Let us consider a client/server system where a server station receives requests from client stations, processes the request and replies to the client station. The i-th client-station generates requests following an exponential distribution with rate λi and the transmission time of the request to the server is also exponentially distributed with parameter µi . Other times, all assumed exponentially distributed, are: the time to process a request from the i-th client (rate ηi), and the reply transmission time (rate β for all the clients).