A Distributed Bandwidth Sharing Heuristic for Backup LSP Computation

With the advent of MPLS, the restoration times of communications is decreased down to 50 ms by the use of preconfigured backup LSPs. To ensure there are enough resources after a failure, the backup LSPs must reserve the resources they need beforehand. However and contrarily to the primary LSPs which really use their resources, the backup LSPs do not use them until a failure of the protected component occurs. Hence, to optimize and maximize resource availability in the network, backup LSPs may share their resource reservation. Indeed, under the hypothesis of single failures in the network, some backup paths are not active at the same time since they protect against the failure of different components. In this article, we propose an efficient Distributed Bandwidth Sharing (DBS) heuristic capable to protect the primary LSPs against all types of failure risks (link, node and SRLG risks) with the transmission of a very small amount of bandwidth information. Our technique is completely distributed; it balances the computations on the different nodes of the topology and is easy to be deployed. Simulations show that with the transmission of a small vector of bandwidth information per link, the rate of rejected backup LSPs is low and close to the ideal.