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CRC errors - advice on what I am seeing

dc8
Grafter
Posts: 60
Registered: 06-01-2014

CRC errors - advice on what I am seeing

Have had a few problems recently with my line and after lots of effort from PN and others on the forum things had settled down quite nicely.
However, yesterday, Sunday, I suddenly started getting a large amount of CRC errors which has continued since and is still the same as I type this.
Attached are 3 graphs from DSLstats which shows what was happening and how things look now.
First graph show normal values and was in the hour before the second graph whch is where things had started to go weird and the last one was from earlier this morning. All the graphs I have overnight show exactly the same sort of output with CRC errors racking up while I was soundly asleep and the laptop was basically idle.
Could anyone suggest what might have caused this dramatic change in the CRC errors that I now see ?
Nothing has changed in the house here, but obviously I don't know if someone else has done anything lol !!
10 REPLIES
cedlor
Grafter
Posts: 685
Thanks: 2
Registered: 02-04-2015

Re: CRC errors - advice on what I am seeing

Do you have the SNRM graphs from the same periods?
dc8
Grafter
Posts: 60
Registered: 06-01-2014

Re: CRC errors - advice on what I am seeing

dc8
Grafter
Posts: 60
Registered: 06-01-2014

Re: CRC errors - advice on what I am seeing

And, just to make things more interesting here is what happened a few minutes ago !!
dc8
Grafter
Posts: 60
Registered: 06-01-2014

Re: CRC errors - advice on what I am seeing

JayG
Aspiring Pro
Posts: 915
Thanks: 66
Fixes: 2
Registered: 30-10-2011

Re: CRC errors - advice on what I am seeing

Just over a year ago I had a couple of bouts of CRC errors of the order of millions in a few hours which certainly did drop the connection - one of those instances was overnight when I wasn't 'actively' using the connection. No real explanation was ever found, and it hasn't happened again since, although I do monitor the connection routinely and there are still bursts of REIN interference from time to time, luckily not of the same magnitude as before, but equally difficult to pin down.
I'd think about replacing your ADSL filter/s to see if that makes a difference - your CRC errors aren't high enough to drop the connection at the moment, and the corresponding dips in SNR don't look too drastic either.
Not saying you don't have a fault of some description, but equally the bursts of errors could just go away as mysteriously as they appeared.
dc8
Grafter
Posts: 60
Registered: 06-01-2014

Re: CRC errors - advice on what I am seeing

Thanks for the reply JayG,
I must admit I am a bit paranoid at the moment after all the problems I had during the last month  Cheesy
I have a brand new XF-1e Professional Microfilter and a new low loss cable from the same place so I think they should be OK - well, hopefully they are !!
Really just wanted to be sure that the errors wouldn't start to cause disconnection problems and the subsequent loss of speeds that I had been suffering.
JayG
Aspiring Pro
Posts: 915
Thanks: 66
Fixes: 2
Registered: 30-10-2011

Re: CRC errors - advice on what I am seeing

Having gone through the trauma of broadband meltdown, paranoia is the price you can expect to pay for being unable to switch off software monitoring of the average semi clapped out BTW phone/ADSL connection!  Cheesy
Community Veteran
Posts: 19,100
Thanks: 437
Fixes: 21
Registered: 31-08-2007

Re: CRC errors - advice on what I am seeing

I think you possibly mean switching off DLM, but that's a much longer story which I won't rant on about here. I think there are few (if any) Plusnet faults staff that know/understand all aspects related to that and/or customised profiles. We certainly don't know, despite our best efforts to find out.
My only comment about the CRC errors so far, is look at the Upstream SNRM to see if that shows up any clues (I know this is downstream), also keep an ear on the QLTest. This might be some fairly narrow band interference rather than general line noise/interference
The only other point to note is that DSLstats fills the 582n log with login/out entries so should you need to look at anything else the log may have told you, generally it won't be there are the data will have been overwritten.
dc8
Grafter
Posts: 60
Registered: 06-01-2014

Re: CRC errors - advice on what I am seeing

Thanks for the reply A.
I was just about to post to say that exactly what I was worried about has just happened - please see attached graphs.
This resulted in a disconnect and a re-connection some 500 lower than before the CRC spike. There a very few spikes on the upstream and I will keep a closer look on these in the future.
Have just looked at the QLN graphs and they seem to have show nothing in them at all and all the text files just have one entry - blank ? The option to create them is ticked within the config but is greyed out so not sure what that means  ?
Thanks for any other pointers you might be able to give on what I should be looking for to try and track this down.
Community Veteran
Posts: 19,100
Thanks: 437
Fixes: 21
Registered: 31-08-2007

Re: CRC errors - advice on what I am seeing

The reason for the drop in speed is of course that your SNRM has been dropping due to the increase in propagation since dusk. With 2 dB less margin (2dB more noise), when the connection dropped it resyncs back at the Target SNRM (currently 9dB it seems), so you get the slower speed.
A resync in daylight hours when you see the SNRM rise to around 11dB will cure that issue.
The burst in CRC looks like a SHINE event but the cause could still be from the same source as the previous sustained CRC errors, which might be classed as REIN. As you know that can often cause a reduction in SNRM, but I guess that when it's not then maybe the Modem is doing very well with bit swapping.
Haven't had any lightning at all at that moment?
I think I would be looking for things maybe like an arcing contact (eg.thermostat or bad electrical connection), maybe discharge lighting being switched on (possibly not functioning as it should), the range of equipment could be endless if there's some sort of bad connection or fault.
Did you switch anything on at around the time the level went up on the previous graphs? Did you switch anything off around the time it went down? These are the sort of things to start keeping an eye on.