CAM05-1: Impact of Unprotected Multi-Failures in Resilient SPM Networks: a Capacity Dimensioning Approach

Restoration or protection switching mechanisms protect traffic in packet-switched networks against local outages by deviating it around the failure location. This assures connectivity, but sufficient backup capacity is also needed to maintain quality of service (QoS) for the duration of the outage. To that end, sufficient capacity must be provided on the links so that the network can survive a set of protected failure scenarios without congestion due to redirected traffic. The self- protecting multipath (SPM) is a protection switching mechanism for which the required backup capacity can be minimized by linear optimization methods. However, unprotected multi-failures may lead to congestion in such "resilient networks" since backup capacity may be missing. In this paper, we quantify and compare the impact of unprotected double failures on the QoS for the optimized SPM, single shortest path routing (SSP), and equal- cost multipath (ECMP) routing.