This book assumes basic familiarity with TCP/IP and
networking concepts. You won't find a primer on the OSI seven-layer model
or a rundown of the Berkeley Socket API within these pages. For a
comprehensive guide to TCP/IP, I
TCP/IP Guide” by Charles Kozierok or the old
Illustrated, Volume I” by W. Richard Stevens.
While TCP/IP familiarity is expected, even the best of us
occasionally forget byte offsets for packet header fields and flags.
This section provides quick reference diagrams and field descriptions
for the IPv4, TCP, UDP, and ICMP protocols. These beautiful diagrams
from http://www.visi.com/~mjb/Drawings are used by
permission of author Matt Baxter.