Bandwidth-based Heavily Loaded Lightpath Protection for IP/MPLS-over-Optical Networks

This paper addresses the problem of provisioning survivability/protection from component failures in IP/MPLS-over-Optical Wavelength Division Multiplexing (WDM) networks. Particularly, it considers a promising multi-layer protection scheme proposed in the literature. The protection scheme has compulsory IP/MPLS layer protection for every request for guaranteed recovery. The scheme also includes optical layer protection for selected lightpaths only when they are ‘heavily loaded’ with equal or more number of traffic requests than a threshold value, and when enough resources are available (such lightpaths are referred to as ‘number-based’ heavy lightpaths). Such optical layer protection has benefits including bulk-recovery, short reroute-times, and reduced failure notifications. However, we find and illustrate that the number-based heavy lightpath protection in the existing scheme has potential drawbacks including bandwidth wastage. To address this issue, we propose alternative definitions of heavy lightpaths which are bandwidth-based instead of pure number-based. The multi-layer survivability with the new bandwidth-based heavy lightpath protection could potentially reduce the bandwidth wastage. However, a challenge is that the new definitions could declare a large number of lightpaths heavy and the optical layer protection could consume more resources (therefore more blocking). To find the effectiveness of our proposal, we carry out extensive simulation based experiments. Our findings verify that our proposal has significantly reduced bandwidth wastage and, at the same time, the challenge it poses (blocking) is contained well within the acceptable range. They also show that our proposal’s practical usage, in terms of the number of heavy lightpaths seen at any given time and the probability of successfully protecting a heavy lightpath, is significant compared to the existing scheme at low traffic loads, making it very effective for network providers.