You'd think so at first, but that's not the case. It really is a DLM imposed cap. In fact, I thought so too, so I rebooted the modem a couple times but it always resynced at exactly 47146.
That's interesting & it can't be pure coincidence to achieve EXACTLY the same sync speed on rebooting the modem.
Initially, the resync occurred by itself at about 6am. Stats showed there were about 16 FEC and CRC errors at the time, in total, accumulated over 5 days. SNR margin was 13.5 and attainable rate over 92000.
Nothing really obvious then to have caused the resync.
Have you tried the ongoing stats that plot your connection stats minute by minute?
You may be able to see SNRM tailing off to zero (sometimes negative values) over a few minutes before the connection resyncs & puts SNRM back to usual levels.
I do a full reboot of the modem and it's still at exactly 47146.
I know it does suffer badly from crosstalk - it's 90m from cabinet and should have an attainable rate well over 100 - but full modem stats here show quite high noise across the spectrum. I've done some investigation, and reducing attenuation simply increases the noise by the same amount, while shielded cable makes no difference - so I conclude it's crosstalk as it's coming from further up the line than my property and is surprisingly flat across the whole 30a spectrum.
I see from those stats that Interleaving depth (D) is quite high at 1686 DS & 527 US.
I imagine that Impulse Noise Protection (INP) & delay (delay) will also be quite high too.
INP & delay can be seen lower down the full Plink.log
How did you manage to reduce attenuation?
My connection suffers from really high attenuation that simply stops it syncing at anything higher than around 30 Mb.
Another trick I have up my sleeve is picking up the phone, which instantly reduces attainable rate by about 5mbps as follows:
Attainable rate (kbit/s) 89516 26890
SNR margin (dB) 12.9 8.4
Line attenuation (dB) 0 0
Output power (dBmV) 12.6 5.7
I occasionally see that phenomenon on my connection.
Attainable rates fluctuate in line with SNRM fluctuations.
I have seen SNRM dropping when dialling out to run the 17070 quiet line test etc.
My SNRM is usually only around 5dB or so, often dropping naturally to 3.5dB to 4dB overnight.
When the using the phone is especially bad, SNRM drops by 4dB or so which immediately forces the connection to resync (usually at a lower speed).
Dialling in to the phone sometimes causes SNRM to increase or lower.
Again, dialling in sometimes causes an immediate resync.
The last time dialling in caused a resync, the connection achieved a higher sync speed & then maintained stability for quite a few days, SNRM levels only dropping by 0.1dB or 0.2dB as should be expected.
It's almost as though the pulsed ringing tone voltages/current caused a dodgy connection somewhere in the D-Side cable to "fix itself".
Quiet line tests are always QUIET nowadays whenever I run them.
I have had many engineer visits due to my connection's instability & low(ish) speeds, "stuck" DLM profiles etc.
In attempts to permanently fix this particular phone issue, engineers have removed a double jumpered connection in the cabinet, replaced & rerouted my drop wire from the DP (approx 50m in length), replaced the master socket filtered faceplate, replaced just the filter pcb & replaced some slightly corroded cabinet jumper wires.
Each time, the connection seems to be fixed, but it usually only lasts for a few days.
More recently, I have noticed the phone issue appears to start as the weather changes to warm & dry periods for a few days.
April was supposedly one of the wettest & coldest on record.
It may be pure coincidence, but my connection was at its most stable during April.
The weather was quite warm & dry yesterday & my connection had resynced at only 23313 k at 20:12 while we were out last night.
My ongoing graphs show that SNRM had dropped from 4.5dB to -0.2dB (minus value) over around 1 hour, before causing the resync.
I tried the phone thing & noticed changes in SNRM levels while testing.
My connection resynced again at 29307 k at 07:02 this morning, while we were still in bed.
My ongoing logs do not show any particular issues for around that period.
Latest 24 hour ongoing stats here
Using the phone has gone back to only very insignificant changes in SNRM levels.
I'll see if that changes if the weather stays warm & dry for the next few days.
However, once again, a forced resync comes back again at exactly 47146/18998:
Downstream Upstream Downstream Upstream
Line rate (kbit/s) 47146 18998 0 0
CRC errors 0 0 0 0
FEC errors 0 0 0 0
HEC errors 0 0 0 0
(So exactly the same behaviour as when it was previously stuck at 60181 for 7 days - aside from when DLM changes my line speed cap, my line hasn't had a single unexpected resync/loss of sync since it's been installed)
I wonder if your connection has started to develop an intermittent D-Side fault, possibly similar to mine?
One engineer in another forum has suggested that the plug in connection module at some DPs (known as a coffin lid DP due to its shape) can be a little unreliable. i.e. not always maintaining a solid connection on the relatively thin wires in use.
Apparently, a "fix" for this is to crimp some thicker wire to the thin wire & use the thicker wire for the actual plug in connection.
I wonder if Zarjaz and/or any other engineers would be able to comment on that as a "potential" cause of using the phone issues.
This is all ifs, buts & maybes & as these issues tend to be intermittent, it must be really hard for engineers to track them down as they may not be prevalent at the time of their visits.