Modeling and simulation of traffic control mechanisms in ATM networks

Abstract

Broadband Integrated Services Digital Network (B-ISDN) represents the most important development in the evolution of telecommunication systems. The aim of B-ISDN is to provide an all-purpose, flexible, efficient and cost effective environment for all new emerging services based on voice, video and data in an integrated fashion. High speed networks provide real-time variable bit rate service with diversified traffic flow characteristics and quality requirements. The main challenge here is the efficient use of network resources and mechanisms in order to achieve a satisfactory quality performance. In order to achieve the aggressive goal, which B-ISDN aims at, a promising transfer and switching technique called Asynchronous Transfer Mode (ATM) has been adopted. The Quality of Service (QoS) measures, such as, cell loss and delay in ATM nodes are the parameters that significantly contribute to the degradation of network performance. It is worth noting that the control of each of these parameters has a special impact on the other parameter, for example, voice traffic can tolerate some cell loss but is very sensitive to cell delay, while video and/or data transfer applications can allow for some delay but not the cell losses. For video applications, the loss of consecutive cells becomes even more critical when reproducing the original data. Buffer management in queueing systems plays important role towards effective control of QoS for various types of applications. Traffic can be shaped by placing cells into buffers to compensate for a difference in rate of flow of data or time of occurrence of events. With larger buffers, the probability of losing cell decreases but the overall delay increases. Hence, it becomes necessary to utilise buffering and scheduling algorithms to regulate QoS attributes in a high speed network. In this thesis, the focus is given on two important design factors, namely, buffer management and scheduling algorithms.