[] Overview
[] Routing Protocols and Knowledge Management
[] High Level Communication Constructs
[] Simple Collaboration - Service-oriented Computing
[] Advanced Collaboration - Workflow Management
Knowledge Management LayerIn Mobile Ad Hoc Networks (MANETs), the network topology evolves rapidly due to the physical motion of hosts, which causes frequent disconnections, leading to a transient interactions among hosts. This constrains distributed applications to an opportunistic communication style and makes providing guarantees difficult. The key problem here is that a given host essentially operates while being "blind" to the network around it. One basic way that we can increase the "field of vision" of a host is by beaconing. This allows hosts to discover other hosts within communication range. However, this method is severely constrained because it requires locality in both the spatial and temporal dimension.
My work extends the "field of vision" of hosts in the MANET beyond the "here and now" to a larger set of locations and points of time in the future. This allows hosts to be cognizant of network conditions in the future and at locations other than the one it is occupying. This enables it to schedule interactions around forward looking communication windows, which in turn makes it possible to provide some loose guarantees on completion times, etc. The mechanics of my approach is shown in Figure 1.
Figure 1: Knowledge Management Mechanism
Publish Subscribe Based Store and Forward Protocol
In MANETs, it is desirable to have a host agnostic protocol so that messages can be addresses according to the semantics of the application they are associated with rather than by host address. This is because application components in a MANET may be logically mobile, and a tight coupling between a host and its role in a distributed application introduces an artificial rigidity. Solving this requires the development of an addressing scheme and routing methodology that is agnostic to host properties.
My work uses a store and forward protocol in combination with a publish-subscribe methodology to build a multi-hop routes for messages that are addressed in a host-agnostic manner. In this approach, the route is not connected end to end at any given time. Rather, a message is forwarded over a single link (when two hosts are directly connected) and stored on the receiving host until the subsequent link becomes available. Messages are contain information about its origin and its destination. This information is application dependent and NOT host dependent. Hosts subscribe to messages of a specific origin and publish messages stamped with its own origin information. The messages migrate towards each other in the network. When a publication "meets" a subscription on an intermediate host, a match is generated and the data is delivered to the subscriber. The mechanism by which this happens is shown in Figure 2. Note that the references to Host 1, Host 4 etc. in the figure below is a reference to their role in the distributed application and not a property of the host itself.
Figure 2: Publish-subscribe-based Store and Forward Protocol
Related Publications
Rohan Sen, Radu Handorean, Gregory Hackmann, and Gruia-Catalin Roman, “Knowledge-driven Interactions with Services across Ad Hoc Networks,” In: International Journal of Collaborative Information Systems, 16(1), pp. 123-153, March 2007 Rohan Sen, Radu Handorean, Gruia-Catalin Roman, and Gregory Hackmann, “Knowledge-Driven Interactions with Services Across Ad Hoc Networks,” In: Proceedings of the 2nd Intl. Conf. on Service Oriented Computing, pp. 222-231, November 2004 Rohan Sen, Gregory Hackmann, Gruia-Catalin Roman, and Christopher Gill, “Opportunistic Exploitation of Knowledge to Increase Predictability of Agent Interactions in MANETs,” In: Proceedings of Software Eng. for Large-Scale Multi-Agent Systems, Digital Proceedings, 2005
