An access protection solution for heavy load unfairness in DQDB

The authors discuss the unfairness issue arising in a 802.6 distributed queue dual bus (DQDB) network at heavy loads. Based on the 802.6 protocol, the end-nodes along a bus experience longer delays than the other nodes. The origin and remedy for this heavy load unfairness problem are discussed. An access control scheme is proposed as a solution. A comparison of the proposed scheme with the 802.6 protocol is presented. The simulation results and performance characteristics are discussed under several types of loads. With symmetric load conditions under the proposed scheme, all active nodes along a bus experience almost the same access delay and packet loss characteristics. The performance under several other load conditions was also found to be satisfactory