A PERFORMANCE ANALYSIS OF BUFFERED DQDB NETWORK WITH REQUEST ARRIVAL PROCESS DEPENDING ON ITS REQUEST COUNTER VALUE AND ITS LOCATION ON THEBUSES

The location of stations on the buses can not be ignored in the analys is of the DQDB protocol, especially when traffic load is heavy. In thi s paper, we propose a new method to model the DQDB (Distributed Queue Dual Bus) protocol by assuming that the request arrival process depend s on both the value of the request counter and the location of a stati on on the buses. By taking these dependences, we can catch the real be havior of the DQDB stations. which is locationally dependent and unfai r under heavy load traffic. Based on this model, we analyze the DQDB s ystem with finite buffer by considering the request counter states and buffer states separately and obtain the throughput, mean packet delay and packet reject probability of individual stations. The throughput in individual stations matches that of simulation very well within the range of traffic up to the channel capacity. Also the delay and packe t reject rate performance is good up to moderate traffic load. These n umerical results reveal the properties of the location dependence and the unfairness of DQDB system under heavy load condition. The analytic results under heavy load traffic for a general DQDB system has not be en reported till now. Therefore we conclude that our model and analysi s are valid and effective.