VDSL errors (CRC, HEC, Frame) are they bad?

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GRISDALE

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Topic # 222715 25-Aug-2017 09:27

Hello,

I've been getting a bunch of different errors on my connection and am trying to figure out what causes these and what kind of symptoms they would exhibit. I've read a bunch of conflicting information on CRC errors, some saying large amounts are fine and some saying the opposite.

I have practically no internal wiring. The phone wire comes out of the ground then a chorus tech put a master filter on that wire then a jackpoint after the filter. There are no other wires or jackpoints coming off it and there's about 1m of wire in total from the point where it comes out of the ground to the jackpoint. I've also tried different modems and changing the 1 internal cable which goes from the jack point to the modem.

Here are my line stats:

stats

Any ideas?

Jase2985

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Reply # 1852341 25-Aug-2017 09:51

4038 in 305 minutes is only 13 per minute, which i believe is fine, its when you are getting down to a couple a second is when you start to have issue

hio77

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Reply # 1852480 25-Aug-2017 12:22

Lately i have seen more issues with people having high FEC errors rather than CRC, CRC error will result in a retransmit.

Realtime traffic is where you will notice the issue, TCP should handle packetloss okay.

Have a look at the thread above, this customer was an astronomical error rate, being on the upstream channel when the DSLAM was loaded this was causing random packetloss etc while correcting.

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smalltrader

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Reply # 1852744 25-Aug-2017 17:09

hio77:
Lately i have seen more issues with people having high FEC errors rather than CRC, CRC error will result in a retransmit.

Realtime traffic is where you will notice the issue, TCP should handle packetloss okay.

Have a look at the thread above, this customer was an astronomical error rate, being on the upstream channel when the DSLAM was loaded this was causing random packetloss etc while correcting.

smalltrader

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Reply # 1852751 25-Aug-2017 17:15

smalltrader:
hio77:
Lately i have seen more issues with people having high FEC errors rather than CRC, CRC error will result in a retransmit.

Realtime traffic is where you will notice the issue, TCP should handle packetloss okay.

Have a look at the thread above, this customer was an astronomical error rate, being on the upstream channel when the DSLAM was loaded this was causing random packetloss etc while correcting.

Interesting observation on high FEC errors. Same thing happens to me. In the last 2 weeks, ddDLM has twice adjusted my profile to 17a with a down sync of 59 Mbps and 6 dB. It has dropped back to 8b and 49 Mbps sync 12 dB due to very high FEC errors. CRC errors are actually very low, not even 1 crc error per minute.

I wonder if there is a wider network issue due to weather or my line has gone bad for some reasons.

hio77

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Reply # 1852770 25-Aug-2017 18:12

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smalltrader:

Interesting observation on high FEC errors. Same thing happens to me. In the last 2 weeks, ddDLM has twice adjusted my profile to 17a with a down sync of 59 Mbps and 6 dB. It has dropped back to 8b and 49 Mbps sync 12 dB due to very high FEC errors. CRC errors are actually very low, not even 1 crc error per minute.

I wonder if there is a wider network issue due to weather or my line has gone bad for some reasons.

FEC's may be minor in terms of they are corrected, however if you have multiple lines pulling 100K+ per second this is obviously going to be degrading to the network.

Being that these are upstream, it is CPE side but at peak times is certainly noticeable in customer traffic. (not saying out of peak it is not also noticeable, simply that is the only times it has been raised)

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smalltrader

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Reply # 1852780 25-Aug-2017 18:53

@hio77

Is high FEC error normally a sign of wider network problem or is this more a problem with the line from my house to the cabinet ? Other than bad weather no other environmental factors in the last month for me. At one stage my line was stable at 68 Mbps with a 6 dB profile for a few weeks.

hio77

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Reply # 1852949 26-Aug-2017 12:29

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smalltrader: @hio77

Is high FEC error normally a sign of wider network problem or is this more a problem with the line from my house to the cabinet ? Other than bad weather no other environmental factors in the last month for me. At one stage my line was stable at 68 Mbps with a 6 dB profile for a few weeks.

Depends on the channel it is on, 99% of the time any error issues are wiring related and not a overall area fault. - Otherwise likely there would already be a FRE

#include <std_disclaimer>

Any comments made are personal opinion and do not reflect directly on the position my current or past employers may have.

smalltrader

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Reply # 1853041 26-Aug-2017 17:44

hio77:
smalltrader: @hio77

Is high FEC error normally a sign of wider network problem or is this more a problem with the line from my house to the cabinet ? Other than bad weather no other environmental factors in the last month for me. At one stage my line was stable at 68 Mbps with a 6 dB profile for a few weeks.

Depends on the channel it is on, 99% of the time any error issues are wiring related and not a overall area fault. - Otherwise likely there would already be a FRE

Thanks for the clarification. Hopefully it is more weather related rather than something really bad happening to the external line.

freakngeek

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Reply # 1854356 28-Aug-2017 20:57

Having issues my self with FECs, started when Interleave depth dropped from over 900+ to 150 a couple of weeks back.
With higher interleave depth, there were FECs but not to this extend.
Below is from modem being up 7 days, check out the FECs, not a single CRC error though

SNR on Downstream is currently 5db, the FECs pile on when this iS at 5db, when SNR at 6db (most of the day) the FECs no longer increase as fast.

But 555,000,000 FECs in 166 hours
= 3,340,000 FECs per hour
= 55,700 per minute
= 928 per second

Everything seems to work as it should
I'll need to do some testing on this
Cable from Road side pillar to Modem is 1m, don't think its that, can't be solar charger as currently dark
Modem running directly of battery no noise in that.
Neighbours line comes from same road side pillar, but heads in own trench, doubt they have VDSL as driveway over 1km to house for them

freakngeek

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Reply # 1854397 28-Aug-2017 21:34

In the 25 minutes since above post another 9million FECs occurred, so...

Forcing the DV130 to sync at +1db via CLI
Modem now syncing at 7db, not a single FEC (yet)
Getting slightly lower downstream sync speed as expected now
But looking back at above with the SNR at 5db the Sync speed is faster than attainable

webwat

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Reply # 1858605 5-Sep-2017 00:56

hio77:

smalltrader: @hio77

Is high FEC error normally a sign of wider network problem or is this more a problem with the line from my house to the cabinet ? Other than bad weather no other environmental factors in the last month for me. At one stage my line was stable at 68 Mbps with a 6 dB profile for a few weeks.

Depends on the channel it is on, 99% of the time any error issues are wiring related and not a overall area fault. - Otherwise likely there would already be a FRE

Its related to something on the line, but may or may not be your house wiring. One issue might be to do with crosstalk since most of your neighbours are probably using DSL and sometimes the lines in the street have multiples, ie not just a straight run to your house. I would ask your internet provider if there is an option to increase the SNR setting at their end.

Qualified in business, certified in fibre, stuck in copper, have to keep going ^_^