Shortcuts through Colocation Facilities

Network overlays, running on top of the existing Internet substrate, are of perennial value to Internet end-users in the context of, e.g., real-time applications. Such overlays can employ traffic relays to yield path latencies lower than the direct paths, a phenomenon known as Triangle Inequality Violation (TIV). Past studies identify the opportunities of reducing latency using TIVs. However, they do not investigate the gains of strategically selecting relays in Colocation Facilities (Colos). In this work, we answer the following questions: (i) how Colo-hosted relays compare with other relays as well as with the direct Internet, in terms of latency (RTT) reductions; (ii) what are the best locations for placing the relays to yield these reductions. To this end, we conduct a large-scale one-month measurement of inter-domain paths between RIPE Atlas (RA) nodes as endpoints, located at eyeball networks. We employ as relays Planetlab nodes, other RA nodes, and machines in Colos. We examine the RTTs of the overlay paths obtained via the selected relays, as well as the direct paths. We find that Colo-based relays perform the best and can achieve latency reductions against direct paths, ranging from a few to 100s of milliseconds, in 76% of the total cases; 75% (58% of total cases) of these reductions require only 10 relays in 6 large Colos.Comment: In Proceedings of the ACM Internet Measurement Conference (IMC '17), London, GB, 201

Three Lenses on Lurking: Making Sense of Digital Silence

In this chapter, the authors provide a critical exploration of the concept of lurking in online learning spaces through a phenomenological inquiry. The authors begin from a position that lurking is often misunderstood – or perhaps not understood – in education, and that the term itself is quite problematic, as it is typically applied to a disparate range of behaviors by those who perceive them as problematic. The authors then propose three heuristic lenses to make sense of lurking behaviors: lurking as troublesome, lurking as ordinary, and lurking as political. These lenses demonstrate that lurking behaviors not only stem from a range of different motivations but are also situated in a variety of contexts, that is, lurking is personal and contextual. The authors’ aim is not to define or redefine lurking for readers but to provide a critical analysis of what digital silence might mean for their students based on their contextual experience and in the light of critical literature. The authors invite readers to be part of the reflexive analysis by considering what lurking might mean in their own teaching contexts

System of Systems Perspective on Risk: Towards a Unified Concept

Many systems and projects that concern systems engineers, engineering managers, and business managers today can be defined as system of systems (SoS), which are described as ambiguous, uncertain and dynamic, among others. In addition to the traditional view on risk identification, analysis and management, the concept of risk should be considered with respect to these systems of systems. The purpose of this paper is to analyse both fundamental concepts and recent publications in system of systems, business and engineering management, as well as risk analysis, modelling, and management for the purpose of better describing the concept of risk with respect to system of systems. The ultimate goal is to provide engineering and business managers the necessary perspective on the concept of risk and its management for the next generation of systems – including various descriptions of risk and discussion of the relevance of properties of system of systems to sustainable management of risks in engineered systems. To achieve a truly sustainable management of risk, there has to be a change in paradigm from a traditional description of risk to that of a more holistic perspective

Recentering open for those at the margins: three lenses on lurking

The group presenting this session was formed through a serendipitous participation in a ‘slow chat’ (#HEdigID) on the topic of OEP. The chat went on long beyond its official end, and we realized that the #HEdigID network was larger than we had observed. It included ‘invisible’ participants who were simply listening, or tuning in once in a while. We began to discuss the practice of ‘lurking’ and the idea of ‘the lurker’. The group conversation which followed revealed some of the complexities of lurking behaviours. What (or who) is a “lurker”? Do we need to rethink what participation means? Why some learners are visible, and others less visible or maybe invisible, remaining on the margins of online and networked learning? Do we need to recenter participation in open spaces – to bring in those who appear to choose to stay on the periphery? It seems there is a need to turn a critical lens onto our assumptions, and think about how ‘privileging the visible’ may constrain and exclude more invisible learners equally interested in learning (Honeychurch et al., 2017; Popovac, M., & Fullwood, C., 2018). Against a prior emphasis on transmission of knowledge, designing for learning in today’s open environments is often ‘designing for participation’. Has the pendulum now swung too far in this direction, such that those who are said to ‘lurk’ are dismissed, derided, or at best, understood through a deficit model? Our proposed lenses on lurking as troublesome, political and ordinary, suggest alternative ways of understanding lurking behaviours, but do not provide an obvious answer to the question of how to engage the lurking learner – or whether the lurker must be engaged. What does learner agency look like in this context? Can we truly design for all? Or should we design for participation – and let lurkers lurk? We are seeking input from participants in online learning spaces – current students or teachers or people who have other roles or with an interest in learning in open environments. Through the discussion/activity, further insights into both the ‘lurker experience’ and inclusive learning design will emerge

Shape control of QDs studied by cross-sectional scanning tunneling microscopy

In this cross-sectional scanning tunneling microscopy study we investigated various techniques to control the shape of self-assembled quantum dots (QDs) and wetting layers (WLs). The result shows that application of an indium flush during the growth of strained InGaAs/GaAs QD layers results in flattened QDs and a reduced WL. The height of the QDs and WLs could be controlled by varying the thickness of the first capping layer. Concerning the technique of antimony capping we show that the surfactant properties of Sb result in the preservation of the shape of strained InAs/InP QDs during overgrowth. This could be achieved by both a growth interrupt under Sb flux and capping with a thin GaAsSb layer prior to overgrowth of the uncapped QDs. The technique of droplet epitaxy was investigated by a structural analysis of strain free GaAs/AlGaAs QDs. We show that the QDs have a Gaussian shape, that the WL is less than 1 bilayer thick, and that minor intermixing of Al with the QDs takes place.Comment: 7 pages, 10 figure