Showing papers by "Jon Crowcroft published in 2013"

Unikernels: library operating systems for the cloud

Abstract: We present unikernels, a new approach to deploying cloud services via applications written in high-level source code. Unikernels are single-purpose appliances that are compile-time specialised into standalone kernels, and sealed against modification when deployed to a cloud platform. In return they offer significant reduction in image sizes, improved efficiency and security, and should reduce operational costs. Our Mirage prototype compiles OCaml code into unikernels that run on commodity clouds and offer an order of magnitude reduction in code size without significant performance penalty. The architecture combines static type-safety with a single address-space layout that can be made immutable via a hypervisor extension. Mirage contributes a suite of type-safe protocol libraries, and our results demonstrate that the hypervisor is a platform that overcomes the hardware compatibility issues that have made past library operating systems impractical to deploy in the real-world.

Energy Management Techniques in Modern Mobile Handsets

Abstract: Managing energy efficiently is paramount in modern smartphones. The diverse range of wireless interfaces and sensors, and the increasing popularity of power-hungry applications that take advantage of these resources can reduce the battery life of mobile handhelds to few hours of operation. The research community, and operating system and hardware vendors found interesting optimisations and techniques to extend the battery life of mobile phones. However, the state of the art of lithium-ion batteries clearly indicates that energy efficiency must be achieved both at the hardware and software level. In this survey, we will cover the software solutions that can be found in the research literature between 1999 and May 2011 at six different levels: energy-aware operating systems, efficient resource management, the impact of users' interaction patterns with mobile devices and applications, wireless interfaces and sensors management, and finally the benefits of integrating mobile devices with cloud computing services.

RILAnalyzer: a comprehensive 3G monitor on your phone

Abstract: The popularity of smartphones, cloud computing, and the app store model have led to cellular networks being used in a completely different way than what they were designed for. As a consequence, mobile applications impose new challenges in the design and efficient configuration of constrained networks to maximize application's performance. Such difficulties are largely caused by the lack of cross-layer under- standing of interactions between different entities -applications, devices, the network and its management plane. In this paper, we describe RILAnalyzer, an open-source tool that provides mechanisms to perform network analysis from within a mobile device. RILAnalyzer is capable of recording low-level radio information and accurate cellular net- work control-plane data, as well as user-plane data. We demonstrate how such data can be used to identify previously overlooked issues. Through a small user study across four cellular network providers in two European countries we infer how different network configurations are in reality and explore how such configurations interact with application logic, causing network and energy overheads.

Fragmented social media: a look into selective exposure to political news

Abstract: The hypothesis of selective exposure assumes that people crave like-minded information and eschew information that conflicts with their beliefs, and that has negative consequences on political life. Yet, despite decades of research, this hypothesis remains theoretically promising but empirically difficult to test. We look into news articles shared on Facebook and examine whether selective exposure exists or not in social media. We find a concrete evidence for a tendency that users predominantly share like-minded news articles and avoid conflicting ones, and partisans are more likely to do that. Building tools to counter partisanship on social media would require the ability to identify partisan users first. We will show that those users cannot be distinguished from the average user as the two subgroups do not show any demographic difference.

Staying online while mobile: the hidden costs

Abstract: Mobile phones in the 3G/4G era enable us to stay connected not only to the voice network, but also to online services like social networks. In this paper, we study the energy and network costs of mobile applications that provide continuous online presence (e.g. WhatsApp, Facebook, Skype). By combining measurements taken on the mobile and the cellular access network, we reveal a detailed picture of the mechanisms selected to implement online presence, along with their effect on handset energy consumption and network signaling traffic. We are surprised to find that simply having idle online presence apps on a mobile (that maintain connectivity in the background, with no user interaction) can drain the handset battery nine times more quickly. This high cost is partly due to online presence apps that are excessively ``chatty'', in particular when their design philosophy stems from a similar desktop version. However, we also find that the cost of background app traffic is disproportionately large because of cross-layer interactions in which the traffic unintentionally triggers the promotion of cellular network states. Our experiments show that both of these effects can be overcome with careful implementation. We posit that a two-way push notification system, with messages being sent at a low (regular) frequency and low volume by a network-aware sender, can alleviate many of the costs.

Psychological maps 2.0: a web engagement enterprise starting in London

Abstract: Planners and social psychologists have suggested that the recognizability of the urban environment is linked to people's socio-economic well-being. We build a web game that puts the recognizability of London's streets to the test. It follows as closely as possible one experiment done by Stanley Milgram in 1972. The game picks up random locations from Google Street View and tests users to see if they can judge the location in terms of closest subway station, borough, or region. Each participant dedicates only few minutes to the task (as opposed to 90 minutes in Milgram's). We collect data from 2,255 participants (one order of magnitude a larger sample) and build a recognizability map of London based on their responses. We find that some boroughs have little cognitive representation; that recognizability of an area is explained partly by its exposure to Flickr and Foursquare users and mostly by its exposure to subway passengers; and that areas with low recognizability do not fare any worse on the economic indicators of income, education, and employment, but they do significantly suffer from social problems of housing deprivation, poor living conditions, and crime. These results could not have been produced without analyzing life off- and online: that is, without considering the interactions between urban places in the physical world and their virtual presence on platforms such as Flickr and Foursquare. This line of work is at the crossroad of two emerging themes in computing research - a crossroad where "web science" meets the "smart city" agenda.

Opportunistic message routing using multi-layer social networks

Abstract: In opportunistic networks, the nodes usually exploit a contact opportunity to perform hop-by-hop routing, since an end-to-end path between the source node and destination node may not exist. Most social-based routing protocols use social information extracted from real-world encounter networks to select an appropriate message relay. A protocol based on encounter history, however, takes time to build up a knowledge database from which to take routing decisions. An opportunistic routing protocol which extracts social information from multiple social networks, can be an alternative approach to avoid suboptimal paths due to partial information on encounters. While contact information changes constantly and it takes time to identify strong social ties, online social network ties remain rather stable and can be used to augment available partial contact information. In this paper, we propose a novel opportunistic routing approach, called ML-SOR (Multi-layer Social Network based Routing), which extracts social network information from multiple social contexts. To select an effective forwarding node, ML-SOR measures the forwarding capability of a node when compared to an encountered node in terms of node centrality, tie strength and link prediction. These metrics are computed by ML-SOR on different social network layers. Trace driven simulations show that ML-SOR, when compared to other schemes, is able to deliver messages with high probability while keeping overhead ratio very small.

LCD-Net: lowest cost denominator networking

Abstract: "The Internet is for everyone" claims Vint Cerf, the father of the Internet via RFC 3271. The Internet Society's recent global Internet survey reveals that the Internet should be considered as a basic human birth right. We strongly agree with these and believe that basic access to the Internet should be made free, at least to access the essential services. However the current Internet access model, which is governed by market economics makes it practically infeasible for enabling universal access especially for those with socio-economic barriers. We see enabling benevolence in the Internet (act of sharing resources) as a potential solution to solve the problem of digital exclusion caused due to socio-economic barriers. In this paper, we propose LCD-Net: Lowest Cost Denominator Networking, a new Internet paradigm that architects multi-layer resource pooling Internet technologies to support benevolence in the Internet. LCD-Net proposes to bring together several existing resource pooling Internet technologies to ensure that users and network operators who share their resources are not affected and at the same time are incentivised for sharing. The paper also emphasizes the need to identify and extend the stakeholder value chain to ensure such benevolent access to the Internet is sustainable.

Why Do I Retweet It? An Information Propagation Model for Microblogs

Abstract: Microblogging platforms are Web 2.0 services that represent a suitable environment for studying how information is propagated in social networks and how users can become influential. In this work we analyse the impact of the network features and of the users' behaviour on the information diffusion. Our analysis highlights a strong relation between the level of visibility of a message in the flow of information seen by a user and the probability that the user further disseminates the message. In addition, we also highlight the existence of other latent factors that impact on the dissemination probability, correlated with the properties of the user that generated the message. Considering these results we define an information propagation model that generates information cascades (i.e. flows of messages propagated from user to user) whose statistical properties match empirical observations.

Understanding and decreasing the network footprint of catch-up tv

Abstract: "Catch-up", or on-demand access of previously broadcast TV content over the public Internet, constitutes a significant fraction of peak time network traffic. This paper analyses consumption patterns of nearly 6 million users of a nationwide deployment of a catch-up TV service, to understand the network support required. We find that catch-up has certain natural scaling properties compared to traditional TV: The on-demand nature spreads load over time, and users have much higher completion rates for content streams than previously reported. Users exhibit strong preferences for serialised content, and for specific genres. Exploiting this, we design a Speculative Content Offloading and Recording Engine (SCORE) that predictively records a personalised set of shows on user-local storage, and thereby offloads traffic that might result from subsequent catch-up access. Evaluations show that even with a modest storage of ~32GB, an oracle with complete knowledge of user consumption can save up to 74% of the energy, and 97% of the peak bandwidth compared to the current IP streaming-based architecture. In the best case, optimising for energy consumption, SCORE can recover more than 60% of the traffic and energy savings achieved by the oracle. Optimising purely for traffic rather than energy can reduce bandwith by an additional 5%.

When assistance becomes dependence: characterizing the costs and inefficiencies of A-GPS

Abstract: Location based services are a vital component of the mobile ecosystem. Among all the location technologies used behind the scenes, A-GPS (Assisted-GPS) is considered to be the most accurate. Unlike standalone GPS systems, A-GPS uses network support to speed nup position fix. However, it can be a dangerous strategy due to varying cell conditions which may impair performance, sometimes potentially neglecting the expected benefits of the original design. We present the characterization of the accuracy, location acquisition speed, energy cost, and network dependency of the state of the art A-GPS receivers shipped in popular mobile devices. Our analysis is based on active measurements, an exhaustive on-device analysis, and cellular traffic traces processing. The results reveals a number of inefficiencies as a result of the strong dependence on the cellular network to obtain assisting data, implementation, and integration problems.

Why individuals seek diverse opinions (or why they don't)

Abstract: Fact checking has been hard enough to do in traditional settings, but, as news consumption is moving on the Internet and sources multiply, it is almost unmanageable. To solve this problem, researchers have created applications that expose people to diverse opinions and, as a result, expose them to balanced information. The wisdom of this solution is, however, placed in doubt by this paper. Survey responses of 60 individuals in the UK and South Korea and in-depth structured interviews of 10 respondents suggest that exposure to diverse opinions would not always work. That is partly because not all individuals equally value opinion diversity, and mainly because the same individual benefits from it only at times. We find that whether one looks for diverse opinions largely depends on three factors--one's prior convictions, emotional state, and social context.

Smart Signage: A Draggable Cyber-Physical Broadcast/Multicast Media System

Abstract: Digital displays, as the replacement of traditional static signs, have gained increasing popularity for out-of-home advertising. Latest advancements in smartphone, wireless communication, and digital display technologies make it possible to design new interactive signage systems linking the digital content with the physical digital displays. Although recent studies have demonstrated the trend of cyber-physical interaction, they are not generally scalable for multiple users, and none of them support interaction with multiple displays in one location. Smart Signage, a “draggable” cyber-physical broadcast/multicast (B/M) media system is proposed in this paper. With a novel cyber-physical B/M protocol that synchronizes the content on the digital displays with the smartphones, it supports one-to-many interaction by allowing multiple users acquiring content from one display with a “dragging” hand gesture. With the embedded display orientation information in the same protocol, Smart Signage supports many-to-many interaction by allowing users obtaining content from the digital display they are pointing at with their smartphones. Users' quality of experience, which is characterized by the response time, is carefully studied in this paper to guarantee the performance of this cyber-physical interactive display system.

Bridging the gap between internet standardization and networking research

Abstract: The participation of the network research community in the Internet Standards Development Organizations (SDOs) has been relatively low over the recent years, and this has drawn attention from both academics and industry due to its possible negative impact. The reasons for this gap are complex and extend beyond the purely technical. In this editorial we share our views on this challenge, based on the experience we have obtained from joint projects with universities and companies. We highlight the lessons learned, covering both successful and under-performing cases, and suggest viable approaches to bridge the gap between networking research and Internet standardization, aiming to promote and maximize the outcome of such collaborative endeavours.

Virtual Public Networks

Abstract: Universal access to Internet is crucial. Several initiatives have recently emerged to enable wider access to the Internet. Public Access WiFi Service (PAWS) enables free Internet access to all and is based on Lowest Cost Denominator Networking (LCDNet) -- a set of network techniques that enable users to share their home broadband network with the public. LCDNet takes advantage of the available unused capacity in home broadband networks and allows Less-than-Best Effort (LBE) access to these resources. LCDNet can enable third-party stakeholders, such as local governments, to setup, configure and operate home networks for public Internet access in cooperation with Internet Service Providers. Software-defined networking (SDN) creates new opportunities for the remote configuration and management of such networks at large scale. In this paper, we present Virtual Public Networks (VPuN), home networks created, deployed and managed through an evolutionary SDN control abstraction. This offers more flexibility to users and network operators, allowing them to share and control the network, while providing opportunities for new stakeholders to emerge as virtual network operators.

Trevi: watering down storage hotspots with cool fountain codes

Abstract: Datacenter networking has brought high-performance storage systems' research to the foreground once again. Many modern storage systems are built with commodity hardware and TCP/IP networking to save costs. In this paper, we highlight a group of problems that are present in such storage systems and which are all related to the use of TCP. As an alternative, we explore Trevi: a fountain coding-based approach for distributing I/O requests that overcomes these problems while still efficiently scheduling resources across both networking and storage layers. We also discuss how receiver-driven flow and congestion control, in combination with fountain coding, can guide the design of Trevi and provide a viable alternative to TCP for datacenter storage.

Critical regions and region-disjoint paths in a network

Abstract: Due to the importance of communication networks to society, it is pertinent that these networks can withstand failures. Improving the robustness of a network usually requires installing redundant resources, which is very costly. Network providers are consequently less inclined to take robustness measures against failures that are unlikely to manifest, like several failures coinciding simultaneously in different geographic regions of their network. Protecting against single regional failures is more realistic. Network robustness, in terms of connectivity properties, also requires survivability algorithms to quickly reroute traffic affected by a network failure. In this paper, we consider a network embedded in a plane and study the problem of finding a circular region with radius r in that plane that would cause the biggest network degradation if all nodes within that particular region were to be destroyed. We propose a polynomial time algorithm for finding such critical regions. In addition, we develop a region-aware network augmentation technique to decrease the impact of a critical region failure. We subsequently consider the region-disjoint paths problem, which asks for two paths with minimum total weight between a source (s) and a destination (d) that cannot both be cut by a single circular regional failure of radius r (unless that failure includes s and d). We prove that the region-disjoint paths problem is NP-hard and propose and evaluate a heuristic algorithm for it.

QoI-Aware Energy-Efficient Participatory Crowdsourcing

Abstract: Today's smartphones not only serve as a means of personal communication device, but are also fundamentally transforming the traditional understanding of crowdsourcing to an emerging type of participatory, task-oriented applications. It aims to support the so-called Citizen Science efforts for knowledge discovery, to understand the human behavior and measure/evaluate their opinions. In this paper, to facilitate the above scenarios, we propose a novel energy-efficient participatory crowdsourcing framework that meets the quality-of-information (QoI) requirements of the request in a distributed manner. Specifically, we extend the traditional framework of Gur Game for distributed decision-making to recommend the level of information contribution for each participant, by merging the multiple automaton chains into a single chain with multiple steady states. We evaluate the proposed scheme under the MIT social evolution data set, where the QoI requirements of the request are successfully achieved, with a satisfactory level of energy consumption fairness among participants, of negligible computational complexity. Finally, we explore the impact of community structure on the proposed algorithm, and propose a feasible method to facilitate the local data aggregation.

Information centric delay tolerant networking: an internet architecture for the challenged

Abstract: Enabling universal Internet access is one of the key issues that is currently being addressed globally. However the existing Internet architecture is seriously challenged to ensure universal service provisioning. This technical report puts forth our vision to make the Internet more accessible by architecting a universal communication architectural framework combining two emerging architecture and connectivity approaches: Information Centric Networking (ICN) and Delay/Disruption Tolerant Networking (DTN). Such an unified architecture will aggressively seek to widen the connectivity options and provide flexible service models beyond what is currently pursued in the game around universal service provisioning.

Smart Signage: An Interactive Signage System with Multiple Displays

Abstract: Digital signs (e.g. electronic billboards), as the replacement of traditional static signs (e.g. paper posters), have gained increasing popularity, especially for out-of-home advertising. The pervasiveness of the smartphones makes it possible to implement new interactive signage systems for advertising purpose. A new drag gable cyber-physical broadcast/multicast media system, Smart Signage, is proposed in our previous work. It allows multiples users simultaneously obtaining the displayed content with an intuitive ``dragging" hand gesture. With the increasing number of deployed digital signs, it is possible that there are multiple signs in one location. In this paper, a new approach is proposed using the existing Smart Signage infrastructure to allow smartphones to interact with multiple digital signs in one location. This approach differentiates signs by the orientations of the signage displays, which are measured by smartphone-embedded orientation sensors. A user can interact with the intended sign by simply pointing his/her smartphone at the target signage display. With this new approach, Smart Signage successfully extends from one-to-many interaction to many-to-many interaction.

Is SDN the de-constraining constraint of the future internet?

Abstract: Dagstuhl hosted a three-day seminar on the Future Internet on March 25-27, 2013. At the seminar, about 40 invited researchers from academia and industry discussed the promises, approaches, and open challenges of the Future Internet. This report gives a general overview of the presentations and outcomes of discussions of the seminar.

Path-Moose : A Scalable All-Path Bridging Protocol

Abstract: This paper describes Path-Moose, a scalable tree-based shortest path bridging protocol. Both ARP-Path and Path-Moose protocols belong to a new category of bridges that we name All-path, because all paths of the network are explored simultaneously with a broadcast frame distributed over all network links to find a path or set a multicast tree. Path-Moose employs the ARP-based low latency routing mechanism of the ARP-Path protocol on a bridge basis instead of a per-single-host basis. This increases scalability by reducing forwarding table entries at core bridges by a factor of fifteen times for big data center networks and achieves a faster reconfiguration by an approximate factor of ten. Reconfiguration time is significantly shorter than ARP-Path (zero in many cases) because, due to the sharing of network paths by the hosts connected to same edge bridges, when a host needs the path it has already been recovered by another user of the path. Evaluation through simulations shows protocol correctness and confirms the theoretical evaluation results. Copyright © 2013 The Institute of Electronics, Information and Communication Engineers.

Decentralized Systems for Privacy Preservation (Dagstuhl Seminar 13062)

Abstract: This report documents the program and the outcomes of Dagstuhl Seminar 13062 "Decentralized Systems for Privacy Preservation". In recent years, a number of concerns have risen about the existence of large, organizationally centralized online services (cloud services, online social networks, repositories, etc). The concerns include risks to users' data from organizational failures and threats to user privacy. In this seminar, the organizers brought together a somewhat more diverse collection of theoreticians and practitioners from industry and academia including social scientists and economists. In keeping with the nature of the interdisciplinary attendees, the organizers also attempted a seminar organization structure intended to promote innovative, cross-discipline working. The results were mixed: some clear agenda setting outputs emerged with some less clear ones.

Low power optical transceivers for switched interconnect networks

Abstract: The power-consumption of network equipment is under ever-increasing scrutiny. As part of an ensemble project seeking to reduce power-consumption within data-centers1, this work focuses on reducing the power consumption of photonic transceivers for future fast power gated and/or optical switching networks. Utilising an open-source toolkit, we show that Serializer/Deserializer (SERDES) dominates power consumption of traditional optical transceivers. This result has particular implications for the modulation format of future interconnects. At 25 Gb/s line rate, SERDES blocks of PAM-16 and 4-wavelength WDM are shown to have 53% and 79% lower power respectively compared with SERDES of serial NRZ as well as reduced power gating restoration time and energy.

Traditional media seen from social media

Abstract: With the advent of social media services, media outlets have started reaching audiences on social-networking sites. On Twitter, users actively follow a wide set of media sources, form interpersonal networks, and propagate interesting stories to their peers. These media subscription and interaction patterns, which had previously been hidden behind media corporations' databases, offer new opportunities to understand media supply and demand on a large scale. Through a map that connects 77 media outlets based on Twitter subscription patterns, we are able to answer a variety of questions: to what extent New York Times and the Wall Street Journal readers overlap? Are they competitors or potential collaborators? Are people who know each other more likely to subscribe to similar outlets?

Bridge Networking Research and Internet Standardization: Case Study on Mobile Traffic Offloading and IPv6 Transition Technologies

Abstract: The gap between networking research communities and Internet standardization organizations (SDOs) has been growing over the years, which has drawn attention from both academic and industrial sides due to its detrimental impact. The reason behind this widening gap is complex and typically beyond the mere technology ground. In this position paper we share our perspectives toward this challenge based on our hands-on experience obtained from joint projects with universities and companies. We highlight the lessons learned, covering both successful and under-performed cases, and further suggest viable solutions to bridge the gap between networking research and Internet standardization, aiming to promote and maximize the outcome of such collaborative endeavours.

Task Farming in Crowd Computing

Abstract: This chapter contains sections titled: Introduction Ideal Parallelism Model Task Farming Socially Aware Task Farming Related Work Conclusions and Future Work References