Under flash-crowd conditions, a large number of users wish to retrieve a small set of files from a server over a short period of time. Although many of these requests are intercepted and satisfied by caching mechanisms, the remaining ones must be satisfied directly by the server. Unfortunately, a sufficient number of these requests exist to cause bottlenecks near the server. Under these conditions, the users who initiate the requests are in a unique position to benefit enormously by sharing retrieved files. This project explores protocols and architectures that provide the proper incentives for users to cooperate under such conditions. It is based on a new paradigm for Internet access called pseudo-serving, in which a super-server grants a user a referral to where a copy of the requested file may be obtained if she agrees to serve some number of other users for a period of time specified in a contract.
In this proposed project we will investigate various issues that must be resolved in order to make pseudo-serving an effective tool for dissipating flash-crowds on the Internet. We have already demonstrated the effectiveness of pseudo-serving to dramatically reduce the download time of large files. But further work needs to be done to investigate the pseudo-serving under more realistic scenarios. Towards this end, we will address the following four issues. The first is the acceptability of the contract to the user. The second is the ability of the super-server to set contracts that account for the physical distribution of sources of the requests. The third is security and various approaches in dealing with contract breaches. And the fourth is strategies for integrating pseudo-serving into various caching policies. Because pseudo-serving and caching compliment each other, they can be combined to deliver better access to information.
The impact of this research extends beyond realizing an end-to-end solution to the flash-crowd problem. Because preferential access is given to users who contribute to the resources they consume, pseudo-serving can be viewed as a form of bartering; users barter their local storage space and network connectivity in exchange for speedy access to requested data. This exchange is unique in that it simultaneously brings the cost of a scarce resource to the user and adds to this resource as necessary to satisfy demand. The insights gained from this research would provide valuable experience in resource sharing at an inter-organizational level in a networked environment.
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