Internet protocol address. An address which consists of a 32-bit number, and is represented by the dot-decimal format. For example: 141.110.200.1 is an IP address. There are four decimal digits separated by three dots. Each digit is allowed the range of 0 to 255. This range corresponds to eight bits (one byte) of information.

A portion of an IP address represents the network address, and the remaining portion the host address. For example, 141.110.200.1 is the IP address of a firewall. The network that the firewall resides on is 141.110.200.0 (note that IP addresses which end in a 0 represent network addresses). The host address of the firewall is 0.0.0.1 (note that the network portion of the IP address is represented by 0s). Each host on the network (and the internet) must have a unique IP address.

The Network Information Centre assigns network addresses to the internet. Its representative in the UK is Nominet UK. An application must be made for an IP network address. Depending on the class of the IP address, the applicant can then assign as many host IP addresses as are allowed. An alternative is to “rent” IP addresses from a local internet service provider (ISP). ISPs usually own the rights to a block of IP addresses, and will rent them out for a fee.

For further information, see the Nominet website.