why ADSL has a dependancy between upstream and downstream bandwidth?

[Konstantin Dunaev]

Hi,

I've found very interesting point with my ADSL connection (Germany), my download speed depends on how mach bandwidth I gives to the upstream:

without upload ftp:

10485760 bytes received in 44,63Seconds 234,93Kbytes/sec.

Upload limited on 8kB/s

ftp: 10485760 bytes received in 43,63Seconds 240,32Kbytes/sec.

Upload limited on 12kB/s

ftp: 10485760 bytes received in 44,39Seconds 236,20Kbytes/sec.

Upload limited 16kB/s

ftp: 10485760 bytes received in 65,09Seconds 161,09Kbytes/sec.

Upload limited 20kB/s

ftp: 10485760 bytes received in 86,02Seconds 121,89Kbytes/sec.

Upload limited 24kB/s

ftp: 10485760 bytes received in 90,73Seconds 115,57Kbytes/sec.

Upload isn't limited (~24kB/s)

ftp: 10485760 bytes received in 265,80Seconds 39,45Kbytes/sec.

Where could be the problem?

Best

Konstantin

[paul.werner]

See if either of these help (hint - the answer is in how TCP works):

http://homepage.ntlworld.com/robin.d.h.walker/cmtips/downup.html

http://cable-dsl.home.att.net/#Asymmetry

Don't feel too bad about it, at least you can troubleshoot, diagnose the problem and emplace a workaround. My ISP here in germany uses a slightly different technique for DSL. I like to refer to it as randomized unfair queueing:-) It works something like this.

1. You sign up for service.

2. They turn service on at rated speed (in my case 1.5Mbps).

3. They let it run a month or three at rated speed.

4. They sign on new customers (not you of course).

5. They sign on new customers at rated speed (whatever that is).

6. Network congestion occurs at the upstream connection beyond the DSLAM.

7. Rate/bandwidth limiters get placed on existing customers.

8. Some customers complain.

9. Complaining customers *magically* see download speeds increase.

10. Non-complaining customers deal with slower speeds as a matter of Internet life.

pw