March 1996 LIDS - P - 2321 Full Utilization , Fairness and Bounded Access Delay on High Speed

Many existing protocols indicate that full utilization and fairness might be incompatible in high-speed-high-latency MANs or LANs. The purpose of this paper is to study the fundamental limitations of dual bus networks, in terms of full utilization, fairness and bounded access delay. A new protocol called FUFA (fully utilized and fair) is used to demonstrate some of these basic properties. We define full utilization, and fairness precisely, and show that both are achieved together in the FUFA protocol. In addition, the protocol provides bounded access delay that is linear in the round trip propagation delay, and at most a constant away from its minimum possible value for any bus protocol that is both fully utilized and fair. The main idea is to compute, for each station, the latest estimate on the number of active downstream stations, according to the information available, and serve them in a round robin scheme.