Network Simulator (1)


ns: Network Simulator
http://www.isi.edu/nsnam/ns/

Can be used on major OSs (Linux, FreeBSD, NetBSD, Windows...)
Supports lots of protocols
Application-level
HTTP, telnet, FTP
Transport protocols level
UDP, TCP, RTP, SRM
Supports various TCP versions: Tahoe, Reno, NewReno..
Router Mechanism level
Various queuing mechanism: CBQ, RED, ECN 
Link-layer mechanisms level
CSMA/CD
High extensibility
Lots of protocol functions are provided as C++ object class