Description
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. Moreover, 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 oscillations due to these disputes occur. This preserves policy freedom when possible, and imposes stability when required.