In the scenario of increasing heterogeneous networks, the testing of network protocols and its accuracy, Mobility issues, Optimization, Problems with wireless links and its solutions are the major working areas. This calls for the need of best testing tools to perform and deliver up to the mark. While Simulation outcomes provides only with synthetic environment for protocol testing, Emulation takes into consideration the network dynamics. Thus the latter gives the feeling of working on live network. NIST Net is one such emulator for Linux which can emulate critical end-to-end performance characteristics such as congestion loss, packet reordering, or asymmetric bandwidth conditions imposed by various wide area network situations. So it provides with a platform useful for researchers in measuring and comparing the performance of customized protocol.