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.

Relative delay estimator for multipath transport

Abstract: Due to the dynamic nature of the Internet, the characteristic parameters of network paths are continually changing. The round trip time (RTT) can be used to estimate retransmission timeouts with reasonable accuracy. However, using RTT to evaluate forward or backward delays is not suitable. By identifying this shortcoming, we propose a relative delay estimator (RDE) to make a distinction between all available paths and build a retransmission policy based on it.

A simple TCP extension for high-speed paths

Abstract: RFC-1072 and RFC-1185 have proposed a new TCP option "Echo/Echo Reply", in which timestamps are carried in TCP headers to aid in extending the sequence number space beyond 32 bits. However, such an extension will add an extra 64 bits to the TCP header and will require option processing for each packet at both ends. In this paper, we propose a simpler TCP extension that expands the sequence number space without increasing the size of the TCP header.

Policy Control of Inter-Administrative Domain Data Communication

Abstract: In this paper we have attempted to synthesise the policy requirements of Administrative Domains and map them to the subject-object matrix normally used for access control models. This facilitates the analysis of the policy controls provided by the policy routing protocols. The hybrid model proposed by us combines the existing IDRP proposal with an alternative source routing proposal. We believe that such a unified policy routing environment will be able to meet the most policy requirements outlined in the first part of the paper.

Corrections to Aggregate Cyber-Risk Management in the IoT Age: Cautionary Statistics for (Re)Insurers and Likes

Abstract: As authors of our recently accepted article: Aggregate Cyber-Risk Management in the IoT Age: Cautionary Statistics for (Re)Insurers and Likes , published in the IEEE IoT Journal, we regret that we have found a few errors in the numerical evaluation setup of the works in [1] and [2] that we had borrowed for our accepted paper. In this correction statement, we describe the errors in detail, correct it, and present our revised results with a renewed experimental setup, hoping it to replace the existing incorrect numerical results in the accepted paper. We apologize for the inconvenience caused to the reader. We emphasize that the numerical evaluation section does not in any way hamper the theoretical contributions in this article, and was initially only meant to provide some empirical evidence for whether the theory proposed in this article generalizes to behavioral settings introduced in [2] .

Towards Provable Remote Data Deletion Through Quantum Entanglement.

Abstract: A continuing challenge in computing is how to retain control of shared information, given the ease of loss-less copying that is possible. This challenge is becoming increasingly acute as the ease of distributing information continues to grow exponentially. Quantum Computing, which makes use of quantum mechanical phenomena, may offer a solution through the property of quantum entanglement. This property occurs when particles interact physically and then become separated, resulting in each of the pair having the same quantum mechanical description (state). So, we could utilise quantum bits (qubits), which are a unit of quantum information and analogous to classical bits, with the property of quantum entanglement to control the distribution of information. Therefore, if two qubits are connected via quantum entanglement [3], the value of one could be controlled by the other so that shared secrets can be destroyed (deleted) remotely. The approach becomes feasible as the number of qubits constructed continues to grow, with a qubyte (composed of eight quantum bits) being constructed in 2005. However, scaling to multiple remote copies would require multiple source copies, because the quantum-no-deleting principle implies that the ability to delete can drop exponentially with the number of copies to be deleted [1]. Also, given that quantum entanglement is yet to exceed 144 km [2], the approach would not yet scale globally. BODY If we connect two qubits via quantum entanglement, the fate of one can be controlled by the other so shared secrets can be deleted remotely.

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.