Multi-layer protection in IP-over-WDM networks with and with no backup lightpath sharing

Abstract

We consider the problem of multi-layer protection in IP-over-WDM networks. In our multi-layer protection schemes, traffic is protected either at the lightpath level or at the label switched path (LSP) level based on the restoration time requirements. In lightpath-level protection, traffic on a path (LSP) is protected by routing it over primary lightpaths which are protected at the optical layer by their respective backup lightpaths. In LSP-level protection, the traffic on a primary LSP is protected at the IP-multi-protocol label switching (MPLS) layer by a backup LSP. In this case, both primary and backup LSPs traverse unprotected lightpaths. We allow two backup LSPs to share bandwidth resource on these unprotected lightpaths if their primary LSPs are link-disjoint. In lightpath-level protection, whether backup resources can be shared or not depends on the protection mechanisms used. In 1:1 dedicated protection where the backup lightpath is pre-configured at the time of setting up of the corresponding primary lightpath, sharing is not possible. However, sharing is allowed in shared protection where the backup lightpaths are configured only after failure. We consider these two schemes and refer them as multi-layer protection with no backup lightpath sharing (MLP-NLS) and multi-layer protection with backup lightpath sharing (MLP-LS). An inter-level sharing (ILS) method is proposed to improve resource utilization in MLP-NLS, by allowing dedicated backup lightpaths to be used by backup LSPs. Two integrated-routing algorithms are developed to select paths in lightpath-level protection and LSP-level protection with the objective to utilize the network resources efficiently. We verify the effectiveness of the proposed multi-layer protection schemes through simulation results on the NSFNET and Pan-European networks. © 2005 Elsevier B.V. All rights reserved.