I used DSLstats to grab this. It may have answered my question as the line speed has crept up by 1Mb since this time yesterday.
There do seem to be a lot of FEC errors, but I was looking at BT's DSL checker again to see what line speed I should be expecting and my line is now marked as having a bridge tap. The current line rate of 40.5Mbps is actually 0.5Mbps above the projected top end for an impacted line, so I won't bother complaining.
xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 12051 Kbps, Downstream rate = 45480 Kbps
Bearer: 0, Upstream rate = 9999 Kbps, Downstream rate = 40510 Kbps
Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 5.9 8.1
Attn(dB): 20.4 0.0
Pwr(dBm): 12.1 7.4
VDSL2 framing
Bearer 0
MSGc: 18 58
B: 51 236
M: 1 1
T: 64 23
R: 12 16
S: 0.0408 0.7543
L: 12536 2694
D: 793 1
I: 64 127
N: 64 254
Counters
Bearer 0
OHF: 30867457 1601981
OHFErr: 536 56
RS: 3607005183 51838
RSCorr: 775589 62361
RSUnCorr: 5840 0
Bearer 0
HEC: 1344 0
OCD: 35 0
LCD: 35 0
Total Cells: 2014087693 0
Data Cells: 194618265 0
Drop Cells: 0
Bit Errors: 0 0
ES: 166 54
SES: 0 0
UAS: 41 41
AS: 81001
Bearer 0
INP: 3.00 0.00
INPRein: 0.00 0.00
delay: 8 0
PER: 2.62 8.70
OR: 73.16 58.79
AgR: 40583.47 10057.90
Bitswap: 51678/51678 544/544
Total time = 22 hours 30 min 42 sec
FEC: 775589 62361
CRC: 536 56
ES: 166 54
SES: 0 0
UAS: 41 41
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 15 minutes time = 42 sec
FEC: 715 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: 6189 3
CRC: 0 1
ES: 0 1
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 22 hours 30 min 42 sec
FEC: 775589 62361
CRC: 536 56
ES: 166 54
SES: 0 0
UAS: 41 41
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
Since Link time = 22 hours 30 min 1 sec
FEC: 775589 62361
CRC: 536 56
ES: 166 54
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
#
Edit:
And the Stats page, if it's any use:
Stats recorded 11 Jul 2017 18:33:11
DSLAM/MSAN type: BDCM:0xa48c / v0xa48c
Modem/router firmware: AnnexA version - A2pv6C038m.d24j
DSL mode: VDSL2 Profile 17a
Status: Showtime
Uptime: 23 hours 9 min 47 sec
Resyncs: 0 (since 11 Jul 2017 18:28:39)
Downstream Upstream
Line attenuation (dB): 20.4 0.0
Signal attenuation (dB): Not monitored
Connection speed (kbps): 40510 9999
SNR margin (dB): 5.9 8.1
Power (dBm): 12.1 7.4
Interleave depth: 793 1
INP: 3.00 0
G.INP: Not enabled Not enabled
Vectoring status: 5 (VECT_UNCONFIGURED)
RSCorr/RS (%): 0.0208 1.6444
RSUnCorr/RS (%): 0.0002 0.0000
ES/hour: 10.0 0
One thing I have noticed is that my minimum pings have increased from about 5ms to 14ms over the past day or so. I've run a tracert and it shows this:
1 <1 ms <1 ms <1 ms R7800 [192.168.1.1]
2 * * * Request timed out.
3 * * * Request timed out.
4 13 ms 13 ms 13 ms 31.55.187.184
5 13 ms 13 ms 13 ms core2-hu0-17-0-1.southbank.ukcore.bt.net [195.99.127.188]
[Blah blah blah]
I live about half a mile from the XXX XXX, so 13ms seems a bit high to the first hop. I'm guessing interleaving has been turned on?