IP Flow Mobility support for Proxy Mobile IPv6 based networks

The ability of offloading selected IP data traffic from 3G to WLAN access networks is considered a key feature in the upcoming 3GPP specifications, being the main goal to alleviate data congestion in celular networks while delivering a positive user experience. Lately, the 3GPP has adopted solutions that enable mobility of IP-based wireless devices relocating mobility functions from the terminal to the network. To this end, the IETF has standardized Proxy Mobile IPv6 (PMIPv6), a protocol capable to hide often complex mobility procedures from the mobile devices. This thesis, in line with the mentioned offload requirement, further extends Proxy Mobile IPv6 to support dynamic IP flow mobility management across access wireless networks according to operator policies. In this work, we assess the feasibility of the proposed solution and provide an experimental analysis based on a prototype network setup, implementing the PMIPv6 protocol and the related enhancements for flow mobility support. *** La capacità di spostare flussi IP da una rete di accesso 3G ad una di tipo WLAN è considerata una caratteristica chiave nelle specifiche future di 3GPP, essendo il principale metodo per alleviare la congestione nelle reti cellulari mantenendo al contempo una ragionevole qualità percepita dall'utente. Recentemente, 3GPP ha adottato soluzioni di mobilità per dispositivi con accesso radio basato su IP, traslando le funzioni di supporto dal terminale alla rete, e, a questo scopo, IETF ha standardizzato Proxy Mobile IPv6 (PMIPv6), un protocollo studiato per nascondere le procedure di mobilità ai sistemi mobili. Questa tesi, in linea con la citata esigenza di spostare flussi IP, estende ulteriormente PMIPv6 per consentire il supporto alla mobilità di flussi tra diverse reti di accesso wireless, assecondando le regole e/o politiche definite da un operatore. In questo lavoro, ci proponiamo di asserire la fattibilità della soluzione proposta, fornendo un'analisi sperimentale di essa sulla base di un prototipo di rete che implementa il protocollo PMIPv6 e le relative migliorie per il supporto alla mobilità di flussiope

Improving Machine Learning Pipeline Creation using Visual Programming and Static Analysis

Tese de mestrado, Engenharia Informática (Engenharia de Software), Universidade de Lisboa, Faculdade de Ciências, 2021ML pipelines are composed of several steps that load data, clean it, process it, apply learning algorithms and produce either reports or deploy inference systems into production. In real-world scenarios, pipelines can take days, weeks, or months to train with large quantities of data. Unfortunately, current tools to design and orchestrate ML pipelines are oblivious to the semantics of each step, allowing developers to easily introduce errors when connecting two components that might not work together, either syntactically or semantically. Data scientists and engineers often find these bugs during or after the lengthy execution, which decreases their productivity. We propose a Visual Programming Language (VPL) enriched with semantic constraints regarding the behavior of each component and a verification methodology that verifies entire pipelines to detect common ML bugs that existing visual and textual programming languages do not. We evaluate this methodology on a set of six bugs taken from a data science company focused on preventing financial fraud on big data. We were able detect these data engineering and data balancing bugs, as well as detect unnecessary computation in the pipelines

Hierarchical Inter-Regional Routing Algorithm for Interplanetary Networks

Le comunicazioni interplanetarie sono caratterizzate da lunghi ritardi, perdite elevate e connettività intermittente con frequenti interruzioni. Lo stack TCP/IP è inadatto nell'affrontare questo tipo di problemi. Mentre inizialmente l'unico scenario di riferimento erano le comunicazioni interplanetarie, negli anni successivi è nato il termine "Challenged Networks" per identificare le reti in cui i protocolli tradizionali falliscono. L'idea si evolve così in Delay/Disruption Tolerant Networking(DTN), con l'obiettivo di fornire una soluzione adatta alle challenged network. Tra i vari aspetti in cui le reti DTN differiscono dai protocolli TCP/IP abbiamo il modo in cui viene effettuato routing. L'attuale algoritmo di routing utilizzato proposto per le reti DTN è chiamato Contact Graph Routing(CGR). L'aspetto che contraddistingue il CGR dagli algoritmi di routing tradizionali è che esso costruisce una rotta di "contatti" (ovvero delle possibilità di comunicazione programmate), anzichè costruire un percorso di nodi. Questa caratteristica è efficace nell'ambito delle reti DTN, dove i contatti sono noti a priori. Nonostante il CGR sia molto efficiente, esso presenta dei problemi di scalabilità. Infatti, con l'aumentare del numero dei contatti, il suo tempo di esecuzione tende a crescere fino a degradare le prestazioni dell'intera rete. In questa tesi viene proposto un algoritmo di routing chiamato Hierarchical Inter-regional Routing (HIRR) che ha l'obiettivo di mitigare il problema di scalabilità del CGR dividendo i nodi della rete in diverse regioni amministrative, in cui l'utilizzo del CGR non risulta essere critico. Lo scopo principale di HIRR è quindi quello di cercare di trarre il massimo beneficio dal CGR, accettando un ragionevole compromesso fra ottimalità delle rotte e tempo di calcolo. Questa tesi è stata svolta al NASA Jet Propulsion Laboratory(JPL) situato a Pasadena in California, aderendo al Visiting Student Research Program (VSRP)

Towards a secure cooperation mechanism for Challenging Networks

A Challenging Network (CN) is a network paradigm adapting to the many issues of the environment in order to guarantee the communication among nodes. One of the most important issues of a CN is the problem of secure cooperation among nodes. In fact, an attacker, either internal or external, may constitute a threat for the network. In this work I investigate the problem of secure cooperation in three kinds of CNs: the Underwater Acoustic Net- works (UANs), the Delay Tolerant Networks (DTNs) and the Publish/Subscribe Networks (PSNs). A UAN is a network paradigm allowing communication among underwater nodes equipped with acoustic modems. Since the acoustic channel is an open medium, an attacker conveniently equipped could intercept the messages traversing the network. In this work I describe a cryptographic suite, aimed at protecting the communication among underwater acoustic nodes. A DTN is a network paradigm guaranteeing message delivery even in presence of network partitions. A DTN relies on the implicit assumption that nodes cooperate towards message forwarding. However, this assumption cannot be satisfied when there are malicious nodes acting as blackholes and voluntarily attracting and dropping messages. In this work I propose a reputation-based protocol for contrasting blackholes. A PSN is a network paradigm allowing communication from publishers to subscribers by means of an infrastructure, called Dispatcher. In this work I present a secure PSN conceived to support cooperation be- tween organizations. The service is based on the notion of security group, an overlay composed of brokers representing organizations that guarantees confidentiality and integrity in end-to-end delivery of messages and supports clients mobility

Modeling pollutant dispersion at the city and street scales: from wind tunnel experiments to complex network theory

L'abstract è presente nell'allegato / the abstract is in the attachmen

Second CLIPS Conference Proceedings, volume 1

Topics covered at the 2nd CLIPS Conference held at the Johnson Space Center, September 23-25, 1991 are given. Topics include rule groupings, fault detection using expert systems, decision making using expert systems, knowledge representation, computer aided design and debugging expert systems

A semantic web rule language for geospatial domains

Retrieval of geographically-referenced information on the Internet is now a common activity. The web is increasingly being seen as a medium for the storage and exchange of geographic data sets in the form of maps. The geospatial-semantic web (GeoWeb) is being developed to address the need for access to current and accurate geo-information. The potential applications of the GeoWeb are numerous, ranging from specialised application domains for storing and analysing geo-information to more common applications by casual users for querying and visualising geo-data, e.g. finding locations of services, descriptions of routes, etc. Ontologies are at the heart of W3C's semantic web initiative to provide the necessary machine understanding to the sheer volumes of information contained on the internet. For the GeoWeb to succeed the development of ontologies for the geographic domain are crucial. Semantic web technologies to represent ontologies have been developed and standardised. OWL, the Web Ontology Language, is the most expressive of these enabling a rich form of reasoning, thanks to its formal description logic underpinnings. Building geo-ontologies involves a continuous process of update to the originally modelled data to reflect change over time as well as to allow for ontology expansion by integrating new data sets, possibly from different sources. One of the main challenges in this process is finding means of ensuring the integrity of the geo-ontology and maintaining its consistency upon further evolution. Representing and reasoning with geographic ontologies in OWL is limited. Firstly, OWL is not an integrity checking language due to it's non-unique name and open world assumptions. Secondly, it can not represent spatial datatypes, can not compute information using spatial operators and does not have any form of spatial index. Finally, OWL does not support complex property composition needed to represent qualitative spatial reasoning over spatial concepts. To address OWL's representational inefficiencies, new ontology languages have been proposed based on the intersection or union of OWL (in particular the DL family corresponding to OWL) with logic programs (rule languages). In this work, a new Semantic Web Spatial Rule Language (SWSRL) is proposed, based on the syntactic core of the Description Logic Programs paradigm (DLP), and the semantics of a Logic Program. The language is built to support the expression of geospatial ontological axioms and geospatial integrity and deduction rules. A hybrid framework to integrate both qualitative symbolic information in SWSRL with quantitative, geometric information using spatial datatypes in a spatial database is proposed. Two notable features of SWSRL are 1) the language is based on a prioritised de fault logic that allows the expression of default integrity rules and their exceptions and 2) the implementation of the language uses an interleaved mode of inference for on the fly computation (either qualitative or quantitative) deduction of spatial relations. SWSRL supports an OGC complaint spatial syntax, and a standardised definition of rule meta data. Both features aid the construction, description, identification and categorisation of designed and implemented rules within large rule sets. The language and the developed engine are evaluated using synthetic as well as real data sets in the context of developing geographic ontologies for geographic information retrieval on the Semantic Web. Empirical experiments are also presented to test the scalability and applicability of the developed framework

A Functional, Comprehensive and Extensible Multi-Platform Querying and Transformation Approach

This thesis is about a new model querying and transformation approach called FunnyQT which is realized as a set of APIs and embedded domain-specific languages (DSLs) in the JVM-based functional Lisp-dialect Clojure. Founded on a powerful model management API, FunnyQT provides querying services such as comprehensions, quantified expressions, regular path expressions, logic-based, relational model querying, and pattern matching. On the transformation side, it supports the definition of unidirectional model-to-model transformations, of in-place transformations, it supports defining bidirectional transformations, and it supports a new kind of co-evolution transformations that allow for evolving a model together with its metamodel simultaneously. Several properties make FunnyQT unique. Foremost, it is just a Clojure library, thus, FunnyQT queries and transformations are Clojure programs. However, most higher-level services are provided as task-oriented embedded DSLs which use Clojure's powerful macro-system to support the user with tailor-made language constructs important for the task at hand. Since queries and transformations are just Clojure programs, they may use any Clojure or Java library for their own purpose, e.g., they may use some templating library for defining model-to-text transformations. Conversely, like every Clojure program, FunnyQT queries and transformations compile to normal JVM byte-code and can easily be called from other JVM languages. Furthermore, FunnyQT is platform-independent and designed with extensibility in mind. By default, it supports the Eclipse Modeling Framework and JGraLab, and support for other modeling frameworks can be added with minimal effort and without having to modify the respective framework's classes or FunnyQT itself. Lastly, because FunnyQT is embedded in a functional language, it has a functional emphasis itself. Every query and every transformation compiles to a function which can be passed around, given to higher-order functions, or be parametrized with other functions