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Standard User jonstatt
(regular) Thu 03-Mar-11 11:02:36
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Latest SNR DSLAM algorithm?


[link to this post]
 
Last night there was some very strange interference that affected my TV, my Radio and my broadband. I didn't see many reconnects at all, but for whatever reason my SNR has now moved to 9dB from 6dB.

The interference is gone now and of course I want my speed back!

I see conflicting information on the net about whether the latest changes by BTW mean that the SNR will ever go back on its own, or if its now stuck at 9dB permanently without intervention. I also see talk of a 14 day monitoring period, and that being refuted elsewhere.

Does anyone know the latest information on this?


Below are my hub stats. It has only been running for a bit over an hour because I manually reset it to make sure it really was stuck at 9dB. These stats are typical for any time of day though and show the line is clearly capable of more.

Line state Connected
Connection time 0 days, 01:19:56
Downstream 7,136 Kbps
Upstream 448 Kbps


ADSL Settings
VPI/VCI 0/38
Type PPPoA
Modulation G.992.1 Annex A
Latency type Fast
Noise margin (Down/Up) 8.9 dB / 22.0 dB
Line attenuation (Down/Up) 31.4 dB / 19.0 dB
Output power (Down/Up) 10.8 dBm / 1.5 dBm
Loss of Framing (Local/Remote) 0 / 0
Loss of Signal (Local/Remote) 0 / 0
Loss of Power (Local/Remote) 0 / 0
FEC Errors (Down/Up) 0 / 0
CRC Errors (Down/Up) 13 / 1
HEC Errors (Down/Up) 7 / 0
Error Seconds (Local/Remote) 13 / 1

Edited by jonstatt (Thu 03-Mar-11 11:42:54)

Standard User b4dger
(knowledge is power) Thu 03-Mar-11 13:07:45
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Re: Latest SNR DSLAM algorithm?


[re: jonstatt] [link to this post]
 
Unfortunately that's how BT's system works.

A storm, noise interference or just looking at your router in the wrong way can soon push up your Target SNRM in an attempt to stabilise your connection by decreasing your sync frown

If your line remains stable then your TSNRM will automatically reduce to the default 6db and return your normal sync. As you say, 14 days is often mentioned but it's often longer depending on your error levels and which way the wind is blowing!

All you can do is monitor your line and make sure none of your equipment etc. is causing problems...

Standard User RobertoS
(sensei) Thu 03-Mar-11 13:38:33
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Re: Latest SNR DSLAM algorithm?


[re: b4dger] [link to this post]
 
The minimum is 10 days. I reckon above 14 and it isn't going to happen.

Re the question about whether there has been a change, it seems that the DLM on WBC FTTC is quite a different thing, and the one on ADSL2+ randomly breaks.

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - IDNet Home Starter Fibre.


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Standard User yarwell
(sensei) Thu 03-Mar-11 14:10:26
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Re: Latest SNR DSLAM algorithm?


[re: RobertoS] [link to this post]
 
it seems that the DLM on WBC FTTC is quite a different thing

to be pedantic it's Openreach DLM not WBC and it does work differently, using PPP negotiation to hand on the line rate.

Phil

MaxDSL - goes as fast as it can and doesn't read the line checker first.

MaxDSL diagnostics
Are your kids pirates ? Limewire, Bearshare, Kazaa, BitTorrent, eMule are all tools of the trade.
Standard User RobertoS
(sensei) Thu 03-Mar-11 14:17:35
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Re: Latest SNR DSLAM algorithm?


[re: yarwell] [link to this post]
 
In reply to a post by yarwell:
it seems that the DLM on WBC FTTC is quite a different thing

to be pedantic it's Openreach DLM not WBC and it does work differently, using PPP negotiation to hand on the line rate.
That's not pedantic smile.

It's important.

Isn't the ADSLx one BT Wholesale though? Or have I had the wrong impression for years?

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - IDNet Home Starter Fibre.
Standard User yarwell
(sensei) Thu 03-Mar-11 14:44:23
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Re: Latest SNR DSLAM algorithm?


[re: RobertoS] [link to this post]
 
Isn't the ADSLx one BT Wholesale though?

I believe so, they run the exchange DSLAMs and Openreach run the cabinet ones (for which they have a dispensation from OFCOM).

Phil

MaxDSL - goes as fast as it can and doesn't read the line checker first.

MaxDSL diagnostics
Are your kids pirates ? Limewire, Bearshare, Kazaa, BitTorrent, eMule are all tools of the trade.
Standard User RobertoS
(sensei) Thu 03-Mar-11 15:24:31
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Re: Latest SNR DSLAM algorithm?


[re: yarwell] [link to this post]
 
Ah - thanks smile.

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - IDNet Home Starter Fibre.
Standard User b4dger
(knowledge is power) Thu 03-Mar-11 15:32:31
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Re: Latest SNR DSLAM algorithm?


[re: RobertoS] [link to this post]
 
In reply to a post by RobertoS:
The minimum is 10 days. I reckon above 14 and it isn't going to happen.

That's not my experience.

My line has shifted a few times over the years due to line damage and storms.
Often it has been many weeks sometimes a month or two before my TSNRM is reduced.

This will probably be my next problem! frown

Standard User iwish
(committed) Sun 06-Mar-11 20:20:59
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Re: Latest SNR DSLAM algorithm?


[re: b4dger] [link to this post]
 
In reply to a post by b4dger:
In reply to a post by RobertoS:
The minimum is 10 days. I reckon above 14 and it isn't going to happen.

That's not my experience.

My line has shifted a few times over the years due to line damage and storms.
Often it has been many weeks sometimes a month or two before my TSNRM is reduced.

This will probably be my next problem! frown

If that was me i would go jump on that tree until it took the line down
Then call it into to BT
Standard User PiKe
(knowledge is power) Tue 24-May-11 09:12:23
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Re: Latest SNR DSLAM algorithm?


[re: b4dger] [link to this post]
 
In reply to a post by b4dger:
In reply to a post by RobertoS:
The minimum is 10 days. I reckon above 14 and it isn't going to happen.

That's not my experience.

My line has shifted a few times over the years due to line damage and storms.
Often it has been many weeks sometimes a month or two before my TSNRM is reduced.

This will probably be my next problem! frown
Ring openreach and get it sorted.

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Standard User RobertoS
(sensei) Tue 24-May-11 10:16:21
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Re: Latest SNR DSLAM algorithm?


[re: PiKe] [link to this post]
 
In reply to a post by PiKe:
Ring openreach and get it sorted.
Not that simple. See this 23 Feb thread.

Finally dealt with 20 May.

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - IDNet Home Starter Fibre. Live BQM.

"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
Standard User PiKe
(knowledge is power) Tue 24-May-11 10:43:01
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Re: Latest SNR DSLAM algorithm?


[re: RobertoS] [link to this post]
 
I got one sorted within a week.

Click here: http://www.openreach.co.uk/orpg/home/submitFeedback....

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Standard User mixt
(experienced) Tue 24-May-11 21:23:42
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Re: Latest SNR DSLAM algorithm?


[re: jonstatt] [link to this post]
 
*laughs* - yes, well, I would say if you fully understood how BT's DLM works, then you would be famous, as you probably also understand where the universe came from.

My line had a fault until it was fixed (a few weeks back). Broadband was still usable, but I was syncing with a 6db margin most of the time, with loads of FEC errors (I forcefully enabled interleaving, through AA's portal).

Magically one day, the DLM decided to raise me to 9db, slowing my sync speed. I contacted AA who got BT to reset it back to 6db. I also asked if they could set it to 3db, but the guy told me 6 was the lowest they could do, and that this was not fixed as the DLM may reset it again, if it decides to.

The fault got fixed. Amazingly, it now insists on making my modem sync at a 3db margin with a whole 1 mbit more speed. But hang on, I didn't think 3db was a valid target SNR?

In short, God knows how their DLM works - literally. I've given up trying to make any sense of it. As long as it doesn't annoy me and doesn't make completely insane judgements about my line quality and what speed I should be syncing at, I ain't too worried.

Now on <aaisp.net>
Previous ISPs: Virgin Media (50Mb/Cable), Be* Un Limited, ZeN
Is Linux routing your internet connection?
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Standard User RobertoS
(sensei) Tue 24-May-11 22:27:14
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Re: Latest SNR DSLAM algorithm?


[re: mixt] [link to this post]
 
The new version of the DLM, which isn't running everywhere yet, does seem to be able to lower stable lines to 3dB.

One poster though gets that, and at 3dB it is unstable. So he gets messed around by disconnections until those cause the DLM to up it again to 6dB. Which is very stable, so it lowers it to 3dB ....

He isn't very pleased. He'd rather have a stable 6dB.

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - IDNet Home Starter Fibre. Live BQM.

"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
Standard User mixt
(experienced) Tue 24-May-11 22:51:08
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Re: Latest SNR DSLAM algorithm?


[re: RobertoS] [link to this post]
 
Oh I've already had that problem. Now that it insists on 3db, I sometimes end up syncing at around 15100bps, which is right at the border line threshold my line can support. At that rate, FEC errors are thousands per second, which makes the line extremely unstable (infact, at one point my modem was reporting a 0db SNR, which is craziness in itself).

I rebooted the modem during the evening on the weekend (when I knew the line noise would be worst) and it decided to sync at 14500 instead. Much better result, FEC errors are about 10 a second, and all is good.

So I try and leave it well alone now. Thankfully, I can do this as my modem is just acting as a PPPoE bridge, the routing and PPPoE connection are done independently by a separate Linux router.

Now on <aaisp.net>
Previous ISPs: Virgin Media (50Mb/Cable), Be* Un Limited, ZeN
Is Linux routing your internet connection?
Need to make BIND geo-aware?
Standard User b4dger
(knowledge is power) Wed 25-May-11 09:28:48
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Re: Latest SNR DSLAM algorithm?


[re: mixt] [link to this post]
 
Are you on an ADSL2+ connection?

There's been some discussion here before about the Default TSNRM as I also believed it was still 6db. It seems ADSL2+ is a different situation and uses 3db-18db TSNRM range.

Standard User mixt
(experienced) Wed 25-May-11 12:35:59
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Re: Latest SNR DSLAM algorithm?


[re: b4dger] [link to this post]
 
Yes, 21CN here running ADSL2+

That would explain things then!

Now on <aaisp.net>
Previous ISPs: Virgin Media (50Mb/Cable), Be* Un Limited, ZeN
Is Linux routing your internet connection?
Need to make BIND geo-aware?
Standard User MHC
(legend) Wed 25-May-11 12:59:40
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Re: Latest SNR DSLAM algorithm?


[re: RobertoS] [link to this post]
 
Mine would sync at 3dB and did so for over a year - even when I lost sync it would establish at 3dB except a couple of times when it went to 6dB but after a few days a manual resync would drop it back to 3dB.





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Standard User RobertoS
(sensei) Wed 25-May-11 18:37:25
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Re: Latest SNR DSLAM algorithm?


[re: mixt] [link to this post]
 
In reply to a post by mixt:
I rebooted the modem during the evening on the weekend (when I knew the line noise would be worst) and it decided to sync at 14500 instead. Much better result, FEC errors are about 10 a second, and all is good.
Precisely the right thing to do smile. Good luck.

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - IDNet Home Starter Fibre. Live BQM.

"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
Standard User RobertoS
(sensei) Wed 25-May-11 18:38:53
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Re: Latest SNR DSLAM algorithm?


[re: b4dger] [link to this post]
 
In reply to a post by b4dger:
Are you on an ADSL2+ connection?

There's been some discussion here before about the Default TSNRM as I also believed it was still 6db. It seems ADSL2+ is a different situation and uses 3db-18db TSNRM range.
I believe the default (initial) setting is still 6dB, but as you say - the new DLM can drop to 3dB.

My broadband basic info/help site - www.robertos.me.uk
My domains,website and mail hosting - Tsohost. Internet connection - IDNet Home Starter Fibre. Live BQM.

"Where talent is a dwarf, self-esteem is a giant." - Jean-Antoine Petit-Senn.
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