Browsing by Author "Kommareddy, Christopher"
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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 Rover Technology: Enabling Scalable Location-Aware Computing(2002-01-31) Banerjee, Suman; Agarwal, Sulabh; Kamel, Kevin; Kochut, Andrzej; Kommareddy, Christopher; Nadeem, Tamer; Thakkar, Pankaj; Trinh, Bao; Youssef, Adel; Youssef, Moustafa; Larsen, Ron; Shankar, A. Udaya; Agrawala, AshokLocation-aware computing involves the automatic tailoring of information and services based on the current location of the user. We have designed and implemented Rover, a system that enables location-based services, as well as the traditional time-aware, user-aware and device-aware services. To achieve system scalability to very large client sets, Rover servers are implemented in an "action-based" concurrent software architecture that enables fine-grained application-specific scheduling of tasks. We have demonstrated feasability through implementations for both outdoor and indoor environments on multiple platforms. (Also UMIACS-TR 2001-89)Item Scalable Application Layer Multicast(2002-08-01) Banerjee, Suman; Bhattacharjee, Bobby; Kommareddy, ChristopherWe describe a new scalable application-layer multicast protocol, specifically designed for low-bandwidth data streaming applications with large receiver sets. Our scheme is based upon a hierarchical clustering of the application-layer multicast peers and can support a number of different data delivery trees with desirable properties. We present extensive simulations of both our protocol and the Narada application-layer multicast protocol over Internet-like topologies. Our results show that for groups of size 32 or more, our protocol has lower link stress (by about 25%), improved or similar end-to-end latencies and similar failure recovery properties. More importantly, it is able to achieve these results by using orders of magnitude lower control traffic. Finally, we present results from our wide-area testbed in which we experimented with 32-100 member groups distributed over 8 different sites. In our experiments, average group members established and maintained low-latency paths and incurred a maximum packet loss rate of less than 1% as members randomly joined and left the multicast group. The average control overhead during our experiments was less than 1 Kbps for groups of size 100. Also UMIACS-TR-2002-53