The Effects of Random Message Sizes on the Performance of the CSMA/CD Protocol

We present a performance model of the carrier-sense multiple-access protocol with collision detection when each message consists of a geometrically distributed number of packets. We solve the model analytically and present numerical evidence that throughput degrades slightly when the mean number of packets per message is increased and the load is kept constant. The numerical examples indicate that the average response time of a message is approximately proportional to the average number of packets per message. We also derive a general relation between throughput and average response time that provides a theoretical explanation of these results.