Reboot-based Recovery of Performance Anomalies in Adaptive Bitrate Video-Streaming Services

Performance anomalies represent one common type of failures in Internet servers. Overcoming these failures without introducing server downtimes is of the utmost importance in video-streaming services. These services have large user abandon- ment costs when failures occur after users watch a significant part of a video. Reboot is the most popular and effective technique for overcoming performance anomalies but it takes several minutes from start until the server is warmed-up again to run at its full capacity. During that period, the server is unavailable or provides limited capacity to process end-users’ requests. This paper presents a recovery technique for performance anomalies in HTTP Streaming services, which relies on Container-based Virtualization to implement an efficient multi-phase server reboot technique that minimizes the service downtime. The recovery process includes analysis of variance of request-response times to delimit the server warm-up period, after which the server is running at its full capacity. Experimental results show that the Virtual Container recovery process completes in 72 seconds, which contrasts with the 434 seconds required for full operating system recovery. Both recovery types generate service downtimes imperceptible to end-users

Implementación de redes overlay jerárquicas usando el protocolo P2PP

En los últimos años, la transmisión de contenido multimedia se ha convertido en uno de los servicios más usados de Internet dando lugar a arquitecturas de red que se desmarcan de los tradicionales modelos cliente servidor. Sin embargo, la popularidad de estas aplicaciones no ha ido acompañada de un igual avance en su estudio y entendimiento. Entre estas nuevas estructuras se encuentran las redes overlay, uno de cuyos usos más extendidos es la creación de redes P2P. Estas redes se caracterizan por crear una red sobre Internet con una topología lógica completamente diferente a la del nivel de red. Dependiendo de la manera en la que se genere esta topología las podemos denominar estructuradas o no estructuradas. El objetivo principal de este proyecto es demostrar la mejora de rendimiento que supone el añadir un modelo jerárquico a una red overlay estructurada. Para ello buscamos una implementación disponible de una de estas redes y la modificamos para que funcione jerárquicamente. En este caso el protocolo elegido ha sido Peer-to-Peer Protocol (P2PP). Tras realizar las modificaciones necesarias para que el software funcionara de acorde a nuestras necesidades, se paso a una fase de diseño y realización de pruebas en una red emulada usando el software ModelNet. Finalmente se analizaron los resultados obtenidos llegando a la conclusión de que la inclusión de la jerarquía mejora el rendimiento de la red de una manera notable según crece el número de nodos participantes en la red.Ingeniería de Telecomunicació

A Content Delivery Model for Online Video

Online video accounts for a large and growing portion of all Internet traffic. In order to cut bandwidth costs, it is necessary to use the available bandwidth of users to offload video downloads. Assuming that users can only keep and distribute one video at any given time, it is necessary to determine the global user cache distribution with the goal of achieving maximum peer traffic. The system model contains three different parties: viewers, idlers and servers. Viewers are those peers who are currently viewing a video. Idlers are those peers who are currently not viewing a video but are available to upload to others. Finally, servers can upload any video to any user and has infinite capacity. Every video maintains a first-in-first-out viewer queue which contains all the viewers for that video. Each viewer downloads from the peer that arrived before it, with the earliest arriving peer downloading from the server. Thus, the server must upload to one peer whenever the viewer queue is not empty. The aim of the idlers is to act as a server for a particular video, thereby eliminating all server traffic for that video. By using the popularity of videos, the number of idlers and some assumptions on the viewer arrival process, the optimal global video distribution in the user caches can be determined

Automatización de instalación y configuración de aplicaciones peer-to-peer en un entorno virtualizado basado en Modelnex y Proxmox

Desde hace unos años, el tráfico generado por el intercambio y transferencia de contenido multimedia en Internet usando arquitecturas distintas a las cliente-servidor ha ido en creciente aumento. De ahí, tecnologías como la P2P (peer-to-peer) están teniendo mucho éxito y por eso se está trabajando en su estudio, entendimiento y desarrollo de nuevas soluciones de manera muy activa. Un tipo de estas arquitecturas son las redes overlay, que lo que hacen es crear una red sobre Internet con una topología lógica diferente a la del nivel de red. Dependiendo de la manera en que se genere serán estructuradas o no. El principal objetivo de este proyecto es diseñar una herramienta que automatice todo el proceso previo a la realización de experimentos enfocados a la demostración, estudio y evaluación del rendimiento de redes overlay, dotando así a desarrolladores e investigadores con una aplicación que les ayudará a la obtención de resultados y conclusiones con mayor rapidez, facilidad y fiabilidad centrando su atención exclusivamente en el desarrollo de sus propios experimentos, siendo estos el paso anterior al despliegue en entornos reales como Internet. Una vez desarrollada la herramienta, se ha procedido a la comprobación y validación de esta usando una red emulada creada por el software Modelnet, que nos permite crear clusters de emulación de una manera escalable y flexible. Finalmente se procedió a la realización de unos experimentos nuevos con el objetivo de añadir más información al desarrollo del estudio en este ámbito. Por último, cabe destacar el uso de PROXMOX como el entorno de virtualización y monitorización de equipos físicos usado durante el proyecto para realizar experimentos, capaz de gestionar un número elevado de nodos virtuales, que en este caso fueron 1000. _____________________________________________________________________________________________________________In recent years, the traffic generated by the exchange and transfer of multimedia content over the Internet using different architectures to client-server has been on the growing increase. Hence, technologies such as P2P (peer-to-peer) are having so much success and are working in his study, understanding and developing new solutions very active. One type of these architectures are overlay networks that they do is create a network on the Internet with a different logical topology of the network level. Depending on how they generate will be structured or not. The main objective of this project is to design a tool that automates the whole process prior to the completion of experiments focused on the demostration and evaluation study of the performance of overlay networks, thus providing developers and researchers with an application that will help them obtain results and conclusions more quickly, easily and reliably to focus exclusively on developing their own experiments, and these pre-deployment step in real environments as the Internet. Once the tool has been developed process of verification and validation is using an emulated network created by the Modelnet software that lets you create clusters of emulation in a scalable and flexible. Finally we proceeded to carry out new experiments in order to add more information to study development in this area. Finally, it should emphasize the use of Proxmox as the virtualization environment and monitoring of hardware used for the project to conduct experiments that can handle a large number of virtual nodes, which in this case was 1000.Ingeniería Técnica en Sonido e Image

Content Replication and Placement Schemes for Wireless Mesh Networks

Recently, Wireless Mesh Networks (WMNs) have attracted much of interest from both academia and industry, due to their potential to provide an alternative broadband wireless Internet connectivity. However, due to different reasons such as multi-hop forwarding and the dynamic wireless link characteristics, the performance of current WMNs is rather low when clients are soliciting Web contents. Due to the evolution of advanced mobile computing devices; it is anticipated that the demand for bandwidth-onerous popular content (especially multimedia content) in WMNs will dramatically increase in the coming future. Content replication is a popular approach for outsourcing content on behalf of the origin content provider. This area has been well explored in the context of the wired Internet, but has received comparatively less attention from the research community when it comes to WMNs. There are a number of replica placement algorithms that are specifically designed for the Internet. But they do not consider the special features of wireless networks such as insufficient bandwidth, low server capacity, contention to access the wireless medium, etc. This thesis studies the technical challenges encountered when transforming the traditional model of multi-hop WMNs from an access network into a content network. We advance the thesis that support from packet relaying mesh routers to act as replica servers for popular content such as media streaming, results in significant performance improvement. Such support from infrastructure mesh routers benefits from knowledge of the underlying network topology (i.e., information about the physical connections between network nodes is available at mesh routers). The utilization of cross-layer information from lower layers opens the door to developing efficient replication schemes that account for the specific features of WMNs (e.g., contention between the nodes to access the wireless medium and traffic interference). Moreover, this can benefit from the underutilized resources (e.g., storage and bandwidth) at mesh routers. This utilization enables those infrastructure nodes to participate in content distribution and play the role of replica servers. In this thesis, our main contribution is the design of two lightweight, distributed, and scalable object replication schemes for WMNs. The first scheme follows a hierarchical approach, while the second scheme follows a flat one. The challenge is to replicate content as close as possible to the requesting clients and thus, reduce the access latency per object, while minimizing the number of replicas. The two schemes aim to address the questions of where and how many replicas should be placed in the WMN. In our schemes, we consider the underlying topology joint with link-quality metrics to improve the quality of experience. We show using simulation tests that the schemes significantly enhance the performance of a WMN in terms of reducing the access cost, bandwidth consumption and computation/communication cost

The pragmatics of monologue: interaction in video blogs

This study reports an in-depth pragmatic analysis of spoke monologues as they appear in video blogs (vlogs). Vlogs are videos of a person talking into the camera, which are edited and subsequently uploaded to video sharing websites such as YouTube, where they appear in a highly multimodal environment. Using methods situated in the fields of Conversation Analysis, Interactive Sociolinguistics and multimodality studies, the research presented investigates a wide range of speaker strategies. These strategies are studied with regard to their form, frequency of occurrence, how they are adapted to the specific context of language use and, where possible, what effect this has on vlog viewers. The strategies and phenomena under investigation are the openings and closings of monologues; repetition and involvement strategies; pointing gestures and video-comment coherence in the virtual online space. Comparison with another monologic genre, the TED Talk, reveals that the monologue setting itself is an influential variable that naturally shapes a vlogger’s or lecturer’s way of speaking compared to conversational settings. However, more specifically, the comparison also shows that the contextual differences between a stage monologue at a TED conference and a camera monologue as part of a vlog, can be significant in terms of their influence on the interaction that takes place.Diese Forschungsarbeit untersucht gesprochene Monologe wie sie in Videoblogs (Vlogs) vorkommen aus linguistisch-pragmatischer Sicht. Vlogs sind Videos von Menschen, die in die Kamera sprechen. Diese Videos werden nach der Aufnahme bearbeitet und dann auf Videoseiten im Internet, wie zum Beispiel YouTube, hochgeladen, wo sie im Rahmen einer multimodal komplexen Webseite einer breiten Öffentlichkeit zugänglich sind. Die Vlogmonologe werden mit Hilfe von Methoden aus der Konversationsanalyse, der Interaktionalen Soziolinguistik und Studien zur Multimodalität auf die Strategien der Sprecher beleuchtet. Diese Strategien werden untersucht im Hinblick auf ihre Form, Häufigkeit, wie sie an den spezifischen Sprechkontext angepasst sind und, wo möglich, was für einen Effekt sie auf die Zuschauer haben. Die Strategien und Phänomene, die hier untersucht werden sind Anfangs- und Schlusssequenzen; Wiederholungen und Involvement-Strategien; Zeigegesten und die Kohärenz zwischen Video und Zuschauerkommentaren im virtuellen Raum. Der Vergleich mit einer anderen monologischen Gattung, dem TED-Talk, zeigt, dass die Sprechsituation im Monolog eine einflussreiche Variable ist verglichen mit konversationellen Situationen. Der Vergleich zeigt aber weiterhin, dass die kontextuellen Unterschiede zwischen Vlogs, die vor der Kamera entstehen, und TED Talks, die auf einer Bühne vor Publikum vorgetragen werden, signifikant sein können hinsichtlich ihres Einflusses auf die stattfindende Interaktion

Content distribution infrastructures for community networks

Multimedia content delivery has undergone dramatic changes in recent years. The roles of content providers and producers are no longer restricted to a few professional organisations since more and more users share audiovisual content or use community sites to support their common interest. Nowadays both portable multimedia devices (e.g. PDAs, mobile phones, MP3 recorders, and digital cameras) and home entertainment systems (e.g., set-top boxes, game consoles, and media-centres) have become integral parts of the content production and distribution chain. Further, the underlying delivery infrastructure is undergoing major changes. There is a shift away from the traditional client/server model to systems based on the peer-to-peer paradigm, which let users share computational, storage and bandwidth resources. Moreover, the physical infrastructure is evolving towards some form of spontaneous cooperation of technologies to support the creation of wireless ad hoc networks or wireless community networks. Thus, the well known engineering problem of delivering multimedia content through the Internet is evolving into the problem of how to dynamically create content distribution infrastructures and services. The above considerations motivated us to promote this Special Issue of ‘‘Computer Networks”. The specific purpose of it is to present recent advances in the study of content distribution infrastructures from a networking perspective