Multicast Tree Diameter for Dynamic Distributed Interactive Applications
Knut-Helge Vik, Pål Halvorsen, Carsten Griwodz · 2008
Latency reduction in distributed interactive applications has been studied intensively. Such applications may have stringent latency requirements and dynamic user groups. We focus on using application-layer multicast with a centralized approach to the group management. The groups are organized in overlay networks that are created using graph algorithms. We investigate many spanning tree problems with particular focus on reducing the diameter of a tree, i.e., the maximum pairwise latency between users. In addition, we focus on reducing the time it takes to execute membership changes. In that context, we use core-selection heuristics to find well-placed group nodes, and edge-pruning algorithms to reduce the number of edges in an otherwise fully meshed overlay. Our edge-pruning algorithms strongly connect well-placed group nodes to the remaining group members, to create new and pruned group graphs, such that, when a tree algorithm is applied to a pruned group graph, it is manipulated into creating trees with a smaller diameter. We implemented and analyzed experimentally spanning-tree heuristics, core-selection heuristics and edge-pruning algorithms. We found that faster heuristics that do not explicitly optimize the diameter are able to compete with slower heuristics that do optimize it.