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McBob

join:2012-08-30
Salina, KS

[KS] Constant T3 timeouts for the past week (salina, ks)

Have a Motorola SB6120 modem with a ~2 month old cable drop and all other line to the modem that are serviceable by myself being brand new (no splitters).

During install of the drop, tech put an attenuator on the back of the modem, removing it has no effect on the frequency of timeouts.

Signal Values:
Without Attenuator -down

Channel ID 125  126  129  130 
Frequency 837000000 Hz 843000000 Hz 861000000 Hz 867000000 Hz 
Signal to Noise Ratio 38 dB 38 dB 38 dB 38 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
2 dBmV  2 dBmV  2 dBmV  0 dBmV  
 
Without Attenuator - up
Channel ID 3 
Frequency 31000000 Hz 
Ranging Service ID 609 
Symbol Rate 5.120 Msym/sec 
Power Level 36 dBmV 
 

The values stay similar with attenuator on, only change is power levels, which go to -1 or -2 dBmV

T3 timeouts such as :
Aug 30 2012 18:16:16 3-Critical R02.0 No Ranging Response received - T3 time-out;CM-MAC=00:23:74:f6:56:39;CMTS-MAC=64:00:f1:3f:fd:7d;CM-QOS=1.1;CM-VER=3.0;

occur frequently, as often as 2 minutes or as far as a few hours apart, most often occurring after noon.

Was using the modem for 1.5 years at previous location across town without having a T3 timeout issue such as this.


ikyuaoki

join:2011-04-12
Wichita, KS

Put it the attenuator on back and post the cable modem stats to see any difference?


McBob

join:2012-08-30
Salina, KS

As stated in the op, the only change is that drop to -1 or -2, T3 timeouts still occur.

With Attenuator - down

Channel ID 125  126  129  130 
Frequency 837000000 Hz 843000000 Hz 861000000 Hz 867000000 Hz 
Signal to Noise Ratio 38 dB 37 dB 38 dB 38 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  -1 dBmV  0 dBmV  -2 dBmV  
 
With Attenuator - up
Channel ID 3 
Frequency 31000000 Hz 
Ranging Service ID 609 
Symbol Rate 5.120 Msym/sec 
Power Level 38 dBmV 
 


ikyuaoki

join:2011-04-12
Wichita, KS
Reviews:
·Cox HSI

1 edit
reply to McBob

the two stats shows no difference, However, DOCSIS 3.0 cable modem can handle between +10dBmV to -10dBmV for downsteam channel.

for upsteam channel, it needs be at least between 45dBmV to about be 55dBmV range.

Just ask the Cox tech to boost the upsteam power channel to make the T3 timeout error away if that works.

I suggest that Coxtech1 can help you out with that upsteam power channel problem if Coxtech1 has a solution for your issue.



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

said by ikyuaoki:

Just ask the Cox tech to boost the upsteam power channel to make the T3 timeout error away if that works.

the techs won't be able to "boost upstream power channel" (sic)...upstream power is negotiated between the CMTS and CM. The CM adjusts it's return power based on how well the CMTS can "hear it"...it isn't a modifiable setting.

the techs can tweak what return power the CM establishes using pads but this would generally be used to adjust for too high a forward level and really should be adjusted long term by adjusting either the line amp or changing the tap value.

That said, adjusting levels won't likely do much for correcting incrementing T3s. If the modem is regularly logging T3s could e an indicator of a return path noise problem and that is something a tech would going to have to come out and trace down.

For the original poster, T3 errors are pretty common and in and of themselves don't necessarily indicate a service problem but can be used to correlate the cause of some service issues.

Other than noticing T3s in the modem logs, are there any other issues with your service?