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.

Engineering global ubiquitous systems.

Abstract: We are urgently in need of engineering design patterns for ubiquitous computing. Ubicomp threatens us with a grand dose of the ‘Interconnectedness of everything’ and so even the smartest of systems designers cannot hold all the factors in mind when building and deploying a Ubicomp application.

FutureGRID: A Program for long-term research into GRID systems architecture

Abstract: Proceedings of the 2003 UK e-Science All Hands Meeting, 31st August - 3rd September, Nottingham UK

Towards Data-Driven Declarative Networking in Delay Tolerant Networks

Abstract: A Delay Tolerant Network (DTN) provides content storage as a core network service across applications to deal with intermittent communication. Thus, the DTN realizes contentbased networking, where messages flowing within networks are at content level, rather than at packet level and focus on information dissemination rather than on node delivery. In the Haggle project, which is a type of DTN, we manage to implement publish/subscribe semantics with an eventdriven and asynchronous operation into a kernel component for enabling efficient distributed content storage. We are working towards an integration of declarative networking to Haggle for data-driven declarative networking. 1. DATA-DRIVEN NETWORKING

Wardrop Equilibrium Formulation of Resource-Constrained DTN Routing in Public Safety Networks

Abstract: In this paper, we investigate the ability of using Delay Tolerant Networking (DTN) in Public Safety networks where bandwidth and storage are constrained. We formalize the problem as a Wardrop equilibrium over a time-discretized graph. Driven by our findings, we propose RECOR, a centralized REsource-Constrained ORacle-based DTN routing mechanism which spreads the demand across multiple store-carry forward paths to satisfy the node storage and link transport constraints observed in intervention situations. By applying the proposed mechanism to real Bluetooth-based DTN traces, we show that the transmission bottleneck can be compensated, but only up to a certain extent, by increasing storage capacity and delay. We also analyze the benefit of strategies that provide more resources to highly connected nodes (e.g. ambulances and firetrucks) which can then feed incentives and policies for DTN network engineering. Finally, the idea presented here is general and suggests the necessity of trace-driven simulation and specific modeling tools for appropriate design of future DTN resource management policies. © 2011 IEEE.

SCDP: Systematic Rateless Coding for Efficient Data Transport in Data Centres

Abstract: In this paper we propose SCDP, a novel, general-purpose data transport protocol for data centres that, in contrast to all other protocols proposed to date, natively supports one-to-many and many-to-one data communication, which is extremely common in modern data centres. SCDP does so without compromising on efficiency for short and long unicast flows. SCDP achieves this by integrating RaptorQ codes with receiver-driven data transport, in-network packet trimming and Multi-Level Feedback Queuing (MLFQ); (1) RaptorQ codes enable efficient one-to-many and many-to-one data transport; (2) on top of RaptorQ codes, receiver-driven flow control, in combination with in-network packet trimming, enable efficient usage of network resources as well as multi-path transport and packet spraying for all transport modes. Incast and Outcast are eliminated; (3) the systematic nature of RaptorQ codes, in combination with MLFQ, enable fast, decoding-free completion of short flows. We extensively evaluate SCDP in a wide range of simulated scenarios with realistic data centre workloads. For one-to-many and many-to-one transport sessions, SCDP performs significantly better compared to NDP. For short and long unicast flows, SCDP performs equally well or better compared to NDP.

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.