Abstract. Each peer in a peer-to-peer network, by definition, is both a consumer and a provider of the service. As a consumer, a peer wants to obtain its objects of interest as quickly as possible. However, as a service provider, the peer wants to serve no more than an equitable portion of the total workload. Our first observation in this paper is that if one satisfies the latter criterion of fairness in workload distribution, then one also minimizes the average download time when the delay at the server is convex in the utilization factor of the server. We had previously observed that controlled flooding search in unstructured networks is optimized when the number of replicas of a file is proportional to the request rate for that file. Here we show that such a replica distribution also ensures fairness in the workload distribution and, at the same time, minimizes the average download time seen by a download request.
The increasing ease of self-expression and webpublishing has resulted in an explosion in the amount of content being generated in the current Internet. Besides traditional sources such as news portals, regular users are documenting their lives and thoughts and other people are subscribing, downloading and viewing this content. A lot of content therefore is being generated at the edge and consumed by the edge.Traditional client-server architectures are known to be ineffective in handling large correlated bursts of user demands. However, with RSS becoming more popular, such flash crowd scenarios will be more and more commonplace due to automated polling and downloads. Peer to peer protocols such as BitTorrent provide an attractive solution for such scenarios. BitTorrent networks are scalable, and the expected download time is independent of the arrival rate of peers (content consumers).
However, the base performance of a BitTorrent network may not be fast enough from a user or content publisher's perspective. Besides, BitTorrent gives poor results towards the end of a flash crowd when most of the large burst of arrivals have downloaded and left, and there are not too many peers online.We motivate the need for a content delivery network with well connected servers to participate in BitTorrent delivery streams. The servers are dynamically added and function as cushions to handle increase in demand as well as bolster a delivery stream when there is a paucity of users. We analytically model the approach and determine the average download time both in steady state and in the transient state. Our analysis shows that a content delivery provider can provision the deployment of servers on-the-fly based on the arrival rate of peers to provide a certain pre-agreed average download time.
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