A DOWNSTREAM REQUEST FIRST QUEUING PROTOCOL FOR DUAL BUS MAN

摘要

The existing packet switching protocol used in the IEEE 802.6 distributed queue dual bus metropolitan area network is in favor of the upstream stations because the reservation requests of downstream stations will be delayed for the propagation time. This results in unfairness that the upstream stations have lower access delay than the downstream ones. With growth of the bus length, speed,number of stations, or network load,the unfairness will become more considerable. A downstream request first queuing protocol is proposed in this paper, which will allow a certain number of requests from downstream stations to queue ahead during a packet is waiting for access. This will reduce the effect of the request propagation delay and achieve lower difference of access delay between the up and down stream stations. Simulation results show that the performance is independent of the network size and network load.