Risk-Aware Routing for Optical TransportNetworks

A Service Level Agreement (SLA) typically specifies the availability a Service Provider (SP) promises to a customer. In an Optical Transport Network (OTN), a lightpath is commonly evaluated by whether its availability complies with the SLA-requested availability. Because of the stochastic nature of link failures, the OTN-layer provisioning is subject to uncertainty, and the SLA is usually at risk. We consider the presence of the network uncertainty, and study routing to minimize the probability of SLA violation. First, we use a single-link model to study SLA Violation Risk under different settings. We show that SLA Violation Risk may vary by paths and is affected by many factors (e.g., failure rate, connection holding time, etc.), and hence cannot be simply described by path availability. We then formulate the problem of risk-aware routing in mesh networks, in which routing decisions are dictated by SLA Violation Risk. In particular, we focus on devising a scheme capable of computing lightpath(s) that are most likely to successfully accommodate the desired SLA-requested availability. We present a polynomial Risk-Aware Routing scheme using only limited failure information. A novel technique is applied to convert links with heteroeonous failure profiles to reference links which capture the main risk features in a relative manner. In addition, we extend our Risk-Aware Routing scheme to incorporate shared path protection (SPP) when backup is needed. Extensive simulations are conducted to demonstrate the efficiency of our schemes in terms of SLA violation ratio and, more generally, to contrast them with the generic availability-aware approaches