Research On The Algorithm For Distributed QoS Multicast Routing With Uncertain Condition

At present, the increase of network bandwidth and processing power makes the network provide more multimedia applications, and also makes the multicast communication that supports "one-to-many" or "many-to-many" become a necessary mode of multimedia services. A fundamental issue in multicast communication is how to determine an efficient multicast routing, and finding simple, effective and robust multicast routing algorithms is unsolved problem in network fields. In addition, many distributed multimedia applications have various demands on delay, delay variation, bandwidth and packet loss, which requires current network to transmit real-time multimedia information with these quality-of-service (QoS) constraints. So, as an indispensable component in a QoS-centric network architecture, research on multicast routing algorithms based on QoS constraint becomes an important part and hotspot issue of network research fields.Most of the routing algorithm has been published has assumed that each node in the network can access and maintain the accurate state of the network through distance vector protocol or link state protocol. However, in the actual dynamic network environment, the state of the network which the nodes can access is not accurate. This non-accuracy of the information of the network seriously affected the performance of routing algorithm.This paper briefly introduced some sources of non-accuracy of the state information of the network, simply list and analyzed the characteristics of the centralized routing algorithm and distributed routing algorithm; Then made a detailed analysis for DiffServ architecture and the principle and theory of QoS routing. And put forward a mathematical model for the algorithm of QoS multicast routing in DiffServ networks; Then expatiate the characteristics of source routing and distributed routing in general. Later we enumerate and analyze several distributed QoS routing in great details. After finding defects of these algorithms, we proposed a new ticket-based multi-path distributed QoS routing algorithm named R-DQMR to improve the network performance can also reduce the impact of non-accuracy on the routing algorithm. In the algorithm, every node only need to maintain local state information of its links, ticket is used to decrease the extension of flooding, while mufti-path can increase the probability of finding the feasible paths. We used the method of "soft-state" to eliminate the impact of dynamic change of resource information. The innovation is that we analyzed the characteristics of multicast routing in DiffServ networks under uncertain condition, and solved the problem of "over-reservation". R-DQMR can eliminated the impact of dynamic change of resource information, so that improved the success ratio. In the end, we realized R-DQMR in virtual network environment which established with C language. Simulation results revealed that R-DQMR improved the success ratio, optimized the average cost and added length of per established path.