Flow control in local area networks and high-speed networks

Kent H Tseng, Purdue University

Abstract

The modeling and optimal arrival rate control for Carrier Sense Multiple Access/Collision Detection (CSMA/CD) and Token Ring local area networks and admission control in Asynchronous Transfer Mode (ATM) high speed networks are studied in this thesis. To investigate the optimal arrival rate control of a typical user for CSMA/CD networks, the optimality criterion of maximizing the average individual throughput subject to an average individual time delay constraint is adopted. Two cases have been studied: (1) the local control (the controller has local information), and (2) the global control (the controller has global information). Under two reasonable approximations, a window type mechanism is shown to be the optimal local control. On the other hand, the optimal global control is found to be an 'almost' Bang-Bang control. For Token Ring networks, the optimality criterion is to maximize the average network throughput subject to a bounded average network time delay constraint. We assume that the network consists of two stations and both station controllers have global information. The optimality problem is formulated using dynamic programming (DP) with a convex cost function. Combining with duality theory, we then show that the optimal arrival rate control for both stations is 'almost' Bang-Bang. In the special case when both buffers are sufficiently large and have the same service rate, the optimal control is further shown to be switchover. Since an M/G/1 queue with state-dependent arrival rates and finite waiting room (size N) is a useful tool for analyzing arrival rate control problems, its asymptotic behavior and optimal control are explored. Using a modified Takacs equation, the waiting time distribution is found by first obtaining the steady state probabilities using the supplementary variable method. Under the optimality criterion that maximizes the average throughput subject to a bounded average time delay, the optimal arrival rate control of the queueing system for N = 1,2, is solved. For ATM networks, suitable voice traffic characterization and a two-queue model with voice/data integrated traffic are proposed. Voice is given a higher priority than data traffic, which is a combination of single cells (packets) and bursts. Assuming a finite voice queue, both cases of finite and infinite data queue are analyzed. The performance measures, average waiting times and blocking probabilities, are derived. Finally, the effect of the number of accepted calls on the performance measures is also portrayed.

Degree

Ph.D.

Advisors

Hsiao, Purdue University.

Subject Area

Electrical engineering

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