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Author Topic: Would appreciate some wisdom regarding my VDSL line - Thanks  (Read 1869 times)

roadsnail

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Would appreciate some wisdom regarding my VDSL line - Thanks
« on: December 28, 2017, 06:16:44 PM »

Background Info:- ISP - Sky  40/10 Unlimited Fibre (FTTC)
Modem/Router - Billion 8800AXL Connected to ECI Cab
Distance to cabinet approx 800m (rounded up to allow for cables up/down poles). According to BT OR man. some of the cable run is Aluminium, although approx 150m of aluminium was swapped for Copper back in the Autumn) with my attenuation figures dropping from around 25.7 to 25.2dB

Have had this service for around 3 years now. Speeds have not been great (varying between 17.5 - 20.0 Mbps throughput DS and 4.5Mbps US), but have been consistent.

Just before Christmas, noticed DLM kicking in and speed gradually dropped to under 10Mbps DS, so logged a call with Sky who blamed my internal wiring. But that's another saga best left for another day.

Upshot - BT Openreach attended (15th Dec) and diagnosed high resistance joint on my line using his TDR, which he located and attended to. He was able to reset the line (to fast path?) and tested for speed and CRC's. He declared it good with a connection speed of just over 21.5Mbps down and very few CRC's (at the time).

I subsequently started monitoring line stats and logging to MDWS (username Scarab). I didn't expect my line to stay on fast path but have been surprised at the very high CRC bursts along with error seconds ES and severe error seconds SES counts following a few line resyncs and various levels of interleaving being applied.

I don't have MDWS stats dating back to when I received a more stable 17.5 to 20Mbps connection BUT I am fairly certain I never saw such huge bursts of ES/SES! I seem to remember the ES counters going into the low 100's (and SES being far less) even when I rarely reset the Billion's counters.

I am wondering if my line is suffering from random noise burst problems (thus the bursts of CRCs followed by stable CRC counts)? I can't think of anything that has changed internal to my house to be causing noise.  I guess noise could be injected virtually anywhere along the cable run but I cannot identify anything obvious - ie roadworks, generators running etc

My other theory for the change I have seen is that the aluminium to copper change a couple of months ago saw me connected to a pair that is just suffering from a higher level of crosstalk than previously. If so, I want my old aluminium pair back! Would crosstalk manifest as bursts of high levels of CRCs? Or would the CRC errors tend to occur at a constant rate?

I am guessing that DLM is doing its thing, but I would appreciate it if some of the Kitz 'gurus' could cast an eye over the stats before I refer this back to Sky again.

Thanks.

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Black Sheep

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Re: Would appreciate some wisdom regarding my VDSL line - Thanks
« Reply #1 on: December 28, 2017, 06:58:21 PM »


Just before Christmas, noticed DLM kicking in and speed gradually dropped to under 10Mbps DS, so logged a call with Sky who blamed my internal wiring. But that's another saga best left for another day.





I would humbly suggest before you/we go looking at possible Openreach network issues, you concentrate your efforts into making certain your internal wiring set-up is fully optimised.
This is more likely to be the reason behind the errors you are seeing, working on a percentage basis.

Plenty of contributors on here that will help you through this.  :) :)
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Black Sheep

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Re: Would appreciate some wisdom regarding my VDSL line - Thanks
« Reply #2 on: December 28, 2017, 06:58:51 PM »

PS - welcome to the forum.  :)
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roadsnail

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Re: Would appreciate some wisdom regarding my VDSL line - Thanks
« Reply #3 on: December 28, 2017, 07:18:45 PM »

Thanks Black Sheep for taking time to read and post.

My internal wiring is actually fine. The BT cable enters my house and goes straight into a filtered faceplate fitted by BT OR about 2 years ago.
There is no star wiring. My router plugs directly into the DSL 'filtered' port of the faceplate.

The only reason I mentioned the Sky comment regarding wiring issues was because their 'remote diagnosis' suggested internal wiring - then promised a Sky engineer who never turned up. Then Sky booked an Openreach engineer who confirms that there are no internal issues. Not surprising given nothing has changed.

But thanks for mentioning this.
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Black Sheep

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Re: Would appreciate some wisdom regarding my VDSL line - Thanks
« Reply #4 on: December 28, 2017, 07:23:17 PM »

Aha, I see ............ no worries, I just thought it best to bottom the 'internal installation' out first. with it being the usual culprit ... but it would seem you're well ahead of the game !!  ;) ;D

I'll hand you over to one of our expert stat-analysers now ..... sit back and be amazed.  ;D ;D
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roadsnail

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Re: Would appreciate some wisdom regarding my VDSL line - Thanks
« Reply #5 on: December 29, 2017, 01:10:14 PM »

Update: DLM intervened earlier today at 10.05 just after a burst of CRC errors, so connection speed down to 15000kbps.

Looking at the past 48 hours CRC graph on MDWS this is typically what I am seeing. Very few DS/US CRC errors for several hours, then CRCs go crazy, then all quiet again for several hours then DLM intervenes.

Guess I'll have to go back to Sky/OR and show them what I am seeing here. All I know is that my line never used to exhibit such extremes of CRC/ES/SES errors before the 'line improvements' made back in the Autumn. Maybe there is an intermittent joint somewhere on the way back to the cabinet?



 
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Deathstar

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Re: Would appreciate some wisdom regarding my VDSL line - Thanks
« Reply #6 on: December 29, 2017, 03:15:42 PM »

You don't happen to have any Power Line Adapters on your network do you?

Sent from my SM-G930F using Tapatalk

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roadsnail

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Re: Would appreciate some wisdom regarding my VDSL line - Thanks
« Reply #7 on: December 29, 2017, 05:20:13 PM »

@Deathstar....No.. good thought though. Have seen these clock up CRCs like crazy on a friend's router.
Nothing has changed for ages on my network.
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Black Sheep

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Re: Would appreciate some wisdom regarding my VDSL line - Thanks
« Reply #8 on: December 29, 2017, 05:48:33 PM »

Maybe there is an intermittent joint somewhere on the way back to the cabinet?



 

When you use the landline phone, can you hear any noise ..... such as background hissing, or a slight crackling ???

If you dial 17070 then listen to the automated 'Hi, I'm Zoe .....' then press '1' and she will read back your landline number to you. Keep repeating this for a few minutes and see if this has any effect on your connection ??

Worth making a note of the time you perform this action, then you can retrospectively check your router/DSL logs to see if the errors did noticeably increase as a result of using the landline ??

This would go some way into determining if there is indeed a high resistance (HR as we all refer to it), connection.  :)
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roadsnail

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Re: Would appreciate some wisdom regarding my VDSL line - Thanks
« Reply #9 on: December 30, 2017, 03:07:02 PM »

@Black Sheep - Thanks for the info on quiet line testing. I carried this out before the BT OR guy found the bad joint on the 15th Dec and the line sounded quiet then. I have experienced really severe problems high resistance problems in the distant past and the line has always sounded crackly, but not this time. I also did a quiet line test after he fixed the problem, and once again all sounds good. I will try once more, but will be surprised if I can hear anything. I suspect any noise is up in the much higher bands/frequencies.

I checked MDWS a few minutes ago and can see that the line seems stable at 15000kbps and FEC seems to be doing its job.

I suspect that the line is just not capable of better speeds for whatever reason.. crosstalk, random noise problems, whatever .. and I will have to live with it.

Thanks to those that have taken an interest in this and a Happy New year to all.

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