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Connection dropouts, T4 timeouts. & just one upstream channel

Frequent Visitor

Connection dropouts, T4 timeouts. & just one upstream channel

Hi,

 

My previously stable Xfinity internet connection started acting up 2 to 3 weeks ago, seemingly right after a <1 hour service outage involving Xfinity trucks in our neighborhood - included work within the cable junction box in my front yard.  

 

Modem:  Arris SB6190

No splitter inside my house between wall and modem - same configuration as before.

 

Modem status:  https://imgur.com/a/UvmxV2D

Modem event log:  https://imgur.com/a/UxnLg3y
 
Thank you!
     Dave
Expert

Re: Connection dropouts, T4 timeouts. & just one upstream channel

Have you tried power cycling the modem ?



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Frequent Visitor

Re: Connection dropouts, T4 timeouts. & just one upstream channel

Yes, sorry, I should have mentioned:  I've power cycled the modem 4 or 5 times since the problem first appeared, but I didn't look at the signal status and event log info until after the two most recent power cycle attempts.  My posted info is from 21 hours of uptime.  

 

I also tried the Xfinity online connection testing tool, but that appeared to be mostly just another power cycle (?). 

 

     Dave

Expert

Re: Connection dropouts, T4 timeouts. & just one upstream channel

O/K try resetting it back to factory defaults by depressing and holding in the recessed reset button on the rear for 30 seconds.



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Re: Connection dropouts, T4 timeouts. & just one upstream channel

OK, I pressed the modem's recessed reset button on back panel for 30sec.

 

Looks like the issue persists -- here is modem status and event log info after 1hr 40min uptime, following SB6190 factory reset step:

 

Modem status:  https://imgur.com/a/SAFmfFS

 

Modem event log:  https://imgur.com/a/Kic1TiM

 

Thanks,

    Dave

Expert

Re: Connection dropouts, T4 timeouts. & just one upstream channel

So it could be 4 things. Either they may have taken the other upstream channels down deliberately due to some sort of maintenance / system upgrades, or there is noise ingress present in the return path that is causing the unbonding of the channels, or the modem is malfunctioning, or they put a filter on your line.

 

So even though the signal stats looked o/k at those snapshots in time, the error log entries confirm that something is going on. Perhaps there is indeed noise ingress into the line(s) somewhere.

 

There are other signal stat figures that can't be read by the modem. 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.


I'm going to escalate your issue to the Comcast corporate employees that are available to these boards. They can check the CMTS (Cable Modem Termination System) for any real time degradation and / or error reports, see your node / cable plant and modem health, and see whether or not everything is in the green zone. They can also see a history plot for the modem and poll for those upstream receive signal stats.

You should get a reply here in your topic. Good luck !



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Re: Connection dropouts, T4 timeouts. & just one upstream channel

Thanks, EG!  I'll hang on for a Comcast employee to reach out next.

 

If it comes down to a modem malfunction, I have a brand new CM1200 (unopened).  I'd probably want to upgrade from my (previously rock solid) SB6190 to the CM1200 soon in any case, but I thought it might make more sense to troubleshoot the current, relatively new issue first (assuming the modem isn't failing....).

 

     Dave 

Official Employee

Re: Connection dropouts, T4 timeouts. & just one upstream channel

Hi there, DesertRules. We appreciate you coming here for support. We understand internet connectivity issues can be super frustrating and we would like to help. We can take a look at some diagnostic reports on this end to see if we can help narrow down the cause. If you can start by sending us a private message with your name (first and last) we can continue from there.

 

To send a private message, please click our name "Comcast_Support" then select "Send a Message" on the right side.

 

We look forward to working with you. 


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Frequent Visitor

Re: Connection dropouts, T4 timeouts. & just one upstream channel

EG and all,

 

Comcast_Support and I are PM'ing -- will update the community here shortly to share what happens next.  So far, Comcast_Support says my signal levels look low from their end.  Root cause not yet determined.  May require a Comcast technician visit to my house.

 

More soon.....

 

     Dave

Frequent Visitor

Re: Connection dropouts, T4 timeouts. & just one upstream channel

All,

 

Issue still not resolved -- Just sharing the latest from my Comcast_Support PM exchanges, keeping others informed just in case the info is helpful:

 

     Dave

-----------------------------

<Follow-up PM today to Comcast_Support>:

Hi again,

 

I do need a Comcast technician visit, per my last PM with answers to questions "which days are best" and "contact number". 

Can you schedule it, or should I call Comcast customer support via phone to set it up?  

 

I've tried the following additional measures, with no improvements:

1) Changed from SB6190 modem to brand new CM1200 modem -- still only one upstream channel, and lots of uncorrectable errors on downstream channels - same as before.

2) Changed out the ground block connector in my outside junction box, and cleaned up the ground connection.  No improvements.

 

Thanks,

     Dave

Frequent Visitor

Re: Connection dropouts, T4 timeouts. & just one upstream channel

Technician visit will happen Tuesday afternoon 10/29 - will post an update afterward.
Expert

Re: Connection dropouts, T4 timeouts. & just one upstream channel

Good luck with it !



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Re: Connection dropouts, T4 timeouts. & just one upstream channel

Updates:  

 

Comcast's technician was friendly and efficient yesterday afternoon.  He said apparently my line had a filter installed by a previous Comcast technician, probably because of measured noise being injected from my house back into the Comcast system.  He said the technician should have left me a door hanger note (I didn't get one).  This is very consistent with my observation that my internet relibaility issues started right after two Comcast trucks weere in our area about 4 weeks ago and technicians did some work, including within the green metal drop box in my front yard. 

 

Anyway, my technician installed a higher-quality coax cable in my house between wall connector and modem (replaced the one I've been using for over 10 years), and he removed the filter from the cable drop box outside and tightened things up.  

 

I'm now seeing no more modem log events, and I am back to having four upstream channels instead of just one (was due to the recently installed filter).  My connection appears to have stopped dropping out intermittently, but that's with my new modem (Netgear CM1200) which was acting more resilient to this issue than was my Arris SB6190 prior to the technician visit. 

 

I am still seeing lots of correctable AND uncorrectable errors on my downstream channels (see below, 24 hours uptime).  But perhaps I won't worry about this unless we encounter user-visible problems like intermittent dropouts -- in that case I'd open a new forum thread & another service request to Comcast.

 

Thanks!

      Dave

 

ownstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 37 747000000 Hz 3.5 dBmV 38 dB 183373 207508
2 Locked QAM256 9 579000000 Hz 4.6 dBmV 39.2 dB 68236 87580
3 Locked QAM256 10 585000000 Hz 4.1 dBmV 39 dB 71955 91310
4 Locked QAM256 11 591000000 Hz 4.5 dBmV 38.7 dB 74133 94357
5 Locked QAM256 12 597000000 Hz 4.2 dBmV 38.7 dB 76329 97257
6 Locked QAM256 13 603000000 Hz 4.6 dBmV 38.8 dB 80104 100222
7 Locked QAM256 14 609000000 Hz 4.1 dBmV 38.5 dB 83884 104851
8 Locked QAM256 15 615000000 Hz 4 dBmV 38.7 dB 85088 107540
9 Locked QAM256 16 621000000 Hz 4.4 dBmV 38.6 dB 88089 108620
10 Locked QAM256 17 627000000 Hz 4.1 dBmV 38.5 dB 90231 113146
11 Locked QAM256 18 633000000 Hz 4.5 dBmV 38.8 dB 93852 114754
12 Locked QAM256 19 639000000 Hz 4 dBmV 38.6 dB 97246 118817
13 Locked QAM256 20 645000000 Hz 4.3 dBmV 38.7 dB 98337 120438
14 Locked QAM256 21 651000000 Hz 4.2 dBmV 38.3 dB 101517 122829
15 Locked QAM256 22 657000000 Hz 3.9 dBmV 38.3 dB 102915 126614
16 Locked QAM256 23 663000000 Hz 4 dBmV 38.1 dB 106268 128082
17 Locked QAM256 24 669000000 Hz 3.8 dBmV 38.2 dB 107651 132459
18 Locked QAM256 25 675000000 Hz 4.2 dBmV 37.7 dB 119496 136381
19 Locked QAM256 26 681000000 Hz 3.8 dBmV 38 dB 115501 136656
20 Locked QAM256 27 687000000 Hz 4.5 dBmV 38.1 dB 116567 138712
21 Locked QAM256 28 693000000 Hz 3.8 dBmV 38.1 dB 119789 144518
22 Locked QAM256 29 699000000 Hz 4.4 dBmV 38.4 dB 122585 146590
23 Locked QAM256 30 705000000 Hz 4.3 dBmV 38.1 dB 126648 151180
24 Locked QAM256 31 711000000 Hz 4.3 dBmV 38.3 dB 131354 155986
25 Locked QAM256 32 717000000 Hz 4.7 dBmV 38.3 dB 137181 163432
26 Locked QAM256 33 723000000 Hz 4.1 dBmV 38.2 dB 145929 170300
27 Locked QAM256 34 729000000 Hz 4.5 dBmV 38.1 dB 149535 176531
28 Locked QAM256 35 735000000 Hz 3.9 dBmV 38.1 dB 162618 187822
29 Locked QAM256 36 741000000 Hz 3.8 dBmV 37.9 dB 170899 196952
30 Locked QAM256 38 753000000 Hz 3.3 dBmV 37.8 dB 196153 218032
31 Locked QAM256 39 759000000 Hz 3.2 dBmV 37.7 dB 214704 231552
32 Locked QAM256 40 765000000 Hz 3.2 dBmV 37.7 dB 225594 245175
Expert

Re: Connection dropouts, T4 timeouts. & just one upstream channel

Please also post what the upstream channels look like now.



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Frequent Visitor

Re: Connection dropouts, T4 timeouts. & just one upstream channel

Sure!  Here is the upstream channels info, and the rest below that:

 

Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 1 5120 Ksym/sec 36500000 Hz 40 dBmV
2 Locked ATDMA 2 5120 Ksym/sec 30000000 Hz 40.5 dBmV
3 Locked ATDMA 3 5120 Ksym/sec 23500000 Hz 41 dBmV
4 Locked ATDMA 4 5120 Ksym/sec 17000000 Hz 40 dBmV
5 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
6 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
7 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
8 Not Locked Unknown 0 0 Ksym/sec 0 Hz 0.0 dBmV
 
Downstream OFDM Channels
Channel Lock
Status
Modulation /
Profile ID
Channel
ID
Frequency Power SNR /
MER
Active Subcarrier
Number Range
Unerrored
Codewords
Correctable
Codewords
Uncorrectable
Codewords
1 Locked 0 ,1 159 805000000 Hz 3.7 dBmV 38.0 dB 1126 ~ 2969 3633982900 137466459 0
2 Not Locked 0 0 0 Hz 0 dBmV 0.0 dB 0 ~ 4095 0 0 0
 
Upstream OFDMA Channels
Channel Lock Status Modulation / Profile ID Channel ID Frequency Power
1 Not Locked 0 0 0 Hz 0 dBmV
2 Not Locked 0 0 0 Hz 0 dBmV
 
Extended Upstream Transmit Power
Enable Extended Upstream Transmit Power
 
Current System Time:Wed Oct 30 17:03:34 2019
System Up Time:1 day 01:19:59
Frequent Visitor

Re: Connection dropouts, T4 timeouts. & just one upstream channel

Hey I see you expanded your original "3 things" list from 10/22 to "4 things" to include the filter scenario -- I figured you were already technically correct on noise ingress & I guess it was a combination, one led to the other. 

 

In my case, I do wish Comcast had said "hey, we saw injected noise from you, so we slapped a filter on your line - let us know if you have any problems.....".

 

Thanks for your help with this, EG!

 

      Dave