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[vic0239]

I’ve noticed that my VMG8924 is reporting a huge jump in B0 FEC errors. These appear to have gone from very few to a constant ~120,000. I remember reading about a similar experience with this device elsewhere on the forum, but can’t recall if there was any resolution. I’m hoping that this is a bug in the firmware and not an issue with my line. I’m running VMG8924-B10A_1.00(AAKL.13)C0. As this is the second occurrence in four days, I’ve only been using the VMG8924 for about a week, I’m wondering if I should ditch the VMG8924 as modem or should I be worrying about my line?

[William Grimsley]

Hi vic0239,

Has DLM made changes to your line by any chance? DLM may have resynced your line to increase interleaving.

[vic0239]

No, no resyncs. Here are the vdsl stats from the router:

============================================================================
    VDSL Training Status:   Showtime
                    Mode:   VDSL2 Annex B
            VDSL Profile:   Profile 17a
                G.Vector:   Disable
            Traffic Type:   PTM Mode
             Link Uptime:   3 days: 7 hours: 56 minutes
============================================================================
       VDSL Port Details       Upstream         Downstream
               Line Rate:     12.077 Mbps       56.658 Mbps
    Actual Net Data Rate:     12.044 Mbps       56.659 Mbps
          Trellis Coding:         ON                ON
              SNR Margin:        5.8 dB            6.1 dB
            Actual Delay:          0 ms              0 ms
          Transmit Power:        7.5 dBm          14.2 dBm
           Receive Power:       -5.9 dBm          -4.3 dBm
              Actual INP:        0.0 symbols      48.0 symbols
       Total Attenuation:       13.5 dB           18.6 dB
Attainable Net Data Rate:     11.951 Mbps       56.711 Mbps
============================================================================
      VDSL Band Status    U0      U1      U2      U3      D1      D2      D3
  Line Attenuation(dB):  6.1    31.3    46.5     N/A    16.0    39.5    60.7   
Signal Attenuation(dB):  6.1    30.8    45.9     N/A    16.6    39.2    60.8   
        SNR Margin(dB):  5.9     5.9     5.8     N/A     6.1     6.1     6.1   
   Transmit Power(dBm):  0.1   -11.9     6.6     N/A    12.2     8.0     5.6   
============================================================================

            VDSL Counters

           Downstream        Upstream
Since Link time = 56 min 39 sec
FEC:      22826904      2717
CRC:      1      659
ES:      1      520
SES:      0      0
UAS:      0      0
LOS:      0      0
LOF:      0      0
LOM:      0      0
Latest 15 minutes time = 12 min 16 sec
FEC:      1467528      1
CRC:      0      0
ES:      0      0
SES:      0      0
UAS:      0      0
LOS:      0      0
LOF:      0      0
LOM:      0      0
Previous 15 minutes time = 15 min 0 sec
FEC:      1793216      27
CRC:      0      2
ES:      0      1
SES:      0      0
UAS:      0      0
LOS:      0      0
LOF:      0      0
LOM:      0      0
Latest 1 day time = 7 hours 57 min 16 sec
FEC:      22507287      382
CRC:      0      92
ES:      0      60
SES:      0      0
UAS:      0      0
LOS:      0      0
LOF:      0      0
LOM:      0      0
Previous 1 day time = 24 hours 0 sec
FEC:      290629      780
CRC:      0      214
ES:      0      176
SES:      0      0
UAS:      0      0
LOS:      0      0
LOF:      0      0
LOM:      0      0
Total time = 1 days 7 hours 57 min 16 sec
FEC:      22826904      2717
CRC:      1      659
ES:      1      520
SES:      0      0
UAS:      36      36
LOS:      0      0
LOF:      0      0
LOM:      0      0

[vic0239]

FECs have dropped to normal levels again. I never witnessed this with the Billion 8800NL. 

Latest 15 minutes time = 2 min 13 sec
FEC:      0      4
CRC:      0      0
ES:      0      0
SES:      0      0
UAS:      0      0
LOS:      0      0
LOF:      0      0
LOM:      0      0

[kitz]

Have you recently had an odd resync?    About a week ago at around midnight I notice that I had lost connection.   I was only down for about 5 mins or so, yet after I came back up my line was behaving a bit erratically.  ie the SNRm was going a bit skewy.      Ive noticed a few couple of people say similar over the past few months.     Despite checking I couldnt find any reason for the resync.    Chrys also had something similar but he had some sort of f/w upgrade to his line card. 

[vic0239]

@kitz, thanks for responding.

No I haven’t had any unscheduled resyncs, just two self-induced ones when I first connected up the ZyXEL to my line (08 Mar 15:22) and again when I restarted the router during the first episode of high FECs (12 Mar 07:28). The first occurrence lasted right through the night until I restarted in the morning, but yesterday’s stopped after a couple of hours. Strange one.

[vic0239]

Just had another few hours of high FEC count,  this time in excess of 200,000 sustained across the period. Assuming these are genuine, will having such a large number of FECs have a detrimental impact on how DLM views the state of my line? Will they be recorded at both ends? I certainly don't experience any drop off in performance during these episodes. Thanks.

[Starman]

As far as we're aware DLM doesn't take any notice of FEC errors - only Error Seconds, Re-syncs and your Signal to Noise Margin.

[broadstairs]

Is this a sudden burst for say one minute of FECs or does this high number persist for a long time? I do see sudden bursts of high FECs on my 8924 but the count is only high for one minute.

Stuart

[vic0239]

As far as we're aware DLM doesn't take any notice of FEC errors - only Error Seconds, Re-syncs and your Signal to Notice Margin.

Thanks, that's a comfort at least.

Is this a sudden burst for say one minute of FECs or does this high number persist for a long time? I do see sudden bursts of high FECs on my 8924 but the count is only high for one minute.

Stuart

No it lasts for a few hours then just stops (see today's graph). The fact that it eventually stops makes me doubt it is the router unless some weird logic is at play there. If it continues on a daily basis I will probably dig out my HG612 and front the ZyXEL with that and see if the issue goes away. I like the performance and features of the 8924, so don't want to abandon it completely.

[Ronski]

It's absolutely nothing to worry about, we used to clock up millions at work, they would suddenly come and go, and then seemed to almost disappear, here's our last years graph. This is on an HG612.

[vic0239]

Ok, thanks. I'll let it be for now and just keep a watchful eye on it.