Bram Cohen (![[info]](http://l-stat.livejournal.com/img/userinfo.gif){kind=small} bramcohen) wrote,@ 2005-03-23 06:57:00 |
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Improving 'ratios'
My last entry about the problems in upload/download ratio generated a lot badly thought out wannabe developer comments. Something about BitTorrent attracts a lot of people who would like to do software but can't.
Anyhow, the key thing everyone seems to have missed is that I didn't say that keeping track of upload vs. download per downloader was a bad idea, just that doing so via fixed ratios results in severe misbehavior when there's an excess number of seeds.
It's quite simple to improve ratio measurement. When a client reports new downloads to the tracker, the tracker can multiply the amount by (number of current peers total - number of current seeds) / (number of current peers total) and add that to the 'total downloaded'. This results in most people having a 'ratio' of more than 1, but that isn't actually a problem unless you're more interested in mathematical purity than practical behavior.
It would be interesting to have a 'help seed' mode for the client, where it downloads only as much as it needs to actively upload. That way new people entering a torrent only wanting to seed could reliably help rather than hurt, since frequently it's difficult to upload a complete copy, and the downloader always downloads a complete copy.
My last entry about the problems in upload/download ratio generated a lot badly thought out wannabe developer comments. Something about BitTorrent attracts a lot of people who would like to do software but can't.
Anyhow, the key thing everyone seems to have missed is that I didn't say that keeping track of upload vs. download per downloader was a bad idea, just that doing so via fixed ratios results in severe misbehavior when there's an excess number of seeds.
It's quite simple to improve ratio measurement. When a client reports new downloads to the tracker, the tracker can multiply the amount by (number of current peers total - number of current seeds) / (number of current peers total) and add that to the 'total downloaded'. This results in most people having a 'ratio' of more than 1, but that isn't actually a problem unless you're more interested in mathematical purity than practical behavior.
It would be interesting to have a 'help seed' mode for the client, where it downloads only as much as it needs to actively upload. That way new people entering a torrent only wanting to seed could reliably help rather than hurt, since frequently it's difficult to upload a complete copy, and the downloader always downloads a complete copy.
