Static Multithreshold Rate Control Mechanisms in Doubly Finite Queue for Supporting Abr Traffic in Atm Networks

This paper is concerned with the variety of ABR switch mechanisms available for implementation with the current end system definition. The various switch mechanisms can be broadly classified in two categories depending on the type of feedback information provided to the end system. The feedback mechanism is either binary involving setting the EFCI bit in the data cell header or explicit rate in which case the switch has to calculate a target rate and send it back to the source through an RM cell. Also within each category, different subgroups are formed based on the type of queuing involved (for example per port queuing, per VC accounting, per VC queuing) and the congestion declaration criteria adopted (for example queue thresholding, queue derivative, load monitoring). Our goal is to provide an overview of the various switch mechanisms available and discuss their performance characteristics accordingly. The performance metrics used include queue length, source flow-controlled cell rate dynamics, fairness of bandwidth allocation in the steady state and ramp-up time in the network transient state. Simulations of the different switch algorithms’ dynamics for network configurations and scenarios of interest are presented. Each link is assigned a weight that reflects its current utilization. Using these weights, the VPs on highly utilized links are rerouted to less congested physical paths. The algorithm makes use of the equivalent bandwidth concept, which provides an efficient method to estimate capacity requirements of connection requests such that QoS requirements are met. The quality of the solutions achieved by the proposed method is compared to several competitors under varying network topologies and traffic conditions. The observations on the algorithm performance show that the developed method is able to facilitate an efficient use of network resources through the introduction of VPs