Broadband Related > Broadband Technology
SNRM shoots up with no reconnect/resync/retrain
Weaver:
On one of my lines, line #3, the upstream SNRM just shot up suddenly, from 6 dB to 9.6 dB and it has stayed up there for 9 hours so far. NB The target SNRM was 6 dB.
* The weird thing was that the modems did not retrain/resynch/reconnect! This would have shown up in AA’s logs, and it would show up in the ‘link uptime’ value in the stats summary below.
Note that the downstream sync rate for line #3 has been an all-time record high of > 3.2 Mbps @ 3dB d/s target SNRM. More importantly though, the upstream line #3 sync rate is currently a record high.
Here are the stats for all modems, but it’s modem #3 that you need to look at. I have a pretty picture of SNRM vs time for line 3.
Status of each link
─────────────────────
* There are 2 links. They are: #1 and #3
* The links in use are: #1 and #3
* The modems successfully queried are: #1 and #3
────────────────────────────────────
***
*** There is some badness; all is not well ! 😦
***
────────────────────────────────────
--
Link #1: sync rate: downstream: 2.769 Mbps at SNRM 2.3 dB; upstream: 676 kbps at SNRM 6.7 dB
Link #1: link uptime: 8 days 4 hours 43 min 45 sec
--
Link #3: sync rate: downstream: 3.151 Mbps at SNRM 2.8 dB; upstream: 728 kbps at SNRM 9.5 dB
Link #3: ES downstream: 'penultimate' period: ES: 32 per hr; MTBE: 112.5 s; bucket duration: 900 s
Link #3: link uptime: 2 days 16 hours 25 min 47 sec
--
Time now: 2023-01-26 07:43:35 UTC. | This software version is v1.31 2023-01-24.
◅ ◅ ◅◊▻ ▻ ▻
Chrysalis:
the target SNRM unless using SRA is only the target at sync time, so an increase of SNRM is unlikely to trigger a resync I think. :)
So the mystery is what improved the line conditions.
Weaver:
Line #3 upstream had a bit of a minor struggle with sustaining a 6 dB target SNRM in the past. The SNRM did not droop much at all, and indeed was rigidly fixed at 6dB precisely throughout the day when the strange jump occurred, but there had always been a fair few ES regularly, so the noise background must I suspect have been a bit spiky. There was no interleave upstream on line #3 which I think was really bad and probably was part of the answer to why it wasn’t coping perfectly. In contrast line #1 upstream had an interleave depth of 8 and no problems.
So is that all there is to it: the line suddenly improved massively, but how?
Here are the full raw stats from a later time still, well after the jump; Line #3, 2023-01-26 13:35 :
--- Code: ---xdslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason: 8000
Last initialization procedure status: 0
Max: Upstream rate = 854 Kbps, Downstream rate = 3172 Kbps
Bearer: 0, Upstream rate = 728 Kbps, Downstream rate = 3151 Kbps
Link Power State: L0
Mode: ADSL2 Annex A
TPS-TC: ATM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 2.9 9.6
Attn(dB): 63.0 40.1
Pwr(dBm): 18.4 12.4
ADSL2 framing
Bearer 0
MSGc: 59 11
B: 98 22
M: 1 1
T: 1 4
R: 0 0
S: 0.9950 1.0000
L: 796 184
D: 1 1
Counters
Bearer 0
SF: 15627005 61809
SFErr: 1138 2578
RS: 0 1518713
RSCorr: 0 0
RSUnCorr: 0 0
Bearer 0
HEC: 1928 1079
OCD: 14 0
LCD: 14 0
Total Cells: 1878187096 433810943
Data Cells: 315389796 39977601
Drop Cells: 0
Bit Errors: 74335 108019
ES: 23322 25322
SES: 2029 3
UAS: 647465 645747
AS: 252710
Bearer 0
INP: 0.00 0.00
INPRein: 0.00 0.00
delay: 0 0
PER: 16.16 17.00
OR: 32.16 8.00
AgR: 3171.61 733.13
Bitswap: 49374/49380 3374/3374
Total time = 152 days 22 hours 26 min 44 sec
FEC: 568397 43732
CRC: 117611 31648
ES: 23322 25322
SES: 2029 3
UAS: 647465 645747
LOS: 268 0
LOF: 618 0
LOM: 205 0
Latest 15 minutes time = 11 min 44 sec
FEC: 0 0
CRC: 2 8
ES: 2 4
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: 8 0
ES: 7 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 22 hours 26 min 44 sec
FEC: 0 0
CRC: 328 355
ES: 298 323
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 1 day time = 24 hours 0 sec
FEC: 0 0
CRC: 393 820
ES: 348 795
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Since Link time = 2 days 22 hours 11 min 49 sec
FEC: 0 0
CRC: 1138 2578
ES: 1025 2016
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
NTR: mipsCntAtNtr=0 ncoCntAtNtr=0
--- End code ---
Alex Atkin UK:
It could perhaps be a crosstalker moving from ADSL to VDSL?
Weaver:
Alex, that is the kind of event we’re looking for. It happened at 22:30-something, I forget the exact time, but I’ve saved the graph of SNRM vs time, so I can look it up. The time of day is a bit odd. Maybe someone unplugged or switched off a modem ?
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