The TCP/IP Guide  9  TCP/IP Lower-Layer (Interface, Internet and Transport) Protocols (OSI Layers 2, 3 and 4)       9  TCP/IP Internet Layer (OSI Network Layer) Protocols            9  Internet Protocol (IP/IPv4, IPng/IPv6) and IP-Related Protocols (IP NAT, IPSec, Mobile IP)

IP History, Standards, Versions and Closely-Related Protocols 1 IP Addressing

Even though the name seems to imply that it's the fourth iteration of the key Internet Protocol, version 4 of IP was the first that was widely used in modern TCP/IP. IPv4, as it is sometimes called to differentiate it from the newer IPv6, is the Internet Protocol version in use on the Internet today, and an implementation of the protocol is running on hundreds of millions of computers. It provides the basic datagram delivery capabilities upon which all of TCP/IP functions, and it has proven its quality in use over a period of more than two decades.

In this section I provide extensive detail on the operation of the current version of the Internet Protocol, IPv4. There are four main subsections, which represent the four main functions of IP. The first subsection provides a comprehensive discussion of IP addressing. The second discusses how data is encoded and formatted into IP datagrams for transmission. The third describes datagram size issues and how fragmentation and reassembly are used to convey large datagrams over networks designed to carry small frames. The last subsection covers matters related to the delivery and routing of IP datagrams. After the four main subsections I conclude our look at IPv4 with an overview of IP multicasting, which is used for delivering a single datagram to more than one recipient.

IP History, Standards, Versions and Closely-Related Protocols 1 IP Addressing