Packet scheduling in input-queued switches with a speedup of less than two and scheduling algorithms for switches with a configuration overhead

Abstract

Input-queued switches and the solution of input/output contention by scheduling algorithms have been widely investigated. Most research has focused on switches for fixed-size packets. This contrasts with the variable size packets of IP networks. Previous research on fixed packet length has only focused on maximum weight matching algorithms. As maximum weight matching algorithms are computationally very complex, it is of interest to investigate less complex, but stable algorithms that take into account the variable packet size of data packets. In this paper, we investigate how the class of maximal matching algorithms deployed in switches with a speedup of less than two can be modified to take into account the varying packet sizes. Using a novel model for the dynamics of maximal matching algorithms, we show that modified maximal matching algorithms guarantee stability of the switch and establish bounds on the average delay experienced by a packet. In the second part of the paper, we apply the techniques developed for networks with variable packet size to the design of a scheduling algorithm for switches with large configuration overhead. We design a maximal weight matching algorithm for a switch with configuration overhead and determine the minimum speedup required to guarantee the stability of the switch.