Development of a network simulator modifying NS2 for evaluating Qos parameters of hybrid networks

Abstract

With the advent of multimedia networking, sincere attempts in guaranteeing quality of service (QoS) through appropriate devices and protocols are essential in designing the next generation advanced networks. Although test-beds and real world experiments can produce much more realistic results than simulations, implementing a large and complex experimental scenario is rather challenging. Therefore, many researchers employ NS2 simulations to test their ideas in the early stage of protocol design. Typically, each researcher writes his/her own NS2 scripts, and much time is spent in processing the raw data produced by the simulator, during extraction of the valuable information. On the other hand, the community still lacks a set of ready-made module to measure QoS parameters and to demonstrate how the QoS parameters are affected by variations of other network parameters. Several researchers have proposed some post-processing techniques. However, they involve a huge amount of time and consume a huge memory. Moreover, the existing techniques are not so versatile to be deployed for wired, wireless and hybrid networks. In this research work, the existing NS2 simulator is modified to include the new modules and corresponding scripts and codes so that it would be capable of taking various inputs and providing appropriate outputs representing the QoS for the wired, wireless and hybrid data networks without requiring any post-processing. Two new modules have been devised with there inherent capability of collecting data, calculating different QoS parameters during simulation, and present them graphically immediately after completion of the simulation without any further post-processing. To facilitate the work of the newly developed agents, the existing packet format is also modified. The newly devised agents added to NS2. not only facilitate the representation of output data in user-friendly format, but also reduce the total simulation time and memory consumptions. Moreover, with a slight post-processing of the output produced by the two QoS monitoring agents, users would be able to get more versatile outputs. In addition, a newly devised protocol, namely, Acknowledgement Augmented UDP (AAUDP) is proposed, which incorporates the aggressive data sending approach ofUDP, xv \ and also the error-correcting capabilities ofTCP ingeniously. The analytical model of the newly devised protocol is also developed. Finally, the new protocol is implemented and incorporated with the modified simulator, to demonstrate the improvements in the performance of the proposed AAUOP protocol in comparison with basic TCP and UOP, especially, in an over-congested link. The results found after simulation, prove that the AAUOP is outperforming the performance of both its predecessors' (TCP and UOP) elegantly, as anticipated initially.