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Author Topic: Continuing lesser line #3 problems - noise - Request for read of stats  (Read 8314 times)

Weaver

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I’m still having problems with line #3 after the engineer’s visit this week, but lesser ones. Big noise spikes mean that connections are being broken and sync rates need to be reduced to allow for this.

I have captured an SNRM-vs-time graph - see https://ibb.co/zPkZ4vZ.

But in addition, the upstream of line 3 continues to be a big problem, with more than 9dB [!] of noise variation through the day, in the same pattern that is now becoming familiar: flat noise-vs-time graphs, with vertical cliffs between levels. The upstream high SNRM level over the last 24 hrs was 10.5dB and the low level was 1.6dB, with a target SNRM set at 6dB.

There is one difference from the earlier picture though: the appearance of spikes overlaid on the ‘plateaux’ graph.

On the SNRM-vs-time graph there are huge upward-going spikes - ie. noise disappearing for very short periods. These are the opposite of a problem of course. A new feature. Just an oddity. God only knows why such ultra-quiet brief moments are happening.

More importantly, there are also downward spikes in the upstream, ~2.5 dB high, and these are wrecking upstream reliability, since during part of the day the upstream SNRM is only 1.6dB, for many hours, until the noise level drops and the graph goes up to the next plateau. The modem chooses to hang on in there and does not drop the link, despite the downward-going spikes bring high enough to make the upstream SNRM go negative for a very short period.

Regarding the graph, unfortunately the y-axis scale is very unhelpful, as the y-axis max is far too high making it difficult to read y-values off accurately. The big upward-going spikes are creating crazy all-time high values and so stretching the y-axis range.

My main requests though:

I got the following stats from the modem and I would be very grateful if (i) someone would read them for me and comment. I would like to know what you think in general and (ii) specifically just how bad you think the error counts are. Also, I’m ashamed to say that, due to the once more increased pain drugs, I have forgotten the meaning of some of the fields in these reports, and (iii) I would be very grateful if some kind folks would go through the exact definitions of the various fields relating to errors. (I can look up the framing-related variables in G.992.3.) Here’s line #3:

Code: [Select]
VMG1312-B10A
Login: admin
Password:
 > xdslctl info --show
xdslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    8000
Last initialization procedure status:   0
Max:    Upstream rate = 280 Kbps, Downstream rate = 2940 Kbps
Bearer: 0, Upstream rate = 344 Kbps, Downstream rate = 2606 Kbps

Link Power State:       L0
Mode:                   ADSL2 Annex A
TPS-TC:                 ATM Mode(0x0)
Trellis:                U:ON /D:ON
Line Status:            No Defect
Training Status:        Showtime
                Down            Up
SNR (dB):        6.0             6.1
Attn(dB):        64.5            40.7
Pwr(dBm):        17.8            12.4

                        ADSL2 framing
                        Bearer 0
MSGc:           63              12
B:              76              4
M:              2               16
T:              1               8
R:              16              16
S:              1.8554          7.2453
L:              733             106
D:              1               4

                        Counters
                        Bearer 0
SF:             36390           35897
SFErr:          0               0
RS:             1255461         323009
RSCorr:         2               0
RSUnCorr:       0               0

ReXmt:          0               0
ReXmtCorr:      0               0
ReXmtUnCorr:    0               0

                        Bearer 0
HEC:            0               0
OCD:            0               0
LCD:            0               0
Total Cells:    3600553         473763
Data Cells:     18185           5381
Drop Cells:     0
Bit Errors:     0               0

ES:             4181            5031
SES:            2543            709
UAS:            24374           22609
AS:             587

                        Bearer 0
INP:            29.00           2.00
INPRein:        0.00            0.00
delay:          8               7
PER:            16.00           16.30
OR:             34.49           8.83
AgR:            2628.53 351.95

Bitswap:        99/106          12/12
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johnson

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #1 on: January 20, 2019, 08:13:12 AM »

Clearly some erroneous values on those graphs, could you post the output of the log file from routerip:8000/data/logfile?
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johnson

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #2 on: January 20, 2019, 08:43:52 AM »

The spikes up to ~100db SNRM are some kind of artifact that should not be present in the graphs, a copy of the logfile would help with figuring out why. If no obvious way of ignoring them becomes apparent I can add clipping to the graph.

The negative downstream in red values are indicative of noise bursts that sometimes the modem copes with, others causing a resync.

Its hard to read much from the current stats without knowing the uptime. For instance the 24374 UAS mean nearly 7 hours with no connectivity, either unplugged from the line or with the modem unable to gain sync.

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jelv

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #3 on: January 20, 2019, 09:45:16 AM »

It seems OpenReach are incapable of keeping your four lines working properly for any significant period so I wonder if AAISP could arrange for you to have booked weekly engineer visits? This would be without you having to raise a new fault each time - engineer just turns up and asks what needs looking at this week.  :P
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j0hn

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #4 on: January 20, 2019, 11:28:30 AM »

lol....
as Johnson says there's no way you could possibly have 100dB SNRM on the upstream (or downstream), if only.

The downstream looks shaky though, but I'd send the log to Johnson to have a look over before doing anything else.
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Weaver

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #5 on: January 20, 2019, 04:12:16 PM »

There is a real problem though, it’s not just the graphs. Downstream sync rate is now down to 265k from 3055k [!] with huge packet loss and frequent disconnects. Will swap modem out as a rule-out. AA notified.
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johnson

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #6 on: January 20, 2019, 04:35:13 PM »

I do not doubt there is problem with the line.

I just want to find a way of fixing the graphs so they are more readable and can maybe give you a better view of whats going on.

Also, as I mentioned previously, uptime is needed when posting ES, SES UAS etc. Its hard to make sense of them without it.

Edit:clarity
« Last Edit: January 20, 2019, 04:42:29 PM by johnson »
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Weaver

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #7 on: January 21, 2019, 07:00:00 AM »

I thought one of the stats’ reports does give time intervals - is that correct? Apologies for posting the wrong report then, as indeed it’s useless without durations.

The uptime was 1d 16h 28m. Luckily I recorded that figure separately.
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aesmith

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #8 on: January 21, 2019, 09:31:56 AM »

Could the 100dB spikes be mis-reporting of negative values?  I had that once when collecting via SNMP from (I think) Linksys, presumably some signed/unsigned mismatch in the MIB.
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Weaver

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #9 on: January 21, 2019, 01:56:08 PM »

I was just thinking the same thing. The Netgear DG834v1 used to display garbage when SNRM values went below zero, a sign bit problem. Was fixed later on.

However I think there are visible downward-going spikes which do reach negative values, so if the basic idea is correct, then the sign bit problem would have to be elsewhere in the arithmetic, somewhere earlier. That’s the only thing that I can think of to save the idea.
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Chrysalis

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #10 on: January 21, 2019, 02:55:01 PM »

yeah it either means negative value or loss of sync with those crazy readings.
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Weaver

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #11 on: January 21, 2019, 02:59:35 PM »

And nightmare: line 2 has also gone bad again, so it appears, although I ought to reserve judgment until it has been retested at 6dB target SNRM downstream instead of the current 3dB, which is potentially asking a lot (although 3dB is normally fine in these lines with no problems over many many months).

Line 2 now losing sync, huge packet loss etc.

And this weird message

BT Test xDSL Copper Test:Pass Standalone sub test passed successfully.Pass Max product, DCN, in synch, tests OK DS06:The system cannot carry out the test because it appears that a call is in progress on the line.Please ensure that there are no calls on the line and retry the test.Otherwise raise a fault report
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Weaver

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #12 on: January 21, 2019, 03:17:01 PM »

Ah, now something sensible

BT Test xDSL Copper Test:Fail Line test failed report fault to OR, appointment advised.Fail Line test failed report fault to OR, appointment advised. T024:FAULT - Loop (Rectified)
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burakkucat

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #13 on: January 21, 2019, 05:16:42 PM »

BT Test xDSL Copper Test:Pass Standalone sub test passed successfully.Pass Max product, DCN, in synch, tests OK DS06:The system cannot carry out the test because it appears that a call is in progress on the line.Please ensure that there are no calls on the line and retry the test.Otherwise raise a fault report

Low insulation, A- to B-wire, will appear to the automated test-head as a telephony call in progress. I.e. the circuit appears to be looped.

BT Test xDSL Copper Test:Fail Line test failed report fault to OR, appointment advised.Fail Line test failed report fault to OR, appointment advised. T024:FAULT - Loop (Rectified)

The observed rectified loop confirms my earlier, above, suspicion.
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Weaver

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Re: Continuing lesser line #3 problems - noise - Request for read of stats
« Reply #14 on: January 21, 2019, 05:55:24 PM »

Ah, makes sense. Low insulation, could be abrasion? Something running over the cable lying on the ground at the side of the road maybe? Or huge hairy cows stamping on it? (There are actually a lot of highland - hairy orange - cows on the lower part of the northern slopes of the road, by the Harrapul fank, where repairs were carried out a couple of years ago.)
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