You might want to take a look at "Computer Networks" by A.S. Tanenbaum and D.J. Wetherall. It's available for free online at https://docs.google.com/viewer?a=v&pid=sites&srcid=ZGVmYXVsdGRvbWFpbnxza21pbmh8Z3g6NjQxMTI2MmYxMTAwZmNjZQ
Or you can buy a copy from your local bookseller. Enjoy! Rick