The TCP/IP protocol suite
was designed to let machines, connected by a variety of
network technologies (e.g.
Ethernet, telephone-wires,
radio, satellites, ATM,
etc.), communicate with each other. Today it is best known as the
protocol used for the Internet, the
global network that grew from the experiments of the U.S. Defense
Advanced Research Project Agency on the ARPANET.
One of the most important aspects of the IP suite is the abstraction from the physical networks it uses. In a way, IP provides a virtual ``physical'' network on top of a heterogenous structure of connected real physical networks.
The expression ``physical network'' comes from Comer's book [DC91]. Another commonly used expression for the physical network is Local Area Network (LAN). Both physical network and LAN seem to be used by most authors as a reference to the physical transmission technology as well as the Network Interface layer on top of it. The hardware implementation aspects will be avoided as much as possible, so the term LAN is used for clarity.
The goal in this chapter is to introduce a way of describing networks, to describe the TCP/IP protocol suite using this method and to introduce an implementation architecture view for future reference.