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ADSL connection dropping (again), download speed now restricted by profile (again)

MikeBz
Grafter
Posts: 97
Thanks: 3
Registered: 14-09-2012

ADSL connection dropping (again), download speed now restricted by profile (again)

After a few weeks of normality, barring one drop about 7 days ago, I've had another couple of outages this afternoon following which my download speed has been restricted by the IP profile changing to 7.11Mbps (downstream SNR has jumped from 6 to 16).

 

Please see my other related threads:

https://community.plus.net/t5/Broadband/ADSL-dropping-frequently/td-p/1300266

https://community.plus.net/t5/Broadband/ADSL-dropping-now-almost-unusable/td-p/1299089

https://community.plus.net/t5/Broadband/Ongoing-connection-issues-now-speed-has-halved-again/td-p/13...

 

Is the frequency of connection loss that I'm suffering from excessive, or is the system just being overly trigger-happy in slapping a restrictive profile on me after a disconnection?  I don't know what to do next.

 

Mike

47 REPLIES
Plusnet Staff
Plusnet Staff
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Registered: 05-04-2007

Re: ADSL connection dropping (again), download speed now restricted by profile (again)

Your line really isn't dropping that often:

 

Your SNR target is still at 3db, however it's currently quite high at 16 which is causing the issues you're seeing. Have you tried a single disconnect/reconnect to bring the SNR back down towards the target?

If this post resolved your issue please click the 'This fixed my problem' button
 Chris Parr
 Plusnet Staff
MikeBz
Grafter
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Registered: 14-09-2012

Re: ADSL connection dropping (again), download speed now restricted by profile (again)

What is the best way to do that - power cycle the router, reboot the router or unplug it from the wall for a short while?  I don't want to do anything which makes the line appear to be faulty.

Community Veteran
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Registered: 31-08-2007

Re: ADSL connection dropping (again), download speed now restricted by profile (again)

At a guess, you probably had some sort of noise that caused the connection to drop and it reconnected whilst the noise was present. When the noise has gone the SNRM will rise as it appears to have done.

The safest way to do a resync in this situation is first, to log into the modem/router and find the Disconnect button - if that's the TG582n you are using, you'll see the button in the Internet Box - this drops the PPP session first and help avoid a possible stale session issue. Click Disconnect and then Power off the modem/router for say 10 minutes or so. If your modem/router is a different model with out a Disconnect button, then just power it off. Never just unplug it from the line, that can look like a dropped connection.
Whilst a "reboot" can achieve the same thing and is often suggested, it can again sometimes look like a dropped connection, and if you already have dropped connection issues or high errors (which you may not be aware of) then it might cause DLM to act.

Once you've regained your sync speed, the IP Profile will go up to match, but the Current Line Speed also has to go back up (which can take some time) and then sometimes you have to drop the PPP session to see the increased speed.

I've had a quick glance at your previous threads - good that you've linked them, but personally I would have continued in the previous one, it's easier to see a complete picture then, as this issue never really appears to have been resolved.

So carrying on from here, in the past I don't see anyone advising you to check the phone line and do a Quiet Line Test 17070 option 2. It's likely that you have an Intermittent Line fault of some sort and these can be a real pain to track down. Do you have any problems with incoming or outgoing calls at all?
The other possibility is power glitches. Do you suffer from any of those at all - rural area perhaps?

MikeBz
Grafter
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Registered: 14-09-2012

Re: ADSL connection dropping (again), download speed now restricted by profile (again)

Thanks, lots of useful info there.  The router is a TP Link TD-W8968, it does have a Disconnect button (ADSL WAN Interface page) but it's permanently greyed out...  I'll try powering it off for 10 mins.

I have done the quiet line test in the past,  and I've had a lengthy visit from an Openreach engineer who did all the usual tests with no problems found.   No power glitches,  no problems with calls (the 'phone line still works when I'm having a spate of ADSL disconnections).   I'm in a town about 400metres from the exchange.  Whatever it is, it is highly intermittent.

MikeBz
Grafter
Posts: 97
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Registered: 14-09-2012

Re: ADSL connection dropping (again), download speed now restricted by profile (again)

Strangely I had another disconnection just as I was about to switch the router off.  At that point I did a quiet line test - no noise.

 

So, router off for 15 minutes and now back up & showing the following:

 

Upstream Downstream
Current Rate (Kbps) 888 20347
Max Rate (Kbps) 888 23492
SNR Margin (dB) 10.1 2
Line Attenuation (dB) 7.5 12

 

A BT Wholesale speed test says my downstream IP Profile is back up to 17.95 (was 7.11 after yesterday's dropout).  I'm still only getting just under 7Mbps downstream (it's normally around 14-15) but I guess I now wait for the current line speed to come back up.

Superuser
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Re: ADSL connection dropping (again), download speed now restricted by profile (again)

Is your router forcing the SNRM to 2?

2dB is not a standard target value.  If that is the SNRM just after resynch and the router is not forcing an adjustment, then that implies there is a 1dB increase of noise post the resynch.

If your router is adjusting the SNRM, can you please remove it.  2dB is too low for line stability, as nighttime AM radio interference can easily exceed 2dB.

MikeBz
Grafter
Posts: 97
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Registered: 14-09-2012

Re: ADSL connection dropping (again), download speed now restricted by profile (again)

I can't find any settings in the router which obviously pertain to SNRM, and there is nothing in the manual.

 

In DSL Settings all I have is:

DSL Modulation type [current value is Auto sync-up]

Annex type [current value is Annex A/I/J/L/M]

Enable bit swap [on]

Enable SRA [on]

There is no documentation for these settings, they are the default values.

Community Veteran
Posts: 19,099
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Registered: 31-08-2007

Re: ADSL connection dropping (again), download speed now restricted by profile (again)

It seems fairly obvious that the noise level increased shortly after sync, the opposite of what happened previously. What modem/router is it? It would be an idea to try and use RouterstatsLite.
MikeBz
Grafter
Posts: 97
Thanks: 3
Registered: 14-09-2012

Re: ADSL connection dropping (again), download speed now restricted by profile (again)

TP Link TD-W8968 v1.  As far as I can tell RouterStatsLite isn't compatible with this router Sad 

MikeBz
Grafter
Posts: 97
Thanks: 3
Registered: 14-09-2012

Re: ADSL connection dropping (again), download speed now restricted by profile (again)

I've switched off SRA, though I'm not really expecting it to make any difference.

Downstream SRNM is still between 1.9 and 2.1.

Downstream Current line speed is still down at 7.11mpbs.

Community Veteran
Posts: 19,099
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Registered: 31-08-2007

Re: ADSL connection dropping (again), download speed now restricted by profile (again)

It might be worth trying RSLite with the settings for the other W896x models in case they work. There's also a "User-defined", but see below "Details" - [*] Note that RouterStats-Lite will only work with routers which use a popup dialogue box for Username & Password login.........

MikeBz
Grafter
Posts: 97
Thanks: 3
Registered: 14-09-2012

Re: ADSL connection dropping (again), download speed now restricted by profile (again)

I'm pretty sure I tried that a couple of months ago, but I'll give it another go when I've got time.

MikeBz
Grafter
Posts: 97
Thanks: 3
Registered: 14-09-2012

Re: ADSL connection dropping (again), download speed now restricted by profile (again)

I've been away for a couple of days, so having got back I find my line speed has gone back up to 17.9Mbps, hurrah. I can see from the router log that the connection dropped for 5 minutes in the early hours of yesterday morning. Current router statistics are thus:

 

Upstream Downstream
Current Rate (Kbps) 888 20347
Max Rate (Kbps) 888 23484
SNR Margin (dB) 9.8 1.5
Line Attenuation (dB) 7.5 12
Errors (Pkts) 0 0

 

 

Chris says my SNR target is 3db,  townman says that 2db is too low for line stability, and the router is at this moment in time showing between 1.4 and 1.8db.  I'm at a loss to know what to do.  Is the router 'wrong' to be attempting SNR so low?  The problems I'm having only started in January this year, at which point the router had been running unchanged for a couple of years.  I can cope with the odd disconnection but not if it means getting on to PN regularly to get things reset.

 

Could I have some help/advice from PN please?

 

Superuser
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Re: ADSL connection dropping (again), download speed now restricted by profile (again)

Mike,

I think I need to add clarification to my comment.

Some routers have the ability to adjust the target SNRM from that set by the DLM and given that ability some users push the SNRM too low to allow for night time AM interference.  On a line with a 6dB target, pushing that down to 5 or 4 is not likely to be an issue, however push 3 down to 2 might be too much for dark hours stability.

If your router is not messing with the target SNRM then all should be ok.  Between an hour before sunset to an hour after sunrise AM radio interference can depress SNRM by 2dB or more.  Therefore at 07:40 1.5dB is likely to be passable on a good line.

My prior concern was that the post reporting a 2dB SNRM was implied to be immediately after a resynch, so why if the target is 3dB did the stats report 2dB?  The 'OK' answer is the router adjusted the target, the not so good answer is that there is 1dB of interference coming from somewhere which coupled with night time AM interference is more than enough to drop the line.

I would wait until mid morning (or as late after sunrise as you are able) and do a graceful drop of PPP, then power off the router.  Wait 10 minutes, power it up again and immediately grab the stats and look at the log for the xDSL connection message which should report the target SNRM figures.