A Distributed Bandwidth Sharing Heuristic for Backup LSP Computation

Abstract

Abstract-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.

Using Shared Risk Link Groups to enhance backup path computation

“…With the increasing interest for local proactive protection in the last decade, several works [1,2,9,6,10,11,7,12,13] have been devoted to the determination of algorithms computing the backup paths. To minimize the quantity of bandwidth allocated on links while avoiding the bandwidth constraint violation (bandwidth insufficiency), the Backup Path Computation (BPC) algorithms require the knowledge of some information like the primary and backup paths, bandwidth allocations and protected risks.…”

“…to guarantee the communication repair success), the backup paths should reserve the bandwidth they need beforehand. Besides, to decrease the bandwidth allocations and accept much more connection establishments, the practical hypothesis of single failure is often adopted [9,6,10,11,7,12,13]. With such hypothesis, all the backup paths protecting against failures of different components can share their bandwidth allocations (on their common links) since they cannot be active at the same time.…”

“…Finally, the third type of risk corresponds to a set of logical links that share a common physical component (optical fiber, crossconnect, etc.) whose failure may impact all links in the set [5][6][7].…”

“…Several classical approaches [9,6,10,11,7,12,13] are developed to optimize the band-width allocated to the backup paths (called also protection bandwidth). In such approaches, the authors suggest to determine the cumulative bandwidth of the backup paths which would be activated on each link, after each possible failure.…”

Distributed PLR-Based Backup Path Computation in MPLS Networks

“…To offer scalability without increasing the recovery cycle, new computation heuristics which approximate and reduce the bandwidth information (protection costs especially) transmitted in the network have emerged [7,9]. Hence, once the bandwidth information is collected, nodes aggregate it before its flooding in the network.…”