Browsing by Author "La, Richard"
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Item An Analytical Model of Epidemic Routing with Immunity for Disruption Tolerant Networks(2010-07) La, RichardWe study the epidemic routing scheme with an immunity mechanism. The immunity mechanism enables more efficient utilization of limited buffer space at the nodes, by allowing nodes to remove outstanding copies of messages that have already been delivered. We develop a new analytical model for estimating the message delivery ratio (MDR) and the average delivery delay (ADD) under a variant of epidemic routing with the immunity mechanism, which we call an immunity routing scheme (IRS). The proposed model is based on a continuous-time Markov chain and takes into finite buffer sizes at the nodes.Item Intradomain Overlays: Architecture and Applications(2003-08-01) Kommareddy, Christopher; Guven, Tuna; Bhattacharjee, Bobby; La, Richard; Shayman, MarkWe introduce an architecture for ``Intradomain Overlays'', where a subset of routers within a domain is augmented with a dedicated host. These strategically placed hosts form an overlay network, and we describe a number of applications for such overlays. These applications include efficient network monitoring, policy- and load-based packet re-routing, and network resource accounting. In this paper, we elaborate on the network monitoring application and describe a distributed protocol for monitoring routers within an AS which has been augmented with a few overlay nodes. The routers and other infrastructure are unaware of the overlay nodes, and the monitoring of individual elements is conducted using plain SNMP. We describe techniques for efficiently synthesizing and transporting the monitored SNMP data, and present results using trace data collected from an AS with 400+ routers. Our results show that the overlay-based monitoring reduces overheads by 2--4 orders of magnitude, and thus enables much finer grained monitoring and traffic engineering than is otherwise possible. (UMIACS-TR-2003-70)Item Network connectivity with heterogeneous mobility(2011) La, RichardWe study the issue of mobile wireless network (MWN) connectivity. In particular, we investigate the smallest communication or transmission range of the nodes necessary for connectivity of MWNs, which we call the critical transmission range (CTR). Unlike many of existing studies, however, the mobilities of the nodes are not assumed homogeneous, and the locations of the nodes are not identically distributed. We examine the distribution of CTR when the number of nodes in the network is large. We show that, under some conditions, the CTR is inversely proportional to the infimum of the average spatial density of the nodes in the network and its distribution goes through a phase transition over a small range.