How to simulate tcp/ip network protocol stack in usermode

Question

I want to simulate tcp/ip network protocol so that I can debug it and learn how it works.I just want to implement a small part of it,but I don't know how to start,what should I do ? Any help will be grateful...

Answer 1

Learning NS-2 would be a good start: http://www.isi.edu/nsnam/ns/ . This is a popular simulator that is widely used in research/academics and has a rich collection of TCP congestion protocols.