On the efficacy of GMPLS auto-reprovisioning as a mesh-network restoration mechanism

GMPLS provides standardized protocols through which nodes can request and establish (or release) lightpaths on demand between themselves and peer nodes. The primary intent is to support automated provisioning for dynamic demand environments. However, an apparently tempting assumption is that GMPLS also provides a mechanism for physical layer network restoration, wherein all effected node pairs "simply redial their connections" - simultaneously. We argue from basic considerations, and illustrate with experimental results, that this is an oversimplified view. It assumes that the problem of replacing a failed path is the same when the path fails in isolation and when numerous paths fail together from a cable cut. Without some form of preplanning, or overall coordination of the multiple simultaneous reprovisioning attempts in the latter case, no guarantees are possible about the overall extent or pattern of recovery level. Capacity over-provisioning can mitigate the risk, but may involve almost as much overprovisioning as would suffice for simple 1+1 signal duplication in the first place, which defeats one of the main aims (efficiency) of a mesh-oriented scheme.