I've been having this issue for almost two months at this point: modem signal levels and power output look acceptable as well as all DOCSIS 3.0 channels seem to be healthy. However, the OFDM channel on 159 is having a lot of correctable errors and the modem fluctuates between a state multiple times a day where I get my full 1GBits to a very slow 32Mbits when the issues on the OFDM channel are observed. First off however, some data to show the status of the modem (Netgear CM2000):
Over time the signal levels are pretty steady too (I record them with a tool I wrote to visualize the levels in Grafana):
Upstream levels are steady too:
Correctable and uncorrectable errors over time (OFDM only):
Logs
Note how the issue usually starts with an Event Type code 3 on the OFDM channel, then followed by events 20 and 22 alternating.
Thu Jan 28 08:01:19 2021 (Notice (6)) CM-STATUS message sent. Event Type Code: 22; Chan ID: 159; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=08:36:00:00:00:00;CMTS-MAC=00:38:df:08:73:25;CM-QOS=1.1;CM-VER=3.1; Thu Jan 28 08:00:54 2021 (Notice (6)) CM-STATUS message sent. Event Type Code: 20; Chan ID: 159; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=08:36:00:00:00:00;CMTS-MAC=00:38:df:08:73:25;CM-QOS=1.1;CM-VER=3.1; Thu Jan 28 07:56:19 2021 (Notice (6)) CM-STATUS message sent. Event Type Code: 22; Chan ID: 159; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=08:36:00:00:00:00;CMTS-MAC=00:38:df:08:73:25;CM-QOS=1.1;CM-VER=3.1; Thu Jan 28 07:55:54 2021 (Notice (6)) CM-STATUS message sent. Event Type Code: 20; Chan ID: 159; DSID: N/A; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=08:36:00:00:00:00;CMTS-MAC=00:38:df:08:73:25;CM-QOS=1.1;CM-VER=3.1; Thu Jan 28 07:54:15 2021 (Notice (6)) CM-STATUS message sent. Event Type Code: 3; Chan ID: N/A; DSID: �; MAC Addr: N/A; OFDM/OFDMA Profile ID: N/A.;CM-MAC=08:36::00:00:00:00;CMTS-MAC=00:38:df:08:73:25;CM-QOS=1.1;CM-VER=3.1;
Observations:
The log entries are pretty telling in the sense that the modem is unhappy with the OFDM channel. Unfortunately, at this point I don't know how to proceed further and get Comcast's attention at the right level. It sure seems like my local head end (CMTS) is having an issue somewhere with Docsis 3.1.