John Vidler

It Bends But Would It Break? Topological Analysis of BGP Infrastructures in Europe

The Internet is often thought to be a model of resilience, due to a decentralised, organically-grown architecture. This paper puts this perception into perspective through the results of a security analysis of the Border Gateway Protocol (BGP) routing infrastructure. BGP is a fundamental Internet protocol and its intrinsic fragilities have been highlighted extensively in the literature. A seldom studied aspect is how robust the BGP infrastructure actually is as a result of nearly three decades of perpetual growth. Although global black-outs seem unlikely, local security events raise growing concerns on the robustness of the backbone. In order to better protect this critical infrastructure, it is crucial to understand its topology in the context of the weaknesses of BGP and to identify possible security scenarios. Firstly, we establish a comprehensive threat model that classifies main attack vectors, including but non limited to BGP vulnerabilities. We then construct maps of the European BGP backbone based on publicly available routing data. We analyse the topology of the backbone and establish several disruption scenarios that highlight the possible consequences of different types of attacks, for different attack capabilities. We also discuss existing mitigation and recovery strategies, and we propose improvements to enhance the robustness and resilience of the backbone. To our knowledge, this study is the first to combine a comprehensive threat analysis of BGP infrastructures withadvanced network topology considerations. We find that the BGP infrastructure is at higher risk than already understood, due to topologies that remain vulnerable to certain targeted attacks as a result of organic deployment over the years. Significant parts of the system are still uncharted territory, which warrants further investigation in this direction.

A Characterization of Actuation Techniques for Generating Movement in Shape-Changing Interfaces

ABSTRACT This article characterizes actuation techniques for generating movement in shape-changing displays with physically reconfigurable geometry. To date, few works in human–computer interaction literature provide detailed and reflective descriptions of the implementation techniques used in shape-changing displays. This hinders the rapid development of novel interactions as researchers must initially spend time understanding technologies before prototyping new interactions and applications. To bridge this knowledge gap, the authors propose a taxonomy that classifies actuator characteristics and simplifies the process for designers to select appropriate technologies that match their requirements for developing shape displays. They scope the investigation to linear actuators that are used in grid configurations. The taxonomy is validated by (a) examining current implementation techniques of motorized, pneumatic, hydraulic, magnetic, and shape-memory actuators in the literature, (b) constructing prototypes to address limited technical details and explore actuator capabilities in depth, (c) describing a use-case scenario through a case study that details the construction of a 10 × 10 actuator shape-display, and (d) a set of guidelines to aid researchers in selecting actuation techniques for shape-changing applications. The significance of their taxonomy is twofold. First, the authors provide an original contribution that enables HCI researchers to appropriately select actuation techniques and build shape-changing applications. This is situated amongst other past works that have investigated broader application scenarios such as a shape-changing vocabulary, a framework for shape transformations, material properties, and technical characteristics of various actuators. Second, they carry out in-depth investigations to validate their taxonomy and expand the knowledge of vertical actuation in shape-changing applications to enable rapid development.

Estimating node lifetime in interference environments

For commercial Wireless Sensor Network (WSNs) deployments it is necessary to estimate the network lifetime. It must be possible before network deployment to determine how long a network maintains operational before maintenance is required and batteries have to be replaced. Unfortunately, node lifetime is very dependent on the radio environment in which the node is operated. As we will demonstrate in this paper the node lifetime in a very busy radio environment can be up to 11 times shorter than in a quiet environment. WSNs employ duty-cycled communication protocols where receivers periodically sample the channel to determine if it has to remain active to receive a message. Radio interference triggers the receive mechanism causing an unnecessary wake-up which leads to an increase in a nodes energy consumption. In this paper we present a method for estimating node energy consumption in a target radio environment. We describe how to capture the essential characteristics of the radio environment and how to use this information to predict node lifetime. We demonstrate the usability of the proposed method using the well known WSN communication protocol ContikiMAC. Our evaluation comprising real-world scenarios shows that the proposed method is able to accurately predict node lifetime.