SURF

In this data release from the ongoing LOw-Frequency ARray (LOFAR) Two-metre Sky Survey we present 120–168 MHz images covering 27% of the northern sky. Our coverage is split into two regions centred at approximately 12h45m +44°30′ and 1h00m +28°00′ and spanning 4178 and 1457 square degrees respectively. The images were derived from 3451 h (7.6 PB) of LOFAR High Band Antenna data which were corrected for the direction-independent instrumental properties as well as direction-dependent ionospheric distortions during extensive, but fully automated, data processing. A catalogue of 4 396 228 radio sources is derived from our total intensity (Stokes I ) maps, where the majority of these have never been detected at radio wavelengths before. At 6″ resolution, our full bandwidth Stokes I continuum maps with a central frequency of 144 MHz have: a median rms sensitivity of 83 μJy beam −1 ; a flux density scale accuracy of approximately 10%; an astrometric accuracy of 0.2″; and we estimate the point-source completeness to be 90% at a peak brightness of 0.8 mJy beam −1 . By creating three 16 MHz bandwidth images across the band we are able to measure the in-band spectral index of many sources, albeit with an error on the derived spectral index of > ± 0.2 which is a consequence of our flux-density scale accuracy and small fractional bandwidth. Our circular polarisation (Stokes V ) 20″ resolution 120–168 MHz continuum images have a median rms sensitivity of 95 μJy beam −1 , and we estimate a Stokes I to Stokes V leakage of 0.056%. Our linear polarisation (Stokes Q and Stokes U ) image cubes consist of 480 × 97.6 kHz wide planes and have a median rms sensitivity per plane of 10.8 mJy beam −1 at 4′ and 2.2 mJy beam −1 at 20″; we estimate the Stokes I to Stokes Q / U leakage to be approximately 0.2%. Here we characterise and publicly release our Stokes I , Q , U and V images in addition to the calibrated uv -data to facilitate the thorough scientific exploitation of this unique dataset.

The FAIR principles have been widely cited, endorsed and adopted by a broad range of stakeholders since their publication in 2016. By intention, the 15 FAIR guiding principles do not dictate specific technological implementations, but provide guidance for improving Findability, Accessibility, Interoperability and Reusability of digital resources. This has likely contributed to the broad adoption of the FAIR principles, because individual stakeholder communities can implement their own FAIR solutions. However, it has also resulted in inconsistent interpretations that carry the risk of leading to incompatible implementations. Thus, while the FAIR principles are formulated on a high level and may be interpreted and implemented in different ways, for true interoperability we need to support convergence in implementation choices that are widely accessible and (re)-usable. We introduce the concept of FAIR implementation considerations to assist accelerated global participation and convergence towards accessible, robust, widespread and consistent FAIR implementations. Any self-identified stakeholder community may either choose to reuse solutions from existing implementations, or when they spot a gap, accept the challenge to create the needed solution, which, ideally, can be used again by other communities in the future. Here, we provide interpretations and implementation considerations (choices and challenges) for each FAIR principle.

Abstract In order to bring quantum networks into the real world, we would like to determine the requirements of quantum network protocols including the underlying quantum hardware. Because detailed architecture proposals are generally too complex for mathematical analysis, it is natural to employ numerical simulation. Here we introduce NetSquid, the NETwork Simulator for QUantum Information using Discrete events, a discrete-event based platform for simulating all aspects of quantum networks and modular quantum computing systems, ranging from the physical layer and its control plane up to the application level. We study several use cases to showcase NetSquid’s power, including detailed physical layer simulations of repeater chains based on nitrogen vacancy centres in diamond as well as atomic ensembles. We also study the control plane of a quantum switch beyond its analytically known regime, and showcase NetSquid’s ability to investigate large networks by simulating entanglement distribution over a chain of up to one thousand nodes.

The application of White Rabbit precision time protocol (WR-PTP) in long-distance optical fiber links has been investigated. WR-PTP is an implementation of PTP in synchronous Ethernet optical fiber networks, originally intended for synchronization of equipment within a range of 10 km. This paper discusses the results and limitations of two implementations of WR-PTP in the existing communication fiber networks. A 950-km WR-PTP link was realized using unidirectional paths in a fiber pair between Espoo and Kajaani, Finland. The time transfer on this link was compared (after initial calibration) against a clock comparison by GPS precise point positioning (PPP). The agreement between the two methods remained within [Formula: see text] over three months of measurements. Another WR-PTP implementation was realized between Delft and Amsterdam, the Netherlands, by cascading two links of 137 km each. In this case, the WR links were realized as bidirectional paths in single fibers. The measured time offset between the starting and end points of the link was within 5 ns with an uncertainty of 8 ns, mainly due to the estimated delay asymmetry caused by chromatic dispersion.

In 2012, the Dutch National Research and Education Network, SURFnet, observed a multitude of Distributed Denial of Service (DDoS) attacks against educational institutions. These attacks were effective enough to cause the online exams of hundreds of students to be cancelled. Surprisingly, these attacks were purchased by students from Web sites, known as Booters. These sites provide DDoS attacks as a paid service (DDoS-as-a-Service) at costs starting from 1 USD. Since this problem was first identified by SURFnet, Booters have been used repeatedly to perform attacks on schools in SURFnet's constituency. Very little is known, however, about the characteristics of Booters, and particularly how their attacks are structure. This is vital information needed to mitigate these attacks. In this paper we analyse the characteristics of 14 distinct Booters based on more than 250 GB of network data from real attacks. Our findings show that Booters pose a real threat that should not be underestimated, especially since our analysis suggests that they can easily increase their firepower based on their current infrastructure.

This global experiment wants to see if high-end applications needing transport capacities of multiple Gbps for up to hours at a time can be handled through an optical bypass network.

Near Field Communication (NFC) technology enables devices to communicate wirelessly within proximity distance. These NFC devices are often embedded into smart posters that offer the ability to exchange small files, photos and contact details. The Nokia 6212 Classic is currently the most popular NFC phone. It allows users to easily exchange digital objects using the NFC interface. To do so, two phones should be within the proximity coupling distance of 5 cm. This paper shows that the NFC feature that invokes a Bluetooth connection without user consent can be abused to surreptitiously install malicious software on the phone. This results in a serious vulnerability when smart posters start installing malicious software or spreading viruses.

Purpose Innovative use of information and communications technology (ICT) requires (new) knowledge and skills for the group that has the biggest impact on the quality of education: instructors. Facilitating professional development (PD) of instructors is crucial for the quality of one’s education system(s), perhaps even more so in times of a pandemic. Design/methodology/approach Based on the authors’ analysis of reviews published in the last decade, this paper summarizes the key building blocks of effective PD on the innovative use of ICT during a pandemic. The authors used these building blocks to reflect on two national PD initiatives developed to support institutions of higher education in instructional use of ICT while dealing with the consequences of the COVID-19 pandemic. Findings Both PD initiatives include the same building blocks: (1) content-related building blocks focused on technological knowledge, (2) active learning and expert-supported PD (didactics-related building blocks) and (3) contextual building blocks consisting of clearly defined goals focused on the instructor's own practice, use of technology, sustained duration (e.g. taking place over a longer period of time) and evidence-informed PD. One contextual building block that was not evident in the reviews but emerged as a vital building block is “responsiveness” to the situation and needs of the participants. Originality/value High-quality PD is crucial if one wants to safeguard the quality of (online) instruction and learning to ensure high-quality education for all students. This paper can contribute to enhancing the quality of much-needed PD on online teaching (during, but also after COVID-19).

Data sets in e-science are increasing exponentially in size. To transfer these huge data sets we need to make efficient use of all available network capacity. This means using multiple paths when available. In this paper a prototype of such a multipath network is presented. Several emerging network technologies are integrated to achieve the goal of efficient high end-to-end throughput. Multipath TCP is used by the end hosts to distribute the traffic across multiple paths and OpenFlow is used within the network to do the wide area traffic engineering. Extensive monitoring is part of the demonstration. A website will show the actual topology (including link outages), the paths provisioned through the network and traffic statistics on all links and the end-to-end aggregate throughput.

The number of mobile devices within academia has increased significantly over the last couple of years and users expect to be able to get connectivity everywhere, at home, on the road and at educational institutions. At the same time however, the security of wireless LANs becomes more and more of a concern In 2003, the TERENA Task Force on Mobility [1] was created to look at WLAN security issues and to formulate requirements to design an international roaming solution that would provide National Research and Educational Networks' (NRENs') users with secure Internet access at academic campuses across Europe. The solution proposed was tested and proved to be very successful with more and more institutions joining it. This infrastructure is called eduroam, which stands for Education Roaming. Within the 6th framework project GANT2 [2], the aim is to expand the existing infrastructure into a pan-European full service for Roaming and Authentication/Authorisation.

Abstract Long-distance quantum communication via entanglement distribution is of great importance for the quantum internet. However, scaling up to such long distances has proved challenging due to the loss of photons, which grows exponentially with the distance covered. Quantum repeaters could in theory be used to extend the distances over which entanglement can be distributed, but in practice hardware quality is still lacking. Furthermore, it is generally not clear how an improvement in a certain repeater parameter, such as memory quality or attempt rate, impacts the overall network performance, rendering the path toward scalable quantum repeaters unclear. In this work we propose a methodology based on genetic algorithms and simulations of quantum repeater chains for optimization of entanglement generation and distribution. By applying it to simulations of several different repeater chains, including real-world fiber topology, we demonstrate that it can be used to answer questions such as what are the minimum viable quantum repeaters satisfying given network performance benchmarks. This methodology constitutes an invaluable tool for the development of a blueprint for a pan-European quantum internet. We have made our code, in the form of NetSquid simulations and the smart-stopos optimization tool, freely available for use either locally or on high-performance computing centers.

Context. Surveys of protoplanetary disks in nearby star-forming regions (SFRs) have provided important information on their demographics. However, due to their sample sizes, these surveys cannot be used to study how disk properties vary with the environment. Aims. We conduct a survey of the unresolved millimeter continuum emission of 873 protoplanetary disks identified by Spitzer in the L1641 and L1647 regions of the Orion A cloud. This is the largest such survey yet, allowing us to identify even weak trends in the median disk mass as a function of position in the cloud and cluster membership. The sample detection rates and median masses are also compared to those of nearby (<300 pc) SFRs. Methods. The sample was observed with the Atacama Large Millimeter/submillimeter Array (ALMA) at 225 GHz, with a median rms of 0.08 mJy beam −1 , or 1.5 M ⊕ . The data were reduced and imaged using an innovative parallel data processing approach. Results. We detected 58% (502/873) of the observed disks. This includes 20 disks with dust masses >100 M ⊕ , and two objects associated with extended dust emission. By fitting a log-normal distribution to the data, we infer a median disk dust mass in the full sample of 2.2 −0.2 +0.2 M ⊕ . In L1641 and L1647, median dust masses are 2.1 −0.2 +0.2 M ⊕ and 2.6 −0.5 +0.4 M ⊕ , respectively. Conclusions. The disk mass distribution of the full sample is similar to that of nearby low-mass SFRs at similar ages of 1–3 Myr. We find only weak trends in disk (dust) masses with galactic longitude and between the Young Stellar Object (YSO) clusters identified in the sample, with median masses varying by ≲50%. Differences in age may explain the median disk mass variations in our subsamples. Apart from this, disk masses are essentially constant at scales of ~100 pc. This also suggests that the majority of disks, even in different SFRs, are formed with similar initial masses and evolve at similar rates, assuming no external irradiation, with disk mass loss rates of ~10 −8 M ⊙ yr −1 .

Abstract We numerically study the distribution of entanglement between the Dutch cities of Delft and Eindhoven realized with a processing-node quantum repeater and determine minimal hardware requirements for verifiable blind quantum computation using color centers and trapped ions. Our results are obtained considering restrictions imposed by a real-world fiber grid and using detailed hardware-specific models. By comparing our results to those we would obtain in idealized settings, we show that simplifications lead to a distorted picture of hardware demands, particularly on memory coherence and photon collection. We develop general machinery suitable for studying arbitrary processing-node repeater chains using NetSquid, a discrete-event simulator for quantum networks. This enables us to include time-dependent noise models and simulate repeater protocols with cut-offs, including the required classical control communication. We find minimal hardware requirements by solving an optimization problem using genetic algorithms on a high-performance-computing cluster. Our work provides guidance for further experimental progress, and showcases limitations of studying quantum-repeater requirements in idealized situations.

This paper proposes a threat detection system based on Machine Learning classifiers that are trained using darknet traffic. Traffic destined to Darknet is either malicious or by misconfiguration. Darknet traffic contains traces of several threats such as DDoS attacks, botnets, spoofing, probes and scanning attacks. We analyse darknet traffic by extracting network traffic features from it that help in finding patterns of these advanced threats. We collected the darknet traffic from the network sensors deployed at SURFnet and extracted several network-based features. In this study, we proposed a framework that uses supervised machine learning and a concept drift detector. Our experimental results show that our classifiers can easily distinguish between benign and malign traffic and are able to detect known and unknown threats effectively with an accuracy above 99%.

The book aims to increase understanding of the challenges to make scholarship more open. It addresses various perspectives offered by KE's Open Scholarship Framework, combining levels (micro, meso and macro-level actors), arenas (political, economic, social, technical) and research phases (discovery, planning, project phase, dissemination). As many of the challenges in navigating the transition to Open Scholarship are economic, the focus of the book is on the <strong>economic arena</strong>. In addition, great attention is given to the incentives, actions and influences of <strong>meso-level actors</strong>: groups, communities or organisations such as universities, disciplines, scholarly societies or publishers because of their enormous impact on developing open scholarship. Taking in the Open Scholarship landscape, the authors of the book - experts and experienced actors in the field of Open Scholarship - look at the stakeholders and their interactions and networks. They examine the historic developments leading to the current organisational complexity, responsibility issues, conflicting motives and values, and the importance of interaction between institutions. The authors analyse how economic models can be applied to scholarship and conclude that economic theory cannot fully explain nor prescribe how Open Scholarship can be achieved. The challenges to achieve Open Scholarship, such as gravitational hubs and the complex governance of common pool resources, are highlighted. The conclusion of the book is that for a successful transition to Open Scholarship, <strong>collective action approaches</strong> and establishment of a supportive infrastructure are key.

The FAIR principles articulate the behaviors expected from digital artifacts that are Findable, Accessible, Interoperable and Reusable by machines and by people. Although by now widely accepted, the FAIR Principles by design do not explicitly consider actual implementation choices enabling FAIR behaviors. As different communities have their own, often well-established implementation preferences and priorities for data reuse, coordinating a broadly accepted, widely used FAIR implementation approach remains a global challenge. In an effort to accelerate broad community convergence on FAIR implementation options, the GO FAIR community has launched the development of the FAIR Convergence Matrix. The Matrix is a platform that compiles for any community of practice, an inventory of their self-declared FAIR implementation choices and challenges. The Convergence Matrix is itself a FAIR resource, openly available, and encourages voluntary participation by any self-identified community of practice (not only the GO FAIR Implementation Networks). Based on patterns of use and reuse of existing resources, the Convergence Matrix supports the transparent derivation of strategies that optimally coordinate convergence on standards and technologies in the emerging Internet of FAIR Data and Services.

Regularly, new architectures are proposed to address shortcomings in the current internet. It is not always trivial to evaluate how these proposals would perform in practice. This situation is improved significantly with the introduction of the P4 programming language and programmable network equipment. In this paper we discuss our implementation of one particular future internet architecture, namely SCION. We implemented a SCION router in P4 for switches based on the Intel Tofino ASIC. Having an open source P4 implementation of SCION that runs on high-speed hardware can contribute to its adoption as well as support research in this area. Our work lead to several recommendations for and subsequent changes to the SCION protocol, as well as some generic guidelines when designing protocols. A first analysis of our implementation shows it can process SCION packets at high speeds.

Authentication is of paramount importance for all modern networked applications. The username/password paradigm is ubiquitous. This paradigm suffices for many applications that require a relatively low level of assurance about the identity of the end user, but it quickly breaks down when a stronger assertion of the user’s identity is required. Traditionally, this is where two- or multi-factor authentication comes in, providing a higher level of assurance. There is a multitude of two-factor authentication solutions available, but we feel that many solutions do not meet the needs of our community. They are invariably expensive, difficult to roll out in heterogeneous user groups (like student populations), often closed source and closed technology and have usability problems that make them hard to use. In this paper we will give an overview of the two-factor au- thentication landscape and address the issues of closed versus open solutions. We will introduce a novel open standards-based authentication technology that we have developed and released in open source. We will then provide a classification of two-factor authentication technologies, and we will finish with an overview of future work.

The Domain Name System Security Extensions (DNSSEC) are steadily being deployed across the Internet. DNSSEC extends the DNS protocol with two vital security properties, authenticity and integrity, using digital signatures. While DNSSEC is meant to solve security issues in the DNS, it also introduces a new one: the digital signatures significantly increase DNS packet sizes, making DNSSEC an attractive vector to abuse in amplification denial-of-service attacks. By default, DNSSEC uses RSA for digital signatures. Earlier work has shown that alternative signature schemes, based on elliptic curve cryptography, can significantly reduce the impact of signatures on DNS response sizes. In this paper we study the actual adoption of ECDSA by DNSSEC operators, based on longitudinal datasets covering over 50% of the global DNS namespace over a period of 1.5 years. Adoption is still marginal, with just 2.3% of DNSSEC-signed domains in the .com TLD using ECDSA. Nevertheless, use of ECDSA is growing, with at least one large operator leading the pack. And adoption could be up to 42% higher. As we demonstrate, there are barriers to deployment that hamper adoption. Operators wishing to deploy DNSSEC using current recommendations (with ECDSA as signing algorithm) must be mindful of this when planning their deployment.

Summary The environmental protection is a dominant concern for all types of industries, organizations, and governments. In this regard, the reduction of the energy consumption is substantial in bringing down the CO2 gas emission, which is considered as an important factor causing global warming. The e‐infrastructure service providers, such as National Research and Education Networks or National Grid Initiatives have crucial role in the context of energy awareness because the energy consumption of the networking, data, and computational infrastructures keeps increasing exponentially over the time. In addition to this, scientific gateways and cloud services are becoming more significant to tackle scientific and societal challenges. Therefore, there is a need to provide robust and reliable services taking into account energy consumption aspect of e‐infrastructures. The aim of the article is to introduce an energy optimization methodology for the beneficiaries of the e‐infrastructures to explore, optimize, and report the energy consumption and CO2 emission of data, computing, and networking facilities. The suggested methodology has been implemented within the Armenian e‐infrastructure aiming at the reduction of the energy consumption and thereby the CO2 emission.