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.

Human mobility models and opportunistic communications system design.

Abstract: In this paper, we seek to improve understanding of the structure of human mobility, with a view to using this for designing algorithms for the dissemination of data among mobile users. We analyse community structures and node centrality from the human mobility traces and use these two metrics to design efficient forwarding algorithms in terms of delivery ratio and delivery cost for mobile networks. This is the first empirical study of community and centrality using real human mobility datasets.

On the monitoring of contractual service level agreements

Abstract: The goal of monitoring contractual service level agreements (SLAs) is to measure the performance of a service, to evaluate whether its provider complies with the level of quality of the service (QoS) that the consumer expects. The aim of this paper is to bring to the system designer's attention the fundamental issues that monitoring of contractual SLAs involves: SLA specification, separation of the computation and communication infrastructure of the provider, service points of presence, metric collection approaches, measurement service and evaluation and violation detection service. The paper develops an architecture and give reasons why currently it is practicable to offer guaranteed QoS only to consumers sharing Internet service providers (ISPs) directly with the service provider.

The conference control channel protocol (CCCP): a scalable base for building conference control applications

Abstract: This paper presents the Conference Control Channel Protocol (CCCP), a new scheme intended for controlling conferences ranging from small, tightly coupled meetings, to extremely large loosely coupled seminars. We describe the requirements of such a scheme, and present a framework for building systems that connect together new and existing applications.

Implementing real time packet forwarding policies using streams

Abstract: This paper describes an implementation of the class based queueing (CBQ) mechanisms proposed by Sally Floyd and Van Jacobson to provide real time policies for packet forwarding. CBQ allows the traffic flows sharing a data link to be guaranteed a share of the bandwidth when the link is congested, yet allows flexible sharing of the unused bandwidth when the link is unloaded. In addition, CBQ provides mechanisms which give flows requiring low delay priority over other flows. In this way, links can be shared by multiple flows yet still meet the policy and Quality of Service (QoS) requirements of the flows. We present a brief description of the implementation and some preliminary preformance measurements. The problems of packet classification are addressed in a flexible and extensible, yet efficient manner, and whilst the Streams implementation cannot cope with very high speed interfaces, it can cope with the serial link speeds that are likely to be loaded.

I and i

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 …

Community detection in graphs

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.