Dissertations / Theses on the topic 'Caching services'

Applications for Internet-enabled devices use machine learning to process captured data to make intelligent decisions or provide information to users. Typically, the computation to process the data is executed in cloud-based backends. The devices are used for sensing data, offloading it to the cloud, receiving responses and acting upon them. However, this approach leads to high end-to-end latency due to communication over the Internet. This dissertation proposes reducing this response time by minimizing offloading, and pushing computation close to the source of the data, i.e. to edge servers and devices themselves. To adapt to the resource constrained environment at the edge, it presents an approach that leverages spatiotemporal locality to push subparts of the model to the edge. This approach is embodied in a distributed caching framework, Cachier. Cachier is built upon a novel caching model for recognition, and is distributed across edge servers and devices. The analytical caching model for recognition provides a formulation for expected latency for recognition requests in Cachier. The formulation incorporates the effects of compute time and accuracy. It also incorporates network conditions, thus providing a method to compute expected response times under various conditions. This is utilized as a cost function by Cachier, at edge servers and devices. By analyzing requests at the edge server, Cachier caches relevant parts of the trained model at edge servers, which is used to respond to requests, minimizing the number of requests that go to the cloud. Then, Cachier uses context-aware prediction to prefetch parts of the trained model onto devices. The requests can then be processed on the devices, thus minimizing the number of offloaded requests. Finally, Cachier enables cooperation between nearby devices to allow exchanging prefetched data, reducing the dependence on remote servers even further. The efficacy of Cachier is evaluated by using it with an art recognition application. The application is driven using real world traces gathered at museums. By conducting a large-scale study with different control variables, we show that Cachier can lower latency, increase scalability and decrease infrastructure resource usage, while maintaining high accuracy.

Les réseaux cellulaires ont connu une croissance phénoménale du trafic alimentée par les nouvelles technologies d'accès cellulaire. Cette croissance est en grande partie tirée par l'émergence du trafic HTTP adaptatif streaming (HAS) comme une nouvelle technologie de diffusion des contenus vidéo. Le principe du HAS est de rendre disponible plusieurs qualités de la même vidéo en ligne et que les clients choisissent la meilleure qualité qui correspond à leur bande passante. Chaque niveau d'encodage est segmenté en des chunks, qui dont la durée varie de 2 à 10 secondes. L'émergence du HAS a introduit des nouvelles contraintes sur les systèmes de livraison des contenus vidéo en particulier sur les systèmes de caches. Dans ce contexte, nous menons une analyse détaillée des données du trafic HAS collecté en France et fournie par le plus grand opérateur de téléphonie mobile du pays. Tout d'abord, nous analysons et modélisons le comportement des clients qui demandent des contenus VoD et live. Ces analyses nous ont permis d'identifier les facteurs qui impactent la performance des systèmes de cache et de proposer un nouveau algorithme de remplacement de contenus qu'on appelle WA-LRU. WA-LRU exploite la localité temporelle des chunks dans le contenu et la connaissance de la charge du trafic dans le réseau afin d'améliorer la performance du cache. Ensuite, nous analysons et modélisons la logique d'adaptation entre les qualités vidéo basés sur des observations empiriques. Nous montrons que le changement fréquent entre les encodages réduit considérablement la performance des systèmes de cache. Dans ce contexte, nous présentons CF-DASH une implémentation libre d'un player DASH qui vise à réduire les changements fréquents entre qualités, assure une bonne QoE des clients et améliore la performance des systèmes de caches. La deuxième partie de la thèse est dédié à la conception, simulation et implémentation d'une solution de préchargement des contenus vidéo sur terminaux mobiles. Nous concevons un système que nous appelons «Central Predictor System (CPsys)" qui prédit le comportement des clients mobiles et leurs consommations des vidéos. Nous évaluons CPSys avec des traces de trafic réel. Enfin, nous développons une preuve de concept de notre solution de préchargement
Recently, cellular networks have witnessed a phenomenal growth of traffic fueled by new high speed broadband cellular access technologies. This growth is in large part driven by the emergence of the HTTP Adaptive Streaming (HAS) as a new video delivery method. In HAS, several qualities of the same videos are made available in the network so that clients can choose the quality that best fits their bandwidth capacity. This strongly impacts the viewing pattern of the clients, their switching behavior between video qualities, and thus beyond on content delivery systems. In this context, we provide an analysis of a real HAS dataset collected in France and provided by the largest French mobile operator. Firstly, we analyze and model the viewing patterns of VoD and live streaming HAS sessions and we propose a new cache replacement strategy, named WA-LRU. WA-LRU leverages the time locality of video segments within the HAS content. We show that WA-LRU improves the performance of the cache. Second, we analyze and model the adaptation logic between the video qualities based on empirical observations. We show that high switching behaviors lead to sub optimal caching performance, since several versions of the same content compete to be cached. In this context we investigate the benefits of a Cache Friendly HAS system (CF-DASH) which aims at improving the caching efficiency in mobile networks and to sustain the quality of experience of mobile clients. Third, we investigate the mobile video prefetching opportunities. We show that CPSys can achieve high performance as regards prediction correctness and network utilization efficiency. We further show that CPSys outperforms other prefetching schemes from the state of the art. At the end, we provide a proof-of-concept implementation of our prefetching system

Latency is becoming a significant factor in many Internet applications such as P2P sharing and online gaming. Coupled with the fact that an increasing number of people are using online services for backup and replication purposes and it is clear that congestion increases exponentially on the network. One of the ways in which the latency problem can be solved is to remove core network congestion or to limit it in such a way that it does not pose a problem. In South Africa, Telkom rolled out MSAN cabinets as part of their Fibre-to-the-curb (FTTC) upgrades. This created an unique opportunity to provide new services, like BaRaaS, by implementing micro data centres within the MSAN to reduce congestion on the core network. It is important to have background knowledge on what exactly latency is and what causes it on a network. It is also essential to have an understanding of how congestion (and thus latency) can be avoided on a network. The background literature covered helps to determine which tools are available to do this, as well as to highlight any possible gaps that exist for new congestion control mechanisms. A simulation study was performed to determine whether implementing micro data centres inside the MSAN will in fact reduce latency. Simulations must be done as realistically as possible to ensure that the results can be correlated to a real-world problem. Two different simulations were performed to model the behaviour of the network when backup and replication data is sent to the Internet and when it is sent to a local MSAN. In both models the core network throughput as well as the Round Trip Times (RTTs) from the client to the Internet and the MSAN cabinets, were recorded. The RTT results were then used to determine whether latency had been reduced. Once it was established that micro data centres will indeed help in reducing congestion and latency on the network, the design of a storage server, for inclusion inside the MSAN cabinet, was done. A cost benefit analysis was also performed to ensure that the project will be financially viable in the long term. The cost analysis took into account all the costs associated with the project and then expanded them over a certain period of time to determine initial expenses. Extra information was then taken into consideration to determine the possible income per year as well as extra expenditure. It was found that the inclusion of a micro data centre reduces latency on the core network due to the removal of large backup data traffic from the core network, which reduces congestion and improves latency. From the Cost Benefit Analysis (CBA) it was found that the BaRaaS service is viable from a subscription point of view. Finally, the relevant conclusions with regard to the effects of data centres in MSAN cabinets on latency and services were drawn.
Vertraagtyd word 'n belangrike faktor in baie Internet toepassings soos P2P-deel en aanlyn-speletjies. Gekoppel met die feit dat 'n toenemende getal mense internetdienste gebruik vir rugsteun en replisering, word opeenhoping in die datanetwerk eksponensieel verhoog. Een van die maniere waarop die vertraagtydsprobleem opgelos kan word, is om opeenhoping in die kern-datanetwerk te verwyder of om dit op so 'n manier te beperk dat dit nie 'n probleem veroorsaak nie. In Suid Afrika het Telkom MSAN-kaste uitgerol as deel van hulle "Fibre-to-the-Curb" (FTTC) opgraderings. Dit het 'n unieke geleentheid geskep om nuwe dienste te skep, soos BaRaaS, deur mikro-datasentrums in die MSAN-kas te implementeer om opeenhoping in die kernnetwerk te verminder. Dit is belangrik om agtergrondkennis te hê van presies wat vertraagtyd is en waardeur dit op die netwerk veroorsaak word. Dit is ook belangrik om 'n begrip te hê van hoe opeenhoping (en dus vertraagtyd) op die netwerk vermy kan word. Die agtergrondsliteratuur wat gedek is help om te bepaal watter instrumente beskikbaar is, asook om moontlikhede na vore te bring vir nuwe meganismes om opeenhoping te beheer. 'n Simulasiestudie is uitgevoer om vas te stel of die insluiting van datasentrums in die MSAN-kaste inderdaad 'n verskil sal maak aan die vertraagtyd in die datanetwerk. Twee simulasies is uitgevoer om die gedrag van die netwerk te modelleer wanneer rugsteun- en repliseringsdata na onderskeidelik die Internet en die plaaslike MSAN gestuur word. In altwee is die deurset van die kernnetwerk sowel as die sogenaamde Round Trip Times (RTTs) van die kliënt na die Internet en die MSAN-kaste aangeteken. Die RTTs-resultate sal gebruik word om te bepaal of vertraagtyd verminder is. Nadat dit bepaal is dat mikro-datasentrums wel die opeenhoping in die netwerk sal verminder, is die ontwerp van 'n stoorbediener gedoen, vir insluiting in die MSAN-kas. 'n Koste-ontleding neem alle koste wat met die projek verband hou in ag en versprei dit dan oor 'n bepaalde tydperk om die aanvanklike kostes te bepaal. Verdere inligting word voorts in ag geneem om die moontlike inkomste per jaar sowel as addisionele uitgawes te bepaal. Daar is bevind dat die insluiting van 'n mikro-datasentrum vertraagtyd verminder deur groot rugsteen-dataverkeer van die kernnetwerk af te verwyder. Die koste-ontleding het gewys dat uit 'n subskripsie-oogpunt, die BaRaaS diens lewensvatbaar is. Uiteindelik word relevante gevoltrekkings gemaak oor die effek van datasentrums in MSAN-kaste op vertraagtyd en dienste.
Dissertation (MEng)--University of Pretoria, 2017.
Electrical, Electronic and Computer Engineering
MEng
Unrestricted

This thesis proposes an approach for the design and implementation of collaborative cache systems in grids that supports capabilities for monitoring and controlling cache interactions. Our approach permits to compose and evaluate high-level collaborative cache functions in a flexible way. Our proposal is based on a multilayer model that defines the main functions of a collaborative grid cache system. This model and the provided specification are used to build a flexible and generic software infrastructure for the operation and control of collaborative caches. This infrastructure is composed of a group of autonomous cache elements called Grid Cache Services (GCS). The GCS is a local administrator of temporary storage and data which is implemented as a grid service that provides the cache capabilities defined by the model. We study a possible configuration for a group of GCS that constitutes a basic management system of temporary data called Temporal Storage Service (TSS)
Cette thèse propose une approche de la conception et de l'implémentation de systèmes de cache collaboratif dans les grilles de données. Notre approche permet la composition et l'évaluation des fonctions d‘un système de cache collaboratif de haut niveau de façon flexible. Notre proposition est basée sur un modèle multicouche qui définit les fonctions principales d'un système de cache collaboratif pour les grilles. Ce modèle et la spécification fournie sont utilisés pour construire une infrastructure logicielle flexible et générique pour l'opération et le contrôle du cache collaboratif. Cette infrastructure est composée d'un groupe d’éléments autonomes de cache appelés "Grid Cache Services" (GCS). Le GCS est un administrateur local de moyens de stockage et de données temporaires. Nous étudions une possible configuration d’un groupe de GCS qui constitue un système basique d'administration de données temporaires appelé "Temporal Storage Service" (TSS)

Le trafic vidéo a subi une augmentation fulgurante sur Internet ces dernières années. Pour pallier à cette importante demande de contenu vidéo, la technologie du streaming adaptatif sur HTTP est utilisée. Elle est devenue par ailleurs très populaire car elle a été adoptée par les différents acteurs du domaine de la vidéo streaming. C’est une technologie moins couteuse qui permet aux fournisseurs de contenu, la réutilisation des serveurs web et des caches déjà déployés. En plus, elle est exempt de tout blocage car elle traverse facilement les pare-feux et les translations d’adresses sur Internet. Dans cette thèse, nous proposons une nouvelle méthode de vidéo streaming adaptatif appelé “Backward-Shifted Coding (BSC)”. Il se veut être une solution complémentaire au standard DASH, le streaming adaptatif et dynamique utilisant le protocole HTTP. Nous allons d’abord décrire ce qu’est la technologie BSC qui se base sur le codec (encodeur décodeur) à multi couches SVC, un algorithme de compression extensible ou évolutif. Nous détaillons aussi l’implémentation de BSC dans un environnement DASH. Ensuite,nous réalisons une évaluation analytique de BSC en utilisant des résultats standards de la théorie des files d’attente. Les résultats de cette analyse mathématique montrent que le protocole BSC permet de réduire considérablement le risque d’interruption de la vidéo pendant la lecture, ce dernier étant très pénalisant pour les utilisateurs. Ces résultats vont nous permettre de concevoir des algorithmes d’adaptation de qualité à la bande passante en vue d’améliorer l’expérience utilisateur. Ces algorithmes permettent d’améliorer la qualité de la vidéo même étant dans un environnement où le débit utilisateur est très instable.La dernière étape de la thèse consiste à la conception de stratégies de caching pour optimiser la transmission de contenu vidéo utilisant le codec SVC. En effet, dans le réseau, des serveurs de cache sont déployés dans le but de rapprocher le contenu vidéo auprès des utilisateurs pour réduire les délais de transmission et améliorer la qualité de la vidéo. Nous utilisons la programmation linéaire pour obtenir la solution optimale de caching afin de le comparer avec nos algorithmes proposés. Nous montrons que ces algorithmes augmentent la performance du système tout en permettant de décharger les liens de transmission du réseau cœur
Due to the growth of video traffic over the Internet in recent years, HTTP AdaptiveStreaming (HAS) solution becomes the most popular streaming technology because ithas been succesfully adopted by the different actors in Internet video ecosystem. Itallows the service providers to use traditional stateless web servers and mobile edgecaches for streaming videos. Further, it allows users to access media content frombehind Firewalls and NATs.In this thesis we focus on the design of a novel video streaming delivery solutioncalled Backward-Shifted Coding (BSC), a complementary solution to Dynamic AdaptiveStreaming over HTTP (DASH), the standard version of HAS. We first describe theBackward-Shifted Coding scheme architecture based on the multi-layer Scalable VideoCoding (SVC). We also discuss the implementation of BSC protocol in DASH environment.Then, we perform the analytical evaluation of the Backward-Sihifted Codingusing results from queueing theory. The analytical results show that BSC considerablydecreases the video playback interruption which is the worst event that users can experienceduring the video session. Therefore, we design bitrate adaptation algorithms inorder to enhance the Quality of Experience (QoE) of the users in DASH/BSC system.The results of the proposed adaptation algorithms show that the flexibility of BSC allowsus to improve both the video quality and the variations of the quality during thestreaming session.Finally, we propose new caching policies to be used with video contents encodedusing SVC. Indeed, in DASH/BSC system, cache servers are deployed to make contentsclosed to the users in order to reduce network latency and improve user-perceived experience.We use Linear Programming to obtain optimal static cache composition tocompare with the results of our proposed algorithms. We show that these algorithmsincrease the system overall hit ratio and offload the backhaul links by decreasing thefetched content from the origin web servers

La généralisation de l’usage de l’Internet, ces dernières années, a été marquée par deux tendances importantes. Nous citerons en premier, l’enthousiasme de plus en plus grand des utilisateurs pour les services médias. Cette tendance est particulièrement accentuée par l’avènement des contenus générés par les utilisateurs qui amènent dans les catalogues des fournisseurs de services un choix illimité de contenus. L’autre tendance est la diversification et l’hétérogénéité en ressources des terminaux et réseaux d’accès. Seule la valeur du service lui-même compte aujourd’hui pour les utilisateurs et non le moyen d’y accéder. Cependant, offrir aux utilisateurs un accès ubiquitaire à de plus en plus de services Internet, impose des exigences très rigoureuses sur l’infrastructure actuelle de l’Internet. En effet, L’évolution de l’Internet devient aujourd’hui une évidence et cette évolution est d’autant plus nécessaire dans un contexte de services multimédias qui sont connus pour leur sensibilité au contexte dans lequel ils sont consommés et pour générer d’énormes quantités de trafic. Dans le cadre de cette thèse, nous nous focalisons sur deux enjeux importants dans l’évolution de l’Internet. A savoir, faciliter le déploiement de services médias personnalisés et adaptatifs et améliorer les plateformes de distribution de ces derniers afin de permettre leur passage à l’échelle tout en gardant la qualité de service à un niveau satisfaisant pour les utilisateurs finaux. Afin de permettre ceci, nous introduisons en premier, une nouvelle architecture multi environnements et multi couches permettant un environnement collaboratif pour le partage et la consommation des services médias dans un cadre des réseaux média du futur. Puis, nous proposons deux contributions majeures que nous déployons sur la couche virtuelle formés par les Home-Boxes (passerelles résidentielles évoluées) introduite dans l’architecture précédente. Dans notre première contribution, nous proposons un environnement permettant le déploiement à grande échelle de services sensibles au contexte. Deux approches ont été considérées dans la modélisation et la gestion du contexte. La première approche est basée sur les langages de balisage afin de permettre un traitement du contexte plus léger et par conséquent des temps de réponse très petits. La seconde approche, quant à elle est basée sur les ontologies et les règles afin de permettre plus d’expressivité et un meilleur partage et réutilisation des informations de contexte. Les ontologies étant connues pour leur complexité, le but de cette proposition et de prouver la faisabilité d’une telle approche dans un contexte de services multimédias par des moyen de distribution de la gestion du contexte. Concernant notre deuxième contribution, l’idée et de tirer profit des ressources (disque et connectivité) des Home-Boxes déjà déployées, afin d’améliorer les plateformes de distribution des services médias et d’améliorer ainsi le passage à l’échelle, la performance et la fiabilité de ces derniers et ce, à moindre coût. Pour cela, nous proposons deux solutions pour deux problèmes communément traités dans la réplication des contenus : (1) la redirection de requêtes pour laquelle nous proposons un algorithme de sélection à deux niveaux de filtrage, un premier filtrage basé sur les règles afin de personnaliser les services en fonction du contexte de leur consommation suivi d’un filtrage basé sur des métriques réseaux (charges des serveurs et délais entre les serveurs et les clients) ; et (2) le placement et la distribution des contenus sur les caches pour lesquels on a proposé une stratégie de mise en cache online, basée sur la popularité des contenus
Users’ willingness to consume media services along with the compelling proliferation of mobile devices interconnected via multiple wired and wireless networking technologies place high requirements on the Future Internet. It is a common belief today that Internet should evolve towards providing end users with ubiquitous and high quality media services and this, in a scalable, reliable, efficient and interoperable way. However, enabling such a seamless media delivery raises a number of challenges. On one hand, services should be more context-aware to enable their delivery to a large and disparate computational context. On another hand, current Internet media delivery infrastructures need to scale in order to meet the continuously growing number of users while keeping quality at a satisfying level. In this context, we introduce a novel architecture, enabling a novel collaborative framework for sharing and consuming Media Services within Future Internet (FI). The introduced architecture comprises a number of environments and layers aiming to improve today’s media delivery networks and systems towards a better user experience. In this thesis, we are particulary interested in enabling context-aware multimedia services provisioning that meets on one hand, the users expectations and needs and on another hand, the exponentially growing users’ demand experienced by these services. Two major and demanding challenges are then faced in this thesis (1) the design of a context-awareness framework that allows adaptive multimedia services provisioning and, (2) the enhancement of the media delivery platform to support large-scale media services. The proposed solutions are built on the newly introduced virtual Home-Box layer in the latter proposed architecture.First, in order to achieve context-awareness, two types of frameworks are proposed based on the two main models for context representation. The markup schemes-based framework aims to achieve light weight context management to ensure performance in term of responsiveness. The second framework uses ontology and rules to model and manage context. The aim is to allow higher formality and better expressiveness and sharing. However, ontology is known to be complex and thus difficult to scale. The aim of our work is then to prove the feasibility of such a solution in the field of multimedia services provisioning when the context management is distributed among the Home-Box layer. Concerning the media services delivery enhancement, the idea is to leverage the participating and already deployed Home-Boxes disk storage and uploading capabilities to achieve service performance, scalability and reliability. Towards this, we have addressed two issues that are commonly induced by the content replication: (1) the server selection for which we have proposed a two-level anycast-based request redirection strategy that consists in a preliminary filtering based on the clients’ contexts and in a second stage provides accurate network distance information, using not only the end-to-end delay metric but also the servers’ load one and, (2) the content placement and replacement in cache for which we have designed an adaptive online popularity-based video caching strategy among the introduced HB overlay

This thesis focuses on the design and implementation of a software system enabling out-of-core rendering of multiple map datasets mapped on virtual globes around our solar system. Challenges such as precision, accuracy, curvature and massive datasets were considered. The result is a globe visualization software using a chunked level of detail approach for rendering. The software can render texture layers of various sorts to aid in scientific visualization on top of height mapped geometry, yielding accurate visualizations rendered at interactive frame rates. The project was conducted at the American Museum of Natural History (AMNH), New York and serves the goal of implementing a planetary visualization software to aid in public presentations and bringing space science to the public. The work is part of the development of the software OpenSpace, which is the result of a collaboration between Linköping University, AMNH and the National Aeronautics and Space Administration (NASA) among others.

This project was done for a company called Anchr that develops a location based mobile application for listing nearby hangouts in a specified area. For this, they integrate a number of services which they send requests to in order to see if there are any nearby locations listed for these services. One of these services is Meetup, which is an application where users can create social events and gatherings. The problem this project aims to solve is that a large number of requests are sent to Meetup’s service in order to get information about the events, so that they then can be displayed in the application. This is a problem since only a limited number of requests can be sent within a specified time period before the service is locked. This means that Meetup’s service cannot be integrated into the application as it is now implemented, as the feature will become useless if no requests can be sent. The purpose of this project is therefore to find an alternative way of collecting the events from the service without it locking. This would enable the service to be integrated into the application. The hypothesis is that instead of using the current method of sending requests to get events, implement a listener that listens for incoming events from Meetup’s stream, to directly get updates whenever an event is created or updated. The result of the project is that there now exists a system which listens for events instead of repeatedly sending requests. The issue with the locking of the service does not exist anymore since no requests are sent to Meetup’s service.
Detta projekt genomfördes för ett företag som heter Anchr som utvecklar en platsbaserad mobilapplikation för att lista närliggande sociala platser inom ett specificerat område. För detta integrerade de ett antal tjänster som de skickar förfrågningar till för att se om det finns några närliggande platser listade för dessa tjänster. En av dessa tjänster är Meetup som är en applikation där användare kan skapa sociala evenemang. Problemet detta examensarbete syftar till att lösa är att ett stort antal förfrågningar skickas till Meetups tjänst för att få information om evenemangen så att de kan visas i applikationen. Detta är ett problem då endast ett begränsat antal förfrågningar kan skickas till deras tjänst inom ett visst tidsintervall innan tjänsten spärras. Detta betyder att Meetups tjänst inte kan integreras in i applikationen såsom den är implementerad i nuläget, eftersom funktionen kommer bli oanvändbar om inga förfrågningar kan skickas. Syftet med detta projekt är därför att hitta ett alternativt sätt att samla in evenemang från tjänsten utan att den spärras. Detta skulle göra så tjänsten kan integreras in i applikationen. Hypotesen är att istället för att använda den nuvarande metoden som går ut på att skicka förfrågningar för att få nya händelser, implementera en lyssnare som lyssnar efter inkommande händelser från Meetups stream, för att direkt få uppdateringar när ett evenemang skapas eller uppdateras. Resultatet av detta är att det nu finns ett system som lyssnar efter evenemang istället för att upprepningsvis skicka förfrågningar. Problemet med låsningen av tjänsten existerar inte längre då inga förfrågningar skickas till Meetup’s tjänst.

With the rise of data exchange over the Internet, information-centric networks have become a popular research topic in computing. One major research topic on Information Centric Networks (ICN) is the use of data caching to increase network performance. However, research in the security concerns of data caching networks is lacking. One example of a data caching network can be seen using a Mobile Ad Hoc Network (MANET). Recently, a study has shown that it is possible to infer military activity through cache behavior which is used as a basis for a formulated denial of service attack (DoS) that can be used to attack networks using data caching. Current security issues with data caching networks are discussed, including possible prevention techniques and methods. A targeted data cache DoS attack is developed and tested using an ICN as a simulator. The goal of the attacker would be to fill node caches with unpopular content, thus making the cache useless. The attack would consist of a malicious node that requests unpopular content in intervals of time where the content would have been just purged from the existing cache. The goal of the attack would be to corrupt as many nodes as possible without increasing the chance of detection. The decreased network throughput and increased delay would also lead to higher power consumption on the mobile nodes, thus increasing the effects of the DoS attack. Various caching polices are evaluated in an ICN simulator program designed to show network performance using three common caching policies and various cache sizes. The ICN simulator is developed using Java and tested on a simulated network. Baseline data are collected and then compared to data collected after the attack. Other possible security concerns with data caching networks are also discussed, including possible smarter attack techniques and methods.

O custo de serviços na Internet tem encorajado o uso de cache a nível de aplicação para suprir as demandas dos usuários e melhorar a escalabilidade e disponibilidade de aplicações. Cache a nível de aplicação, onde desenvolvedores manualmente controlam o conteúdo cacheado, tem sido adotada quando soluções tradicionais de cache não são capazes de atender aos requisitos de desempenho desejados. Apesar de sua crescente popularidade, este tipo de cache é tipicamente endereçado de maneira ad-hoc, uma vez que depende de detalhes específicos da aplicação para ser desenvolvida. Dessa forma, tal cache consiste em uma tarefa que requer tempo e esforço, além de ser altamente suscetível a erros. Esta dissertação avança o trabalho relacionado a cache a nível de aplicação provendo uma compreensão de seu estado de prática e automatizando a identificação de conteúdo cacheável, fornecendo assim suporte substancial aos desenvolvedores para o projeto, implementação e manutenção de soluções de caching. Mais especificamente, este trabalho apresenta três contribuições: a estruturação de conhecimento sobre caching derivado de um estudo qualitativo, um levantamento do estado da arte em abordagens de cache estáticas e adaptativas, e uma técnica que automatiza a difícil tarefa de identificar oportunidades de cache O estudo qualitativo, que envolveu a investigação de dez aplicações web (código aberto e comercial) com características diferentes, permitiu-nos determinar o estado de prática de cache a nível de aplicação, juntamente com orientações práticas aos desenvolvedores na forma de padrões e diretrizes. Com base nesses padrões e diretrizes derivados, também propomos uma abordagem para automatizar a identificação de métodos cacheáveis, que é geralmente realizado manualmente por desenvolvedores. Tal abordagem foi implementada como um framework, que pode ser integrado em aplicações web para identificar automaticamente oportunidades de cache em tempo de execução, com base na monitoração da execução do sistema e gerenciamento adaptativo das decisões de cache. Nós avaliamos a abordagem empiricamente com três aplicações web de código aberto, e os resultados indicam que a abordagem é capaz de identificar oportunidades de cache adequadas, melhorando o desempenho das aplicações em até 12,16%.
Latency and cost of Internet-based services are encouraging the use of application-level caching to continue satisfying users’ demands, and improve the scalability and availability of origin servers. Application-level caching, in which developers manually control cached content, has been adopted when traditional forms of caching are insufficient to meet such requirements. Despite its popularity, this level of caching is typically addressed in an adhoc way, given that it depends on specific details of the application. Furthermore, it forces application developers to reason about a crosscutting concern, which is unrelated to the application business logic. As a result, application-level caching is a time-consuming and error-prone task, becoming a common source of bugs. This dissertation advances work on application-level caching by providing an understanding of its state-of-practice and automating the decision regarding cacheable content, thus providing developers with substantial support to design, implement and maintain application-level caching solutions. More specifically, we provide three key contributions: structured knowledge derived from a qualitative study, a survey of the state-of-the-art on static and adaptive caching approaches, and a technique and framework that automate the challenging task of identifying cache opportunities The qualitative study, which involved the investigation of ten web applications (open-source and commercial) with different characteristics, allowed us to determine the state-of-practice of application-level caching, along with practical guidance to developers as patterns and guidelines to be followed. Based on such patterns and guidelines derived, we also propose an approach to automate the identification of cacheable methods, which is often manually done and is not supported by existing approaches to implement application-level caching. We implemented a caching framework that can be seamlessly integrated into web applications to automatically identify and cache opportunities at runtime, by monitoring system execution and adaptively managing caching decisions. We evaluated our approach empirically with three open-source web applications, and results indicate that we can identify adequate caching opportunities by improving application throughput up to 12.16%. Furthermore, our approach can prevent code tangling and raise the abstraction level of caching.

Thesis (Ph. D.) -- University of Maryland, College Park, 2006.
Thesis research directed by: Electrical Engineering. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Today's Internet usage is changing from host-to-host communication to user-to-content interaction which proves a challenge for Internet Service Providers (ISPs). Repeated requests lead to transfers of large amounts of traffic containing the same content often over costly inter-ISP connections. Content Distribution Networks (CDNs) contribute to solving this issue, but do not directly address the problem. This thesis project explores how content based addressing could minimize inter-ISP traffic due to repeated requests for content by caching content within the ISP's network. We implemented CCNx 0.6.0 in a network testbed in order to simulate scenarios with multiple ISPs interconnected to each other. This testbed is used to illustrate how caching of popular content minimizes inter-ISP traffic as well as how content independence minimizes the effect of other network problems such as link failures and congestion. These tests shows that the large overhead of the CCNx implementation due to the additional headers brings a 16% performance reduction compared to Hypertext Transfer Protocol (HTTP) transfers. However, these tests also shows that the cost from the inter-ISP traffic of CCNx transfers are constant regardless of the number of repeated requests, due to content caching in the ISP's network. As soon as there is more than one request for the same content there is a gain in using CCNx rather than HTTP for content transfer.
Dagens användning av internet ändrar form från dator-till-dator kommunikation till användaretill- innehålls interaktion vilket innebär nya utmaningar för internetleverantörer vilka måste överföra stora mängder upprepade förfrågningar av innehåll via kostsamma länkar mellan internetleverantörer. Lösningar som innehållsdistribuerande nätverk (Content Distribution Network) hjälper idag till men addresserar inte kärnan av problemet. Det här examensarbetet undersöker hur innehållsbaserad addressering kan minimera mängden trafik mellan internetleverantörer genom att cachning, att lagra kopior av innehåll, i internetleverantörers nätverket. I det här examensarbetet implementerade vi CCNx 0.6.0 i en testbädd för att simulera scenarion med nätverk mellan internetleverantörer. Denna testbädd används för att illustrera hur cachning av populärt innehåll kan minimera trafik mellan internetleverantörer samt hur innehållets oberoende av plats även hjälper till med andra problem i nätverket såsom länkfel och stockning. Dessa test visar att CCNx implementationen har stor overhead information på grund av ytterligare, extra headers vilket medför en 16% reducering i prestanda jämfört med överföringar som använder Hypertext Transfer Protocol (HTTP). Vidare visar dessa tester även att kostnaden från trafik mellan internetleverantörer är konstant oberoende av antalet upprepade förfrågningar, på grund av cachning av innehåll i internetleverantörens nätverk. Så snart det finns fler än en begäran för samma innehåll finns det en vinst i att använda CCNx istället för HTTP för överföringar av innehåll.

Il modello di lavoro noto come Multi Cloud sta emergendo come una naturale evoluzione del Cloud Computing per rispondere alle nuove esigenze di business delle aziende. Un tipico esempio è il modello noto come Cloud Ibrido dove si ha un Cloud Privato connesso ad un Cloud Pubblico per consentire alle applicazioni di scalare al bisogno e contemporaneamente rispondere ai bisogni di privacy, costi e sicurezza. Data la distribuzione dei dati su diverse strutture, quando delle applicazioni in esecuzione su un centro di calcolo devono utilizzare dati memorizzati remotamente, diventa necessario accedere alla rete che connette le diverse infrastrutture. Questo ha grossi impatti negativi su carichi di lavoro che consumano dati in modo intensivo e che di conseguenza vengono influenzati da ritardi dovuti alla bassa banda e latenza tipici delle connessioni di rete. Applicazioni di Intelligenza Artificiale e Calcolo Scientifico sono esempi di questo tipo di carichi di lavoro che, grazie all’uso sempre maggiore di acceleratori come GPU e FPGA, diventano capaci di consumare dati ad una velocità maggiore di quella con cui diventano disponibili. Implementare un livello di cache che fornisce e memorizza i dati di calcolo dal dispositivo di memorizzazione lento (remoto) a quello più veloce (ma costoso) dove i calcoli sono eseguiti, sembra essere la migliore soluzione per trovare il compromesso ottimale tra il costo dei dispositivi di memorizzazione offerti come servizi Cloud e la grande velocità di calcolo delle moderne applicazioni. Il sistema cache presentato in questo lavoro è stato sviluppato tenendo conto di tutte le peculiarità dei servizi di memorizzazione Cloud che fanno uso di API S3 per comunicare con i clienti. La soluzione proposta è stata ottenuta lavorando con il sistema di memorizzazione distribuito Ceph che implementa molti dei servizi caratterizzanti la semantica S3 ed inoltre, essendo pensato per lavorare su ambienti Cloud si inserisce bene in scenari Multi Cloud.

With Vehicular mobile communication becoming a daily requirement and an ever increasing number of services being available to passengers, it is clear that vehicular networks efficient communication systems. VANETs, one of the most significant trends in ad-hoc networking, has much to gain from improved content delivery and one of the leading contenders for mobile networks is the Information-Centric networking approach. Its peculiarities define the Vehicular Environment requires specialized solutions, tailored for highly mobile environments. The main contribution of this thesis is the introduction of a novel architecture and components. We perform extensively discuss Information-Centric Vehicular Ad-hoc Networks. Additionally, we perform an in-depth analysis of bus-based transit systems into VANETs not only as participating members but as service providers and official agents including roles and potential challenges. We perform statistical analysis and analyze world data to denote the intrinsic potential of public transit systems. From the discussions presented, we introduce a novel service-based system architecture for Information-Centric Networking named SEVeN. The proposed model is designed to enable service exchange and service management in highly competitive vehicular ad-hoc networks. The proposed SEVeN architecture includes the introduction of a novel purpose-defined naming policy and service sub-layer as well as a service prioritization policy named LBD. We also discuss the current state of ICN caching in VANET, existing issues faced by vehicular networks and potential approaches based on intermediate cache coordination that can be taken to mitigate existing shortcommings. We perform a series of simulations and analyze the efficiency of popular caching in various network configurations to denote current shortcomings. From this discussion, we propose a cache content insertion policies, UG-Cache and MG-Cache, for ICN-VANETs. In these cache policies, cache insertion decisions are made based on recommendations from content sender dependent on request frequency and cache distance. We also introduce a caching policy based on collaborative observation of locality in request frequency, designed to allow vehicles to preemptively distribute and store in a reserved portion of the cache based on the cooperative observation of requests with provider-based location correlation. All novel elements proposed by this thesis are discussed, described, evaluated within the chapters of this thesis.

Cloud Computing represents a recent paradigm shift that enables users to share and remotely access high-powered computing resources (both infrastructure and software/services) contained in off-site data centers thereby allowing a more efficient use of hardware and software infrastructures. This growing trend in cloud computing, combined with the demands for Big Data and Big Data analytics, is driving the rapid evolution of datacenter technologies towards more cost-effective, consumer-driven, more privacy conscious and technology agnostic solutions. This dissertation is dedicated to taking a systematic approach to develop system-level techniques and algorithms to tackle the challenges of large-scale data processing in the Cloud and scaling and delivering privacy-aware services with anytime-anywhere availability. We analyze the key challenges in effective provisioning of Cloud services in the context of MapReduce-based parallel data processing considering the concerns of cost-effectiveness, performance guarantees and user-privacy and we develop a suite of solution techniques, architectures and models to support cost-optimized and privacy-preserving service provisioning in the Cloud. At the cloud resource provisioning tier, we develop a utility-driven MapReduce Cloud resource planning and management system called Cura for cost-optimally allocating resources to jobs. While existing services require users to select a number of complex cluster and job parameters and use those potentially sub-optimal per-job configurations, the Cura resource management achieves global resource optimization in the cloud by minimizing cost and maximizing resource utilization. We also address the challenges of resource management and job scheduling for large-scale parallel data processing in the Cloud in the presence of networking and storage bottlenecks commonly experienced in Cloud data centers. We develop Purlieus, a self-configurable locality-based data and virtual machine management framework that enables MapReduce jobs to access their data either locally or from close-by nodes including all input, output and intermediate data achieving significant improvements in job response time. We then extend our cloud resource management framework to support privacy-preserving data access and efficient privacy-conscious query processing. Concretely, we propose and implement VNCache: an efficient solution for MapReduce analysis of cloud-archived log data for privacy-conscious enterprises. Through a seamless data streaming and prefetching model in VNCache, Hadoop jobs begin execution as soon as they are launched without requiring any apriori downloading. At the cloud consumer tier, we develop mix-zone based techniques for delivering anonymous cloud services to mobile users on the move through Mobimix, a novel road-network mix-zone based framework that enables real time, location based service delivery without disclosing content or location privacy of the consumers.

L'objectif de cette thèse est de fournir des algorithmes d'optimisation pour l'accès aux services vidéo qu’ils soient non-gérés (Internet TV) ou gérés (IPTV). Nous étudions des statistiques récentes concernant les services vidéo non-gérés comme YouTube et nous proposons des techniques d'optimisation appropriées qui pourraient améliorer l'accès aux fichiers vidéos et réduire le coût de cet accès. En outre, l’analyse des coûts joue un rôle important dans les décisions qui concernent la mise en cache des fichiers vidéos et celles liées au choix des périodes temporelles d'hébergement de ces fichiers sur les serveurs. En ce qui concerne les services vidéo gérés appelés IPTV, nous avons mené des expériences sur une architecture ouverte IPTV-collaboration entre différents opérateurs. Ce modèle est analysé selon un critère de coût d’investissement et d'exploitation à l'intérieur de la sphère domestique. En outre, nous avons introduit une solution d’optimisation dynamique de l'arbre « minimum spanning tree » (MST) pour le service IPTV multicast. Lors d’un accès nomade, les arbres statiques pourraient être incapables de fournir le service de manière efficace vu que l'utilisation de la bande passante augmente aux côté des points de streaming (racines de la topologie). Finalement, nous étudions des mesures de sécurité fiables en streaming vidéo basées sur la méthodologie de la chaîne de hachage et nous proposons un nouvel algorithme hybride. Nous effectuons des comparaisons entre les différentes manières utilisées dans la réalisation de la fiabilité des chaînes de hachage basées sur les classifications génériques
The aim of this thesis is to provide optimization algorithms for accessing video services either in unmanaged or managed ways. We study recent statistics about unmanaged video services like YouTube and propose suitable optimization techniques that could enhance files accessing and reduce their access costs. Moreover, this cost analysis plays an important role in decision making about video files caching and hosting periods on the servers. Under managed video services called IPTV, we conducted experiments for an open-IPTV collaborative architecture between different operators. This model is analyzed in terms of CAPEX and OPEX costs inside the domestic sphere. Moreover, we introduced a dynamic way for optimizing the Minimum Spanning Tree (MST) for multicast IPTV service. In nomadic access, the static trees could be unable to provide the service in an efficient manner as the utilization of bandwidth increases towards the streaming points (roots of topologies). Finally, we study reliable security measures in video streaming based on hash chain methodology and propose a new algorithm. Then, we conduct comparisons between different ways used in achieving reliability of hash chains based on generic classifications

The aim of this thesis is to provide optimization algorithms for accessing video services either in unmanaged or managed ways. We study recent statistics about unmanaged video services like YouTube and propose suitable optimization techniques that could enhance files accessing and reduce their access costs. Moreover, this cost analysis plays an important role in decision making about video files caching and hosting periods on the servers. Under managed video services called IPTV, we conducted experiments for an open-IPTV collaborative architecture between different operators. This model is analyzed in terms of CAPEX and OPEX costs inside the domestic sphere. Moreover, we introduced a dynamic way for optimizing the Minimum Spanning Tree (MST) for multicast IPTV service. In nomadic access, the static trees could be unable to provide the service in an efficient manner as the utilization of bandwidth increases towards the streaming points (roots of topologies). Finally, we study reliable security measures in video streaming based on hash chain methodology and propose a new algorithm. Then, we conduct comparisons between different ways used in achieving reliability of hash chains based on generic classifications

Esta tesis se ha creado en el marco de la línea de investigación de Mecanismos de Distribución de Contenidos en Redes IP, que ha desarrollado su actividad en diferentes proyectos de investigación y en la asignatura ¿Mecanismos de Distribución de Contenidos en Redes IP¿ del programa de doctorado ¿Telecomunicaciones¿ impartido por el Departamento de Comunicaciones de la UPV y, actualmente en el Máster Universitario en Tecnologías, Sistemas y Redes de Comunicación. El crecimiento de Internet es ampliamente conocido, tanto en número de clientes como en tráfico generado. Esto permite acercar a los clientes una interfaz multimedia, donde pueden concurrir datos, voz, video, música, etc. Si bien esto representa una oportunidad de negocio desde múltiples dimensiones, se debe abordar seriamente el aspecto de la escalabilidad, que pretende que el rendimiento medio de un sistema no se vea afectado conforme aumenta el número de clientes o el volumen de información solicitada. El estudio y análisis de la distribución de contenido web y streaming empleando CDNs es el objeto de este proyecto. El enfoque se hará desde una perspectiva generalista, ignorando soluciones de capa de red como IP multicast, así como la reserva de recursos, al no estar disponibles de forma nativa en la infraestructura de Internet. Esto conduce a la introducción de la capa de aplicación como marco coordinador en la distribución de contenido. Entre estas redes, también denominadas overlay networks, se ha escogido el empleo de una Red de Distribución de Contenido (CDN, Content Delivery Network). Este tipo de redes de nivel de aplicación son altamente escalables y permiten un control total sobre los recursos y funcionalidad de todos los elementos de su arquitectura. Esto permite evaluar las prestaciones de una CDN que distribuya contenidos multimedia en términos de: ancho de banda necesario, tiempo de respuesta obtenido por los clientes, calidad percibida, mecanismos de distribución, tiempo de vida al utilizar caching, etc. Las CDNs nacieron a finales de la década de los noventa y tenían como objetivo principal la eliminación o atenuación del denominado efecto flash-crowd, originado por una afluencia masiva de clientes. Actualmente, este tipo de redes está orientando la mayor parte de sus esfuerzos a la capacidad de ofrecer streaming media sobre Internet. Para un análisis minucioso, esta tesis propone un modelo inicial de CDN simplificado, tanto a nivel teórico como práctico. En el aspecto teórico se expone un modelo matemático que permite evaluar analíticamente una CDN. Este modelo introduce una complejidad considerable conforme se introducen nuevas funcionalidades, por lo que se plantea y desarrolla un modelo de simulación que permite por un lado, comprobar la validez del entorno matemático y, por otro lado, establecer un marco comparativo para la implementación práctica de la CDN, tarea que se realiza en la fase final de la tesis. De esta forma, los resultados obtenidos abarcan el ámbito de la teoría, la simulación y la práctica.
Molina Moreno, B. (2013). Estudio, análisis y desarrollo de una red de distribución de contenido y su algoritmo de redirección de usuarios para servicios web y streaming [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/31637
TESIS

Progressive Web Apps (PWA) is a concept of enhanced web apps which aim to erase the difference between web and native apps. The concept of PWA introduces several benefits, including simpler distribution and development, which makes web apps a viable option for many businesses. The installation process of a PWA is different from native apps and this study aims to understand whether or not it has an impact on the users will to install the PWA. PWA:s are installed directly from the browser, rather than an app marketplace. Said installation process is suspected to be unknown to many which might influence the impact. In this study, several papers on the topic are studied. A PWA is developed from scratch which is used as a platform for a user test, hosting a brief introduction of the topic as well as guiding participants through the installation process. In conjunction with the user test a survey is conducted to collect the impressions from their experience in the user test. The result of the survey shows indications that the suspected lack of knowledge and experience was correct, and that the installation process is not to complicated.Additionally, results show that many probably will not bother to install a PWA, even if it is available. Therefore, I argue that the installation process does have an impact in its current form. Alternatives to the installation process used in this study do exist and are discussed in this paper.

碩士
輔仁大學
資訊工程學系
91
Due to the rapid growth of mobile communication, more and more wireless mobile applications are developed. Location-based services become a popular trend. However, problems are still to be solved. How to integrate the services of multiple telecommunication service providers? How to provide the location-based services to mobile roaming users? This thesis is aiming at solving these two problems. First part of this thesis proposes to integrate the service roaming into web services infrastructure. Mobile users could get location-based service during roaming. The mobile wireless network has evolved into the Internet infrastructure. Web services become the communication technology of future distributed software. With the XML and SOAP based software development, interoperability became possible. Integrate the location-based application into the web services will make the service roaming available with standardized interfaces. The number of services is expected to be increased significantly after services roaming integration. The second part of this thesis focuses on improving mobile roaming performance with caching. The location-based service caching is different from traditional web caching. Location-based service caching is related to both spatial and timing information. We investigate this problem based on the operation model of application proxy server. Through the experimental analysis, our proposed scheme achieves the LBS roam with tolerable overhead. The increased response time is less than 15ms. On the other hand, the roaming with service cache could improve the response time by 50%.

碩士
國立中正大學
資訊工程研究所
101
Owing to the variety of ways to reach the Internet and changes in user behavior on the Internet, the explosive growth of network traffic appeared. In video streaming environment, it is an important issue to reduce network traffic and upgrade quality of user experience. In this paper, we focus on caching algorithms for upgrading quality of user experience by deploying proxy caches of multimedia objects on the Internet. Based on interval caching, we propose a new caching algorithm named Popularity-Weighted Block-Level Interval Caching (PWBIC). For improving continuity of cached blocks, PWBIC caches intervals and the Extra Blocks which precede them. In order to reduce the probability of caching intervals which occur in unpopular objects, PWBIC weights intervals by using the popularity of objects. Because the beginning portion of objects should be given preferential treatment, PWBIC caches virtual intervals which contain the beginning portion of objects. A simulation is conducted to evaluate PWBIC and compare PWBIC with the original interval caching and its variations. The results show that PWBIC has higher byte-hit ratio and decreased the number of fetched blocks from content server or disk. Also, PWBIC achieves prefix caching.

碩士
國立交通大學
資訊管理研究所
92
In the digital age, technology is evolving rapidly. After the invention of the Internet, Web services technology is seen as the next paradigm which will change the way business integrates. Traditionally, business process integration between companies requires reaching a consensus in platform and protocol in order to communicate with other companies. This leads to a high expenditure in process integration for all companies involved. Furthermore, the changes in functionality in the system may require all participating companies to change the module or system since it is tightly coupled. The introduction of Web services is the new paradigm shift for the software industry as it supports cross platform communications to achieve services retrieval and integration. Many researches have focused on the communication in Web service composition. This thesis investigates the operational performance of service platforms for Web services composition to shorten operational time. As a result, it provides a selective method to reduce the operational time for service platforms.

博士
國立中山大學
資訊工程學系研究所
98
For more than a decade, streaming media services, including on-line conferences, distance education and movie broadcasting, have gained much popularity on the Internet. Due to the high bandwidth requirements and long lived nature of video streaming, it requires huge transmission cost to support these streaming media services. In addition, how to adapt rich multimedia content to satisfy various resource-constrained devices presents a challenge. The limited and time-varying network bandwidth complicates the content adaptation tasks. Differentiated content delivery may be required to meet diverse client profiles and user preferences. Therefore, in order to reduce transmission cost to serve heterogeneous clients for efficient streaming, in this dissertation, several novel schemes including transcoding-enable proxy caching scheme, reactive transmission schemes, and network coding P2P content distribution scheme, are proposed to support efficient multiple-version and layered video delivery in the proxy-attached network environment as well as to provide efficient interactive IPTV service in a peer-to-peer network. Firstly, for multiple-version cache consideration in the transcoding-enable proxy, we focus on reducing the required server bandwidth and startup delay by caching the optimal versions of the video. A generalized video object profit function is derived from the extended weighted transcoding graph to calculate the individual cache profit of certain version of a video object, and the aggregate profit from caching multiple versions of the same video object. This proposed function takes into account the popularity of certain version of a video object, the transcoding delay among versions and the average access duration of each version. Based on the profit function, cache replacement algorithms are proposed to reduce the startup delay and network traffic by efficiently caching video objects with maximum profits. Next, a set of proxy-assisted transmission schemes are proposed to reduce the transmission cost for layered video streaming by integrating the proxy caching with reactive transmission schemes, peer-to-peer mesh networks and multicast capability. These proposed transmission schemes make multiple requests to be serviced by the single transmission and thus to significantly reduce the total required transmission cost. The optimal proxy prefix cache allocation is also calculated for each transmission scheme to identify the cache layers and cache length of each video to minimize the aggregate transmission cost. The process considers the fact that reduction in transmission cost by caching X layers of a video is not only from requests on X layers, but also from requests on less than X layers. Finally, we proposed a network coding equivalent content distribution (NCECD) scheme to decrease server stress, startup delay and jumping latency to support random access operations which are desirable for peer-to-peer on-demand video streaming. The random access operations are difficult to be efficiently supported, due to the asynchronous interactive behaviors of users and the dynamic nature of peers. In NCECD, videos are divided into segments which are then further divided into blocks. These blocks are then encoded into independent encoded blocks that are distributed to the local storage of different peers. With NCECD, a new client only needs to connect to a sufficient number of parent peers in order to view the whole video and rarely needs to find new parents when performing random access operations. Whereas most existing methods must search for parent peers containing interested segments, NCECD uses the properties of network coding to cache equivalent content on most peers, so that searches are rarely needed. The analysis of system parameters is given to achieve reasonable block loss rates for peer-to-peer interactive video-on-demand streaming. Experimental results demonstrate that these proposed schemes can lead to significant transmission cost saving, high delay saving ratio, high bandwidth saving ratio, low startup and jumping searching delays, connecting to a new parent peer delay and less server resources. Hence, these proposed schemes can further be integrated and utilized to build an efficient video streaming platform for providing high-performance and high-quality IPTV services to a diversity of clients.

碩士
國立臺灣海洋大學
資訊工程學系
104
The mobile application (i.e. mobile app or app) is becoming an important software delivery model which integrates front-end user interfaces (UIs) with back-end services in the cloud. Currently, millions of mobile apps are available, including those dealing with entertainment, news, travel, and social networking. However, apps may behave unstably since users may use mobile apps in a variety of wireless network conditions. Meanwhile, developers are hard to mix exiting apps to create a new one and users are not able to customize an app based on their preferences. Therefore, in this paper, we propose a component architecture, called MASA (mobile application slice architecture). MASA offers four main features: 1) being based on mobile web techniques to allow apps to be used cross platform; 2) providing a programming model for building UI page MASs to composite MASs to an application; 3) furnishing a proposed “channel” mechanism with associated APIs to facilitate the data exchange among MASs; and 4) supplying a relational and context-aware web service caching and prefetching mechanism with associate APIs to allow uninterrupted and even offline access to web services. Meanwhile, we also developed a web-based software tool, called MASA portal, to assist users in the construction, discovery, and delivery of composite MAS. Experiment results demonstrate that the proposed MASA approach is able to achieve good scalability when combining a large number of MASs and shorten service response times under a variety of network conditions. Keywords: mobile application, software component, RESTful service, context awareness, service cache, service prefetch, broadcast

Mobile edge computing (MEC) can dramatically promote the compu- tation capability and prolong the lifetime of mobile users by offloading computation- intensive tasks to edge cloud. In this thesis, a spatial-random two-tier heterogeneous network (HetNet) is modelled to feature random node distribution, where the small- cell base stations (SBSs) and the macro base stations (MBSs) are cascaded with resource-limited servers and resource-unlimited servers, respectively. Only a certain type of application services and finite number of offloaded tasks can be cached and processed in the resource-limited edge server. For that setup, we investigate the per- formance of two offloading strategies corresponding to integrated access and backhaul (IAB)-enabled MEC networks and traditional cellular MEC networks. By using tools from stochastic geometry and queuing theory, we derive the average delay for the two different strategies, in order to better understand the influence of IAB on MEC networks. Simulations results are provided to verify the derived expressions and to reveal various system-level insights.

碩士
國立中正大學
通訊工程研究所
93
Streaming media over the Internet brings a huge amount of network traffic which makes the Internet suffering from network congestion. The characteristics of multimedia objects such as huge size, requirement of high bandwidth and the effect of interaction imply that web proxy is not appropriate for caching multimedia streaming object. With the segmentation of multimedia object, we can easily cache the prefix of multimedia object to absorb startup latency or calculate a cache value for each segment for making replace decision accurately. In general, there are two segmentation methods：fix-sized segmentation(FSS) and variable-sized segmentation(VSS). In FSS, when the cache space is not enough to store a new arrival media segments, the replacement policy will select a victim which has the least cache value and evict the last segment of victim for a new segment. However, these causes too many replacement times while evict a big chunk of data. We proposed a caching replacement policy that can be applied to the FSS-based multimedia proxy. The Narrowest Access Gap first replacement policy(NAG) evicts appropriate segments according to the history access records to reduce the overhead caused by FSS. Finally, simulations are performed to evaluate Least-Recently-Used, VSS and NAG replacement policy performance. Simulation results indicate that our policy can achieve higher Byte-hit ratio than others.

碩士
國立屏東科技大學
資訊管理系
92
Continuous progress in the technologies of wireless communications (ex: GSM, GPRS, PHS and 3G) and satellite position (ex: GPS), mobile device’s support are more widespread. We can use handheld device to get we need’s information via wireless communications. One of the promising emerging applications is the location-aware mobile information service. A user gets his/her present location through a global positioning system (GPS) and feeds it to the backend information server via GPRS or CDMA. Server uses that location information to search the information around that area and deliver it to the user. However, multimedia information (ex: Sound and Movie) use pervasive, wide area network’s bandwidth and quality at this time still can not satisfied with a large number of users connection’s request at the same time. Therefore, in this thesis, we propose a Collaborative Micro Caching Mechanism (CC) for the mobile entity who uses MANET to share files by myself without request the same data with server. The basic principle: users in the same area can use MANET to connect and share files by myself with each other. When user still need other data then enables to start to download data with database. This can increase chance to share information and reduce the wide area network’s traffic. We discuss with related work and suggest some solution, and development a simple system at the time. The experiments results confirm that the CC Mechanism can effectively avoid the information exceeding waiting time, and information’s transmission quantity also can to be promoted. Hence, it helps the information availability of location-aware mobile information service.

Copyright law is a special category of civil law which, with the upswing of the Internet, has become important for different types of stakeholders in the global information society. The 'participative web' operates with content generated by users. This user-generated content has often disputable origins in terms of copyright clearance. The Internet has opened the possibility for developing new forms of communication between anonymous or individual users who are not easily identifiable. Especially peer-to-peer file sharing and recently the information services offered and operated by the so-called 'cyberlockers' are the reason of questioning the role of copyright protection online which needs a beneficial solution. Copyright infringement in the era of information society is a complex phenomenon with a multiplicity of contributing factors like the importance of information data with big business potential, personal attitudes shown by internet users towards the value and scarcity of intellectual property, or legal responsibility of internet service providers (ISP) who paradoxically act from the safety of the so-called safe harbours as intermediaries of information exchange, representing a new element in the communication chain between rights holders and users. Commercial and business models operating...