Designing networks with hop bounded protection paths

Network QoS is essential for supporting real time interactive services such as VoIP. In the differentiated services framework QoS is provided by marking packets to receive preferential forwarding treatment, at each network node. This per hop forwarding treatment at each node may however be ineffective in providing the delay and jitter guarantees unless bounds are also imposed on the number of hops in the service routing paths. Interactive services also require minimal interruptions from network disruptions. Routing on hop limited paths may however have an adverse impact on the proportion of network capacity dedicated for protection to guarantee recovery from failures. In this paper we analyze this tradeoff in the context of MPLS fast reroute when protection capacities are pre-provisioned. We show that the underlying optimization problem is NP hard. We design almost best possible approximation algorithms for the problem and show that they work well in practice as well.