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Low SNR early signs of a fault?

Community Veteran
Posts: 3,187
Thanks: 20
Fixes: 2
Registered: 31-07-2007

Low SNR early signs of a fault?

DLM dropped my connection twice last night, second time SNR dropped from 6 too 3.  When that happened on my old DSL connection it was always a phone line fault was the cause, but not sure if its true for fibre or if my connection is just that good.  Using a Billion 8800NL so hopefully its able to hold the connection on 3 SNR


edit: forgot to say already done a couple of quiet line tests over 15mins trying to catch any hissing but none


  Downstream Upstream
Line Coding (Trellis) On On
SNR Margin (dB) 2.8 4.8
Attenuation (dB) 20.6 0.0
Output Power (dBm) 13.0 6.6
Attainable Rate (Kbps) 63352 18838
Rate (Kbps) 74380 20000
B (# of bytes in Mux Data Frame) 239 236
M (# of Mux Data Frames in an RS codeword) 1 1
T (# of Mux Data Frames in an OH sub-frame) 22 5
R (# of redundancy bytes in the RS codeword) 0 16
S (# of data symbols over which the RS code word spans) 0.1027 0.3771
L (# of bits transmitted in each data symbol) 18696 5410
D (interleaver depth) 1 1
I (interleaver block size in bytes) 240 255
N (RS codeword size) 240 255
Delay (msec) 0 0
INP (DMT symbol) 0.00 0.00
OH Frames 0 0
OH Frame Errors 113567 2438
RS Words 0 1858287
RS Correctable Errors 0 20
RS Uncorrectable Errors 0 0
HEC Errors 390541 0
OCD Errors 12 0
LCD Errors 12 0
Total Cells 777843408 0
Data Cells 5488962 0
Bit Errors 0 0
Total ES 48762 2310
Total SES 87 6
Total UAS 160 231239



Unvalued customer since 2001 funding cheap internet for others / DSL/Fibre house move 24 month regrade from 8th May 2017
Aspiring Pro
Posts: 960
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Registered: 11-01-2008

Re: Low SNR early signs of a fault?

Your connection may have dropped and re-synced at a target noise margin of 3dB instead of 6. This would be an indication that DLM sees your connection as stable and able to cope with a lower target SNR margin, thus giving you an increased line speed.

My other car isn't a Ferrari
Plusnet Staff
Plusnet Staff
Posts: 17,641
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Registered: 05-04-2007

Re: Low SNR early signs of a fault?

Nothing to be concerned about unless you do start to have issues, @maranello is accurate in their response.

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 Chris Parr
 Plusnet Staff
Community Veteran
Posts: 5,034
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Registered: 10-06-2010

Re: Low SNR early signs of a fault?

Considering that the attainable rate figure is much lower than the current line rate, it looks like the 2.8 dB current SNRM is lower than whatever the target SNRM was, so it probably connected when there was less noise present.

Community Veteran
Posts: 5,510
Thanks: 687
Registered: 23-09-2010

Re: Low SNR early signs of a fault?

This used to be the norm that if your line managed a long uptime it automatically changed from 6 to 3.

But I assume this has more to do with BT's rumoured experiment of dropping everyone to 3 if their line stands a chance of maintaining it.