Simulation methodology has become popular among computer and telecommunication network researchers and developers worldwide. This popularity is due to the availability of various sophisticated and powerful simulation packages, and also because of the flexibility in model construction and validation offered by simulation. For selecting an appropriate network simulator for a simulation task, it is important to have good knowledge of the simulation tools available, along with their strengths and weaknesses. It is also important to ensure that the results generated by the simulators are valid and credible. The objective of this paper is to survey, classify, and compare telecommunication network simulators to aid researchers in selecting the most appropriate simulation tool. We compare the network simulators based on type, deployment mode, network impairments and protocol supported. We discuss simulator evaluation methodologies and techniques, and provide guidelines for best practice in network simulation.