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Recent Drop in Margin and Sync

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Dabbler
Posts: 22
Thanks: 2
Registered: ‎27-03-2018

Recent Drop in Margin and Sync

Hi

Have had problems with DSL dropping for years. Problem is random with heavy burst of noise affecting almost all tones. Have never managed to resolve this. As it happens less than once a day have set my router to auto-reboot each morning.  Have got around 5 mbps every day for years with a SNRM around 15 dB.  This week have noticed streaming youtube was poor and router indicates SNRM dropped to 12.5 and sync rate has dropped from 5 mb to 3 mb.  Rebooted but still the same. I also notice that attainable rate has increased from around 5.5 mb to 8.6 mb.  Line attenuation looks to be the same at 45.5 dB. I also note increase in interleaver depth to 160 downstream, although not sure exact figure before.  BtW speed test = 1.58/0.57. 

Have attached router stats.  Have DSLstats if it will help.  Any help appreciated.

12 REPLIES 12
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Hero
Posts: 4,833
Thanks: 1,618
Fixes: 48
Registered: ‎24-02-2012

Re: Recent Drop in Margin and Sync

@melindwr I am no expert here, but one thing I would not recommend is setting a daily reboot - the DLM will interpret this as a problem, and in part, this is probably part of your speed issue - it will automatically reduce your speed/increase the noise margin to compensate.

You appear to be on a longish line, and my initial thought is that the attainable rate looks a little high, but I could be wrong here.

If he doesn't mind, I'm going to tag @Townman here, and see if he has any thoughts.

John
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Dabbler
Posts: 22
Thanks: 2
Registered: ‎27-03-2018

Re: Recent Drop in Margin and Sync

Have a daily reset for at least 3 years, have no option as there seems no solution to the Shine problem. Each day router syncs at 5 mb until this week and DLM has decreased my margin (from 15 to 12.5) not increased it or am I misunderstanding something?. My line is clearly not capable of 8 mb attainable rate!

What will happen if I tell my Billion router to increase margin back to 15?Huh

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Hero
Posts: 4,833
Thanks: 1,618
Fixes: 48
Registered: ‎24-02-2012

Re: Recent Drop in Margin and Sync

If this has been going on for this length of time, it begs the question of have you ever investigated/reported it?

If you have DSLstats reports, do they show a variation over time of your D/S SNR?

If you reset your margin to 15, it is still possible for the DLM to 'adjust' it.

John
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Dabbler
Posts: 22
Thanks: 2
Registered: ‎27-03-2018

Re: Recent Drop in Margin and Sync

I did investigate it and concluded that sudden noise is not within the power of BT or PN to solve.  But I am open to further help with this. However my sync rate has typically been around 5000 Kb and margin around 15 dB. Today it is 3071 and 12.6 dB.  In fact had the margin dropped to this level before this week I would have no internet at all! I have DSLstats but have not used it for some time, as I can check the stats each time I reboot the router manually when it drops when I am online.

Should you be able to help with the dropping connection I will explain.  Internet drops no traffic either up or down, margin has dropped. DSL is (usually) still synced (as reported by router) PPP has dropped. Try to to reconnect PPP no luck will not connect.  Only a reboot will restore connection. Billion 7000DXL and Archer D5 plugged into test socket.  In the past had dsl stats running all the time.  Last data recorded from router showed massive errors and and noise on most of the tones.  I did raise this with PN at the time.  Maybe I should raise it again.

I gave up. Rebooting once a day may have degraded my speed but I was able to live with 5000Kb.

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Hero
Posts: 4,833
Thanks: 1,618
Fixes: 48
Registered: ‎24-02-2012

Re: Recent Drop in Margin and Sync

This is slightly beyond my personal experience - I am entirely self-taught in these things and have no real networking knowledge.

As I have said above, I have tagged a much more experienced community member - hopefully he will pick this up fairly soon, but I am not really in a position to make any useful comments at the moment.

It may, however, be a good idea to run DSLstats for 24 hours or so to give some indication of the problem.

John
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Dabbler
Posts: 22
Thanks: 2
Registered: ‎27-03-2018

Re: Recent Drop in Margin and Sync

Thanks a lot for your help. I have dslstats running and keeping daily logs.

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Superuser
Superuser
Posts: 16,313
Thanks: 6,621
Fixes: 56
Registered: ‎22-08-2007

Re: Recent Drop in Margin and Sync

Hi,

John has out lined things fairly well. Accepting that there is SHINE rebooting the router needed or not will not help matters. Certainly rebooting it in the presence of SHINE is not ideal but might well be unavoidable.

It is worth taking a pace back here to understand SNRM - this is not a static metric. The line has a TARGET SNRM and a current SNRM - the router only reports the current SNRM. Note you might see the target SNRM recorded in the router log on a resync. This is how things work...

When the router attempts to sync it will negotiate the best possible sync speed to attain the TARGET SNRM over the then present noise. Thereafter the sync speed remains constant for the xDSL session. If the background noise present at resync goes down, the current SNRM goes up; conversely if the background noise increases the current SNRM goes down. Therefore looking at the current SNRM on a problematic line, when not knowing the target is a bit pointless - it is the relative value, not the absolute value which is important.

The normal target is 6dB - unstable lines get banded as given higher targets in 3dB steps (6, 9, 12...) so it looks as though yours has a deep banding, possibly consequential to the daily reboots.

What is thought to be the source of the SHINE?

XDSL stats running constantly is a good initial step to profiling the source - look for patterns in the change of SNRM. You need fine granularity in the sampling - every 10-15 seconds. I’ve seen spikes from high speed electric trains and with fine granularity been able to discern the direction of travel from the 50 or so seconds of plotting.

It’s a bit like the hunt for Red October - UI need to ping it just right.

You should raise a broadband fault report if only to get the DLM reset ... and oh don’t mess with the SNRM tweaking - it just confuses matters when you’re trying to drain the swamp.
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Dabbler
Posts: 22
Thanks: 2
Registered: ‎27-03-2018

Re: Recent Drop in Margin and Sync

Thank you for for reply. I am not too clever with this stuff but I have a better understanding of how this works. Three years ago I spent months with PN faults and Kitz forum trying to find the source of SHINE. I could not.  I live in a very rural area, so few sources of EM noise. I found that there was was an instantaneous burst of noise which dropped the PPP session.  The router would not automatically or manually reconnect. Initially I thought the router (Archer D5) was the problem so I bought a Billion 7800dxl. Problem persisted. Only rebooting would work. The only discernible pattern was that all drops were during the hours of darkness, but could be anytime during the night. 

In the end I gave up and settled with reboot as I still achieved 5000 Kb + on my line with 45.5 dB attn. This week something has changed as I already outlined.

On your advice, I have increased sampling frequency in DSLStats and will wait and see what happens over the next few days and report back.

 

Thank you again.

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Plusnet Help Team
Plusnet Help Team
Posts: 282
Thanks: 95
Fixes: 24
Registered: ‎08-04-2020

Re: Recent Drop in Margin and Sync

Fix

Hi @melindwr

 

Sorry to hear about issues with your broadband. I have looked into settings and BRAT to check for any patterns of noise.

BRAT is not indicating SHINE, there were few spikes of noise in last 14 days but not every day and SNR was quite stable for several days in a row. There were some fluctuations but nothing significant.

But as stated by @Townman - finding sources of any SHINE is a like hunting for Red October.

 

Profile was capped so I've requested DLM reset and set up SNR target to 9dB. Profile was capped most likely due to restarts of router - DLM "considered" this line as unstable and capped speed profile to stabilise it. 

I have updated your IP profile too as was matching capped speed profile,

 

Can you please leave router connected and don't restart it for few days so DLM won't cap this profile again?

 Piotr
 Plusnet Help Team
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Dabbler
Posts: 22
Thanks: 2
Registered: ‎27-03-2018

Re: Recent Drop in Margin and Sync

Around 9pm router dropped PPP connection.  SNRM dropped very quickly and rapid drop in SNR per tone and hence accumulating errors. Have tried to reconnect PPP but it is not connecting. Have screendumped most of DSLStats graphs and copied stats and connection stats to a text file. You will have your own side of this problem. Have had to reboot rooter and all is fine again.

Not sure what to attach to help solve this as there are quite a few graphs:

SNR, Conection Speed, Bit loading and SNR per Tone, CRC SES and ES, QLN, Hlog

Have the stats and connection stats in PDF Router Noise

 

 

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Dabbler
Posts: 22
Thanks: 2
Registered: ‎27-03-2018

Re: Recent Drop in Margin and Sync

Internet dropped again at around 4.30am 17th. Router indicates dsl and PPP connection but could not access the internet. SNR per tone similar to previous drop. Ended PPP session but could not reconnect. Had to reboot router.
 
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Dabbler
Posts: 22
Thanks: 2
Registered: ‎27-03-2018

Re: Recent Drop in Margin and Sync

Fault raised by PN Admin. Openreach visit arranged.  Wait to see if they can help.

Thanks all who helped.