Optimizing Restoration with Segment Routing

Segment routing is a new proposed routing mechanism for simplified and flexible path control in IP/MPLS networks. It builds on existing network routing and connection management protocols and one of its important features is the automatic rerouting of connections upon failure. Re-routing can be done with available restoration mechanisms including IGP-based rerouting and fast reroute with loop-free alternates. This is particularly attractive for use in Software Defined Networks (SDN) because the central controller need only be involved at connection set-up time and failures are handled automatically in a distributed manner. A significant challenge in restoration optimization in segment routed networks is the centralized determination of connections primary paths so as to enable the best sharing of restoration bandwidth over nonsimultaneous network failures. We formulate this problem as a linear programming problem and develop an efficient primal-dual algorithm for the solution. We also develop a simple randomized rounding scheme for cases when there are additional constraints on segment routing. We demonstrate the significant capacity benefits achievable from this optimized restoration with segment routing.