Delay Tolerant Lazy Release Consistency For Distributed Shared Memory In Opportunistic Networks

Abstract

Opportunistic networking (ON), a concept which allows a mobile wireless device to dynamically interact with other wireless devices in its immediate vicinity, is a field with great potential to improve the utility of itinerant computational platforms. While ONs increase a device's ability to interact with its peers, the fleeting and intermittent connections between devices make many traditional computer collaboration paradigms, such as distributed shared memory (DSM), virtually untenable. DSM systems, developed for traditional networks, rely on relatively stable, consistent connections among participating nodes. In an ON, connectivity among nodes is distributed in time and space making it useful for delay tolerant applications only. When devices are disconnected their ability to collaborate is interrupted and their computing power underutilized until such time as they encounter their computing partners again. Because nodes within an ON are assumed to have no advance knowledge that they will encounter a specific device in the future, periods of disconnection between nodes could be lengthy or potentially infinite.This thesis proposes delay tolerant lazy release consistency (DTLRC) for implementing distributed shared memory in opportunistic networking environments. DTLRC permits mobile devices to remain independently productive while separated and provides a mechanism for nodes to regain coherence of shared memory if and when they meet again. DTLRC allows nodes to make use of results produced on shared memory while disconnected. Simulations using experimentally determined data traces demonstrate that DTLRC is a viable concept for enhancing cooperation among mobile wireless devices in an opportunistic networking environment.