Resolving inter-domain policy disputes

The Border Gateway Protocol (BGP) allows each autonomous system (AS) to select routes to destinations based on semantically rich and locally determined policies. This autonomously exercised policy freedom can cause instability, where unresolvable policy-based disputes in the network result in interdomain route oscillations. Several recent works have established that such instabilities can only be eliminated by enforcing a globally accepted preference ordering on routes (such as shortest path). To resolve this conflict between policy autonomy and system stability, we propose a distributed mechanism that enforces a preference ordering only when disputes resulting in oscillations exist. This preserves policy freedom when possible, and imposes stability when required.