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[Weaver]

Oh no, HCD 5 dB deep in line 2 again. It set in yesterday (Tue, 13 th) lunchtime:

Hollow-curve disease in mid-stage; SNRM vs tones, modem 2:

   



History; SNRM down and upstream vs time, modem 2:


   

[Weaver]

And guess what, very, very early this morning, line 4 also suddenly started showing the early signs of HCD. Funny shape, not seen before:
Line 4:



Here is the latest Summary / wellness and errors report for all lines:

 

Code: [Select]

       Summary of DSL links’ wellbeing and error counts
     ────────────────────────

* There are 4 modems in total. They are:  #1, #2, #3 and #4
* The active, contactable modems are:      #1, #2, #3 and #4
* The modems successfully queried are:    #1, #2, #3 and #4


       ───────────────────────
       ***                                                                           ***
       ***     There is some SERIOUS BADNESS !          ***
       ***                      All is not well !   😦                       ***
       ***                                                                           ***
       ───────────────────────


* Sync rate: The following links have a really low downstream sync rate, below min:
   Link #1 downstream: the current sync rate 2442 kbps is below the minimum expected downstream rate (2600 kbps)
   Link #2 downstream: the current sync rate 1731 kbps is below the minimum expected downstream rate (2590 kbps)

--
* SNRM: The SNRM of the following link is out of range:
   Link #2 downstream: current SNRM: 4.8 dB is too high;  above the expected maximum SNRM ( 3.5 dB )


--
* HCD:❗So-called ‘hollow curve disease’ (HCD) defect detected in the downstream SNR-vs-tones curve of link #2. Serious fault. 🔺
   Link #2: Summary: curve midpoint test tone 59 is 5.65556 dB below chord 1: (tones 40-85); ❗
   Link #2: Details: chord 1: [ tone 40: 29.5625 dB; chord midpoint test tone 59: 28.71806 dB; tone 85: 27.5625 dB ]; curve midpoint test tone 59: 23.0625 dB

--
* ES (not so serious): The following link has a few CRC errors, at a lower error rate, where the ES rate < 60 ES / hr (†):
   Link #2: downstream:  penultimate period: ES per hr: 4.00, mean time between errors: 900 s, collection duration: 900 s, SNRM: 4.799 dB

────────────────────────────────────
(†) The duration of a ‘most recent’ errored seconds (ES) collection bucket is
variable, with a _maximum_ of 15 mins. The ‘most recent’ buckets’ start times
are always 15 mins apart, and the end time is now. A ‘penultimate’ bucket is a
fixed 15 mins long. An ES is a 1 s time period in which a DSL modem receives
corrupt data that can not be recovered by the two modems’ error correction
capabilities. (This is not to be confused with the whole-path, end-to-end packet
retransmission-based error correction used in ‘transport layer’ software such as
QUIC, TCP etc. Here we are only concerned with data corruption on a single,
direct, modem-to-modem DSL link, and its correction by modems.)
────────────────────────────────────

--
Time now: 2022-09-14T09:05:20 UTC.

                                     ◅ ◅ ◅◊▻ ▻ ▻

[Weaver]

The small HCD in line 4 has become undetectable, with any remaining trace of that rather odd shape now buried in the noise.
Line 2 is now really really bad downstream, because of the high SNRM.

Code: [Select]

       Summary of DSL links’ wellbeing and error counts
     ────────────────────────

* There are 4 modems in total. They are:  #1, #2, #3 and #4
* The active, contactable modems are:      #1, #2, #3 and #4
* The modems successfully queried are:    #1, #2, #3 and #4


       ───────────────────────
       ***                                                                           ***
       ***     There is some SERIOUS BADNESS !          ***
       ***                      All is not well !   😦                       ***
       ***                                                                           ***
       ───────────────────────


* Sync rate: The following links have a really low downstream sync rate, below min:
   Link #1 downstream: the current sync rate 2442 kbps is below the minimum expected downstream rate (2600 kbps)
   Link #2 downstream: the current sync rate 288 kbps is below the minimum expected downstream rate (2590 kbps)

--
* SNRM: The SNRM of the following link is out of range:
   Link #2 downstream: current SNRM: 10.4 dB is too high;  above the expected maximum SNRM ( 3.5 dB )

--
* HCD:❗So-called ‘hollow curve disease’ (HCD) defect detected in the downstream SNR-vs-tones curve of link #2. Serious fault. 🔺
   Link #2: Summary: curve midpoint test tone 59 is 6.91667 dB below chord 1: (tones 40-88); ❗
   Link #2: Details: chord 1: [ tone 40: 20.9375 dB; chord midpoint test tone 59: 21.72917 dB; tone 88: 22.9375 dB ]; curve midpoint test tone 59: 14.8125 dB


--
Time now: 2022-09-16T12:13:23 UTC.

                                     ◅ ◅ ◅◊▻ ▻ ▻


Overall stats for all modems:

Code: [Select]

                        Status of each link
                    ──────────

* There are 4 modems in total. They are:  #1, #2, #3 and #4
* The active, contactable modems are:      #1, #2, #3 and #4
* The modems successfully queried are:    #1, #2, #3 and #4


   Link #1: sync rate: downstream: 2.442 Mbps at SNRM 3.3 dB; upstream: 643 kbps at SNRM 6.3 dB
   Link #1: uptime: 4 days 11 hours 29 min 5 sec

--
   Link #2: sync rate: downstream: 288 kbps at SNRM 10.4 dB; upstream: 512 kbps at SNRM 6.4 dB
   Link #2: uptime: 6 hours 17 min 49 sec

--
   Link #3: sync rate: downstream: 2.968 Mbps at SNRM 3.2 dB; upstream: 627 kbps at SNRM 5.7 dB
   Link #3: uptime: 20 days 20 hours 38 min 49 sec

--
   Link #4: sync rate: downstream: 2.741 Mbps at SNRM 3.3 dB; upstream: 355 kbps at SNRM 6.2 dB
   Link #4: uptime: 12 days 12 hours 8 min 17 sec

--
Time now: 2022-09-16T12:15:42 UTC.

                                              ◅ ◅ ◅◊▻ ▻ ▻

Picture of the horror that is line 2:

[Weaver]

I was misled into optimism. The line 2 was very sickly yesterday, out of respect. Modem was cycling through the training steps trying to get to showtime for a good part of the time. As of 12:36 UTC today approx it has now recovered and is perfect again. So we have an intermittent severe fault. On Friday afternoon, AA saw a report of an "exchange fault" and "refer to BTW" that you saw on Friday. I have asked AA if they have an idea what that was all about; too soon to expect a reply, and they will probably be swamped with serious problem questions after the long weekend with the bank holiday.

So all good for the moment. The stats are perfect. There’s no sign of any HCD even. At that point this morning it very suddenly jumped back to being perfect. As if there had been someone out there working on it, just not based here. Perhaps AA had booked something on Friday that took effect just then. All known pictures available. The logs show chaos yesterday and before.

[Weaver]

AA said they only know that little snippet of information from BTW: "Router and Cabling; Core Network and Serving Exchange;software problem rectified."

Does anyone know what that could mean? I mean: What kinds of things happen that fit that category?

Line 2 still perfect as are all other lines. Occasional tiny bits of downstream CRC errors on various lines, at 3dB downstream, but overall it’s as good as it gets.