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I've read some wikis and pages about TCP congestion avoidance algorithm but I don't sure about the response to this question: What's the best TCP congestion avoidance algorithm to an ADSL2+ connection? Actually I use CUBIC, is it the best option?

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A link that explains what you're talking about will increase your chance of getting a good answer. Two of them would be even better. :-) – Stefano Palazzo Jun 6 '11 at 14:33
It would also be good to describe the reason for your concern -- this might change the recommendations you get. Are you just interested from a theoretical standpoint, trying to insure you have an optimal configuration, or are you seeing particular problems or troublesome behavior? – belacqua Aug 13 '11 at 20:20

Due to bufferbloat on typical consumer ADSL2+ connection the TCP congestion avoidance algorithms do not work at all. If you are suffering from that, this blog posting by Jim Gettys might be helpful. Personally, I apply bandwidth limit on the bulk uploads (scp and torrents, mainly) to not exceed half the stated capacity of my link, and that seems to be sufficient.

If your problem is something else (for example, if you are on the DSLAM side or provide the link further downstream), please give more details.

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Could your MTU be too large? See

An excessive (for your network) MTU will lead to fragmentation, and sending 2 packets along the path for every 1 MTU-sized packet you thought you sent.

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