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mclasser

join:2011-12-12

1 edit

[VA] T4 Timeout

I bought an SB6121 about a month ago an have been happy with it so far. I checked the modem logs this morning and saw it rebooted in the middle of the night due to a T4 timeout. It hasn't done this before and I was wondering what such a timeout meant. Since it happened around midnight I was thinking it may have just been Cox doing some maintenance.

Downstream Bonding Channel Value
Channel ID 68 65 66 67
Frequency 393000000 Hz 375000000 Hz 381000000 Hz 387000000 Hz
Signal to Noise Ratio 36 dB 36 dB 36 dB 36 dB
Downstream Modulation QAM256 QAM256 QAM256 QAM256
Downstream Power Level
-5 dBmV -5 dBmV -5 dBmV -5 dBmV

Upstream Bonding Channel Value
Channel ID 3 1 2 4
Frequency 26000000 Hz 17800000 Hz 21100000 Hz 32500000 Hz
Ranging Service ID 6878 6878 6878 6878
Symbol Rate 5.120 Msym/sec 2.560 Msym/sec 2.560 Msym/sec 5.120 Msym/sec
Power Level 38 dBmV 37 dBmV 38 dBmV 38 dBmV
Upstream Modulation [3] QPSK
[3] 64QAM
[3] QPSK
[2] 16QAM
[3] QPSK
[2] 16QAM
[3] 64QAM
[3] QPSK
[3] 64QAM



bbeesley
VIP
join:2003-08-07
Richardson, TX
kudos:5

said by mclasser:

I was wondering what such a timeout meant.

The T4 timer is incremented when the cable modem doesn't receive a downstream ranging opportunity. The CMTS is required to send a ranging response "answer" to the cable modem with "T4" seconds (T4 is a configurable value)...if the cable modem fails to hear back from the CMTS within that amount of time will go ahead and reinitialize.

This is usually caused by noise, but in your instance since it happened only once and during a maintenance window your hypothesis that it was maintenance related is sound.