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Scientific Posters
Here you can find the scientific posters that were exhibited on the Open House Day
Title: P2P-TVfor the IPMultimedia Subsystem
Author: Alex Bikfalvi, Jaime García-Reinoso
Publication date: 18th November 2011
Abstract: In network architectures such as NGN/IMS, bandwidth reservation and centralized control is necessary. In this setting, providing cost-e ective but high quality video streaming services that take advantage of P2P technology remains an important challenge. In particular, consumer-class IPTV su ers from a high churn rate generated by repeated channel changes. This work enhances the performance of such a system in two ways: (i) by leveraging the peers' excess download bandwidth to support, after a channel change, continuous peer participation in previous channels, and (ii) by exploring the user activity to estimate the current demand.
Andra Lutu Poster

Title: A Collateral Benefit for Prefix Deaggregation

Author: Andra Lutu, Rade Stanojevic, Marcelo Bagnulo
Publication date: 18th November 2011
Abstract: The injection of more-specific prefixes through BGP is a powerful traffic engineering tool with a number of well-known side-effects (e.g. increase in the size of the BGP routing table).
We study the impact of deaggregation on the transit traffic bill of the networks originating the more-specific prefixes
Title: Rate Allocation for Layered Multicast Streaming with Inter-Layer Network Coding
Author: Joerg Widmer, Andrea Capalbo, Antonio Fernández Anta, Albert Banchs
Publication date: 18th November 2011
Abstract: Multi-layer video streaming allows to provide different video qualities to a group of multicast receivers with heterogeneous receive rates. For layered multicast streaming, network coding provides higher capacity than multicast routing. The optimum solution to a network coded layered multicast problem may require decoding of the network code at interior nodes to extract information to be forwarded and decoding consumes resources, introducing delay. We propose a heuristic based on the Edmonds-Karp maximum flow algorithm and we prove that our algorithm ensures decodability of the information received, by providing some fairness properties.
Title: Energy efficiency in Wireless Access Network
Author: Andrés García-Saavedra
Publication date: 18th November 2011
Abstract: We no longer want to maximize the bits sent per time unit, but instead maximize the bits the network can send per each joule consumed. Energy efficiency (EF) and throughput constitute a different objective to optimize. In a scenario with disimilar stations, there exist a trade-off between the configuration that maximizes energy efficiency and the configuration that provides fair allocation of throughput. We propose the Energy-efficiency Proportional Fairness criterion.
Title: CIPT: Using Tuangou to Reduce IP Transit Costs
Author: Rade Stanojevic, Ignacio Castro, Sergey Gorinsky
Publication date: 18th November 2011
Abstract: A majority of ISPs (Internet Service Providers) support connectivity to the entire Internet by transiting their trafic via other providers. Although the transit prices per Mbps decline steadily, the overall transit costs of these ISPs remain high or even increase, due to the trafic growth. The discontent of the ISPs with the high transit costs has yielded notable innovations such as peering, content distribution networks, multicast, and peer-to-peer localization. While the above solutions tackle the problem by reducing the transit trafic, this paper explores a novel approach that reduces the transit costs without altering the trafic. In the proposed CIPT (Cooperative IP Transit), multiple ISPs cooperate to jointly purchase IP (Internet Protocol) transit in bulk. The aggregate transit costs decrease due to the economies-of-scale effect of typical subadditive pricing as well as burstable billing: not all ISPs transit their peak trafic during the same period. To distribute the aggregate savings among the CIPT partners, we propose Shapley-value sharing of the CIPT transit costs. Using public data about IP trafic of 264 ISPs and transit prices, we quantitatively evaluate CIPT and show that significant savings can be achieved, both in relative and absolute terms. We also discuss the organizational embodiment, re-lationship with transit providers, trafic confidentiality, and other aspects of CIPT.
Title: Bisection (Band)Width of Product Networks with Application to Data Centers.
Author: Jordi Arjona, Antonio Fernández Anta
Publication date: 18th November 2011
Abstract: The bisection width of interconnection networks has always been important in parallel computing, since it bounds the amount of information that can be moved from one side of a network to another, i.e., the bisection bandwidth. Finding the exact value of the bisection width has proven to be challenging for some network families. For instance, the problem of finding the exact bisection width of the multidimensional torus was posed by Leighton (Problem 1.281) and has remained open for almost 20 years. In this paper we provide the exact value of the bisection width of the torus, as well as of several d-dimensional classical parallel topologies that can be obtained by the application of the Cartesian product of graphs. To do so, we first provide two general results that allow to obtain upper and lower bounds on the bisection width of a product graph as a function of some properties of its factor graphs. We also apply these results to obtain bounds for the bisection bandwidth of a d-dimensional BCube network, a recently proposed topology for data centers.
Title: Energy Efficient File Distribution
Author: Kshitiz Verma, Gianluca Rizzo, Antonio Fernández Anta, Rubén Cuevas
Publication date: 18th November 2011
Abstract: In this work, we focus on energy efficiency in file distribution in a wired network. We derive lower and upper bounds on the energy required for the distribution process and design algorithms achieving the bounds. We find that upto 50% energy can be saved using our file distribution schemes over conventional ones.
Title: Optimized IPv6 Internet access from vehicles in multi-hop and heterogeneous environments
Author: Marco Gramaglia
Publication date: 18th November 2011
Abstract: In order to provide  efficient Internet connectivity from vehicles, three fundamental functionalities are needed: IP address autoconfiguration, enhanced routing and mobility support. The work briefly presented in this poster aims at providing a solution for these three open issues. An analytical model for an address autoconfiguration mechanism and a routing protocol have been already proposed, with accepted contributions. A third line analyzing mobility aspects is currently being developed. Another accepted contribution is a statistical framework for studying the interarrival time between vehicles, that has been elaborated using real traffic measurements.
Title: TORRENTGUARD: Unrevealing dark side of the BitTorrent
Author: Michal Kryczka, Rubén Cuevas, Arturo Azcorra
Publication date: 18th November 2011
Abstract: N/A
Title: Traffic Attraction through Prefix Deaggregation: An Economic Perspective
Author: Pradeep Bangera, Sergey Gorinsky
Publication date: 18th November 2011
Abstract: 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. This work offers a novel economic perspective on prefix deaggregation. In particular, we investigate whether provider-free ASes have financial incentives to deaggregate prefixes in order to attract additional IP traffic of their customers. Our study combines analysis with extensive simulations seeded by actual data. Using a realistic AS-level Internet topology, we derive a traffic-matrix model and then conduct simulations in our optimized version of C-BGP.
Title: Feasibility of floating content service for context-aware applications
Author: Shahzad Ali, Gianluca Rizzo, Marco Ajmone Marsan
Publication date: 18th November 2011
Abstract: Applications are getting context-aware because they need to operate in a mobile environment. Context-awareness paves the way towards smart environments and adaptive applications. Opportunistic communications are a natural candidate for such applications because they naturally incorporate context and also relieves the user from relying on infrastructure. But lack of infrastructure support in mobile environment can not guarantee performance for context-aware applications.
Title: Obscure Giants: Detecting the Provider-Free ASes
Author: Syed Hasan, Sergey Gorinsky
Publication date: 18th November 2011
Abstract: Internet routing depends on economic relationships between ASes (Autonomous Systems). Despite extensive prior research of these relationships, their characterization remains imprecise. In this work, we focus on provider-free ASes that reach the entire Internet without paying anyone for the traffic delivery. While the ground truth about PFS (set of the provider free ASes) lies outside the public domain, we use trustworthy non-verifiable sources as a baseline for result validation. Straightforward extraction of PFS from public datasets of inter-AS economic relationships yields poor results. Then, we develop a more sophisticated Temporal Cone (TC) algorithm that relies on topological statistics (customer cones of ASes) and exploits the temporal diversity of the datasets. Our evaluation shows that the TC algorithm infers PFS from the same public datasets with a significantly higher accuracy. We also assess the sensitivity of the TC algorithm to its parameters.