Survivable IP topology design with re-use of backup wavelength capacity in optical backbone networks

In IP-over-WDM networks, wavelength circuits are often protected by dedicated backup circuits. Especially with future deployment of 100 G transmission systems, this will induce huge under-utilization of backup resources. Network utilization can be boosted by loaning the idle backup circuits to preemptible IP/packet services. Unfortunately, if the idle backup circuits are loaned to support IP requests then, in case of failure of the backup circuit, IP demands over the backup circuit get preempted. So, the choice of the backup circuits that can be loaned to IP/packet services must be carefully preplanned, since, in order to fully reroute the preempted IP traffic, the IP topology must remain connected. Note that a single failure in the WDM layer may affect both the links that are directly interrupted by the failure and also those links which get preempted due to the failure. Thus, only those backup circuits can be loaned which do not disconnect the IP topology in case of a failure. In this paper, we propose a mathematical formulation for the design of survivable IP topology with re-use of backup wavelength capacity. We observe that borrowing idle backup capacity to preemptible IP traffic enables much higher resource utilization, allowing for relevant decrease of network cost, and that we can still ensure combined survivability of both IP and wavelength services. A fast and computationally efficient heuristic approach is also presented.