There are several mechanisms by which users can gain insight into where their packets have gone, but no mechanisms allow users undeniable proof that their packets did not traverse certain parts of the world while on their way to or from another host. This paper introduces the problem of finding "proofs of avoidance": evidence that the paths taken by a packet and its response avoided a user-specified set of "forbidden" geographic regions. Proving that something did not happen is often intractable, but we demonstrate a lowoverhead proof structure built around the idea of what we call "alibis": relays with particular timing constraints that, when upheld, would make it impossible to traverse both the relay and the forbidden regions. We present Alibi Routing, a peer-to-peer overlay routing system for finding alibis securely and efficiently. One of the primary distinguishing characteristics of Alibi Routing is that it does not require knowledge of-or modifications to-the Internet's routing hardware or policies. Rather, Alibi Routing is able to derive its proofs of avoidance from user-provided GPS coordinates and speed of light propagation delays. Using a PlanetLab deployment and larger-scale simulations, we evaluate Alibi Routing to demonstrate that many source-destination pairs can avoid countries of their choosing with little latency inflation. We also identify when Alibi Routing does not work: it has difficulty avoiding regions that users are very close to (or, of course, inside of).

Abstract-In Vehicular Ad Hoc Networks (VANETs), geographic routing protocols appear to be a fascinating option since they have generally low delay and small routing overhead and GPS devices are becoming affordable. However, we reveal that geographic routing protocols suffer from routing holes when nodes are distributed only on lines such as cars on roads, trains on rails, and ships on courses. To tackle this problem, we propose a novel geographic routing protocol, Virtual Vertex Routing (VVR), which uses the information of the lines. Using graph formulation, we introduce a new concept, the proximity of a vertex (or a virtual vertex). An intermediate node in this proximity performs routing toward the destination by Floyd algorithm. For routing holes, we propose two countermeasures: greedy routing (VVR-GR) and face routing (VVR-FR). The latter can guarantee the packet delivery. Extensive simulations are performed to show that VVR outperforms GPSR and AODV.

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Abstract-Finding a reliable and efficient routing path in vehicular ad hoc networks (VANETs) is a challenging issue due to high mobility of vehicles and frequent link breakage. Motivated by this, we propose a robust and efficient routing protocol, called MMR. The contribution of this paper is two-fold: two-level routing and a new routing metric. A routing process of MMR consists of the macro level and the micro level. MMR forwards a packet to an approximate location of the destination at the macro level and then forwards a packet to the exact location of the destination at the micro level. This two-level routing reduces the protocol overhead and improves scalability in terms of the number of nodes. MMR also introduces a new routing metric that reduces the protocol overhead and path breakage by considering velocities of vehicles. Through simulations, we show that MMR improves the routing performance by about 30∼40% in highly mobile environments, compared to the existing ad hoc routing protocols such as AODV and GPSR

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