Data is being transferred through net. It have two types :
Circuit Switching : Dedicated circuit per call(Ex. telephone net).
Packet Switching : Data sent through net in discrete “chunks”.
Circuit Switching :
There are three phases in circuit switching :
- Establish
- Transfer
- Disconnect
The telephone message is sent in one go, it is not broken up. The message arrives in the same order that it was originally sent. In modern circuit-switched networks, electronic signals pass through several switches before a connection is established. During a call, no other network traffic can use those switches. The resources remain dedicated to the circuit during the entire data transfer and the entire message follows the same path. Circuit switching can be analogue or digital.
Packet Switching :
In packet-based networks, the message gets broken into small data packets. These packets are sent out from the computer and they travel around the network seeking out the most efficient route to travel as circuits become available. This does not necessarily mean that they seek out the shortest route. Each packet may go a different route from the others. Each packet is sent with a ‘header address’. This tells it where its final destination is, so it knows where to go. The header address also describes the sequence for reassembly at the destination computer so that the packets are put back into the correct order. One packet also contains details of how many packets should be arriving so that the recipient computer knows if one packet has failed to turn up. If a packet fails to arrive, the recipient computer sends a message back to the computer which originally sent the data, asking for the missing packet to be resent.
