A Logical Approach to Representing and Reasoning About Interdomain Routing Policies

The Internet paths connecting independently operated networks, also called domains or autonomous systems (ASes), are driven by semantically rich policies: the interdomain routing protocol that computes the Internet paths allows the ASes to influence path selection with their local policies, such as economic concerns or operational constraints. An AS can promote a policy compliant but globally longer path by carefully tweaking lower level path attributes that are used in the routing protocol. Such operational policies are notoriously complex and hard to understand. This paper takes a step back and asks whether a more principled logical approach can lead to AS policies that are easier to understand, reuse, evolve, and coexist. To this end, we propose to represent policies by database integrity constraints, in the form of headless datalog rules about what are the acceptable Internet paths. The simple datalog expression unifies a wide spectrum of AS policies, ranging from classic examples seen in today’s routing practice to futuristic ones proposed in various extensions to Internet routing. More importantly, by leveraging datalog’s connection to the theorem proving technique called the residue method, we developed a new technique for understanding the interactions among the policies — whether a policy can inadvertly affect another, and how to resolve the conflict. We also evaluated our logical policies, showing promising result with small overhead for conflict resolution on realistic large networks.