I've had a quick look and caching seems to only be usefulif you are an ISP
You (the ISP) hold popular p2p files on a local server so your customers can retrieve the file without you having to pay for international traffic thus improving margins.
I don't really think mean this. An ISP shouldn't be asking these questions on Microsuck
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Are you thinking more of a p2p seed server ? That would be pretty simple to setup, I assume you have a spare machine for it ?
which p2p network are you thinking of (BitTorrent ?) because that will decide which application to use.