A single-fault recovery strategy for optical networks using subgraph routing

The data transmission potential inherent in optical networks is enormous, and because of this great potential, optical networks are in dire need of fault toleration. Recently, various fault toleration techniques exploiting the special properties of optical data transmission have been presented, one of the most interesting being backup-multiplexing. Backup multiplexing comes in a couple of different flavors, but it basically enables connections to be backed up by allocating system resources for fault recovery upon the occurrence of a single fault in a network. Backup-multiplexing attempts to limit the amount of system resources it utilizes up by allowing backup connections to share a particular wavelength, given that their associated primary paths are link disjoint. This way, in the event of a link failure, each primary routed on that link can be assured of finding an available backup connection. Backup multiplexing is certainly a viable form of fault toleration, but is there another way of assuring that a network can recover from a link failure, while not tying up valuable system resources in backup connection allocation? The goal of this research is to present an alternative method, known as L+1 fault tolerance, and to compare the performance of that alternative to that of the backup multiplexing strategy. Each network has a set of subgraphs associated with it such that one of the links in the original network is removed. Connections in the newly proposed strategy are accepted if they can be routed in all of the subgraphs. That way, in the event of a link failure, the network state can be restored to that of the corresponding subgraph, where all connections are guaranteed restoration.