The best open source tool for network simulation is NS2. The first step to learn NS2 is to it. Cygwin gives linux like environment on Windows. Here is the step by step procedure how to install NS2:
Some other useful links for NS2.
- The Network Simulator: Building Ns, http://www.isi.edu/nsnam/ns/ns-build.html
- How to Compile Ns2 on Windows Platform, http://www.isi.edu/nsnam/ns/ns-win32-build.html
- Ns Manual, http://www.isi.edu/nsnam/ns/ns-documentation.html
- Tutorial for the Network Simulator “ns”, www.isi.edu/nsnam/ns/tutorial/index.html
- Tracegraph Program Download Page, http://www.geocities.com/tracegraph/
- NS by Example, http://nile.wpi.edu/NS/