An analysis of congestion controls in centralized control systems

International audienceThis article studies different congestion control methods applied to a centralized control system, consisting in several sensors/actuators and one controller. Sensors/actuators are linked to the controller through an IP network. Depending on the data exchanged, the network can be congested. In such case, the congestion control used by data exchange becomes important. We evaluate four congestion control methods used by three classical transport protocols, UDP, TCP and DCCP. This evaluation uses ns2 network simulator. Results on a centralised control system show that TCP and DCCP offer a good tradeoff on reliability vs. throughput, whereas UDP has best results provided that the network is well configured

A Security Supervision System for Hybrid Networks

The traditional way of protecting networks and applications with e.g., firewalls and encryption, is no longer sufficient to protect effectively emerging hybrid wired-cum-wireless networks including ad hoc networks. Intrusion detection mechanisms should be coupled with preventive measures so as to identify unauthorised abuses. To this end, we propose a novel Hybrid Distributed Security Operation Center (HDSOC) which collects logs that are generated by any application/service, layer of the protocol stack or resource (e.g., router), providing a global view of the supervised system based on which complex and distributed intrusions can be detected. Our HDSOC further (i) distributes its capabilities and (ii) provides extensive coordination capabilities for guarantying that both the networks and the HDSOC components do not constitute isolated entities largely unaware of each others

A framework to Calibrate a MEMS Sensor Network

International audienceThe Smart Surface project aims at designing an integrated micro-manipulator based on an array of micromodules connected with a 2D array topology network. Each micromodule comprises a sensor, an actuator and a processing unit. One of the aims of the processing unit is to differentiate the shape of the part that is put on top of the Smart Surface. From a set of shapes this differentiation is done through a distributed algorithm that we call a criterion. The article presents Sensor Network Calibrator (SNC), a calibrator which allows to parametrize the Smart Surface and to determine the necessary number of sensors required by our Smart Surface. The tests will show that SNC is of great importance for choosing the number of sensors, and therefore to determine the size of the sensors grid

VAAL, Video Adaptation at Application Layer and Experiments using DCCP

International audienceMore and more high definition and high quality videos are nowadays stored on Internet but they are not accessible for everybody because high and stable bandwidth is needed to stream them. A lower bitrate encoding is usually chosen but it leads to lower quality too. A solution is to use a TCP-friendly transport protocol and let the application itself choose for each user the bitrate of the video which matches the network bandwidth. This paper presents VAAL, a simple and efficient method designed to ameliorate user video experience. It involves only the application layer on the sender. The main idea of VAAL is that the sender application monitors the network conditions by checking transport protocol buffer overflows and adapts the video bitrate accordingly. Experimental results show that the video adaptation using VAAL performs very well compared to the currently widely-used static encoding

A taxonomy of the parameters used by decision methods for adaptive video transmission

International audienceNowadays, video data transfers account for much of the Internet traffic and a huge number of users use this service on a daily base. Even if videos are usually stored in several bitrates on servers, the video sending rate does not take into account network conditions which are changing dynamically during transmission. Therefore, the best bitrate is not used which causes sub-optimal video quality when the video bitrate is under the available bandwidth or packet loss when it is over it. One solution is to deploy adaptive video, which adapts video parameters such as bitrate or frame resolution to network conditions. Many ideas are proposed in the literature, yet no paper provides a global view on adaptation methods in order to classify them. This article fills this gap by discussing several adaptation methods through a taxonomy of the parameters used for adaptation. We show that, in the research community, the sender generally takes the decision of adaptation whereas in the solutions supported by major current companies the receiver takes this decision. We notably suggest, without evaluation, a valuable and realistic adaptation method, gathering the advantages of the presented methods

Large scale MEMS robots cooperative map building based on realistic simulation of nano-wireless communications

International audienceThe Claytronics project has produced interesting hardware components like cylindric micro-robots called catoms and software models to enable the concept of programmable matter. One application is the use of several catoms linked together so that they can " walk ". These walkers can explore an area and thanks to electromagnetic wireless nano-networks, they can communicate with each other sharing the map of the place to explore. In this paper, we study the different parameters influencing the transmission quality of the map to a sink which uses both traditional wireless and wireless nano-communication networks

{EcnLD}, {ECN Loss Differentiation} to optimize the performance of transport protocols on wireless networks

International audienceOne major yet unsolved problem in wired-cum-wireless networks is the classification of losses, which can be due either to wireless temporary interferences or to network congestion. The transport protocol response to losses has to be different for these two cases. If the transmission uses existing protocols like TCP, the losses will always be classified as congestion losses by the data sender, causing reduced throughput. In wired networks, ECN (Explicit Congestion Notification) can be used to control the congestion through active queue management such as RED (Random Early Detection). It can also be used to resolve the transport protocol misreaction on wireless networks. This paper proposes a loss differentiation method (EcnLD), based on ECN signaling and RTT, and applied to TCPlike. TCPlike is one of the two current congestion controls present in the new transport protocol DCCP (Datagram Congestion Control Protocol). Our results indicate that EcnLD is a good approach to optimize congestion control and therefore increase the performance of transport protocols over wireless networks

Oscillation-free video adaptation at application layer on server side and experiments using DCCP

International audienceNowadays, video data transfers account for much of the Internet bandwidth and a huge number of users use it daily. However, despite its apparent interest, video streaming is still done in a suboptimal manner. Indeed, more and more high-definition and high-quality videos are nowadays stored on Internet but they are not accessible for everybody because a high and stable bandwidth is needed to stream them; also, during videoconferencing, the highest possible quality often exceeds the available bandwidth. Hence, a lower bitrate encoding is usually chosen but it leads to lower quality and network under-utilization too. This paper presents Video Adaptation at Application Layer (VAAL), a simple and efficient method designed to use optimally network resources and to ameliorate user video experience. It involves only the application layer on the server. The main idea of VAAL is that it checks Transmission Control Protocol-friendly transport protocol buffer overflows and adapts the video bitrate accordingly; as a result, the bitrate constantly matches the network bandwidth. It can be used together with Zigzag Avoidance Algorithm (ZAAL), a novel algorithm aiming to avoid quality oscillations. Experimental results show that the video adaptation using VAAL+ZAAL performs much better compared with the currently widely used static encoding, making it a strong candidate for hard real-time video streaming

Simulation to help calibration of a {MEMS} Sensor Network

International audienceThe Smart Surface project aims at designing an integrated micro-manipulator based on an array of micromodules connected with a 2D array topology network. Each micromodule comprises a sensor, an actuator and a processing unit. One of the aims of the processing unit is to differentiate the shape of the part that is put on top of the Smart Surface. From a set of shapes this differentiation is done through a distributed algorithm that we call a criterion. The article presents Sensor Network Calibrator (SNC), a calibrator which allows to parametrize the Smart Surface and to determine the necessary number of sensors required by our Smart Surface. The tests will show that SNC is of great importance for choosing the number of sensors, and therefore to determine the size of the sensors grid