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Optimizing Xfer speed with limited bandwidth (dialup, slow DSL, EDGE)


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I found that the setup instructions aren't very good for slow DSL (or dialup, EDGE, etc). Here are some useful changes.

1. Don't use an experiment to determine bandwidth. You are likely to get lousy results. Use the bandwidth on your connection. On dialup, 6K is right. On slow DSL and EDGE, 10-30 is good. (Note that speeds are in kilobits per second (kilobaud), not kilobytes. You will still need to divide by 8.) Set the maximum to a value that makes for a convenient scale on the Detailed Info speed graph.

2. Start the upload speed at 50% of theoretic max. Once you see an upload start, watch what happens to the download when the upload approaches its limit. If the download starts to oscillate, knock another 1K off the upload limit. I found that 50% is always low enough, but 75% will not be. DO NOT SET THE VALUE TOO LOW. Too low, and the max download value will also be reduced.

In the BitTorrent preferences:

3. Turn off DHT.

Enable it only for new torrents. It is eating a steady 0.3-0.5Kbyte/second.

4. Turn on encryption, with FORCE and disable legacy.

This will reduce the number of accessible peers, but the chances are, the peers that you disable are ones that are being throttled by at least one of the ISPs in the connection. Each throttled connection cuts throughput by A LOT. (It doesn't matter so much for a high-bandwidth network, because other peers are more able to take up the slack.)

5. Set the max number of uploads a little higher than the default. It is unnecessarily conservative.

6. Watch the speed graph for a while. The upload speed should drop to 0 (not to ~0.4) when it is idle, and the download speed should not show sympathetic oscillation with when upload speed is at or near its limit. (There will be a lot of jitter, but no approximately periodic waves.)

7. Finally, if the number of peers you find is too small to keep your connection saturated, turn on DHT briefly, and turn off FORCED encryption. (This is very unlikely, unless you are using a private net or a really unpopular torrent.)

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If by EDGE you mean cellular network you're lucky you get any bandwidth on those per-byte plans.

? What does scale have to do with it. The graph under the Speed tab has 4 subdivisions. Setting it for nice round numbers does not matter if you can only sustain 18 upload without dropping your connection. Setting it to 20 would cause frequent packet loss.

2 is unnecessary when using the Speed Guide.

3 is subjective. Many people including those with quotas would already turn this off because DHT can use something like 4 GiB / mo. I don't recall exact bandwidth anymore.

4 depends on ISP interference. Encryption does not solve shaping profiles. On ISPs which care they use DPI anyway which still shapes traffic. It's up to the user to choose whether to connect to unencrypted peers.

5 ... UPLOAD / (SLOTS * TORRENTS) should not be below 3 for efficiency sake, and NEVER below 1 (the hallmark of badly configured clients) for tcp protocol sake. More is better, as long as it's the same across all torrents. I use 20 peers per torrent with 4 slots per torrent and 4 torrents for .5Mbit upload. Depending if I want to initial seed faster I stop some other torrents. The low peers per torrent allows ALL peers I'm connected to to get a slot within the 5 minute default disconnect window.

6 sine waves are not really something one can fix as that's sign of packet / connection mangling

7 swarm size is more important, i.e. keep DHT on for dead tracker torrents or torrents which you know are old/niche/useful in your opinion.

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Even many ISPs that don't do Deep Packet Inspection (DPI) may throttle ANY traffic they don't recognize. Rogers Cable in Canada is the best example of this.

Many interfere with uploading and seeding. ComCast Cable in USA is a good example of this.

Some interfere heavily with everything. TalkTalk or Tiscali in Europe are good examples of that. :P

Some cripple out-of-country or outside-of-ISP traffic, regardless of nature or type. SingTel in Singapore does that.

Against some "hostile" ISPs, encryption may or may not help. Sometimes non-encrypted traffic gets some (additional) speed...more than without it.

High connection rates (half open rate) and obvious listening port with 40+ connections to that 1 port...pretty obvious to ISPs that care to look.

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