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Are Upload and Download speeds directly related?


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Does anyone know if upload and download speeds are directely related? I did a little test to see and this is what I got.

single 700M file seeding (no downloading on it) and a single 500M file downloading (no uploading on it)

Here are the results when I change my upload speed only:

300kB/s down

2kB/s up

150kB/s down

10kB/s up

75kB/s down

50kB/s up

You can see that as I modifed the upload speeds, the download speeds were directly affected. This makes me think that if I allow even a single upload at any reasonable upload speed then my download speeds will be cutback drastically. How can uTorrent give me full download speeds while maintaining full upload speeds when working with single torrents? I say 'single torrents' because I don't have this problem with multiple torrents since they all get low download speeds that add up to a high speed. I'm using uTorrent 1.6. I have a 5000/640kbps connection.

Any ideas?

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The effect you're experiencing is called 'bottlenecking' and occurs no matter what program you use. If you had an HTTP download going at 300KB/s, something like, say, an FTP upload wouldn't be able to exceed 2KB/s.

A general rule of thumb to follow is to set your upload limit to 80% your maximum. Please refer to the FAQ and the speed guide for further information.

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To test the bottleneck theory I downloaded a file from one server via http and uploaded one file to a different server via ftp. Here are the results:

70kB/s upload

215kB/s download

these are simultaneous speeds. so this pretty much nullifies the bottleneck theory. what else could cause this?

Oh, and here's my utorrent settings:

global max num of connections: 375

max num of connected peers per torrent: 100

num of upload slots per torrent: 4

use additional if < 90%: checked

max num of active torrents: 20

max num of active downloads: 10

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375 global connections is way too many. You generally only need 50 or less peers per torrent, and all those extra peers generates a lot more TCP and BT protocol overhead than if you had less peers. Toning those settings down should help a lot.

Try 180 max connections and 60 max per torrent.

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That only eliminates the bottleneck theory based on raw bandwidth useage, not lots of connections at once causing a bottleneck.

I'd say if you're regularly running more than 10 torrents at once, then you need to reduce connections per torrent to only 20-40.

Hopefully, you can disable DHT and UPnP. (You use manual port-forwarding, right?)

Also, what's your half-open and bt.connect_speed values in µTorrent? Setting them high tends to put a very heavy load on networking hardware and firewall software.

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yeah, i did follow the speed guide. :(

ok, i've changed to 180max and 40 max/torrent

DHT and UPnP are disabled

half-open is 8 and bt.connect_speed is 20

i've now tested it with 2 max global and 2 max/torrents:

i got full speed on the download when i had the upload off, but when i turned on the upload and got a peer attached theni dropped back down to the usual slow download speed.

that was with me being the only connection downloading and only having one peer uploading from me. that makes me think it can't the number of connections since i barely had any available (2).

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D-Link DGL-4300. nothing done to affect the utorrent traffic.

do others get the same results when they have one upload and one download simultaneously?

ok. got a little more info.

i did a 1 to 1 test from a machine outside my network to a machine inside my network.

when i have a single download going, i get full speed.

when i have a single upload going, i get full speed.

when i have a download and upload going simultaneously i get higher download speeds when i have lower upload speeds.

and the speed tradeoff is not dependent on the max speed available in any ways.

if i set upload to 80kB max but only use 2kB then i get a high download speed, but

if i set upload to 80kB max and use 60kB then i get a low download speed.

why would uTorrent limit my download speed purely based on the upload speed in use? That seems like a big waste of bandwidth. If i can max my download at appx 600kB/s and my upload at appx 80kB/s then i feel that utorrent should at least be able to attain those speeds in an optimal condition. I know that every download uses a little bit of upload, and visa versa, but it would not affect my bandwidth in the drastic way that i'm seeing. Getting appx 50kB up and appx 50kB down is quite rediculous. That's just nowhere near what my connection is capable of.

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Sounds almost like your connection as acting like it's half-duplex, and not µTorrent's fault.

Half-duplex means your connection can only upload OR download at any given instant...but it can alternate between the 2 per second so you can get both download and upload speeds. The problem is, you'll take a HUGE speed hit on download while uploading even 25% of your max. And at >50% upload max, your download speed might only run at 10%.

Maybe it's just software problems? -- as I imagine poorly-written software firewalls would cause this behavior too!

Lastly, how is your D-Link router port-forwarded? If it's done using DMZ, that's really, really BAD. If it's UPnP, on D-Link that's almost as bad. There is also multiple ways to port-forward beyond that...not all are equally reliable.

(VPN, Virtual server, port triggers, port-forwarding, etc...different names, same results, but often different methods!)

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I am infact using the DMZ on the router. What is it that makes that bad? And I want to think that the routher is behaving properly since I can HTTP in and FTP out simultaneously and still get full bandwidth on both.

i'm gonna go try some speed tests outside my network. maybe this can tell me if it's the router for sure.

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Firstly, your computer being in DMZ on a router means...NO firewalling of the internet to your computer. You only need to open 1 incoming port for µTorrent to work properly, but DMZ opens 65000+. This is bad because any vulnerability your computer might have is exposed to the internet.

Secondly, D-Link routers are notorious for corrupting data when in DMZ mode. In short, DMZ mode doesn't even work right -- and that alone can explain ALL the problems you're having so far.

I hate to say it, but you may want to get the latest versions of SpyBot Seek and Destroy, Ad Aware, and Trend Housecall AV. They will likely find anything that slipped in.

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I appreciate the concern :), but i need several open for other apps i run. So i free them all and use a local firewall to pick them apart. After a few more different configurations I'm convinced that it's the router now. I think i'm gonna play with it's settings and see what i can find. Thanks for all the help, switeck. it's nice to see people who care enough to help others. :D

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