MODULE INETWORKING CONCEPTS

PROTOCOLSIn a n/w communication occurs b/w 2 entitiesEntity means anything that is capable of

sending and receiving informationFor communication to occur the entiety must

agree a protocolie. protocol means a set of rule that govern

data communicationie . It defines what is communicatedHow it is communicatedWhen it is communicated

PROTOCOLSKey Elements of a protocol are

Syntax Symantics and TimingSyntax

Refers structure or format of dataEg. A simple protocol might expect the

first 8 bit of data to be address of sender,2nd 8 bit to be the address of the receiver and rest of stream to be the message itself

PROTOCOLSKey Elements of a protocol are

SemanticsRefers to meaning of each section of

bitsie.how a particular pattern to be

interpreted and what action to be taken based on that interpretation

Eg.whether an address identify the route to be taken or the final destination of the message?

PROTOCOLSKey Elements of a protocol are

TimingRefers to 2 characteristicsWhen data should sentHow fast they can sentEg. if a sender produces data at 100

Mbps , the transmission will overload the receiver and some data will be lost.

STANDARDSProvides guidelines to

manufacturer,vendors,govt agencies and othe rservice providers to ensure the kind of interconnectivity necessary in today’s market place and in international communication

2 categories of standardsDefactoDejure

STANDARDSDefacto

Standard that have not been approved by an international body but have standards are often estabilished originally by manufacturers who seek to define the functionality of a new product or technology

DejureStandards that are legislated by an

officially recognized body are De Jure standards

FORUMSStandards committees are procedural bodies

and slow movingSo forums are developed.They are made up of

representatives from interested corporationsForums work with universities and users to

test,evaluate,and standardise new technologiesThe forums submit their conclusion to the

standard bodies based on the acceptance and use of those technologies in the telecommunication community

Protocol Architecture

The entities comprising the corresponding layers on different machines are called peers.

The peers that communicate by using the protocol to talk to each other.

Each layer passes data and control information to the layer immediately below it, until the lowest layer is reached.

Below layer 1 is the physical medium through which actual communication occurs.

Between each pair of adjacent layers is an interface. The interface defines which primitive operations and services

the lower layer makes available to the upper one.A list of the protocols used by a certain system, one protocol per

layer, is called a protocol stack.A set of layers and protocols is called a network architecture.

NETWORK MODELn/w is a combination of h/w,s/w that sends

data from one location to otherh/w consist of any physical equipment that

carries signals from one point of n/w to others/w consist of instruction set that make

possible the services that use expect from a n/w

eg. Consider service provided by a network like email sending from one point in world to other

It can be broken up to several task performed by separate s/w package and each s/w package uses services of other s/w package

At lowest layer a signal or a set of signals is sent from source computer to the destination computer

LAYERED TASKSWe use the concept of layers in our daily life.

As an example, let us consider two friends who communicate through postal mail. The process of sending a letter to a friend would be complex if there were no services available from the post office.

Tasks involved in sending a letter

In fig there is sender ,receiver, carrier that transports letter

Hierarchy of tasks involved areHigher layer.

The sender writes the letter inserts the letter in an envelope writes the sender and receiver addresses and drops the letter in a mailbox.

Middle layer. The letter is picked up by a letter carrier and delivered to the

post office.Lower layer.

The letter is sorted at the post office; a carrier transports the letter.

On the WayThe letter is then on its way to the recipient.On the way to the recipient's local post office,

the letter may actually go through a central office.

In addition, it may be transported by truck, train, airplane etc

On the WayThe letter is then on its way to the recipient.On the way to the recipient's local post office,

the letter may actually go through a central office.

In addition, it may be transported by truck, train, airplane etc

At the Receiver SiteLower layer.

The carrier transports the letter to the post office.

Middle layer. The letter is sorted and delivered to the

recipient's mailbox.Higher layer.

The receiver picks up the letter, opens the envelope, and reads it.

At the Receiver SiteLower layer.

The carrier transports the letter to the post office.

Middle layer. The letter is sorted and delivered to the

recipient's mailbox.Higher layer.

The receiver picks up the letter, opens the envelope, and reads it.

HierarchyThere are three different activities at the sender site and

another three activities at the receiver site. The task of transporting the letter between the sender and

the receiver is done by the carrier. The tasks must be done in the order given in the hierarchy.

At the sender site, the letter must be written and dropped in the mailbox before being picked up by the letter carrier and delivered to the post office.

At the receiver site, the letter must be dropped in the recipient mailbox before being picked up and read by the recipient.

ServicesEach layer at the sending site uses the

services of the layer immediately above itSender at higher layer uses services of middle

layerMiddle layer uses services of lower layerLower layer uses services of carrier