Tài liệu giảng dạy CCNA - module 01 chapter 07 - Fundamentals of TCP and UDP

Introduction to transport layer  The primary duties of the transport layer are to transport and regulate the flow of information from the source to the destination, reliably and accurat

Module 01 InterNetwork Overview

Chapter 07 Fundamentals of TCP and UDP

Table of Content

1 Typical features of layer 4

2 The Transmission Control Protocol

3 The User Datagram Protocol

1 Typical Features of OSI Layer 4

Introduction to transport layer

 The primary duties of the transport layer are to transport

and regulate the flow of information from the source to the

destination, reliably and accurately

 The transport layer defines end-to-end connectivity

between host applications

 Transport services include the following basic services:

 Segmentation of upper-layer application data

 Establishment of end-to-end operations

 Transport of segments from one end host to another end host

 Flow control provided by sliding windows

 Reliability provided by sequence numbers and

acknowledgments

2 The Transmission Control

Protocol

6

7

Acknowledgment

9

 Supplies a virtual circuit between end-user applications

 Breacking outgoing messages into segments and

reassembles messages at the destination

 Resends anything not received by acknowledgement

 Flow control: Windowing

 The protocols that use TCP include: FTP, HTTP SMTP,

Telnet

• Source Port 16 bits.

• Destination Port 16 bits.

• Sequence Number: 32 bits

– The sequence number of the

first data octet in this segment (except when SYN is present).

TCP Header format:

Acknowledgment

• Acknowledgment Number: 32 bits

– This field contains the value of the

next sequence number the sender of

the segment is expecting to receive.

• Control Bits: 8 bits

– ACK : Acknowledgment field significant

– RST : Reset the connection

– SYN : Synchronize sequence numbers

– FIN : No more data from sender

• Window: 16 bits

– The number of data octets beginning

with the one indicated in the

acknowledgment field which the sender

of this segment is willing to accept.

 UDP transports data unreliably between hosts Following are the

characteristics:

 Connectionless.

 Unreliable, no software checking for message delivery

 Transmit messages, does not need reassemble incoming

UDP Header format

 UDP is a simple protocol that exchanges datagrams,

without acknowledgments or guaranteed delivery

8

RFC -76

8

TCP and UDP port numbers

 Both TCP and UDP use port (or socket) numbers to pass

information to the upper layers

00

RFC -17

00

Range of ports

 2 bytes: 0 – 65535

 Numbers below 255 : for public applications.

 Numbers from 255 - 1023 : assigned to

companies for marketable applications.

 Numbers above 1023 : are unregulated.

 End systems use port numbers to select proper

applications

 Originating source port numbers are dynamically assigned

by the source host; usually, it is a number larger than

1023

Telnet port number

Summary

 TCP:

 Connection-oriented.

 Supplies a virtual circuit between end-user applications

 Breacking outgoing messages into segments and reassembles

messages at the destination.

 Resends anything not received by acknowledgement.

 Flow control: Windowing

 UDP:

 Connectionless

 Unreliable, no software checking for message delivery

 Transmit messages, does not need reassemble incoming

messages.

 Without acknowledgements

 Error processing and retransmission must be handled by

higher layer protocols.