AbstractWhen different kinds of local area networks are interconnected, a gateway holds the key to better performance of the interconnected network. Since gateways are lia‐able to overflow easily because of their comparatively long processing time, it is necessary to estimate their appropriate buffer size with regard to the input traffic. This paper considers a local area network working under CSMA/CD protocol. First, we analyze the output process of messages which constitutes a part of arrival process at a gateway, by solving an embedded Markov chain. Second, two stochastic models of the gateway are formulated by queueing theory and loss probability of messages is evaluated in regard to its buffer size. Numerical results show some interesting features of the output and arrival processe