Short Bytes: A new BitTorrent feature has been announced which is designed with a goal of maintaining a sharing ratio of 2:1 in a swarm. The confusing Altruistic Mode feature will make sure that your share more and download less.
The Altruistic Mode is designed to make sure that your sharing ratio remains more than 2:1 i.e. while downloading a torrent, you upload 2Gb data for every 1GB download. Many of the loyal torrent users seed to benefit the network and the download speed of other users. But BitTorrent says that this does not guarantee a 2:1 ratio. That’s where the Altruistic Mode comes handy and helps a swarm. “Because of this Altruistic Mode downloads will often never complete,” writes Bram Cohen, the creator of the BitTorrent protocol.
In a blog post, Cohen explains various aspects of the mode depending on the normal download mode:
- If Download Mode would upload at a greater than 2:1 ratio then an Altruistic Mode peer will have very similar behavior.
- If Download Mode would upload at a ratio between 2:1 and 1:1 then Altruistic Mode will upload less and download a lot less than Download Mode would, resulting in a 2:1 upload to download ratio.
- If Download Mode would upload at a ratio of less than 1:1 then Altruistic Mode will do very little uploading or downloading.
“What Altruistic Mode approximately does is that as long as there are two peers which are interested it keeps downloading, because for each new piece it downloads it can upload to two peers, but if there is only one interested peer it stops downloading because the peer can only get at best the same amount of upload as download and possibly be a net drain in that case.”
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Cohen considers 2:1 as an ideal ratio considering the complexities and the possibility that a ratio higher than 2:1 could harm the peers and a complete copy of the file may not exist. For now, Altruistic Mode is an experiment.
“We are hoping that it’s sufficiently understandable and useful that users embrace it and that we don’t get too many complaints about downloads never finishing or that the upload ratio remains unchanged, which as explained above are completely expected behaviors under some conditions.”
Given the fact that the downloads may never complete, BitTorrent’s ambitious feature may not be welcomed by many users. However, if Altruistic mode becomes a success Cohen has further plans.
Cohen concludes, “If this goes well we may roll out another feature in the future where a peer starts out in Altruistic Mode and later switches to regular Download Mode, which would not change the upload ratio significantly but would help other peers download faster at the beginning, so peers who want to get a complete file eventually but aren’t in a rush can allow other peers who care about getting it sooner to finish first.”
The Altruistic Mode is available on BitTorrent 7.9.9 and uTorrent 3.4.9. And it won’t be turned on by default in the clients.
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