CRC/FEC/HEC errors

builder22 · 14 Feb 2016 at 12:05

what is an acceptable amount of errors? syncing at 16000

had a problem with the phoneline (no dial tone + internet almost stopped) which is now fixed but i don't think the errors were as high as this before.

here's the stats, connected for 2days 15 hours at this point

Modulation : ADSL2+
Annex Mode : Annex A/L
Line State : up
Lan Tx : 4076716
Lan Rx : 2523325
ADSL Tx : 2271623
ADSL Rx : 3556035
CRC Down : 0
CRC Up : 134
FEC Down : 0
FEC Up : 265
HEC Down : 220
HEC Up : 0
SNR Up : 7.0
SNR Down : 8.3
Line Attenuation Up : 13.0
Line Attenuation Down : 21.4
Data Rate Up : 1131
Data Rate Down : 16008

Rroff · 14 Feb 2016 at 12:08

Depends on your use a bit - that level looks reasonably low for 2-3 days uptime - ideally lower or 0 but doesn't look high enough that it would impact on most uses including online gaming within reason.

builder22 · 14 Feb 2016 at 12:36

thanks

it's overhead lines that go to the house - I noticed there are a few branches in contact with the line so when it's windy the line moves with the branches.
I thought that was what was causing the no dial tone fault but it was a fault on the line somewhere on the main road - could the branches have anything to do with the errors?

also - I used to have the stability adjustment set to -2db on the router (Asus N55-U) and it was syncing about 18000 but since the fault was fixed it needs to be set to -3db to keep the SNR figures reasonable

thing is it works and is within the 'acceptable speed range' so just have to accept that's the way it is now?

MissChief · 14 Feb 2016 at 13:51

As above, negligible for the up time. Line stats look ok as well.

builder22 · 14 Feb 2016 at 14:05

thanks - another query....

on the BTWholesale speedtest site, for the upload speed the results come back as....

0.83 Mbps Max Achievable Speed
Upload speed achieved during the test was - 0.94Mbps
Additional Information:
Upstream Rate IP profile on your line is - 0.83 Mbps

was wondering if that had anything to do with the 'up' errors, as it's running faster than the max speed?

Rroff · 14 Feb 2016 at 14:10

builder22 said:
it's overhead lines that go to the house - I noticed there are a few branches in contact with the line so when it's windy the line moves with the branches.
I thought that was what was causing the no dial tone fault but it was a fault on the line somewhere on the main road - could the branches have anything to do with the errors?

I've wondered about that - we have a tree between us and the pole (unfortunately on neighbours land) and it always seems when it grows up enough that the line passes through the branches that our connection drops a bit compared to what it normally is - bit of a pain as it usually takes BT coming out with a cherry picker to sort it once it gets to a point its causing problems with the box.

builder22 · 14 Feb 2016 at 14:21

maybe act as a bad earth or something like that?
do they just trim the trees when they come out or do they have to do something with the connections on the mast/junction box? too

builder22 · 20 Feb 2016 at 10:11

since the last time I posted here I've noticed my sync speed has increased - I haven't altered anything, not even rebooted the router

looking at the Line Data on my ISP's website it shows the noise margin was reset - what exactly does that mean - what does BT do to the signal to allow it to sync higher?

the errors are now much higher too....

this is after 4 days uptime

Modulation : ADSL2+
Annex Mode : Annex A/L
Line State : up
Lan Tx : 14757501
Lan Rx : 8443799
ADSL Tx : 3322990
ADSL Rx : 5797461
CRC Down : 0
CRC Up : 963
FEC Down : 0
FEC Up : 9426
HEC Down : 1477
HEC Up : 0
SNR Up : 6.8
SNR Down : 6.5
Line Attenuation Up : 13.0
Line Attenuation Down : 21.4
Data Rate Up : 1131
Data Rate Down : 17938

Rroff · 20 Feb 2016 at 10:15

Noise margin reset probably means that the line management has seen a specific period of time with minimal errors and reset to the default target of 6db - if a line is having problems the target SNR can be adjusted upwards which results in a lower sync speed but usually a more stable line.

A couple of times there has been a problem with our line which is usually due to a mixture of someone carelessly working on the pole (not sure what happens exactly but if they don't do their job properly our line can get stuck in the door to the box or something) and the branches in the way when they grow up longer - we've had to get BT to send someone out to look at it who then orders a cherry picker to cut the branches back as its the only way it can be resolved after awhile.