Networks - EdexcelPacket switching

TCP/IP uses packet switching to send data across a network. In packet switching, messages are broken up into very small pieces, called packets. Each packet consists of two parts:

• header - this includes the sender's and recipient's IP addresses, the packet number, the total number of packets the message contains, plus the details of any protocols used
• payload - this is part of the message itself

The packets are sent individually across the network and put back together to reform the message at the other end.

Packets may or may not follow the same route - they are sent along whichever route gives the quickest transmission. Therefore, packets may arrive out of sequence.

The recipient takes each packet, makes a note of its number and then puts it into the correct order. A packet switched network can therefore be fault tolerant. If a particular connection fails, the packets can be sent via a different route and then reassembled in the correct order. This is possible even if some packets are delayed.