A Novel Source Path Topology Map Construction Method in ALM

Abstract

Application Layer Multicast (ALM) systems can easily be deployed compared with IP multicast because they do not require any modification to the current Internet infrastructure. Topology-aware ALM systems make multicast forwarding path as far as possible to match the underlying physical paths. They can reduce redundant data packets and forwarding delay. So the source path topology map construction is more important in topology-ware ALM systems. We find that only the routers directly connecting to terminal nodes (usually as gateway) and their connection information are required to be added to the source path topology map. This kind of topology map is named as gateway-level map. In this paper, we first prove that for the same multicast members, the complete path-matching algorithm (based on the gateway-level topology map) generates the same multicast tree as the complete topology map. After that, we present a delay coarse-grained matching method to generate the gateway-level topology map. Furthermore, the paper discusses some details such as how to get the topology information, how to build the map, how to maintain map information, and so on. Finally, performance analysis and simulation experiments demonstrate the conclusion that the method not only simplifies the information required by topology construction, but also accelerates the speed of accessing topological information. The time of application layer multicast nodes joining the multicast tree is reduced. This method also provides users the higher quality of service.