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Connection dropping

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Connection dropping

I have a Motorola Surfboard SB6121 and have had issues with the connection dropping pretty much daily around the same time (~9AM). Comcast lists this modem as "not supported", so I'm not sure if it's just because this modem is really old but I'd like to make sure before getting a new one

 

Signal:

Downstream Bonding Channel Value
Channel ID 20  21  22  24 
Frequency 609000000 Hz  615000000 Hz  621000000 Hz  633000000 Hz 
Signal to Noise Ratio 36 dB  36 dB  37 dB  37 dB 
Downstream Modulation QAM256  QAM256  QAM256  QAM256 
Power Level
The Downstream Power Level reading is a snapshot taken at the time this page was requested. Please Reload/Refresh this Page for a new reading
0 dBmV   0 dBmV   0 dBmV   0 dBmV  

 

Upstream Bonding Channel Value
Channel ID 37  38  39  40 
Frequency 17300000 Hz  23700000 Hz  30300000 Hz  36700000 Hz 
Ranging Service ID 13424  13424  13424  13424 
Symbol Rate 5.120 Msym/sec  5.120 Msym/sec  5.120 Msym/sec  5.120 Msym/sec 
Power Level 46 dBmV  46 dBmV  46 dBmV  45 dBmV 
Upstream Modulation [3] QPSK
[3] 64QAM
 
[3] QPSK
[3] 64QAM
 
[3] QPSK
[3] 64QAM
 
[3] QPSK
[3] 64QAM
 
Ranging Status Success  Success  Success  Success 

 

Signal Stats (Codewords) Bonding Channel Value
Channel ID 20  21  22  24 
Total Unerrored Codewords 66434631  66217646  66227349  461356074 
Total Correctable Codewords 265109  102790  126940  186505 
Total Uncorrectable Codewords 375718  253595  275347  377819 

 

Logs:

Time Priority Code Message
Jan 18 2018 10:00:47 3-Critical T05.0 SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:06:58 6-Notice N/A MDD Recovery following MDD Loss;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:06:57 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:06:57 5-Warning N/A DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:06:57 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:06:57 5-Warning N/A DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:06:57 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:06:57 5-Warning N/A DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:06:33 3-Critical T05.0 SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:05:50 6-Notice N/A MDD Recovery following MDD Loss;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:05:49 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:05:49 5-Warning N/A DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:05:49 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:05:49 5-Warning N/A DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:05:49 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:05:49 5-Warning N/A DS Partial Service Fallback: MDD Lost-> CM in DOCSIS 3.0 Recovery Mode ;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:05:48 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:05:25 3-Critical T05.0 SYNC Timing Synchronization failure - Loss of Sync;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:04:42 6-Notice N/A MDD Recovery following MDD Loss;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Jan 18 2018 09:04:39 5-Warning T202.0 Lost MDD Timeout;CM-MAC=b0:77:ac:29:db:1d;CMTS-MAC=00:01:5c:68:b0:76;CM-QOS=1.1;CM-VER=3.0;
Expert

Re: Connection dropping

Only the Comcast supplied rental versions of the 6121 are on their "End Of Life" list. The retail available versions are not EOL.

 

The stats as read at the modem level at that moment in time were o/k but there are three additional signal stats that can cause this which can't be read by the modem. They can only be read from their end by them polling the CMTS (Cable Modem Termination System) at the local headend facility.

They are the "Upstream Rx Power" (Upstream Receive Power Level), the "Upstream SNR Ch." (Upstream Signal To Noise Ratio), and the "Upstream ICFR" (In Channel Frequency Response). These are as equally important in diagnosing connectivity issues as are the modem's stats.

You can call in and ask what these figures are. The Upstream Receive Power Level should fall within the range of -2dB to +2dB with 0dB being in the middle and perfect.

The Upstream SNR should be least 31dB, and the higher it is the better.

The ICFR should be no higher than 2 dB.

You could have an intermittent noise ingress issue in only the upstream channel(s) / return path only somewhere.

They will be able to see whether or not everything is in the green zone and also see a history plot for the modem.