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Jon Crowcroft

Bio: Jon Crowcroft is an academic researcher from University of Cambridge. The author has contributed to research in topics: The Internet & Multicast. The author has an hindex of 87, co-authored 672 publications receiving 38848 citations. Previous affiliations of Jon Crowcroft include Memorial University of Newfoundland & Information Technology University.


Papers
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Journal ArticleDOI
TL;DR: This work model the behavior of scoped-flooding by the help of a theoretical model on network growth and utility and proposes to exploit the resulting divergence in availability along with the routers’ topological properties to fine tune the flooding radius.
Abstract: Scoped-flooding is used for content discovery in a broad networking context and it has significant impact on the design of caching algorithms in a communication network. Despite its wide usage, a thorough analysis on how scoped-flooding affects a network’s performance, e.g., caching and content discovery efficiency, is missing. To develop a better understanding, we first model the behavior of scoped-flooding by the help of a theoretical model on network growth and utility. Next, we investigate the effects of scoped-flooding on various topologies in information-centric networks (ICNs). Using the proposed ring model, we show that flooding can be constrained within a small neighborhood to achieve most of the gains which come from areas with relatively low growth rate, i.e., the network edge. We also study two flooding strategies and compare their behaviors. Given that caching schemes favor more popular items in competition for cache space, popular items are expected to be stored in diverse parts of the network compared to the less popular items. We propose to exploit the resulting divergence in availability along with the routers’ topological properties to fine tune the flooding radius. Our results shed light on designing both efficient content discovery mechanism and effective caching algorithms for future ICN.

8 citations

Proceedings ArticleDOI
14 Jul 2015
TL;DR: It is described how more accurate models for data-center systems can be designed and used in order to create an evaluation framework that allows the exploration of the energy-performance trade-off in VM consolidation strategies with enhanced fidelity.
Abstract: In this paper we challenge the common evaluation practices used in Virtual Machine (VM) consolidation, such as simulation and small testbeds, which fail to capture the fundamental trade-off between energy consumption and performance. We identify a number of over-simplifying assumptions which are typically made about the energy consumption and performance characteristics of modern networked systems. In response, we describe how more accurate models for data-center systems can be designed and used in order to create an evaluation framework that allows the exploration of the energy-performance trade-off in VM consolidation strategies with enhanced fidelity.

8 citations

Proceedings ArticleDOI
17 Nov 2002
TL;DR: The article compiles the security issues of a dynamic networked system where electronic tariffs and service level agreement (SLA) structures are distributed among service providers and customers and a set of security protocols is outlined.
Abstract: In the near future, billing for network services will not only be concerned with time or volume based accounting but also in ways of measuring the quality of the service provided. Dynamic price schemes, such as congestion-based charging, have been proposed. In some of these models, the charging infrastructure relies on the distribution of electronic tariffs to end-users machines. The tariff structure includes the price information and an algorithm to calculate the charge. Thus, the monitoring of network usage according to this tariff is essential within these frameworks. However, little attention has been given to the security issues associated with Internet metering in these schemes. This has had a great impact on the new models proposed today, since security has become a major concern in open networks. Systems that naturally have incentive to fraud, such as metering systems used for billing purposes, must deal with security threats in large scale environments. The article compiles the security issues of a dynamic networked system where electronic tariffs and service level agreement (SLA) structures are distributed among service providers and customers. To address these issues, a set of security protocols is outlined.

8 citations

Proceedings ArticleDOI
26 Sep 2016
TL;DR: It is argued that most of the benefits of an NRS can be realized by indexing only a small fraction of the requested content benefiting from the NRS the most, e.g., lower inter-AS traffic, higher cache hit, and lower latency.
Abstract: A name resolution server (NRS) in an Information-Centric Network (ICN) can leverage the off-path copies in the network, which may not be accessible via content discovery mechanisms. Such capability is essential for an Autonomous System (AS) to avoid the costly inter-AS traffic for external content, to yield higher bandwidth efficiency for intra-AS traffic, and to decrease the data access latency for a pleasant user experience. However, these benefits come at the expense of storage and NRS update costs, for which scalability is paramount given huge number of contents. In this article, we argue that most of the benefits of an NRS can be realized by indexing only a small fraction of the requested content benefiting from the NRS the most. First, we model the cost of serving each content in the existence of an NRS and lack of it, considering content’s popularity, availability, size, and type. Then, we derive the optimal indexing decision under a given NRS size constraint by formulating an optimization problem that minimizes total cost for serving all requests within this AS. Our results suggest that an NRS tracking even only a tiny fraction of the most popular (external) content delivers most of the benefits of an NRS, e.g., lower inter-AS traffic, higher cache hit, and lower latency. While larger NRS provides slightly higher cache hits for small caches, the impact is more visible for larger cache capacity. In contrast to diminishing gains in cache hit, data latency decreases further with increasing NRS size owing to faster name resolution.

8 citations

Proceedings ArticleDOI
08 Jun 2016
TL;DR: This work proposes using the idea of "approximate networking"---which will provide good-enough networking services by employing contextually-appropriate tradeoffs---to survive, or even thrive, in the conditions of scarcity and limits.
Abstract: Internet is the linchpin of modern society, which the various threads of modern life weave around. But being a part of the bigger energy-guzzling industrial economy, it is vulnerable to disruption. It is widely believed that our society is exhausting its vital resources to meet our energy requirements, and the cheap fossil fuel fiesta will soon abate as we cross the tipping point of global oil production. We will then enter the long arc of scarcity, constraints, and limits---a post-peak "long emergency" that may subsist for a long time. To avoid the collapse of the networking ecosystem in this long emergency, it is imperative that we start thinking about how networking should adapt to these adverse "undeveloping" societal conditions. We propose using the idea of "approximate networking"---which will provide good-enough networking services by employing contextually-appropriate tradeoffs---to survive, or even thrive, in the conditions of scarcity and limits.

8 citations


Cited by
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[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal ArticleDOI
TL;DR: In this paper, Imagined communities: Reflections on the origin and spread of nationalism are discussed. And the history of European ideas: Vol. 21, No. 5, pp. 721-722.

13,842 citations

Journal ArticleDOI
TL;DR: A thorough exposition of community structure, or clustering, is attempted, from the definition of the main elements of the problem, to the presentation of most methods developed, with a special focus on techniques designed by statistical physicists.
Abstract: The modern science of networks has brought significant advances to our understanding of complex systems. One of the most relevant features of graphs representing real systems is community structure, or clustering, i. e. the organization of vertices in clusters, with many edges joining vertices of the same cluster and comparatively few edges joining vertices of different clusters. Such clusters, or communities, can be considered as fairly independent compartments of a graph, playing a similar role like, e. g., the tissues or the organs in the human body. Detecting communities is of great importance in sociology, biology and computer science, disciplines where systems are often represented as graphs. This problem is very hard and not yet satisfactorily solved, despite the huge effort of a large interdisciplinary community of scientists working on it over the past few years. We will attempt a thorough exposition of the topic, from the definition of the main elements of the problem, to the presentation of most methods developed, with a special focus on techniques designed by statistical physicists, from the discussion of crucial issues like the significance of clustering and how methods should be tested and compared against each other, to the description of applications to real networks.

9,057 citations

Journal ArticleDOI
TL;DR: A thorough exposition of the main elements of the clustering problem can be found in this paper, with a special focus on techniques designed by statistical physicists, from the discussion of crucial issues like the significance of clustering and how methods should be tested and compared against each other, to the description of applications to real networks.

8,432 citations