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The increasing heterogeneity and asymmetry in wireless network environments makes QoS guarantees in terms of delays and throughput a challenging task. In this paper, we study a novel scheduling algorithm for multipath transport called Delay Aware Packet Scheduling (DAPS) which aims to reduce the receiver's buffer blocking time considered as a main parameter to enhance the QoS in wireless environments. We develop an analytical model of maximum receiver's buffer blocking time and extend the DAPS algorithm considering implementation issues. Performance evaluations based on ns-2 simulations highlight the enhanced QoS that DAPS can provide. With reference to the classical multipath transport protocol CMT-SCTP, we observe a significant reductions of the receiver's buffer occupancy, down by 77%, and the application delay, down by 63%.

Email and chat still constitute the majority of electronic communication on the Internet. The standardisation and acceptance of protocols such as SMTP, IMAP, POP3, XMPP, and IRC has allowed to deploy servers for email and chat in a decentralised and interoperable fashion. These protocols can be secured by providing encryption with TLS-directly or via the STARTTLS extension. X.509 PKIs and ad hoc methods can be leveraged to authenticate communication peers. However, secure configuration is not straight-forward and many combinations of encryption and authentication mechanisms lead to insecure deployments and potentially compromise of data in transit. In this paper, we present the largest study to date that investigates the security of our email and chat infrastructures. We used active Internet-wide scans to determine the amount of secure service deployments, and employed passive monitoring to investigate to which degree user agents actually choose secure mechanisms for their communication. We addressed both client-to-server interactions as well as server-to-server forwarding. Apart from the authentication and encryption mechanisms that the investigated protocols offer on the transport layer, we also investigated the methods for client authentication in use on the application layer. Our findings shed light on an insofar unexplored area of the Internet. Our results, in a nutshell, are a mix of both positive and negative findings. While large providers offer good security for their users, most of our communication is poorly secured in transit, with weaknesses in the cryptographic setup and especially in the choice of authentication mechanisms. We present a list of actionable changes to improve the situation.

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In a transportation system with fully autonomous vehicles (or cybercars), a lot of tasks have to be executed to answer the demand of a customer to travel between two points. The framework of this paper is an approach consisting in decomposing the planning into three levels, each of which using only a relevant subset of the information, thus reducing the complexity: the macroscopic level, e.g. a city or a region; the mesoscopic level, e.g. a city quarter; the microscopic level, i.e. the surroundings of the cybercar.At the macroscopic level, a path is computed. By path, we mean a succession of edges (road segments) in the graph description of the road network.At the mesoscopic level, paths are transmitted by the upper level and turned into trajectories. A trajectory is a precise space-time curve that the cybercar has to follow. Typical precisions are 10 cm and 1/10 s. The goal of this level is to produce trajectories for all the cybercars circulating in a given area. These trajectories have to be safe, most notably collision-free, but also efficient, i.e. deadlock-free.At the microscopic level, the cybercar's control moves along the trajectory and ensures that none of these collisions which couldn't have been foreseen at the higher levels occur.It should also be stressed that this framework is not top-down only. Each lower level can raise warnings to higher levels ; e.g. stopping before an unforeseen children raises a warning from the microscopic level, where it is detected, to the mesoscopic level, where new trajectories are calculated.In this paper, we focus on the mesoscopic level. More precisely, we present the study on a simple crossroads (X junction) of the concepts developed to deal in a general context. Several trajectory-generating algorithms are described and compared in terms of efficiency. One key element of these algorithms is the respect of the controllability constraints of the vehicles, for the actual vehicles to be able to follow the generated trajectories. A second key element is the management of the shared resources, i.e. the places on the junction where trajectories intersect.

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