This paper studies the efficient integration of gateway forwarding strategies in wireless ad hoc networks. The problem to solve is the forwarding to one or more gateways in an environment where there is no hierarchical addressing. We provide an overview of the challenges in this area and then compare the properties of two proposed forwarding strategies; traditional default routes and tunnels. We find that default route forwarding will not operate efficiently in a multi-hop environment and that it will, without modifications, operate incorrectly with multiple gateways. On the other hand, we find tunnel forwarding to be architecturally appealing with many properties that make it a suitable forwarding strategy with multiple gateways. We have implemented default route and tunnel forwarding in the AODV routing protocol. We verify in simulation that the incorrect forwarding of default routes has adverse effects on TCP and that the modifications we suggest improve performance, although they do not completely solve the problem. Our simulations also show that our tunnel implementation is efficient and works well with TCP, even with multiple gateways.
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