The prevalence of multicore architectures has accentuated the need for scalable on-chip communication media. Various parallel applications and programming paradigms use a mix of unicast (one-to-one) and multicast (one-to-many) to maintain data coherence and consistency. Providing efficient support for these communication patterns becomes a critical design point for on-chip networks (OCN). High performance on-chip networks design advocates balanced traffic across the whole network, which makes adaptive routing appealing. Adaptive routing explores the path diversity of the network, increases throughput, and reduces network latency compared with oblivious routing. In this work, we propose an adaptive multicast routing, Balanced Recursive Partitioning Multicast (B-RPM), to achieve balanced one-to-many on-chip communication. The algorithm derives its functionality from previously proposed algorithm Recursive Partitioning Multicast (RPM). Unlike RPM which uses fixed set of directional priorities and position of destination nodes, B-RPM replicates packet based on the local congestion information and position of destination nodes with respect to current node. B-RPM employs a new deadlock avoidance technique Dynamically Sized Virtual Networks (DSVN). Built upon the traditional virtual networks, DSVN dynamically allocates the network resources to different VNs according to the run-time traffic status, which delivers better resources utilization. We also propose a new scheme for representing multiple destinations in packet head. The scheme works simply by differentiating multicast and unicast packets. The algorithm combined with dynamically sized virtual networks enables us to improve network performance at high load on average by 20% (up to 50%) and saturation throughput of network on average by 10% (up to 18%) over the most recent multicast algorithm. Also the new header representation scheme enables us to save 24% of dynamic link power.

The success of the internet over last few decades has mainly depended on various infrastructure technologies to run distributed applications. Due to diversification and multi-provider nature of the internet, radical architectural improvements which require mutual agreement between infrastructure providers have become highly impractical. This escalating resistance towards the further growth has created a rising demand for new approaches to address this challenge. Network virtualization is regarded as a prominent solution to surmount these limitations. It decouples the conventional Internet service provider’s role into infrastructure provider (InP) and service provider (SP) and introduce a third player known as virtual network Provider (VNP) which creates virtual networks (VNs). Resource discovery aims to assist the VNP in selecting the best InP that has the best matching resources for a particular VN request. In the current literature, resource discovery focuses mainly on static attributes of network resources highlighting the fact that utilization on dynamic attributes imposes significant overhead on the network itself. In this thesis we propose a resource discovery approach that is capable of utilizing the dynamic resource attributes to enhance the resource discovery and increase the overall efficiency of VN creation. We realize that recourse discovery techniques should be fast and cost efficient, enough to not to impose any significant load. Hence our proposed scheme calculates aggregation values of the dynamic attributes of the substrate resources. By comparing aggregation values to VN requirements, a set of potential InPs is selected. The potential InPs satisfy basic VN embedding requirements. Moreover, we propose further enhancements to the dynamic attribute monitoring process using a vector based aggregation approach.

A indústria da construção civil constitui um importante setor para a economia nacional, demandando diversos insumos e destacando-se pela atividade intensiva que, conseqüentemente, gera riquezas em uma longa e complexa cadeia de fornecedores. O modo de operação adotado é semelhante ao das organizações virtuais, porém ainda de forma não estruturada, deixando, portanto, de proporcionar muitas vantagens competitivas. Para tanto, o trabalho propõe o modelo de requisitos e componentes técnicos, baseado na metodologia EKD (Enterprise Knowledge Development), para auxiliar a formação e gerência de redes entre empresas da construção civil. Este modelo proporcionará, aos envolvidos no projeto, uma clara visão dos requisitos necessários para a estruturação de um futuro sistema de informação, além de explorar a necessidade de intensa comunicação e troca de informações entre parceiros. Para a elaboração do modelo proposto, será conduzida uma análise dos projetos internacionais mais relevantes da construção desenvolvidos, a fim de detectar seus objetivos e pontos falhos a serem reestruturados e adaptados para a indústria da construção civil brasileira. Da mesma forma, o modelo proposto basear-se-á, também, em uma adaptação de uma arquitetura de referência para redes da construção civil. / The civil construction industry constitutes an important sector for the national economy, demanding many inputs and being distinguished for the intensive activity that, consequently, generates wealth in a long and complex supplier\'s chain. The adopted way of operation is similar to the one of the virtual organizations, however still of not structuralized form, leaving, therefore, to provide many competitive advantages. For in such a way, the work considers the technical requirements and components model, based on EKD methodology (Enterprise Knowledge Development), to assist the formation and management of nets between companies of the civil construction. This model will provide, to the involved ones in the project, a clear vision of the necessary requirements for the construction of a future information system, besides exploring the necessity of intense communication and information exchange between partners. For the elaboration of the considered model, an analysis of the betters international projects developed of the construction will be lead, in order to detect its objectives and defective points to be reorganized and suitable for the brazilian industry of civil construction. In the same way, the considered model will be based in an adaptation of a reference\'s architecture for nets of the civil construction.

The success of the internet over last few decades has mainly depended on various infrastructure technologies to run distributed applications. Due to diversification and multi-provider nature of the internet, radical architectural improvements which require mutual agreement between infrastructure providers have become highly impractical. This escalating resistance towards the further growth has created a rising demand for new approaches to address this challenge. Network virtualization is regarded as a prominent solution to surmount these limitations. It decouples the conventional Internet service provider’s role into infrastructure provider (InP) and service provider (SP) and introduce a third player known as virtual network Provider (VNP) which creates virtual networks (VNs). Resource discovery aims to assist the VNP in selecting the best InP that has the best matching resources for a particular VN request. In the current literature, resource discovery focuses mainly on static attributes of network resources highlighting the fact that utilization on dynamic attributes imposes significant overhead on the network itself. In this thesis we propose a resource discovery approach that is capable of utilizing the dynamic resource attributes to enhance the resource discovery and increase the overall efficiency of VN creation. We realize that recourse discovery techniques should be fast and cost efficient, enough to not to impose any significant load. Hence our proposed scheme calculates aggregation values of the dynamic attributes of the substrate resources. By comparing aggregation values to VN requirements, a set of potential InPs is selected. The potential InPs satisfy basic VN embedding requirements. Moreover, we propose further enhancements to the dynamic attribute monitoring process using a vector based aggregation approach.

Οι επιχειρηματικές οργανωτικές δομές ιστορικά έχουν πάρει πολλαπλές μορφές. Η πολυμορφία αυτή που παρουσιάζεται στο πέρασμα του χρόνου είναι αποτέλεσμα της προσπάθειας των επιχειρήσεων να ανταποκριθούν στις αλλαγές που προέκυπταν κάθε φορά στο επιχειρηματικό περιβάλλον και στις απαιτήσεις του καταναλωτικού κοινού καθώς και να ικανοποιήσουν τις οργανωτικές και διοικητικές ανάγκες που έθετε η συνεχής και ραγδαία εξέλιξη της τεχνολογίας και κατ’ επέκταση της παραγωγικής διαδικασίας. Κραταιά θέση κατείχε παραδοσιακά το πυραμιδικό ιεραρχικό μοντέλο που χαρακτηριζόταν από την κάθετη ολοκλήρωση του έργου και ανταποκρινόταν επαρκώς στην ανάγκη της μαζικής παραγωγής και του συντονισμού των ιδιαιτέρως σύνθετων παραγωγικών διαδικασιών. Το μοντέλο αυτό γνώρισε συνεχή εξέλιξη στην διάρκεια των δεκαετιών από το τέλος του Β 'Παγκοσμίου Πολέμου μέχρι και τον 20ο αιώνα. Με το πέρασμα των χρόνων εμφανίζονται διάφορες νέες παραλλαγές του παραδοσιακού προτύπου οι οποίες διακρίνονται για τις πεπλατυσμένες δομές τους. Αυτά τα μοντέλα πέρα από την ενθάρρυνση και προώθηση της εξειδίκευσης, εισάγουν την συμμετοχική λήψη αποφάσεων και την αυξημένη αυτονομία ακόμη και σε κατώτερα οργανωτικά στρώματα. Σαν αποτέλεσμα της ανάπτυξης του συγκεκριμένου προτύπου οργάνωσης προκύπτει η σημαντική μείωση της γραφειοκρατίας, η ευελιξία και η ταχύτερη απόκριση των επιχειρήσεων αλλά κυρίως παρατηρείται το φαινόμενο της γεωγραφικής και οργανωτικής διασποράς των εργαζομένων. Ακολούθως, τα νέα απαιτητικά επιχειρηματικά δεδομένα που κάνουν την εμφάνισή τους στις αρχές του 21ου αιώνα σε συνδυασμό με την ταυτόχρονη ραγδαία τεχνολογική εξέλιξη αναδεικνύουν το εικονικό οργανωτικό μοντέλο, το οποίο απαντά στην πολυπλοκότητα και τον ‘άγριο’ ανταγωνισμό, αναπτύσσοντας δίκτυα συμμαχικών επιχειρήσεων, ομάδων και ατόμων, με σκοπό να εκμεταλλευτούν Ακολούθως, τα νέα απαιτητικά επιχειρηματικά δεδομένα που κάνουν την εμφάνισή τους στις αρχές του 21ου αιώνα σε συνδυασμό με την ταυτόχρονη ραγδαία τεχνολογική εξέλιξη αναδεικνύουν το εικονικό οργανωτικό μοντέλο, το οποίο απαντά στην πολυπλοκότητα και τον ‘άγριο’ ανταγωνισμό, αναπτύσσοντας δίκτυα συμμαχικών επιχειρήσεων, ομάδων και ατόμων, με σκοπό να εκμεταλλευτούν νεοεμφανιζόμενες ευκαιρίες, εκμεταλλευόμενες τους κοινούς πλέον πόρους του εικονικού δικτύου. Έτσι λοιπόν το εικονικό οργανωτικό μοντέλο διαμορφώνει Εικονικές Επιχειρήσεις (Virtual Firms) (Virtual Organizations) (Virtual Enterprises). Αναφορικά με τον ορισμό της Εικονικής Επιχείρησης οι απόψεις δεν εμφανίζουν ομοφωνία συγκλίνοντας όμως στα κοινά χαρακτηριστικά που αναπτύσσονται από τους διαφωνούντες θεωρητικούς, η εικονική επιχείρηση αποτελεί ένα δίκτυο ανεξάρτητων επιχειρήσεων με τη σύνθεση του οποίου επιδιώκεται να αναπτυχθούν συνέργιες, οι εταιρίες του δικτύου λειτουργικά συνδέονται με ένα κεντρικό εκτελεστικό φορέα λόγω της εκτεταμένης ανάπτυξης των Τηλεπικοινωνιών και της Πληροφορικής για την επίτευξη ενός κοινού σκοπού. Η θεωρία που σχετίζεται με την εικονικότητα και ειδικότερα με την συγκεκριμένη υβριδική μορφή επιχείρησης παρουσιάζει και προσεγγίζει τα ιδιαίτερα χαρακτηριστικά. Συμπερασματικά και με γνώμονα την μακροσκελή ανάλυση που έγινε τόσο αναφορικά με την εικονική μορφή οργάνωσης, τα πλεονεκτήματα και τις συνέργειες που μπορεί να δημιουργηθούν στα πλαίσιά της, όσο και αναφορικά με την οικονομική θεωρία και τα μεγέθη που παρουσιάζουν αδυναμία και επομένως χρειάζονται υποστήριξη ακολουθεί η παρατήρηση ορισμένων κοινών σημείων. / The business organizational structures historically have taken multiple forms. This diversity presented in the passage of time is a result of the efforts of companies to respond to changes resulting each time in the business environment and demands of consumers and to meet the organizational and management needs posed by the continuous and rapid development of technology and hence the production process. The result of the increasing demand of the business world is the creation and development a virtual model of organization. The purpose of this study is documentation of the ways in which the virtual model of organization can contribute to the effort of modern economic units to survive in times of economic crisis, as these units are formed in globalized markets. Mighty position was held traditionally by the hierarchical pyramid model characterized by vertical integration of the project and adequate response to the needs of mass production and coordination of the highly complex production processes. This model has seen continuous development during the decades since the end of WWII until the 20th century. Over the years there were displayed several new variants of the traditional pattern which were characterized by their flat structures. These models except of encouraging and promoting specialization they introduced participatory decision making and increased autonomy, even at lower organizational strata., new demanding business data that m As a result of the development of that certain organization model, occurs a significant reduction of bureaucracy, flexibility and faster response to business but mainly the phenomenon of geographical and organizational dispersion of employees. Subsequentlyake their appearance in the early 21st century along with the rapid technological developments highlight the virtual organization model, which responds to the complexity and 'wild' competition, developing networks of allied businesses, groups and people in order to exploit emerging opportunities, exploiting the most common resources of the virtual network. So the virtual organizational model creates (Virtual Firms) or (Virtual Organizations) or (Virtual Enterprises). Regarding the definition of the virtual enterprise views show no consensus, however, converging on common characteristics developed by dissident theorists, the virtual enterprise is a network of independent firms whose synthesis seeks to develop synergies, the companies operating the network are associated with a central executive body due to the extensive development of Telecommunications and Information Technology in order to achieve a common goal. The theory associated with virtualization and especially with this hybrid form of business presents approximate characteristics. In conclusion and having regard to the lengthy analysis in relation to both the virtual form of organization, the benefits and synergies that may arise, and also in terms of economic theory and its weak figures that need support, an observation of some common points will follow. These common findings emerge and are documented as a result of the study one can leverage the operational and strategic business development in times of economic crisis and also constitute the most characteristic features of virtual enterprises and forms that can be taken.

A indústria da construção civil constitui um importante setor para a economia nacional, demandando diversos insumos e destacando-se pela atividade intensiva que, conseqüentemente, gera riquezas em uma longa e complexa cadeia de fornecedores. O modo de operação adotado é semelhante ao das organizações virtuais, porém ainda de forma não estruturada, deixando, portanto, de proporcionar muitas vantagens competitivas. Para tanto, o trabalho propõe o modelo de requisitos e componentes técnicos, baseado na metodologia EKD (Enterprise Knowledge Development), para auxiliar a formação e gerência de redes entre empresas da construção civil. Este modelo proporcionará, aos envolvidos no projeto, uma clara visão dos requisitos necessários para a estruturação de um futuro sistema de informação, além de explorar a necessidade de intensa comunicação e troca de informações entre parceiros. Para a elaboração do modelo proposto, será conduzida uma análise dos projetos internacionais mais relevantes da construção desenvolvidos, a fim de detectar seus objetivos e pontos falhos a serem reestruturados e adaptados para a indústria da construção civil brasileira. Da mesma forma, o modelo proposto basear-se-á, também, em uma adaptação de uma arquitetura de referência para redes da construção civil. / The civil construction industry constitutes an important sector for the national economy, demanding many inputs and being distinguished for the intensive activity that, consequently, generates wealth in a long and complex supplier\'s chain. The adopted way of operation is similar to the one of the virtual organizations, however still of not structuralized form, leaving, therefore, to provide many competitive advantages. For in such a way, the work considers the technical requirements and components model, based on EKD methodology (Enterprise Knowledge Development), to assist the formation and management of nets between companies of the civil construction. This model will provide, to the involved ones in the project, a clear vision of the necessary requirements for the construction of a future information system, besides exploring the necessity of intense communication and information exchange between partners. For the elaboration of the considered model, an analysis of the betters international projects developed of the construction will be lead, in order to detect its objectives and defective points to be reorganized and suitable for the brazilian industry of civil construction. In the same way, the considered model will be based in an adaptation of a reference\'s architecture for nets of the civil construction.

The success of the internet over last few decades has mainly depended on various infrastructure technologies to run distributed applications. Due to diversification and multi-provider nature of the internet, radical architectural improvements which require mutual agreement between infrastructure providers have become highly impractical. This escalating resistance towards the further growth has created a rising demand for new approaches to address this challenge. Network virtualization is regarded as a prominent solution to surmount these limitations. It decouples the conventional Internet service provider’s role into infrastructure provider (InP) and service provider (SP) and introduce a third player known as virtual network Provider (VNP) which creates virtual networks (VNs). Resource discovery aims to assist the VNP in selecting the best InP that has the best matching resources for a particular VN request. In the current literature, resource discovery focuses mainly on static attributes of network resources highlighting the fact that utilization on dynamic attributes imposes significant overhead on the network itself. In this thesis we propose a resource discovery approach that is capable of utilizing the dynamic resource attributes to enhance the resource discovery and increase the overall efficiency of VN creation. We realize that recourse discovery techniques should be fast and cost efficient, enough to not to impose any significant load. Hence our proposed scheme calculates aggregation values of the dynamic attributes of the substrate resources. By comparing aggregation values to VN requirements, a set of potential InPs is selected. The potential InPs satisfy basic VN embedding requirements. Moreover, we propose further enhancements to the dynamic attribute monitoring process using a vector based aggregation approach.

Computer networks were not designed with security in mind, making research into the subject of network security vital. Virtual Networks are similar to computer networks, except the components of a Virtual Network are in software rather than hardware. With the constant threat of attacks on networks, security is always a big concern, and Virtual Networks are no different. Virtual Networks have many potential attack vectors similar to physical networks, making research into Virtual Network security of great importance. Virtual Networks, since they are composed of virtualized network components, have the ability to dynamically change topologies. In this paper, we explore Virtual Networks and their ability to quickly shift their network topology. We investigate the potential use of this flexibility to protect network resources and defend against malicious activities. To show the ability of reactively shifting a Virtual Network’s topology to se- cure a network, we create a set of four experiments, each with a different dynamic topology shift, or “dynamic defense”. These four groups of experiments are called the Server Protection, Isolated Subnet, Distributed Port Group, and Standard Port Group experiments. The Server Protection experiments involve detecting an attack against a server and shifting the server behind a protected subnet. The other three sets of experiments, called Attacker Prevention experiments, involve detecting a malicious node in the internal network and initiating a dynamic de- fense to move the attacker behind a protected subnet. Each Attacker Prevention experiment utilizes a different dynamic defense to prevent the malicious node from attacking the rest of the Virtual Network. For each experiment, we run 6 different network attacks to validate the effectiveness of the dynamic defenses. The network attacks utilized for each experiment are ICMP Flooding, TCP Syn Flooding, Smurf attack, ARP Spoofing, DNS Spoofing, and NMAP Scanning. Our validation shows that our dynamic defenses, outside of the standard port group, are very effective in stopping each attack, consistently lowering the at- tacks’ success rate significantly. The Standard Port Group was the one dynamic defense that is ineffective, though there are also a couple of experiments that could benefit from being run with more attackers and with different situations to fully understand the effectiveness of the defenses. We believe that, as Virtual Networks become more common and utilized outside of data centers, the ability to dynamically shift topology can be used for network security purposes.

The current Internet architecture presents a barrier to accommodate the vigorous arising demand for deploying new network services and applications. The next-generation architecture views the network virtualization as the gateway to overcome this limitation. Network virtualization promises to run efficiently and securely multiple dedicated virtual networks (VNs) over a shared physical infrastructure. Each VN is tailored to host a unique application based on the user’s preferences. This thesis addresses the problem of the efficient embedding of multiple VNs onto a shared substrate network (SN). The contribution of this thesis are twofold: First, a novel hierarchical SN management framework is proposed that efficiently selects the optimum VN mapping scheme for the requested VN from more than one proposed VN mapping candidates obtained in parallel. In order to accommodate the arbitrary architecture of the VNs, the proposed scheme divides the VN request into smaller subgraphs, and individually maps them on the SN using a variation of the exact subgraph matching techniques. Second, the physical resources pricing policy is introduced that is based on time-ofuse, that reflects the effect of resource congestion introduced by VN users. The preferences of the VN users are first represented through corresponding demand-utility functions that quantify the sensitivity of the applications hosted by the VNs to resource consumption and time-of-use. A novel model of time-varying VNs is presented, where users are allowed to up- or down-scale the requested resources to continuously maximize their utility while minimizing the VNs embedding cost. In contrast to existing solutions, the proposed work does not impose any limitations on the size or topology of the VN requests. Instead, the search is customized according to the VN size and the associated utility. Extensive simulations are then conducted to demonstrate the improvement achieved through the proposed work in terms of network utilization, the ratio of accepted VN requests and the SP profits.

The current Internet architecture presents a barrier to accommodate the vigorous arising demand for deploying new network services and applications. The next-generation architecture views the network virtualization as the gateway to overcome this limitation. Network virtualization promises to run efficiently and securely multiple dedicated virtual networks (VNs) over a shared physical infrastructure. Each VN is tailored to host a unique application based on the user’s preferences. This thesis addresses the problem of the efficient embedding of multiple VNs onto a shared substrate network (SN). The contribution of this thesis are twofold: First, a novel hierarchical SN management framework is proposed that efficiently selects the optimum VN mapping scheme for the requested VN from more than one proposed VN mapping candidates obtained in parallel. In order to accommodate the arbitrary architecture of the VNs, the proposed scheme divides the VN request into smaller subgraphs, and individually maps them on the SN using a variation of the exact subgraph matching techniques. Second, the physical resources pricing policy is introduced that is based on time-ofuse, that reflects the effect of resource congestion introduced by VN users. The preferences of the VN users are first represented through corresponding demand-utility functions that quantify the sensitivity of the applications hosted by the VNs to resource consumption and time-of-use. A novel model of time-varying VNs is presented, where users are allowed to up- or down-scale the requested resources to continuously maximize their utility while minimizing the VNs embedding cost. In contrast to existing solutions, the proposed work does not impose any limitations on the size or topology of the VN requests. Instead, the search is customized according to the VN size and the associated utility. Extensive simulations are then conducted to demonstrate the improvement achieved through the proposed work in terms of network utilization, the ratio of accepted VN requests and the SP profits.