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ADSL link momentarily dropping

odyssea4
Dabbler
Posts: 23
Thanks: 4
Registered: ‎17-03-2019

ADSL link momentarily dropping

Hi,

We are having problems with our ADSL link occasionally dropping.  Typically, this happens once a day, or every 2 days, usually during times of high usage.  I would attribute this to the ASUS DSL-AC68U router, but for two observations:

  • The problem sometimes occurs when the router isn't actually passing that much traffic, but when one would expect the UK network to be busy.
  • The same thing used to happen occasionally with the old Thomson router that was supplied when we moved to PlusNet.

It was only when our daughter started to use the internet that we really noticed how often it was occurring, which was one of the reasons for buying a new router, but until COVID-19 lockdown started it was just a minor irritation.  However, with three family members now connecting into work and school remotely, it is now becoming a problem, particularly since it has recently happened twice during video-conference calls. 

I have checked the logs that the router generates during one of these events and the first message is simply "WAN Connection: No response from ISP." which doesn't give much away as to what is going on.  I have increased the PPP Echo Max Failures threshold, in case the router was struggling to receive a echo response from the other end when traffic is heavy, but this seems to have had little effect (I think it should only send PPP echoes when there is no other traffic but it seemed worth a try at the time) .

I have also noticed that every time the link drops, our internet-facing IP address changes, so I'm wondering if something odd is happening with the DHCP lease. 

I've had a look around in the router's operating system to see if I can increase the verbosity of its logging, in order to get some further insight, but haven't found an obvious way of doing so.  Given that I can provide exact times of when the drop-outs occur, though, I was wondering what I would need to do to request a PlusNet engineer to take a look at the logs from their end of the link to see if those provide any further insight?

Kind regards,

Simon

31 REPLIES 31
Beyhive
Plusnet Alumni (retired)
Plusnet Alumni (retired)
Posts: 722
Fixes: 44
Registered: ‎25-02-2019

Re: ADSL link momentarily dropping

Hi @odyssea4,

I've checked the connection this side and it looks like the signal strength for your line is set too low which explains the disconnections.

 

I have placed an order to up your signal strength which should complete in the next 4 hours. If you then turn the router off and then on again in 4 hours or later the connection should be back to normal for you.

Let us know how it goes please.

If this post resolved your issue please click the 'This fixed my problem' button
 Faris
 Plusnet Help Team
odyssea4
Dabbler
Posts: 23
Thanks: 4
Registered: ‎17-03-2019

Re: ADSL link momentarily dropping

Hi @Beyhive ,

Thank you for looking into this.  I've rebooted the router this morning so we'll see how it goes for a few days.

Kind regards,

Simon

odyssea4
Dabbler
Posts: 23
Thanks: 4
Registered: ‎17-03-2019

Re: ADSL link momentarily dropping

Hi @Beyhive,

It looks like the problem is still there, since the link dropped out again at almost exactly 3pm today (the first time since the reboot yesterday morning) . At the time, my daughter was in a video call on Microsoft Teams and I had just started a audio call on Skype for Business). 

I've attached the logs from the router (router uses GMT timestamps).  If I've interpreted the logs correctly, one notable difference, on this occurrence, is that it looks like the router had two attempts before it re-established the connection. 

Below is part of the traffic graph for the WAN interface on the router. It is notable that the incoming traffic (orange bars) leading up to the outage isn't that heavy, although outgoing traffic (cyan bars) was getting close to the max uplink bandwidth of the line.  Having said that, the link has coped with heavier sustained outgoing traffic on other occasions over the past 24 hours without any problems.

activity-graph-to-20200429-1550.png

 

As always, any insight you can provide from your side would be very gratefully received.

 

Kind regards,

Simon

odyssea4
Dabbler
Posts: 23
Thanks: 4
Registered: ‎17-03-2019

Re: ADSL link momentarily dropping

I haven't had any further feedback from PlusNet for a couple of weeks so I'm raising it to the top of the pile again because the problem is still happening (in fact, it's getting embarrassing because it's interfering with video calls with customers). 

By using tcpdump on my router I have managed to log traffic on the PPP interface when the fault occurs.  The first indication of a problem is that the stream of packets incoming from the WAN ceases but the router continues to transmit packets about 15-30 seconds afterwards, suggesting that it thinks the PPP connection is still up, until some timeout occurs which causes it to reset the connection.  Therefore, I would still like to know what the router at the PlusNet end of the link reports when the failure occurs, because it appears that either something is causing it to cease transmitting traffic over the link, or its output signal is being attenuated to an extent that my router is failing to receive them. 

Any further advice on this would be very greatly appreciated.

Kind regards,

Simon

Tomca
Grafter
Posts: 33
Thanks: 10
Fixes: 1
Registered: ‎09-03-2020

Re: ADSL link momentarily dropping

@odyssea4 Thanks for getting back to us. Sorry to hear you're still having issues, the connection seems very stable from looking at our connection logs, however the SNR (signal to noise) on the line was very low, this could be the cause or the errors on the connection.

 

I've placed an order to change this and also made some adjustments that should stop the SNR from going too low again in the future.

 

I hope this helps.

 

Thanks - Carl.

 Carl Tomlinson
 Plusnet Help Team
odyssea4
Dabbler
Posts: 23
Thanks: 4
Registered: ‎17-03-2019

Re: ADSL link momentarily dropping

Hi @Tomca,

Thank you for looking into this.  Unfortunately, the problem is still happening.  With regard to your post, the connection does seem to be very stable - except when it goes down!  The pattern of fault occurrences, and previous experience diagnosing faults on comm links, suggests to me that the problem is not completely attributable to the SNR.  The evidence from this end suggests that the router just ceases to receive traffic over the link and eventually times out the connection.  Hence, I would like to know, if possible, what the equipment at the PlusNet end thinks is happening when a drop-out occurs so that we might be able to determine the root cause. That's why I originally asked if it was possible for someone to review the connection logs from the PPP termination equipment at the PlusNet end from around the time that a drop-out occurred, if I could point you to the exact time.  The latest link drop occurred at 16:01 BST today and came back up at 16:04.

Kind regards,

Simon

 

Gandalf
Community Gaffer
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Registered: ‎21-04-2017

Re: ADSL link momentarily dropping

Hi Simon thanks for getting back to us. I'm sorry for the issues with your connection.

Our logs don't show us anything that would get to the bottom of this. For example, the various messages we can see directly in our radius server for the cause of the drops are "User request", "Administrative reset" and "Lost carrier".

What's more important is the series of testing we can run using our suppliers systems. I've tested the copper line and the tests are showing "CIDT FAULT - HIGH RESISTANCE IMBALANCE DETECTED" which we'd need to progress as a broadband fault and potentially arrange a broadband engineer to investigate further.

Would it be possible though for you to disconnect all equipment from every telephone socket you have, and remove the faceplate of the master socket revealing the test socket in the bottom right hand corner? If you could then post back I can retest your line and see if the fault's still showing which will narrow down where the issue lies.

From 31st October 2022, I no longer have a regular presence here as I’ve moved on to a new role.
Anoush Mortazavi
Plusnet
odyssea4
Dabbler
Posts: 23
Thanks: 4
Registered: ‎17-03-2019

Re: ADSL link momentarily dropping

@Gandalf,

Thank you for replying so promptly and I'm sorry I missed your posting until now.  If you can let me know a time which is convenient to you (preferably any day after 16:30), I will make sure everything is disconnected at this end and post confirmation to you on this thread, so you can run the tests.

Thank you again.

Kind regards,

Simon

Gandalf
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Registered: ‎21-04-2017

Re: ADSL link momentarily dropping

Thanks for getting back to me @odyssea4

No problem, if you can disconnect everything within the next 10 minutes and post back I can retest your line straight away.

Alternatively we could schedule this for 5pm tomorrow?

From 31st October 2022, I no longer have a regular presence here as I’ve moved on to a new role.
Anoush Mortazavi
Plusnet
odyssea4
Dabbler
Posts: 23
Thanks: 4
Registered: ‎17-03-2019

Re: ADSL link momentarily dropping

@Gandalf,

All disconnected and faceplate removed. Ready when you are. Please let me know when complete so I can reconnect everything.

Simon
Gandalf
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Re: ADSL link momentarily dropping

Thanks Simon, apologies for the delay the series of tests took a while to complete. 

Line tests are now passing with no high resistance fault found so I think we'd need to do a bit of process of elimination, putting things back together piece by piece running a test at each point in-between.

For now I'd recommend putting everything back together how it was as I'm about to log off now for the night. 

Would you be free at 5pm tomorrow for half an hour?

I'd be free all day from 11:30 to 8 apart from 4 to 4:30 (that's when I have my daily team meeting)

From 31st October 2022, I no longer have a regular presence here as I’ve moved on to a new role.
Anoush Mortazavi
Plusnet
odyssea4
Dabbler
Posts: 23
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Registered: ‎17-03-2019

Re: ADSL link momentarily dropping

@Gandalf,
Thank you for checking that out. By all means I can be ready at 5pm tomorrow.
Thank you so much for your help.
Simon
Gandalf
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Registered: ‎21-04-2017

Re: ADSL link momentarily dropping

No problem Simon and sounds good.

From 31st October 2022, I no longer have a regular presence here as I’ve moved on to a new role.
Anoush Mortazavi
Plusnet
odyssea4
Dabbler
Posts: 23
Thanks: 4
Registered: ‎17-03-2019

Re: ADSL link momentarily dropping

Hi @Gandalf,

I am ready when you are, if you want to do some more tests.

Simon