2.14 IP Header Files

At the network layer, IP datagrams consist of header and data. The header contains detailed and extensive information describing routing information for the datagram such as the source and destination address. IP headers have a length of at least 20 bytes. All the IP headers are organized into four-byte words since nodes and routers normally process four bytes simultaneously.

By looking at the meanings of the different IP datagram header fields (as shown in Animation 2.14-1), it becomes easier to understand how datagrams are created and routed through the network.