cancel
Showing results for 
Search instead for 
Did you mean: 

High numbers of CRC errors

FarmerGiles
Dabbler
Posts: 15
Registered: ‎16-01-2011

High numbers of CRC errors

Hi all
Is this something Plus Net would be able/prepared to investigate?  Line is otherwise stable now though, and throughput OK.  Neighbour's line (only just next door and on same cable with same hardware) shows only a small number of CRCs.  This implies that my line is noisy or suffering interference.
I should say that when line syncs at slower speed (200k-300k slower) the number of CRCs is very similar.
.....or should I just consider myself lucky that it works at all?
Regards
Stats:
Uptime: 4 days, 5:30:43
Modulation: G.992.1 Annex A
Bandwidth (Up/Down) [kbps/kbps]: 448 / 2,080
Data Transferred (Sent/Received) [MB/MB]: 78.31 / 373.77
Output Power (Up/Down) [dBm]: 11.5 / 17.0
Line Attenuation (Up/Down) [dB]: 31.5 / 63.5
SN Margin (Up/Down) [dB]: 6.0 / 7.5
Vendor ID (Local/Remote): TMMB / ALCB
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 0 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 13,485 / 0
FEC Errors (Up/Down): 396 / 690,881
CRC Errors (Up/Down): 64 / 19,279
HEC Errors (Up/Down): 34 / 14,209
9 REPLIES 9
FarmerGiles
Dabbler
Posts: 15
Registered: ‎16-01-2011

Re: High numbers of CRC errors

Any takers?
spraxyt
Resting Legend
Posts: 10,063
Thanks: 674
Fixes: 75
Registered: ‎06-04-2007

Re: High numbers of CRC errors

5000 downstream CRC errors per day, is high but not excessive. If the DLM was bothered it would raise your target noise margin reducing sync speed.
Does noise (SN) margin vary considerably between daylight hours and night-time?
You could monitor noise margin continuously using RouterStats. The full product should work with your router. I suggest using the configuration guidelines posted here. The bit loading plots might identify if particular frequencies are unduly subject to noise, though since your sync speed is about right for the attenuation I suspect not.
David
MisterW
Superuser
Superuser
Posts: 14,581
Thanks: 5,413
Fixes: 385
Registered: ‎30-07-2007

Re: High numbers of CRC errors

Your line IS quite long as shown by the 63.5db attenuation. The downstream speed you're getting ( 2080 ) is about what you'd expect for that length of line from the graph here http://www.internode.on.net/residential/adsl_broadband/easy_broadband/performance/
TBH Those CRC errors are not that high for 4 days uptime. Your SNR is at 7.5 which tends to imply a 6db target which means the line isn't perceived by the exchange as particularly noisy, otherwise it would have raised the target. What might be useful is to connect to the test socket ( http://www.plus.net/support/broadband/bbfaults/master_socket_testing.shtml ) for a couple of days ( assuming you have one ) and repost the stats. We can then see if your internal wiring is having an effect on the errors.

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

adamwalker
Plusnet Help Team
Plusnet Help Team
Posts: 16,871
Thanks: 882
Fixes: 221
Registered: ‎27-04-2007

Re: High numbers of CRC errors

As this is a long line there may not be much improvement we can make here to be very honest.
I've checked our connection logs and can see that the line is quite stable with connections in excess of 4 days at a time which is good.
What are your speeds like?
If this post resolved your issue please click the 'This fixed my problem' button
 Adam Walker
 Plusnet Help Team
FarmerGiles
Dabbler
Posts: 15
Registered: ‎16-01-2011

Re: High numbers of CRC errors

My SNR margin seems to drop dramatically when its warm. Today, hottest day here so far this year, SNR margin dropped from 7.5dB at 07:00hrs to 2.5dB at 15:00hrs. Router (Speedtouch) stayed in sync but notched up 1.5million FECs in 8 hrs.
SNR currently 3.5dB (synced at 2080) with line up for c8 days.  Throughput down (currently) from 1.8mbps to 1mbps.
I realise its a long line.  My question was does this indicate a possible HR connection, trees rubbing etc somewhere or is this par for the course on a long line?
Latest Stats
Uptime: 8 days, 4:20:09
Modulation: G.992.1 Annex A
Bandwidth (Up/Down) [kbps/kbps]: 448 / 2,080
Data Transferred (Sent/Received) [MB/MB]: 168.21 / 941.14
Output Power (Up/Down) [dBm]: 11.5 / 17.0
Line Attenuation (Up/Down) [dB]: 31.5 / 63.5
SN Margin (Up/Down) [dB]: 6.0 / 4.0
Vendor ID (Local/Remote): TMMB / 
Loss of Framing (Local/Remote): 0 / 0
Loss of Signal (Local/Remote): 0 / 0
Loss of Power (Local/Remote): 0 / 0
Loss of Link (Remote): 0
Error Seconds (Local/Remote): 94,694 / 0
FEC Errors (Up/Down): 2,658 / 3,690,794
CRC Errors (Up/Down): 404 / 113,400
HEC Errors (Up/Down): 200 / 84,348
Thanks
MisterW
Superuser
Superuser
Posts: 14,581
Thanks: 5,413
Fixes: 385
Registered: ‎30-07-2007

Re: High numbers of CRC errors

Quote
SNR margin dropped from 7.5dB at 07:00hrs to 2.5dB at 15:00hrs.

That's quite a large change in SNR , typically you would hope for about 2-3db change from best to worst. At 2.5db I'm not surprised that you get lots of errors.
Getting BT to investigate it as a fault is going to be difficult I expect since the line is staying in synch and the speed is not unreasonable for that length of line.

Superusers are not staff, but they do have a direct line of communication into the business in order to raise issues, concerns and feedback from the community.

adamwalker
Plusnet Help Team
Plusnet Help Team
Posts: 16,871
Thanks: 882
Fixes: 221
Registered: ‎27-04-2007

Re: High numbers of CRC errors

Quote
My question was does this indicate a possible HR connection

Sorry not sure what you meant by that? Also if trees are rubbing on the line we can get that sorted pretty quickly if it can be proved that this is indeed happening.
If this post resolved your issue please click the 'This fixed my problem' button
 Adam Walker
 Plusnet Help Team
FarmerGiles
Dabbler
Posts: 15
Registered: ‎16-01-2011

Re: High numbers of CRC errors

Sorry, I meant are the higher temperatures affecting a high resistance connection somewhere along the line?
However, looking at the stats today it may in fact be tree problems as its not all that warm at the moment and the SNR margin has already dropped to 1.5dB which doesn't bode well for today.  Link is up at the moment but went down at about 04:00am.
Regards
jojopillo
Plusnet Alumni (retired)
Plusnet Alumni (retired)
Posts: 9,786
Registered: ‎16-06-2010

Re: High numbers of CRC errors

Hi FarmerGiles,
It's hard to know what to advise really as the line looks stable and your profile is 1750.
Jojo Smiley