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Author Topic: Strange happenings on my line yesterday  (Read 51520 times)

broadstairs

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Re: Strange happenings on my line yesterday
« Reply #30 on: May 28, 2016, 08:07:25 AM »

I woke up this morning to find that DLM had intervened on my line with INP of 5 and a Delay of 10. Now this is only on the downstream which is not the direction which is causing trouble, it is upstream which is the problem. This seems to me to be a somewhat lacking implementation in DLM trying to fix a problem by hammering the downstream when it is NOT in trouble, I can understand that more often downstream can be problematic but to ignore the upstream when changing the parameters seems to me to be a flawed implementation.

Because of the situation at home this week I have had to delay my engineers visit to Thursday afternoon so I'm going to have to live with this for some time yet, but if DLM continues to hit downstream I dread to think what it will be like by Thursday.

Stuart
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broadstairs

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Re: Strange happenings on my line yesterday
« Reply #31 on: May 28, 2016, 11:18:49 AM »

DLM has intervened again with a delay of 13 d/s but the U/S is suffering once again. Bottom line is that DLM is not making things better..... u/s gets worse and d/s gets penalised....

Stuart
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WWWombat

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Re: Strange happenings on my line yesterday
« Reply #32 on: May 28, 2016, 11:55:11 AM »

Your downstream is just as broken as the upstream - the sync speed adjustments mirror each other perfectly. Yes, your upstream speed drops to almost zero at these times, so is worse /relatively/, but the two are failing in tandem.

If I look at the behaviour, and the ES rates, I'd say that DLM is responding to the number of resyncs you are getting, rather than the ES rate. In fact, looking at the raw CRC count instead of ES, you can see that CRCs appear as spikes - but only at the precise point that a resync happens too. The graphs only show downstream CRC's, even though the ES graph suggests upstream ones must be happening too - I can't reconcile that.

The SES graph also shows a lot of behaviour, where downstream is worse than upstream. SESs are likely to influence DLM too, but we have insufficient data or evidence to figure this out, as they happen relatively rarely. Suffice to say that these, when they happen regularly, are bad news.

Whatever is going wrong with your line, it isn't your bog-standard REIN or SHINE. And that's why DLM isn't handling it too well - it is designed to cope with those phenomena, but not the kind of problem your line is exhibiting.

I just hope it keeps showing the problem when the engineer turns up...

(Edit: Add graph showing CRC vs resync, and up/down mirroring)
« Last Edit: May 28, 2016, 11:58:08 AM by WWWombat »
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WWWombat

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Re: Strange happenings on my line yesterday
« Reply #33 on: May 28, 2016, 12:20:03 PM »

Your downstream is just as broken as the upstream - the sync speed adjustments mirror each other perfectly. Yes, your upstream speed drops to almost zero at these times, so is worse /relatively/, but the two are failing in tandem.

I was just investigating this aspect further ...

Yesterday, I looked at the Hlog graph, and could see that, when things went wrong, it was roughly 3dB down across the spectrum. Not enough to lose almost all of the upstream.

Just now, I looked at the bit-loading for two occasions (midnight 27th May, and midday 27th May) - times that were largely "perfect" and "terrible". The bitloading downstream is roughly 2 bits lower in D1 and D2, and 1 bit lower in D3. This is about right for the change in Hlog.

However, upstream gets a much worse deal - it loses as much as 4 bits from U1 and 6 bits from U2, leaving U0 as the only loaded spectrum. That is very disjoint from the alteration in Hlog, so I set about figuring why.

There appears to be no change in QLN, so it isn't down to extra noise.

However, there are large variations in upstream power. Sometimes dropping by around 10dBm. *That* would have a large impact on upstream speed.

Power variation normally occurs as part of the upstream power backoff mechanism, which prevents nearby modems from drowning out distant modems. I could expect slight power increases when attenuation increases - but we're getting the opposite here (although we do see power increase sometimes).

Can anyone else offer an explanation?
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WWWombat

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Re: Strange happenings on my line yesterday
« Reply #34 on: May 28, 2016, 12:23:13 PM »

Whatever is going wrong with your line, it isn't your bog-standard REIN or SHINE. And that's why DLM isn't handling it too well - it is designed to cope with those phenomena, but not the kind of problem your line is exhibiting.

Remember too that DLM is designed to respond to errors and resyncs, and not to excessively low speeds. Upstream is causing some errors, but perhaps not enough to invoke DLM. When a resync happens, upstream ends up on a low speed for unknown reasons - but that isn't enough, by itself, to trouble DLM further.
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Chrysalis

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Re: Strange happenings on my line yesterday
« Reply #35 on: May 28, 2016, 06:39:21 PM »

when is engineer coming? if not then get it booked.
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burakkucat

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Re: Strange happenings on my line yesterday
« Reply #36 on: May 28, 2016, 07:09:33 PM »

when is engineer coming?

This coming Thursday afternoon, if I have correctly understood what Stuart has written.
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broadstairs

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Re: Strange happenings on my line yesterday
« Reply #37 on: May 28, 2016, 09:49:07 PM »

Correct  ;)

Stuart
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broadstairs

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Re: Strange happenings on my line yesterday
« Reply #38 on: May 28, 2016, 11:21:26 PM »

I decided tonight to put my HG635 back instead of the ZyXEL for a couple of days just to make sure these problems were not the router. I dont think they are but I though trying another router would not be a bad idea. It is still running DSLStats to MDWS.

Stuart
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daveesh1

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Re: Strange happenings on my line yesterday
« Reply #39 on: May 29, 2016, 12:32:27 AM »

Time will tell. All looks ok at the moment
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broadstairs

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Re: Strange happenings on my line yesterday
« Reply #40 on: May 29, 2016, 07:56:04 AM »

Yes but it usually is not too bad overnight. I am having a few issues with the HG635 getting stats, for some reason DSLStats is failing to login some times, dont know why - maybe Eric might have an answer. The real test will be during the day today and if it still gives me grief then I'll put the ZyXEL back in.

Stuart
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Chrysalis

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Re: Strange happenings on my line yesterday
« Reply #41 on: May 29, 2016, 11:37:23 AM »

Correct  ;)

Stuart

live webcam during visit?
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broadstairs

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Re: Strange happenings on my line yesterday
« Reply #42 on: May 29, 2016, 01:06:29 PM »

Well my line is going down hill like before so it's not the router. I'll put the ZyXEL back later today.

Stuart
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broadstairs

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Re: Strange happenings on my line yesterday
« Reply #43 on: May 29, 2016, 02:43:40 PM »

Since the fault was still there with the HG635 plus some unusual errors with it the ZyXEL VMG8924-B10A is back up and running.

Stuart
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Chrysalis

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Re: Strange happenings on my line yesterday
« Reply #44 on: May 29, 2016, 04:12:30 PM »

I suggest you stop swapping kit round in the days leading up to the visit, so they cannot blame that for your issues.
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