Despite the availability of video-on-demand (VoD) services in a number of cities around the world, the large-scale deployment of VoD services has not been widely explored due to economic constraints. The high complexity founded in these systems makes the design process very difficult.This study presents a VoD system design for a highspeed metropolitan network, based on ATM technology, located in Brazil. To accomplish this goal, we have utilized our own simulation-based tool for VoD design called VODSim. This tool allows VoD research on any VoD platform, simulating the complete flow path followed by requests from clients to servers passing through the network infrastructure, allowing the configuration and tuning of multiple system parameters. Using VODSim, we analyse possible VoD architectures for the proposal environment (i.e. Centralized-server, Independent-servers, One-level-proxies and Distributedservers), studying key-parameters that have influence in system design.Experimental results show that Distributed-server architecture is the one that adjusts better to the analyzed infrastructure, improving streaming capacity by 16%, 25% and 28% more than One-level-proxies, Centralized and Independent-servers respectively. Taking in account future growth in VoD system, the Distributed-server even provides an unlimited scalability through new local network incorporation and using P2P techniques.
Most of the Video on Demand (VoD) systems were designed to work in dedicated networks. However, there are some approaches that provide VoD service in nondedicated and best effort networks, but they adapt the media's quality according to the available network bandwidth. Our research activities focus on VoD systems with high quality service on nondedicated networks. Currently, we have designed and developed, to integrate in the VoD server, a network manager that provides: total network control, network state information, and adaptation of the transmission rate in a TCP-Friendly way. The present work describes this network manager, named Network Traffic Scheduler (NTS), which incorporates a congestion control algorithm named "Enhanced Rate Adaptation Protocol" (ERAP). ERAP is an optimization of the well-known protocol denominated "Rate Adaptation Protocol" (RAP). Maintaining the basic behavior of RAP, ERAP increases the efficiency of the NTS by reducing the resources usage (of the server and the network). These components has been extensively evaluated by simulations and real tests in which the resource consumption and the performance were measured. This paper presents the advantages of using ERAP instead of RAP in a VoD server, and its viability to be integrated within the NTS in a VoD server on nondedicated networks.
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