Recursive quantum repeater networks

Internet-scale quantum repeater networks will be heterogeneous in physical technology, repeater functionality, and management. The classical control necessary to use the network will therefore face similar issues as Internet data transmission. Many scalability and management problems that arose during the development of the Internet might have been solved in a more uniform fashion, improving flexibility and reducing redundant engineering effort. Quantum repeater network development is currently at the stage where we risk similar duplication when separate systems are combined. We propose a unifying framework that can be used with all existing repeater designs. We introduce the notion of a Quantum Recursive Network Architecture, developed from the emerging classical concept of 'recursive networks', extending recursive mechanisms from a focus on data forwarding to a more general distributed computing request framework. Recursion abstracts independent transit networks as single relay nodes, unifies software layering, and virtualizes the addresses of resources to improve information hiding and resource management. Our architecture is useful for building arbitrary distributed states, including fundamental distributed states such as Bell pairs and GHZ, W, and cluster states.Comment: 14 page

Deep Space Network information system architecture study

The purpose of this article is to describe an architecture for the Deep Space Network (DSN) information system in the years 2000-2010 and to provide guidelines for its evolution during the 1990s. The study scope is defined to be from the front-end areas at the antennas to the end users (spacecraft teams, principal investigators, archival storage systems, and non-NASA partners). The architectural vision provides guidance for major DSN implementation efforts during the next decade. A strong motivation for the study is an expected dramatic improvement in information-systems technologies, such as the following: computer processing, automation technology (including knowledge-based systems), networking and data transport, software and hardware engineering, and human-interface technology. The proposed Ground Information System has the following major features: unified architecture from the front-end area to the end user; open-systems standards to achieve interoperability; DSN production of level 0 data; delivery of level 0 data from the Deep Space Communications Complex, if desired; dedicated telemetry processors for each receiver; security against unauthorized access and errors; and highly automated monitor and control

The solar chromosphere at high resolution with IBIS. II. Acoustic shocks in the quiet internetwork and the role of magnetic fields

(Abridged) Aims: We characterize the dynamics of the quiet inter-network chromosphere by studying the occurrence of acoustic shocks and their relation with the concomitant photospheric structure and dynamics. Methods: We analyze a comprehensive data set that includes high resolution chromospheric and photospheric spectra obtained with the IBIS imaging spectrometer in two quiet-Sun regions. This is complemented by high-resolution sequences of MDI magnetograms of the same targets. From the chromospheric spectra we identify the spatio-temporal occurrence of the acoustic shocks. We compare it with the photospheric dynamics by means of both Fourier and wavelet analysis, and study the influence of magnetic structures. Results: Mid-chromospheric shocks occur as a response to underlying powerful photospheric motions at periodicities nearing the acoustic cut-off, consistent with 1-D hydrodynamical modeling. However, their spatial distribution within the supergranular cells is highly dependent on the local magnetic topology, both at the network and internetwork scale. Large portions of the internetwork regions undergo very few shocks, as "shadowed" by the horizontal component of the magnetic field. The latter is betrayed by the presence of chromospheric fibrils, observed in the core of the CaII line as slanted structures with distinct dynamical properties. The shadow mechanism appears to operate also on the very small scales of inter-network magnetic elements, and provides for a very pervasive influence of the magnetic field even in the quietest region analyzed.Comment: 18 pages, 16 figures (includes 1 Appendix). Accepted by A&A (16 October 2008). Minor changes from v1 after referee's comments. Higher quality figures available at http://www.arcetri.astro.it/~gcauzzi/papers_astroph/ibis.shocks.accepted.pd

On the Magnetic Nature of an Exploding Granule as Revealed by Sunrise/IMaX

We study the photospheric evolution of an exploding granule observed in the quiet Sun at high spatial ($0.3^{\prime\prime}$) and temporal (31.5 s) resolution by the imaging magnetograph Sunrise/IMaX in June 2009. These observations show that the exploding granule is cospatial to a magnetic flux emergence event occurring at mesogranular scale (up to 12 Mm$^{2}$ area). Using a modified version of the SIR code for inverting the IMaX spectropolarimetric measurements, we obtain information about the magnetic configuration of this photospheric feature. In particular, we find evidence of highly inclined emerging fields in the structure, carrying a magnetic flux content up to $4 \times 10^{18}$ Mx. The balance between gas and magnetic pressure in the region of flux emergence, compared with a very quiet region of the Sun, indicates that the additional pressure carried by the emerging flux increases by about 5% the total pressure and appears to allow the granulation to be modified, as predicted by numerical simulations. The overall characteristics suggest that a multi-polar structure emerges into the photosphere, resembling an almost horizontal flux sheet. This seems to be associated with exploding granules. Finally, we discuss the origin of such flux emergence events.Comment: 19 pages, 12 figure + Appendix, accepted for ApJ. Figure 1 and Figure 5 are a low-quality version of the original one

Distributed computation in computer networks

None provide

High-resolution wave dynamics in the lower solar atmosphere

The magnetic and convective nature of the Sun's photosphere provides a unique platform from which generated waves can be modelled, observed, and interpreted across a wide breadth of spatial and temporal scales. As oscillations are generated in-situ or emerge through the photospheric layers, the interplay between the rapidly evolving densities, temperatures, and magnetic field strengths provides dynamic evolution of the embedded wave modes as they propagate into the tenuous solar chromosphere. A focused science team was assembled to discuss the current challenges faced in wave studies in the lower solar atmosphere, including those related to spectropolarimetry and radiative transfer in the optically thick regions. Following the Theo Murphy international scientific meeting held at Chicheley Hall during February 2020, the scientific team worked collaboratively to produce 15 independent publications for the current Special Issue, which are introduced here. Implications from the current research efforts are discussed in terms of upcoming next-generation observing and high performance computing facilities.Comment: 16 pages, 4 figures, Introduction to the "High-resolution wave dynamics in the lower solar atmosphere" special issue of the Philosophical Transactions A: https://walsa.team/u/rst

Contributions to routing scalability and QoS assurance in cloud data transport networks based on the recursive internetwork architecture

With an increasing number of devices and heterogeneous distributed applications, it is becoming evident that service delivered by the current Internet fall short to supply the actual Quality of Service (QoS) requirements of applications. In addition, the global scope of the IP layer causes large scalability problems on the network. Multiple solutions aim to overcome the limitations of the model (BGP, NAT, etc.), but all end being constrained by the same networking model that they try to improve, ending simply breaking and patching the stack itself of TCP/IP. In contrast, RINA proposes a new clean-slate Internet architecture based on a recursive networking stack with focus on inter process communication, where each layer, or DIF, performs the same set of tasks. DIFs are fully configurable by mean of programmable policies, and provide complete support for QoS services. RINA is capable to provide a standardized way to express the capabilities of each layer, the QoS Cubes. With those, RINA allows for applications and upper processes to express their requirements in terms of latency, losses, etc. The contributions in this thesis take profit from the recursive stack of RINA and the use of policies to propose and analyse old and new solutions which would not be compatible with the current TCP/IP Internet. Improving the QoS services, this work takes profit from the information on requirements provided by the applications themselves to improve the assurance of QoS. With the use of Q-based scheduling policies, improved QoS assurances are provided, aiming to provide “good enough” service for all flows in the network, resulting in a more appropriate sharing of resources. These policies have been tested in backbone-like networks, showing interesting improvements with respect to commonly used solutions like MPLS-based VPNs. In addition the provisioning of QoS services to end-users is also considered. In order to allow that, it is required to impose some limits on what end-users can send to the network, limiting the amount of priority traffic that potentially greedy users can send. In that regard, while enforcing strict rate-limits per QoS would be trivial in RINA, a new △Q-based rate-limiting policy that aims to limit the amount of priority traffic in a more user-friendly way is also explored. In terms of scalability, this work also considers different measures to improve forwarding and routing within large-scale networks. As for the use of policies that could profit from specific network topologies, a new forwarding policy, that mix both topological rules and exceptions, is proposed. With this policy, forwarding table lookups in large tables are replaced with fast and simple forwarding rules based on the location of nodes and their neighbourhood. Given the common topologies used in large data centres, the proposed policy is found to be a perfect match for those scenarios. Test for different data centre topology showed clear improvements, requiring only a small fraction of all forwarding information despite the large size of such networks, depending that in the number of concurrent failures in the network rather than on the size of it. In addition, this work also considers the use of topological routing policies to populate exceptions upon failures. The use of topological routing solutions resulted in reduced complexity for computing paths and less routing messages. In addition to topological solutions, the use other routing solution, not well suited for the IP environment are also investigated. Specifically, it is shown how a Landmark routing solution could be implemented within RINA. Finally, efforts are also devoted to analyse the importance of path selection for ensuring QoS requirements and how it is not required to reach extremes solutions, like the use of connections, to provide the required services.Con un número cada vez mayor de dispositivos y aplicaciones distribuidas, se está volviendo evidente que el servicio best-effort ofrecido por la actual Internet TCP/IP no satisface los requisitos de calidad de servicio (QoS) de las aplicaciones. No solo eso, sino que el alcance global de la capa de IP se convierte en la causa de grandes problemas de escalabilidad, requiriendo costes cada vez más altos para ser resueltos. Desde la implantación de TCP/IP, han aparecido múltiples soluciones que tienen como objetivo superar las limitaciones del modelo (BGP, NAT, LISP, etc.). Aun así, todas estas soluciones terminan restringidas por el mismo modelo de red que intentan mejorar. Dado esto, la mayoría de las soluciones terminan simplemente rompiendo y parcheando la pila misma de TCP/IP. Con el objetivo de resolver esos problemas, la Recursive InterNetwork Architecture (RINA) propone una nueva arquitectura de Internet que vuelve a las raíces de la comunicación en red. En lugar de parchear la pila actual de TCP/IP, RINA propone una pila de red recursiva con enfoque en la comunicación entre procesos, donde cada capa, llamada Distributed IPC Facility (DIF), realiza el mismo conjunto de tareas. Mientras realizan las mismas tareas, las DIF de RINA son completamente configurables por medio de políticas programables, definiciones de cómo realizar tales tareas. Además, RINA brinda soporte completo para servicios de QoS por medio de los Cubos QoS, o clases de QoS que definen las capacidades de cada DIF. Con el uso de los Cubos QoS, RINA es capaz de proporcionar una forma estandarizada de expresar las capacidades de cada capa. Además, dada esa información, RINA también permite que las aplicaciones y los procesos de capas superiores expresen sus requisitos de QoS en términos de latencia aceptada, pérdidas, uso promedio, etc. Las contribuciones en esta tesis sacan provecho de la pila recursiva de RINA y el uso de políticas para proponer y analizar soluciones, antiguas y nuevas, para QoS y escalabilidad, que no serán compatibles con la Internet TCP/IP actual. En términos de mejoras de los servicios de QoS, el trabajo en esta tesis aprovecha la información sobre los requisitos de flujo, proporcionados por las propias aplicaciones, para mejorar las garantías de QoS proporcionadas por la red. Propone el uso de políticas basadas en △Q, proporcionando garantías de QoS mejoradas, que coinciden mejor con los requisitos de los flujos. A diferencia de las soluciones de diferenciación de QoS más simples, donde los servicios de QoS se proporcionan en orden de prioridad, △Q pretende proporcionar un servicio “suficientemente bueno" para todos los flujos en la red, lo que resulta en una repartición de recursos más apropiada. En este trabajo, estas políticas se han probado en redes tipo backbone, que muestran mejoras interesantes con respecto a las soluciones comunes de diferenciación de QoS, como las VPN basadas en MPLS. Además del uso de las políticas de △Q en el núcleo de la red, esta tesis también considera el suministro de servicios de QoS a los usuarios finales, siendo ese el objetivo final de las redes. Para permitir eso, se requiere imponer algunos límites a lo que los usuarios finales pueden enviar a la red, con el fin de limitar la cantidad de tráfico prioritario que usuarios codiciosos puedan enviar. En ese sentido, aunque imponer límites de velocidad estrictos por QoS sería trivial en RINA, también se explora una nueva política de limitación de tasas basada en △Q que pretende limitar la cantidad de tráfico prioritario de una manera más beneficiosa para los usuarios. En términos de escalabilidad, esta tesis también considera diferentes medidas para mejorar el reenvío y el enrutamiento dentro de redes de gran escala. Primero, en cuanto al uso de políticas que podrán beneficiarse de topologías de red específicas, se propone una nueva política de forwarding que combina reglas topológicas, es decir decisiones basadas en la ubicación de nodos, y excepciones, es decir entradas que sobrescriben reglas en caso de error. Con esta política, las costosas búsquedas en tablas grandes se reemplazan con reglas de rápidas y simples basadas en la ubicación de los nodos y su vecindad. Dadas las topologías específicas más comúnmente utilizadas en los grandes centros de datos hoy en día, se encuentra que el uso de la política propuesta es la combinación perfecta para esos escenarios. Pruebas en varias topologías comunes para centros de datos mostraron mejoras claras, que requieren solo una pequeña fracción de toda la información sobre la red, a pesar del gran tamaño de dichas redes, dependiendo esta de la cantidad de fallas concurrentes en la red y no del tamaño de la misma. Además, esta tesis también considera el uso de políticas de enrutamiento topológico para poblar tales excepciones en caso de fallas. El uso de soluciones de enrutamiento topológico dio como resultado la reducción de la complejidad en el cálculo de rutas, junto con un menor número de mensajes de enrutamiento. Además de las soluciones topológicas, también se investiga el uso de otra solución de enrutamiento, no adecuada para el entorno de IP. Específicamente, se muestra como una solución de enrutamiento Landmark, una solución de enrutamiento de la familia de enrutamiento compacto, podría implementarse dentro de RINA. Finalmente, también se dedican esfuerzos a analizar la importancia de la selección de rutas para garantizar los requisitos de QoS y como no se requiere llegar a soluciones extremas, como el uso de conexiones, para proporcionar los servicios requeridos.Postprint (published version

IP and ATM integration: A New paradigm in multi-service internetworking

ATM is a widespread technology adopted by many to support advanced data communication, in particular efficient Internet services provision. The expected challenges of multimedia communication together with the increasing massive utilization of IP-based applications urgently require redesign of networking solutions in terms of both new functionalities and enhanced performance. However, the networking context is affected by so many changes, and to some extent chaotic growth, that any approach based on a structured and complex top-down architecture is unlikely to be applicable. Instead, an approach based on finding out the best match between realistic service requirements and the pragmatic, intelligent use of technical opportunities made available by the product market seems more appropriate. By following this approach, innovations and improvements can be introduced at different times, not necessarily complying with each other according to a coherent overall design. With the aim of pursuing feasible innovations in the different networking aspects, we look at both IP and ATM internetworking in order to investigating a few of the most crucial topics/ issues related to the IP and ATM integration perspective. This research would also address various means of internetworking the Internet Protocol (IP) and Asynchronous Transfer Mode (ATM) with an objective of identifying the best possible means of delivering Quality of Service (QoS) requirements for multi-service applications, exploiting the meritorious features that IP and ATM have to offer. Although IP and ATM often have been viewed as competitors, their complementary strengths and limitations from a natural alliance that combines the best aspects of both the technologies. For instance, one limitation of ATM networks has been the relatively large gap between the speed of the network paths and the control operations needed to configure those data paths to meet changing user needs. IP\u27s greatest strength, on the other hand, is the inherent flexibility and its capacity to adapt rapidly to changing conditions. These complementary strengths and limitations make it natural to combine IP with ATM to obtain the best that each has to offer. Over time many models and architectures have evolved for IP/ATM internetworking and they have impacted the fundamental thinking in internetworking IP and ATM. These technologies, architectures, models and implementations will be reviewed in greater detail in addressing possible issues in integrating these architectures s in a multi-service, enterprise network. The objective being to make recommendations as to the best means of interworking the two in exploiting the salient features of one another to provide a faster, reliable, scalable, robust, QoS aware network in the most economical manner. How IP will be carried over ATM when a commercial worldwide ATM network is deployed is not addressed and the details of such a network still remain in a state of flux to specify anything concrete. Our research findings culminated with a strong recommendation that the best model to adopt, in light of the impending integrated service requirements of future multi-service environments, is an ATM core with IP at the edges to realize the best of both technologies in delivering QoS guarantees in a seamless manner to any node in the enterprise

Proceedings of the Second International Mobile Satellite Conference (IMSC 1990)

Presented here are the proceedings of the Second International Mobile Satellite Conference (IMSC), held June 17-20, 1990 in Ottawa, Canada. Topics covered include future mobile satellite communications concepts, aeronautical applications, modulation and coding, propagation and experimental systems, mobile terminal equipment, network architecture and control, regulatory and policy considerations, vehicle antennas, and speech compression