Edit by Nathaniel; December 11, 2008: I found out this is pirated. Phooey. So... link removed and you can buy it here in hard copy, PDF, or both.

Check this [link removed] out if you want an in-depth explanation of TCP/IP.

Edit by Nathaniel; September 23: Just warning you, this is a 12.7 megabyte PDF, so if you have a slow internet connection like me... now you know. Ta!