On the impact of redirection on HTTP adaptive streaming services in federated CDNs

HTTP Adaptive Streaming (HAS) refers to a set of novel streaming services that allow clients to adapt video quality based on current network conditions. Their use of existing HTTP delivery infrastructure makes them perfectly suited for deployment on existing Content Delivery Networks (CDNs). Nevertheless, this leads to some new challenges, related to the distribution of content across servers and the latency caused by request redirection. The federation or interconnection of CDNs proliferates these problems, as it allows content to be distributed across networks and increases the number of redirects. This paper focuses on the second problem, assessing the impact of redirection on the Quality of Experience of HAS in CDN interconnection scenarios. Additionally, several novel inter-CDN request routing policies are proposed that aim to reduce the number of redirects. Our results indicate that redirection latency significantly impacts performance of HAS and more intelligent routing mechanisms are capable of solving this problem

An Experimental Evaluation of Akamai Adaptive Video Streaming over HSDPA networks

Adaptive video streaming is a relevant advancement with respect to classic progressive download streaming such as the one employed by YouTube. Building upon its content delivery network (CDN), Akamai recently started to offer High Definition (HD) adaptive video streaming using HTTP. Nowadays, not only the amount of Internet video traffic is always increasing but also the number of users accessing the Internet using wireless links. In this paper we experimentally investigate the switching algorithm employed by Akamai to implement video quality adaptation over a High Speed Downlink Data Packet Access (HSDPA) link. In order to assess the Quality of Experience we measure goodput, TCP friendliness, and video reproduction continuity. Main results are: 1) Akamai flows are not able to achieve the fair share when competing with a TCP greedy flow due to the conservativeness of the stream-switching algorithm; 2) when the link is shared with a greedy TCP connection in 50% of the experiments the video reproduction was paused for more than 19% of the experiment duration

QoE for Mobile Streaming

No abstract

Cache-Version Selection and Content Placement for Multi-Resolution Video Streaming in Information-Centric Networks

Information Centric Networks (ICN) is an infrastructure that focuses on information retrieval rather than end to end connections. ICN uses 2 features - name based routing and in-network caching in order to attain better performance. Named Data Networks (NDN) is an architecture for Information Centric Networks (ICN). In this thesis, we implement a version selection cum content placement policy (CaVe-CoP) that takes advantage of both features. We focus on multi-resolution video streaming and implement a scheme where only an optimal set of resolutions of videos need to be cached in order to obtain higher network utility. This distinction between multiple resolutions of the same video is possible today because of the varied devices available for video streaming that have different resolution constraints. We first formulate and solve an optimization problem for version selection and content placement in a generic network that supports multi-resolution video streaming and has in-network caches. Next, we implement the solution in an NDN-compliant framework (ndnSIM) as a distributed algorithm. We compare our policy against 2 other policies - 1) where all resolutions of a content are cached, and 2) where the user opts for a greedy version selection. Our simulations on general network topologies show a fast convergence rate, higher utility and a lower stall time in comparison to both these policies

Entwurf eines Überlast-Reglers unter Berücksichtigung des Netzzustandes und möglicher Überlast-Beschränkungen

Auf dem Pfad eines Nutzers, der eine Verbindung mit einem Dienst über das Internet aufbaut, liegen typischerweise einer oder mehrere Router. Jeder dieser Router hat einen gewissen Pufferspeicher für Pakete (Routerqueue). Sobald der Router Pakete schneller empfängt, als er sie weiterleiten kann, füllt sich dieser Puffer. Bei einem Überlauf des Puffers kommt es zum Paketverlust, da der Router weitere ankommende Pakete verwerfen muss. Dieses Verwerfen führt entweder zu komplettem Datenverlust, oder einem erneuten Senden der Daten und bringt damit Verzögerungen mit sich, die für Echtzeitanwendungen oder Streaming problematisch sind. Das erneute Senden von Daten, wie es vom Transmission Control Protocol (TCP) bei Verlust gemacht wird, sorgt dafür, dass der Empfänger garantiert Daten erhält. Allerdings füllt sich dadurch wiederum die Routerqueue und verschlimmert daher möglicherweise die Überlastsituation. Ein Ansteigen der Latenzzeit durch größere Pufferfüllstände ist eine weitere unangenehme Folge des erneuten Sendens. Häufig wird versucht, die unterschiedlichen Anforderungen von einzelnen Verkehrsarten mit einer gezielten Priorisierung an den Zwischenroutern zu lösen. Hierbei wird Echtzeitverkehr mit einer höheren Priorität versendet, wie zeitunkritischer Verkehr, welcher länger im Routerpuffer verweilen muss. Im Gegensatz zu Verkehrspriorisierungen wird in dieser Diplomarbeit versucht, mit einem Adaptionsregler auf die Überlastsituation zu reagieren, um nicht nur in einer Überlastsituation gezielt manchen Verkehr zu bevorteilen, sondern aktiv den erzeugten Verkehr und damit die Überlastsituation zu reduzieren. Dieser Ansatz hat den Vorteil, dass nur ein Feedback über den Netzzustand benötigt wird, und man nicht auf intelligentere Router angewiesen ist, die Pakete priorisieren können

Throughput and Delay on the Packet Switched Internet

The Internet has become a vital and essential part of modern everyday life. Services delivered by the Internet are used by people across the planet every moment of every day of the year. The Internet has proven a positive force for good improving the lives of billions of people worldwide. The power of the Internet to deliver this positive good to humanity relies on its ability to deliver life improving services. In my doctorate work culminating in this dissertation I have striven to sustain and increase the Internet's ability to deliver these services and to have a positive good effect upon humanity.The overarching purpose of this dissertation is to improve the Internet's ability to deliver life improving services. I have further divided this purpose into two goals. To improve the ability of applications operating in challenging network conditions to gain their fair share of the bandwidth resources and to reduce the delay with which these services are delivered. Every service delivered by the Internet consists of Internet objects that are delivered through communication paths across the Internet. The delivery of these objects is defined by the two characteristics; Throughput and delay. Throughput determines how much of an object can be delivered over a period of time and delay determines how long it takes to deliver an object.These two characteristics determine the Internet's ability to deliver objects across communication paths. Improving these two characteristics (bandwidth and delay) increase the ability of the Internet to deliver objects and thus improve the Internet's capability to deliver life improving services. To accomplish this goal I present projects along three areas of effort. These three areas of effort are: (1) Increase the ability of applications operating in challenging conditions to achieve their fair share of bandwidth. (2) Synthesize knowledge required to address the effort to reduce delay. (3) Develop protocols that reduce delay encountered in the communications paths of the Internet.In this dissertation I present projects along these three areas of effort that accomplish the two goals (increase bandwidth and reduce delay) to achieve the purpose of improving the Internet's ability to deliver essential and life improving services. These projects and their organization into areas of effort, goals and purpose are my contributions to the networking sciences

Improving ABR Video Streaming Design with Systematic QoE Measurement and Cross Layer Analysis

Adaptive Bitrate streaming (ABR) has been widely adopted by mobile video services to deliver satisfying Quality of Experience (QoE) over cellular network with time-varying bandwidth conditions. To build an ABR service, a wide range of critical components spanning different entities need to be determined. It is challenging to achieve designs with good QoE properties, as the streaming performance depends on complex interactions among the various factors. To make it more complex, many design decisions also involve tradeoffs among different QoE metrics. To address this challenge, in this dissertation, we build four systems to provide systematic support for video QoE measurements and cross-layer analysis. First, we build a general black-box measurement platform based on standard ABR protocols and common UI designs. It analyzes HTTP information in the network traffic and correlates UI events of mobile video apps to reveal ABR design and identify QoE issues. Second, to address the challenge brought by increasingly adopted encryption protocols such HTTPS and QUIC, we develop a technique called CSI to infer ABR video adaptation behavior based on packet size and timing information still available in the encrypted traffic. Third, we explore a conceptually very different approach to QoE measurement --- utilizing the on-device recording capability to record the video displayed on the mobile device screen and measuring delivered QoE from this recording. We design a novel system VideoEye to conduct such screen-recording-based QoE analysis. Lastly, to understand the interaction of existing video streaming system design with the new transport protocol QUIC, we build a platform WIQ to perform what-if analysis and measure the video QoE impact of QUIC without the need of modifying the server or client implementation. Leveraging these systems, we perform measurements on popular streaming services, understand the QoE implications of various ABR design, identify a wide range of QoE issues and develop best practices.PHDComputer Science & EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttps://deepblue.lib.umich.edu/bitstream/2027.42/155039/1/xsc_1.pd

Amélioration de la transmission de contenus vidéo et de données dans les réseaux sans-fil

Cette thèse traite de l amélioration du transfert de données, d une part sur les réseaux sans-fils et d autre part pour des données continues telles que la vidéo. Pour améliorer les transmissions sur les réseaux sans-fils nous nous sommes intéressés au contrôle de congestion des protocoles de transport mais nous avons également proposé une méthode pratique d adaptation de la vidéo aux conditions du réseau.Cette thèse contient donc deux volets. La première porte sur la différenciation de pertes entre les pertes de congestion et les pertes sur le réseau sans fil. Il est connu que lors d une perte, les protocoles de transport actuels réduisent le débit (par deux par exemple). Or, pour les pertes sans fil, cela n a pas d intérêt. Pour différencier ces pertes sur l émetteur des données, nous proposons une méthode originale qui utilise à la fois ECN (Explicit Congestion Notification) et le changement sur le RTT du paquet qui suit la perte. La seconde propose une méthode originale d adaptation vidéo au niveau de la couche application sur l émetteur. Avec l arrivée des vidéos à bitrate élevés (HD, 3D) et l augmentation constante mais irrégulière des bandes passantes réseau, la qualité vidéo à l utilisateur reste à la traîne : elle est non-optimale (bitrate beaucoup plus petit ou plus grand que le débit disponible) et non adaptable (aux conditions dynamiques du réseau). Nous proposons une méthode très simple à implémenter, puisqu elle ne requiert qu une modification côté émetteur au niveau de la couche application. Elle adapte en permanence le bitrate de la vidéo aux conditions du réseau, autrement dit elle fait un contrôle de congestion sur l émetteur. La visioconférence est un cas d application idéal. Cette méthode fonctionne au-dessus de tout protocole de transport avec contrôle de congestion (TCP, DCCP), ce qui lui confère aussi la propriété de TCP-friendliness.This thesis deals in improving the data transfer on wireless networks and for the continuous data such as video. To improve transmission over wireless networks, we were interested in congestion control transport protocols and we also proposed a practical method for adjusting the video rate to network conditions.This thesis composes of two parts. The first part concerns the loss differentiation between congestion losses and losses on the wireless network. It is known that when there is a loss, transport protocols reduce the current sending rate (e.g. by two). However, for wireless losses, it has no interest in reducing the rate. To differentiate these losses on the data senders side, we propose a novel method that uses both the ECN (Explicit Congestion Notification) and the change of RTT of the packet following the loss. The second part proposes a novel method for video adaptation at the application layer of the sender. With the advent of high bitrate video (e.g. HD, 3D) and steadily increasing but irregular network bandwidth, video quality to the user lags. It is non-optimal (bitrate is highly smaller or larger than the available bandwidth) and not adaptable (to the dynamic conditions of the network). We propose a simple method to implement, since it requires a change only at the application layer of the sender. It adapts the bitrate of the video to the network conditions, i.e. it is a congestion control on the transmitter. Videoconferencing is an ideal case for the application of adaptation. This method works over any transport protocol with congestion control (e.g. TCP, DCCP), which also confers the property of TCP-friendliness.BESANCON-Bib. Electronique (250560099) / SudocSudocFranceF