Saturday, December 20, 2008

Concept of Packets

Most computer networks do not transfer data as an arbitrary string of continuous bits.Instead the network system divides the data into small blocks called packets,which it sends individually.Computer networks are often called packet networks or packet switching networks because they use packet technology.The concept of using data packets for data transmission is supported by two facts,first a sender and receiver need to coordinate transmission to ensure that data arrives correctly.Dividing the whole data into small blocks helps a sender and receiver to determine which blocks arrive correctly and which blocks do not.

The second fact that supports packet technique is as all we know that communication circuits and modem hardware are expensive,multiple computers often shares underlying connection and hardware.To ensure that all computers receive fair,prompts access to a shared communication facility,a network system cannot allow one computer to access deny to other computers.Using small packets helps ensure fairness.Let understand this more clearly.The networks that do not packet technology allows an application program(computer) to hold a shared communication resource arbitrarily long that means an application was permitted to finish before another application could begin using the resource.But now the networks that uses packet technology have a solution of this problem.Here the networks permits one computer to send a packet of data and then blocks that computer from sending another packet.Meanwhile the network permits another computer to send a packet and so on.A single computer can hold a shared resource only long enough to send single packet,and must wait until other computers have a turn before sending a second packet.

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