Introduction

o TCP (Transmission Control Protocol) is a standard that defines how to establish and maintain a network conversation via which application programs can exchange data.

o TCP works with the Internet Protocol (IP), which defines how computers send packets of data to each other. Together, TCP and IP are the basic rules defining the Internet.

What is TCP/IP ?oTCP stands for “Transmission Control Protocol”

o IP stands for “Internet Protocol”o TCP/IP is a set of protocols developed to allow cooperating computers to share resources across a network.

oThey are Transport layer and Network layer protocols respectively of the protocol suite

o The most well known network that adopted TCP/IP is Internet – the biggest WAN in the world.

What is a protocol?

A protocol is a collection of rules and procedures for two computers to exchange information.

Protocol also defines the format of data that is being exchanged.

Objectives.. To introduce TCP as a protocol that

provides reliable stream delivery service.

To define the format of a TCP segment and its fields.

To show how TCP provides a connection-oriented service, and show the segments exchanged during connection establishment and connection termination phases.

To discuss the state transition diagram for TCP and discuss some scenarios.

To introduce windows in TCP that are used for flow and error control.

To list and explain the purpose of each timer in TCP.

Overview Of TCP/IPo Oldest networking standard developed for US department’s ARPANET. o Most popular network protocol. o Allows reasonably efficient and error – free transmission. o A file transfer protocol , sends large files uncorrupted across unreliable networks. o Compatible with a variety of data link protocols hence popular.

TCP/IP Model Because TCP/IP was developed

earlier than the OSI 7-layer mode, it does not have 7 layers but only 4 layers

FTP, SMTP, Telnet, HTTP,…

TCP, UDP

IP, ARP, ICMP

Network Interface

Application layer protocols

o It define the rules when implementing specific network applications

o Rely on the underlying layers to provide accurate and efficient data delivery.

Typical protocols:• FTP – File Transfer Protocol

• For file transfer• Telnet – Remote terminal protocol

• For remote login on any other computer on the network• SMTP – Simple Mail Transfer Protocol

• For mail transfer• HTTP – Hypertext Transfer Protocol

• For Web browsing.

TCP Protocol Suit

Stream Delivery

Sending & Receiving Buffers

Stream of bytes

Errors Controlo TCP is a reliable transport layer

protocol. This means that an application program that delivers a stream of data to TCP relies on TCP to deliver the entire stream to the application program on the other end in order, without error, and without any part lost or duplicated.

o Error control in TCP is achieved through the use of three tools: checksum, acknowledgment, and time-out.

TCP over wireless networks

o TCP has been optimized for wired networks. Any packet loss is considered to be the result of network congestion and the congestion window size is reduced dramatically as a precaution.

o However, wireless links are known to experience sporadic and usually temporary losses due to fading, shadowing, hand off, and other radio effects, that cannot be considered congestion.

o After the (erroneous) back-off of the congestion window size, due to wireless packet loss, there can be a congestion avoidance phase with a conservative decrease in window size. This causes the radio link to be underutilized.

Network Layero ICMP (Internet control

message protocol) - handles error & controls messages.

o ARP (Address resolution protocol) – obtaining the physical address of a mode when the internet address is known.

o RARP (Reverse address resolution protocol) – allows a host to discover its internet address when it knows only its physical address.

Port Multiplexing

o A computer may perform a number of network applications at the same time

• FTP + SMTP + HTTP, etc.

o Each computer has only one network address, how can it serve so many applications at the same time?

Port 25

Port 21Port 80

Network add:158.132.161.99

Overview Of Routing

o How a packet finds its way to a computer in a network?•By using Routers :

o Routing is the selection of a path to guide a packet from the source to the destination.

o Criteria in selecting a path may be:• Shortest path• Quickest path• Cheapest path

o Each router has a table that records the estimated distance to all other routers.

o If a router knows the entire network topology, the shortest path can be calculated.

o To achieve this, routers broadcast Link State Advertisement to all other routers periodically.

o By means of routing protocolo Each router knows the exact topology, and then calculates the shortest path.

o In practice, it is not possible for a router to all paths. Only the nearer ones are kept