Illustrated TCP/IP by Matthew G. Naugle Wiley Computer Publishing, John Wiley & Sons, Inc. ISBN: 0471196568   Pub Date: 11/01/98

Chapter 36
Source and Destination Address Fields

The next fields are the source and destination address fields. These fields are very important for they identify the individual IP network and station on any IP network. These are particularly important, for users will be most aware of this when starting their workstation or trying to access other stations without the use of a domain name server or an up–to–date host file. These fields indicate the originator of the datagram, the final destination IP address that the packet should be delivered to, and the IP address of the station that originally transmitted the packet. All hosts on an IP internet will be identified by these addresses. IP addressing is extremely important and a full discussion follows. Currently, these addresses are set to 32 bits, which allows for over 4 billion addresses.

This may sound like a lot of addresses but unfortunately, many mistakes were made in assigning IP addresses to corporations and individuals. The mistakes were made unknowingly, for this protocol suite took off by surprise. This is fully discussed at the end of this section. There are two types of addresses: classless and classful. Both types will be presented.

Source and Destination Address Fields

IPv6, the next version of IP (currently being implemented as autonomous islands in the sea of IPv4), allows for 128 bits of address, which basically allows for thousands of billions of hosts to be numbered. Also, with IPv6, an efficient allocation scheme was developed to hand out IPv6 addresses as well.