Role of Optical Network in ResilientIP Backbone Architecture

layer is the third component, the optical switch, which interconnects the core routers via a switched optical network layer over WDM links. While new high-availability (so-called “non-stop routing”) core routers provide service resiliency at the packet layer, the optical layer provides lowest cost and highest level of resiliency at the physical layer against catastrophic network events such as optical amplifier failure and fiber cuts. Focusing on the second and third components of the integrated network evolution, there are four network architectures of interest. Current IP networks connect core routers directly over WDM in a dual-router configuration. This is architecture 1 and the Present Mode of Operations (PMO). Incorporating an optical core transport network leads to architecture 2. As the number of nodes in a network grows, the transit traffic in a node grows exponentially. Since optical switch port costs are only a fraction of the router port costs, the optical switches allow significant cost reduction by siphoning off the transit traffic from the router layer to the optical layer. In addition, further resiliency is achieved by restoring high-capacity WDM links at the optical layer, building upon the deployment of WDM-based optical networks that support fast and capacity-efficient shared mesh restoration. Finally, an optical layer can allow the network to handle surges in IP traffic automatically, or to reroute trunks around a router failure. Common to architectures 1 and 2 is the presence of redundant routers per node, as in today’s current IP backbone networks. To address this architectural aspect, and in conjunction with deploying an optical layer, we propose a new paradigm by which a single (or a few) redundant routers are deployed in the network and used to replace any failed router. This is architecture 3. Effectively, a single (or a few) shared redundant routers replace a second router in each office. This architecture leverages the rearrangeable optical layer to re-home access routers into the remote shared redundant router in case of a core router failure, as well as to appropriately re-trunk the spare router now in use to the rest of the IP network. We also consider with architecture 4 a single core router per node, along with the optical layer, Role of Optical Network in Resilient IP Backbone Architecture