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.

SCDP: systematic rateless coding for efficient data transport in data centres

Abstract: In this paper we propose SCDP, a general-purpose data transport protocol for data centres that, in contrast to all other protocols proposed to date, supports efficient one-to-many and many-to-one 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, 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 and PIAS. For short and long unicast flows, SCDP performs equally well or better compared to NDP and PIAS.

Bringing Information Centric Networking to Challenged Environments: An overview of the Second Workshop on Future Internet Architecture for Developing Regions

Abstract: The 2nd workshop on Future Internet Architecture for Developing Regions (FI4D) took place on January 8th, 2017. The workshop was hosted by the 14th Annual IEEE Consumer Communications $\&$ Networking Conference in Las Vegas, USA. This report summarizes the motivation, discussions and perspectives held during the half-day event.

Proceedings of the 2015 Workshop on Do-it-yourself Networking: an Interdisciplinary Approach

Abstract: It is our great pleasure to welcome you to the first of a series of interdisciplinary workshops on DIY networking. They build on a recent successful Dagstuhl seminar by the name "DIY networking: an interdisciplinary perspective", which brought together a highly diverse group of researchers and practitioners to reflect on technological and social issues related to the use of local wireless networks operating outside the public Internet. The seminar initiated a process of bridging the communication gap between those who build technology (e.g. computer scientists, engineers, and hackers) and those who understand better the complex urban environment where this technology is deployed (e.g. social and political scientists, urban planners, designers, and artists). Now in DIYnet 2015 -- hosted by ACM MobiSys -- the participants try to make one more step toward facilitating interdisciplinary exchanges around the complex design space defined by DIY networking solutions, for a more creative interplay between technological and human networks in the city. The technical programme includes both conceptual and experiential entries with DIY networking applications, and novel scientific contributions on important technical questions. We are also very proud to have with us key people coming from different domains that are close to the common object of enquiry: DIY networking. More specifically Michael Smyth (Edinburgh Napier University) will give a keynote talk on Urban Interaction Design, and highlight the interdisciplinary perspective of hybrid space design. Paul Dourish (University of California, Irvine) will give a second keynote talk on The Politics of Infrastructure Projects, which will bring the political dimension. Andreas Unteidig (Berlin University of the Arts) will give a demo of the "hybrid letter box" and introduce the design research perspective. Mathias Jud (independent artist) will give a demo of the community art project http://www.qaul.net, which has received the "Prix Ars electronica [the next idea]", and bring the artistic and activist perspective.

RAFT Consensus Reliability in Wireless Networks: Probabilistic Analysis

Abstract: The centralized system becomes less efficient, secure, and resilient as the network size and heterogeneity increase due to its inherent single point of failure issues. Distributed consensus mechanisms characterized by decentralization, autonomy, parallelism, and fault-tolerance can meet the increasing demands of safety and security in critical interconnected systems. This article establishes a Node and Link probabilistic failure model in the presence of node and communication link failures for a representative crash fault-tolerant distributed consensus protocol: RAFT. The analytical results in terms of the probability density function and the mean value of consensus reliability are derived. Two important reliability performance indicators, Reliability Gain and Tolerance Gain are proposed to indicate the linear relationship between the consensus reliability and two basic parameters, i.e., the joint failure rate and the maximum number of tolerant faulty nodes, which provide the theoretical guidance for quickly deploying an RAFT system. The special case of a distributed consensus network with already a certain number of failures and its adverse impact are evaluated. The Markov probabilistic models, definitions of Reliability Gain and Tolerance Gain, and the analysis methods proposed in this article can be extended to other consensus mechanisms.

Prospects for Internet technology

Abstract: This paper surveys the current developments in Internet technology, with a particular emphasis on performance, and the growing need for various guarantees of quality of service. It discusses hardware technologies for increased bandwidth, mechanisms for requesting and providing specific qualities of service, and various scaling issues. Finally it discusses mechanisms needed for (but not the economics of) the Internet in the mass market. To this end, we survey changes in the areas of addressing, and flow management.

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.