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CRC errors etc ???

karlos103
Grafter
Posts: 106
Registered: 26-01-2014

CRC errors etc ???

Hi all
Keep having DSL disconnects ...seems to happen when it rains ....plus in openreach modem i have a lot of error in the WAN xDSL tab -
CRC errors  2396 downstream / 0 upstream
FEC errors      47  downstream / 5 upstream
HEC errors  592  downstream / 0 upstream
Does anyone know what these mean and if i should worry ?
Any help most appreciated
Karl
11 REPLIES
Superuser
Superuser
Posts: 12,230
Thanks: 3,541
Fixes: 22
Registered: 22-08-2007

Re: CRC errors etc ???

Hi,
These mean that your modem has needed to "recover" data using various error correction methods.  These arise from noise on the line inserting errors into the message can cause delays due to processing time and retransmissions.
Without the full set of modem stats, it is not possible to tell if these error levels are significant or not.  If they arise form a few minutes of connectivity, then they are more significant that if they arose from days of connectivity.

The coincidence of DSL disconnect and rain rather suggests that there might be bad joints on your line.  Does you phone line crackle when you lift the handset?  try a quiet line test 17070 option 2.  Are you ADSL or FTTC?
Can you please post all of the DSL stats you can obtain from your router please?  This will provide the right information upon which to offer guidance.
leader
Grafter
Posts: 261
Registered: 02-02-2013

Re: CRC errors etc ???

Are you on an ECI street cabinet ?
(Its a Common  issue when unlocked HG612's are used on ECI (IFTN) MSAN's.)
karlos103
Grafter
Posts: 106
Registered: 26-01-2014

Re: CRC errors etc ???

hi
im on fibre broadband ...don't know what eci  cab is lol ....sorry new to this .
What stats do you need from my unlocked modem ??
Many thanks
karl
Superuser
Superuser
Posts: 12,230
Thanks: 3,541
Fixes: 22
Registered: 22-08-2007

Re: CRC errors etc ???

Karlos,
I'm not familiar with the "innards" of FTTC, beyond knowing that on the D-Side it is susceptible to the same bad joint issues as ADSL, so sorry that I cannot assist further.
karlos103
Grafter
Posts: 106
Registered: 26-01-2014

Re: CRC errors etc ???

thanks for the info ...to me seems more than a coincindence thats DSL disconnects when it rain ....broadband been fitted for a month now and seem to have a lot of disconnects ...tried a homehub 5 to start with and disconnected loads of times but heard there is an issue with them disconnecting ....so turned to original equipment and even that still does it .....but everytime i look at logs and see dsl disconnects ...its around same time as it starts to rain .
Also when BT engineer came to fit my fibre broadband he said we had a fault ...i said i had no idea as old adsl broadband and phone seemed ok ....he said nothing about it afterwards .....so maybe we do have an issue with line .
Will have to get them to come and look at line now as seems like its nothing to do with the equipment im using as tried different ones and still happens
Many thanks
karl
dragon2611
Grafter
Posts: 283
Registered: 20-10-2013

Re: CRC errors etc ???

Quote from: Townman
Hi,
These mean that your modem has needed to "recover" data using various error correction methods.  These arise from noise on the line inserting errors into the message can cause delays due to processing time and retransmissions.

That's the FEC errors, i.e errors that are corrected by the interleaving/forward error correction, they won't cause any extra delays other than the delay added by having the interleaving on.
The CRC errors however will be packets that failed the CRC check and couldn't be fixed by FEC and therefore will have been dropped and will need re-transmission.
HEC errors are where the ATM header had errors and had errors, this will cause the ATM cell to be discarded (Note: I had to google this one as I couldn't remember it)
Also those error counts are meaningless without a connection uptime, there is likely to be some transmission errors it's the nature of DSL shoving high speed data down an infrastructure that was never designed for it
Mine is
Quote
Line rate (kbit/s) 79987 19999
CRC errors 0 0
FEC errors 3927 4240
HEC errors 10429 0

On first glance it doesn't look great,
But my DSL uptime is 8043173  Seconds (I think) which I believe to be 93 Days  Shocked
System uptime for the modem is
System up time 93 days 2 hours 14 minutes 29 seconds
So actually my error counts are Tiny when taken as a %age of packets that would have gone through that modem.
That's with a unlocked HG612 on FTTC - If you want to unlock the modem so you can get at the stats I'd always advise trying to get a second one from somewhere as then you have an untouched one to put back on if you get a fault  Wink
karlos103
Grafter
Posts: 106
Registered: 26-01-2014

Re: CRC errors etc ???

i unlocked mine this week , but have locked version of firmware to put back on if need be ...but going to get an asus dsl modem router this week anyway .
as for uptime it say 28024 ....last time dsl disconnected was this afternoon about 3pm
karl
Superuser
Superuser
Posts: 12,230
Thanks: 3,541
Fixes: 22
Registered: 22-08-2007

Re: CRC errors etc ???

@Dragon,
Thank you for the expansion on the recovery approach for each of the error types.
One minor quibble though; if there are substantial FECs modems can become overloaded with the over head of processing them.  I have seen the TG's web interface become completely non-responsive in the presence of a high FEC incidence rate.  Any error correction process adds a delay at some level - granted some more than others, but error correction is not a zero cost game.
karlos103
Grafter
Posts: 106
Registered: 26-01-2014

Re: CRC errors etc ???

Crc error just gone up by 500 in last 20 mins
leader
Grafter
Posts: 261
Registered: 02-02-2013

Re: CRC errors etc ???

Quote from: karlos103
hi
im on fibre broadband ...don't know what eci  cab is lol ....sorry new to this .

They are a handy tool those unlocked hg612 as dragon2611 notes...
(Usual  command via telnet)
sh
xdslcmd info --vendor
(The asus might have the same issue as its also broadcom based , its an eci IFTN:0xb203   cabinet:?:
(Lots of good info on the Be usergroup site )
http://beusergroup.co.uk/technotes/index.php?title=Diary_of_an_FTTC_Install
karlos103
Grafter
Posts: 106
Registered: 26-01-2014

Re: CRC errors etc ???

Right here is what it says when enter xdslcmd info --vendor
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max:    Upstream rate = 22090 Kbps, Downstream rate = 81264 Kbps
Path:  0, Upstream rate = 17000 Kbps, Downstream rate = 48865 Kbps
ChipSet Vendor Id:    IFTN:0xb203
ChipSet VersionNumber: 0xb203
ChipSet SerialNumber:  5501540049
Hope that helps .....also noticed speed has dropped a lot because of the disconnects , used to have
around 70mb download ....slowly got worse !!