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3 Messages

Wednesday, July 19th, 2023 8:23 PM

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Intermittent Connectivity Issues T3 and T4 Timeouts Plus High Downstream Power

Hi everyone, I have been experiencing intermittent internet connection issues for the past week. I have never had issues like this in the 3 years I've been using Xfinity at my apartment. It all began last week after Xfinity resolved an outage in my area. I will see my internet connection drop off multiple times a day and then reconnect about 2 minutes later. It happens roughly every 2-3 hours. My modem doesn't seem to be powering down or anything during these drops in connection. I checked the event log for my modem and am posting the results below:

Time Priority Description
1970-1-1, 00:00:46 Notice (6) Honoring MDD; IP provisioning mode = IPv6
1970-1-1, 00:00:40 Notice (6) WiFi Interface [wl1] set to Channel 153 (Side-Band Channel:N/A) - Reason:INIT
1970-1-1, 00:00:40 Notice (6) WiFi Interface [wl0] set to Channel 11 (Side-Band Channel:N/A) - Reason:INIT
1970-1-1, 00:00:37 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;
2023-7-19, 14:04:36 Critical (3) Resetting the cable modem due to docsDevResetNow
2023-7-19, 13:22:55 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-19, 13:21:49 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-19, 11:15:07 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-19, 11:14:02 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-19, 09:18:15 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-19, 09:17:09 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-19, 05:20:22 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-19, 03:22:20 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-19, 03:21:15 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-19, 01:21:15 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-19, 01:20:10 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-18, 23:15:22 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-18, 23:14:17 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-18, 21:22:20 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-18, 21:21:16 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-18, 19:16:10 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-18, 19:15:05 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-18, 17:24:01 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-18, 17:22:56 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-18, 15:23:48 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-18, 15:22:43 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-18, 11:11:19 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-18, 09:21:51 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-18, 09:20:46 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-18, 07:15:19 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-18, 05:24:23 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-18, 05:23:18 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-18, 03:21:32 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-18, 03:20:27 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-18, 01:16:35 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-17, 23:23:29 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-17, 23:22:24 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-17, 21:24:02 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;
2023-7-17, 21:22:57 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;
2023-7-17, 19:24:44 Critical (3)

Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;

Startup Procedure
Procedure Status Comment
Acquire Downstream Channel 591000000 Hz Locked
Connectivity State OK Operational
Boot State OK Operational
Security Enabled BPI+
IP Provisioning Mode Honor MDD honorMdd(4)
 
Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 28 591000000 Hz 10.6 dBmV 44.4 dB 0 0
2 Locked QAM256 21 549000000 Hz 10.7 dBmV 44.8 dB 0 0
3 Locked QAM256 22 555000000 Hz 10.8 dBmV 44.8 dB 0 0
4 Locked QAM256 23 561000000 Hz 10.6 dBmV 44.6 dB 0 0
5 Locked QAM256 24 567000000 Hz 10.6 dBmV 44.8 dB 0 0
6 Locked QAM256 25 573000000 Hz 10.6 dBmV 44.8 dB 0 0
7 Locked QAM256 26 579000000 Hz 10.5 dBmV 44.7 dB 0 0
8 Locked QAM256 27 585000000 Hz 10.5 dBmV 44.5 dB 0 0
9 Locked QAM256 29 597000000 Hz 10.6 dBmV 44.2 dB 0 0
10 Locked QAM256 30 603000000 Hz 10.5 dBmV 44.3 dB 0 0
11 Locked QAM256 31 609000000 Hz 10.7 dBmV 44.6 dB 0 0
12 Locked QAM256 32 615000000 Hz 11 dBmV 44.9 dB 0 0
13 Locked QAM256 33 621000000 Hz 10.9 dBmV 44.4 dB 0 0
14 Locked QAM256 34 627000000 Hz 10.8 dBmV 40.7 dB 0 0
15 Locked QAM256 35 633000000 Hz 10.9 dBmV 42.3 dB 0 0
16 Locked QAM256 36 639000000 Hz 11 dBmV 41.3 dB 0 0
17 Locked QAM256 37 645000000 Hz 11.3 dBmV 44.4 dB 0 0
18 Locked QAM256 38 651000000 Hz 11.4 dBmV 45.4 dB 0 0
19 Locked QAM256 39 657000000 Hz 11.3 dBmV 45.5 dB 0 0
20 Locked QAM256 40 663000000 Hz 11.2 dBmV 45.2 dB 0 0
21 Locked QAM256 41 669000000 Hz 11 dBmV 44.6 dB 0 0
22 Locked QAM256 42 675000000 Hz 11.1 dBmV 44.6 dB 0 0
23 Locked QAM256 43 681000000 Hz 11 dBmV 44.7 dB 0 0
24 Locked QAM256 44 687000000 Hz 11 dBmV 44.6 dB 0 0
 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 1 5120 Ksym/sec 16400000 Hz 40.8 dBmV
2 Locked ATDMA 2 5120 Ksym/sec 22800000 Hz 41.2 dBmV
3 Locked ATDMA 3 5120 Ksym/sec 29200000 Hz 40.7 dBmV
4 Locked ATDMA 4 5120 Ksym/sec 35600000 Hz 40.7 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
 

From what little research I already did, it looks like my downstream power could be somewhat high? Perhaps that is part of the issue? I have never looked at my event log or power levels before so I am unsure if these are normal for me or not.

I appreciate any help as this issue has been highly disruptive for me while I work from home.

Thank you

Expert

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110.3K Messages

2 years ago

@jgagliardi2 

Please redact all of the CM MAC and the CMTS MAC addresses from your error log entries for your privacy. They are considered to be personal information. The posting of personally identifiable information is a violation of their forum guidelines. The forum bot will not allow your post to be seen publically. It flagged your post as "Private".

Expert

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110.3K Messages

2 years ago

No worries ! This may or may not be the root cause of the problem (YMMV) but it should be addressed regardless.


The downstream power is indeed on the high side. It may be over-driving the front-end receiver circuit of the modem. That can cause random disconnects, spontaneous re-booting of the modem, speed, packet loss, latency problems, and the un-bonding of channels.


Is there a drop amplifier on the coax cable line leading to the modem ? If so, try removing / bypassing it and see. If not, you can try installing a -6 dB forward path-only attenuator pad such as this one on the coax port on the rear of the modem to knock that power level down and see;


https://www.amazon.com/FPA6-54-Forward-Attenuator-DOCSIS-Internet/dp/B08KTRC3XZ  


It won't affect the upstream power level which is within spec.

What is the exact make and model number of the modem / gateway device ?

Is this with a WiFi connection ? If so, as a test, does a computer / device that is hardwired directly to the router / gateway device with an ethernet cable have the same intermittent internet connection problem ?

With this test, we are trying to isolate this down to being either a WiFi-only problem or a problem with the general connection to the Comcast system which would of course affect both.

(edited)

Visitor

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3 Messages

@EG​ Thank you for the response, my modem is a Netgear AC1900 WiFi Cable Modem Router Model:C7000. I've had it since 2019 but has always been highly reliable.

My desktop is always hardwired into the modem via ethernet and experiences the disconnects at the same time as my wifi devices. 

I just scheduled an Xfinity tech to come to my apartment on Saturday, the rep I spoke with indicated that there is scheduled maintenance in my area this Friday so it's possible that may resolve my issue.

As far as I can tell there is no drop amplifier I can see on my cable, so perhaps the attenuator may help this issue.

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