Abstract

Introduction A generalized optical network consists of multiple optical cross-connects OXC that are interconnected via bi-directional WDM links in a general topology, often referred to as intelligent optical mesh network. A major aspect of this intelligence is the ability to provide fast provisioning and restoration. To achieve this, there is a need for a unified control plane responsible for running routing and traffic engineering protocols, achieved, for example, through the introduction of GMPLS. The control plane queries and modifies the wavelength-switching table of the cross-connect; floods the reservation tables of the cross-connect (through OSPF or IS-IS) in the network; is responsible for connection setup/tear-down through CR-LDP (or RSVP-TE). A mesh-restored lightpath in an optical network is allocated a pair of link-disjoint paths, where one of the path is the primary or working path and the other is backup or protection path that is activated only in case of failure. Each link in the primary path has dedicated capacity allocated to a connection. The protection path can also have dedicated capacity (1 + 1 restored lightpath), however that results in inefficient use of network capacity. In contrast, in shared or 1:N restored lightpath, the protection capacity is shared with the backup path for other restored connections, hence resulting in improved utilization of the network resources.² Shared route computation can proceed through centralized network management system that results in good network uti-lization but does not scale well with network size, can be a single point of failure and is rather slow for dynamic applications. An alternative is the distributed computation with a use of a database at every OXC, where a decision on sharing is being done locally on a link-by-link basis. The distributed approach provides better scalability, resilience and speed, but results in sub-optimal sharing and hence utilization of network capacity. In this paper we propose a novel distributed approach, called Informed Dynamic Shared Path Protection (IDSPP), where information about the shared resources on every link is distributed throughout the network using extensions to OSPF (or IS-IS), resulting in much better sharing. Simulation results indicate substantial improvement over the uninformed (1:N) approach. ThO4 Fig. 1. Protection sharing table.

© 2002 Optical Society of America