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Standard User djandyr
(newbie) Mon 16-Jan-12 14:17:36
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Disconnections on 2 lines


[link to this post]
 
We have two lines with Entanet which have been perfect for over 5 years but both now are experiencing very frequent disconnections and very slow throughput for the last month. A BT voice and broadband engineer have been called out and cannot find any faults on BT side, only replacing the faceplace on both lines. They requested to Entanet to replace the line card on the DSLAM

Entanet responded blaming BT, and they want to wait 12 days to stablise the line, decreasing the bandwidth until disconnections stop. If this doesnt work they want BT out to look for REIN interference.

The only thing puzzling about the REIN, is that we have other offices in the building and their ADSL from different providers using the same exchange (LVBOO) is absolutely fine, no disconnections and good speed.

The BT speedtester reports on both lines reports no problem, however speed tests on both lines using speedtest.net report < 2mb.

Could anyone shed any light, or suggest any ideas on what the problem could be?

BiPAC 7300N

DMT Status Up
Operational Mode ADSL2+
Upstream 1171 kbps
Downstream 17434 kbps
SNR Margin (Upstream) 6.2 db
SNR Margin (Downstream) 0.1 db
Line Attenuation (Upstream) 14.5 db
Line Attenuation (Downstream) 29.0 db

BiPAC 5200N

Line State: Showtime
Modulation: ADSL2 PLUS
Annex Mode: ANNEX_A
Upstream 1048 kbps
Downstream 18108 kbps
SNR Margin (Upstream) 6.5 db
SNR Margin (Downstream) 0.3 db
Line Attenuation (Upstream) 14.9 db
Line Attenuation (Downstream) 30.0 db

Edited by djandyr (Mon 16-Jan-12 14:24:14)

Standard User RobertoS
(sensei) Mon 16-Jan-12 14:22:29
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Re: Disconnections on 2 lines


[re: djandyr] [link to this post]
 
Those stats look as though the connection speed has been tweaked at your end by altering the sync-time noise margin. Is that the case?

Alternatively the BT DLM has reduced it to 3dB. Please can you resync one of them and take the stats immediately afterwards.

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.

Edited by RobertoS (Mon 16-Jan-12 14:24:12)

Standard User djandyr
(newbie) Mon 16-Jan-12 14:30:50
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Re: Disconnections on 2 lines


[re: RobertoS] [link to this post]
 
Thanks for the reply,

We havent tweaked sync time noise margin, although the BT broadband engineer was here for most of the day running tests, and his notes mention an SNR reset.

Edited by djandyr (Mon 16-Jan-12 22:57:17)


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Standard User RobertoS
(sensei) Mon 16-Jan-12 14:32:18
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Re: Disconnections on 2 lines


[re: djandyr] [link to this post]
 
Resync is done by you!

Just power off the router for a couple of minutes is easiest.

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 djandyr
(newbie) Mon 16-Jan-12 14:40:33
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Re: Disconnections on 2 lines


[re: RobertoS] [link to this post]
 
Just restarted the router, and took the stats immediately.

BiPAC 5200N

Line State: Showtime
Modulation: ADSL2 PLUS
Annex Mode: ANNEX_A
Upstream 1071 kbps
Downstream 18234 kbps
SNR Margin (Upstream) 6.7 db
SNR Margin (Downstream) 3.0 db
Line Attenuation (Upstream) 14.9 db
Line Attenuation (Downstream) 30.0 db
Standard User RobertoS
(sensei) Mon 16-Jan-12 15:11:29
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Re: Disconnections on 2 lines


[re: djandyr] [link to this post]
 
Yes, the downstream margin has been set to 3dB.

Ever since BT introduced ADSLx the standard setting has been 6dB, then higher in 3dB steps if the line is unstable or has a lot of errors.

Since quite recently, (different dates on different exchanges), it has been able to drop it automatically to 3dB if the line is stable.

Several posters have reported that when it did that their line became unstable, and the DLM didn't have the nous to up it to 6dB again. Presumably because a few a day is within tolerance.

The noise margin can easily vary by 3dB over 24 hours, and often considerably more. I suggest that yours are around the 3dB variation level and it just takes something like a phone call, or a microwave oven being used, to send it too low and cause a disconnection/reconnection, which sets it back to 3dB but slower.

Enta should be able to get the sync-time margin set to a minimum of 6dB. That will cost you a bit of speed, but you are currently getting well above the expected speed for that line - due to the 3dB setting. A 6dB setting would bring you down to the top end of the expected.

Alternatively, if your routers allow you to adjust it yourself, that would be my preferred route. The reason being that they may have to make it so it can't rise to 9dB if anything happens in the future degrading the line quality. If that happened you would need to remember this episode and get it changed perhaps to automatic again.

Another option, if your routers are supported by RouterStats Lite, would be to install that and monitor the movement of the noise margin for a few days. You need to set it to save graphs and to log to file, so we can help analyse the results. I like to set the sampling interval to 5 seconds when there is a problem like this to find. You can fnd it by scrolling down past the full version, on this page.

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 aquiss
(experienced) Mon 16-Jan-12 16:10:36
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Re: Disconnections on 2 lines


[re: RobertoS] [link to this post]
 
In reply to a post by RobertoS:
Yes, the downstream margin has been set to 3dB.

Ever since BT introduced ADSLx the standard setting has been 6dB, then higher in 3dB steps if the line is unstable or has a lot of errors.


Missing from your reply, though for clarity. It should be noted that BT has a new target margin of 3dB on 21CN lines which alot of lines have now defaulted to. This came into action around October time (off memory).

Martin Pitt
Aquiss Internet
http://www.aquiss.net

Home Broadband Packages : http://www.aquiss.net/home-broadband.php
Business Broadband Packages : http://www.aquiss.net/business-broadband.php
Aquiss Partner Scheme : http://www.aquiss.net/partners.php
Standard User djandyr
(newbie) Mon 16-Jan-12 16:17:45
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Re: Disconnections on 2 lines


[re: RobertoS] [link to this post]
 
Many thanks for your reply,

We have tweaked the SNR on one of our routers to 6.8db, and we are monitoring the lines with routerstats lite.

Will update to see if the line throughput and disconnections have settled.
Standard User RobertoS
(sensei) Mon 16-Jan-12 16:36:00
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Re: Disconnections on 2 lines


[re: aquiss] [link to this post]
 
In reply to a post by aquiss:
Missing from your reply, though for clarity. It should be noted that BT has a new target margin of 3dB on 21CN lines which alot of lines have now defaulted to. This came into action around October time (off memory).
In reply to a post by RobertoS:
Since quite recently, (different dates on different exchanges), it has been able to drop it automatically to 3dB if the line is stable.

Several posters have reported that when it did that their line became unstable, and the DLM didn't have the nous to up it to 6dB again. Presumably because a few a day is within tolerance.
smile ?

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 aquiss
(experienced) Mon 16-Jan-12 19:56:21
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Re: Disconnections on 2 lines


[re: RobertoS] [link to this post]
 
Sorry, totally missed that. That's what a 5.00am start does to the brain! (or age).

Martin Pitt
Aquiss Internet
http://www.aquiss.net

Home Broadband Packages : http://www.aquiss.net/home-broadband.php
Business Broadband Packages : http://www.aquiss.net/business-broadband.php
Aquiss Partner Scheme : http://www.aquiss.net/partners.php
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