Proving the Impossible: Provable Route Avoidance using Alibi Routing

We introduce route avoidance using alibi routing, in which a source can provably avoid a particular area when sending traffic to a destination. Our approach combines overlay routing and latency estimation using network coordinates to establish an “alibi” — a packet could not possibly have gone to the relay(s), the area to be avoided, and the destination within the considered timeframe. In our simulation over PlanetLab ping trace data, we show that geographic coordinates map well to 2-D network coordinates and allow us to reason about who can avoid whom and at what costs. We find that geography, particularly the continent and distribution of nodes, is a primary determinant of the possibility and costs of provable avoidance. We also discuss potential extensions to alibi routing, including secure network coordinates and “scaffolding” for constructing paths with multiple relays.