Packet data

When transferring data, it is important that the transfer of data is performed in a way which works alongside the network hardware.

Modern networks use a technology called packet switching, whereas older networks (think the old phone network) use circuit switching.

Consider the example where you have two computers, one at home, and one somewhere else many miles away (maybe a web server). You are not going to connect directly to the web-server, as that would require a dedicated line between your PC and the server, which is not feasible. (Imagine every computer needing a direct connection to every other computer…)

Instead, the Internet is formed from switches and routers: these break up the ‘journey’ from A to B into a series of smaller steps, whereby the data passes from router to router, until it reaches the destination (this is a guided process: it isn’t random!).

When using a packet-switching network, data is split up into chunks, called packets. Each packet contains not only data, but also information about:

• Source address (where it came from)
• Destination address (where it’s going)
• What packet is it? (e.g. 1st of 5 packets)

In packet switching, the route that each packet takes from source to destination is independent of the route that other packets take; that is, five packets could take five different routes to the destination.

This allows an improvement in throughput – if one part of a network is congested, data can be routed through a different path.