As an alternative to the shared backup path protection (SBPP) method, we develop a framework for dynamic provisioning of survivable services through the use of p-cycles to form a protected working capacity envelope (PWCE) within which dynamic provisioning of protected services is greatly simplified. With a PWCE, arbitrarily fast dynamic service demands can be handled with much less complexity (in terms of database maintenance and state update dissemination) than with SBPP. Only a simple open-shortest-path-first (OSPF) topology view of nonexhausted spans in the envelope is required. If a new path can be routed through the envelope, it is protected by virtue of being routable. This is in contrast to needing a full database of the network state so that the end user can set up a shared backup protection path under SBPP. In addition, dissemination of spare capacity sharing updates occurs only on the time scale of the nonstationary evolution of the demand statistics, not like SBPP, which occurs on the time scale of individual connection arrivals or departures. During statistically stationary periods there is no dissemination of spare capacity sharing updates whatsoever with an envelope that is well matched to its load. The PWCE concept thus offers some new trade-offs between operational simplicity and spare capacity efficiency. Under the PWCE concept p-cycles are of particular interest for consideration because, although many protection techniques can be the basis of PWCE operation p-cycles offer the unique combination of ring-like protection times with the capacity efficiency of shared-mesh networks. But, in addition, p-cycles offer a further important property for a transparent optical network: that of providing fully pre-cross-connected protection paths. Because all protection paths are preconnected structures, optical transmission path integrity can be validated before failure and is not of such concern as it is in schemes where optical replacement path segments of several wavelength channels would have to be assembled on the fly (without the benefit of o-e-o between stages). The main contribution of this work is the detailed implementation and simulation of test networks operating under PWCE and designed with novel envelope volume maximizing formulations. A wide range of network capacity environments were considered to find that p-cycle-based PWCE is close to SBPP in blocking performance while simultaneously offering much simpler operation and a faster restoration speed.
© 2005 Optical Society of AmericaPDF Article