; the final 16 bits as host identifier. Class C: The first three bits 1,1,0 act as class identifier; the next 21 bits as network identifier; the final eight bits as host identifier. The IP addresses are written as four decimal numbers separated by points, with each of the four numbers ranging from 0 to 255. If the value of the first byte is less than 128, it represents class A addresses, 128-191 represent class B addresses, and 191-223 represent class C addresses. Addresses above the value of 223 are reserved addresses. Another aspect to know of when doing IP planning is that of 'sub-network or subnet'. With the standard addressing scheme, a single administrator is responsible for managing host addresses for the entire network. As networks are growing rapidly, local changes may become impossible, thereby requiring a new IP address for the 'new' network. By using the concept of 'subnet-working', the administrator can delegate address assignment to smaller networks within the entire network. By sub-netting it is possible to divide the whole network into smaller networks in such a way that each of these smaller networks has its own unique address; and this address is still considered to be a standard IP address. The combination of the sub-net number and the host number is known as the local address. Subnet addressing is done in such a way that it is transparent to remote networks. IP Routing When the addresses have been defined, the next step is to route the traffic. Routing involves transportation of the packet data to the right host and via an optimal path. There are many parameters that determine the selection of the path, and there are algorithms that can be used to do the calculations. These algorithms generally need information such as the source address, the destination address and the next hop address. The core gateways have all the information about the networks that is necessary to find the optimal route for data. This is done through the gateway-to-gateway protocol (GGP). For traffic routing in a complex 