| Summary: | 碩士 === 國立清華大學 === 資訊系統與應用研究所 === 93 === Video-on-Demand (VoD) services using peer-to-peer (P2P) technologies benefit by balancing load among clients and maximizing their bandwidth utilization to reduce the burden on central video servers. In this thesis, we propose a novel architecture to construct a fully decentralized P2P overlay network for VoD streaming based on a multi-overlay concept. The architecture is referred to as MegaDrop.
Conventional P2P techniques for realizing VoD services only stream media data between active peers in the same VoD session. However, they never consider those inactive peers that have left the session but may still hold partial media content in their local storage. Thus, our architecture takes both kinds of peers into consideration, providing mechanisms for discovering all potential nodes that may possess the desired media objects.
By taking advantage of the large storage and the powerful processing capability in current client-side devices, the architecture distributes media among nodes, allows any peer to search for a specific media object over the entire P2P network as soon as possible, and streams the media object from a group of the nodes that have either the entirety or only parts of the media content. There is no central resource allocation in the streaming session at all, thereby avoiding the single point of failure.
We employed a layering strategy further dividing the architecture into four major tiers: Peer Discovery Layer (PDL), Content Lookup Layer (CLL), Media Streaming Layer (MSL), and Playback Control Layer (PCL). PDL takes charge of discovering peers, which constructs the first overlay network. CLL generates a unique identifier for a media object and provides content matching capability. MSL performs actual media transmission between peers, which constructs the second overlay network. PCL interacts with end users, letting them execute control operations.
The evaluation of the resultant system revealed that our architecture is particularly efficient for huge media delivery and multi-user streaming session. The more peers participating in a session, the more aggregate bandwidth peers can obtain. All of the peers thereby gain a shorter average streaming time. Furthermore, our system provides not only VoD streaming but also file sharing services.
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