Distributed, IP-based control architecture has been proposed for switched optical mesh networks, as a means to automate operations, enhance interoperability and facilitate the deployment of new applications. While distributed control in general enhances scalability and flexibility, it also offers challenges to path computation, especially for shared mesh restored paths, because of the summarization of link state information disseminated by the routing protocol. This paper discusses the tradeoffs between the path computation efficiency and the abstraction level of link state information. Several heuristic algorithms for computing shared mesh restored paths are described, which require different levels of abstraction and summarization of link resource sharing information. The performance of these algorithms is compared in term of the efficiency of network capacity utilization, the computation complexity, and the amount of required network information. We show that with appropriately aggregated link state information the proposed path computation algorithms are able to utilize the network resource very efficiently.

Efficient methods are needed to aggregate and disseminate the routing information, including the optical link resource availability and sharing, so that the amount advertised by the routing protocol is minimized and the information necessary for path computation is not lost. In this paper, the author proposed to extend the generalized multi-protocol label switching (GMPLS) OSPF-TE routing protocol to carry the necessary sharing information of the reserved resource on a TE link in support of computing the shared mesh restored paths. It is based on the OSPF routing extensions required to support traffic engineering (TE) and GMPLS. New optional sub-TLVs (type/length/value) are added to the link TLV of the TE link state advertisements (LSA) so that the sharing information of the restoration resource is disseminated.

Optical mesh network infrastructure has emerged as the technology of choice for next-generation transport networks. At the same time, distributed, IP-based, control architecture has been proposed for intelligent optical networks, as a means to automate operations, enhance interoperability, and facilitate the deployment of new applications. While distributed control in general enhances scalability and flexibility, it has also been observed that the requisite network topology and link-state information summarization may result in suboptimal path computation, especially for shared mesh restored paths. This paper presents a distributed control plane for optical mesh networks, focusing on distributed path computation and provisioning mechanisms. It discusses the tradeoffs between the path computation efficiency for shared mesh restored paths and the amount of network topology and link-state information that is disseminated via routing protocols. We show that with appropriately aggregated link resource availability and sharing information, the proposed distributed path computation algorithms are able to determine the shareability of restoration links with remarkable accuracy. A local channel assignment scheme, which is used in conjunction with the distributed path computation algorithms to assign shared channels when provisioning restoration paths, is also proposed. The additional information that signaling messages are required to carry in order to perform the local channel assignment at each node along the restoration path is discussed. Furthermore, we specify the extensions to the open shortest-path first (OSPF) routing protocol in support of shared mesh restoration. We analyze the performance of the proposed distributed path computation algorithms and the local channel assignment scheme, as well as the overhead of OSPF extensions. In particular, we study the tradeoffs between network capacity utilization, restoration path computation complexity, OSPF extension overhead, and memory requirements for storing the modified link-state database.