Chapter 3: Transport Layerhome.cse.ust.hk/.../notes/chapter3_spr05_v4.pdf · Comp 361, Spring 2005 3: Transport Layer 2 Chapter 3 outline 3.1 Transport-layer services 3.2 Multiplexing

3 Transport Layer 1Comp 361 Spring 2005

Chapter 3 Transport Layer last revised 160305

Chapter goalsunderstand principles behind transport layer services

multiplexingdemultiplexingreliable data transferflow controlcongestion control

instantiation and implementation in the Internet

Chapter Overviewtransport layer servicesmultiplexingdemultiplexingconnectionless transport UDPprinciples of reliable data transferconnection-oriented transport TCP

reliable transferflow controlconnection management

principles of congestion controlTCP congestion control

Chapter 3 outline

31 Transport-layer services32 Multiplexing and demultiplexing33 Connectionless transport UDP34 Principles of reliable data transfer

35 Connection-oriented transport TCP

segment structurereliable data transferflow controlconnection management

36 Principles of congestion control37 TCP congestion control

Transport services and protocolsprovide logical communicationbetween app processes running on different hoststransport protocols run in end systems

send side breaks app messages into segments passes to network layerrcv side reassembles segments into messages passes to app layer

more than one transport protocol available to apps

Internet TCP and UDP

applicationtransportnetworkdata linkphysical

networkdata linkphysical

networkdata linkphysicalnetwork

data linkphysical

logical end-end transport

Transport vs network layerHousehold analogy12 kids sending letters

to 12 kidsprocesses = kidsapp messages = letters in envelopeshosts = housestransport protocol = Ann and Billnetwork-layer protocol = postal service

network layer logical communication between hoststransport layer logical communication between processes

relies on enhances network layer services

Transport-layer protocols

Internet transport servicesreliable in-order unicastdelivery (TCP)

congestion flow controlconnection setup

unreliable (ldquobest-effortrdquo) unordered unicast or multicast delivery UDPservices not available

real-timebandwidth guaranteesreliable multicast

data linkphysical

Chapter 3 outline

Multiplexingdemultiplexinggathering data from multiplesockets enveloping data with header (later used for demultiplexing)

Multiplexing at send host

delivering received segmentsto correct socket

Demultiplexing at rcv host

= socket = process

application

transport

network

physical

P1 application

transport

network

physical

application

transport

network

physical

P2P3 P4P1

host 1 host 2 host 3

Multiplexingdemultiplexingsegment - unit of data

exchanged between transport layer entities

aka TPDU transport protocol data unit

Demultiplexing delivering received segments to correct app layer processes

receiver

applicationtransportnetwork

M P2applicationtransportnetwork

HtHn segment

segment Mapplicationtransportnetwork

M MP3 P4

segmentheader

application-layerdata

How demultiplexing workshost receives IP datagrams

each datagram has source IP address destination IP addresseach datagram carries 1 transport-layer segmenteach segment has source destination port number (recall well-known port numbers for specific applications)

host uses IP addresses amp port numbers to direct segment to appropriate socket

source port dest port

32 bits

applicationdata

(message)

other header fields

TCPUDP segment format

Connectionless demultiplexingWhen host receives UDP segment

checks destination port number in segmentdirects UDP segment to socket with that port number

IP datagrams with different source IP addresses andor source port numbers directed to same socket

Create sockets with port numbers

DatagramSocket mySocket1 = new DatagramSocket(99111)

UDP socket identified by two-tuple

(dest IP address dest port number)

Connectionless demux (cont)DatagramSocket serverSocket = new DatagramSocket(6428)

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428

SP provides ldquoreturn addressrdquo

Connection-oriented demux

TCP socket identified by 4-tuple

source IP addresssource port numberdest IP addressdest port number

recv host uses all four values to direct segment to appropriate socket

Server host may support many simultaneous TCP sockets

each socket identified by its own 4-tuple

Web servers have different sockets for each connecting client

non-persistent HTTP will have different socket for each request

Connection-oriented demux(cont)

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 80DP 9157

SP 9157DP 80

SP 80DP 5775

SP 5775DP 80

Connection-oriented demux Threaded Web Server

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

UDP User Datagram Protocol [RFC 768]

ldquono frillsrdquo ldquobare bonesrdquoInternet transport protocolldquobest effortrdquo service UDP segments may be

lostdelivered out of order to app

connectionlessno handshaking between UDP sender receivereach UDP segment handled independently of others

Why is there a UDPno connection establishment (which can add delay)simple no connection state at sender receiversmall segment header (8 Bytes)no congestion control UDP can blast away as fast as desired

UDP moreoften used for streaming multimedia apps

loss tolerantrate sensitive

other UDP uses (why)

DNS small delaySNMP stressful cond

reliable transfer over UDP add reliability at application layer

application-specific error recover

32 bits

Applicationdata

(message)

length checksumLength in

bytes of UDPsegmentincluding

header

UDP segment format

UDP checksumGoal detect ldquoerrorsrdquo (egflipped bits) in transmitted

segment

Receivercompute checksum of received segmentcheck if computed checksum equals checksum field value

NO - error detectedYES - no error detected But maybe errors nonetheless More later

Receiver may choose to discard segment or send a warning to app in case error

Sendertreat segment contents as sequence of 16-bit integerschecksum addition (1rsquo s complement sum) of segment contentssender puts checksum value into UDP checksum field

Chapter 3 outline

Principles of Reliable data transferimportant in app transport link layerstop-10 list of important networking topics

characteristics of unreliable channel will determine complexity of reliable data transfer protocol (rdt)

Reliable data transfer getting started

sendside

receiveside

rdt_send() called from above (eg by app) Passed data to

deliver to receiver upper layer

udt_send() called by rdtto transfer packet over

unreliable channel to receiver

rdt_rcv() called when packet arrives on rcv-side of channel

deliver_data() called by rdt to deliver data to upper

Reliable data transfer getting startedWersquoll

incrementally develop sender receiver sides of reliable data transfer protocol (rdt)consider only unidirectional data transfer

but control info will flow on both directionsuse finite state machines (FSM) to specify sender receiver

state1

state2

event causing state transitionactions taken on state transition

state when in this ldquostaterdquo next state

uniquely determined by next event

eventactions

Incremental Improvements

rdt10 assumes every packet sent arrives and no errors introduced in transmission

rdt20 assumes every packet sent arrives but some errors (bit flips) can occur within a packet Introduces concept of ACK and NAK

rdt21 deals with corrupted ACKSNAKS

rdt22 like rdt21 but does not need NAKs

Rdt30 Allows packets to be lost

Rdt10 reliable transfer over a reliable channel

underlying channel perfectly reliableno bit errorsno loss of packets

separate FSMs for sender receiversender sends data into underlying channelreceiver read data from underlying channel

Wait for call from above packet = make_pkt(data)

udt_send(packet)

rdt_send(data)extract (packetdata)deliver_data(data)

Wait for call from

rdt_rcv(packet)

sender receiver

Rdt20 channel with bit errors

underlying channel may flip bits in packetrecall UDP checksum to detect bit errors

the question how to recover from errorsacknowledgements (ACKs) receiver explicitly tells sender that pkt received OKnegative acknowledgements (NAKs) receiver explicitly tells sender that pkt had errorssender retransmits pkt on receipt of NAKhuman scenarios using ACKs NAKs

new mechanisms in rdt20 (beyond rdt10)error detectionreceiver feedback control msgs (ACKNAK) rcvr-gtsender

rdt20 FSM specification

Wait for call from above

snkpkt = make_pkt(data checksum)udt_send(sndpkt)

extract(rcvpktdata)deliver_data(data)udt_send(ACK)

rdt_rcv(rcvpkt) ampamp notcorrupt(rcvpkt)

rdt_rcv(rcvpkt) ampamp isACK(rcvpkt)

udt_send(sndpkt)

rdt_rcv(rcvpkt) ampampisNAK(rcvpkt)

udt_send(NAK)

rdt_rcv(rcvpkt) ampamp corrupt(rcvpkt)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

rdt20 operation with no errors

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

rdt20 error scenario

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

rdt20 has a fatal flawWhat happens if ACKNAK

corruptedsender doesnrsquot know what happened at receivercanrsquot just retransmit possible duplicate But receiver waiting

What to dosender ACKsNAKs receiverrsquos ACKNAK What if sender ACKNAK corruptedretransmit but this might cause retransmission of correctly received pktReceiver wonrsquot know about duplication

Handling duplicates sender adds sequence number(01) to each pktsender retransmits current pkt if ACKNAK garbledreceiver discards (doesnrsquot deliver up) duplicate pktDuplicate packet is one with same sequence as previous packet

Sender sends one packet then waits for receiver response

stop and wait

Sender whenever sender receives control message it sends a packet to receiver

A valid ACK Sends next packet (if exists) with new sequence A NAK or corrupt response resends old packet

Receiver sends ACKNAK to senderIf received packet is corrupt send NAKIf received packet is valid and has different sequence as prevpacket send ACK and deliver new data upIf received packet is valid and has same sequence as prevpacket ie is a retransmission of duplicate send ACK

Note ACKNAK do not contain sequence

rdt21 sender handles garbled ACKNAKs

Wait for call 0 from

sndpkt = make_pkt(0 data checksum)udt_send(sndpkt)

rdt_send(data)

Wait for ACK or NAK 0 udt_send(sndpkt)

rdt_rcv(rcvpkt) ampamp ( corrupt(rcvpkt) ||isNAK(rcvpkt) )

rdt_rcv(rcvpkt) ampamp notcorrupt(rcvpkt) ampamp isACK(rcvpkt)

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

Wait for ACK or NAK 1

rdt21 receiver handles garbled ACKNAKsrdt_rcv(rcvpkt) ampamp notcorrupt(rcvpkt)

ampamp has_seq0(rcvpkt)

Wait for 0 from below

sndpkt = make_pkt(NAK chksum)udt_send(sndpkt)

rdt_rcv(rcvpkt) ampamp not corrupt(rcvpkt) ampamphas_seq0(rcvpkt)

rdt_rcv(rcvpkt) ampamp notcorrupt(rcvpkt) ampamp has_seq1(rcvpkt)

extract(rcvpktdata)deliver_data(data)sndpkt = make_pkt(ACK chksum)udt_send(sndpkt)

rdt_rcv(rcvpkt) ampamp (corrupt(rcvpkt)

sndpkt = make_pkt(ACK chksum)udt_send(sndpkt)

rdt21 discussion

Senderseq added to pkttwo seq rsquos (01) will suffice Whymust check if received ACKNAK corrupted twice as many states

state must ldquorememberrdquowhether ldquocurrentrdquo pkt has 0 or 1 seq

Receivermust check if received packet is duplicate

state indicates whether 0 or 1 is expected pkt seq

note receiver can notknow if its last ACKNAK received OK at sender

rdt22 a NAK-free protocol

same functionality as rdt21 using ACKs onlyinstead of NAK receiver sends ACK for last pkt received OK

receiver must explicitly include seq of pkt being ACKed(in 21 seq s included in data packets but not in ACKsNAKs)

duplicate ACK at sender results in same action as NAK retransmit current pkt

rdt22 sender receiver fragments

rdt_send(data)

udt_send(sndpkt)

rdt_rcv(rcvpkt) ampamp ( corrupt(rcvpkt) ||

isACK(rcvpkt1) )

rdt_rcv(rcvpkt) ampamp notcorrupt(rcvpkt) ampamp isACK(rcvpkt0)

Wait for ACK

0sender FSM

fragment

extract(rcvpktdata)deliver_data(data)sndpkt = make_pkt(ACK1 chksum)udt_send(sndpkt)

rdt_rcv(rcvpkt) ampamp (corrupt(rcvpkt) ||

has_seq1(rcvpkt))

udt_send(sndpkt)receiver FSM

fragment

rdt30 channels with errors and loss

New assumptionunderlying channel can also lose packets (data or ACKs)

checksum seq ACKs retransmissions will be of help but not enough

Q how to deal with losssender waits until certain data or ACK lost then retransmitsyuck drawbacks

Approach sender waits ldquoreasonablerdquo amount of time for ACK retransmits if no ACK received in this time(Retransmissions onlytriggered by timeouts)if pkt (or ACK) just delayed (not lost)

retransmission will be duplicate but use of seq rsquos already handles thisreceiver must specify seq of pkt being ACKed

requires countdown timer

rdt30 sendersndpkt = make_pkt(0 data checksum)udt_send(sndpkt)start_timer

rdt_send(data)

Wait for

rdt_rcv(rcvpkt) ampamp ( corrupt(rcvpkt) ||isACK(rcvpkt1) )

sndpkt = make_pkt(1 data checksum)udt_send(sndpkt)start_timer

rdt_send(data)

stop_timerstop_timer

udt_send(sndpkt)start_timer

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

Performance of rdt30

rdt30 works but performance stinksexample 1 Gbps link 15 ms e-e prop delay 1KB packet

L (packet length in bits)R (transmission rate bps)

8kbpkt109 bsec

Ttransmit = = = 8 microsec

U sender =

00830008

= 000027 L R RTT + L R

U sender utilization ndash fraction of time sender busy sending1KB pkt every 30 msec -gt 33kBsec thruput over 1 Gbps linknetwork protocol limits use of physical resources

rdt30 stop-and-wait operation

first packet bit transmitted t = 0

sender receiver

last packet bit transmitted t = L R

first packet bit arriveslast packet bit arrives send ACK

ACK arrives send next packet t = RTT + L R

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocolsPipelining sender allows multiple ldquoin-flightrdquo yet-to-be-acknowledged pkts

range of sequence numbers must be increasedbuffering at sender andor receiver

Pipelined protocols

Advantage much better bandwidth utilization than stop-and-wait

Disadvantage More complicated to deal with reliability issues eg corrupted lost out of order data

Two generic approaches to solving thisbull go-Back-N protocolsbull selective repeat protocols

Note TCP is not exactly either

Pipelining increased utilization

sender receiver

last bit transmitted t = L R

last bit of 2nd packet arrives send ACKlast bit of 3rd packet arrives send ACK

U sender =

02430008

= 00008 3 L R RTT + L R

Increase utilizationby a factor of 3

Go-Back-NSender

k-bit seq in pkt headerldquowindowrdquo of up to N consecutive unackrsquoed pkts allowed

ACK(n) ACKs all pkts up to including seq n - ldquocumulative ACKrdquomay receive duplicate ACKs (see receiver)

Only one timer for oldest unacknowledged pkttimeout(n) retransmit pkt n and all higher seq pkts in windowCalled a sliding-window protocol

GBN Sender

rdt_Send() called checks to see if window is full No send out packetYes return data to application level

Receipt of ACK(n) cumulative acknowledgement that all packets up to and including n have been received Updates window accordingly and restarts timer

Timeout resends ALL packets that have been sent but not yet acknowledged

This is only event that triggers resend

GBN sender extended FSMrdt_send(data)

Wait start_timerudt_send(sndpkt[base])udt_send(sndpkt[base+1])hellipudt_send(sndpkt[nextseqnum-1])

timeout

if (nextseqnum lt base+N) sndpkt[nextseqnum] = make_pkt(nextseqnumdatachksum)udt_send(sndpkt[nextseqnum])if (base == nextseqnum)

start_timernextseqnum++

elserefuse_data(data)

base = getacknum(rcvpkt)+1If (base == nextseqnum)

stop_timerelse

start_timer

base=1nextseqnum=1

GBN receiver extended FSM

udt_send(sndpkt)default

rdt_rcv(rcvpkt)ampamp notcurrupt(rcvpkt)ampamp hasseqnum(rcvpktexpectedseqnum)

extract(rcvpktdata)deliver_data(data)sndpkt = make_pkt(expectedseqnumACKchksum)udt_send(sndpkt)expectedseqnum++

expectedseqnum=1sndpkt =

make_pkt(0ACKchksum)

If expected packet receivedSend ACK and deliver packet upstairs

If out-of-order packet received discard (donrsquot buffer) -gt no receiver bufferingRe-ACK pkt with highest in-order seq may generate duplicate ACKs

More on receiver

The receiver always sends ACK for last correctly received packet with highest in-order seq Receiver only sends ACKS (no NAKs)Can generate duplicate ACKsneed only remember expectedseqnum

GBN inaction

GBN is easy to code but might have performance problems

In particular if many packets are in pipeline at one time (bandwidth-delay product large) then one error can force retransmission of huge amounts of data

Selective Repeat protocol allows receiver to buffer data and only forces retransmission of required packets

Selective Repeat

receiver individually acknowledges all correctly received pkts

buffers pkts as needed for eventual in-order delivery to upper layer

sender only resends pkts for which ACK not received

sender timer for each unACKed pktCompare to GBN which only had timer for base packet

sender windowN consecutive seq rsquosagain limits seq s of sent unACKed pktsImportant Window size lt seq range

Selective repeat sender receiver windows

Selective repeat

pkt n in [rcvbase rcvbase+N-1]

send ACK(n)out-of-order bufferin-order deliver (also deliver buffered in-order pkts) advance window to next not-yet-received pkt

pkt n in [rcvbase-Nrcvbase-1]

ACK(n) (note this is a reACK)

otherwiseignore

receiverdata from above

if next available seq in window send pkt

timeout(n)resend pkt n restart timer

ACK(n) in [sendbasesendbase+N]

mark pkt n as receivedif n smallest unACKed pkt advance window base to next unACKed seq

sender

Selective repeat in action

Selective repeatdilemma

Example seq rsquos 0 1 2 3window size=3

receiver sees no difference in two scenariosincorrectly passes duplicate data as new in (a)

Q what is relationship between seq size and window size

Chapter 3 outline

TCP Overview RFCs 793 1122 1323 2018 2581

full duplex databi-directional data flow in same connectionMSS maximum segment size

connection-orientedhandshaking (exchange of control msgs) initrsquossender receiver state before data exchange

flow controlledsender will not overwhelm receiver

point-to-pointone sender one receiver

reliable in-order byte steam

no ldquomessage boundariesrdquopipelined

TCP congestion and flow control set window size

send amp receive buffers

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

applicationwrites data

applicationreads data

More TCP DetailsMaximum Segment Size (MSS)

Depends upon implementation (can often be set)The Max amount of application-layer data in segment

Application Data + TCP Header = TCP Segment

Three way HandshakeClient sends special TCP segment to server requesting connection No payload (Application data) in this segmentServer responds with second special TCP segment

(again no payload)Client responds with third special segment

This can contain payload

Even More TCP Details

A TCP connection between client and server creates in both client and server

(i) buffers(ii) variables and

(iii) a socket connection to process

TCP only exists in the two end machinesNo buffers and variables allocated to the connection in

any of the network elements between the host and server

TCP segment structure

32 bits

applicationdata

(variable length)

sequence numberacknowledgement number

Receive windowUrg data pnterchecksum

FSRPAUheadlen

notused

Options (variable length)

URG urgent data (generally not used)

ACK ACK valid

PSH push data now(generally not used)

RST SYN FINconnection estab(setup teardown

commands)

bytes rcvr willingto accept

Internetchecksum

(as in UDP)

countingby bytes of data(not segments)

TCP seq rsquos and ACKsSeq rsquos

byte stream ldquonumberrdquo of first byte in segmentrsquos data

ACKsseq of next byte expected from other sidecumulative ACK

Q how receiver handles out-of-order segments

A TCP spec doesnrsquot say - up to implementer

Host BHost A

Seq=42 ACK=79 data = lsquoCrsquo

Seq=43 ACK=80

Usertypes

lsquoCrsquohost ACKsreceipt oflsquoCrsquo echoes

back lsquoCrsquo

host ACKsreceipt

of echoedlsquoCrsquo

timesimple telnet scenario

TCP Round Trip Time and Timeout

Q how to estimate RTTSampleRTT measured time from segment transmission until ACK receipt

ignore retransmissionsSampleRTT will vary want estimated RTT ldquosmootherrdquo

average several recent measurements not just current SampleRTT

Q how to set TCP timeout valuelonger than RTT

but RTT variestoo short premature timeout

unnecessary retransmissions

too long slow reaction to segment loss

EstimatedRTT = (1- α)EstimatedRTT + αSampleRTT

Exponential weighted moving averageinfluence of past sample decreases exponentially fasttypical value α = 0125

Example RTT estimationRTT gaiacsumassedu to fantasiaeurecomfr

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

SampleRTT Estimated RTT

Setting the timeoutEstimtedRTT plus ldquosafety marginrdquo

large variation in EstimatedRTT -gt larger safety marginfirst estimate of how much SampleRTT deviates from EstimatedRTT

DevRTT = (1-β)DevRTT +β|SampleRTT-EstimatedRTT|

(typically β = 025)

Then set timeout interval

TimeoutInterval = EstimatedRTT + 4DevRTT

Chapter 3 outline

TCP reliable data transfer

TCP creates rdtservice on top of IPrsquos unreliable servicePipelined segmentsCumulative acksTCP uses single retransmission timer

Retransmissions are triggered by

timeout eventsduplicate acks

Initially consider simplified TCP sender

ignore duplicate acksignore flow control congestion control

TCP sender eventsdata rcvd from app

Create segment with seq seq is byte-stream number of first data byte in segmentstart timer if not already running (think of timer as for oldest unacked segment)expiration interval TimeOutInterval

timeoutretransmit segment that caused timeoutrestart timer

Ack rcvdIf acknowledges previously unackedsegments

update what is known to be ackedstart timer if there are outstanding segments

TCP sender(simplified)

NextSeqNum = InitialSeqNumSendBase = InitialSeqNum

loop (forever) switch(event)

event data received from application above create TCP segment with sequence number NextSeqNumif (timer currently not running)

start timerpass segment to IP NextSeqNum = NextSeqNum + length(data)

event timer timeoutretransmit not-yet-acknowledged segment with

smallest sequence numberstart timer

event ACK received with ACK field value of y if (y gt SendBase)

SendBase = yif (there are currently not-yet-acknowledged segments)

start timer

end of loop forever

Commentbull SendBase-1 last cumulatively ackrsquoed byteExamplebull SendBase-1 = 71y= 73 so the rcvrwants 73+ y gt SendBase sothat new data is acked

TCP retransmission scenariosHost A

Seq=100 20 bytes data

ACK=100

timepremature timeout

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

TCP retransmission scenarios (more)Host A

Seq=92 8 bytes data

ACK=100

Cumulative ACK scenario

Host B

ACK=120

SendBase= 120

TCP ACK generation [RFC 1122 RFC 2581]

Event at Receiver

Arrival of in-order segment withexpected seq All data up toexpected seq already ACKed

Arrival of in-order segment withexpected seq One other segment has ACK pending

Arrival of out-of-order segmenthigher-than-expect seq Gap detected

Arrival of segment that partially or completely fills gap

TCP Receiver action

Delayed ACK Wait up to 500msfor next segment If no next segmentsend ACK

Immediately send single cumulative ACK ACKing both in-order segments

Immediately send duplicate ACK indicating seq of next expected byte

Immediate send ACK provided thatsegment starts at lower end of gap

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Selective repeat dilemma

Chapter 3 outline

More TCP Details

TCP seq rsquos and ACKs

Example RTT estimation

Chapter 3 outline

TCP sender events

TCP retransmission scenarios

TCP retransmission scenarios (more)

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP Congestion Control

TCP AIMD

TCP Slow Start

The Big Picture

TCP sender congestion control

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

TCP Latency Modeling

Fixed Congestion Window (W)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

data linkphysical

Chapter 3 outline

= socket = process

application

transport

network

physical

P1 application

transport

network

physical

application

transport

network

physical

P2P3 P4P1

receiver

HtHn segment

M MP3 P4

segmentheader

32 bits

applicationdata

(message)

other header fields

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 80DP 9157

SP 9157DP 80

SP 80DP 5775

SP 5775DP 80

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

data linkphysical

Chapter 3 outline

= socket = process

application

transport

network

physical

P1 application

transport

network

physical

application

transport

network

physical

P2P3 P4P1

receiver

HtHn segment

M MP3 P4

segmentheader

32 bits

applicationdata

(message)

other header fields

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 80DP 9157

SP 9157DP 80

SP 80DP 5775

SP 5775DP 80

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

data linkphysical

Chapter 3 outline

= socket = process

application

transport

network

physical

P1 application

transport

network

physical

application

transport

network

physical

P2P3 P4P1

receiver

HtHn segment

M MP3 P4

segmentheader

32 bits

applicationdata

(message)

other header fields

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 80DP 9157

SP 9157DP 80

SP 80DP 5775

SP 5775DP 80

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

data linkphysical

Chapter 3 outline

= socket = process

application

transport

network

physical

P1 application

transport

network

physical

application

transport

network

physical

P2P3 P4P1

receiver

HtHn segment

M MP3 P4

segmentheader

32 bits

applicationdata

(message)

other header fields

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 80DP 9157

SP 9157DP 80

SP 80DP 5775

SP 5775DP 80

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

= socket = process

application

transport

network

physical

P1 application

transport

network

physical

application

transport

network

physical

P2P3 P4P1

receiver

HtHn segment

M MP3 P4

segmentheader

32 bits

applicationdata

(message)

other header fields

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 80DP 9157

SP 9157DP 80

SP 80DP 5775

SP 5775DP 80

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

= socket = process

application

transport

network

physical

P1 application

transport

network

physical

application

transport

network

physical

P2P3 P4P1

receiver

HtHn segment

M MP3 P4

segmentheader

32 bits

applicationdata

(message)

other header fields

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 80DP 9157

SP 9157DP 80

SP 80DP 5775

SP 5775DP 80

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

receiver

HtHn segment

M MP3 P4

segmentheader

32 bits

applicationdata

(message)

other header fields

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 80DP 9157

SP 9157DP 80

SP 80DP 5775

SP 5775DP 80

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

32 bits

applicationdata

(message)

other header fields

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 80DP 9157

SP 9157DP 80

SP 80DP 5775

SP 5775DP 80

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 80DP 9157

SP 9157DP 80

SP 80DP 5775

SP 5775DP 80

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 6428DP 9157

SP 9157DP 6428

SP 6428DP 5775

SP 5775DP 6428

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 80DP 9157

SP 9157DP 80

SP 80DP 5775

SP 5775DP 80

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 80DP 9157

SP 9157DP 80

SP 80DP 5775

SP 5775DP 80

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

ClientIPB

clientIP A

P1P1P3

serverIP C

SP 80DP 9157

SP 9157DP 80

SP 80DP 5775

SP 5775DP 80

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

ClientIPB

clientIP A

serverIP C

SP 9157DP 80

D-IPCS-IP AD-IPC

S-IP B

SP 5775DP 80

D-IPCS-IP B

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

32 bits

Applicationdata

(message)

header

UDP segment format

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

segment

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

sendside

receiveside

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

state1

state2

eventactions

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

udt_send(packet)

Wait for call from

rdt_rcv(packet)

sender receiver

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

rdt_send(data)

receiver

Wait for call from

sender

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

udt_send(sndpkt)

udt_send(NAK)

Wait for ACK or

Wait for call from

rdt_send(data)

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

stop and wait

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

rdt_send(data)

udt_send(sndpkt)

Wait forcall 1 from

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

rdt21 discussion

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

rdt_send(data)

udt_send(sndpkt)

isACK(rcvpkt1) )

Wait for ACK

0sender FSM

fragment

has_seq1(rcvpkt))

fragment

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

rdt_send(data)

Wait for

rdt_send(data)

timeout

rdt_rcv(rcvpkt)

Wait for call 0from

Wait for

Λrdt_rcv(rcvpkt)

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

rdt30 in action

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

8kbpkt109 bsec

U sender =

00830008

= 000027 L R RTT + L R

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

sender receiver

U sender =

008 30008

= 000027 L R RTT + L R

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Pipelined protocols

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

sender receiver

U sender =

02430008

= 00008 3 L R RTT + L R

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Go-Back-NSender

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

GBN Sender

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

timeout

stop_timerelse

start_timer

base=1nextseqnum=1

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

More on receiver

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

GBN inaction

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Selective Repeat

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Selective repeat

otherwiseignore

sender

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

socketdoor

TCPsend buffer

TCPreceive buffer

socketdoor

segment

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Host BHost A

Seq=43 ACK=80

Usertypes

back lsquoCrsquo

host ACKsreceipt

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

1 8 15 22 29 36 43 50 57 64 71 78 85 92 99 106

time (seconnds)

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

start timer

end of loop forever

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

ACK=100

Host B

Seq=92 8 bytes data

ACK=120

Seq=92 8 bytes data

ACK=120

Host A

Seq=92 8 bytes data

ACK=100

lost ACK scenario

Host B

Seq=92 8 bytes data

ACK=100

SendBase= 120

Sendbase= 100

utSendBase

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Seq=92 8 bytes data

ACK=100

Host B

ACK=120

SendBase= 120

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Event at Receiver

TCP Receiver action

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Fast Retransmit

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

start timer

fast retransmit

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

TCP is a hybrid

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

TCP Flow Control

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

32 bits

applicationdata

(variable length)

FSRPAUheadlen

notused

ACK ACK valid

commands)

Internetchecksum

(as in UDP)

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

LastByteRead]

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Technical Issue

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Note on UDP

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

server

ack=client_isn+1)

ack=server_isn+1

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

client

server

closed

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

client

server

closing

closed

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

A few special cases

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

a top-10 problem

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

λin λout=

λin λoutgtλ

inλout

(c)(a) (b)

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3 outline

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Congwin

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

8 Kbytes

16 Kbytes

24 Kbytes

congestionwindow

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

TCP Slow Start

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Host A

one segment

Host B

two segments

four segments

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

The Big Picture

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Slow Start (SS)

Enter slow start

Duplicate ACK

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

TCP throughput

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

TCP Futures

LRTTMSSsdot221

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

TCP connection 1

bottleneckrouter

capacity R

TCP connection 2

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

modeling slow start

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

latency = 2RTT + OR

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

RSRTTP

⎤⎢⎣⎡ +++=

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

RSRTTPRTT

idleTimeRTTRO

)12(][2

2delay

minusminus+++=

minus+++=

RS k =⎥⎦

⎤⎢⎣⎡ minus+

+minus

requestobject

first window= SR

second window= 2SR

third window= 4SR

fourth window= 8SR

delivered

time atclient

time atserver

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

⎥⎥⎤

⎢⎢⎡ +=

geminus=

ge+++=

ge+++=minus

)1(log

)1(logmin

222min222min

SOkOSSSkK

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

101214161820

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

28Kbps

100Kbps

1 Mbps 10Mbps

non-persistent

persistent

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

UDPTCP

Chapter 3 outline

UDP more

UDP checksum

Chapter 3 outline

rdt21 discussion

rdt30 sender

rdt30 in action

Pipelined protocols

Go-Back-N

GBN Sender

More on receiver

GBN inaction

Selective Repeat

Selective repeat

Chapter 3 outline

More TCP Details

Chapter 3 outline

TCP sender events

Fast Retransmit

Chapter 3 outline

TCP Flow Control

Technical Issue

Chapter 3 outline

A few special cases

Chapter 3 outline

TCP AIMD

TCP Slow Start

The Big Picture

TCP throughput

TCP Futures

TCP Fairness

Why is TCP fair

Fairness (more)

HTTP Modeling

Chapter 3 Summary

Chapter 3: Transport Layerhome.cse.ust.hk/.../notes/chapter3_spr05_v4.pdf · Comp 361, Spring 2005 3: Transport Layer 2 Chapter 3 outline 3.1 Transport-layer services 3.2 Multiplexing

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