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Forum Discussion
cm600 xfinity T3 error then bufferbloat
Hi,
i have blast pro (250down/10up) with xfinity in 94550. the cm600, firmware version shows V1.01.18, is connected to a ubiquiti edgerouter-x running latest 1.10.9 firmware. i use the smart queue to control bufferbloat very effectively and this setup has worked well until last november (2018). since that time, i get fairly regular T3 errors in the log, every couple of days. e.g. Started Unicast Maintenance Ranging - No Response received - T3 time-out;
the modem auto connects and we have internet. HOWEVER, bufferbloat is out of control UNLESS I reboot the modem. it can be a hard or soft reboot, but that fixes.
is this a known problem with the cm600's? prior to november last year, i never had to reboot. since november this has been ongoing. fortunately reboot fixes it. any ideas on what it could be? we know how helpful xfinity is.
thanks,
jeff
12 Replies
Noise in the line can cause t3 errors.
I would go through and check your connections and your cables first. A bad/cheap connection, splitter, cable will degrade signal.It can be an intermittent failure or a failure that only happens when the signal is boarderline. Start with the easy stuff you control and can adjust.
Do you have a screenshot/snip of your connections page (download and upload)?
i've had 2 service call checking connector from the street to the house. signal levels are nominal.
we've done the basic trouble shooting. the timeouts are intermittent as i said.
not the errors. this is since a reboot 3 days ago, the last t3 error.
here's the down/up:
Frequency start Value This field below allows you to modify the frequency the cable modem start with its scan during initialization and registration. Enter the new start frequency and restart the cable modem for it to take effect. Starting Frequency Startup Procedure Procedure Status Comment Acquire Downstream Channel 597000000 Hz Locked Connectivity State OK Operational Boot State OK Operational Security Enable BPI+ IP Provisioning Mode Honor MDD IPv6 only <tabindex=-1>Downstream Bonded Channels</tabindex=-1> Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables 1 Locked QAM256 22 597000000 Hz -8.6 dBmV 37.3 dB 44 0 2 Locked QAM256 1 465000000 Hz -6.2 dBmV 39.2 dB 1577 3345 3 Locked QAM256 2 471000000 Hz -6.4 dBmV 39.2 dB 4 0 4 Locked QAM256 3 477000000 Hz -6.4 dBmV 39.2 dB 7 0 5 Locked QAM256 4 483000000 Hz -6.3 dBmV 39.2 dB 5 0 6 Locked QAM256 5 489000000 Hz -6.4 dBmV 39.2 dB 1 0 7 Locked QAM256 6 495000000 Hz -6.5 dBmV 39.2 dB 2 0 8 Locked QAM256 7 507000000 Hz -6.7 dBmV 34.8 dB 13 0 9 Locked QAM256 9 519000000 Hz -6.9 dBmV 38.9 dB 3 0 10 Locked QAM256 13 543000000 Hz -8.0 dBmV 38.0 dB 24 0 11 Locked QAM256 14 549000000 Hz -8.0 dBmV 38.0 dB 20 0 12 Locked QAM256 15 555000000 Hz -8.0 dBmV 38.0 dB 19 0 13 Locked QAM256 16 561000000 Hz -8.2 dBmV 37.7 dB 19 0 14 Locked QAM256 17 567000000 Hz -8.3 dBmV 37.6 dB 20 0 15 Locked QAM256 18 573000000 Hz -8.4 dBmV 37.6 dB 16 0 16 Locked QAM256 19 579000000 Hz -8.5 dBmV 37.5 dB 37 0 17 Locked QAM256 20 585000000 Hz -8.4 dBmV 37.5 dB 0 0 18 Locked QAM256 21 591000000 Hz -8.5 dBmV 37.5 dB 0 0 19 Locked QAM256 23 603000000 Hz -8.6 dBmV 37.1 dB 0 0 20 Locked QAM256 24 609000000 Hz -8.5 dBmV 37.2 dB 0 0 21 Locked QAM256 26 621000000 Hz -8.7 dBmV 36.9 dB 0 0 22 Locked QAM256 27 627000000 Hz -9.0 dBmV 36.5 dB 0 0 23 Locked QAM256 28 633000000 Hz -9.0 dBmV 36.5 dB 0 0 24 Locked QAM256 32 657000000 Hz -9.2 dBmV 36.2 dB 0 0 <tabindex=-1>Upstream Bonded Channels</tabindex=-1> Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power 1 Locked ATDMA 3 5120 Ksym/sec 30300000 Hz 51.3 dBmV 2 Locked ATDMA 1 5120 Ksym/sec 17300000 Hz 49.8 dBmV 3 Locked ATDMA 2 5120 Ksym/sec 23700000 Hz 50.5 dBmV 4 Locked ATDMA 4 5120 Ksym/sec 36700000 Hz 52.3 dBmV 5 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 6 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 7 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV 8 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV persaonally i feel that it is plant noise. we had that years ago and was why i left comcast. but we came back because att was too slow. it's been good for nearly 2 years... not intermittently bad. but at least i can fix it.
i was hoping it might be a modem issue that could be fixed by firmware... i guess not?
Your power levels are out of sync. Your upstream levels are a bit to high and your downstream is a bit to low. Your best download is just within spec and your worse is out of spec. Its imbalanced and out of spec. Here's a website with some basic specs that are easy to interpret.
https://pickmymodem.com/signal-levels-docsis-3-03-1-cable-modem/
Did you go through and check connectors, cables, splitters? I had a cable with water in it once that caused an imbalance. I would more your router to right where it comes into your house and connect there to see what your connections are. this reduces the chances of bad connections/wires/splitters causing the issue. If you move the modem, post back here what the signals change to.
