The authors provide an in-depth look at individual TCP/IP protocols in light of design alternatives, implementation techniques with actual ANSI C code, and the internals of protocol software. This book uses the widely accepted data-mark interpretation of TCP urgent data, and a discussion of the consequences is included. Throughout the book the authors use a working system— which they designed and built using ANSI C—to explain the interaction among protocols, the complete implementation process, and the internal structure.