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Transmission Control Protocol

(TCP)

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Position of TCP in TCP/IP protocol suite

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TCPTCP• TCP is a connection-oriented protocol, it TCP is a connection-oriented protocol, it

creates a virtual connection between two TCPs creates a virtual connection between two TCPs to send data.to send data.

• TCP uses flow and error control mechanisms TCP uses flow and error control mechanisms at the transport level. at the transport level.

• It adds connection-oriented and reliability features to the services of IP.

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TCP Services

• Process-to-Process Communication.

• Stream Delivery Service.

• Full-Duplex Communication.

• Connection-Oriented Service.

• Reliable Service.

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TCP ServicesProcess-to-Process Communication

Like UDP, TCP provides process-to-process communication using port numbers.

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Well-known ports used by TCP

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PROCESS TO

PROCESSCOMMUNICATION

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Figure 12-2

TCP versus IP

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Figure 12-3

Port numbers

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TCPSERVICES

12.212.2

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Figure 12-4

Stream delivery

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TCP Services

Stream Delivery Service ‘Sending and

receiving buffers’

• TCP needs buffers for storagethe sending and the receiving processes may not

write or read data at the same speed.

• There are the sending buffer and the receiving buffer, one for each direction.

• It is necessary for flow and error control mechanisms.

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Figure 12-5

Sending and receiving buffers

Stream of bytes

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TCP Services Stream Delivery Service ‘TCP segments’

• The IP layer, as a service provider for TCP, needs to send data in packets, not as a stream of bytes.

• At the transport layer, TCP groups a number of bytes together into a packet called a segment.

• TCP adds a header to each segment (for control purposes) and delivers the segment to the IP layer for transmission.

• The segments are encapsulated in IP datagrams and transmitted.

• the segments are not necessarily the same size.

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Figure 12-6

TCP segments

Segment 1

H

Segment N

H

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NUMBERINGBYTES

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The bytes of data being transferred The bytes of data being transferred in each connection are numbered by TCP. in each connection are numbered by TCP.

The numbering starts with The numbering starts with a randomly generated number.a randomly generated number.

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Example 1Example 1

Suppose a TCP connection is transferring a file of 5,000 bytes. The first byte is numbered 10,001. What are the sequence numbers for each segment if data are sent in five segments, each carrying 1,000 bytes?

SolutionThe following shows the sequence number for each segment:

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SolutionSolution

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The value of the sequence number field in a segment defines the number

of the first data byte contained in that segment.

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Figure 12-7

Sender buffer

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Figure 12-19

TCP segment format

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Figure 12-20

Control field

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Urgent Pointer

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TCPOPERATION

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Figure 12-33

Encapsulation and decapsulation

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Figure 12-34

Multiplexing and demultiplexing

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TCP Connection

• In TCP, connection-oriented transmission requires three phases:

1. connection establishment.

2. data transfer.

3. and connection termination.

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TCP Connection

Connection establishment:

• Three-way Handshaking

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Three-way Handshaking

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Three-way hand-shake

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Check Sum(TCP Header)