To find out more about UNIX TCP/IP and related concepts, consult these resources:
Comer, Douglas E., and D. Stevens. Internetworking with TCP/IP, Volumes I, II, and III (various editions). Englewood Cliffs and Upper Saddle River, NJ: Prentice Hall, 1996–2005.
Petersen, Richard. Linux: The Complete Reference. 5th ed. Berkeley, CA: McGraw-Hill-/ Osborne, 2002.
Petersen, Richard. UNIX Networking Clearly Explained. Chestnut Hill, MA: AP Professional, 1999.
Stevens, R. UNIX Network Programming. Volumes I and II (various editions). Englewood Cliffs and Upper Saddle River, NJ: Prentice Hall, 1998–2003.
You can consult some useful web sites for additional information about the Secure Shell. In particular, FAQs on the Secure Shell can be found at http://www.employees.org/~satch/ssh/faq/. An excellent tutorial on the Secure Shell is available at http://www.tac.nyc.ny.us/~kim/ssh/#ss. You can also consult the newsgroup comp.security.ssh.