Transmission Control Protocol (TCP) and Packet-Switching Hardware Devang Parekh EE290F 4/15/04.

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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