Performance analysis of a buffered CSMA/CD system

Abstract

AbstractMost of the performance analyses of CSMA/CD systems have assumed that each user has a buffer space for only one packet. Using the technique of equilibrium point analysis, this paper analyzes the dynamic behavior of a slotted nonpersistent CSMA/CD system with a finite number of users, each of whom has a finite buffer space for more than one packet. Two schemes of packet transmission are studied: (1) once a user captures the channel, he continuously transmits all of the packets which have been stored in his buffer by the instant of the capture (gating type); and (2)he transmits at most one packet at a time (limiting type). First the gating type is analyzed, and its throughput, its average packet delay and its system stability are evaluated. An approximate probability distribution for the number of packets in the buffer space of a user is derived. On the basis of these analytic results, we study how to select both the buffer size and the rescheduling probability of packets which guarantee the system stability, keep the probability of buffer overflow sufficiently small and at the same time minimize the average packet delay. The two schemes are compared and it is shown that the gating scheme out performs the limiting scheme in terms of average packet delay and the average and variance for the number of packets in a buffer.