Agenda de eventos

31 Ago
2011

Unrevealing the structure of live BitTorrent Swarms: methodology and analysis

Michal Kryczka, Institute IMDEA Networks; Rubén Cuevas, Universidad Carlos III de Madrid; Carmen Guerrero, Universidad Carlos III de Madrid; Arturo Azcorra, Universidad Carlos III de Madrid
BitTorrent is one of the most popular application in the current Internet. However, we still have little knowledge about the topology of real BitTorrent swarms and how the traffic is actually exchanged among peers. This paper addresses fundamental questions regarding the topology of live BitTorrent swarms. For this purpose we have collected the evolution of the graph topology of 250 real torrents from its birth during a period of 15 days. Using this dataset we first demonstrate that real BitTorrent swarms are neither random graphs nor small world networks.
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25 Ago
2011

Algorithmic Mechanisms for Internet Supercomputing under Unreliable Communication

Evgenia Christoforou, University of Cyprus; Antonio Fernández Anta, Institute IMDEA Networks; Chryssis Georgiou, University of Cyprus; Miguel A. Mosteiro, Rutgers University at Universidad Rey Juan Carlos
This work, using a game-theoretic approach, considers Internet-based computations, where a master processor assigns, over the Internet, a computational task to a set of untrusted worker processors, and collects their responses. The master must obtain the correct task result, while maximizing its benefit. Building on prior work, we consider a framework where altruistic, malicious, and rational workers co-exist. In addition, we consider the possibility that the communication between the master and the workers is not reliable, and that workers could be unavailable; assumptions that are very realistic for Internet-based master-worker computations.
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25 Ago
2011

Brief Announcement: B-Neck: A Distributed and Quiescent Max-min Fair Algorithm

Alberto Mozo, Universidad Politécnica de Madrid; José Luis López-Presa, Universidad Politécnica de Madrid; Antonio Fernández Anta, Institute IMDEA Networks
In this brief announcement we propose B-Neck, a max-min fair distributed algorithm that is also quiescent. As far as we know, B-Neck is the first max-min fair distributed algorithm that does not require a continuous injection of control traffic to compute the rates. When changes occur, affected sessions are asynchronously informed, so they can start the process of computing their new rate (i.e., sessions do not need to poll the network for changes). The correctness of B-Neck is formally proved, and extensive simulations are conducted. In them it is shown that B-Neck converges relatively fast and behaves nicely in presence of sessions arriving and de- parting.
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23 Ago
2011

Performance evaluation of a Tree-Based Routing and Address Autoconfiguration for Vehicle-to-Internet Communications

Marco Gramaglia, Institute IMDEA Networks; Carlos J. Bernardos, Universidad Carlos III de Madrid; María Calderón, Universidad Carlos III de Madrid; Antonio de la Oliva, Universidad Carlos III de Madrid
Vehicular ad hoc networks have proven to be quite useful for broadcast alike communications between nearby cars, but can also be used to provide Internet connectivity from vehicles. In order to do so, vehicle-to-Internet routing and IP address autoconfiguration are two critical pieces. TREBOL is a tree-based and configurable protocol which benefits from the inherent tree-shaped nature of vehicle to Internet traffic to reduce the signaling overhead while dealing efficiently with the vehicular dynamics.
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19 Ago
2011

Insomnia in the Access or How to Curb Access Network Related Energy Consumption

Eduard Goma, Telefónica Research; Marco Canini, EPFL; Alberto Lopez Toledo, Telefónica Research; Nikolaos Laoutaris, Telefónica Research; Dejan Kostic, EPFL; Pablo Rodriguez, Telefónica Research; Rade Stanojević, Institute IMDEA Networks; Pablo Yagüe Vale
Access networks include modems, home gateways, and DSL Access Multiplexers (DSLAMs), and are responsible for 70-80% of total network-based energyconsumption. In this paper I'll take an in-depth look at the problem of greeningaccess networks, identify three root problems, and propose practical solutionsfor their user- and ISP-parts. On the user side, the combination of  continuous light traffic and lack of alternative paths condemnsgateways to being powered most of the time despite having Sleep-on-Idle (SoI) capabilities. To address this problem, we introduce Broadband Hitch-Hiking(BH2), that takes advantage of the overlap of wireless networks to aggregate user traffic in as few gateways as possible. In current urban settings BH2can power off 65-90% of gateways.
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18 Jul
2011

Distance-biased Sampling of Networks

Antonio Fernández Anta, Senior Researcher, Institute IMDEA Networks
Sampling a large network with a given distribution has been identified as a useful operation to build network overlays. For example, constructing small world network topologies can be done by sampling with a probability that depends on the distance to a given node. In this talk we describe algorithms that can be used by a source node to randomly select a node in a network with probability distributions that depend on their distance.
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13 Jul
2011

Traffic Attraction through Prefix Deaggregation: An Economic Perspective

Pradeep Bangera, Ayudante de investigación en el IMDEA Networks
ISPs (Internet Service Providers) typically operate as commercial ASes (Autonomous Systems) and obtain revenue by delivering IP (Internet Protocol) traffic of their customers. In particular, the provider-free ASes – which reach the entire Internet without paying anyone for the traffic delivery – sell IP transit to numerous other ASes. IP prefix deaggregation gives the deaggregator some control over Internet traffic flows but increases the memory requirements of IP routers.
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6 Jul
2011

Obscure Giants: Detecting the Provider-Free ASes

Syed Hasan, Ayudante de investigación, Institute IMDEA Networks
We study the detection of the provider-free AS set (PFS), i.e., the set of those Autonomous Systems (ASes) that reach the entire Internet without paying anyone for the traffic delivery. Using trustworthy but non-verifiable sources for sanity checks, we derive the PFS from public datasets of inter-AS economic relationships. Whereas a straightforward method for extracting the PFS performs poorly because the datasets are noisy, we develop a more sophisticated Temporal Cone (TC) algorithm that relies on topological statistics and exploits the temporal diversity of the datasets. The evaluation shows that our TC algorithm detects the PFS with a high accuracy.
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29 Jun
2011

Where are my followers? Understanding the Locality Effect in Twitter

Dr. Ruben Cuevas, Profesor Titular, Universidad Carlos III de Madrid
Twitter is one of the most used applications in the current Internet with more than 200M accounts created so far. As other large-scale systems Twitter can obtain benefit by exploiting the Locality effect existing among its users. In this paper we perform the first comprehensive study of the Locality effect of Twitter. For this purpose we have collected the geographical location of around 1M Twitter users and 16M of their followers. Our results demonstrate that language and cultural characteristics determine the level of Locality expected for different countries.
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22 Jun
2011

FakeDetector: A measurement-based tool to get rid out of fake content in your BitTorrent Downloads

Michal Kryczka, Ayudante de investigación, Institute IMDEA Networks
Fake content represents an important portion of those files shared in BitTorrent. In this paper we conduct a large scale measurement study in order to analyse the fake content publishing phenomenon in the BitTorrent Ecosystem. Our results reveal that a few tens of users are responsible for 90% of the fake content. Furthermore, more than 99% of the analysed fake files are linked to either malware or scam websites. This creates a serious thread for the BitTorrent ecosystem. To address this issue, we present a new detection tool named FakeDetector that may prevent the download of almost 10 millions of fake files per year based on our evaluation. This could help to reduce the number of computer infections and scams suffered by BitTorrent users.
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