Enabling Policy Innovation in Interdomain Routing: A Software-Defined Approach

BGP is known to restrict policy expressiveness and induce uncontrolled policy interactions that are hard to understand, reuse, and evolve. We argue that the use of a path vector system as the carrier of interdomain policies is the root cause of these limitations. To this end, we propose an alternative policy scheme built in a software-defined controller to decouple policy making from the path vector system. Rather than treating policies as hardwired attributes of a route, that are configured and consumed as the route goes through the path vector decision process, we let policies flow, interact, and combine to influence end to end routes. This new software-defined scheme creates new space for policy language, route decision, and conflict resolution design, towards more flexible policies, cleaner policy enforcement, and controlled policy interaction. As a realization of our vision, we present an implementation that uses data integrity constraints for representing and reasoning about routing policies, addressing unique challenges in the decentralized interdomain environment.