Massachussets Institute of Technology: Hari Balakrishnan's "The Internetworking Problem"

Read these lecture notes. As you read, pay special attention to the history and different versions of internetworking structure based on TCP/IP protocols.

Click http://ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-829-computer-networks-fall-2002/lecture-notes/L2Internetworking.pdf link to open resource.