On Joint Restoration of Packet-over-optical Networks

Recent advances in generalized multiprotocol label switching (GMPLS) [1,12] and the extensive study and understanding of packet-over-optical network architecture, has made it possible for a single integrated control plane to manage the resources of the packet network and underlying optical transport network in an unified manner. This opens up the possibility for coordinated actions across the two networking layers. In this paper, we propose and evaluate a joint protection/restoration scheme for a future packet-over-optical network. Since packet switch ports are typically more expensive than optical switch ports, the essence of the approach is to attempt to reuse packet service ports or the service wavelengths associated with optical switch ports for restoration rather than reserve additional standby packet ports exclusively for network recovery. This can be done when there are concerted actions between the packet and optical transport layers. In today’s telecommunication networks, optical transport layer failures such as cable or fiber cuts are typically recovered by the optical transport layer network. This is due to cost effectiveness as well as speed of recovery compared to higher layer mechanisms. This leaves the recovery of higher layer failures such as packet switch failures to be considered in the packet-over-optical transport network. Traditionally, the recovery from router failures is performed in the packet layer alone. However, when we consider single failures and recognize that there is restoration capacity provisioned in the optical transport layer to protect against optical layer failures, we see that there is an opportunity for extracting efficiencies via orchestrated actions between the two layers. In this context, we propose a novel joint packet-optical restoration scheme to protect against single packet router failure, where the restoration algorithm manages network resources from both the packet layer and the optical layer in a synergistic manner. In particular, we observe that overlaying joint packet-optical router protection with transport layer protection permits strong synergy of protection capacity reuse. Indeed, our case studies show that the proposed joint packet-optical router protection is lowor no-cost when it is overlaid on the existing transport layer protection scheme.