DCP: A Distributed-Control Polling MAC Protocol: Specifications and Comparison with DQDB

This paper describes and analyzes a novel MAC protocol named distributed-control polling (DCP), which has been designed to bring together the most interesting features of distributed-control MAC protocols (e.g., DQDB) and centralized token-passing MAC protocols (e.g. , FASNET, FDDI, EXPRESS-NET). From the fully distributed MAC protocols, DCP acquires the capability to guarantee both a complete utilization of the medium capacity and an access delay of only a few slots at light loads. From the centralized token-passing MAC protocols, DCP inherits a more predictable and fair behavior at heavy loads. The basic ideas of our proposal are: a cycle for acquiring transmission rights and a balancing function between reservations and empty slots. The analysis reported in this paper shows that DCP guarantees a complete utilization of the medium capacity and its behavior at light loads is close to that of DQDB, while at heavy loads it approaches a polling system with limited service and zero reply interval.