Performance analysis of CSMA/CD networks with a buffered gateway

A single CSMA/CD (carrier sense multiple access with collision detection) local area network which is connected to other networks by a gateway with finite buffer capacity is described. Its performance is analyzed by using an embedded Markov chain. For the service discipline of packets queuing at the gateway, three cases are considered: G-limited service discipline, E-limited service discipline, and G-decrementing service discipline. The state transition of the system is analyzed, and the Laplace-Stieltjes transforms of the probability distribution functions of idle and busy periods are derived. Equations for average performance measures are formulated. Numerical examples are used to examine the effect of external traffic on the packet delay and throughput at terminals as well as at the gateway for each service discipline. The results show that as a service discipline at the gateway, the limited service disciplines are preferable to the decrementing service discipline in that they more fairly allocate the channel bandwidth to terminals and the gateway. The numerical results also show that the performance of the gateway is substantially improved by using a higher retransmission rate at the gateway