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Dave9's avatar
Contributor III
5 years ago

What causes T3 timeouts?

After several service calls, I finally got all of the issues with my connection resolved. There were multiple issues including bad exterior cable and bad amplifier on the pole. Everything was great for about 10 days, then T3 timeouts started occurring.

I'm not asking for someone to give me a reply that says "We'd be happy to take a look at your account." The signals and error rates are great. Almost perfect I would say, which is why I'm baffled by the onset of multiple T3 timeouts starting a few days ago.

What causes T3 timeouts? What are some reasons that these would start occurring? Almost everything out to the pole has been replaced (modem, interior cable, most exterior cable, pole amplifier) so I have to wonder if it's a problem farther up the line or even at the CMTS itself. Is that possible?

06/01/2020 13:02 82000500 3 "Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=(redacted);CMTS-MAC=(redacted);CM-QOS=1.1;CM-VER=3.1;"
  • The problem with those power levels is like I was saying earlier, it's just a snapshot.  A competent Cox tech can monitor in real time what your power levels are and see if there is fluctuation.  Your issue looks pretty similar to what I was dealing with (good TX-RX power, SNR, etc) and my problem started right after Cox split one of their nodes (Vegas) to ease congestion.  That's when I removed my only spiltter (was trying to keep RX levels closer to 0) and pulled a new cable to the curb from DMARC (3rd time).  Since then, I've been rock solid.

    I will say dealing with cox help over the phone or txt is a waste of time.  You need a good tech you can talk to face to face, because it seems you have the vocabulary to troubleshoot this, you just need a tech with more/better tools.

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    • Dave9's avatar
      Contributor III

      That matches up with the answer I found in my own research. Is there anything I can do to determine if the ingress is coming from wiring or equipment on my premises or farther up the line? It would have to be low frequency ingress since error rates on the downstream (high frequency) channels are great. No uncorrectables, and 0 to 3 correctables per day depending on channel.

      • Zurq's avatar
        Contributor II

        change splitters and coax. if you have tv service one downstream channel is used for tv, and you wills see uncorrectables on it.

  • Dave9's avatar
    Contributor III

    Update: I changed the interior coax one more time just to be safe. Still seeing T3 timeouts. Interestingly it looks like the modem has been configured to only show the most recent T3 in the logs so it looks like only 1 has ever happened, but the timestamp on that entry keeps changing to reflect the last time the error occurred. Also I'm seeing packet loss on pings which I never saw before the T3s started.

    The only variables left in the picture are the coax between the demarc and the wall jack, and something upstream from the pole amplifier. What's the best way to determine the cause? I know calling support will be frustrating because the signals look great and it's hard for them to see past the signals and understand intermittent issues.

    • FatDaddyWampus's avatar

      You'll need to get a tech out that can monitor the power levels in real time.  Your modem will only give you a snapshot.  In the meantime, If possible, I'd simplify the whole path.  For example, I have one piece of direct burial RG6 from the street (via conduit) to my dmarc where it hits a bonded bullet, then from there it's a solid piece of coax all the way to the modem.  I removed all wall jacks and used low voltage cable feedthroughs at the wall gangboxes.  No splitters/taps/wall plates anywhere in the path to my modem (but all I have is internet)

      I'm surprised you're not getting any Dynamic Range Window errors along with your T3's though.  Here's my power level snapshot (modem log is clear):  

      • Dave9's avatar
        Contributor III

        I had been getting a ton of DRW violations before they changed the amplifier, and maybe I still am. The log has changed in a very strange way where only the most recent event seems to show up at the top, and everything else below it is old (2-3 weeks old). It's like it saved a lot of log entries from the first time I powered it on and doesn't ever write over those. Makes it hard to troubleshoot. Any tips for what I can say to support to make them understand the issue and get the right tech out? Like I said, my signals are amazingly good and I don't think many of them understand there can be a problem even with good signals.

        It's strange because it all worked perfectly for about 10 days before the T3s started up. Seems to be at least 2 per hour but it's hard to say since I only get the most recent one in the log. I'm going to try doing a modem refresh even though I'm not sure if that really does anything beyond just a reboot.

        Downstream Bonded Channels
        Channel ID Lock Status Modulation Frequency Power SNR/MER Corrected Uncorrectables
        5 Locked QAM256 807000000 Hz 9.6 dBmV 43.6 dB 0 0
        1 Locked QAM256 783000000 Hz 10.1 dBmV 44.0 dB 0 0
        2 Locked QAM256 789000000 Hz 10.2 dBmV 44.0 dB 0 0
        3 Locked QAM256 795000000 Hz 9.7 dBmV 43.7 dB 0 0
        4 Locked QAM256 801000000 Hz 9.9 dBmV 43.6 dB 0 0
        6 Locked QAM256 813000000 Hz 9.4 dBmV 43.5 dB 0 0
        7 Locked QAM256 819000000 Hz 9.5 dBmV 43.5 dB 0 0
        8 Locked QAM256 825000000 Hz 9.0 dBmV 43.3 dB 0 0
        9 Locked QAM256 831000000 Hz 9.2 dBmV 43.4 dB 0 0
        10 Locked QAM256 837000000 Hz 9.0 dBmV 43.1 dB 0 0
        11 Locked QAM256 843000000 Hz 8.8 dBmV 43.2 dB 0 0
        12 Locked QAM256 849000000 Hz 8.9 dBmV 43.0 dB 0 0
        13 Locked QAM256 855000000 Hz 8.6 dBmV 42.9 dB 0 0
        14 Locked QAM256 861000000 Hz 8.6 dBmV 43.0 dB 0 0
        15 Locked QAM256 867000000 Hz 8.4 dBmV 42.9 dB 0 0
        16 Locked QAM256 873000000 Hz 8.2 dBmV 42.7 dB 0 0
        33 Locked QAM256 357000000 Hz 7.8 dBmV 44.5 dB 0 0
        34 Locked QAM256 363000000 Hz 7.8 dBmV 44.8 dB 0 0
        35 Locked QAM256 369000000 Hz 8.0 dBmV 44.9 dB 0 0
        36 Locked QAM256 375000000 Hz 8.0 dBmV 44.9 dB 0 0
        37 Locked QAM256 381000000 Hz 8.1 dBmV 44.8 dB 0 0
        38 Locked QAM256 387000000 Hz 8.2 dBmV 44.8 dB 0 0
        39 Locked QAM256 393000000 Hz 8.4 dBmV 44.9 dB 0 0
        40 Locked QAM256 399000000 Hz 8.4 dBmV 44.9 dB 0 0
        41 Locked QAM256 405000000 Hz 8.5 dBmV 44.8 dB 0 0
        42 Locked QAM256 411000000 Hz 8.7 dBmV 44.6 dB 0 0
        43 Locked QAM256 417000000 Hz 8.7 dBmV 44.8 dB 0 0
        44 Locked QAM256 423000000 Hz 8.9 dBmV 45.0 dB 0 0
        45 Locked QAM256 429000000 Hz 8.9 dBmV 44.9 dB 0 0
        46 Locked QAM256 435000000 Hz 8.9 dBmV 44.9 dB 0 0
        47 Locked QAM256 441000000 Hz 8.9 dBmV 44.9 dB 0 0
        48 Locked QAM256 447000000 Hz 8.8 dBmV 44.7 dB 0 0
        159 Locked Other 300000000 Hz 7.6 dBmV 43.0 dB 2131560290 0

        Upstream Bonded Channels
        Channel Channel ID Lock Status US Channel Type Frequency Width Power
        1 2 Locked SC-QAM Upstream 23500000 Hz 6400000 Hz 38.0 dBmV
        2 1 Locked SC-QAM Upstream 16900000 Hz 6400000 Hz 38.0 dBmV
        3 3 Locked SC-QAM Upstream 29900000 Hz 6400000 Hz 39.0 dBmV
        4 4 Locked SC-QAM Upstream 36300000 Hz 6400000 Hz 39.0 dBmV