NETWORKING CONCEPTS

PROTOCOLS In a n/w communication occurs b/w 2 entities Entity means anything that is capable of sending and receiving information For communication to occur the entiety must agree a protocol ie. protocol means a set of rule that govern data communication ie. It defines what is communicated How it is communicated When it is communicated

PROTOCOLS Key Elements of a protocol are Syntax Symantics and Timing Syntax Refers structure or format of data Eg. A simple protocol might expect the first 8 bit of data to be address of sender,2 nd 8 bit to be the address of the receiver and rest of stream to be the message itself

PROTOCOLS Key Elements of a protocol are Semantics Refers to meaning of each section of bits ie.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?

PROTOCOLS Key Elements of a protocol are Timing Refers to 2 characteristics When data should sent How fast they can sent Eg. if a sender produces data at 100 Mbps, the transmission will overload the receiver and some data will be lost.

STANDARDS Provides 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 standards Defacto Dejure

STANDARDS Defacto 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 Dejure Standards that are legislated by an officially recognized body are De Jure standards

FORUMS Standards committees are procedural bodies and slow moving So forums are developed.They are made up of representatives from interested corporations Forums work with universities and users to test,evaluate,and standardise new technologies The 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 MODEL n/w is a combination of h/w,s/w that sends data from one location to other h/w consist of any physical equipment that carries signals from one point of n/w to other s/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 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 TASKS We 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 are Higher 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 Way The 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 Way The 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 Site Lower 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 Site Lower 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.

Hierarchy There 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.

Services Each layer at the sending site uses the services of the layer immediately above it Sender at higher layer uses services of middle layer Middle layer uses services of lower layer Lower layer uses services of carrier