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ThinkPadUser
Contributor
858 Views
Message 1 of 9

VDSL/FTTC - SNR would slowly drop and then the connection would disconnect every few days

Hi, I'm noticing a pattern with my line. For whatever reason, the SNR would slowly drop to around 4.0db and then give it a few hours and it would disconnect.

Annotation 2020-07-25 012039.png

DSLStats graph showing the disconnection which would happen around midnight.

Before this, I noticed the line spike downwards from time to time as seen here:

Annotation 2020-07-02 122248.png

Tonight I've noticed a spike and the line disconnecting as well. This was the night after the first screenshot:

ThinkPadUser_0-1595719846046.png

 

Modem: Zyxel VMG8924-B10A

xdslctl stats at 00:32 BST 26/07/2020:

xdslctl info --stats
xdslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason: 1
Last initialization procedure status: 0
Max: Upstream rate = 5158 Kbps, Downstream rate = 32678 Kbps
Bearer: 0, Upstream rate = 5124 Kbps, Downstream rate = 29999 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 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): 6.6 6.1
Attn(dB): 26.8 0.0
Pwr(dBm): 5.1 5.2

VDSL2 framing
Bearer 0
MSGc: -6 33
B: 65 160
M: 1 1
T: 0 5
R: 6 16
S: 0.0000 0.9979
L: 8340 1419
😧 1 1
I: 72 177
N: 72 177
Q: 8 0
V: 6 0
RxQueue: 128 0
TxQueue: 32 0
G.INP Framing: 18 0
G.INP lookback: 31 0
RRC bits: 0 24
Bearer 1
MSGc: 90 -6
B: 0 0
M: 2 0
T: 2 0
R: 16 0
S: 10.6667 0.0000
L: 24 0
😧 1 0
I: 32 0
N: 32 0
Q: 0 0
V: 0 0
RxQueue: 0 0
TxQueue: 0 0
G.INP Framing: 0 0
G.INP lookback: 0 0
RRC bits: 0 0

Counters
Bearer 0
OHF: 0 44115
OHFErr: 0 0
RS: 41133912 2867026
RSCorr: 47 0
RSUnCorr: 0 0
Bearer 1
OHF: 44451 0
OHFErr: 0 0
RS: 266335 0
RSCorr: 0 0
RSUnCorr: 0 0

Retransmit Counters
rtx_tx: 305542121 0
rtx_c: 194057 0
rtx_uc: 422501 0

G.INP Counters
LEFTRS: 64 0
minEFTR: 29991 0
errFreeBits: 1484135884 0

Bearer 0
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 41191007 0
Data Cells: 435503 0
Drop Cells: 0
Bit Errors: 0 0

Bearer 1
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 0 0
Data Cells: 0 0
Drop Cells: 0
Bit Errors: 0 0

ES: 84 23
SES: 61 1
UAS: 150 91
AS: 715

Bearer 0
INP: 52.00 0.00
INPRein: 1.00 0.00
delay: 0 0
PER: 0.00 16.27
OR: 0.01 19.16
AgR: 30461.01 5142.82

Bearer 1
INP: 2.50 0.00
INPRein: 2.50 0.00
delay: 0 0
PER: 16.06 0.01
OR: 47.81 0.01
AgR: 47.81 0.01

Bitswap: 493/493 1/1

Total time = 11 days 3 hours 22 min 43 sec
FEC: 613034 9601
CRC: 3769 54
ES: 84 23
SES: 61 1
UAS: 150 91
LOS: 3 0
LOF: 19 0
LOM: 28 0
Latest 15 minutes time = 7 min 43 sec
FEC: 35 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: 78935 0
CRC: 1814 0
ES: 29 0
SES: 28 0
UAS: 51 23
LOS: 1 0
LOF: 7 0
LOM: 21 0
Latest 1 day time = 3 hours 22 min 43 sec
FEC: 146621 39
CRC: 1816 6
ES: 30 3
SES: 28 0
UAS: 51 23
LOS: 1 0
LOF: 7 0
LOM: 21 0
Previous 1 day time = 24 hours 0 sec
FEC: 87913 149
CRC: 536 27
ES: 11 13
SES: 10 0
UAS: 32 22
LOS: 1 0
LOF: 6 0
LOM: 0 0
Since Link time = 11 min 55 sec
FEC: 47 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
NTR: mipsCntAtNtr=0 ncoCntAtNtr=0
>

Error averages from 18/07/2020 to 25/07/2020

ThinkPadUser_5-1595720200477.png

ThinkPadUser_6-1595720210213.pngThinkPadUser_7-1595720227611.pngThinkPadUser_8-1595720235904.png

ThinkPadUser_9-1595720267535.pngThinkPadUser_10-1595720276298.png

ThinkPadUser_11-1595720288298.pngThinkPadUser_12-1595720298746.png

 

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8 REPLIES 8
TimCurtis
Recognised Expert
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Message 2 of 9

Re: VDSL/FTTC - SNR would slowly drop and then the connection would disconnect every few days

@ThinkPadUser 

2 things.

1. Any noise on the line , plug a corded phone into the test socket & dial 17070 option 2. It should be silent.

2. Can you try with a HomeHub so as to rule out any issue with the Zyxel.

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ThinkPadUser
Contributor
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Message 3 of 9

Re: VDSL/FTTC - SNR would slowly drop and then the connection would disconnect every few days

Hi, 

I haven't got a corded phone but with a cordless one I've heard a low hum with a quiet thud before or after the announcer says "Quiet line test"

Regarding ruling out the Zyxel, I've ran the line with an Openreach HG612 a few weeks ago and noticed that the line would spike downwards as well with the HG612.

 

Annotation 2020-06-30 121501.png

A spike from the HG612 seen in the last 30 days. They seem to happen around midnight to 3 am time period.

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imjolly
Distinguished Sage
Distinguished Sage
785 Views
Message 4 of 9

Re: VDSL/FTTC - SNR would slowly drop and then the connection would disconnect every few days

have you tried using the test socket for quiet line test  the low hum is normal for cordless but the quiet thud is not.

is there anything in your home the switches on or off about the times of the spike



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ThinkPadUser
Contributor
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Message 5 of 9

Re: VDSL/FTTC - SNR would slowly drop and then the connection would disconnect every few days

So I did do the test via the test socket and the line was mostly quiet though I did hear two hums, one lower and one higher. No idea if that's caused by the cordless phone or not.
I could also hear a faint noise at the end of the announcer going "Quiet Line Test".

Regarding if anything in my home turns on or off during this time, I would say no. I'm the last one to be awake in the home and I'm on my computer when it usually happens. Unless someone switching on or off lights can cause spikes, I'm not aware of anything else that would have caused it in my home.

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pippincp
Sage
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Message 6 of 9

Re: VDSL/FTTC - SNR would slowly drop and then the connection would disconnect every few days

I've never heard of 2 hums with a cordless phone (not saying it can't happen) but faint noise  during the quiet line test suggests  a line problem. That's why we alays suggest using a (less than £10) wired phone for the test as it cuts out the possible variations a cordless may have.

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ThinkPadUser
Contributor
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Message 7 of 9

Re: VDSL/FTTC - SNR would slowly drop and then the connection would disconnect every few days

Ok, so should I call up BT or wait for a mod to pick this case up?
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pippincp
Sage
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Message 8 of 9

Re: VDSL/FTTC - SNR would slowly drop and then the connection would disconnect every few days

Will be resolved quicker if you ring up.

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ThinkPadUser
Contributor
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Message 9 of 9

Re: VDSL/FTTC - SNR would slowly drop and then the connection would disconnect every few days

So I called BT, they've told me that the drops were in the normal range and that the line was fine despite the faint noise on the quiet line test.

Not sure what else I can do from here...

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