Events agenda

3 Feb
2010

Seminar: Peer-to-peer vs. IP multicast: comparing approaches to IPTV streaming based on TV channel popularity

Alex Bikfalvi
Already a popular application in the Internet, IPTV is becoming, among the service providers, a preferred alternative to conventional Broadcasting technologies. Since many of the existing deployments have been done within the safe harbor of telcos own networks, IP multicast has been the desired streaming solution. However, previous studies showed that the popularity of the TV channels follows the Pareto principle, with the bulk of TV channels being watched only by a small fraction of viewers. Recognizing the potential scalability issues, we believe that multicast streaming approach may not be desirable for unpopular TV channels, especially when there are many such channels in the provider's service package. 
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29 Jan
2010

The GeoNet Final Workshop

Emilio Davila Gonzalez (European Commission); Arnaud de La Fortelle (INRIA); Thierry Ernst (INRIA); Carlos J. Bernardos (IMDEA Networks); Wenhui Zhang (NEC); Hamid Menouar (Hitachi)
The GeoNet consortium invites you to attend its final workshop as a unique opportunity to learn more about IPv6 geonetworking and the link between IPv6 geonetworking and the related ITS development in CAR 2 CAR Communication Consortium, CVIS implementation and ETSI TC ITS standardization. During the workshop you will get information through communications and posters and also see the system working in real cars. Please find the program in attachment with practical details (exact place, registration procedure…).
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27 Jan
2010

The pain of doing research with real (wireless) devices

Dr. Pablo Serrano
A lot of attention has been given to multihop wireless networks lately. This attention has motivated an increase in the number of 802.11-based deployments, both indoor and outdoor, used to perform measurement studies to analyze WLAN performance by means of wireless sniffers that passively capture transmitted frames. In this talk talk we will introduce some of the major issues that systems researchers have to address when performing such measurements: i) on one hand, the testbed itself requires a significant amount of resources during both its deployment and its maintenance, and they require a "calibration" phase before running the experiments given that as off-the-shelf devices have recently been shown to deviate from the expected behavior–in this talk we summarize a few lessons learned from the deployment of a 28-node wireless testbed; ii) on the other hand, little attention has been given to the fidelity of an individual device, i.e., the ability of a given sniffer to capture all frames that could have been captured by a more faithful device. We assess this fidelity by running controlled experiments, and show that it varies significantly across sniffers, both quantitatively and qualitatively.
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18 Jan
2010

Energy Efficient Ethernet (IEEE 802.3az): Performance Evaluation

Dr. Pedro Reviriego (Universidad Antonio de Nebrija) (Madrid, Spain)
Energy consumption in Computer Networks is an issue that is gaining increasing attention. In this talk we will review the issue of energy consumption in Computer Networks to then focus on Ethernet where a new standard is being developed to improve energy efficiency. We will discuss some of the alternatives that were considered during the Energy Efficient Ethernet standardization process and describe the solution adopted in the standard. Then we will present some results of an initial performance evaluation of the standard that shows the potential savings for different scenarios. We will conclude the talk by outlining the implications that Energy Efficient Ethernet will have on different aspects of the LANs.
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13 Jan
2010

Computing: A small step from Classical to Quantum

Kshitiz Verma, Research Assistant, Institute IMDEA Networks
The Theory of Computing is almost a hundred year old now. Its roots can actually be traced to the Entscheidungsproblem posed by David Hilbert in 1928. Another concrete theory in Physics called the Quantum Mechanics had its inceptions almost two hundred years ago (with Thomas Young's Double Slit Experiment in 1803) but actually started in the late 19th century. Today, Quantum Mechanics is proven to be the most successful theory of Physics. So the natural question to ask was that while the statement of Church-Turing Thesis is seen to be a statement of physics (laws of nature), then it should be compatible with the theory of Quantum Mechanics!
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15 Dec
2009

Routing for Energy Minimization in the Speed Scaling Model

Dr. Antonio Fernández Anta, Laboratory of Distributed Algorithmics and Networks (Laboratorio de Algoritmia Distribuida y Redes - LADyR), Group of Systems and Communications (Grupo de Sistemas y Comunicaciones - GSyC,, Universidad Rey Juan Carlos (Madrid)
The problem is interesting for two reasons. First, the cost function closely models the energy consumption of some network elements and network-wide optimization is a well-motivated but under-explored direction for energy minimization. Second, it brings light to a challenging combinatorial optimization problem. We will present positive and negative results for polynomial functions and polynomial functions with startup cost. For the latter, techniques to accomplish better-than-polynomial approximation ratios independent of demands and cost function remains a challenging problem.
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9 Dec
2009

Design and Evaluation of a robust delay-based congestion protocol

Prof. Dr. Narasimha Reddy (Cátedra de Excelencia, University Carlos III of Madrid; Visiting Researcher, IMDEA Networks, Madrid; Texas A&M University, USA)
Many delay-based congestion protocols have been proposed. Some recent studies have questioned the validity of congestion prediction at end hosts Based on measurement studies. In this talk, we show that end-host based delay prediction can be more accurate than previously characterized. We propose PERT (Probabilistic Early Response TCP) to mitigate the uncertainties in end-host based congestion prediction. PERT emulates the behavior of AQM/ECN in the end hosts' response to congestion.
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2 Dec
2009

Providing Throughput Guarantees in Heterogeneous Wireless Mesh Networks

Dr. Antonio de la Oliva
This talk addresses the problem of providing throughput guarantees in heterogeneous wireless mesh networks. As a first step, it proposes a novel model to represent the capacity region of a wireless link that, by linearizing this region, has the fundamental property of being very simple while providing a good approximation to the entire region. In a second step, this model is mapped to two of the most prominent wireless technologies nowadays, namely Wireless LAN and WiMAX. The last step addresses the issue of finding optimal routing strategies, which is done by solving an optimization problem subject to the constraints imposed by the linearized capacity region. The performance of the proposed approach has been compared against traditional routing metrics in mesh networks, such as ETT and ETX, and shown to overperform them by approximately a factor of 2.
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25 Nov
2009

Deep Diving into BitTorrent Locality

Rubén Cuevas Rumín, PhD Student, Institute IMDEA Networks
A substantial amount of work has recently gone into localizing BitTorrent traffic within an ISP in order to avoid excessive and often times unnecessary transit costs. Several architectures and systems have been proposed and the initial results from specific ISPs and a few torrents have been encouraging. In this work we attempt to deepen and scale our understanding of locality and its potential. Looking at specific ISPs, we consider tens of thousands of concurrent torrents, and thus capture ISP-wide implications that cannot be appreciated by looking at only a handful of torrents. Secondly, we go beyond individual case studies and present results for the top 100 ISPs in terms of number of users represented in our dataset of up to 40K torrents involving more than 3.9M concurrent peers and more than 20M in the course of a day spread in 11K ASes. We develop scalable methodologies hat permit us to process this huge dataset and answer questions such as: What is the minimum and the maximum transit traffic reduction across hundreds of ISPs? What are the win-win boundaries for ISPs and their users? What is the maximum amount of transit traffic that can be localized without requiring fine-grained control of inter-AS overlay connections? What is the impact to transit traffic from upgrades of residential broadband speeds?
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18 Nov
2009

ISP-friendly Swarm-based P2P streaming

Dr. Reza Rejaie, Visiting Researcher IMDEA Networks
Existing Swarm-based Peer-to-Peer Streaming (SPS) applications rely on a randomly connected overlays among peers, which tend to generate a significant amount of costly inter-ISP traffic. To reduce such traffic, localization of overlay connectivity within each ISP has received a great deal of attention as a promising approach for reducing the volume of inter-ISP traffic.  
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