A Distributed Snapshot Algorithm Adapted for Message Delivery to Mobile Units

Mobile computing is emerging as a novel paradigm with its own characteristic problems, models, and algorithms. Much eeort is being expended on integrating mobile units with xed networks, providing bridges to connect wireless to wired. The result is a xed core of static nodes and a uid fringe of mobile units, an overall system similar to the cellular telephone network. With this graph as a foundation, our approach to mobility treats the mobile units themselves a persistent messages moving through the network. This model allows algorithms from traditional distributed computing to be directly implemented in the mobile environment. However, it has been noted that because of the unique properties of mobility such as limited bandwidth and disconnection, it is not practical to do such a direct translation. This paper presents a fundamentally diierent direction. Previous work has focused on moving distributed algorithms into the mobile domain to solve the same types of problems, while we adapt distributed algorithms to solve issues unique to the mobile environment. Speciically, we propose an algorithm based on distributed snapshots which accomplishes guaranteed unicast and broadcast message delivery to rapidly moving mobile units.