Analysis of leaky bucket access control mechanism with batch arrival process

Abstract

A rate-based access control mechanism for high-speed networks, based on the buffered leaky bucket scheme, is studied. The study is carried out in discrete time and assumes an asynchronous transfer mode (ATM) environment, where only fixed size packets or cells are transmitted over the network. The leaky bucket scheme is based on the use of transmission tokens for each cell accessing the network. How often tokens are generated and the maximum number of tokens that can be accumulated are the parameters used to match the access control mechanism to the requirements of the cell arrivals patterns. Since cell arrivals often correspond to the segmentation of large user packets into many cells or to the superposition of a number of cells coming from different logical connections routed over the same path in the network, a batch arrival process is considered to represent such arrival patterns. With the batch arrival process the impact of other factors, such as burstiness of the sources and packet length variations, can be captured effectively. The distribution of batch sizes is arbitrary, while the time between arrivals of successive batches is taken to be geometrically distributed. Using matrix analytic techniques, the queue length distribution at the access point is obtained. A number of numerical examples that illustrate the influence of the different system parameters are provided.