A Hop to Hop Controlled Hierarchical Multicast Congestion Control Mechanism

摘要

Hierarchical multicast can effectively achieve multicast communica tion of heterogeneous network. RED algorithm and HTH algorithm were ana lyzed and discussed. RED can keep low delay while pursuit larger throughput, but it has shortcoming of sensitive to parameters. HTH algorithm can rapidly respond to congestion and effectively improve throughput as well as utilization of link, but it occupies too much router resources in case of many streams. On the basis, a kind of hop-to-hop controlled hierarchical multicast congestion con trol mechanism combining RED and HTH was presented. With this mechanism, each router determines its congestion status based on current network state. If congestion occurs, it discards with certain probability and report congestion sta tus to upstream router. After router received congestion state from other routers, it will take appropriate measures to increase or decrease transmission rate to some downstream router. At the same time, packet discard number of each link was considered in congestion control to ensure fairness. Simulation result based on NS-2 shows that the proposed algorithm is superior to RED in aspects of throughput and packet loss rate.