Segmented Source Routing for Handling Link Failures in Software Defined Network

When a link fails in Software Defined Networks (SDN), the flows that use the failed link need to be rerouted over other paths. To achieve this rerouting task, researchers have proposed reactive and proactive recovery approaches. In reactive approach, upon failure, SDN controller computes new paths for the affected flows and installs them on demand. In proactive approach, the SDN controller pre-calculates backup paths and installs them on the switches in advance. While proactive approach minimizes packet loss and delay, it introduces a new problem, namely excessive usage of limited TCAM memory at SDN switches. In this paper, we consider two promising techniques (namely source routing and segment routing), and propose a new proactive technique called Segmented Source Routing (SSR). SSR uses source routing but in a segmented manner: one from the failure detecting node to an emergency node and one from emergency node to the destination. After addressing various challenges in placing emergency nodes and assigning emergency nodes to flows, our simulations shows that SSR maintains the same level of performance of pure source routing while significantly reducing the memory overhead, computation overhead, and the packet sizes as it shortens the source routes and avoids storing them at every node.