PROTECTORATION: A Fast and Efficient Multiple-Failure Recovery Technique for Resilient Packet Ring (RPR) Using Dark Fiber

The two protection methods, wrapping and steering, used in the IEEE 802.17 Resilient Packet Ring (RPR) provide fast but very inefficient and limited network failure recovery. Due to the increased length of the backup path, RPR suffers from high traffic loss, a decreased throughput-delay performance, and the lack of resilience against multiple link and/or node failures. To achieve an improved resilience we propose to interconnect a subset of the ring nodes by means of a dark-fiber single-hop star wavelength division multiplexing (WDM) network. In doing so, the ring network is divided into separate domains, each being fully recoverable from a single link or node failure without losing full network connectivity. We propose and examine by means of probabilistric analysis and simulation a novel hybrid fault recovery technique, termed protectoration, in terms of stability and throughput-delay performance. The proposed protectoration technique (i) combines the fast recovery time of protection and the bandwidth efficiency of restoration, (ii) provides full recovery from multiple link and node failures, (iii) builds on both wrapping and steering protection methods of RPR and thus allows for an evolutionary upgrade of existing RPR networkds, and (iv) does not require the convergence of routing protocols in response to failures and thus improves the routing stability and network availability. Our numerical investigations show that the location of failures has a strong impact on the network performance. For a given failure location, the protectoration technique is able to accommodate multiple ring failures without significant performance loss.