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Schedule for Spring 2008
Unless otherwise noted *, seminars are held on Thrusdays at 11:00AM (-12:30PM) in the Graduate Lounge (CS Research Lab)

March 27, 2008
Speaker: Raymond Sweha

In this talk I will present a set of techniques used for End-System Stream Multicast -- specifically those proposed by Jin, Sharma, Bestavros, and Matta (see references below). These techniques were inspired/influenced by the Skyscraper approach proposed by Hua et al. I will contrast cache-and-relay versus prefetch-and-relay, whereby in the former end-systems cache played-back content as opposed to prefetch future content in the stream.

1) Kien Hua. Skyscraper Broadcasting: A New Broadcasting Scheme for Metropolitan Video-on-Demand Systems. In proceedings of SIGCOMM'97
This Paper presnet the Skyscraper approach which is the base for the work we present.

2) Shudong Jin and Azer Bestavros. Cache-and-Relay Streaming Media Delivery for Asynchronous Clients. In proceedings of NGC'02
This paper overviews the basic "Cache and Relay" approach and presents analytical results regarding its scalability.

3) Azer Bestavros and Shudong Jin. OSMOSIS: Scalable Delivery of Real-Time Streaming Media in Ad-Hoc Overlay Networks. In Proceedings of IEEE ICDCS'03.
This paper presents the implementation details of Cache and Relay systems.

4) Abhishek Sharma Azer Bestavros and Ibrahim Matta. dPAM: A Distributed Prefetching Protocol for Scalable Asynchronous Multicast in P2P Systems. In Proceedings of Infocom'05.
This paper considers the effects of churn on cache and relay systems, and proposes the use of prefetching as a better technique. It provides evidence of the scalability of this technique even in the presence of churn.

April 10, 2008
Speaker: Pietro Michiardi

April 17, 2008
Speaker: Chong Wang
I will present the following 2 papers from Sigcomm 2006 and 2007: P.Mahadevan, D.Krioukov, K.Fall, A.Vahdat, Systematic Topology Analysis and Generation Using Degree Correlations P.Mahadevan, C.Hubble, D.Krioukov, B.Huffaker, A.Vahdat, Orbis: Rescaling Degree Correlations to Generate Annotated Internet Topologies

ABSTRACT: Researchers have proposed a variety of metrics to study topological properties of networks. However, there is little understanding of the relationships among individual metrics or their applicability to different settings. A systematic method uses dK-series of probability distributions specifying all degree correlations within d-sized subgraphs of a given graph. Techniques to construct random graphs that reproduce dK-series will be discussed. Experiments show that d=2 case can approximately reconstruct the Internet AS- and router-level topologies. Based on this and other observations of Internet characteristics, graphs of different sizes that reproduce 2K-series can be generated. Finally, the Internet's router level topologies annotated with AS membership information can be generated using a top-down approach.
May 1, 2008
Speaker: Christine Bassem Shafik

ABSTRACT: Service discovery is one of the crucial components in ubiquitous computing where people and computational devices embedded in the surroundings invisibly interact and share services. Such services are either hardware, like printers, fax machines, or software like files or drivers. In this paper, we focus on the challenges of designing a dependable and efficient service discovery protocol for highly dynamic ad hoc networks. Due to the nature of such networks, service discovery faces various challenges such as the high mobility of the devices, the limited battery power and the nonexistence of an infrastructure. A fully distributed, energy efficient, service discovery protocol is proposed and its performance is evaluated through simulation experiments. Results showed a significant improvement in terms of saving the power capacity of the devices in the network and minimizing the delay and the failure rate of service requests.

May 12, 2008 at 2:00pm
Speaker: Andrej Cvetkovski

Title: Geographic routing using hyperbolic space
Author: Robert Kleinberg

ABSTRACT: We propose a scalable and reliable point-to-point routing algorithm for ad hoc wireless networks and sensor-nets. Our algorithm assigns to each node of the network a virtual coordinate in the hyperbolic plane, and performs greedy geographic routing with respect to these virtual coordinates. Unlike other proposed greedy routing algorithms based on virtual coordinates, our embedding guarantees that the greedy algorithm is always successful in finding a route to the destination, if such a route exists. We describe a distributed algorithm for computing each node's virtual coordinates in the hyperbolic plane, and for greedily routing packets to a destination point in the hyperbolic plane. (This destination may be the address of another node of the network, or it may be an address associated to a piece of content in a Distributed Hash Table. In the latter case we prove that the greedy routing strategy makes a consistent choice of the node responsible for the address, irrespective of the source address of the request.) We evaluate the resulting algorithm in terms of both path stretch and node congestion.

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