Wireless ad hoc networks have emerged to be used in scenarios where it is required or desired to have wireless communications among a variety of devices without relying on any infrastructure or central management.

One of the fundamental operations in wireless ad hoc networks is broadcasting, where a wireless device (simply called a node) disseminates a message to all other nodes in the network. A major challenge of efficient broadcast algorithms is to reduce the number of transmissions required to disseminate a message. Unfortunately, minimizing the total number of required transmissions is an NP-hard problem even when the whole network topology is known by every node. Reducing the number of transmissions becomes more challenging in local broadcast algorithms, where each node makes decision (whether or not to transmit a received message) based on local neighborhood information. The common belief is that local broadcast algorithms are not able to guarantee both full delivery and a good bound on the number of transmissions.

Delay Tolerant Networks (DTN) are networks of self-organizing wireless nodes, where end-to-end connectivity is intermittent. In these networks, content or information between nodes is exchanged (opportunistically), whenever two nodes are within range ("in contact"). Forwarding decisions are generally probabilistic and based on locally collected knowledge about node behavior (e.g., past contacts between nodes) to predict future contact opportunities. The use of complex network analysis has been recently suggested to perform this prediction task and improve the performance of opportunistic (DTN) routing. Contacts seen in the past are aggregated to a "Social Graph", and a variety of metrics (e.g., entrality and similarity) or algorithms (e.g., community detection) can be used to assess the utility of a node to deliver a content or bring it closer to the destination.

The optimal configuration of the contention parameters of a WLAN depends on the network conditions in terms of number of stations and the traffic they generate. Following this observation, a considerable effort in the literature has been devoted to the design of distributed algorithms that optimally configure the WLAN parameters based on current conditions. In this work we propose a novel algorithm that, in contrast to previous proposals which are mostly based on heuristics, is sustained by mathematical foundations from multivariable control theory. A key advantage of the algorithm over existing approaches is that it is compliant with the 802.11 standard and can be implemented with current wireless cards without introducing any changes into the hardware or firmware. We study the performance of our proposal by means of theoretical analysis, simulations and a real implementation. Results show that the algorithm substantially outperforms previous approaches in terms of throughput and delay.

El próximo lunes, Ruben Cuevas defenderá su tesis titulada: “Dynamic and Location-Aware Server Discovery Using a Fair Distributed Hash Table”, tutorada por la Dr. Carmen Guerrero, Profesor Titular, Universidad Carlos III de Madrid e investigador de NETCOM Research Group.

Users' demands for Internet connectivity anytime anywhere are no longer a future requirement, but a reality that operators face today. The current trend in hand-held devices, equipped with multiple access technologies, and accessing IP data services triggered the need for mobility support managed by the IP layer. However, the complexity of protocols such as Mobile IP complicated the deployment of solutions in real products. Lately, there is a new trend toward solutions that enable the mobility of IP devices with a local domain with only the support from the network. Proxy Mobile IPv6 is the solution standardized by the IETF that follows this "novel" approach.

Multimedia content delivery is projected to be the biggest bandwidth consumer of the future Internet. For many years, the mechanism for content delivery envisioned by the networking community is network multicast.

Multicasting emulates traditional TV broadcasting; it is designed to be network efficient. But it falls short in at least two aspects: (a) it does not maximize throughput for content delivery; (b) like TV broadcasting, it does not provide on-demand access (i.e. Video-on-Demand).

Embedded sensor systems are well suited to provide context data, i.e. any information which allows determining the context of entities (e.g. a user's location, an object's environmental parameters, or the number of people in a room). The additional integration of actuators allows interaction with the real world, e.g. control of heating, ventilation, or lighting. However, the big gap between the heterogeneous set of devices providing sensing and/or actuation needs to be bridged to enable smart context-aware applications. Special consideration hereby needs to be given to the efficient use of the available energy budget and the support for device heterogeneity. In this talk, means towards energy-efficient data transfer by applying header and payload compression for Wireless Sensor and Actuator Networks (WSAN) are presented, as well as our approach towards the seamless integration of WSAN nodes through using semantic self-descriptions and means towards unifying the access to node resources.

Whereas prefix hijacking is usually examined from security perspectives, this paper looks at it from a novel economic angle. Our study stems from an observation that a transit AS (Autonomous System) has a financial interest in attracting extra traffic to the links with its customers. Based on real data about the actual hijacking incident in the Internet, we conduct simulations in the real AS-level Internet topology with synthetic demands for the hijacked traffic. Then, we measure traffic on all inter-AS links and compute the payments of all providers. The analysis of our results from technical, business, and legal viewpoints suggests that hijacking-based traffic attraction is a viable strategy that can create a fertile ground for tussles between providers. In particular, giant top-tier providers appear to have the strongest financial incentives to hijack popular prefixes and then deliver the intercepted traffic to the proper destinations. We also discuss directions for future research in the area of hijacking-based traffic attraction.

Coordinación: Dirección General de Universidades e Investigación, a través de la Fundación madri+d, Comunidad de Madrid

La iniciativa IMDEA participará en la actividad “Por qué soy científico”, por medio de la intervención los directores de cada uno de los ocho institutos que la componen.

Por qué soy científico

Organizador: Instituto Madrileño de Estudios Avanzados (IMDEA)

Horario: De 18:00 a 19:30

Lugar de celebración y accesos:
Medialab Prado
C/ Alameda, 15. Madrid
Metro: Atocha y Cercanías: Atocha
Autobuses: 6, 10, 14, 19, 26, 27, 32, 34, 37 y 45

Disruptive events such as large-scale power outages, undersea cable cuts, or Internet worms could cause the Internet to deviate from its normal state of operation. This deviation from normalcy is what we call the impact on the Internet, which we also refer to as an "Internet earthquake."