Protocols with QoS Support

Protocols Protocols with QoS Supportwith QoS Support

29/9 - 2003

INF5070 – Media Storage and Distribution Systems:

2003 Carsten Griwodz & Pål Halvorsen

INF5070 – media storage and distribution systems

Overview Quality-of-Service

Resource reservation

Protocols: IPv4 IPv6 Tenet ATM IntServ RSVP DiffServ MPLS …

Quality-of-Service



Quality–of–Service (QoS) – I

Many definitions, e.g.:

“QoS represents the set of those quantitative and qualitative characteristics of a distributed multimedia system that are necessary to achieve the required functionality of an application” Vogel et. al.: “Distributed Multimedia and QoS: A Survey”, IEEE Multimedia 1995



Quality–of–Service (QoS) – II Different semantics or classes of QoS:

determines reliability of offered service utilization of resources

max

reserved A

reserved B

time

reso

urc

es

unusedavailable resources

reserved C



Quality–of–Service (QoS) – IIIBest effort QoS:

system tries its best to give a good performance no QoS calculation (could be called no effort QoS)

simple – do nothing

QoS may be violated unreliable service

Deterministic guaranteed QoS: hard bounds QoS calculation based on upper bounds (worst case) premium better name!!??

QoS is satisfied even in the worst case high reliability

over-reservation of resources poor utilization and unnecessary service rejects

QoS values may be less than calculated hard upper bound



Quality–of–Service (QoS) – IV Statistical guaranteed QoS:

QoS values are statistical expressions (served with some probability) QoS calculation based on average (or some other statistic or stochastic value)

resource capabilities can be statistically multiplexed more granted requests

QoS may be temporarily violated service not always 100 % reliable

Predictive QoS: weak bounds QoS calculation based previous behavior of imposed workload

resource capabilities can be statistically multiplexed more granted requests possibly more exact workload description (if past and actual behavior

matches)

QoS may be temporarily violated service not 100 % reliable QoS values may be less than calculated hard upper bound

Resource Reservation



Resource Reservation – I Reservations is fundamental for reliable enforcement of

QoS guarantees per-resource data structure (information about all usage) QoS calculations and resource scheduling may be done based

on the resource usage pattern

reservation protocols negotiate desired QoS by transferring information about resource

requirements and resource usage between the end-systems and the intermediate systems participating in the data transfer

reservation operationo calculate necessary amount of resources based on the QoS

specificationso reserve resources according to the calculation (or reject request)

resource scheduling enforce resource usage with respect to resource administration

decisions



Resource Management Phasesuser’s QoS

requirementstim

e Phase 1:

Phase 2:

Phase 3:

admission test and calculation of QoS guarantees

rejection or renegotiation

resource reservation QoS guarantees to user

negotiation

data transmission QoS enforcement by proper scheduling

monitoring and adaptation “notification”

renegotiation

enforcement

specification

confirmation

renegotiation

stream termination resource deallocation termination

not necessary an own phase, some protocols start sending at once



Reservation Directions Sender oriented:

sender (initiates reservation) must know target addresses

(participants) in-scalable good security

1. reserve

2. reserve

3. reserve

receiver

sender

data flow



Reservation Directions Receiver oriented:

receiver (initiates reservation) needs advertisement before

reservation must know “flow” addresses

sender need not to know receivers more scalable in-secure 1. reserve

2. reserve

3. reserve

receiver

sender

data flow



Reservation Directions Combination:

start sender oriented reservation

additional receivers join at routers(receiver based)

receiver

sender

data flow

reserve from nearest router

1. reserve

2. reserve

3. reserve

Routing



Routing

physicallink

network

applicationtransport



Routing

216.239.51.101

129.42.16.99

80.91.34.111

129.240.148.31

129.240.148.31

66.77.74.20

209.73.164.90

192.67.198.54

209.189.226.17

193.99.144.71

81.93.162.20



Routing

216.239.51.101

129.42.16.99 80.91.34.111

129.240.148.31

129.240.148.31

66.77.74.20

209.73.164.90192.67.198.54

209.189.226.17

193.99.144.71

81.93.162.20

… - …216.239.51.101 - IF1209.189.226.17 - IF280.91.34.111 - IF3209.189.226.* - 209.189.226.17129.240.* - 80.91.34.11181.93.* - 80.91.34.111192.67.* - 80.91.34.111209.73.* - 80.91.34.111129.240.148.* - 80.91.34.111193.99.* - 80.91.34.11166.77.74.20 - 80.91.34.111… - …



Routing

216.239.51.101

129.42.16.99 80.91.34.111

129.240.148.31

129.240.148.31

66.77.74.20

209.73.164.90192.67.198.54

209.189.226.17

193.99.144.71

81.93.162.20

Protocols



Internet Protocol version 4 (IPv4) – I

IP is THETHE network layer protocol within the Internet IPv4

defined by RFC 791 (1981) – STD 5 unreliable datagram service (neither flow nor error

control) no fixed routes

flexibility for path selection reordering problems not suitable for time critical continuous media data but, source routing is optional

o loose – specify some router IP addresses to be passed in order o strict – specify all routers to be passed in order

maximum 64 KB datagrams including headers segmentation for smaller subnets (e.g., 1500 B for standard

Ethernet) reassembly in end-system’s IP-layer



Internet Protocol version 4 (IPv4) – II

0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| IHL |Type of Service| Total Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identification |Flags| Fragment Offset | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Time to Live | Protocol | Header Checksum | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Source Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Destination Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Options | Padding | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

indicates the format of the internet header, i.e., version 4

length of the internet header in 32 bit words, and thus points to the beginning of the data (minimum value of 5)

indication of the abstract parameters of thequality of service desired – somehow treathigh precedence traffic as more important – tradeoff between low-delay, high-reliability, andhigh-throughput – NOT used, bits now reused

datagram length(octets) includingheader and data - allows the lengthof 65,535 octets

identifying value to aid assembly of fragments

fragments allowed flag allowed and last fragment flag

indicate where this fragment belongs in datagram

checksum on the header only – TCP, UDP over payload. Since some header fields change(TTL), this is recomputed and verified at each point

indicates used transport layer protocol

disable a packet to circulate forever,decrease value by at least 1 in each node – discarded if 0

32-bit address fields. May be configured differently from small to large networks

options may extend the header. If the options do not end on a 32-bit boundary, the remaining fields are padded in the padding field (0’s)



128-bit address fields

disable a packet to circulate forever, decrease value by at least 1 in each node – discarded if 0

length of payload in bytes.If zero, indicates that the payload length is carried in a Jumbo Payload option.

Identifies the type of headerimmediately following theheader – e.g., TCP, UDP, butalso EXTENSION headers

version of protocol, i.e., version 6

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| Prio. | Flow Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Payload Length | Next Header | Hop Limit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Source Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Destination Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Internet Protocol version 6 (IPv6) – I

IPv6 defined by RFC 1883 (1995), but

revised by RFC 2460 (1998) simplified header:

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Version| Traffic Class | Flow Label | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Payload Length | Next Header | Hop Limit | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Source Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | | + Destination Address + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

the 4-bit priority field hasbeen replaced by an 8-bit traffic class field. To identify and distinguish between different classes or priorities

label packets which requests special handling by the IPv6 routers, such as non-default quality of service or real-time



Internet Protocol version 6 (IPv6) – II

IPv6 enlarged address space (2128 = 3.4 x 1038 addresses)

simplified headers reduce packet processing time

“jumbograms” allows packets larger than 64 KB (using a extension header)

strict routing (source can fix route to destination using a routing extension header)

inclusion of security concepts and mobile end-systems

may specify only a geographical range for a multicast session

some support for QoS concepts – each packet header includes ...

... a 8-bit traffic class field – defined by DiffServ ... a 20-bit flow label



Internet Protocol version 6 (IPv6) – IV

Flow labels “a flow is a sequence of packets sent from the source to the

destination for which the source desires special handling by the routers”

each flow must have same flow label, priority and addresses flow = pseudo-connection

before start or during transmissiono set up flow between source and destinationo route is cached – table entries in a router allows fast packet switchingo routers can reserve resources

during data transmissiono routers can identify flows by a unique “flow label/address” combinationo routers can treat packets according to the flow type

still experimental use

BUT;BUT; IPv6 itself does not define mechanisms for IPv6 itself does not define mechanisms for QoS treatment – must use additional protocolsQoS treatment – must use additional protocols



IP Multicast Limiting IP multicast geographically

IPv4 – interpretation of TTL header field is used(non-standardized MBONE use)

IPv6 – multicast address contains a 4-bit scope field possible geographical limits

machine LAN organization country (v4 only) continent (v4 only) global – no limit



Tenet – I

Late 80’s/early 90’s, Tenet group at Berkeley

Aims for network support for real-time continuous media applications

Real-time communication model

Real-time channels: end-to-end connection with performance guarantees and traffic restrictions associated with a set of nodes and links (a route) through which

real-time packets pass resource reservation in route nodes admission control



Tenet – II Traffic specification:

expressing peak and average load on the network indication of the burstiness of the load parameters:

minimum packet inter-arrival time average packet inter-arrival time averaging interval maximum packet size

Supported QoS parameters (by which users describe their requirements): upper bound on end-to-end message delay delay violation probability bound buffer overflow probability bound delay jitter bound (optional) a throughput guarantee is obtained from the traffic specification



Tenet – III Protocol suite:

Real-time Channel Administration Protocol (RCAP) performs channel setup uses the traffic description and performance requirement

to find a route and maps the global requirement onto local resources

performs admission control and reservations on the way

Real-time Message Transport Protocol (RMTP) intended for message based real-time transport

Continuous Media Transport Protocol (CMTP) offers a stream based interface and a time-driven

mechanism for audio and video – may demand data from application

Real-time Internet Protocol (RTIP) replaces IP schedules packets according to resource reservations made by RCAP

applicationapplication

physical layerphysical layer

data link layerdata link layer

real-timeinternet protocol

real-timeinternet protocol

real-time messagetransport protocol

real-time messagetransport protocol

continuous mediatransport protocol

continuous mediatransport protocol

real-time channeladministration protocol

real-time channeladministration protocol



Defined by ATM Forum and International Telecommunication Union (ITU)

Targeted for all kinds of traffic within the same network (i.e., both continuous and discrete data types)

A full suite of protocols: physical layer – deals with voltages, bit timing

and framing on the physical medium ATM layer – defines the ATM cell structure adaptation layer – analogous to the Internet

transport layer supporting different services

Today: “IP-over-ATM” IP rules – TCP/IP is used in every end-system

ATM used as link-layer technology however, ATM may forward data quickly ATM may be used in the Internet backbone running under IP uses AAL5 to transport IP datagrams over the ATM network

Asynchronous Transfer Mode (ATM) – I

ATM physical layerATM physical layer

ATM layerATM layer

ATM adaptation layer (AAL)ATM adaptation layer (AAL)



Asynchronous Transfer Mode (ATM) – II Service classes

constant bit rate (CBR)(real-time, guaranteed constant rate)

variable bit rate (VBR) – real-time and non-real-time available bit rate (ABR)

(slightly better than best effort – a minimum guarantee, only class with congestion control)

unspecified bit rate (UBR)(best effort, no guarantees)

Virtual channels (VC) the ATM network sets up a VC between sender and receiver a path consisting of a sequence of links each link has a virtual circuit identifier (VCI) used for routing

(included in the cell header) ATM backbones usually use permanent VCs, i.e., saving VC

setup and teardown Virtual paths



Asynchronous Transfer Mode (ATM) – III The ATM standard specifies a number of QoS parameters

traffic generation by sender: cell rate (sustainable (SCR) / peak (PCR) / minimum (MCR)) maximum burst size (MBS) cell delay variation tolerance (CDVT)

service provided by network: cell transfer delay (CTD) –

cell transit time from source to destination cell delay variation (CDV) –

variance in transfer delays

cell loss ratio (CLR) – fraction of cells lost or delivered too late

cell error rate (CER) – fraction of cells with bit errors

severly-errored cell block ratio (SECBR) – fraction of an N-cell block with M or more cells damaged

cell misinsertion rate (CMR) – number of cells delivered to wrong destination

cannot benegotiated – part of network QoS offer



Asynchronous Transfer Mode (ATM) – VI

Traffic contracts

the VC acts like a contract between customer and network for a service

consist of a connection traffic descriptor and a set of QoS parameters

which traffic to be offered which service class compliance requirements

the QoS parameters are negotiated during the VC setup (can be specified either explicitly or implicitly)



Asynchronous Transfer Mode (ATM) – V

Different service categories require different parameters

Traffic description

Min lossguarantee

(CLR)

Delay/variance

guarantee (CDV)

Bandwidth guarantee

Feedback control

CBR PCR + + + -rt-VBR PCR, SCR,

MBS + + + -nrt-VBR PCR, SCR,

MBS + - + -ABR PCR, MCR + - + +UBR PCR - - - -



Asynchronous Transfer Mode (ATM) – VI Application areas for ATM service categories (by ATM Forum)

CBR rt-VBR nrt-VBR ABR UBR

critical data 2 1 3 1 n/s

ISDN – video conference 3 ? ? n/s n/s

compressed audio 1 3 2 2 1

video distribution 3 2 1 n/s n/s

interactive multimedia 3 3 2 2 1

3 – good2 – fair1 – not good, not applicable with advantagen/s – not suitable

may be more useful now!!??



Integrated Services (IntServ) – I Framework by IETF to provide individualized

QoS guarantees to individual application sessions

Goals: efficient Internet support for applications which require service

guarantees fulfill demands of multipoint, real-time applications (like video

conferences) do not introduce new data transfer protocols

In the Internet, it is based on IP (v4 or v6) and RSVP (described later)

Two key features reserved resources – the routers need to know what resources are

available (both free and reserved) call setup (admission call) – reserve resources on the whole path from

source to destination



Integrated Services (IntServ) – II Admission call:

traffic characterization and specification one must specify the traffic one will

transmit on the network (Tspec) one must specify the requested QoS

(Rspec – reservation specification)

signaling for setup send the Tspec and Rspec to all routers

per-element admission test each router checks whether the requests

specified in the R/Tspecs can be fulfilled if YES, accept; reject otherwise

1. request: specify traffic (Tspec), guarantee (Rspec)

1

2

32. consider request against available resources

3. accept or reject

receiver

sender



Integrated Services (IntServ) – III IntServ introduce two new services enhancing the

Internet’s traditional best effort:

guaranteed service guaranteed bounds on delay and bandwidth for applications with real-time requirements

controlled-load service “a QoS closely to the QoS the same flow would receive from an

unloaded network element” [RFC 2212], i.e., similar to best-effort in networks with limited load

no quantified guarantees, but packets should arrive with “a very high percentage”

for applications that can adapt to moderate losses, e.g., real-time multimedia applications



Both service classes uses token bucket to police a packet flow: packets need a token to be forwarded

each router has a b-sized bucket with tokens:if bucket is empty, one must wait

new tokens are generated at a rate r and added:if bucket is full (little traffic), the token is deleted

the token generation rate r serves to limit the long term average rate

the bucket size b serves to limit themaximum burst size

Integrated Services (IntServ) – IV

token wait queue

bucket

token generation



Integrated Services (IntServ) – V Usual protocol structure:


data linkdata link

IPIP

UDPUDP RSVPRSVP

RTPRTP



Resource Reservation Protocol (RSVP) - I

Defined by RFC 2205 (1997)

A protocol to signal reservations of resources in the Internet contains protocol elements for control no support for data transfers (reservation signals only) simplex protocol, i.e., makes reservations for unidirectional flows receiver-oriented, i.e., the receiver initiates and maintains resource

reservations maintains a “soft” state – graceful changes to dynamic

memberships and automatic adaptation to route changes (timeouts)

companion protocol to IP – supports both IPv4 and IPv6 transported as raw IP datagram with protocol number 46 filtering provides support for heterogeneous receivers and different

reservation styles



RSVP will generally require raw network I/O sends raw IP datagrams using

protocol 46

operates on top of IP, i.e., takes the place of the transport protocol

does not perform traditional transport layer services – must add a transport protocol (UDP)

Resource Reservation Protocol (RSVP) - II


data linkdata link

IPIP

UDP UDP RSVPRSVP



same multicast group and port

Sessions a data flow with particular destination and transport protocol defined by (destination address, protocol ID)

IP address IP protocol ID

may carry multiple data flows Data flows are distinguished by

source IP address and source port (IPv4) source IP address and flow label (IPv6)

Transmission model:

Resource Reservation Protocol (RSVP) - III



Resource Reservation Protocol (RSVP) - IV

Two fundamental messages: PATH:

sender sends a PATH message downstream following the data path sent using same source and destination addresses includes:

o hop-addresseso sender template (describes data packet format)o sender Tspec (traffic characteristics generated by sender)o sender Adspec (advertisement information)o ...

RESV: receiver sends a RESV message upstream using the path described

in the PATH message sent to previous hop only includes:

o flowspec: reservation requests, desired QoS (e.g., RFC 1363)o filterspec: reservation styleo reverse data paths for the flowo ...

flow descriptor



Creating and maintaining a reservation state: the SOURCE

multicasts data flows sends PATH messages with traffic

characteristics (Tspec) describing flows the RECEIVER

joins multicast group receives the PATH message determines own QoS requirements based the PATH Tspec sends a RESV message with request and filters

the ROUTERS reserve according to incoming flowspecs downstream merge and forward the RESV messages to next node using largest

flowspec

the reservations are maintained using “soft” states the reservation has an associated timer – a timeout removes the

reservation periodically refreshed by PATH and RESV messages

Resource Reservation Protocol (RSVP) - V



Resource Reservation Protocol (RSVP) - VI

3 Mbps

5 Kbps

1 Mbps10 Mbps

1 Mbps

PATH PATH PATH

PATHPATH

PATH

PATH

PATH

PATH

PATH

RESV5 Kbps

reserved 5 Kbps

RESV1 Mbps

reserved 1 Mbps

RESV1 Mbps

rese

rved

1 M

bps

merging

RESV10 Mbps

reserved 10 Mbps

merging

RESV10 Mbps

rese

rved

10

Mbp

s

RESV3 Mbps

rese

rved

3 M

bps

RESV3 Mbps

rese

rved

3 M

bps

RESV1 Mbps

rese

rved

1 M

bps

mergingRESV

3 Mbps

reserved 3 Mbps

merging

RESV10 Mbps

rese

rved

10

Mbp

s



Resource Reservation Protocol (RSVP) - VII

RSVP in hosts and routers:1. RESV with flowspec and filterspec to RSVP daemon2. policy control to check privileges etc.3. admission control using flowspec4. forward RESV message5. control of local modules: classifier and scheduler

applicationprocess

RSVPdaemon

policycontrol

admissioncontrol

routingprocess

RSVPdaemon

policycontrol

admissioncontrol

packetclassifier

packetscheduler

packetclassifier

packetschedulerdata



Resource Reservation Protocol (RSVP) - VIII

Reservation styles a reservation request includes a set of options called

the reservation style

shared vs. distinct reservations concerns treatment of reservations of different senders shared – single reservation for all senders (e.g., video conference

audio) distinct – one reservation per sender (e.g., video conference

video)

explicit vs. wildcard concerns selection of senders explicit – specify senders (e.g., teleteaching) wildcard – automatically select all senders (e.g., video

conference)



Resource Reservation Protocol (RSVP) - IX

distinctreservation

sharedreservation

explicitsender

selection

Fixed:distinct reservation (not shared) for each sender

Shared-explicit:single reservation shared by a specified list of senders

wildcardsender

selectionundefined

Wildcard:single reservation shared by flows form all senders



Resource Reservation Protocol (RSVP) - X

The RSVP standard [RFC 2205] allows to reserve link bandwidth – it does NOT...NOT...:

...define how the network should provide the reserved bandwidth to the data flows – the routers must implement these mechanisms themselves

...specify how to do resource provisioning – which must likely be done using a proper scheduling mechanism

...determine the route – it is not a routing protocol, but relies on others

...determine which data to drop in case of overflow, i.e., the most important data may be lost

...perform an admission test, but it assumes that the routers perform admission control

THUS; RSVP can only be used as a small piece in THUS; RSVP can only be used as a small piece in the the QoS guarantee puzzleQoS guarantee puzzle Kurose, J. F., Ross, K. W.: “Computer Networking: A Top-Down Approach Featuring the Internet”, 2nd edition, Addison Wesley, 2002



Differentiated Services (DiffServ) – I

IntServ and RSVP provide a framework for per-flow QoS, but they … … give complex routers

much information to handle … have scalability problems

set up and maintain per-flow state information periodically PATH and RESV messages overhead

… specify only a predefined set of services new applications may require other flexible services

DiffServ [RFC 2475] tries to be both scalable and flexible



Differentiated Services (DiffServ) – II

ISP favor DiffServ Basic idea

multicast is not necessary

make the core network simple due to many users implement more complex control operations at the edge aggregation of flows –

reservations for a group of flows, not per flow thus, avoid scalability problems on routers with many

flows

do not specify services or service classes instead, provide the functional components on which

services can be built thus, support flexible services



Differentiated Services (DiffServ) – III

Two set of functional elements: edge functions: packet classification and traffic conditioning core function: packet forwarding

At the edge routers, the packets are tagged with a DS-mark (differentiated service mark) uses the type of service field (IPv4) or the traffic class field

(IPv6) different service classes (DS-marks) receive different service subsequent routers treat the packet according to the DS-mark classification:

incoming packet is classified (and steered to the appropriate marker function) using the header fields

the DS-mark is set by marker once marked, forward classifier marker

forward



Differentiated Services (DiffServ) – IV

Note, however, that there is no “rules” for classification – it is up to the network provider

A metric function may be used to limit the packet rate: the traffic profile may define rate and maximum bursts if packets arrive too fast, the metric function assigns another marker

function telling the router to delay or drop the packet

classifier markerforward

shaper /dropper



Differentiated Services (DiffServ) – V

In the core routers, a DS-marked packet is forwarded according to a per-hop behavior (PHB) associated with the DS-tag the PHB determines how the router resources are used and shared

among the competing service classes the PHB should be based on the DS-tag only – simple forwarding

decisions, no need for QoS-states for each source-destination pair packets with same DS-tag are treated equally – regardless of

source or destination (traffic aggregating)

a PHB can result in different service classes receiving different performance

performance differences must be observable and measurable to be able to monitor the system performance

no specific mechanism for achieving these behaviors are specified- any mechanism can by used as long as the performance specification is met



Differentiated Services (DiffServ) – VI

Currently, two PHBs are under active discussion

expedited forwarding [RFC 3246] specifies a minimum departure rate of a class, i.e., a guaranteed

bandwidth the guarantee is independent of other classes, i.e., enough

resources must be available regardless of competing traffic

assured forwarding [RFC 2597] divide traffic into four classes each class is guaranteed a minimum amount of resources each class are further partitioned into one of three “drop”

categories(if congestion occur, the router drops packets based on “drop” value)



core routers

Differentiated Services (DiffServ) – VII

Edge router:use header fields to lookup right DS-tag and mark packet

Core router:use PHB according to DS-tag to forward packet

fast and scalable due to simple core routers



Internet Streaming Protocol, Version 2 (ST-II) – I

ST-II is defined by RFC 1190/1819 It is a connection-oriented supplement to IP

with two components: ST: reservations and data management SCMP (ST control message protocol): reliable

control messages

Main concepts: unreliable data transfers, reliable control a negotiated packet size (no fragmentation and reassembly) routing tree from sender to multiple receivers flow specification describing QoS parameters during connection

setup


linklink

transporttransport

ST-II ST-II SCMPSCMP



Internet Streaming Protocol, Version 2 (ST-II) – II

The resource reservation is sender-oriented SCMP sends a message with a flow specification if the routers and the destination accepts the call, the call is

returned (possibly modified) to the source typical parameters include

bandwidth delay delay variance size

Max delay

12

Min delay

2

size 4096

Max delay

12

Min delay

5

size 2048

Max delay

12

Min delay

9

size 2048

connect connect

accept/reject

Fast Routing



Routing Speed-up ATM

Virtual Channels and Virtual Path RSVP

IP and Port Mapping ST-II

Hop ID MPLS

Label



Multiprotocol Label Switching (MPLS)

Multiprotocol Label Switching Separate path determination from hop-by-hop

forwarding Forwarding is based on labels Path is determined by choosing labels

Distribution of labels On application-demand

LDP – label distribution protocol By traffic engineering decision

RSVP-TE – traffic engineering extensions to RSVP




MPLS works above multiple link layer protocols

Carrying the label Over ATM

Virtual path identifier or Virtual channel identifier Maybe shim

Frame Relay data link connection identifier (DLCI) Maybe shim

Ethernet, TokenRing, … Shim

Shim?



Link Layer HeaderShim


Shim: the label itself

Network Layer Header …

Shim

20 bitslabel

3 bitsexperimental

1 bitBottom of stack

8 bits TTL



Routing using MPLS

216.239.51.101

129.42.16.99 80.91.34.111

129.240.148.31

129.240.148.31

66.77.74.20

209.73.164.90192.67.198.54

209.189.226.17

193.99.144.71

81.93.162.20

…

Label 12 –

IF 1

Label 27 –

IF 2

…

Added label

Remove label

Reserved path for this label



MPLS Label Stack

ISP 1ISP 1

ISP 2ISP 2

ISP 3

The ISP 1 Classifies the packet Assigns it to a reservation Performs traffic shaping Adds a label to the packet

for routers in his net

The ISP 1 Buys resources from ISP 2The ISP 2 Repeats classifying, assignment,

shaping Adds a label for the routers in his net He pushes a label on the label

stack



MPLS Label Stack

ISP 1ISP 1

ISP 2ISP 2

ISP 3

The End:Summary



Summary Timely access to resources is important for multimedia

application to guarantee QoS – reservation might be necessary

Many protocols have tried to introduce QoS into the Internet, but no protocol has yet won the battle... often NOT only technological problems, e.g.,

scalability flexibility ...

but also economical and legacy reasons, e.g., IP rules – everything must use IP to be useful several administrative domains (how to make ISPs agree) router manufacturers will not take the high costs (in amount of

resources) for per-flow reservations pricing ...



Some References1. ATM Forum, http://www.atmforum.com2. ATM Forum: “ATM Service Categories”, http://www.atmforum.com/aboutatm/6.html3. Danthine, A., Bonaventure, O.: “From Best Effort to Enhanced QoS”,

in: Spaniol, O., Danthine, A., Effelsberg, W. (Eds.): “Architecture and Protocols for High-Speed Networks”, Kluwer Achademic Publishers, 1994, pp. 179-201

4. Kurose, J. F., Ross, K. W.: “Computer Networking: A Top-Down Approach Featuring the Internet”, 2nd edition, Addison Wesley, 2002

5. Steinmetz, R., Nahrstedt, C.: “Multimedia: Computing, Communications & Applications”, Prentice Hall, 1995

6. Tenet group: http://tenet.berkeley.edu/tenet.html

The RFC repository maintained by the IETF Secretariat can be found at http://www.ietf.org/rfc.htmlThe following RFCs might be interesting with respect to this lecture:

RFC 791: Internet Protocol RFC 1883: Internet Protocol, Version 6 (IPv6) RFC 2460: Internet Protocol, Version 6 (IPv6), Obsoletes: 1883 RFC 2212: Specification of Guaranteed Quality of Service RFC 2205: Resource ReSerVation Protocol (RSVP) RFC 1363: A Proposed Flow Specification RFC 2475: An Architecture for Differentiated Services RFC 3246: An Expedited Forwarding PHB (Per-Hop Behavior) RFC 2597: Assured Forwarding PHB Group RFC 1190: Experimental Internet Stream Protocol, Version 2 (ST-II) RFC 1819: Internet Stream Protocol Version 2 (ST2): Protocol Specification - Version

ST2+

Protocols with QoS Support

Documents

classes of qos

qos support299

reliable predictive

effort qos simple

granted requests qos

resource requirements

resource scheduling

hard boundsqos calculation