Research On Dynamic-Risk-Disjoint Protection And Subtree Restoration Of Multicast Services In Optical Networks

With the development of the network convergence and the value-added services, to satisfy the customer demands, multicast services are becoming more and more prevalent, and so optical network need to support multicast services. For optical network multicast services, a single fault may cause loss of multiple connection. Hence survivability (Protection and Restoration) of multicast services in optical network carries great significance. In this thesis, the author did some research in this area.First, the protection of multicast services in optical network is researched. The current protection technology of optical network is introduced, and the research focuses on the influence of risk disjoint mechanism. The traditional complete risk disjoint mechanism and link disjoint mechanism are analyzed, and a new Dynamic Risk Disjoint (DRD) mechanism is proposed. Moreover, two protection algorithms based on DRD mechanism for multicast services in optical network are proposed, DRD based Tree Protection (DRD-TP) and DRD based Shared Link Protection (DRD-SLP). Simulation results and performance comparisons show that the new DRD-TP approach can reduce blocking probability compared with CRD-based schemes, and DRD-SLP performs excellently in backup resources sharing.Second, the restoration of multicast services in optical network is researched. A new SubTree Restoration (STP) algorithm is proposed. Using STP algorithm, the least cost paths between nodes are computed when computing the working tree, so the best backup path can be found as soon as the failure occurs. Unlike traditional link restoration, the restoration path is not between the nodes of the failure link. Instead, when the failure divided the working tree into two subtrees, the restoration path is the shortest path between the two subtrees. Simulation results show that the new STP approach can improve network resources utilization compared with CRD-based schemes, and can also reduce the restoration time.