Center placement algorithms for large multicast groups

An increasing number of distributed applications require a speci c form of multicast called dissemination, in which a single source reliably transfers data to multiple receivers. Reliability requires that data packets are acknowledged positively or negatively, which leads for large groups of receivers (100s or 1000s of participants) to the problem of feedback implosion. Among the approaches trying to avoid feedback implosion, the cluster approach is the most promising. It partitions the multicast delivery tree into clusters. Each cluster has a representative called center, which is used for acknowledgment accumulation and local retransmission. Up to now, clustering/center placement has been done administratively or based on network addresses. Needed are center placement algorithms, allowing the introduction of placement criteria based on the network topology and on delay. In this work, three center placement algorithms designed for static multicast groups are presented and simulation results are shown in order to asses their performance.