Communication Network Protocols

Jaya KalidindiCSC 8320(fall 2008)

Overview

Network Protocols OSI Protocol Suite TCP/IP Protocol Suite Protocol Examples in Internet Network References

Network Protocols

Network protocols are sets of standard rules : To regulate the exchange of messages

For Representing the data,authentication and error detection.

To provide a reliable communication.

What does a protocol tell us?

Syntax of a message what fields does it contain? in what format?

Semantics of a message what does a message mean? for example, not-OK message means

receiver got a corrupted file Actions to take on receipt of a message

for example, on receiving not-OK message, retransmit the entire file

Protocol layering

A network that provides many services needs many protocols

Turns out that some services are independent but others depend on each other

Protocol A may use protocol B as a step in its execution for example, packet transfer is one step in the

execution of the example reliable file transfer protocol This form of dependency is called layering

reliable file transfer is layered above packet transfer protocol

like a subroutine

OSI Protocal Suite

Physical Layer

First level in Network Layer Handles all the physical aspects of

communication between two directly connected physical entities.

Provides the basis for higher level communication services.

Main functionality is to transmit bits.

Data Link Layer

This layer accepts the bit streams provided by the physical layer .

Provides reliability of transfer of data between two directly connected entities.

Its functionality includes error detection control, flow control and access control.

Divided into two sub-layers: Medium Access Control Logical Link Control

MAC sub-layer

Defines means by which physical means may be accessed.

It co-ordinates to seize a shared channel by multiple MAC entities.

Provides a limited form of error control.

Ethernet is an example of a shared medium with defined MAC sub-layer functionality.

LLC sub-layer

It is responsible of reliable transfer of message-link protocol data units between two directly connected layer 2 entities.

LLC services can be Connection oriented: Frames are

individually numbered and acknowledged by their sequence number.

Connection-less: Messages are not acknowledged.

Data link layer

Transport Layer

Concerned with getting level 4 messages form source to destination in a reliable manner.

Functions are: Windowing and flow control. Error detection and recovery. Multiplexing.

Continued…

Two types of service quality:

Reliable service: makes sure that data is not lost and provides data error-free to the user.

Un-reliable service: does not have a mechanism to show that receiver has received the data sent.

Network Layer

Used to support data communication between indirectly connected entities.

Has the ability to forward messages from layer 3 entity to another, until final destination is reached.

Functions are: Routing Forwarding packets to final destination

port. Providing logical addressing.

Session layer

Controls communication or dialogues between applications on hosts.

Synchronization is achieved at coordinated timing .

NFS, NetBios, SQL are some examples.

Session initiation protocol

Presentation Layer

Performs data transformation or formatting if required by the end applications.

Functions are: Data compression File formatting Encryption

• MPEG, Quicktime are some examples.

Application Layer

Provides services that directly support an application that runs on the host.

Most network management activities are based on services provided by the layer 7.

FTP, Telnet, SNMP, SMTP are some examples.

OSI vsTCP/IP

FTP (file transfer control )

Allows users to access remote file servers, list remote directories, and move files to or from remote hosts.

FTP understands basic file formats and can transfer files in ASCII character or binary format., FTP provides a standard

UNIX-like user interface, regardless of the actual underlying operating system.

Telnet

Telnet provides a remote terminal access protocol running over Transport Control Protocol. It allows a user at one site to establish a virtual circuit connection to a remote system

Using Telnet, a user at one

host can login to another host, appearing like directly attached.

SNMP

Is an application service that has evolved with the growth of TCP/IP. It was derived from a low-overhead protocol designed to monitor Internet

routers

UDP

The User Datagram Protocol (UDP) is a Transport Layer protocol in the TCP/IP protocol suite. UDP provides a connectionless, best effort delivery service

UDP.

SMTP

Email is the most widely used application on the Internet (although it does not account for the highest volume of traffic). The Simple mail transfer protocol (SMTP) provides a simple, text-oriented protocol to transfer mail reliably between TCP/IP-based systems

Reference

R. Chow and T. Johnson. Distributed Operating Systems & Algorithms. 1997

Jim Kurose, Keith Ross, Computer Networking: A Top Down Approach Featuring the Internet, 3rd edition. Addison-Wesley, July 2004.

Cisco Systems, OSI Network Protocols, October 2006.

Diagrams:www.wikipedia.org,www. google.com

TCP/IP

THANK YOU