Improving Dependability of Networks with Penalty and Revocation Mechanisms

Both malicious and non-malicious faults can dismantle computer networks. Thus, mitigating faults at various layers is essential in ensuring efficient and fair network resource utilization. In this thesis we take a step in this direction and study several ways to deal with faults by means of penalties and revocation mechanisms in networks that are lacking a centralized coordination point, either because of their scale or design. Compromised nodes can pose a serious threat to infrastructure, end-hosts and services. Such malicious elements can undermine the availability and fairness of networked systems. To deal with such nodes, we design and analyze protocols enabling their removal from the network in a fast and a secure way. We design these protocols for two different environments. In the former setting, we assume that there are multiple, but independent trusted points in the network which coordinate other nodes in the network. In the latter, we assume that all nodes play equal roles in the network and thus need to cooperate to carry out common functionality. We analyze these solutions and discuss possible deployment scenarios. Next we turn our attention to wireless edge networks. In this context, some nodes, without being malicious, can still behave in an unfair manner. To deal with the situation, we propose several self-penalty mechanisms. We implement the proposed protocols employing a commodity hardware and conduct experiments in real-world environments. The analysis of data collected in several measurement rounds revealed improvements in terms of higher fairness and throughput. We corroborate the results with simulations and an analytic model. And finally, we discuss how to measure fairness in dynamic settings, where nodes can have heterogeneous resource demands

How Penalty Leads to Improvement: a Measurement Study of Wireless Backoff

Despite much theoretical work, different modifications of backoff protocols in 802.11 networkslack empirical evidence demonstrating their real-life performance. To fill the gap we have set out to experiment with performance of exponential backoff by varying its backoff factor. Despite the satisfactory results for throughput, we have witnessed poor fairness manifesting in severe capture effect. The design of standard backoff protocol allows already successful nodes to remain successful, giving little chance to those nodes that failed to capture the channel in the beginning. With this at hand, we ask a conceptual question: Can one improve the performance of wireless backoff by introducing a mechanism of self-penalty, when overly successful nodes are penalized with big contention windows? Our real-life measurements using commodity hardware demonstrate that in many settings such mechanism not only allows to achieve better throughput, but also assures nearly perfect fairness. We further corroborate these results with simulations and an analytical model. Finally, we present a backoff factor selection protocol which can beimplemented in access points to enable deployment of the penalty backoff protocol to consumer devices.Non Peer reviewe

Distributed User Authentication in Wireless LANs

Abstract—An increasing number of mobile devices, including smartphones, use WLAN for accessing the Internet. Existing WLAN authentication mechanisms are either disruptive, such as presenting a captive web page prompting for password, or unreliable, enabling a malicious user to attack a part of operator’s infrastructure. In this paper, we present a distributed authentication architecture for WLAN users providing instant network access without manual interactions. It supports terminal mobility across WLAN access points with the Host Identity Protocol (HIP), at the same time protecting the operator’s infrastructure from external attacks. User data sent over a wireless link is protected by the IPsec ESP protocol. We present our architecture design and implementation experience on two OpenWrt WLAN access points, followed by measurement results of the working prototype. The system is being deployed into pilot use in the city-wide panOULU WLAN. I

Extracurricular sports and recreation activities as a component of the cognitive activity development of primary school children

Analysis of scientific and methodological sources on the main positions of development and improvement of physical culture in general education institutions shows that it is necessary to pay attention to the development of schoolchildren cognitive abilities through project activities, interactive game technologies, and personal participation in sports events. Extracurricular activities are an expanded space of upbringing and education, it creates additional opportunities for self-realization and self-knowledge, their capabilities through sports and recreation activities. This article describes the methodology of sports and recreation classes held outside of school hours with the introduction of game sports (basketball, floorball), interactive technologies. The content of the proposed methodology is traditional. It consists of mastering knowledge methods, improving motor skills and developing physical qualities. They are formed thanks to the proposed interactive game technologies and tasks for the intellectual abilities development. The article discusses the possible conditions of sports and recreation activities in general education institutions that ensure a more successful development of younger students cognitive activity. Analysis and generalization of scientific and methodological literature, testing, questionnaires, pedagogical experiment, methods of mathematical statistics. The experimental method was implemented in junior classes and was conducted as part of extracurricular sports and recreation activities in accordance with the Federal state educational standard. The proposed forms and methods of organizing basketball and floorball classes with the inclusion of interactive game technologies and tasks for the development of intellectual abilities increased the cognitive activity of younger schoolchildren. The results of the pedagogical experiment showed the expediency and effectiveness of the proposed method. It provides a holistic approach in the framework of extracurricular sports and recreation activities to improve the indicators of younger schoolchildren cognitive abilities