Testing PABXs and call centers under high load is of paramount importance because customers rely on these systems for safety and business critical applications. A traffic generator for high traffic volumes is presented in this paper. The two key characteristics of the traffic generator are the generation of traffic with configurable statistical properties and its flexibility in many aspects, ranging from the number and kind of emulated users to the user behaviour models and signalling protocols. This extraordinary flexibility could only be achieved by a pure software approach. The architecture clearly separates the basic runtime system and support functions which are implemented in the traffic generator core from user models and signalling protocols which the traffic generator reads and executes during tests.
ATM switches have to provide traffic management functions to meet the QoS requirements of different service categories. Among the traffic management functions we will focus on connection admission control (CAC) and priority control in this paper. Besides the mechanisms and algorithms behind these functions the issue of application to a concrete architecture of an ATM multi-service workgroup switch is emphasized.For CAC a new method is proposed that is based on a simple approximation of the effective bandwidth. The difficulties occurring if connections with different parameters are mixed together are solved by handling CBR traffic separately and dividing the parameter space for VBR connections into several regions. Within the VBR regions the linear method is applied while for connections associated to different regions a reduced service rate is considered.The performance of both the priority control mechanisms and the CAC method is evaluated using analysis and simulation.
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