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Standard User DougM
(member) Sun 19-Mar-17 15:58:12
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Recurring fault: CRC errors from 4am every couple of days


[link to this post]
 
My previously stable line has developed a fault. It runs with zero errors until 4am, then begins flooding with CRC errors. A resync stops the errors without changing any line characteristics: rate, margin, G.INP, bitswap all remain identical but the errors stop.

This would be okay if I could just resync every day and stop the errors, but over the course of a few weeks DLM responds by dropping the line rate. I dropped from 48 to 20Mbps and required an engineer visit to test the line and reset the DLM. It went back to 48 and started over. He couldn't find a fault but couldn't swap line pairs because the cabinet had no spare.

Any ideas how I get this resolved? I really don't want a monthly engineer visit just to reset DLM.

-==-
DougM
Standard User WilliamGrimsley
(committed) Sun 19-Mar-17 16:11:16
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: DougM] [link to this post]
 
It sounds like either something electrical coming on or a router issue, seen as the problem dissapears after a router restart. When the issue arises, please can you complete a quiet line test by dialing 17070 and selecting option 2, if you use a cordless phone any distant hiss is normal, but it's best to use a corded phone if you can.

Please can you post your line stats from the router? It may be worth uploading (if you haven't already) to MDWS: https://www.mydslwebstats.co.uk

Edited by WilliamGrimsley (Sun 19-Mar-17 16:15:15)

Standard User smurf46
(committed) Sun 19-Mar-17 17:52:43
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: DougM] [link to this post]
 
I'm experiencing something similar, over the last month. In my case line speed has dropped from 40, down to 36, 32 and now 30 Mbps. QLT did not indicate any line noise. Happens about once a week but on different days, and occurs from a hour or so, to several days up to a week before the line stabilises (errors disappear altogether, up to 10% packet loss disappears and max and average latency return to the same as minimum, which stays unaltered throughout according to TBBQM). Only affects download.

My Broadband Ping

Haven't reported anything as the line is still usuable (although there can be what I assumed was a separate problem with DNS resolver), and only seems to drop when it stabilises. Router reboots when it's occurring make no difference.

Stats taken from Fritz!:
Line stable since 6am today
Negotiated Connection Properties
Receive Direction Send Direction
Max. DSLAM throughput kbit/s 30000 6000
Min. DSLAM throughput kbit/s 128 128
Attainable throughput kbit/s 29996 6507
Current throughput kbit/s 29996 6000
Seamless rate adaptation off off

Latency fast fast
Impulse Noise Protection (INP) 44 0
G.INP on off

Signal-to-noise ratio dB 12 7
Bitswap on on
Line attenuation dB 24 24

Profile 17a
G.Vector off off

Carrier record A43 A43

Error Counter
Seconds With Not Remediable Errors (CRC)
Errors (ES) Many
Errors (SES) per
Minute Last
15 Minutes
FRITZ!Box 0 0 0 0
Central exchange 17 0 0.03 3

Only difference when line is misbehaving is that download attenuation rises to 37 and errors accumulate in the up to hundreds per hour at the Fritz!. Historically (for 6 years) download SNR has been in the 9-11dB range, at a consistent 40Mbps download.

I assumed it was just the underground line suffering from damp as winter turns to spring, and that (new) G.Inp was reacting to the line conditions. I was therefore rather hoping that warmer weather would eventually sort it out.

We see things not as they are, but as we are .
- Anais Nin

Edited by smurf46 (Sun 19-Mar-17 18:16:03)


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Standard User DougM
(member) Sun 19-Mar-17 18:01:46
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: WilliamGrimsley] [link to this post]
 
My Fritz!Box 7490 allows VDSL2 resync without a reboot. I tried the old Huawei and saw the same, so I'm back with Fritz since it's a far better solution.

During the errors the quiet line test is perfect; I have a wired phone just for this test.

I left the line erroring for the engineer to see, but as soon as he disconnected the router and connected his equipment the line bounced and the errors again cleared. The line test was perfect, but he changed the NTE as a matter of course.

Here's the outcome of the errors: ~5% packet loss until I resync.

https://community.plus.net/t5/image/serverpage/image...

-==-
DougM
Standard User DougM
(member) Sun 19-Mar-17 18:04:46
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: smurf46] [link to this post]
 
Interesting that we both use Fritz!Box. Are you using a 7490 on the latest code (6.80)?

-==-
DougM
Standard User smurf46
(committed) Sun 19-Mar-17 18:18:08
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: DougM] [link to this post]
 
In reply to a post by DougM:
Interesting that we both use Fritz!Box. Are you using a 7490 on the latest code (6.80)?


Yes, to both.

I recall a widespread problem with the 7390 firmware a couple of years ago, when it was incompatible with some BT firmware modification? Upload speeds collapsed, but as I recall neither TBBQM nor the Fritz stats indicated anything untoward, merely the upload synch speed collapsed. I suppose we have to wait and see whether anyone else reports!

We see things not as they are, but as we are .
- Anais Nin

Edited by smurf46 (Sun 19-Mar-17 18:52:18)

Standard User WilliamGrimsley
(committed) Sun 19-Mar-17 18:50:31
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: DougM] [link to this post]
 
I know. Sorry, I best leave this to the experts.
Standard User DougM
(member) Sun 19-Mar-17 19:39:27
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: smurf46] [link to this post]
 
There is an advanced option to roll back the DSL to the previous firmware's implementation; I'm going to try that next.

I'll also use the in-built option to report the problem directly to AVM. It's the last tab of the DSL section.

-==-
DougM
Standard User WilliamGrimsley
(committed) Sun 19-Mar-17 19:47:37
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: DougM] [link to this post]
 
I highly doubt that'll fix the issue, to say this is occuring at the same time of day. It's likely to be electrical interference from a device powering on.
Standard User DougM
(member) Sun 19-Mar-17 19:56:43
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: WilliamGrimsley] [link to this post]
 
Perhaps, but interesting that smurf46's problem also kicks off at 4am and is running identical hardware. Plus 4am's the time DLM seems to favour triggering changes.

Possibly a coincidence, but highly suspicious.

-==-
DougM
Standard User WilliamGrimsley
(committed) Sun 19-Mar-17 20:57:06
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: DougM] [link to this post]
 
His problem doesn't occur at 4 am.
Standard User DougM
(member) Sun 19-Mar-17 21:00:54
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: WilliamGrimsley] [link to this post]
 
His BQM shows the same pattern as mine; average latency jumps and packet loss run high from 4am until resync.

-==-
DougM
Standard User smurf46
(committed) Sun 19-Mar-17 21:27:35
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: DougM] [link to this post]
 
I'll report it to AVM too. The more reports they have the better. The attenuation change in my case (37 down to 24) makes me think it could be a firmware issue. I thought attenuation was the one thing that doesn't change (as it's based on distance to the cab) though I may be wrong.

Mine does start at 4am, (as on 3, 5 and 6 March), but also at other times, like the middle of the day too, most notably on the 8th from 10pm (when it wasn't cured by the reconnection the following day at 3am) and then continuous high latency until the 17th at around 5am (reconnection) following significant packet loss throughout the previous day.

I'll be interested to see whether your roll-back cures it. But if it's a firmware incompatibility I'd expect to see a number of other reports emerging as we did with the 7390s uploads. I think Plusnet have a number of Fritz! users, so it ought to show up on their forum..

The annoying thing for me is the on-going stepped throughput reductions, if they continue.

We see things not as they are, but as we are .
- Anais Nin

Edited by smurf46 (Sun 19-Mar-17 21:38:36)

Standard User DougM
(member) Sun 19-Mar-17 22:01:49
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: smurf46] [link to this post]
 
Reported and rolled-back to previous model firmware. I'll report back after a few days.

-==-
DougM
Standard User smurf46
(committed) Mon 20-Mar-17 09:27:32
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: DougM] [link to this post]
 
Ugh. Despite no errors being reported on the Fritz! over last 24 hours since last resync and no disturbance showing on BQM, there has been a further resync this morning with a drop in throughput down again to 28Mbps and SNR up to a record 13db.

It definitely seems that somewhere along the line the software has gone awry..

We see things not as they are, but as we are .
- Anais Nin
Standard User smurf46
(committed) Tue 21-Mar-17 10:18:02
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: DougM] [link to this post]
 
After our friend the massive errors returned at this morning's 4am event (without resync), after yesterday's clear day, I too did the DSL rollback option on the modem. Interestingly nothing changed apart from the error accumulation disappearing and the reported attainable download speed rose back to the traditional 42Mbps. Have to pray the DLM too will reset in time. As least throughput stays at 27Mbps and hasn't gone down further so far.

AVM now have two sets of data from me, before and after the rollback, so may be when they get around to it they can tell what is happening. IDNet (my ISP) support are about as much use as a chocolate teapot. They've melted. No response.

We see things not as they are, but as we are .
- Anais Nin
Standard User DougM
(member) Tue 21-Mar-17 10:29:35
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: smurf46] [link to this post]
 
I've been running the old firmware for 36 hours and have zero CRC errors. If it remains ~zero after 72 hours then I'd have exceeded the longest uptime using the latest firmware. Beyond that, it's a wait for DLM to respond.

I also noticed my attainable rate jumped back to 48Mbps after the rollback: but that may be down to changes in reporting since the latest firmware matched the banded rate, the previous firmware shows it varying as SNR margin changes.

-==-
DougM
Standard User freeola
(member) Tue 21-Mar-17 10:43:36
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: smurf46] [link to this post]
 
Nope, the Fritz stats clearly show a loss of tones in the upstream when this problem occurred. AVM did listen (eventually) and fixed this. Since the latest 7390 firmware it's been very stable. Hopefully they can do the same for the 7490.

Freeola
http://freeola.com - Broadband, Hosting & Instant Sites - Support
Standard User smurf46
(committed) Tue 21-Mar-17 10:59:22
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: DougM] [link to this post]
 
In reply to a post by DougM:
I've been running the old firmware for 36 hours and have zero CRC errors. If it remains ~zero after 72 hours then I'd have exceeded the longest uptime using the latest firmware. Beyond that, it's a wait for DLM to respond.

I also noticed my attainable rate jumped back to 48Mbps after the rollback: but that may be down to changes in reporting since the latest firmware matched the banded rate, the previous firmware shows it varying as SNR margin changes.


Ah. I had continuous uptime with the 6.80 firmware since it became available, before this problem occurred; and my attainable rate was always dynamic, though my maximum has I think always been banded (though it's supposed not to be according to my ISP sub). Not that it makes much difference in my case!

We see things not as they are, but as we are .
- Anais Nin
Standard User smurf46
(committed) Tue 21-Mar-17 12:00:40
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: freeola] [link to this post]
 
In reply to a post by freeola:
Nope, the Fritz stats clearly show a loss of tones in the upstream when this problem occurred. AVM did listen (eventually) and fixed this. Since the latest 7390 firmware it's been very stable. Hopefully they can do the same for the 7490.


Thanks, I may not have noticed as I don't have the upper frequency tones due to my line!

Is the 7390 firmware now publicly available, as I gave up when it was available only to selected users on request and I didn't get any response from AVM? If so, I could change back to the 7390 from the 7490 if the current roll-back of DSL firmware back doesn't sort it.

Anyone know if the 7390 will take a 7490 backup?

We see things not as they are, but as we are .
- Anais Nin
Standard User freeola
(member) Tue 21-Mar-17 12:47:56
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: smurf46] [link to this post]
 
Yes the latest firmware is 6.53.
I don't think the 7490 config can be ported to the 7390.

Freeola
http://freeola.com - Broadband, Hosting & Instant Sites - Support
Standard User DougM
(member) Wed 22-Mar-17 15:23:26
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: smurf46] [link to this post]
 
After 48 hours with zero errors, my line was rebanded from 32Mbps to 40Mbps. Still showing zero errors, so hopefully will continue to climb until I get back to 48Mbps.

-==-
DougM
Standard User smurf46
(committed) Fri 24-Mar-17 07:41:19
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: DougM] [link to this post]
 
Zero errors, but no change here.

I suspect that the Fritz! isn't good for UK lines, especially poor ones like mine. Reading between the lines, so I may be wrong of course, the Fritz! is very interventionist in trying to make the most of your line. Which is why we use it, of course. But are any telcos elsewhere in the world as interventionist in their line management as BT? They pride themselves on it. So there is obvious scope for conflict. And the BT DLM response to the conflict is to cap throughputs, a blunt and simple way to put an end to the "problem".

So it may be, that if it's speed you're after, don't waste your money on a Fritz!

There may be some evidence from the few BT-approved "firmwares". Difficult to get information, as they seem like state secrets (another possible BT trait, apart from the PR spin do any of us know what they are up to behind the scenes?) I suspect the partial spin-off of OpenReach too will not make much difference, it's about governance more than the practicalities. If you don't use the "approved" firmwares, it appears your throughputs are lower. Despite indicators of numerous routers being under test the list hasn't changed much in the last few years with it seems no additions, and the Fritz! isn't amongst them. Apparently the tests for compatibility are extensive and seem almost impossible to pass. Perhaps because BT's line management which must be a major part of the compatibility testing, intervenes so much. A mixed blessing, perhaps; for the rest of us.

We see things not as they are, but as we are .
- Anais Nin
Standard User lexden16
(committed) Fri 24-Mar-17 12:13:29
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: smurf46] [link to this post]
 
In reply to a post by smurf46:
Zero errors, but no change here.

I suspect that the Fritz! isn't good for UK lines, especially poor ones like mine. Reading between the lines, so I may be wrong of course, the Fritz! is very interventionist in trying to make the most of your line. Which is why we use it, of course. But are any telcos elsewhere in the world as interventionist in their line management as BT? They pride themselves on it. So there is obvious scope for conflict. And the BT DLM response to the conflict is to cap throughputs, a blunt and simple way to put an end to the "problem".

So it may be, that if it's speed you're after, don't waste your money on a Fritz!

There may be some evidence from the few BT-approved "firmwares". Difficult to get information, as they seem like state secrets (another possible BT trait, apart from the PR spin do any of us know what they are up to behind the scenes?) I suspect the partial spin-off of OpenReach too will not make much difference, it's about governance more than the practicalities. If you don't use the "approved" firmwares, it appears your throughputs are lower. Despite indicators of numerous routers being under test the list hasn't changed much in the last few years with it seems no additions, and the Fritz! isn't amongst them. Apparently the tests for compatibility are extensive and seem almost impossible to pass. Perhaps because BT's line management which must be a major part of the compatibility testing, intervenes so much. A mixed blessing, perhaps; for the rest of us.


I disagree. I have used a Fritz!Box for 6 years on both ADSL and FTTC lines. My 7490 is performing as it should on an 80/20 connection with Zen. The only significant change since installing 6.80 was a change in backhaul from WMBC to Zen GEA just over 9 days ago. I am now on an open profile with downstream fixed at 77961 and upstream variable at c.25000. Downstream SNR varies between 5 and 4 with steady line attenuation. My line errors for the past 9 1/2 days ( with no re-synchs) are:


FRITZ!Box 1242 0 0.13 0
Central exchange 60 0 0 0

I am though getting horrendous packet loss showing on my BQM which started about 10 days ago. My speed tests are fine and there are no issues with streaming or VOIP.

BQM Here

My line is connected to an ECI cabinet.

Edited by lexden16 (Fri 24-Mar-17 12:14:55)

Standard User smurf46
(committed) Thu 30-Mar-17 14:32:19
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: DougM] [link to this post]
 
Still no change here after a week. But at least speeds are stable at 27/6 with still no reported CRC errors at the modem and SNR stable at 13/6 . Huawei cab.

Warning, I tried to take the new 6.83 firmware, to see if there was a bug fix. It didn't look like it from the description. And I suspect I was right,my Fritz! 7490 running 6.80 wouldn't take it. Perhaps due to the DSL firmware rollback.

We see things not as they are, but as we are .
- Anais Nin

Edited by smurf46 (Thu 30-Mar-17 16:59:04)

Standard User smurf46
(committed) Tue 25-Apr-17 11:09:48
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Re: Recurring fault: CRC errors from 4am every couple of day


[re: smurf46] [link to this post]
 
Ugh! I succumbed to the latest 6.83 Fritz! firmware yesterday lunchtime. Sync fine until . . . . The old friends are back, from 2am this morning with continuous packet loss at 10% and continuous high peak latency, and multiple CRC errors.

I can only assume the Fritz! DSL firmware and DLM have fallen out again. Trying reverting the Fritz DSL firmware again, to see if that sorts it ... again; before DLM starts crashing the sync speeds again.. (Huawei cab). Edit: definitely looks like it, after the reset reboot the effect on the TBBQM is like switching all the problems off at once.

We see things not as they are, but as we are .
- Anais Nin

Edited by smurf46 (Tue 25-Apr-17 11:16:54)

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