Routing Technology Research In The Futureoptical Transport Network

With the development of the large scale multi-layer and multi-domain optical network, the calculation based on constraint optimal route, between multi-layers and multi-domains become difficult. E-NNI interfaces that have been reported have inevitable limitations for solving topology information diffusion of large-scale optical network. E-NNI interfaces do not adapt to the routing calculation between the multi-layer and multi-domain. PCE (Path Computation Element), reported by IETF Group, has effectively solved this issue.PCE is the functional entity that is based on Network topology and calculates network path with constraint conditions. As a relatively independent function entity, with flexible system structures, PCE can be embedded in the control plane, and can be used as a focus on the server fusion to intelligence network. PCE can realize end-to-end path calculation between many different kinds of network environment. If PCF structure is introduced into the ASON control plane, it will be helpful to slove the end-to-end path calculation issue in the multiple domain environments. PCE obtains flexible system structures, including the different structures, different calculation models, the traffic engineering database (TED) synchronicity, discovery mechanism and strategy and PCEP. Based on this, in the multi-domain optical network, PCF further studies domain flow equilibrium solutions, domain routing concussion inhibit strategy, multi-domain network routing forwarding node light quick optimization algorithm, and realize real-time monitoring of performance in the physical layer, electrical layer and signal transmission layer. This paper introduces the basic framework of RFC4655 PCE agreement, RFC5400 PCEP communication protocol and the calculation of RFC5441 BRPC domain traffic engineering label switching path. PCE can be used in the future optical transmission network, and we discuss the path calculation between single-domain and multi-domain.The second chapter mainly studies PCE (Path Computation Element). PCE system structure characteristics include:PCE is compatible with existing MPLS/GMPLS agreement. PCE is compatible with existing MPLS/GMPLS network operation mode, including management level. PCE uses a single, signaling protocol and structure, suitable for different network environment, such as inner domain, between domains, and between different operators, etc. PCE allows operators or equipment manufacturers use different routing algorithms, based on complex traffic engineering parameters and strategy calculation routing; and has the flexible system structures.PCE can work with nets element equipment together, also can be in a single server implementation.The third chapter studies the communication protocol (PCEP) between path computation elements. When the PCC and the PCE is not in the same physical location, it will need communication protocol to realize multi-domain path requests and path calculation.The fourth chapter studies routing applications of the PCE optical network. PCE-based network architecture and routing technology can make the path computation and traffic engineering, which is under the complex constraint conditions, independent from the traditional control plane. As a function entity responsible for path computation the network, PCE that is based on the known network topology and constraints, according to the path computation client (PCC) of the request, will calculate the best path.The fifth chapter studies the simulation of PCE optical networks. The use of Automatic Switched Optical Network (ASON) in the traditional methods can not effectively solve the large-scale multi-layer multi-domain optical networks, especially under conditions of multiple constraints routing problem. The based on PCE from the destination node reverse back to the source node constrained shortest path tree calculation, thus providing an effective inter-domain traffic engineering label-switched path.