Internet Protocols

The Internet protocols are the world’s most popular open-system (nonproprietary) protocol suite
because they can be used to communicate across any set of interconnected networks and are equally
well suited for LAN and WAN communications. The Internet protocols consist of a suite of
communication protocols, of which the two best known are the Transmission Control Protocol
(TCP) and the Internet Protocol (IP). The Internet protocol suite not only includes lower-layer
protocols (such as TCP and IP), but it also specifies common applications such as electronic mail,
terminal emulation, and file transfer. This chapter provides a broad introduction to specifications that
comprise the Internet protocols. Discussions include IP addressing and key upper-layer protocols
used in the Internet. Specific routing protocols are addressed individually in Part 6, Routing
Protocols.
Internet protocols were first developed in the mid-1970s, when the Defense Advanced Research
Projects Agency (DARPA) became interested in establishing a packet-switched network that would
facilitate communication between dissimilar computer systems at research institutions. With the
goal of heterogeneous connectivity in mind, DARPA funded research by Stanford University and
Bolt, Beranek, and Newman (BBN). The result of this development effort was the Internet protocol
suite, completed in the late 1970s.
TCP/IP later was included with Berkeley Software Distribution (BSD) UNIX and has since become
the foundation on which the Internet and the World Wide Web (WWW) are based.
Documentation of the Internet protocols (including new or revised protocols) and policies are
specified in technical reports called Request For Comments (RFCs), which are published and then
reviewed and analyzed by the Internet community. Protocol refinements are published in the new
RFCs. To illustrate the scope of the Internet protocols, Figure 30-1 maps many of the protocols of
the Internet protocol suite and their corresponding OSI layers. This chapter addresses the basic
elements and operations of these and other key Internet protocols.