PRIORITY ACCESS SCHEMES USING CSMA-CD

Some CSMA-CD schemes for multiple priority message classes are suggested. For all the schemes, an approximate analytic technique for calculating the mean packet delay (for each priority) at the stable operating point of the system has been developed. The analytic results are tested against computer simulation. A Poisson packet arrival process and a general packet length distribution are considered. The mean packet retransmission delay is a general function of priority and the number of unsuccessful attempts. There is a variation in delay differences among priorities for the different schemes. This allows one to single out the particular scheme that is optimal for a given system delay requirement. Some of the priority schemes possess the desirable property of having less average delay compared to a corresponding nonpriority system.