Internet Core Protocols: The Definitive Guide

IP Addresses

IP uses an anarchic and highly distributed model, with every device being an equal peer to every other device on the global Internet. This structure was one of IP’s original design goals, as it proved to be useful with a variety of different systems, it did not require a centralized management system (which would never have scaled very well), and also it provided for fault-tolerance on the network (no central management means no single point of failure).

In order for systems to locate each other in this distributed environment, nodes are given explicit addresses that uniquely identify the particular network that the system is on, and that also uniquely identify the system to that particular network. When these two identifiers are combined, the result is a globally unique address.

This concept is illustrated in Figure B.1. In that figure, the network is numbered 192.168.10, and the two nodes are numbered 10 and 20. Taken together, the fully qualified IP addresses for those systems would be 192.168.10.10 and 192.168.10.20.

Figure B.1. IP addresses consist of a network address and a node address

An IP address is actually a 32-bit binary number (in binary, 192.168.1.20 corresponds to 11000000101010000000101000010100). However, the 32-bit IP address actually consists of two sub-addresses, with one part identifying the network and the rest identifying the host to ...