Flexible Routing with Policy Exchange

Abstract

BGP and its alternatives alike, struggle with distributed policy making in the absence of a central authority: BGP prioritizes independence of the participating networks (e.g., ASes), imposes zero coordination, but has to tolerate inflexible policies each network can express. On the other hand, BGP alternatives (source routing, for example), through coordination, trade independence for flexibility, but only achieve flexibility partially. This paper asks, to achieve flexible routing, what is the fitting adjustment between network independence and coordination? To answer this question, we propose a simple principle that the sole end to interfere with the flexibility of a participating network is to prevent harms — decreasing the level of flexibility — to others. As an instantiation of this principle, we introduce the concept of policy exchange that dynamically adjusts independently set policies on the fly, and develop a preliminary implementation with conditional table, a strong knowledge representation system that allows us to distribute and manipulate policies with the usual SQL-like operators. Our preliminary experiments on realistic network topology and synthetic policies are encouraging.