Temporal Locality in Today's Content Caching: Why it Matters and How to Model it

The dimensioning of caching systems represents a difficult task in the design of infrastructures for content distribution in the current Internet. This paper addresses the problem of defining a realistic arrival process for the content requests generated by users, due its critical importance for both analytical and simulative evaluations of the performance of caching systems. First, with the aid of YouTube traces collected inside operational residential networks, we identify the characteristics of real traffic that need to be considered or can be safely neglected in order to accurately predict the performance of a cache. Second, we propose a new parsimonious traffic model, named the Shot Noise Model (SNM), that enables users to natively capture the dynamics of content popularity, whilst still being sufficiently simple to be employed effectively for both analytical and scalable simulative studies of caching systems. Finally, our results show that the SNM presents a much better solution to account for the temporal locality observed in real traffic compared to existing approaches.Comment: 7 pages, 7 figures, Accepted for publication in ACM Computer Communication Revie

Proactive Mechanisms for Video-on-Demand Content Delivery

Video delivery over the Internet is the dominant source of network load all over the world. Especially VoD streaming services such as YouTube, Netflix, and Amazon Video have propelled the proliferation of VoD in many peoples' everyday life. VoD allows watching video from a large quantity of content at any time and on a multitude of devices, including smart TVs, laptops, and smartphones. Studies show that many people under the age of 32 grew up with VoD services and have never subscribed to a traditional cable TV service. This shift in video consumption behavior is continuing with an ever-growing number of users. satisfy this large demand, VoD service providers usually rely on CDN, which make VoD streaming scalable by operating a geographically distributed network of several hundreds of thousands of servers. Thereby, they deliver content from locations close to the users, which keeps traffic local and enables a fast playback start. CDN experience heavy utilization during the day and are usually reactive to the user demand, which is not optimal as it leads to expensive over-provisioning, to cope with traffic peaks, and overreacting content eviction that decreases the CDN's performance. However, to sustain future VoD streaming projections with hundreds of millions of users, new approaches are required to increase the content delivery efficiency. To this end, this thesis identifies three key research areas that have the potential to address the future demand for VoD content. Our first contribution is the design of vFetch, a privacy-preserving prefetching mechanism for mobile devices. It focuses explicitly on OTT VoD providers such as YouTube. vFetch learns the user interest towards different content channels and uses these insights to prefetch content on a user terminal. To do so, it continually monitors the user behavior and the device's mobile connectivity pattern, to allow for resource-efficient download scheduling. Thereby, vFetch illustrates how personalized prefetching can reduce the mobile data volume and alleviate mobile networks by offloading peak-hour traffic. Our second contribution focuses on proactive in-network caching. To this end, we present the design of the ProCache mechanism that divides the available cache storage concerning separate content categories. Thus, the available storage is allocated to these divisions based on their contribution to the overall cache efficiency. We propose a general work-flow that emphasizes multiple categories of a mixed content workload in addition to a work-flow tailored for music video content, the dominant traffic source on YouTube. Thereby, ProCache shows how content-awareness can contribute to efficient in-network caching. Our third contribution targets the application of multicast for VoD scenarios. Many users request popular VoD content with only small differences in their playback start time which offers a potential for multicast. Therefore, we present the design of the VoDCast mechanism that leverages this potential to multicast parts of popular VoD content. Thereby, VoDCast illustrates how ISP can collaborate with CDN to coordinate on content that should be delivered by ISP-internal multicast

Performance Evaluation of Scalable Multi-cell On-Demand Broadcast Protocols

As mobile data service becomes popular in today's mobile network, the data traffic burden irrevocably increases. LTE 4G, as the next-generation mobile technology, provides high data rates and improved spectral efficiency for data transmission. Currently in the mobile network, mobile data service solely relies on the point-to-point unicast transmission. In the ever-evolving 4G mobile network, mobile broadcast may serve as a supplemental means of pushing mobile data content from the data server to the mobile user devices. As part of the LTE 4G specifications, the mobile broadcast technology referred to as eMBMS is designed for supporting the mobile data service. From eMBMS, SFN broadcast transmission scheme allows data broadcasting to be synchronized in all cells of a defined core network area. LTE 4G also enables single-cell broadcast scheme in which data broadcasting is taking place independently in every cell. In this thesis, besides SFN or single-cell broadcast transmission, a hybrid broadcast transmission scheme in which SFN and single-cell broadcast transmission are used interchangeably in the same network based on the network conditions is proposed. For on-demand data service, the pull-based scheduling protocols from previous work are originally designed to work in a single-cell case scenario. With slight modifications, the batching/cbd protocol can be adapted for multi-cell data service. A new combined scheduling protocol, that is cyclic/cd,fft protocol, is devised as the second candidate for multi-cell data transmission scheduling. Based on the three broadcast transmission schemes and the two broadcast scheduling protocols, six mobile broadcast protocols are proposed. The mobile broadcast models, which correspond to the six mobile broadcast protocols, are evaluated by analysis and simulation experiment. By analysis, the cost equations are derived for calculating average server bandwidth, average client delay and maximum client delay of the mobile broadcast models. In the experiment, the input parameters of broadcast test models are assessed one at a time. The experimental results show that the hybrid broadcast transmission together with cyclic/cd,fft protocol would provide the best server bandwidth performance and the SFN broadcast transmission together with batching/cbd protocol provides the best average delay performance

On-device caching δημοφιλούς περιεχομένου βίντεο σε συσκευές με λειτουργικό σύστημα Android

Στην παρούσα εργασία επικεντρωνόμαστε στην τεχνική του on-device caching βίντεο κλιπ από διάφορες υπηρεσίες παροχής ροής βίντεο σε φορητές ασύρματες συσκευές. Στο πρώτο κεφάλαιο, γίνεται μια παράθεση των λόγων για τους οποίους οδηγηθήκαμε στην ανάγκη που πυροδότησε την έρευνα και ανάπτυξη των δικτύων 5G, καθώς και μια επισκόπηση των κύριων στόχων των δικτύων 5G, των βασικών υποδομών και τεχνολογιών που θα χρησιμοποιηθούν για την επίτευξη των στόχων αυτών και μια ποσοτική και ποιοτική σύγκριση των δικτύων 4G-LTE με τα δίκτυα 5G. Στο δεύτερο κεφάλαιο, γίνεται μια σύντομη αναφορά στις υποδομές του 5G στο φυσικό επίπεδο. Στο τρίτο κεφάλαιο γίνεται μια αναφορά στις cloud υποδομές του 5G μέσω των οποίων δίνεται η δυνατότητα του caching στο άκρο του δικτύου. Στο τέταρτο κεφάλαιο γίνεται μια αναφορά στο caching καθώς και στις διάφορες τεχνικές caching σε mobile δίκτυα. Στη συνέχεια, γίνεται μια αναφορά στη σημαντικότητα του caching περιεχομένου βίντεο σε φορητές συσκευές και στις διάφορες υπηρεσίες video streaming. Έπειτα, παρουσιάζεται η τεχνική του on-device caching σε συσκευή Android μέσω ήδη υπαρχουσών λύσεων και εφαρμογών οι οποίες το επιτυγχάνουν, αξιολογώντας και συγκρίνοντάς τες ως προς ποικίλα κριτήρια, όπως η διεπαφή χρήσης, η εμπειρία χρήσης, η δυνατότητα πολυνημάτωσης, κ.λ.π.. Στη συνέχεια, παραθέτουμε τα συμπεράσματά μας και προτείνουμε ιδέες για περαιτέρω βελτιώσεις και νέες λειτουργίες των ήδη υπαρχουσών λύσεων. Στο πέμπτο κεφάλαιο πραγματοποιούμε μια ανακεφαλαίωση και παραθέτουμε τα σημαντικότερα συμπεράσματά μας.In this thesis, we focus on the on-device video caching from various video streaming services on wireless mobile devices. In the first chapter, we cite the main reasons that lead to the need for research and development of the 5G networks and we provide an overview of the main goals of the 5G networks, the basic infrastructures and technologies that will be used in achieving these goals, as well as a qualitative and quantitative comparison between 4G-LTE networks and 5G networks. In the second chapter, we make a short reference to the 5G physical layer infrastructure. In the third chapter, we make a reference to the 5G cloud infrastructure, which enables caching at the network edge. In the fourth chapter, we make a reference to caching and the various caching techniques in mobile networks. Then, we deal with the importance of video caching on mobile devices and various video streaming services. In the sequel, we present the on-device caching technique on Android-powered mobile devices using already existing solutions and applications through which video caching on mobile devices can be achieved, evaluating and comparing them to each other, based on characteristics such as the user interface, the user experience, the multithread implementation, etc.. Finally, we present our conclusions and we suggest some ideas for further improvements and extra features to those applications. In the fifth chapter, we summarize this work and present our main conclusions

Serviços OTT TV: aspectos técnico-económicos

Mestrado em Engenharia Eletrónica e TelecomunicaçõesThe breadth of availability and variety of online video contents has helped to encourage a far more mobile experience, which has proved particularly popular among younger generations. Over The Top (OTT) services, particularly those on-demand video platforms, became more and more attractive to consumers when compared with the current main TV packages. This document describes how the video OTT Ecosystem works from a technical side. The description presented reaches both ends of the distribution chain: from how the video signals are acquired and processed, thru all the way to how they are delivered to the client, passing by the challenges and consequences that such services have on the network. The main objective of this dissertation is to understand the possibility to create in Portugal a new operator where the core business is video delivery using only OTT services.A amplitude e variedade de conteúdos disponíveis online têm ajudado a promover uma experiência cada ver mais móvel da televisão, serviço que se tem revelado particularmente popular entre os mais jovens. Serviços Over The Top (OTT), sobretudo aqueles disponíveis através de plataformas de video on-demand, têm-se tornado cada vez mais atraentes para os consumidores, em comparação com os atuais pacotes de televisão. Este documento descreve como funciona, do ponto de vista técnico, o ecossistema do vídeo sobre OTT. A descrição apresentada abrange ambas as extremidades da cadeia de distribuição: desde a forma como os sinais de vídeo são adquiridos e processados até ao modo como eles são entregues ao cliente, passando pelos problemas e consequências que tais serviços podem ter na rede. O principal objectivo deste trabalho é contribuir para compreender se é possível criar em Portugal um novo operador onde o core business seja a distribuição de vídeo utilizando apenas serviços OTT

Untangling the Web: A Guide To Internet Research

[Excerpt] Untangling the Web for 2007 is the twelfth edition of a book that started as a small handout. After more than a decade of researching, reading about, using, and trying to understand the Internet, I have come to accept that it is indeed a Sisyphean task. Sometimes I feel that all I can do is to push the rock up to the top of that virtual hill, then stand back and watch as it rolls down again. The Internet—in all its glory of information and misinformation—is for all practical purposes limitless, which of course means we can never know it all, see it all, understand it all, or even imagine all it is and will be. The more we know about the Internet, the more acute is our awareness of what we do not know. The Internet emphasizes the depth of our ignorance because our knowledge can only be finite, while our ignorance must necessarily be infinite. My hope is that Untangling the Web will add to our knowledge of the Internet and the world while recognizing that the rock will always roll back down the hill at the end of the day

Mashup Ecosystems: Integrating Web Resources on Desktop and Mobile Devices

The Web is increasingly used as an application platform, and recent development of it has introduced software ecosystems where different actors collaborate. This collaboration is international from day one, and it evolves and grows rapidly. In web ecosystems applications are provided as services, and interdependencies between ecosystem parts can vary from very strong and obvious to loose and recondite. Mashups -- web application hybrids that combine resources from different services into an integrated system that has increased value from user perspective -- are exploiting services of the Web and creating ecosystems where end-users, mashup authors, and service providers collaborate. The term "resources" is used here in a broad sense, and it can refer to user's local data, infinite content of the Web, and even executable code. This dissertation presents mashups as a new breed of web applications that are intended for parsing the web content into an easily accessed form on both regular desktop computers as well as on mobile devices. Constantly evolving web technologies and new web services open up unforeseen possibilities for mashup development. However, developing mashups with current methods and tools for existing deployment environments is challenging. First, the Web as an application platform faces numerous shortcomings, second, web application development practices in general are still immature, and third, development of mashups has additional requirements that need to be addressed. In addition, mobility sets even more challenges for mashup authoring. This dissertation describes and addresses numerous issues regarding mashup ecosystems and client-side mashup development. To achieve this, we have implemented technical research artifacts including mashup ecosystems and different kinds of mashup compositions. The artifacts are developed with numerous runtime environments and tools and targeted at different end-user platforms. This has allowed us to evaluate methods, tools, and practises used during the implementation. As result, this dissertation identifies the fundamental challenges of mashup ecosystems and describes how service providers and mashup ecosystem authors can address these challenges in practice. In addition, example implementation of a specialized multimedia mashup ecosystem for mobile devices is described. To address mashup development issues, this dissertation introduces practical guidelines and a reference architecture that can be applied when mashups are created with traditional web development tools. Moreover, environments that can be used on mobile devices to create mashups that have access to both web and local resources are introduced. Finally, a novel approach to web software development -- creating software as a mashup -- is introduced, and a realization of such concept is described

Cacheability of YouTube Videos in Cellular Networks

Video traffic now represents a growing proportion of the traffic on cellular networks, causing capacity problems for operators and increased delays for users. Studies have shown that deploying caches at the network level reduces the delay for the end-user and the overall traffic volume for the telecom operator. In this paper, we analyse a large nationwide dataset of real-life video requests sent by mobile users to a popular video streaming website. This analysis is the first to rely on such a large dataset, and sheds light on the optimal cacheability of video content with caches distributed in the cellular network, and how efficient some existing cache replacement algorithms are at reducing the number of requests sent to the video provider. We show that depending on the cache size and algorithm parameters, up to 20.33% of the requests can be served by a local cache