In the latest years, Internet traffic has increased at a significantly faster pace than its capacity, preventing efficient bulk data transfers such as data-center services and high-definition user-generated content applications. In this paper, we propose to take advantage of the existing worldwide road infrastructure as an offloading channel to help the legacy Internet assuage its burden. Our results suggest that piggybacking data on vehicles can easily lead to network capacity in the petabyte range.

Abstract. Recent papers have reported on successful application of constraint solving techniques to off-line real-time scheduling problems, with realistic size and complexity. Success allegedly came for two reasons: major recent advances in solvers efficiency and use of optimized, problemspecific constraint representations. Our current objective is to assess further the range of applicability and the scalability of such constraint solving techniques based on a more general and agnostic evaluation campaign. For this, we have considered a large number of synthetic scheduling problems and a few real-life ones, and attempted to solve them using 3 state-of-the-art solvers, namely CPLEX, Yices2, and MiniZinc/G12. Our findings were that, for all problems considered, constraint solving does scale to a certain limit, then diverges rapidly. This limit greatly depends on the specificity of the scheduling problem type. All experimental data (synthetic task systems, SMT/ILP models) are provided so as to allow experimental reproducibility.

The future of Vehicular Ad-Hoc Networks (VANET) will rely mainly on the support of efficient information dissemination protocols, whether we talk about safety applications that warn the driver of an imminent collision, a simple update on traffic conditions, or road-side advertisements. One of the greatest challenges when designing such protocols is how to deliver packets efficiently in a highly mobile environments under intermittent connectivity. Surprisingly, this problem has been under-investigated in the literature. In this paper, we propose, design, and evaluate SERVUS 1 , a robust dissemination protocol that guarantees packet propagation with high delivery ratio and low overhead. SERVUS includes a new broadcast management mechanism that takes advantage of the inherent behavioral properties of the VANET environment. In particular, the proposed protocol can update isolated nodes (or clusters) with missing information while ensuring homogeneous information dispersal at low overhead. Through a number of analyses, we show that SERVUS is highly efficient with regard to the tradeoff between reliability and cost, and overcomes important issues like the broadcast storm problem and the topological temporal fragility.

The success of YouTube has profoundly changed the face of industries dealing with digital content as it provides new means of distribution and promotion. While YouTube poses new opportunities for content creators to quickly reach a large audience of viewers, all videos posted online do not compete on the same footing with regard to popularity. To better understand the variation in the popularity of videos, we investigate the role of social interactions between users. In this way, our work is in stark contrast to prior research that studied user generated content video systems but without considering the structure of social relationships within those systems. In this paper, we conduct measurements on YouTube by applying a novel methodology to identify all the users interacting within the same community of interest. Using user information and the meta-data of posted videos, we analyze the influence of the community-based features of YouTube on the popularity of content posted online. Our analysis shows that users posting videos under a specific category get a better recognition than those actively posting videos belonging to a large variety of categories.

International audienceVehicular ad hoc networks (VANET) are an active area for research and development likely to become an integral part of the communication infrastructure of tomorrow. From road safety to recreation applications, a wide range of services are emerging from the rapid technological advances in vehicles sensing, computing, and wireless capabilities. The key issue with respect to those new purposes is the ability of vehicles to disseminate information collected by on-board sensing devices about their surroundings. In this paper, we propose a component-based approach to analyze existing dissemination protocols for VANETs. Our results help better understand the behavior of each component by avoiding the interplays that may result from their combination. We also identify which technical instantiations best fit to different application profiles and environment parameters, while having regard to the resulting performance issues