DHARMA: distributed home agent for robust mobile access

Mobile wireless devices have intermittent connectivity, sometimes intentional. This is a problem for conventional Mobile IP, beyond its well-known routing inefficiencies and deployment issues. DHARMA selects a location-optimized instance from a distributed set of home agents to minimize routing overheads; set management and optimization are done using the PlanetLab overlay network. DHARMA's session support overcomes both transitions between home agent instances and intermittent connectivity. Cross-layer information sharing between the session layer and the overlay network are used to exploit multiple wireless links when available. The DHARMA prototype supports intermittently connected legacy TCP applications in a variety of scenarios and is largely portable across host operating systems. Experiments with DHARMA deployed on more than 200 PlanetLab nodes demonstrate routing performance consistently better than that for best-case Mobile IP.