This chapter discusses generic issues in connectionless network layer service. Subsequent chapters go into the specifics of various connectionless network layer protocols such as IP, IPX, AppleTalk, CLNP, and DECnet, but the concepts are introduced here. Why do I bother describing protocols that are dying out? Why don't I just describe IP, which the world is basically converging on? There are a number of reasons.
You will have a deeper understanding of IP if you also understand alternatives.
A lot of interesting ideas, both good and bad, are in the other protocols. It's important to write them down so that future designers can use the good ideas and learn from the bad ones.
Most protocols don't go away completely. ...