Thanks for the response.
Practically speaking, does that indicate a particular direction to focus on (e.g. faulty equipment, interference, a fault in the line) or is it just one of the vagaries of VDSL which I'll need to live with (i.e. I'm stuck with the lower DS sync speed)?

Edited by oracleredux (Thu 09-Dec-21 16:11:59)

Whatever you do don't keep re-sync'ing. It could just be DLM waiting for a few days stability before lowering your sync-time SNR Margin. Which if it happens it will be in three stages, 1dB at a time. Each causing a re-sync at a higher speed.

Thanks - I will leave untouched for a week or so and see if anything changes.
The 4 resyncs since 6 November were all due to my intervention to switch out the modem/ router to the BT HH6 and back again following testing and replacement of the failed PSU on the USG, so the line itself has been stable.

Edited by oracleredux (Thu 09-Dec-21 16:19:52)

Although, given the downstream SNR margin of 6.9dB (correction: 6.4dB), I am not sure whether this is any headroom for the DLM to wait for stability and then change the margin? Unless I'm misunderstanding the process.

Edited by oracleredux (Thu 09-Dec-21 16:22:51)

As mentioned, it should resync down to 3dB ... your 6.4 at present was probably a 6.0 sync and as the environment changes it has gone up to 6.4. So just leave it.


Nothing much you can do except wait and DLM will do it, in its own time!

If the line is clean, which MHC has cast doubt on, the sync-time margin can be reduced by DLM to 3dB. This has been so for many years now. It's just a matter of wait and see.

At least you are still getting a decent speed .

Thanks @Pluralist and @MHC.

I had not appreciated that SNR Margin can now be reduced to 6dB by DLM (the benefits of having a well performing line). I was recalling ADSL days where it was 6dB or 3dB with more forward thinking providers such as Be*. That being said, my parents have a BT line which never shifts off 6dB DS SNR (e.g. 52 days of uptime with no resyncs and a ~6.7dB SNR), and I have monitored that fairly frequently.

Agreed, ~65Mbit is not to be sniffed at!

Thanks again for the advice, I'll see where things are for week or so and report back.

No change in sync rate or SNR Margin which remains (most of the time) around 6.3dB). However, for around 30 minutes this morning the SNR Margin increased markedly to @11.5dB.

See:
SNR Down by band
SNR up by Band
Bitloading

I did not actively turn any equipment off in my house at that time (and would expect further examples if it was due to, for e.g. a fridge compressor, so it isn't clear what has cut in or out within my property or externally.

Stats summary:

Stats recorded 15 Dec 2021 13:25:24

DSLAM type / SW version: BDCM:0xa4a1 (164.161) / v0xa4a1
Modem/router firmware: Not monitored
DSL mode: VDSL2 Profile 17a
Status: Showtime
Uptime: 6 days 18 hours 9 min 45 sec
Resyncs: 4 (since 06 Nov 2021 12:15:21)

Downstream Upstream
Line attenuation (dB): 14.9 0.0
Signal attenuation (dB): Not monitored
Connection speed (kbps): 67422 19999
SNR margin (dB): 6.3 14.8
Power (dBm): 13.4 6.6
Interleave depth: 8 1
INP: 48.00 0
G.INP: Enabled Not enabled
Vectoring status: 5 (VECT_UNCONFIGURED)

RSCorr/RS (%): 0.0001 0.0556
RSUnCorr/RS (%): 0.0000 0.0000
ES/hour: 0 11.5

As ever, would welcome any insight but will keep monitoring.

That 08:30 to 09:05 change ... something odd about that.

Do you have a device that was turned off at that time? Try watching that for a couple of days to see it repeats.

Indeed - rather odd.

I didn't actively turn anything on or off during that period (and was the only one in the house). I have just turned off a few devices in the vicinity of the modem (PoE injectors, chargers, IoT devices etc) and none of those affected SNRM.

I will monitor and see what happens over the coming couple of days.