In order to provide reliable connections across metropolitan and wide-area optical networks, the network operator must provide some degree of redundancy so that traffic can be switched from damaged working paths to backup paths that are disjoint from the working paths that they are protecting. In the most general form of path protection, N working paths between two client edge nodes are protected by M backup paths. The set of working and protection paths forms a M:N protection group. In the near future, optical transport networks (OTNs) will use an automated control plane to set up, tear down, or modify connections between client edge nodes. If protection groups are allowed to evolve over time, with working and backup paths being set up or torn down individually, it may be necessary to modify other working and backup paths in addition to those that are being created or destroyed, in order to maximize network utilization. In this paper, we examine the mechanisms that can support adaptive M:N protection group management and describe how existing Generalized Multi-Protocol Label Switching (GMPLS) signaling protocols allow this capability to be deployed in the OTN.
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