Logical topology design for IP rerouting: ASONs versus static OTNs

IP-based backbone networks are gradually moving to a network model consisting of high-speed routers that are flexibly interconnected by a mesh of light paths set up by an optical transport network that consists of wavelength division multiplexing (WDM) links and optical cross-connects. In such a model, the generalized MPLS protocol suite could provide the IP centric control plane component that will be used to deliver rapid and dynamic circuit provisioning of end-to-end optical light paths between the routers. This is called an automatic switched optical (transport) network (ASON). An ASON enables reconfiguration of the logical IP topology by setting up and tearing down light paths. This allows to up- or downgrade link capacities during a router failure to the capacities needed by the new routing of the affected traffic. Such survivability against (single) IP router failures is cost-effective, as capacity to the IP layer can be provided flexibly when necessary. We present and investigate a logical topology optimization problem that minimizes the total amount or cost of the needed resources (interfaces, wavelengths, WDM line-systems, amplifiers, etc.) in both the IP and the optical layer. A novel optimization aspect in this problem is the possibility, as a result of the ASON, to reuse the physical resources (like interface cards and WDM line-systems) over the different network states (the failure-free and all the router failure scenarios). We devised a simple optimization strategy to investigate the cost of the ASON approach and compare it with other schemes that survive single router failures

Logical topology optimisation for dynamic multi-layer recovery schemes

This paper summary includes an overview description and first results of ongoing work on a logical topology optimisation problem. The problem is to rind an optimal IP topology that routes a given IP demand matrix and makes it resilient against single router failures. The functionality of an underlying ASON is used to ensure survivability against single router failures, leading to what is called a dynamic multi-layer resilience strategy. The routing in the IP layer is chosen to be OSPF in order to limit operational complexity. The recovery mechanisms in the optical layer make it survivable against cable cuts or optical node failures. The objective is to minimise the total cost of the needed resources, like IP router interfaces and WDM line system equipment. New in this optimisation problem is the possibility, as a result of the ASON, to reuse resources over the failure free and the failure scenarios