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Standard User rnewfie
(member) Wed 29-Jan-14 14:53:29
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Millions (literally) of CRCs Reported on Router

[link to this post]
Ever since changing ISPs, I have been using their new router, a TG582N.
Within a few weeks I noticed that it was reporting 3600 CRCs per minute. This was over a period of several days, but by re-booting the router, it stopped and reported a normal one CRC per 100 seconds or so.
The only reason I noticed this was that general browsing speeds were sluggish. I did a few speed tests and throughput was around 800k, previously around 4000k. This on a connection speed of around 5200k

Over a period of several weeks, the situation is this :-
If I run this router in ADSL2+ mode, after a few hours, it starts producing exactly 3600 CRCs per minute, which goes on forever, or until I re-boot the router. If it were a 'real' line problem, then it wouldn't stop when the router re-booted, nor would it be consistently 3600 per minute.
When I reported this to my ISP, they supplied a replacement TG582N router - This does exactly the same.
If I run these routers in ADSL2 mode, then there are no CRCs produced.
The ISP has increased the SNRM to 9.0 from 6.0 to see if that was the problem - It still produced 3600 CRCs per minute on an increased margin.

I have three other routers - A TG585v6, a TG585v8 and a DSL-2640B - None of these produce CRC errors in ADSL2+ mode.

I am currently running the DSL-2640B router on an SNRM of 3.0 and over a period of 76 hours, the router has produced 5790 CRC errors (One per 47 seconds) - Not brilliant, but the SNRM is always between 1.1 and 2.8. The connection speed is up to 5600k as well due to the low SNRM.

My question is this - Why is it that the TG582N router produces a consistent 3600 CRCs per minute when in ADSL2+ mode and no other router on the same line does, nor does this router do it in ADSL2 mode?

I have reported all of this to my ISP and their last statement was ''you have clearly shown, is an issue with the Technicolor router when running as ADSL2+.'' They also suggested upgrading the router to the latest firmware, but it is already on it.
They also said, ''Unfortunately we do not have a direct route of support with Technicolor''

Anyone got any suggestions?
Standard User b4dger
(knowledge is power) Wed 29-Jan-14 15:35:29
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Re: Millions (literally) of CRCs Reported on Router

[re: rnewfie] [link to this post]
Strange one - your line doesn't seem to like that chipset/firmware?!

Is your line via BTw or LLU?
It's also worth mentioning the ISP in case it gives a clue to the issue or helps others.

Have you tried using the TEST socket just to see if that should change the situation?

If you've found a router that's happy I would stick to that smile

Standard User rnewfie
(member) Wed 29-Jan-14 16:11:45
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Re: Millions (literally) of CRCs Reported on Router

[re: b4dger] [link to this post]
It's BTw via Plusnet.

I haven't tried the test socket as
1) The extension wiring is perfect (been tested to destruction by Openreach for a different reason!),
2) Will need to move the router and I didn't want any unnecessary re-syncs as Plusnet have done an SNR reset and I'm on a training period.

The DSL-2640B router I am on is fine, except that it doesn't support wireless-n, but I'm not sure if running on G is much of a restriction.

All of the routers I have are Broadcom based, so I wouldn't have thought there was an incompatibility.

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Standard User rnewfie
(committed) Mon 19-Oct-15 14:30:27
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Re: Millions (literally) of CRCs Reported on Router

[re: rnewfie] [link to this post]
I just came across this thread and realised that I forgot to post what the problem is with this router.

Just in case anyone is having a similar problem, I found that the magic number of 3600 CRCs per minute is indeed significant. It is the number of Super Frames generated to allow synchronisation on an ADSL link.
There are 60 per second, i.e. every 16.667 milliseconds and therefore 3600 per minute. For those techies, you may have seen the figure of 17 milliseconds quoted, this is a rounding of the above.

Under certain conditions, I know not what, the router reports Super Frames as CRCs. Apart from the screwed statistics, the router seems to work quite well.
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