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.

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.

The technological advancement and information overload in recent years increased the popularity of Distributed Storage Systems where the data is replicated and maintained at multiple disks or servers residing at different network locations. While replication is sufficient to ensure data survivability, it raises an important question: "How can we efficiently maintain consistency among the replicas, despite system asynchrony and failures?"

As wireless ad hoc networking becomes more and more popular and ad hoc networks are used for an increasing number of applications, the integration of these networks in today's Internet, still mostly organized as a set of interconnected fixed and wired networks, becomes a key research field in the computer networking domain. Flooding and routing are some of the main challenges posed by the convergence of the Internet and wireless ad hoc networks

El Madrid Audiovisual Cluster es miembro del comité organizador de BROADCAST, el salón profesional de la tecnología audiovisual, que este año evoluciona hacia un nuevo planteamiento: el certamen dará un salto cualitativo de la tradicional exposición de productos a una propuesta de soluciones y contenidos emergentes. De este modo se adapta a la realidad de la industria de la tecnología audiovisual.

Inter-domain traffic engineering is an important aspect of network operation both technically and economically. Traffic engineering the outbound direction is less problematic as routers under the control of the network operator are responsible for the way traffic leaves the network. The inbound direction is considerably harder as the way traffic enters a network is based on routing decisions in other networks.

It is notoriously difficult to make distributed systems reliable. This becomes even harder in the case of the widely-deployed systems that are heterogeneous (multiple implementations) and federated (multiple administrative entities). The set of routers in charge of the Internet's inter-domain routing is a prime example of such a system.

Ponente: Peter Jacko, Post-doc Fellow, Basque Center for Applied Mathematics (BCAM), Bilbao, España
Lugar: Aula 4.1.F03, Edificio Torres Quevedo, Universidad Carlos III de Madrid, Avda. Universidad, 30, 28911 Leganes – Madrid
Fecha: 28 Octubre 2011, 12:30
Organización: NETCOM Research Group (Telematics Department, Universidad Carlos III de Madrid, España); Institute IMDEA Networks (Madrid, España)

Sleep modes are emerging as a promising technique for energy-efficient networking: by adequately putting to sleep and waking up network resources according to traffic demands, proportionality between energy consumption and network utilization can be approached, with important reductions in energy consumption. Previous studies have investigated and evaluated sleep modes for wireless access networks, computing variable percentages of energy savings.

Distributed Opportunistic Scheduling (DOS) techniques have been recently proposed to improve the throughput performance of wireless networks. With DOS, each station contends for the channel with a certain access probability. If a contention is successful, the station measures the channel conditions and transmits in case the channel quality is above a certain threshold.