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[purenirvana]

Hi Guys,

Just here again asking for you kind folks to give me some of your invaluable advice! 

As I understand it BT can manually pin or set your SNR margin to a figure they deem suitable, i.e. if you have a line that is constantly unstable they might decide to pin it at 12db for example. Presumambly this means no matter what happens with your line when you resync you will always connect with a 12db SNR. Am I correct so far? 

The reason I ask this is that I have been pushed up to a 15db SNR from my nice 6db due to a lot of power drop outs in my area in very quick succession. This is very annoying as my line was holding a nice 3Mbps profile prior to this and now is down to 1.75Mbps! As we have a lot of power outages where I live I can see it being just my luck that we have another succession of them just as my line returns back to it's usual 6db! So what I'm asking is this, can I ask my ISP to ask BT to pin my line to 6db SNR as the line is capable of holding a reliable connection at this SNR, it's just my electricity supply that is causing the drop outs!! Can BT do this when requested to?

Many thanks in advance for any replies to this matter!

pn 

[kitz]

>> Am I correct so far?

Yes

>> can I ask my ISP to ask BT to pin my line to 6db SNR as the line is capable of holding a reliable connection at this SNR,

It cant be "pinned", but it can be reset.
You can ask for it to be reset, but the answer to 6dB is likely to be a firm no... not from from 15dB.  You may be able to get them to reduce it to 12dB or even 9dB, but they certainly wont go that low.

Even if they do reset it, it will in future be liable to future fluctuations from power cuts etc which will start the cycle off again. :/

The DLM constantly monitors your line.. and if it considers it stable enough it will eventually reduce it back again but this process could take a long time, and like you say if you hit a bad patch then it all goes straight back up again.

What router do you use..  with some routers its possible to at least partially over-ride the settings yourself.

[purenirvana]

Hi kitz,

Thanks so much for your quick reply! 

I am using a Netgear DG834GT. I have already manually telneted it and reduced the target SNR but at 15db margin still can't get it back to the old 3Mbps 

So it seems BT can manually intervene and fix your SNR higher but they won't manually intervene to fix it lower only "reset" it?

Thanks again!

pn

[roseway]

BT don't manually set your target noise margin higher. It's the automatic DLM process which does this when the connection is seen to be unstable. The same process can automatically reduce it when the necessary criteria for stability are met. It's not entirely clear what these criteria are, and reducing the target noise margin will take some weeks even if it happens at all. They can, after some persuasion, reduce the target noise margin or reset it to 6dB, but they don't like doing it, for what are generally quite good reasons - i.e. if the conditions which caused the original instability still exist, then DLM will soon increase the target noise margin again to stabilise the connection.

In reality, your best bet may well be to tweak the target noise margin in the router, and accept that you won't be able to get back all the way to the position you were in before.