Don’t Mind the Gap: Bridging Network-wide Objectives and Device-level Configurations

We develop Propane, a language and compiler to help network operators with a challenging, error-prone task—bridging the gap between network-wide routing objectives and low-level configurations of devices that run complex, distributed protocols. The language allows operators to specify their objectives naturally, using high-level constraints on both the shape and relative preference of traffic paths. The compiler automatically translates these specifications to router-level BGP configurations, using an effective intermediate representation that compactly encodes the flow of routing information along policy-compliant paths. It guarantees that the compiled configurations correctly implement the specified policy under all possible combinations of failures. We show that Propane can effectively express the policies of datacenter and backbone networks of a large cloud provider; and despite its strong guarantees, our compiler scales to networks with hundreds or thousands of routers.