SNR Margin Adjustment

[#1]

Since being on broardband - few years now - my downstream SNR margin, as reported by my router, has always been around 12. This remained the case having been transferred to ADSL2+ at the end of April. A few days ago I found how to adjust this figure on my Belkin F5D7633 router and it is now just over 6 resulting in a significant speed increase. So far the connection seems stable with no re-syncs since adjustment was made 3 days ago and download speed has risen from 6500 to 9400 as measured by PN speed tester.
So my question is: will the exchange equipment ever change the SNR margin (which it never did for me) or does this have to be done by the user?

[#2]

Others posting in this forum have shown the 21CN DLM manages SNR margins quite aggressively and can react initially to changed conditions (downstream and upstream) within 14 days, making further adjustments within days of the first change.
Making changes behind the DLM's back seems to confuse it and can lead to unwanted behaviour - the SNR margin heading upwards, but it will be interesting to see if that is what happens following your endeavours.

[#3]

Its now a week since I adjusted the router SNR margin. Yesterday and today it seems that it re-synced at a minute or two after 8am. Both time it retained rates well above 11,000 and so my BT/PN profile continues at 10,000. Download speedtest results remain consistent at about 9,500. Will update in about a week or if something significant occurs.

[#4]

Good
That sounds promising.

[#5]

Another update. About a week ago I lost the ability to communicate with my router using IE8 although I could still get a telnet connection. Did hard reboot of router (power off/on) and fiddled with SNR margin to lower it to a target of 6. This caused the rate to fluctuate over the nex day or so and ith got down to 3 or lower. This was not liked by the DSLAM (?) and it ramped SNR way back up and resulting sync was 7000+ and profile of 6000. I again played with SNR which achieved sync of 10000+ and profile of 9000. A few days later sync reset itself to 11585 with lowering of SNR to 6ish and yesterday profile caught up to 10000 automatically.
What I'm not sure of is how IE8 lost contact with router because I would have preffered to have left things alone to avoid upsetting what was seeming a fairly stable setting.

[#6]

Hopefully James will see this...
My noise margin was stable for months at 6dB.
For some reason (No resyncs etc) BT put this up to 9dB
The recent thunderstorms yesterday caused a further uplift to 12dB - even though it didn't quite loose sync during them.
Please could I ask Plusnet to request a target noise margin of 6dB again from BT?
I'm asking here, because no response (at all) occured when I tried raising tickets on the 9dB issue (on both occasions).

[#7]

We're unable to request SNR changes on ADSL2+ because of the way that the DLM works.
After about 3 days (after the thunderstorms), I would expect a drop.

[#8]

I think (now) 13+dB margin increase to be quite an increase over 9dB - not a drop.
The only thing that has dropped is the sync speed.
PN have succesfully requested BT to reduce target noise margins in the past.

[#9]

We haven't on ADSL2+ as far as I know.  The DLM is meant to retrain at a lower SNR if the line is stable.

[#10]

You have before on ADSL2... I asked for 9db on my line as it either tries 6db or 12db (or more). Never anything between.
Lasted about 48hr before DLM decided it knew better. 9db was great; stable at 23500. Now down to 15000 which I suppose is better than the 8000 it was before.

[#11]

I'm bumping along at 4.5Mbps at 13dB margin.
Best ever was about 7Mbps - all on 21CN!!!!!
I'm only 2Km from the exchange.
It looks like a job for DMT - pathetic isn't it?

[#12]

Quote from: jamesd

You have before on ADSL2... I asked for 9db on my line as it either tries 6db or 12db (or more). Never anything between. Lasted about 48hr before DLM decided it knew better. 9db was great; stable at 23500. Now down to 15000 which I suppose is better than the 8000 it was before.

Our was lowered by you too, after a lot of testing and investigation of the connection. Take a look at ticket ID: 28464949
It was first changed down to 9db by BT on 20th April and then went back up to 15db, eventually being reinstated at 9db early in May. Following a recent power cut and subsequent resynch, it's now down to around 6db, which is where it was with ADSL Max!

[#13]

Hi
I my ticket - PN are going to request a lower SNR or 6db as the DLM thinks 15db is best.  Strange on the ADSLmax the DLM thinks 6db is best! 
Phil