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RelayCast: Scalable Multicast Routing in Delay Tolerant Coalition Networks


Mobile wireless networks with intermittent connectivity, often called Delay/Disruption Tolerant Networks (DTNs), have recently received a lot of attention because of their applicability in various applications, including multicasting. To overcome intermittent connectivity, DTN routing protocols utilize mobility-assist routing by letting the nodes carry and forward the data. In this paper, we study the scalability of DTN multicast routing. As Gupta and Kumar showed that unicast routing is not scalable, recent reports on multicast routing also showed that the use of a multicast tree results in a poor scaling behavior. However, Grossglauser and Tse showed that in delay tolerant applications, the unicast routing overhead can be relaxed using the two-hop relay routing where a source forwards packets to relay nodes and the relay nodes in turn deliver packets to the destination via mobility, thus achieving a perfect scaling behavior of _(1). Inspired by this result, we seek to improve the throughput bound of wireless multicast in a delay tolerant setting using mobility-assist routing. In this paper, we propose RelayCast, a routing scheme that extends the two-hop relay algorithm in the multicast scenario. Given that there are ns sources each of which is associated with nd random destinations, our results show that RelayCast can achieve the throughput upper bound of _(min(1, nnsnd)). RelayCast is then extended to delay tolerant coalition networks where multiple domains exist, and nodes communicate with other nodes in different domains via gateways due to security concerns and policy reasons. We find the throughput and delay scaling properties of inter-domain RelayCast and report that there is an optimal inter-domain networking configuration that achieves the same scaling behavior as single domain multicast.

Paper: PDF file of paper

Information & Date

Annual Conference of ITA 2009 (ACITA 09), Adelphi, MD, September. 2009


Uichin Lee
Soon Young Oh
Kang-Won Lee
Mario Gerla