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Pointless SN Margin Changes That Only Makes Things Worse

Community Veteran
Posts: 5,582
Thanks: 722
Fixes: 1
Registered: 23-09-2010

Pointless SN Margin Changes That Only Makes Things Worse

I currently have a good stable connection. Stays connected for weeks. It would stay connected for months if it wasn't for nuisance SN Margin changes made by the mindless DLM in its fruitless search going round and round trying to "improve" things.
With a SN Margin of 6 I get a connection speed of 6.5-7.0 which works well. The only problem is the DLM works, on my line, towards a base of 3 (even though there is a swing of about 4).
So this is what usually happens. On a SN Margin 6 with a reasonable error rate everything is fine. After being up 20-30 days the line will drop as it gets reset to 3. Error rate goes up by a factor of ten plus and line will also drop in the evening due to the swing. This will happen a couple of times, or I will drop it on purpose, until it goes back to 6. Then the roundabout starts again.
It's a nuisance when this happens as sometimes I over shoot the mark and it goes to 9 (but it doesn't take long to drop back). Surely there must be an easy way to stop this pointless toing and froing.
8 REPLIES
jojopillo
Grafter
Posts: 9,786
Registered: 16-06-2010

Re: Pointless SN Margin Changes That Only Makes Things Worse

Hi billnotben,
I'll set it to 6dB now and see if there's anything I can do to stabilise it.
Jojo Smiley
Community Veteran
Posts: 5,582
Thanks: 722
Fixes: 1
Registered: 23-09-2010

Re: Pointless SN Margin Changes That Only Makes Things Worse

Is there any way it can be permanently set to always restart at 6?
jojopillo
Grafter
Posts: 9,786
Registered: 16-06-2010

Re: Pointless SN Margin Changes That Only Makes Things Worse

Hi billnotben,
Yes, but it's very difficult and something that is only possible via the faults process. What I have done may help though.
Jojo Smiley
Community Veteran
Posts: 5,582
Thanks: 722
Fixes: 1
Registered: 23-09-2010

Re: Pointless SN Margin Changes That Only Makes Things Worse

Thanks Joanne, I'll see how it goes now.
There was a time when I was lucky to hold a connection for more than three days but having FEC on permanently fixed that.
I guess stability can have its own (minor) problems.
Community Veteran
Posts: 6,313
Thanks: 86
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Registered: 08-01-2008

Re: Pointless SN Margin Changes That Only Makes Things Worse

Whetever happened after this trial: http://community.plus.net/forum/index.php/topic,82898.0.html ?
For my line, it proved the best thing since sliced bread (and stayed that way until I switched to FTTC).
Call me 'w23'
At any given moment in the universe many things happen. Coincidence is a matter of how close these events are in space, time and relationship.
Opinions expressed in forum posts are those of the poster, others may have different views.
jojopillo
Grafter
Posts: 9,786
Registered: 16-06-2010

Re: Pointless SN Margin Changes That Only Makes Things Worse

Hi walker23,
Sadly it was just a trial. We do have more control over what we can set profiles to but they are only soft changes, so any instability will cause the DLM to kick in. I wish there was a way for us to hard fix profiles but nowadays we have to do it via the fault process.
Jojo Smiley
Community Veteran
Posts: 6,313
Thanks: 86
Fixes: 3
Registered: 08-01-2008

Re: Pointless SN Margin Changes That Only Makes Things Worse

Thanks Jo,
I recall virtually everone on that trial being pretty pleased with the results so I'd have thought it was about as successful as any trial could be, what a pity the success didn't translate into what it could have been.
In my case, I had intermittent instability (suspected REIN issue on a semi-predictable basis) and being able to 'fix' the line parameters meant that I could always return to normal service rather than being banded on a low speed because the line played up 'some of the time'.
I guess 'they' had their reasons for not adopting this system.
Call me 'w23'
At any given moment in the universe many things happen. Coincidence is a matter of how close these events are in space, time and relationship.
Opinions expressed in forum posts are those of the poster, others may have different views.
jojopillo
Grafter
Posts: 9,786
Registered: 16-06-2010

Re: Pointless SN Margin Changes That Only Makes Things Worse

I think the main thing that did was to stop unnecessary banding and low IP profiles, but since the change to bRAS quantisation profiles are applies instantly, so there's no worries about getting stuck with a low profile for 3 days or so Smiley