Simulation of a large scale ATM network with VoIP traffic

IP telephony (Voice over IP – VoIP) has become an important driver for packet-based communications. The impact of the growing VoIP traffic on communication networks, especially backbone networks cannot be neglected. Telecom service providers must be aware that VoIP is the newest, fast-growing alternative for voice communication. Unlike voice transmission over the public telephone network, VoIP networks is frequently unreliable, and non-deterministic which is a consequence of using IP as a transport medium. This fact makes the proper analysis of the network indispensable before deploying VoIP. In a heavy-loaded network with bursty traffic sources the round-trip delay and the jitter can easily grow beyond the acceptable values. In this case using network simulation as an analysis tool can answer the question of network performance and transmission quality. To archive this the proper modeling of the traffic sources (beside VoIP the bursty background traffic) is needed. This paper tries to show the overview of the general phases of modeling a VoIP source and a HTTP source for the background traffic, focusing on a heavy-loaded, large scale ATM network environment. The goal of the whole project was to build a model of the ATM backbone for a Hungarian telecom provider. This network interconnects the regional centers of the country through a central switch in a star topology. Information about link utilization, traffic throughput, cell loss, ATM and VoIP delay should be gathered.