Failure-independent path-protecting p-cycles: efficient and simple fully preconnected optical-path protection

Abstract

We propose a new technique for optical-network protection called failure-independent path-protecting (FIPP) p-cycles. The method is based on an extension of p-cycle concepts to retain the property of full preconnection of protection paths, while adding the property of end-to-end failure-independent path-protection switching against either span or node failures. An issue with applying the popular method of shared-backup path protection (SBPP) to an optical network is that spare channels for the backup path must be cross connected on the fly upon failure. It takes time and signaling to make the required cross connections, but more importantly, until all connections are made, it is not actually known if the backup optical path will have adequate transmission integrity. Thus, speed and optical-path integrity are important reasons to try to have backup paths fully preconnected before failure. With fully preconnected protection, not only can very fast restoration be attained, but the optical-path engineering can also be assured prior to failure. Regular p-cycles are fully preconnected, but are not end-to-end path-protecting structures. SBPP is capacity efficient and failure independent-failures only need to be detected at the end nodes and the end nodes activate and switch over to one predefined backup route for each working path-but the backup paths are not preconnected. FIPP p-cycles support the same failure-independent end-node-activated switching of SBPP, but with the fully preconnected protection-path property of p-cycles. As a fully preconnected and path-oriented scheme, FIPP p-cycles are, therefore, potentially more attractive for optical networks than SBPP. Results confirm that FIPP p-cycle network designs will exhibit capacity efficiency that is characteristic of path-oriented schemes and may be as capacity efficient as SBPP, but more conclusive comparisons on larger scale networks await further study.