Determining event ordering in mobile ad hoc networks

Determining event ordering has always been a crucial issue in distributed computing. A well known model for describing event ordering is the happened-before relation. However, the traditional happened-before relation model is inadequate to faithfully characterize event ordering in recent emerging mobile ad hoc networks (MANETs), which usually have no fixed supporting infrastructure and may experience dynamic network topology changes. In this paper, we first propose a new relation, called the extended-happened-before relation, to model the ordering of events for a MANET. Then we present an algorithm to assign logical time to events such that the extended-happened-before relation between events can be decided by comparing their timestamps. We finally show how to construct consistent global snapshots in a MANET when the ordering of events can be determined.