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EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:9
reply to Morac

Re: [Connectivity] Modem is reporting continuous T4 errors.

said by Morac:

Second, if you are seeing upload issues, it could be an upstream signal problem.

FWIW, due to the way TCP ACK (Acknowledgement) works, upstream / return impairments can affect the downstream as well.


Morac
Cat god

join:2001-08-30
Riverside, NJ
kudos:1
Reviews:
·Comcast

said by EG:

said by Morac:

Second, if you are seeing upload issues, it could be an upstream signal problem.

FWIW, due to the way TCP ACK (Acknowledgement) works, upstream / return impairments can affect the downstream as well.

True but ACK packets are normally much smaller than upstream data packets so unless things are really bad, they are less likely to be affected.
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Morac
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join:2001-08-30
Riverside, NJ
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Reviews:
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1 edit
reply to Morac

Just mentioning that despite this "being looked into", the constant T4 errors on one channel continue. Fortunately it's not affecting speeds or latency, but it's kind of like skydiving without a backup chute.
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instigator

join:2012-06-24
Fort Lauderdale, FL
reply to Morac

Thought I'd follow up since I posted in here... My zoom modem came in the mail last Friday. Once I connected it I had 8 channels bonded DS 3 channels bonded US (including the channel I was/am seeing with errors), but had absolutely terrible connection speeds...less than 1M. I followed the wire in the attic and found an extra splitter that was unnecessary so I put a straight-through connector in it.

BOOM! I instantly saw constant 35M+ download speeds and 5M+ uploads on the speed test.

Everything seems to be running smooth



Morac
Cat god

join:2001-08-30
Riverside, NJ
kudos:1
Reviews:
·Comcast
reply to Morac

I checked into the status of this since it's been about a month and I was told that "maintenance has been completed to stabilize channels", but I'm still getting the T4 errors though.

I'm having ComcastWill look at it, but while he was looking at it, the modem rebooted. He said he didn't do that, but I haven't seen a reboot the entire time this has been happening.

He's going to try pinging my local network group to look at the CMTS again, but I'm guessing they aren't really doing anything about it since one or more of the channels is still working.

Is there for support to actually see if the CMTS is having problems (other than looking at signals)?
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threadsent

join:2012-09-08

any updates? i have the exact same problem. i get t4 errors all day every minute on my log.
i have near optimal power/signal levels.



Morac
Cat god

join:2001-08-30
Riverside, NJ
kudos:1
Reviews:
·Comcast

said by threadsent:

any updates? i have the exact same problem. i get t4 errors all day every minute on my log.
i have near optimal power/signal levels.

I had a service outage in the middle of the night about 2 or 3 weeks ago. When it came back up, the problem was fixed. My guess is they finally replaced the bad part.

Functionally, I haven't noticed a difference. Upload speed might be a tiny bit faster, but nothing else changed.
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DrDrew
That others may surf
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join:2009-01-28
SoCal
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1 edit

1 recommendation

reply to Morac

said by Morac:

pstream Frequency: 36200108 Hz29399949 Hz22000000 Hz
Upstream bandwidth: 6400000 Hz6400000 Hz3200000 Hz
...
Is it possible for one of the 3 upstream channels to be having T4 errors, but the other 2 work okay?

Yes.

For example your middle upstream channel is centered on 29.4 mhz and is 6.4 mhz wide. 29.4 - 3.2 (half the channel width) is 26.2 mhz. The CB radio frequencies are from 26.965 to 27.405 MHz, so the entire CB radio band is within that lower half of your middle upstream channel.

It's possible a crack in the cable is letting local CB interference or a local CB radio placed close to cable equipment is overpowering it's shielding.

This is a pretty common problem with cable systems running along major trucking routes.

It would've been better if the 29.4 Mhz channel was 3.2 Mhz wide and the 22 Mhz upstream was 6.4 Mhz wide... that would've left a gap from 25.2 to 27.8 Mhz for the CB band to fit into.
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Morac
Cat god

join:2001-08-30
Riverside, NJ
kudos:1
Reviews:
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reply to Morac

Problem is back again as of yesterday. My signals look good.


Downstream
Channel Frequency: 675000488 Hz 657001099 Hz 668999146 Hz 681001709 Hz
Modulation: 256 QAM 256 QAM 256 QAM 256 QAM
Signal strength: 8.8028 dBmV 8.8512 dBmV 9.2323 dBmV 8.1789 dBmV
Signal noise ratio: 37.356 dB 36.844 dB 37.356 dB 37.356 dB

Upstream
Channel Id: 7 8 9
Upstream Frequency: 36200215 Hz 29399984 Hz 22000000 Hz
Upstream bandwidth: 6400000 Hz 6400000 Hz 3200000 Hz
Transmission signal strength: 43.2500 dBmV 43.5000 dBmV 43.2500 dBmV


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EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:9
reply to Morac

Don't forget about the uSNR (upstream Signal to Noise Ratio) number that can only be read from their end. It should be at least 30 dB and higher is better. Call in when you are experiencing the problem and see if it is in spec.


WaldorfMD

join:2012-11-30
reply to Morac

At least your not seeing constant disconnects when connected to the drop:

Time Not Established Critical (3) DHCP WARNING - Non-critical field invalid in response.
Time Not Established Critical (3) No Ranging Response received - T3 time-out
Time Not Established Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Time Not Established Critical (3) DHCP WARNING - Non-critical field invalid in response.
Fri Nov 30 19:53:39 2012 Critical (3) DCC aborted unable to communicate on new upstream channel
Fri Nov 30 19:53:39 2012 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Fri Nov 30 19:33:48 2012 Critical (3) DHCP WARNING - Non-critical field invalid in response.
Fri Nov 30 19:33:34 2012 Critical (3) DCC aborted unable to communicate on new upstream channel
Fri Nov 30 19:33:34 2012 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Fri Nov 30 19:28:43 2012 Critical (3) DHCP WARNING - Non-critical field invalid in response.
Fri Nov 30 19:28:31 2012 Critical (3) DCC aborted unable to communicate on new upstream channel
Fri Nov 30 19:28:31 2012 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Fri Nov 30 19:08:38 2012 Critical (3) DHCP WARNING - Non-critical field invalid in response.
Fri Nov 30 19:08:24 2012 Critical (3) DCC aborted unable to communicate on new upstream channel
Fri Nov 30 19:08:24 2012 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Fri Nov 30 18:58:34 2012 Critical (3) DHCP WARNING - Non-critical field invalid in response.
Fri Nov 30 18:58:19 2012 Critical (3) DCC aborted unable to communicate on new upstream channel
Fri Nov 30 18:58:19 2012 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Fri Nov 30 18:48:27 2012 Critical (3) DHCP WARNING - Non-critical field invalid in response.
Fri Nov 30 18:48:14 2012 Critical (3) DCC aborted unable to communicate on new upstream channel
Fri Nov 30 18:48:14 2012 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Fri Nov 30 18:43:28 2012 Critical (3) DHCP WARNING - Non-critical field invalid in response.
Fri Nov 30 18:43:14 2012 Critical (3) DCC aborted unable to communicate on new upstream channel
Fri Nov 30 18:43:14 2012 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Fri Nov 30 17:55:49 2012 Critical (3) DHCP WARNING - Non-critical field invalid in response.
Fri Nov 30 17:55:39 2012 Critical (3) No Ranging Response received - T3 time-out
Fri Nov 30 17:55:32 2012 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Fri Nov 30 17:52:57 2012 Critical (3) DCC aborted unable to communicate on new upstream channel
Fri Nov 30 17:52:57 2012 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Fri Nov 30 17:28:07 2012 Critical (3) DHCP WARNING - Non-critical field invalid in response.
Fri Nov 30 17:27:49 2012 Critical (3) DCC aborted unable to communicate on new upstream channel
Fri Nov 30 17:27:49 2012 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...


WaldorfMD

join:2012-11-30

we don't see a problem ... really..nothing at all, with the second modem connected directly to your drop, let me pull out the RF Meter...HRMM... is 66dBmV within DOCSIS 1.1 or 2.0 spec, heck is it even in 3.0 Spec.... ...silence....*crickets pointing and laughing*



EG
The wings of love
Premium
join:2006-11-18
Union, NJ
kudos:9

1 edit

said by WaldorfMD:

let me pull out the RF Meter...HRMM... is 66dBmV within DOCSIS 1.1 or 2.0 spec, heck is it even in 3.0 Spec.... ...silence....*crickets pointing and laughing*

*Ahem*, is that forward or return power ???

WaldorfMD

join:2012-11-30
reply to Morac

That's the return path that tries to lock and acquire on return path frequency 36.0MHz.

Forward signal strength is 3.1-6.7 dBmV