Transmission Control Protocol (TCP) and Packet-Switching Hardware Devang Parekh EE290F 4/15/04
Jan 15, 2016
Transmission Control Protocol (TCP) and
Packet-Switching Hardware
Devang ParekhEE290F4/15/04
Outline
TCP OSI 7 Layer SYN/ACK Different Flavors
Routers What they do Protocols
OSI 7 Layer Model
OSI 7 Layer Model
Physical (Layer 1) Physical link layer Electrical impulse, radio, optical Lowest layer of the OSI Model
OSI 7 Layer Model
Data Link (Layer 2) Data packets encoded into bits Media Access Control (MAC) Layer
Controls how a computer gains access to a link and transmission on that link.
Logical Link Control (LLC) Layer Frame synchronization, flow control, error
checking
OSI 7 Layer Model
Network (Layer 3) Switching and routing performed at
this layer Addressing, internetworking, error
handling, congestion control, packet sequencing
IP
OSI 7 Layer Model
Transport (Layer 4) Transparent transfer of data End-to-end recovery Flow control TCP/UDP
OSI 7 Layer Model
Session (Layer 5) Manages end-to-end connections
Presentation (Layer 6) Acts as middleware for application
layer
Application (Layer 7) The program you use
TCP/UDP
UDP (User Datagram Protocol) Provides multiplexing/demultiplexing
to IP No congestion control Advantage: does not increase delay
over connection Audio/video stream
TCP/UDP
TCP (Transmission Control Protocol) Reliable, in-order delivery Multiplexing/Demultiplexing to IP Congestion control and avoidance Increases delay File transfer, chat
3-way handshake
3-way handshake
Goal: Agree on sequence numbers
State Diagram
Header
Header
Ports – self-explanatorySequence number, acknowledgement – used in sliding window protocolFlags SYN/FIN –establishing/terminating
connections ACK – acknowledgement is valid URG – urgent data RESET- abort connection
Sliding Window Protocol
Stop & Wait Transmit Wait for Ack If timeout send again
Go-back-n Transmit n packets If timeout at packet k, send again
from k, k+1, …
Congestion Control
Telephone Network: Reservation
TCP: Adapt rate to congestion Algorithm should be fair
UDP: Hope for the best
Congestion Control
Ex. TCP-Reno Congested -> decrease rate Uncongested -> increase rate Additive-Increase Multiplicative-
Decrease (AIMD)
Congestion Control
Fast retransmitFast RecoverySlow StartFlow Control
Congestion Control
Fast Retransmit ACK #= next expected ACK
Congestion Control
Slow Start Discover available bandwidth fast
Congestion Control
Flow Control Receiver advertises window
Routers
IP AddressingClasses
Routers
Functions Topology update Shortest path Switching
Routers
Topology Update Link State
Communicates name and distance to each neighbor
Distance Vector Communicates current distance estimates to
every other node Path Vector
Communicates current preferred path to every other node
Routers
Routers
Routers
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