Research On Multiconstraint Multicast Routing Algorithm In Application-level Network

As the development of computer network technology and multimedia technology, Internet is becoming important carrier of many real-time multimedia applications, such as the audio/video conferencing, on-line live broadcasting and multiparty games. These applications which need high bandwidth and low latency put forward exigent requirement on group communication. Because of some technology and economy issues, IP multicast service among the whole network haven't been deployed completely. Under the circumstance that IP multicast cannot satisfy these application requirement, researchers begin to consider utilizing network resources of Internet end user to provide multicast service directly in the application level, therefore, the notion of application-level multicast has been put forward.The idea of application-level multicast service is that all multicast functions are implemented in end hosts instead of routers. The primary advantage is that IP network architecture need not to be changed, support of lower level network is not required and the deployment is simple. Application-level multicast routing is different from traditional IP multicast routing. The application-level network is a virtual logic network, its routing differs from the network in lower level, thus may result in the latency increasing and resource wasting of the application-level multicast. Because of the limited transmitting capability of the end hosts, limited degree is introduced. How to provide effective multicast and design good multicast routing algorithm are the key points of the application-level multicast research, and also the focus of this paper.First, this paper analyzes degree-constraint minimum diameter spanning tree algorithm– the CT algorithm, and proposes the improved CT algorithm. In the process of constructing multicast tree, the new algorithm considers the balanceable distribution of node degree which the CT algorithm doesn't take into consideration. By using strategy function, this algorithm iteratively chooses the path which makes diameter of the spanning tree the shortest, thus decreases the transmitting latency of the network and the number of repeated grouping in the same link path. At the mean time, it uses the topology optimization strategy to get the optimal multicast tree. Experiments show that this algorithm has reached the demand of degree balance and kept the performance of time delay.Then, in the real-time multimedia application, the receiver request that information should be arrived within one delay in order to guarantee the quality of service. Thus, the delay-limtied application-level multicast routing problem is introduced. Aiming at this problem, this paper proposes an efficient algorithm - the TS-LDRB algorithm based on Tabu Search. This algorithm makes use of the Tabu Search to search for the multicast spanning tree which satisfies the delay restriction and analyzes the characteristic of this method.