CYCLE COMPENSATION PROTOCOL - A FAIR PROTOCOL FOR THE UNIDIRECTIONAL TWIN-BUS ARCHITECTURE

The IEEE 802.6 Standard-Distributed Queue Dual Bus (DQDB)1-for metropo litan area networks (MAN's) has been proposed. It is based on a unidir ectional twin bus architecture. The DQDB protocol lays more emphasis o n the overall channel utilization than the fair sharing of channel ban dwidth by all the stations. In this paper, we first describe the unfai rness problem in which the upstream stations occupy most of the channe l bandwidth while the downstream stations get fewer chances to transmi t their packets. Many.proposed possible fixes are also discussed. We p ropose a protocol called Cycle Compensation Protocol (CCP), which ensu res fairness regardless of the ratio of end-to-end propagation delay t o the slot size and also achieves almost the same throughput and delay as those of DQDB. CCP also guarantees that the channel bandwidth acqu ired by a station is inversely proportional to the number of busy stat ions and will reach this state within a limited time delay.