Role of optical network and spare router strategy in resilient IP backbone architecture

At the heart of IP backbone networks are the core IP routers with throughput of hundreds of Gb/s. These routers with interfaces operating at the per-wavelength bit rates are directly connected via point-to-point WDM optical-transport systems. For acceptable service reliability even for best effort services typically two interconnected routers are used for redundancy in each backbone node. It has been established that the majority of the traffic in a node is transit traffic and a significant cost reduction can be achieved by siphoning off the transit traffic from the IP layer into the optical layer. In this paper we discuss the current trend in the IP backbone network which is poised to take over other premium services, in addition to best effort IP services, as an integrated transport platform. We discuss several network architecture options with the critical attribute being that it must be as resilient as the current SONET transport network. We propose an innovative architecture option in which a resilient network is built with current router technology. In another option we assume that the router layer can be as resilient as the current SONET layer with the emerging resilient router technology. We perform an economic evaluation and discuss the reliability of these network architectures.