Ontwerp en evaluatie van content distributie netwerken voor multimediale streaming diensten.

Traditionele Internetgebaseerde diensten voor het verspreiden van bestanden, zoals Web browsen en het versturen van e-mails, worden aangeboden via één centrale server. Meer recente netwerkdiensten zoals interactieve digitale televisie of video-op-aanvraag vereisen echter hoge kwaliteitsgaranties (QoS), zoals een lage en constante netwerkvertraging, en verbruiken een aanzienlijke hoeveelheid bandbreedte op het netwerk. Architecturen met één centrale server kunnen deze garanties moeilijk bieden en voldoen daarom niet meer aan de hoge eisen van de volgende generatie multimediatoepassingen. In dit onderzoek worden daarom nieuwe netwerkarchitecturen bestudeerd, die een dergelijke dienstkwaliteit kunnen ondersteunen. Zowel peer-to-peer mechanismes, zoals bij het uitwisselen van muziekbestanden tussen eindgebruikers, als servergebaseerde oplossingen, zoals gedistribueerde caches en content distributie netwerken (CDN's), komen aan bod. Afhankelijk van de bestudeerde dienst en de gebruikte netwerktechnologieën en -architectuur, worden gecentraliseerde algoritmen voor netwerkontwerp voorgesteld. Deze algoritmen optimaliseren de plaatsing van de servers of netwerkcaches en bepalen de nodige capaciteit van de servers en netwerklinks. De dynamische plaatsing van de aangeboden bestanden in de verschillende netwerkelementen wordt aangepast aan de heersende staat van het netwerk en aan de variërende aanvraagpatronen van de eindgebruikers. Serverselectie, herroutering van aanvragen en het verspreiden van de belasting over het hele netwerk komen hierbij ook aan bod

Provider-Controlled Bandwidth Management for HTTP-based Video Delivery

Over the past few years, a revolution in video delivery technology has taken place as mobile viewers and over-the-top (OTT) distribution paradigms have significantly changed the landscape of video delivery services. For decades, high quality video was only available in the home via linear television or physical media. Though Web-based services brought video to desktop and laptop computers, the dominance of proprietary delivery protocols and codecs inhibited research efforts. The recent emergence of HTTP adaptive streaming protocols has prompted a re-evaluation of legacy video delivery paradigms and introduced new questions as to the scalability and manageability of OTT video delivery. This dissertation addresses the question of how to enable for content and network service providers the ability to monitor and manage large numbers of HTTP adaptive streaming clients in an OTT environment. Our early work focused on demonstrating the viability of server-side pacing schemes to produce an HTTP-based streaming server. We also investigated the ability of client-side pacing schemes to work with both commodity HTTP servers and our HTTP streaming server. Continuing our client-side pacing research, we developed our own client-side data proxy architecture which was implemented on a variety of mobile devices and operating systems. We used the portable client architecture as a platform for investigating different rate adaptation schemes and algorithms. We then concentrated on evaluating the network impact of multiple adaptive bitrate clients competing for limited network resources, and developing schemes for enforcing fair access to network resources. The main contribution of this dissertation is the definition of segment-level client and network techniques for enforcing class of service (CoS) differentiation between OTT HTTP adaptive streaming clients. We developed a segment-level network proxy architecture which works transparently with adaptive bitrate clients through the use of segment replacement. We also defined a segment-level rate adaptation algorithm which uses download aborts to enforce CoS differentiation across distributed independent clients. The segment-level abstraction more accurately models application-network interactions and highlights the difference between segment-level and packet-level time scales. Our segment-level CoS enforcement techniques provide a foundation for creating scalable managed OTT video delivery services

Design, analysis, and experimental verification of continuous media retrieval and caching strategies for network-based multimedia services

Ph.DDOCTOR OF PHILOSOPH

Dependable IPTV Hosting

This research focuses on the challenges of hosting 3rd party RESTful applications that have to meet specific dependability standards. To provide a proof of concept I have implemented an architecture and framework for the use case of internet protocol television. Delivering TV services via internet protocols over high-speed connections is commonly referred to as IPTV (internet protocol television). Similar to the app-stores of smartphones, IPTV platforms enable the emergence of IPTV services in which 3rd party developers provide services to consumer that add value to the IPTV experience. A key issue in the IPTV ecosystem is that currently telecommunications IPTV providers do not have a system that allows 3rd party developers to create applications that meet their standards. The main challenges are that the 3rd party applications must be dependable, scalable and adhere to service level agreements. This research provides an architecture and framework to overcome these challenges

External Media Announcement Approach For Media Resource Function Processor

Announcement application service is a multimedia service in IMS which plays media (audio/video) announcements to the User Equipment (UE). This thesis studies Media Resource Function Processor (MRFP), a key network component in IMS which is responsible for the announcement application service. This thesis looks into the MRFP architecture and tries to find a feasible and alternative approach to handle media announcements. The factors this thesis concentrates on are: (1) primarily, the limited availability of memory to store the media announcements within the MRFP, and (2) the possibility to reduce the number of Digital Signal Processors (DSPs) reserved for playing announcements. For a possible solution to the above mentioned research questions, this thesis proposes an external announcement approach to provide the announcement service.This is studied by using a separate server outside the MRFP node to store all the media announcement files. In this thesis, the external announcement approach is studied by using three different protocols - RTSP, HTTP or FTP as the interface between the MRFP node and the external server. The impact on the software architecture of MRFP due to the external announcement approach is studied. Also, a prototype is built to test the performance of the external announcement approach in an emulated Wide Area Network (WAN) environment. One other key area of study made in this thesis is to use the existing limited MRFP memory as a cache. The number of requests made to the external server to fetch the announcement files can be decreased by implementing an effective caching algorithm in the MRFP, which improves the performance. The study made shows that Greedy Dual-Size Popularity (GDSP) algorithm can be a relevant and very effective caching mechanism in MRFP. Through this work, it is demonstrated that an effective announcement service can be achieved in MRFP by using an external server

Active caching for recommender systems

Web users are often overwhelmed by the amount of information available while carrying out browsing and searching tasks. Recommender systems substantially reduce the information overload by suggesting a list of similar documents that users might find interesting. However, generating these ranked lists requires an enormous amount of resources that often results in access latency. Caching frequently accessed data has been a useful technique for reducing stress on limited resources and improving response time. Traditional passive caching techniques, where the focus is on answering queries based on temporal locality or popularity, achieve a very limited performance gain. In this dissertation, we are proposing an ‘active caching’ technique for recommender systems as an extension of the caching model. In this approach estimation is used to generate an answer for queries whose results are not explicitly cached, where the estimation makes use of the partial order lists cached for related queries. By answering non-cached queries along with cached queries, the active caching system acts as a form of query processor and offers substantial improvement over traditional caching methodologies. Test results for several data sets and recommendation techniques show substantial improvement in the cache hit rate, byte hit rate and CPU costs, while achieving reasonable recall rates. To ameliorate the performance of proposed active caching solution, a shared neighbor similarity measure is introduced which improves the recall rates by eliminating the dependence on monotinicity in the partial order lists. Finally, a greedy balancing cache selection policy is also proposed to select most appropriate data objects for the cache that help to improve the cache hit rate and recall further

A Framework for pervasive web content delivery

Ph.DDOCTOR OF PHILOSOPH