You can find lots of stuff about ISO's OSI on the web. However, you should proceed with caution since according to what I have read, TCP/IP does not really fit that well (for example, layers 5 and 6 are archaic and layer 3 needs some work). The computing world kind of passed OSI by. There is a gentleman from The Netherlands by the name of Tanenbaum who has written some good books about computer networking from a theoretical point of view.