This topic

FTTC DLM query

Andrew600 — Mon, 04 Nov 2024 16:20:27 GMT

Following a landline disconnection caused by contractor incompetence, Openreach turned up this morning to sort it out.

Broadband wasn’t affected and remained up at full 80/20 speed.

In the process of fixing the landline he disconnected the broadband at the cabinet which at first reconnected at 80/20, but after a few minutes it resynced automatically at 72/20 and the maximum data rate is now only 74 mbps compared to the normal 85 or so.

SNR has increased to 6.4 instead of 3.

The OR guy said he thought DLM had got upset and intervened, to give it 24 hours then to give him a call if it doesn’t recover and he will reset it. I’m grateful he gave me contact details to be honest.

Question is does this make sense and is a DLM reset the thing to do if it doesn’t sort itself out.

Thanks for any thoughts.

Re: FTTC DLM query

licquorice — Mon, 04 Nov 2024 16:28:56 GMT

Just leave things alone and DLM will revert to 3dB snrm in steps.

Resetting won't help as it will just reset to the default 6dB snrm which is the situation you are in now.

You certainly won't be able to tell the difference between 72M and 80M in the real world anyway.

Re: FTTC DLM query

imjolly — Mon, 04 Nov 2024 16:30:59 GMT

Yes the resets/disconnections have triggered the DLM to increase the noise margin resulting in drop in connection speed. This will correct itself automatically given a stable connection and 7/10 days

Re: FTTC DLM query

Andrew600 — Mon, 04 Nov 2024 16:38:11 GMT

Thanks both. I’ll leave it alone.

Glad I posted now. I had no idea the default was 6dB, and a loss of 10% speed will have no effect at all for my usage anyway.

Thanks for the replies. Much appreciated.

Re: FTTC DLM query

Andrew600 — Thu, 14 Nov 2024 11:08:27 GMT

Sorry to be a pain about this. It’s just ticked over 10 days up time with no DLM intervention yet.

Is it time for a hub restart?

Stats:-

DSL uptime:10 days,00 Hours06 Mins08 Sec

Data rate:19.999 Mbps / 72.038 Mbps

Maximum data rate:25.005 Mbps / 74.131 Mbps

Noise margin:15.3 / 6.3

Line attenuation:5.3 / 9.4

Signal attenuation:5.2 / 10.8

Re: FTTC DLM query

licquorice — Thu, 14 Nov 2024 15:10:16 GMT

Unfortunately, if DLM hasn't dropped your noise margin to 3dB by now it isn't going to. A hub restart won't do anything to prompt DLM.

Not what you want to hear, but there is absolutely nothing you can do to invoke 3dB margin.

Re: FTTC DLM query

Andrew600 — Thu, 14 Nov 2024 15:21:51 GMT

Thanks @licquorice

Yep, not what I wanted to hear.
I wonder what the OR contractor, then an OR engineer did to provoke this. It’s been at 3dB and 80/20 for longer than I can remember, so something fairly significant happened. It was without any doubt a contractor foul up, but it will remain an unsolved mystery.

At least, as you suggested, the impact on my day to day use is zero, so it doesn’t really matter. It’s just the numbers annoying me.

Re: FTTC DLM query

licquorice — Thu, 14 Nov 2024 15:33:05 GMT

DLM seems to be very flaky and temperamental I'm afraid. Probably no consolation, but my line has been banded at 44M with 9dB margin for months despite being totally stable.

You could try one restart of the hub but I would be extremely surprised if it kicked DLM into life.

Re: FTTC DLM query

Andrew600 — Thu, 14 Nov 2024 16:39:01 GMT

You were right.
A hub restart made no difference at all.
Once is enough. I won’t be doing another. I’ll just live with it and hope it sorts itself out one day.

I hope yours improves soon. 🤞

Re: FTTC DLM query

licquorice — Thu, 14 Nov 2024 16:51:10 GMT

If it has kicked DLM, you won't see an immediate change. It will still need to see that your line will cope with reducing SNRM before it does so. Check again in a few days, but I'm very doubtful it will.

Re: FTTC DLM query

Andrew600 — Fri, 29 Nov 2024 16:14:08 GMT

I just realised something I should have checked all the way back at the start of this, but didn’t think to check because the landline had just been repaired.
The phone is humming on a quiet line test. It’s not noisy enough to interfere with calls, but it’s not silent either.

It’s an old phone temporarily plugged into the master socket, not a dect by the way.

Fault reported….again.

I’m guessing it could well be why DLM hasn’t done anything to increase speeds.

Re: FTTC DLM query

licquorice — Fri, 29 Nov 2024 16:48:52 GMT

Indeed it could well be.

Possibly an earth contact fault causing the hum.

Re: FTTC DLM query

Andrew600 — Tue, 03 Dec 2024 15:20:16 GMT

No nearer a solution after the latest Openreach visit sadly.
The fault has apparently been detected as being 100+ metres beyond our street cabinet and is not easily repairable because of a collapsed/damaged duct.

A request for complete replacement of the offending cable has been made today, but I dread to think of the timescale involved with that. Potentially a road closure would be needed. The OR engineer certainly wasn’t prepared to make a guess.

A question please and me thinking out loud really.

Given the cable from the cabinet to us is said to be perfect, is there anyway I can force a switch to digital voice despite it being copper from the cabinet? That would bypass the problem by cutting power to the offending cable wouldn’t it?

Failing that, should it drag on, I guess I could try to renegotiate a broadband only connection to achieve the same thing and switch the household to 100% mobile.

Re: FTTC DLM query

licquorice — Tue, 03 Dec 2024 16:14:33 GMT

The fault can't be on the 'E' side (beyond ) of the cabinet as that isn't carrying the broadband and thus DLM.

Scrap that. Yes, it could affect the 'D' side as well as there is a DC path through the cabinet.

If you moved to DV, there would no longer be a DC path through to the faulty E side, so yes, it should clear your fault.

Re: FTTC DLM query

Andrew600 — Tue, 03 Dec 2024 17:09:56 GMT

Thanks @licquorice

I’m pleased my thinking wasn’t totally wrong.

I think what I’ll do is live with it over Christmas to see if any repair eta appears, but as BT have just sent me the standard your service should be fixed now message I suspect I might not have any idea what’s happening going forward. I suppose I’ll have to mark it as not fixed and see.

If nothing acceptable is proposed, I can then discuss the options with BT retail from a stronger position.

As an aside, the engineer implied quite strongly that they are fed up with dealing with the neglected copper network. I can sympathise. I’ll be glad to see the back of it too. Sadly FTTP is only estimated for by Dec 2026 for us.

Re: FTTC DLM query

Andrew600 — Thu, 05 Dec 2024 09:40:28 GMT

It looks like BT are now aware that it’s an ongoing fault, so that’s a small positive.

I just received this.

”We're sorry, but we need to do some more work to fix your fault. This means it'll be a bit longer before we can get your service up and running again.
We'll let you know as soon as we have more news for you.”

I’ll park this one for now and reassess in January.

Re: FTTC DLM query

Andrew600 — Mon, 09 Dec 2024 09:55:47 GMT

A small unexpected update.

24 hours after the email posted above, BT unilaterally marked the fault as fixed despite me saying it wasn’t.
Whether Openreach have any plans to fix it properly I have no idea. I’ve lost all means of tracking progress.

I still plan to wait until January before doing anything else.

Re: FTTC DLM query

Andrew600 — Sun, 19 Jan 2025 09:51:34 GMT

Another update, positive this time.

The E side copper fault has definitely not been fixed, but DLM appears to have reduced the noise margin to 3 over night.

Although the maximum data rate is much lower than it used to be and seems to be reflecting the effects of the fault, I’m now getting all of that data rate delivered to the hub, so essentially I’m back to normal….for now anyway.
Fingers crossed that it stays like this.

Hub log looks like this at the moment.

DSL uptime:0 days,06 Hours59 Mins57 Secs

Data rate:19.999 Mbps / 79.999 Mbps

Maximum data rate:30.755 Mbps / 74.423 Mbps

Full Fibre (FTTP) Mode:Off

Noise margin:11.5 / 3.1

Line attenuation:5.1 / 9.1

Signal attenuation:5.1 / 10.5

Re: FTTC DLM query

Andrew600 — Thu, 17 Apr 2025 09:52:50 GMT

I knew it was too good to last. The hub has rebooted for the first time since my last post due to a firmware update and it’s back to square one. The landline has continued to slowly get more and more noisy and maximum data rate has dropped back to 70 mbps again.

After BT initiating and then cancelling an upgrade to Digital Voice with no explanation I called them to ask why and after a very long call with 4 different people I finally managed to get them to raise an order for a switch to Digital Voice in two weeks time.
I had to resist several attempts to recontract me, switch me to EE on a new expensive contract, etc etc. It was a painful process, but hopefully DV will solve our issues.

Re: FTTC DLM query

imjolly — Thu, 17 Apr 2025 10:31:19 GMT

not sure how DV will solve the problem as you will still have the same FTTC connection just your phone will connect to socket on back of hub instead of master socket but hub will still be connected to master socket

if you have had a few resets/drops in connection has your noise margin gone up from about 3db?