Download speed has increased

Speedtest.net and the lusnet speed test both indicate that my broadband download speed is just over 7Mbps, but a few days ago it was at around 6Mbps.

I'm just wondering why the speed has increased - I've had Plusnet BB service on this line for over a year now.

WBC DLM dropped your sync-time margin to 3dB?

In reply to a post by RobertoS:

WBC DLM dropped your sync-time margin to 3dB?

I don't have any previous figures to compare with, but from my router's ADSL status parameters page:
SNR Margin(Upstream) 23.6
SNR Margin(Downstream) 2.7
Line Attenuation(Upstream) 20.9
Line Attenuation(Downstream) 42.5

Are you referring to the SNR Margin (downstream)?

Yes.

That can make over 1.2Mbps difference in the connection speed, (sync/bandwidth). 1Mbps sync gives probably about 800Mbps actual download.

This might be a dumb question, but why would the SNR have dropped?

In reply to a post by joconnell:

This might be a dumb question, but why would the SNR have dropped?

Not a dumb question, but why would it have dropped to 3db?

Because on WBC (21CN) connections the DLM has been modified in the last few months to reduce the default 6dB to 3dB on stable low-error lines, in the same way as it has always raised it from 6dB to 9, 12 or 15dB on ones with problems.

This has not been done on the DLM for the old IPStream/IPSC (20CN) connections. IIRC you were recently moved from 20CN to 21CN?

It's now dropped to 2.2

The noise margin is set to a particular value in the system, to be applied at the time you connect. After that, it varies 24/7 because the "noise" around varies all the time.

I've got this description of what it's all about and how it works. See also the BT IP Profile and DLM pages.