Middleware for service provision in disconnected mobile ad hoc networks

Abstract : Mobile ad hoc networks (MANETs) are spontaneously formed out of mobile devices that communicate thanks to short-range wireless communication capabilities (e.g. Wi-Fi, Bluetooth). In many ad hoc networks deployed in real conditions, mobile devices can exhibit highly dynamic behaviors of mobility and volatility. Because of their behavior and their distribution, the devices in such network environments form so-called "islands" whose topology evolves continuously, rather than a single fully connected network. In this work, I focus on this class of MANETs which I refer to as disconnected MANETs. Network-wide communication in disconnected MANETs is still a challenge, namely because routing techniques designed for fully connected MANETs cannot be applied. The store-carry-and-forward approach provides a solution. With this approach, a message can be stored temporarily on a node, in order to be forwarded later when circumstances permit. Mobility then becomes an advantage as it facilitates message propagation from one island to another. The service-oriented computing (SOC) model seems suited for ad hoc environments because it emphasizes the decoupled nature of its entities. Effectively, the decoupling between a client entity and a provider entity becomes essential in mobile environments with a fluctuating availability of providers, and where end-to-end communications are not guaranteed. Still, in existing service-oriented systems, providers are usually supposed to be available and always reachable. Therefore, implementing distributed services for such networks still poses several challenges. Not only network-wide communication features must be provided, in spite of constant network fragmentation, but aspects such as the unpredictable reachability of the providers, or potential communication delays, must be taken into account at the service level. I propose a service platform for mobile nodes that supports the execution of service-oriented applications in disconnected MANETs. The service platform is implemented as a middleware composed of two layers: a communication layer, and a service layer. The communication layer provides mechanisms to decouple two service entities in terms of temporaneous interaction, synchronous behavior, and mutual knowledge. For this layer (DoDWAN), I use an opportunistic and content-driven protocol. The service layer (DiSWAN) provides mechanisms that decouple service providers and clients in terms of interoperability and service contract. For this layer, I propose solutions for service discovery and invocation. The elements that construct the discovery protocol are the description and advertisement at the provider side, and collection and selection at the client side. Description includes functional and nonfunctional service properties, as well as context properties. Discovery is based on a peer-to-peer architecture, where a client collects only interesting services. Content-based invocations are used to benefit from the service replication, in case a multitude of providers can be offering the same business service. A client creates a functional request according to a discovered provider, then publishes its contentbased request message to the attention of all compatible providers. Profiting from this provider multiplicity can generate redundant messages, I propose network healing mechanisms in order to eliminate the redundant invocation requests and responses. Using a prototype implementation of the middleware, I conducted simulations in a disconnected MANET environment. The performances of discovery is directly related to those of the underlying communication layer. Simulations confirm the benefits of content-based invocations in providing faster response times and better client satisfaction. Simulations also show a drastic reduction of redundant and leftover messages when applying the healing mechanisms.
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Submitted on : Monday, May 30, 2011 - 5:26:03 PM
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Romeo Said. Middleware for service provision in disconnected mobile ad hoc networks. Networking and Internet Architecture [cs.NI]. Université de Bretagne Sud, 2011. English. ⟨tel-00596996⟩

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