Types of Switching (Data Transmission)

Circuit Switching


Creates a direct link between two devices for the duration of communication.


Example is a telephone system. If you are calling somebody on your mobile and somebody tries to ring you they will get a 'user is unavailable message'. This is because when a call is made a direct path in a telephone exchange is made by various switches.


Advantages of this is that it is quick (no delay) as there is no interference and also the fact that it is simple to set up. Only two people are using the connection at once, everyone else would be rejected.


Disadvantage is that only one connection can be made at once, group calls are multiple calls on one line aren't possible. Also it wastes a lot of bandwidth, even if a person is on hold the line is still in use/data being sent so no one else could use it.


It is important with Circuit Switching that data is sent/received at the same rate otherwise there will be delays/pauses in the call. Data always arrives in the order it was sent.





Packet Switching

This is the main/most common method of network communication.

All data is broken down into equal packets (each packet is between 500 and 1500 bytes in size) which are then sent between devices.

Each packet contains a header (which holds the sender and recipient IP address, the protocol being used and the amount of packets), and a payload which actually contains the data.

When the packets are received they are reassembled by the recipient computer to make the data.

Sometimes a CRC checksum calculation is done on each packet to make sure it is correct (what the computer was expecting), if this calculation fails then the computer rejects the packet and requests it be re-sent by the sender.








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