Traffic shaping in high speed ATM computer networks

Voice, data, and video traffic have radically different performancerequirements and they are very bursty in their nature. The bursty nature ofthe traffic is the pnmary cause of congestion. Congestion results inundesirable performance degradation such as long cell delay, high cell loss,and large buffer requirements. Congestion control is the network functionthat attempts to avoid or control congestion and limits its effects.Congestion control is an essential part of B-ISDN in order toguarantee its performance level. The high transmission rate of such networksand the support of different services with divers traffic characteristics makethe congestion control problem more complicated and more challenging thanin the conventional networks.Traffic shaping has been proposed as congestion control mechanismto control the input rate and smooth the burstiness of the traffic. Shaping thetraffic when it enters the network makes the traffic smoother and morepredictable, thus reducing the probability of the congestion.This thesis studies the effects of the conventional traffic shaping onthe performance of the network using OPNET simulator. An ATM based B-ISON network model, a traffic ’model, and a shaper model are developed,simulation results show that conventional traffic shaping can provide goodnetwork level performance, i.e., low queuing delay and low cell loss insidethe network. However, user level is adversely affected. Conventional trafficshaping is basically a conservative approach to the congestion control. Withconventional traffic shaping cell loss will be reduced but at the cost of extradelay at the shaper. Conventional traffic shaping reduces, the bufferrequirements at the switches with the provision of an, input buffer at theshaper., This thesis also studies the effects of a new proposed adaptive-ratetraffic shapingmodel. Simulation’ shows that shaping decreases the delayfrom the user leveipersp~cti.ve, maximizes the utilization of the switch