| Περίληψη: | The purpose of this dissertation is the scalable bandwidth monitoring and control of peer to peer live video streaming systems in order to guarantee the complete and on time video distribution. For this reason, designed, developed and implemented a comprehensive solution that handles the problem of deficit or surplus of bandwidth resources in a peer to peer live streaming system.The major requirements for a P2P live video streaming application can be summarized to the followings: a) efficiency of the video distribution in terms of utilization of peers’ upload bandwidth, in order to minimize any additional bandwidth contributed by a set of media servers (cloud) and/or maximize the playback rate of the video which the system is able to deliver, b) stability of the system which is defined as the uninterrupted and complete stream delivery in each participating peer in the presence of dynamic conditions, c) scalability which is determined by the amount of resources (bandwidth, storage, processing overhead) that the media server/cloud, which manages the system, has to contribute in order to sustain the uninterrupted delivery of the stream, as the number of participating peers grows. There are two strategies in order to adapt the P2P live streaming service to the dynamic upload bandwidth conditions of participating peers. The first is to dynamically adapt the playback rate according to the existing upload bandwidth of participating peers, while the second is to dynamically allocate upload bandwidth from auxiliary sources (e.g. clouds). The selection of a strategy has to do with the QoE that participating users desire and the business model of the service provider. The proposed system is able to guarantee the complete and on time video distribution to every participating peer based on the two aforementioned strategies. The contribution of this dissertation is summarized to the development of these strategies with respect to the aforementioned P2P live streaming requirements. In the first control strategy that has been developed, it is proposed an architecture which adapts dynamically the video playback rate according to the existing upload bandwidth of participating peers. In the second control strategy that is developed, it is proposed an architecture that dynamically calculates and allocates/releases from/to auxiliary sources (e.g. clouds) the amount of deficit/surplus of bandwidth which is required for the video distribution with respect to the video playback rate and system's resources. In the third strategy is proposed a live streaming architecture that with a not only scalable but also in a totally distributed way, is able to determine dynamically the required bandwidth (hence the equivalent in surplus/deficit) for the video distribution. At the same time if necessary subsidiary help, it will no longer come from a central source (e.g. cloud) but from other (additional and/ or unused) peers.
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