httest is a script based tool for testing and benchmarking web applications, web servers, proxy servers and web browsers. httest can emulate clients and servers in the same test script, very useful for testing proxys.
Virtop is a software providing solution for simulating computer networks with scenarios on a single machine. It is mainly intended for education purposes like organizing practice classes in computer networks in the universities.
VNUML is a virtualization tool designed to quickly define and test complex network simulation scenarios based on the great User Mode Linux (UML) virtualization software.