The design of ad hoc mobile applications often requires the availability of a consistent view of the application state among the participating hosts. Such views are important because they simplify both the programming and verification tasks. We argue that preventing the occurrence of unannounced disconnection is essential to constructing and maintaining a consistent view in the ad hoc mobile environment. In this, we provide the specification for a group membership service supporting ad hoc mobile applications and propose a protocol for implementing the service.

A unique property of this group membership is that messages sent between group members are guaranteed to be delivered successfully, given appropriate system assumptions. This property is preserved over time despite movement and frequent disconnections. The protocol merges groups and maintains a logical connectivity graph based on a notion of safe distance. The process called Merging, which will lead to combine the groups, which are in the safe distance by maintaining the leader for each group, provides the guaranteed delivery of messages.

Group membership has been an important problem in the area of fault-tolerant distributed computing. Solving the problem requires the provision of a service that establishes and maintains some kind of agreement over time among participating components about who is currently in the group, despite the presence of failures in the corresponding distributed system. Such a group membership service simplifies the development of many fault-tolerant distributed applications and is widely used
for supporting reliable group communications.

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