Exploiting Traffic Balancing and Multicast Efficiency in Distributed Video-on-Demand Architectures

Distributed Video-on-Demand (DVoD) systems are proposed as a solution to the limited streaming capacity and null scalability of centralized systems. In a previous work, we proposed a fully distributed large-scale VoD architecture, called Double P-Tree, which has shown itself to be a good approach to the design of flexible and scalable DVoD systems. In this paper, we present relevant design aspects related to video mapping and traffic balancing in order to improve Double P-Tree architecture performance. Our simulation results demonstrate that these techniques yield a more efficient system and considerably increase its streaming capacity. The results also show the crucial importance of topology connectivity in improving multicasting performance in DVoD systems. Finally, a comparison among several DVoD architectures was performed using simulation, and the results show that the Double P-Tree architecture incorporating mapping and load balancing policies outperforms similar DVoD architectures.This work was supported by the MCyT-Spain under contract TIC 2001-2592 and partially supported by the Generalitat de Catalunya- Grup de Recerca Consolidat 2001SGR-00218

Bandwidth Borrowing Schemes for Instantaneous Video-on-Demand Systems

A controlled multicast scheme provides instantaneous service, but limited server bandwidth causes some user requests to be either delayed or rejected when insufficient free bandwidth is available. Two borrowing schemes are proposed for instantaneous video-on-demand (VOD) that reduce the user request blocking rate by borrowing bandwidth from ongoing video streams when there is insufficient free bandwidth for the server to deliver a new video stream. Both these new schemes have proved to be successful in reducing blocking rate and increasing bandwidth utilization at the expense of temporarily degrading the video quality

Popularity-Based Adaptive Content Delivery Scheme with In-Network Caching

To solve the increasing popularity of video streaming services over the Internet, recent research activities have addressed the locality of content delivery from a network edge by introducing a storage module into a router. To employ in-network caching and persistent request routing, this paper introduces a hybrid content delivery network (CDN) system combining novel content routers in an underlay together with a traditional CDN server in an overlay. This system first selects the most suitable delivery scheme (that is, multicast or broadcast) for the content in question and then allocates an appropriate number of channels based on a consideration of the content’s popularity. The proposed scheme aims to minimize traffic volume and achieve optimal delivery cost, since the most popular content is delivered through broadcast channels and the least popular through multicast channels. The performance of the adaptive scheme is clearly evaluated and compared against both the multicast and broadcast schemes in terms of the optimal in-network caching size and number of unicast channels in a content router to observe the significant impact of our proposed scheme

Enabling Large-Scale Peer-to-Peer Stored Video Streaming Service with QoS Support

This research aims to enable a large-scale, high-volume, peer-to-peer, stored-video streaming service over the Internet, such as on-line DVD rentals. P2P allows a group of dynamically organized users to cooperatively support content discovery and distribution services without needing to employ a central server. P2P has the potential to overcome the scalability issue associated with client-server based video distribution networks; however, it brings a new set of challenges. This research addresses the following five technical challenges associated with the distribution of streaming video over the P2P network: 1) allow users with limited transmit bandwidth capacity to become contributing sources, 2) support the advertisement and discovery of time-changing and time-bounded video frame availability, 3) Minimize the impact of distribution source losses during video playback, 4) incorporate user mobility information in the selection of distribution sources, and 5) design a streaming network architecture that enables above functionalities.To meet the above requirements, we propose a video distribution network model based on a hybrid architecture between client-server and P2P. In this model, a video is divided into a sequence of small segments and each user executes a scheduling algorithm to determine the order, the timing, and the rate of segment retrievals from other users. The model also employs an advertisement and discovery scheme which incorporates parameters of the scheduling algorithm to allow users to share their life-time of video segment availability information in one advertisement and one query. An accompanying QoS scheme allows reduction in the number of video playback interruptions while one or more distribution sources depart from the service prematurely.The simulation study shows that the proposed model and associated schemes greatly alleviate the bandwidth requirement of the video distribution server, especially when the number of participating users grows large. As much as 90% of load reduction was observed in some experiments when compared to a traditional client-server based video distribution service. A significant reduction is also observed in the number of video presentation interruptions when the proposed QoS scheme is incorporated in the distribution process while certain percentages of distribution sources depart from the service unexpectedly

Control evaluation in a LVoD system based on a peer-to-peer multicast scheme

Providing Quality of Service (QoS) in video on demand systems (VoD) is a challenging problem. In this paper, we analyse the fault tolerance on a P2P multicast delivery scheme, called Patch Collaboration Manager / Multicast Channel Distributed Branching (PCM/MCDB) [13]. This scheme decentralizes the delivery process between clients and scales the VoD server performance. PCM/MCDB synchronizes a group of clients in order to create local network channels to replace on-going multicast channels from the VoD server. Using the P2P paradigm supposes facing the challenge of how often peers connect and disconnect from the system. To address this problem, a centralized mechanism is able to replace the failed client. We evaluate the failure management process of the centralized scheme in terms of the overhead injected into the network and analyse the applicability of a distributed approach to managing the process. Analytical models are developed for centralized and distributed approaches. Their behaviour are compared in order to evaluate whether the distributed scheme can improve the fault management process, in terms of reducing server load and generating better scalability.Proporcionar Calidad de Servicio (QoS) en sistemas de Vídeo bajo Demanda (VoD) es un problema desafiador. En este artículo, analizamos la tolerancia a fallos en un esquema de envío de informaciones, basado en comunicaciones multicast y colaboraciones P2P, denominado PCM/MCDB [13]. El esquema descentraliza el proceso de envío de información entre los clientes y escala las prestaciones del servidor de VoD. PCM/MCDB sincroniza un grupo de clientes con objeto de crear canales de redes locales para reemplazar canales multicast en curso del servidor. La aplicación del paradigma P2P supone cómo afrontar el problema de la conexión y desconexión de clientes del sistema. Para resolver este problema, un mecanismo centralizado es capaz de reemplazar el cliente fallido. En el trabajo evaluamos el proceso de gestión de fallos del esquema centralizado en términos del flujo de informaciones insertado en la red y analizamos la aplicabilidad de un esquema distribuido para el proceso de gestión. Modelos analíticos son desarrollados para las aproximaciones centralizada y distribuida. Sus comportamientos son comparados con objeto de evaluar si un esquema distribuido puede mejorar el proceso de gestión de fallos desde el punto de vista de reducir la carga del servidor y proporcionar mejor escalabilidad.VIII Workshop de Procesamiento Distribuido y ParaleloRed de Universidades con Carreras en Informática (RedUNCI

Control evaluation in a LVoD system based on a peer-to-peer multicast scheme

Providing Quality of Service (QoS) in video on demand systems (VoD) is a challenging problem. In this paper, we analyse the fault tolerance on a P2P multicast delivery scheme, called Patch Collaboration Manager / Multicast Channel Distributed Branching (PCM/MCDB) [13]. This scheme decentralizes the delivery process between clients and scales the VoD server performance. PCM/MCDB synchronizes a group of clients in order to create local network channels to replace on-going multicast channels from the VoD server. Using the P2P paradigm supposes facing the challenge of how often peers connect and disconnect from the system. To address this problem, a centralized mechanism is able to replace the failed client. We evaluate the failure management process of the centralized scheme in terms of the overhead injected into the network and analyse the applicability of a distributed approach to managing the process. Analytical models are developed for centralized and distributed approaches. Their behaviour are compared in order to evaluate whether the distributed scheme can improve the fault management process, in terms of reducing server load and generating better scalability.Proporcionar Calidad de Servicio (QoS) en sistemas de Vídeo bajo Demanda (VoD) es un problema desafiador. En este artículo, analizamos la tolerancia a fallos en un esquema de envío de informaciones, basado en comunicaciones multicast y colaboraciones P2P, denominado PCM/MCDB [13]. El esquema descentraliza el proceso de envío de información entre los clientes y escala las prestaciones del servidor de VoD. PCM/MCDB sincroniza un grupo de clientes con objeto de crear canales de redes locales para reemplazar canales multicast en curso del servidor. La aplicación del paradigma P2P supone cómo afrontar el problema de la conexión y desconexión de clientes del sistema. Para resolver este problema, un mecanismo centralizado es capaz de reemplazar el cliente fallido. En el trabajo evaluamos el proceso de gestión de fallos del esquema centralizado en términos del flujo de informaciones insertado en la red y analizamos la aplicabilidad de un esquema distribuido para el proceso de gestión. Modelos analíticos son desarrollados para las aproximaciones centralizada y distribuida. Sus comportamientos son comparados con objeto de evaluar si un esquema distribuido puede mejorar el proceso de gestión de fallos desde el punto de vista de reducir la carga del servidor y proporcionar mejor escalabilidad.VIII Workshop de Procesamiento Distribuido y ParaleloRed de Universidades con Carreras en Informática (RedUNCI

Interactivity And User-heterogeneity In On Demand Broadcast Video

Video-On-Demand (VOD) has appeared as an important technology for many multimedia applications such as news on demand, digital libraries, home entertainment, and distance learning. In its simplest form, delivery of a video stream requires a dedicated channel for each video session. This scheme is very expensive and non-scalable. To preserve server bandwidth, many users can share a channel using multicast. Two types of multicast have been considered. In a non-periodic multicast setting, users make video requests to the server; and it serves them according to some scheduling policy. In a periodic broadcast environment, the server does not wait for service requests. It broadcasts a video cyclically, e.g., a new stream of the same video is started every t seconds. Although, this type of approach does not guarantee true VOD, the worst service latency experienced by any client is less than t seconds. A distinct advantage of this approach is that it can serve a very large community of users using minimal server bandwidth. In VOD System it is desirable to provide the user with the video-cassette-recorder-like (VCR) capabilities such as fast-forwarding a video or jumping to a specific frame. This issue in the broadcast framework is addressed, where each video and its interactive version are broadcast repeatedly on the network. Existing techniques rely on data prefetching as the mechanism to provide this functionality. This approach provides limited usability since the prefetching rate cannot keep up with typical fast-forward speeds. In the same environment, end users might have access to different bandwidth capabilities at different times. Current periodic broadcast schemes, do not take advantage of high-bandwidth capabilities, nor do they adapt to the low-bandwidth limitation of the receivers. A heterogeneous technique is presented that can adapt to a range of receiving bandwidth capability. Given a server bandwidth and a range of different client bandwidths, users employing the proposed technique will choose either to use their full reception bandwidth capability and therefore accessing the video at a very short time, or using part or enough reception bandwidth at the expense of a longer access latency