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Author Topic: ADSL2 line problems  (Read 4602 times)

g3uiss

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Re: ADSL2 line problems
« Reply #30 on: June 21, 2018, 12:20:00 PM »

Just had a look.   Those missing tones are still there in the same place. 
Considering Interleaving is now switched on, its done absolutely nothing to help.     
In fact if anything, your CRC's and Err Secs appear to have increased and you've also had some SES errors.  :(   Lower SNRM is noted.

:'(

Would you think thatís an exchange issue as nothing changed locally.
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kitz

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Re: ADSL2 line problems
« Reply #31 on: June 21, 2018, 12:43:56 PM »

I cant think of anything exchange side which would cause that.   Faulty line cards can cause strange problems that can look REIN like, but on 21CN BTw MSANs these are usually spotted easier than older line cards and even vdsl line cards due to the amount of lines they control. 

The lower SNRM could/will in part be responsible for an increase in errors,  but by the same token I'm surprised that FEC isn't making much difference and at least reducing some of the errors.   I'm talking totally off the top of my head but that suggests its not noise from RFI/EMI bursts as we usually see but ingress from another source.  With the missing tones I'm beginning to wonder about a possible oxidised joint somewhere, but I'm not seeing any typical signs of a HR fault either from your graphs.   ???   

Is the line clear if you do a Quiet Line Test?   


b*cat is far better at electronics than me, so passing over to him his thoughts on whether he thinks an oxidised joint could possibly cause these types of symptoms despite it not being anything we've seen presented before.   Otherwise I'm scratching my head.
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kitz

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Re: ADSL2 line problems
« Reply #32 on: June 21, 2018, 12:55:06 PM »

Quote
Is the line clear if you do a Quiet Line Test?

Just another suggestion to see if you can pick up any symptoms of a High Open.   Temporarily set DSLstats to record every 5 seconds.
Ring the landline from another phone, let it ring for a couple of rings (sufficient for DSLstats to have made a recording), then pick up the receiver to open the line for a sufficient length of time for DSLstats to have made another recording.
All the while carefully watching the Upstream SNRm graph for signs of any dips or spikes. 
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g3uiss

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Re: ADSL2 line problems
« Reply #33 on: June 21, 2018, 01:27:03 PM »

Just another suggestion to see if you can pick up any symptoms of a High Open.   Temporarily set DSLstats to record every 5 seconds.
Ring the landline from another phone, let it ring for a couple of rings (sufficient for DSLstats to have made a recording), then pick up the receiver to open the line for a sufficient length of time for DSLstats to have made another recording.
All the while carefully watching the Upstream SNRm graph for signs of any dips or spikes.

Line is clear, but I recently had a line card changed which is when it all started. I will try the phone test you suggest later.
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g3uiss

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Re: ADSL2 line problems
« Reply #34 on: June 21, 2018, 01:51:05 PM »

A bit more history might be useful.

Line fault on previously excellent line Feb-April this year. Eventually cleared but, for first time Interleave needed DS to keep it stable

2 weeks ago sudden slow speeds SNR put up to 12 by DLM.

Isp identified line card problem. This replaced.

Profile set at SNR 6 US/DS no interleave.

DLM action every night increasing SNR and Interleave, eventually speed poor and below MGALS

Various interventions by ISP. Yesterday they put SNR back to 6 US/DS no interleave. This morning DLM raised SNR again to 9

The ES rate appears to be below the "Red: from my understanding as I assume its 2880 like VDSL.

I have resisted a visit because personal circumstances don't give a clear AM or PM slot (I think @kitz) know about this

Iv'e just uploaded stats agian

Tony .....at wits end :(
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g3uiss

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Re: ADSL2 line problems
« Reply #35 on: June 21, 2018, 03:19:19 PM »

Just another suggestion to see if you can pick up any symptoms of a High Open.   Temporarily set DSLstats to record every 5 seconds.
Ring the landline from another phone, let it ring for a couple of rings (sufficient for DSLstats to have made a recording), then pick up the receiver to open the line for a sufficient length of time for DSLstats to have made another recording.
All the while carefully watching the Upstream SNRm graph for signs of any dips or spikes.

Nothing perhaps a very slight US blip of less than .1db only could see it if I made the page a very short time period.
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kitz

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Re: ADSL2 line problems
« Reply #36 on: June 21, 2018, 07:41:05 PM »

Quote
Nothing perhaps a very slight US blip of less than .1db only could see it if I made the page a very short time period.

Very tiny blip and negligible. I'd be concerned if it took a downwards dip, but it looks fine.

Quote
Isp identified line card problem. This replaced.

Do you know for certain if the line card was replaced?   Usually you get a small amount of downtime when they swap the line card out or at least a minute or two if they do a lift and shift.

Typical line card problems display symptoms that look quite like REIN.   From what I have seen so far your SNRM is fairly straight lined.

Quote
The ES rate appears to be below the "Red: from my understanding as I assume its 2880 like VDSL.

WBC MTBE actually more forgiving than NGA.     I don't understand either why DLM is penalising you as you are below the latest figures that I have unless something has changed again. WBC MBTE for standard was decreased from 300 to 250 in 2014.

Looks like DLM has increased target SNRM but removed Interleaving.

Code: [Select]
Previous 1 day time = 24 hours 0 sec
FEC: 0 0
CRC: 45 1
ES: 697 1
SES: 31 0
UAS: 415 384
LOS: 3 0
LOF: 26 0
LOM: 0 0

Oh - you do have quite a few Loss of Framing which are classed as line failures.
It may be worthwhile keeping an eye on that figure,  I'm a wee bit more concerned over the LOFs than your Err/Sec count.  The combo of SES & LOF can indicate longer duration of noise bursts.  FEC doesn't always work well for longer duration noise bursts.   Beginning to wonder if DLM is detecting & acting on that rather than the Err/Sec count.



Quote
I have resisted a visit because personal circumstances don't give a clear AM or PM slot (I think @kitz) know about this
.....at wits end

I fully appreciate why it is difficult :(    Wish I could help more but I'm running out of ideas based on your stats.   :(



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kitz

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Re: ADSL2 line problems
« Reply #37 on: June 21, 2018, 07:55:28 PM »

Hmmmmm  just been reviewing your posts and noticed this

Quote
Only started after phone problems with water in the DP

Water ingress!!!!


See  Locating water ingress in telephone cables using frequency domain reflectometry 

Quote
When water enters a cable it lowers the magnitude and angle of the characteristic line impedance, causing reflections at the points where the water starts and ends. The dry and wet characteristic impedances of a 300-meter section of telephone line were experimentally measured and the reflection coefficient was estimated to have a phase angle of 20deg. Measurements of a properly terminated telephone line with 300 meters of the line immersed in water showed a first reflection with a phase angle of 162deg (180deg-18deg). A second reflection, from the end of the wet section, was measured with a phase angle of 25deg. These reflection angles differ from the 0deg or 180deg typical of bridge taps, open circuits or short circuits and this allows a technician to specifically identify water ingress

Is this why we are seeing those more or less evenly spaced 0 tones in hlog.      hlog usually identifies bridge taps by identifying the point of reflection. 

I'm out of my depth here as it would require proper tools to diagnose.    Any thoughts from b*cat, ejs or Blacksheep please. 
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ejs

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Re: ADSL2 line problems
« Reply #38 on: June 21, 2018, 08:43:24 PM »

I guess that those zero bit loaded tones with corresponding gaps in the HLog are "blackout" tones with no signal, to allow noise monitoring. I think some of those tones show small dips on the QLN, suggesting there's less crosstalk on those tones perhaps because other lines also aren't using those tones. I think those gaps will be unrelated to whatever the problem is.
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burakkucat

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Re: ADSL2 line problems
« Reply #39 on: June 21, 2018, 08:58:52 PM »

b*cat is far better at electronics than me, so passing over to him his thoughts on whether he thinks an oxidised joint could possibly cause these types of symptoms despite it not being anything we've seen presented before.

 :hmm:  Hmm . . . The symptoms are not characteristic of a joint developing HR or semi-conductive tendencies.
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g3uiss

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Re: ADSL2 line problems
« Reply #40 on: June 21, 2018, 09:22:16 PM »



Oh - you do have quite a few Loss of Framing which are classed as line failures,  but afaik these aren't counted as full retrains as far as MBTR is concerned. 
It may be worthwhile keeping an eye on that figure,  I'm a wee bit more concerned over the LOFs than your Err/Sec count.  The combo of SES & LOF can indicate longer duration of noise bursts.  FEC doesn't always work well for longer duration noise bursts.   Beginning to wonder if DLM is detecting & acting on that rather than the Err/Sec count.



That's interesting, I was beginning to think the DLM is acting on something else. I will see what the DLM does tomorrow, I'm pressing for a visit week tomorrow, when I can make either slot. I just hope I can get a good engineer. The water in the DP is also interesting. The line was stable for many years until that problem, then it was never as good. As for the line card, I only have the ISP's word that the fault was cleared.

Thanks all for input, very grateful. Will post news tomorrow  :)
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konrado5

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Re: ADSL2 line problems
« Reply #41 on: June 21, 2018, 09:38:25 PM »

Quote from: kitz
Oh - you do have quite a few Loss of Framing which are classed as line failures
Every retrain caused by interferences = 1 LOS and 9 LOF.
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g3uiss

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Re: ADSL2 line problems
« Reply #42 on: June 21, 2018, 10:17:47 PM »

Are these not related to all the resyncs caused by the ISP testing the line ?
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burakkucat

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Re: ADSL2 line problems
« Reply #43 on: June 21, 2018, 10:33:29 PM »

Water ingress!!!!

See  Locating water ingress in telephone cables using frequency domain reflectometry 

Is this why we are seeing those more or less evenly spaced 0 tones in hlog.      hlog usually identifies bridge taps by identifying the point of reflection. 

I'm out of my depth here as it would require proper tools to diagnose.    Any thoughts from b*cat, ejs or Blacksheep please.

I am aware that a "wet cable" can be seen by TDR but have never had any experience of such a situation. I have always assumed that it is water inside the outer sheath, water penetration as a result of protective sheath damage, that gives rise to the effect. Unfortunately payment is required to download a copy of the PDF file.

Only started after phone problems with water in the DP

What we currently do not know is whether the DP is aerial or underground. With an aerial DP, I would be very surprised for any significant quantity of water to accumulate . . . even more so for such water to fortuitously submerge the end of a cable sheath, thus setting up a "wet cable". However if it is an underground DP, whose closure was defective at some time in the past, then there is a distinct possibility of significant water ingress.

I wonder if Black Sheep has had any experience of such a fault or knows of an occurrence?
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konrado5

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Re: ADSL2 line problems
« Reply #44 on: June 21, 2018, 10:47:02 PM »

Is this why we are seeing those more or less evenly spaced 0 tones in hlog.      hlog usually identifies bridge taps by identifying the point of reflection.
I'm almost sure that these 0-bit tones are disabled tones. On QLN there isn't any significant noise. Moreover, there is no signal. If signal is very weak hlog looks jagged. For example, I've had jagged Hlog graph when I've had very low power output in HAM band mask.
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