Engineering VBR Traffic Parameters for WAN Voice

Asynchronous Transfer Mode (ATM) supports a number of different traffic classes, including Constant Bit Rate (CBR), Available Bit Rate (ABR), and Variable Bit Rate (VBR). Applications wishing to use a particular class must determine the set of traffic parameters which characterize the connection. In this paper, we consider how to engineer the traffic parameters for VBR WAN voice, where multiple voice streams, utilizing compression and silence detection, are multiplexed into a single virtual circuit. We define two criteria which the VBR parameters must satisfy: 1) Achievement of a desired probability of cell marking/loss by a leaky bucket policer, and 2) Maximization of admission probabilities to the network. We compute the parameters for two vastly different systems and admission controllers. In either case, we observe a similar trend in the admission probabilities, and propose a method for choosing specific values of the VBR parameters.