In reply to a post by StephenTodd:

might it be the sync speed at 0 dB SNR margin ? That's my guess.
Mine is quite often below my sync speed What snr is it quoting when it is below sync speed?

I guess that at sync time max was above the sync; as time went on max wanders below sync, but the line quality is good enough it still manages to keep the connection.

I think it is the max speed estimated by the modem is based on the target SNRM (ie 6dB), and assumes that no FEC or interleaving is going on.

My line started with max attainable of 90Mbps and synced at 80 with a SNR higher than 6dB (not sure exactly what, though). As the max attainable dropped (I'm presuming because crosstalk has increased) so did the SNR value:
85Mbps - 7.3dB (Feb 2012)
84Mbps - 7.1dB (Mar 2012)
83Mbps - 6.9dB (Jun 2012)
82Mbps - 6.6dB (Jul 2012)

I don't have the later figures to hand, but it was very close to 6dB on the last resync (Dec 2012).

Right now, the max attainable is 72Mbps and the SNR is running at around 3.2dB. I don't want to resync it...

If the actual, current, SNR has reduced below this level, then noise levels have increased since the last sync.

That's a bit of a worry. The uptime is 16 days at the moment but I did think it had retained that SNR over a 40min power cut that occurred 16 days ago.

Has anybody successfully used the SNR tweak available with DSLstats?

I've tried tweaking SNRM via telnet, which is all any of the tools use. It doesn't work. Gives wierd results. That isn't surprising, as sync speed is not set directly using it in the way it is on ADSLx.

Openreach SIN 498 FTTC DLM section specifically says it should not be tweaked. (At the time I tried, it didn't).

Note : It is the DLM system that sets the line profile, and this should not be interfered with by CPs/users setting rates, SNR margins etc. at the modem.

In reply to a post by WWWombat:

There is no relationship between IP Profile and max downstream rate.

The relationship is with the sync speed.

Using an unlocked HG612 modem, we see this info:-

Max: Upstream rate = 4851 Kbps, Downstream rate = 21488 Kbps
Path: 0, Upstream rate = 4859 Kbps, Downstream rate = 20764 Kbps


Max: is the theoretical speed & actual Sync speed is Path: 0.



From a HG622 modem, we see this:-
Max: Upstream rate = 4940 Kbps, Downstream rate = 25300 Kbps
Bearer: 0, Upstream rate = 4947 Kbps, Downstream rate = 24894 Kbps

Actual sync speed is Bearer: 0.




IP Profile SHOULD be around 96.79% of sync speed.

Occasionally VDSL2 connections resync too quickly for a PPP session to be initiated & thus the reported IP Profile can remain stuck at a higher or lower level.

A means to refresh the reported IP Profile is to disconnect/reconnect the ROUTER/HUB, not the MODEM as doing it via the ROUTER will not make DLM see it as an 'unstable' connection needing remedial & usually negative action in terms of sync speeds..

what is weird results?

bear in mind the hg612 cannot tweak vdsl snrm.

you need a device that can such as a fritzbox or draytek 2850.

Attempting to tweak settings is against Openreach's specifications.

In reply to a post by Chrysalis:

what is weird results?

The weird results he got when he tweaked the vdsl snrm on his HG612.

I never said it wasnt.

whats your reason for trying to scare people of doing it hmmm.

Edited by Chrysalis (Sat 18-May-13 17:34:53)

the hg612 can only tweak adsl snrm not vdsl snrm.

I don't know about the ADSLx aspect. I said I got wierd results when I tried it on VDSL2. I meant "I got wierd results when I tried it on VDSL2". Strange variations in sync and other stats. I don't remember as it was something like a year ago and clearly an unwise and useless thing to be doing.