Sensor networks are meant for sensing and disseminating information about the environment they sense. The criticality of a sensed phenomenon determines it's importance to the end user. Hence data dissemination in a sensor network should be informationaware. Such information-awareness is essential firstly to disseminate critical information more reliably and secondly to consume network resources proportional to criticality of information.In this paper, we describe a protocol called ReInForM to support information awareness in sensor networks. Using ReInForM, data can be delivered at desired levels of reliability at proportional cost, in spite of the presence of significant channel errors. It uses the concept of dynamic packet state in context of sensor networks to control the number of paths required for the desired reliability using only local knowledge of channel error rates and does not require any prior computation or maintenance of these multiple paths. We also show that for uniform unit disk graphs, multiple edge-disjoint paths numbering as many as the average node degree, exist between any source and sink with very high probability. These paths exist in a thin band between source and sink having low deviation from the optimal path. ReInForm utilizes this property in its randomized forwarding mechanism which results in use of all possible paths in this band. Thus as a side effect ReInForM leads to load balancing as well.

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Abstract-We present SPIDER -a system for fast replication or distribution of large content from a single source to multiple sites interconnected over Internet or via a private network. In order to exploit spatial diversity of the underlying network, SPIDER uses an overlay structure composed of dedicated Transit Nodes (TNs). The data transport mechanism in SPIDER leverages this overlay structure to provide a coordinated approach that minimizes the maximum time to replicate to all destination sites (the makespan of content replication). In order to achieve this objective, SPIDER employs two orthogonal components: a) creation of multiple dynamic distribution trees using the transit nodes b) end-to-end reliable data transport with flow control on these trees by chaining point-to-point TCPs. We further present simulations based results to quantify benefits of tree construction algorithms in random topologies. We evaluate the real implementation of the SPIDER in PlanetLab and observe a 2-6 times speed up compared to different existing schemes.

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