Survivability schemes for optical backbone and access networks

Network survivability, reflecting the ability of a network to maintain an acceptable level of service during and after failures, is an important requirement for WDM optical networks due to the ultrahigh capacity. The most common network failure is the link failure which could cause enormous data loss and lots of service disruption to Internet users. Although single-link failures are the most common failure scenarios, double-link failures can occur in some cases and cause more severe problem. Compared to unicast sessions, multicast sessions suffer more seriously from link failures because a link may carry traffic to multiple destinations rather than to a single destination. Hence, multicast sessions demand more effective and efficient protection against link failures. With the increasing demand for access bandwidth, the access networks draw more attention. The hybrid wireless-optical broadbandaccess network (WOBAN) is a promising architecture for future access networks because it combines the high capacity of optical communication and the flexibility and cost-effectiveness of a wireless network. First, we consider the problem of protecting unicast connections against double link failures. The basic idea is to use two p-Cycles, with link-disjoint protection segments, to protect each working link. To utilize spare capacity more efficiently, we also propose a new hybrid protection/restoration scheme to handle two-link failures. Our scheme uses protection to ensure that most of the affected demands can be restored using the pre-planned backup paths upon a two-link failure. For the demands not restorable with protection, we use dynamic restoration to find new backup paths for them. Second, we propose protection schemes for multicast sessions under one link failure. An intelligent p-Cycle (IpC) scheme is presented to provide p-Cycle protection for dynamic multicast sessions. When a multicast request arrives, a multicast tree is computed for it and then the IpC scheme is used to compute a set of high efficient p-Cycles on-demand to protect each link on the multicast tree. Then we