Hop-Constrained Node Survivable Network Design: An Application to MPLS over WDM

Abstract

In this paper, we address a hop-constrained node survivable network design problem that is defined in the context of multi-protocol label switching (MPLS) over wavelength division multiplexing (WDM) networks. At the lower WDM layer, we consider a maximum length constraint for optical connections between MPLS routers. At the upper MPLS layer, we consider survivability as well as maximum delay constraints. Survivability is guaranteed by routing each demand through D node-disjoint paths and maximum delay is guaranteed by constraining all paths to a maximum number of hops. An Integer Linear Programming model, based on the previous works by Gouveia et al. (Proc of IEEE INFOCOM, 2003, and Telecommunications network planning: innovations in pricing, network design and management, pp 167–180, 2006) is used to model the network design problem considering two different survivability mechanisms: path diversity (where each demand is equally split over the D paths) and path protection (where any D–1 out of the D paths have enough capacity to support the total demand). For both mechanisms, we use the NSFNet and EON real world networks to make a cost analysis of the design solutions for different values of D. In the path diversity mechanism, the results consistently show that greater values of D impose a cost penalty that is greater than the gain in the percentage of demand that is protected. In the path protection mechanism, where all traffic is totally protected, the results show that the network solutions obtained with D=3 node-disjoint paths have consistently lower costs than the network solutions obtained with D=2 node-disjoint paths. However, using values of D that are greater than 3 led to network solutions with larger costs.