Assessing the Performance of Virtualization Technologies for NFV: a Preliminary Benchmarking

The NFV paradigm transforms those applications executed for decades in dedicated appliances, into software images to be consolidated in standard server. Although NFV is implemented through cloud computing technologies (e.g., virtual machines, virtual switches), the network traffic that such components have to handle in NFV is different than the traffic they process when used in a cloud computing scenario. Then, this paper provides a (preliminary) benchmarking of the widespread virtualization technologies when used in NFV, which means when they are exploited to run the so called virtual network functions and to chain them in order to create complex services

Preface of the 31st Italian Symposium on Advanced Database Systems

This volume contains the proceedings of the 31st Italian Symposium on Advanced Database Systems (SEBD - Sistemi Evoluti per Basi di Dati), held in Galzinagno Terme (Padua, Italy) from 2 to 5 July 2023.</p

Preface of the 31st Italian Symposium on Advanced Database Systems

This volume contains the proceedings of the 31st Italian Symposium on Advanced Database Systems (SEBD - Sistemi Evoluti per Basi di Dati), held in Galzinagno Terme (Padua, Italy) from 2 to 5 July 2023.</p

Definition of new WAN paradigms enabled by smart measurements

Nowadays massive amounts of data are being moved over the Internet thanks to data-hungry applications, Big Data, and multimedia content. Combined with a reduction in cost and augmented reliability for high-speed broadband access, the whole Internet infrastructure is facing new challenges especially when information crosses long geographical distances. That is the case for Wide Area Networks (WANs), which are typically traversed in enterprises with multi-site deployments. When a connection is established between end-points that are geographically distant with high latency and high bandwidth, data is flowing over a so-called Long Fat Network. Currently, transport protocols in end-points are not able to exploit the resources of such links, notably the most common TCP implementations still stuffer from design flaws that limit their efficiency. More recent developments still suffer from low fairness in resource sharing and lack of global visibility. We identify SD-WAN as an SDN use-case that can enable new transport protocols adoption, improving traffic behavior over WANs, without the need to modify the end-points. In this thesis, we explore new approaches to network measurements that will enable both end-points and SD-WAN edge routers, to gain visibility over the end-to-end network status. Such additional visibility promotes the development of smarter control mechanisms for network traffic. The preliminary study carried on comprises TCP behavior over WANs and existing methodologies to control its traffic patterns and enforce rate throttling. We also identify a specific use case that poses challenges for WAN scenarios: the Split TCP connections in a Performance Enhancing Proxy (PEP). New control mechanisms to improve resource utilization and fairness are defined in this project. Specifically, we propose a new approach called Receive Window Modulation (RWM) that allows edge-routers to control the sending rate of a TCP connection by modifying the window advertised by the receiver. We prove that such a controller can improve TCP efficiency and fairness by leveraging local information and additional contextual information obtained from network measurements. It also provides a lossless throttling mechanism, allowing for policy enforcement without hindering TCP throughput. We validate RWM in a real experimental scenario, showing improvements of up to 70% in TCP throughput when coupled with loss-based congestion controls. Bufferbloat is also mitigated, reducing the end-to-end TCP latency measured almost three-fold in some scenarios. Another contribution of this project includes a new method to estimate network available bandwidth from TCP passive probings based on the statistical analysis of the Inter-Packet arrival time (SABES). The methodology is based on the packet dispersion model and takes advantage of state-of-the-art machine learning techniques to improve its accuracy, including Deep Neural Networks and Kernel Density Estimation. We validate the model in both simulations and real-world experiments, obtaining a median of the mean absolute error distribution of less than 10% of the network capacity. We study network capacity estimation and bottleneck detection with an innovative active probing approach called HIRE. We propose a new packet dispersion model that takes into account the packet pairs delay, allowing for precise end-to-end capacity estimation. HIRE also introduces the concept of Hidden packets Red-shift Effect, which consists of injecting TTL expiring packets in between probing pairs at a specific rate. This technique allows locating the narrow link position along the path. We validate the model in simulations obtaining an estimation error of less than 3% in most scenarios. All these contributions constitute the building blocks of a Stateful Edge Router Architecture, SERA. Such architecture is presented in the final part of the dissertation, preparing the ground for future developments.Hoy en día, Internet mueve cantidades considerables de datos debido a aplicaciones que requieren muchos datos (Big Data). En combinación con una reducción en los costes y un aumento en la fiabilidad de los enlaces de acceso a banda ancha, la infraestructura de Internet tiene que hacer frente a nuevos retos, especialmente cuando la información tiene que atravesar grandes distancias geográficas. Esto es el caso de las Redes de Area Extendida (WANs), que típicamente forman parte de la infraestructura de empresas con distintas sedes y oficinas. Hoy en día, los protocoles de transporto en los puntos finales no son capaces de explotar los recursos de las WANs, las mas comunes siendo implementaciones de TCP, las cuales todavía sufren de fallos en sus diseños que limitan la eficiencia. Desarrollos TCP recientes todavía no garantizan una repartición equitativa de los recursos de red y faltan de visibilidad global. Identificamos SD-WAN como un caso de uso el cual puede facilitar la adopción de nuevos protocoles de transporte, mejorando el comportamiento del trafico de red sobre WANs, sin la necesidad de modificar los puntos finales. En esta tesis exploramos nuevas propuestas en el campo de las medidas de red, las cuales permiten tanto a puntos finales como a router de borde, de ganar visibilidad sobre el estado de la red. Dicha visibilidad añadida permite el desarrollo de mecanismos de control del trafico de red mas inteligentes. Identificamos un caso de uso especifico que pone retos en los escenarios WAN: las conexiones Split TCP en el caso de un Performance Enhancing Proxy (PEP). En el proyecto vienen definidos nuevos mecanismos que mejoran la explotación y repartición de los recursos de red. En concreto, proponemos un nuevo esquema llamado Receive Window Modulation (RWM), que permite a los routers de borde controlar la ratio de envío de una conexión TCP modificando la ventana de recepción declarada por el recibidor. Probamos que dicho controlador puede mejorar la eficiencia y equidad de TCP, utilizando informaciones locales y de contexto obtenidas por medio de medidas de red. RWM también provee un mecanismo de control del trafico privo de perdidas sin dañar el rendimiento de TCP. Hemos validado RWM en un entorno experimental real, demostrando mejoras de hasta el 70% en el rendimiento de TCP. El fenómeno de bufferbloat también viene mitigado, reduciendo la latencia medida hasta tres veces en algunos escenarios. Hemos estudiado un método de estimación del ancho de banda disponible basado en el análisis estadístico de muestras de trafico TCP y de su tiempo de llegada entre paquetes, llamado SABES. La metodología se basa en modelo de dispersión de los paquetes y utiliza técnicas de aprendizaje automático para mejorar su precisión, incluyendo redes neurales profundas (DNN) y estimación de densidad de kernel (KDE). Hemos validado el modelo tanto en entornos simulados como en experimentos reales, obteniendo una mediana del error medio absoluto menor del 10% de la capacidad de red. También hemos estudiado la estimación de la capacidad de red y detección de cuellos de botella con una técnica innovadora que utiliza sondeo activo, que llamamos HIRE. Proponemos un nuevo modelo de dispersión de paquetes el cual tiene en cuenta la latencia de la pareja de paquetes, permitiendo estimar con elevada precisión la capacidad del camino. HIRE también introduce el concepto de Efecto de corrimiento al rojo para paquetes escondidos, el cual consiste en inyectar paquetes que caducaran debido a su TTL entre parejas de sondeo activo a una ratio de envío especifica. Esta técnica permite localizar la posición del enlace a capacidad menor en el camino. Hemos validado el modelo en entornos simulados obteniendo un error de estimación inferior al 3% en la mayoría de los escenarios. Una arquitectura que reúne todos los componentes introducidos viene presentada la parte final de la tesis, preparando el terreno para desarrollo de futuros desarrollosPostprint (published version

Definition of new WAN paradigms enabled by smart measurements

Nowadays massive amounts of data are being moved over the Internet thanks to data-hungry applications, Big Data, and multimedia content. Combined with a reduction in cost and augmented reliability for high-speed broadband access, the whole Internet infrastructure is facing new challenges especially when information crosses long geographical distances. That is the case for Wide Area Networks (WANs), which are typically traversed in enterprises with multi-site deployments. When a connection is established between end-points that are geographically distant with high latency and high bandwidth, data is flowing over a so-called Long Fat Network. Currently, transport protocols in end-points are not able to exploit the resources of such links, notably the most common TCP implementations still stuffer from design flaws that limit their efficiency. More recent developments still suffer from low fairness in resource sharing and lack of global visibility. We identify SD-WAN as an SDN use-case that can enable new transport protocols adoption, improving traffic behavior over WANs, without the need to modify the end-points. In this thesis, we explore new approaches to network measurements that will enable both end-points and SD-WAN edge routers, to gain visibility over the end-to-end network status. Such additional visibility promotes the development of smarter control mechanisms for network traffic. The preliminary study carried on comprises TCP behavior over WANs and existing methodologies to control its traffic patterns and enforce rate throttling. We also identify a specific use case that poses challenges for WAN scenarios: the Split TCP connections in a Performance Enhancing Proxy (PEP). New control mechanisms to improve resource utilization and fairness are defined in this project. Specifically, we propose a new approach called Receive Window Modulation (RWM) that allows edge-routers to control the sending rate of a TCP connection by modifying the window advertised by the receiver. We prove that such a controller can improve TCP efficiency and fairness by leveraging local information and additional contextual information obtained from network measurements. It also provides a lossless throttling mechanism, allowing for policy enforcement without hindering TCP throughput. We validate RWM in a real experimental scenario, showing improvements of up to 70% in TCP throughput when coupled with loss-based congestion controls. Bufferbloat is also mitigated, reducing the end-to-end TCP latency measured almost three-fold in some scenarios. Another contribution of this project includes a new method to estimate network available bandwidth from TCP passive probings based on the statistical analysis of the Inter-Packet arrival time (SABES). The methodology is based on the packet dispersion model and takes advantage of state-of-the-art machine learning techniques to improve its accuracy, including Deep Neural Networks and Kernel Density Estimation. We validate the model in both simulations and real-world experiments, obtaining a median of the mean absolute error distribution of less than 10% of the network capacity. We study network capacity estimation and bottleneck detection with an innovative active probing approach called HIRE. We propose a new packet dispersion model that takes into account the packet pairs delay, allowing for precise end-to-end capacity estimation. HIRE also introduces the concept of Hidden packets Red-shift Effect, which consists of injecting TTL expiring packets in between probing pairs at a specific rate. This technique allows locating the narrow link position along the path. We validate the model in simulations obtaining an estimation error of less than 3% in most scenarios. All these contributions constitute the building blocks of a Stateful Edge Router Architecture, SERA. Such architecture is presented in the final part of the dissertation, preparing the ground for future developments.Hoy en día, Internet mueve cantidades considerables de datos debido a aplicaciones que requieren muchos datos (Big Data). En combinación con una reducción en los costes y un aumento en la fiabilidad de los enlaces de acceso a banda ancha, la infraestructura de Internet tiene que hacer frente a nuevos retos, especialmente cuando la información tiene que atravesar grandes distancias geográficas. Esto es el caso de las Redes de Area Extendida (WANs), que típicamente forman parte de la infraestructura de empresas con distintas sedes y oficinas. Hoy en día, los protocoles de transporto en los puntos finales no son capaces de explotar los recursos de las WANs, las mas comunes siendo implementaciones de TCP, las cuales todavía sufren de fallos en sus diseños que limitan la eficiencia. Desarrollos TCP recientes todavía no garantizan una repartición equitativa de los recursos de red y faltan de visibilidad global. Identificamos SD-WAN como un caso de uso el cual puede facilitar la adopción de nuevos protocoles de transporte, mejorando el comportamiento del trafico de red sobre WANs, sin la necesidad de modificar los puntos finales. En esta tesis exploramos nuevas propuestas en el campo de las medidas de red, las cuales permiten tanto a puntos finales como a router de borde, de ganar visibilidad sobre el estado de la red. Dicha visibilidad añadida permite el desarrollo de mecanismos de control del trafico de red mas inteligentes. Identificamos un caso de uso especifico que pone retos en los escenarios WAN: las conexiones Split TCP en el caso de un Performance Enhancing Proxy (PEP). En el proyecto vienen definidos nuevos mecanismos que mejoran la explotación y repartición de los recursos de red. En concreto, proponemos un nuevo esquema llamado Receive Window Modulation (RWM), que permite a los routers de borde controlar la ratio de envío de una conexión TCP modificando la ventana de recepción declarada por el recibidor. Probamos que dicho controlador puede mejorar la eficiencia y equidad de TCP, utilizando informaciones locales y de contexto obtenidas por medio de medidas de red. RWM también provee un mecanismo de control del trafico privo de perdidas sin dañar el rendimiento de TCP. Hemos validado RWM en un entorno experimental real, demostrando mejoras de hasta el 70% en el rendimiento de TCP. El fenómeno de bufferbloat también viene mitigado, reduciendo la latencia medida hasta tres veces en algunos escenarios. Hemos estudiado un método de estimación del ancho de banda disponible basado en el análisis estadístico de muestras de trafico TCP y de su tiempo de llegada entre paquetes, llamado SABES. La metodología se basa en modelo de dispersión de los paquetes y utiliza técnicas de aprendizaje automático para mejorar su precisión, incluyendo redes neurales profundas (DNN) y estimación de densidad de kernel (KDE). Hemos validado el modelo tanto en entornos simulados como en experimentos reales, obteniendo una mediana del error medio absoluto menor del 10% de la capacidad de red. También hemos estudiado la estimación de la capacidad de red y detección de cuellos de botella con una técnica innovadora que utiliza sondeo activo, que llamamos HIRE. Proponemos un nuevo modelo de dispersión de paquetes el cual tiene en cuenta la latencia de la pareja de paquetes, permitiendo estimar con elevada precisión la capacidad del camino. HIRE también introduce el concepto de Efecto de corrimiento al rojo para paquetes escondidos, el cual consiste en inyectar paquetes que caducaran debido a su TTL entre parejas de sondeo activo a una ratio de envío especifica. Esta técnica permite localizar la posición del enlace a capacidad menor en el camino. Hemos validado el modelo en entornos simulados obteniendo un error de estimación inferior al 3% en la mayoría de los escenarios. Una arquitectura que reúne todos los componentes introducidos viene presentada la parte final de la tesis, preparando el terreno para desarrollo de futuros desarrollo

Il fantasma della libertà. Libertà e vincoli in un role-playing

Due metodologie di analisi del testo (process research in psicoterapia), rispettivamente di tipo cognitivista e psicodinamico, sono state impiegate per indagare le dinamiche di gruppo di una seduta gruppo-analitica

Assessment of agro-ecological service crop managements combined with organic fertilisation strategies in organic melon crop

In organic horticultural systems, cover crops could provide several ecological services, therefore, they can be defined agroecological service crops (ASCs). The objective of this two-year research was to study the suitability on melon production of different ASC termination strategies, in combination with organic fertilisers application. In a split-block design, the main-plot was the ASC management, comparing: i) green manure, in which the vetch was chopped and plowed into the soil; and ii) roller-crimper (RC), in which the vetch was flattened by a roller-crimper; with iii) fallow control, without vetch. The subplot consisted of offfarm organic inputs: i) commercial humified fertiliser; ii) anaerobic digestate fertiliser; iii) composted municipal solid wastes; which were compared to iv) unfertilised control (N0). At vetch termination, above soil biomass and nitrogen (N) content were determined. At harvesting, crop yield performance and quality, N status and N efficiency were investigated. Also, main soil characteristics were assessed at the end of the trial. Among the ASC managements, the slightly reduced yield in the RC plots particularly in combination with N0 might have been the result of less N supplied by the vetch during the melon cycle. Anyway, no negative effects were observed for yield quality. The use of the RC showed a great potential in enhancing soil fertility. Our study suggests the suitability in organic farming of properly matching management of ASC and fertilisation strategies on melon crop

Recycling Agricultural Wastes and By-products in Organic Farming: Biofertilizer Production, Yield Performance and Carbon Footprint Analysis

The Circular Economy concept implies the re-design of existing production systems in agriculture, by promoting agricultural waste recycling. In an organic zucchini—lettuce rotation, two different agroecological tools were considered: biofertilizer and presence or absence of green manure (GM+ and GM−). In particular, we compared: (i) anaerobic digestate from cattle manure, co-composted with vegetable wastes, with the presence of GM (AD GM+); (ii) olive pomace compost, re-composted, with the presence of GM (OWC GM+); (iii) municipal waste compost with GM (MWC GM+); (iv) municipal waste compost without GM (MWC GM−). These materials were tested with a commercial organic fertilizer without GM (COF GM−) as a positive control. The objectives were: (i) assessing the environmental sustainability of biofertilizers through carbon footprint analysis by greenhouse gas—GHG—emissions; (ii) evaluating the agronomic performance on the vegetable rotation, by energy output assessment. The total carbon emissions of biofertilizers production was 63.9 and 67.0 kg of CO2 eq Mg−1 for AD and OWC, respectively. The co-composting and re-composting processes emitted 31.4 and 8.4 kg CO2 per Mg of compost, respectively. In AD the ventilation phase of composting accounted for 37.2% of total emissions. The total CO2 emission values for the two-crop cycles were the highest in COF GM− and the lowest in OWC GM+, due to different fertilizer sources. On the average of the treatments, the input that induced the highest CO2 emission was irrigation (37.9%). The energy output assessment for zucchini and lettuce highlighted similar performance for all the treatments. Our findings demonstrated the validity of the tested processes to recycle agro-industrial wastes, and the potential of agroecological practices (GM) to mitigate GHG emissions

HIRE: Hidden Inter-packet Red-shift Effect

Over the years, different techniques have been proposed to detect bottleneck bandwidth and available bandwidth of an end-to-end path. However, to the author's knowledge, no work has been conducted on detecting which link or node on the path could be the narrow link. In this paper, we present a novel technique based on packet pairs dispersion analysis, whose objective is twofold: first, it allows to estimate the narrow link capacity using a new approach which takes into account both inter-packet time and packet propagation delay. Its second objective is to induce the specific hop in the end-to-end path which represents the narrow link. This is achieved by injecting packets trains with intermediate TTL-expiring packets which decrease the train rate when they cross the narrow link (red-shift effect). We validate our approach in simulations showing the tool robustness in very complex scenarios.This work was supported by the Industrial PhD grant 2015DI023 of AGAUR and Gencat and the project Efficient Smart Multi Connected Networks co-financed by the Spanish Ministry of Ciencia Innovacion y Universidades with reference RTC-2017-6655-7, The Spanish Agenda Estatal de Investigacin and the European Regional Development Fund (FEDER).Peer ReviewedPostprint (author's final draft