topic Re: DLM Woes in Fibre

DLM Woes

PsiDOC1 — Wed, 06 Aug 2025 19:12:00 GMT

Hi all.
Some may remember the username form way back when I used to hack BT routers for giggles and give them a new lease of life outside the BT regime. So I kind of know a little bit.
Anyhow: Here's the back story.
A couple of weeks ago I noticed the FTTC VDSL2 connection that usually runs at about 60-ish meg running a bit slow. I checked the router stats and found it to be at 36 Meg. By the time I got to looking into it properly (grandkids were here for a week or so and continuously on devices on internet so was a while before I could get the line freed up!) it had dropped to 27 Meg.
A few tests later and I discovered one of the phone lines in the walls of the house had a leg gone low resistance to ground on my side of the BT Master box. So with the iffy cable disconnected (was a non used line anyway!) I now have the router syncing at between 80 - 86 meg down and 34 meg up - not too shabby. The line rate and Net Data Rate both stayed at 27.3 meg as the DLM has been pulling the speed down and down due to the iffy cable which is understandable.
I waited 24 hours and checked the xDSL stats on the router which was still at 27.3 meg and aside from the FEC count increasing everything else (CRC. ES, SES, UAS etc) was zero.
So I got hold of TalkTalk and explained about the iffy cable and it was my side and now fixed and asked them to reset the DLM or the IP Profile or whatever it is now to allow the speed to come back up and see how high it can go.
Here's the kicker.
I spoke to talk talk on Saturday and nothing has changed since then. Still stuck on 27.3 meg. Still all zeros on the stats aside from the FEC.
So I decided to power cycle the router as I had some cable tidying to do anyway.
Guess what? I's still connecting at 27.3 meg. 🤣
Did I get impatient? I'd have thought 4 days of a perfect connection would have been enough to wake up the most draconian of DLM scripts?
Am I stuck in this 27 meg jail and forever doomed to have grandkids moaning that they are lagging when all of them get on and use every last data bit of my now slow VDSL?
Anything I can do to bump start this process and wake the DLM up?
I can sacrifice an old BT Home Hub to the VDSL gods if necessary - I still have a couple here. 🤣

Here's the router stats - Router is a Zyxel VMG8924-B10A. The original talktalk one got splatted a few years ago during a lightning strike.

====================================================================================
VDSL Training Status: Showtime
Mode: VDSL2 Annex B
VDSL Profile: Profile 17a
G.Vector: Disable
Traffic Type: PTM Mode
Link Uptime: 0 day: 1 hour: 15 minutes
====================================================================================
VDSL Port Details Upstream Downstream
Line Rate: 19.998 Mbps 27.397 Mbps
Actual Net Data Rate: 19.999 Mbps 27.398 Mbps
Trellis Coding: ON ON
SNR Margin: 14.4 dB 22.5 dB
Actual Delay: 0 ms 0 ms
Transmit Power: 6.4 dBm 13.4 dBm
Receive Power: 0.0 dBm -1.8 dBm
Actual INP: 55.0 symbols 54.0 symbols
Total Attenuation: 0.0 dB 14.8 dB
Attainable Net Data Rate: 34.316 Mbps 83.218 Mbps
====================================================================================
VDSL Band Status U0 U1 U2 U3 U4 D1 D2 D3
Line Attenuation(dB): N/A 19.3 29.3 N/A N/A 9.8 23.1 37.4
Signal Attenuation(dB): N/A 18.4 28.4 N/A N/A 12.7 22.9 37.4
SNR Margin(dB): N/A 14.3 14.4 N/A N/A 22.8 22.7 22.3
TX Power(dBm): N/A -23.8 6.4 N/A N/A 10.6 8.1 6.2
====================================================================================

VDSL Counters

Downstream Upstream
Since Link time = 15 min 45 sec
FEC: 0 23
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 15 minutes time = 1 min 10 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 15 minutes time = 15 min 0 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 1 hours 16 min 10 sec
FEC: 0 23
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 23 23
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 1 day time = 0 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Total time = 1 hours 16 min 10 sec
FEC: 0 23
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 23 23
LOS: 0 0
LOF: 0 0
LOM: 0 0
====================================================================================

Re: DLM Woes

fr8ys — Wed, 06 Aug 2025 19:33:23 GMT

When you say powercycle, was the router off for 30 minutes to establish a new session? If not, perhaps try that.

@KeithFrench any thoughts?

Re: DLM Woes

PsiDOC1 — Wed, 06 Aug 2025 19:42:29 GMT

@fr8ys No it was off for a few minutes at best while I tidied up the cables by the master socket where the router is now located.
Should I go for a 30 minute disconnection?
Cheers.

Re: DLM Woes

fr8ys — Wed, 06 Aug 2025 19:47:53 GMT

Worth a try. Is it full fibre? If so turn the ONT off too.

Re: DLM Woes

PsiDOC1 — Wed, 06 Aug 2025 19:53:22 GMT

No it's not FTTP - we don't get such luxuries out in the sticks.
It's 65 meg fibre to the cabinet.

OK I'll give the half an hour disconnection a shot.
I can do that without a riot on my hands now the grandkids have gone home. 🤣

Re: DLM Woes

fr8ys — Thu, 07 Aug 2025 07:18:36 GMT

@PsiDOC1

How did it go? Any joy or still an issue?

Re: DLM Woes

nomfezeko-TT — Thu, 07 Aug 2025 08:25:45 GMT

Thank you so much @fr8ys for helping out, we will wait for the customer to get back to us and let us know if your advice has helped sort the problem or if they are still having issues so we can help further.

Re: DLM Woes

KeithFrench — Thu, 07 Aug 2025 10:37:57 GMT

Sorry for the delay in replying @PsiDOC1 @fr8ys

There is no way to reset DLM on an FTTC connection, or at least none that is available without a particular request from TalkTalk to Openreach.

Re: DLM Woes

PsiDOC1 — Thu, 07 Aug 2025 15:24:57 GMT

Me again.
I went off to bed and switched it all off with the intention of reading and switching it all back on 30 mins later.
I woke up 6 hours later and thought oh damn. 🤣
I powered it all back on and checked this morning before work and viola! 73meg connection.
Here's the router stats

====================================================================================
VDSL Training Status: Showtime
Mode: VDSL2 Annex B
VDSL Profile: Profile 17a
G.Vector: Disable
Traffic Type: PTM Mode
Link Uptime: 0 day: 10 hours: 3 minutes
====================================================================================
VDSL Port Details Upstream Downstream
Line Rate: 19.998 Mbps 73.612 Mbps
Actual Net Data Rate: 19.999 Mbps 73.613 Mbps
Trellis Coding: ON ON
SNR Margin: 14.3 dB 8.1 dB
Actual Delay: 0 ms 0 ms
Transmit Power: 6.6 dBm 13.5 dBm
Receive Power: 0.0 dBm -2.0 dBm
Actual INP: 55.0 symbols 52.0 symbols
Total Attenuation: 0.0 dB 15.0 dB
Attainable Net Data Rate: 33.158 Mbps 82.007 Mbps
====================================================================================
VDSL Band Status U0 U1 U2 U3 U4 D1 D2 D3
Line Attenuation(dB): N/A 19.7 29.7 N/A N/A 10.0 23.5 37.8
Signal Attenuation(dB): N/A 18.8 28.7 N/A N/A 12.9 23.2 37.8
SNR Margin(dB): N/A 13.8 14.5 N/A N/A 6.7 8.4 9.1
TX Power(dBm): N/A -23.9 6.6 N/A N/A 10.6 7.8 7.0
====================================================================================

I'll remember that 30 minute trick in the future as that's a very handy piece of information.
OK back to hacking hubs for me.
Thanks all.
Si

Re: DLM Woes

fr8ys — Thu, 07 Aug 2025 15:37:55 GMT

@PsiDOC1 Great, pleased it worked.

Re: DLM Woes

Mandisa-TT — Thu, 07 Aug 2025 15:45:07 GMT

Thanks for getting back to us! It sounds like your router decided to take a little nap too! 😄 I guess it needed its beauty sleep just like the rest of us.

Great to hear you’ve got a solid 73 meg connection now! Thanks @fr8ys and @KeithFrench for all your help. @PsiDOC1 Is there anything else I can assist you with?

Re: DLM Woes

PsiDOC1 — Thu, 07 Aug 2025 18:41:29 GMT

It did indeed and thanks for that trick. It's one to remember in the future if I get more in house wiring shenanigans.

Re: DLM Woes

PsiDOC1 — Thu, 07 Aug 2025 18:43:04 GMT

Tomorrow night's euromillions lottery numbers would be a big help.
Seriously, though, Thank you. I learned along the way as well which is always a good thing.
Cheers.
Si