C

Visitor

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7 Messages

Tue, Sep 28, 2021 9:43 PM

Repeated loss of connectivity

Greetings...I'm trying to troubleshoot a repeated loss of connectivity that has been increasing over the past year, and has risen in frequency to a few times a day now. Repeated pattern is a complete connection loss, then comes back 30-60 seconds later. In talking to my neighbors (we live in a community that shares a common Xfinity entry point), they experience similar drops. The signal drop has gotten to a point where it is completely infuriating and it's time to escalate problem solving. 

A few basics: happens on a wired connection to router as well as PC direct to cable modem. Things seem fine when I run speed tests, and speeds are within plan. Internet cable connection goes to wall to Xfinity box in garage to street, no splitters along the way. No kinks in cabling along the way from what I can see. I use my own router & cable modem, which have worked without issues for a couple of years until the drops started. I live in a relatively new neighborhood and home (~5 years old).

I see folks exchanging connection logs on other forum posts, not sure how to do that...could someone share details how to do that? Then of course happy to remove all personal data and share for follow-up.

Thanks a bunch for your help!

Visitor

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7 Messages

1 m ago

Ah...I figured out how to log onto the modem and get the event log...let's try a copy/paste on that with MAC xxx'd out...

Time Priority Description
1970-1-1, 00:00:38 Notice (6) Honoring MDD; IP provisioning mode = IPv6
1970-1-1, 00:00:27 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:21 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
2021-9-15, 09:45:34 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 09:45:26 Critical (3) SYNC Timing Synchronization failure - Failed to receive MAC SYNC frame within time-out period;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 09:45:20 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 09:45:16 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 09:45:14 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 09:44:53 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=xxx;CMTS-MAC=xxx:40;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 09:44:50 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 09:44:38 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=a0:04:60:95:d4:58;CMTS-MAC=00:38:df:08:5a:40;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 09:44:37 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 09:44:30 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 09:44:29 Critical (3) SYNC Timing Synchronization failure - Failed to acquire FEC framing;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 09:44:22 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 09:44:17 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 02:07:30 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 01:59:32 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-15, 01:45:29 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-10, 15:13:43 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-10, 15:01:06 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=axxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
2021-9-10, 15:00:48 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-10, 14:57:28 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
1970-1-1, 00:14:05 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:12:51 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:12:39 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:11:14 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:10:00 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:08:55 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:07:35 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:06:24 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:04:51 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:03:47 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:02:33 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:01:32 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:27 Critical (3) No Ranging Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
1970-1-1, 00:00:21 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
2021-9-10, 14:17:16 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
2021-9-10, 12:58:42 Critical (3) Started Unicast Maintenance Ranging - No Response received - T3 time-out;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.1;CM-VER=3.0;
1970-1-1, 00:00:21 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;;CM-MAC=xxx;CMTS-MAC=xxx;CM-QOS=1.0;CM-VER=3.0;
BruceW

Gold Problem Solver

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23K Messages

1 m ago

Network connection problems are often due to poor coax connections or damaged coax cable, usually in or near your home. If you want to troubleshoot this yourself, please see Internet Troubleshooting Tips. If you still need help, please post your Internet plan speed and the following information from your modem or gateway:

  • model number
  • downstream power levels and SNR
  • upstream power levels

If you can't find the problem or you'd rather have Comcast take care of it, call them at the phone number on your bill or 1-800-Comcast, or use one of the options on https://www.xfinity.com/support/contact-us/. It's not likely they can fix the problem remotely. If not, insist they send a tech out to identify the cause and correct it.

If the tech finds bad coax, splitters, amplifiers, or connections in your home (even if Comcast originally supplied them) you'll probably have to pay for the visit unless you have their Service Protection Plan ( https://www.xfinity.com/support/articles/service-protection-plan, closed to customers that don't already have it). If the trouble is due to a faulty Comcast rental device or anything outside your home you shouldn't be charged.

Visitor

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7 Messages

@BruceW Hi Bruce --thanks for taking a look and sharing insight. My internal cabling is all straight ahead and tidy...5 year old construction, no splitters, even at the garage entry box. No idea what the junction at the street looks like. Had another two connection losses this morning in fact. I'm on Performance Pro + plan (think that's 200 down / 6 up). Based on my earlier experience with neighbors and this equipment, connection loss is clearly starting outside the property. 

Using a NetGear CM500...from the admin panel...

Downstream Bonded Channels
Channel Lock Status Modulation Channel ID Frequency Power SNR Correctables Uncorrectables
1 Locked QAM256 13 495000000 Hz 7.9 dBmV 38.6 dB 0 0
2 Locked QAM256 1 423000000 Hz 7.6 dBmV 38.6 dB 0 0
3 Locked QAM256 2 429000000 Hz 7.8 dBmV 38.7 dB 0 0
4 Locked QAM256 3 435000000 Hz 7.9 dBmV 38.7 dB 0 0
5 Locked QAM256 4 441000000 Hz 7.8 dBmV 38.6 dB 0 0
6 Locked QAM256 5 447000000 Hz 7.9 dBmV 38.6 dB 0 0
7 Locked QAM256 6 453000000 Hz 7.9 dBmV 38.6 dB 0 0
8 Locked QAM256 7 459000000 Hz 8.1 dBmV 38.7 dB 0 0
9 Locked QAM256 8 465000000 Hz 8.1 dBmV 38.7 dB 0 0
10 Locked QAM256 9 471000000 Hz 8.1 dBmV 38.7 dB 0 0
11 Locked QAM256 10 477000000 Hz 8.1 dBmV 38.6 dB 0 0
12 Locked QAM256 11 483000000 Hz 8 dBmV 38.6 dB 0 0
13 Locked QAM256 12 489000000 Hz 8 dBmV 38.6 dB 0 0
14 Locked QAM256 14 507000000 Hz 7.8 dBmV 37.7 dB 0 0
15 Locked QAM256 15 513000000 Hz 8 dBmV 38.5 dB 0 0
16 Locked QAM256 16 519000000 Hz 8 dBmV 38.4 dB 0 0
 
Upstream Bonded Channels
Channel Lock Status US Channel Type Channel ID Symbol Rate Frequency Power
1 Locked ATDMA 2 5120 Ksym/sec 22800000 Hz 43.2 dBmV
2 Locked ATDMA 1 5120 Ksym/sec 16400000 Hz 43.2 dBmV
3 Locked ATDMA 3 5120 Ksym/sec 29200000 Hz 43.2 dBmV
4 Locked ATDMA 4 5120 Ksym/sec 35600000 Hz 43.2 dBmV
BruceW

Gold Problem Solver

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23K Messages

1 m ago

The signal levels, SNR, and error counts you posted are OK, but there are other signal stats that the modem doesn't report. The modem is approved for speeds up to about 370 Mbps, so that should be OK. As stated above, you'll need to contact Comcast and have them take a look at the problem.

Visitor

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7 Messages

@BruceW Hi Bruce...thank you again for taking a look. I actually thought I was contacting Comcast by posting here -- they're already contacted me for a follow-up support review (!?) -- and I prefer not calling them if I don't have to, as I find the phone service to be annoying and long. I'll start going down that route.

Meanwhile, please do not consider this topic closed, I'll circle back with what I hope the final resolution is. Also, received two more disconnects this morning...while we've established that my equipment is fine, I do wish there was a better tool in our troubleshooting bag to establish the pattern of disconnects and signal drops.

Official Employee

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289 Messages

Hello, @ckerwien. We appreciate you making us aware of your intermittent internet connection. I would be more than happy to help troubleshoot some more to find the root cause of this problem.

 

In order to get started can you please send me a private message to Xfinity Support with your full name and full address by clicking the chat icon in the top right?

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick
EG

Expert

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89.9K Messages

1 m ago

@ckerwien The signal stats are o/k but the error log entries indicate that something is going on. Perhaps there is noise ingress into the line(s) /  an upstream channel-return path impairment somewhere.


As @BruceW had stated, 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 will be able to poll the CMTS to see whether or not everything is in the green zone, see your node / cable plant and modem health, and also see a history plot for the modem. You should get a reply here in your topic. Good luck !

(edited)

EG

Expert

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89.9K Messages

1 m ago

@ckerwien @XfinityRaul 

Please post any possible solutions for the issue here in the open forums so that all readers here may benefit from the exchange / info. This is in keeping with the spirit for which these public help forums were originally intended. Thank you.

Visitor

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7 Messages

1 m ago

Thank you @EG  @XfinityRaul for reaching out and taking a look, appreciate the additional eyes on the topic, as the issues has been super frustrating to deal with.

I called up Support, Tech on site is happening this upcoming Sunday, will report back what the outcome of that is.

General feedback on the phone cycle: voice AI bot is an interesting way to filter & fork calls to the right location, I can't stand working with it, as I'm forced into pre-determined logic streams that doesn't really apply to my situation. Once I got past that, the customer service rep was fantastic and good to talk to.

Will report back after next steps!

EG

Expert

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89.9K Messages

@ckerwien

Quite welcome ! 🙂 And please do. 

I am not a Comcast Employee.
I am a Customer Expert volunteering my time to help other customers here in the Forums.
We ask that you post publicly so people with similar questions may benefit from the conversation.

Was your question answered? Please mark an Accepted Answer!tick

Visitor

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7 Messages

1 m ago

Hi folks -- quick update here...just received a call from "Advanced Technical Support" notifying me that the issues has been resolved on the Comcast side. (!?) I asked for more detail on that, and the rep just said that there was happening on the backend and everything should be okay now. Clearly she didn't more information than that, but I would like to have a little more transparency on what backend work could be happening, so I can be aware of symptoms and then do appropriate follow-up. Not looking to get too deep into how Comcast handles their network operations and maintenance of course, but a little more insight would be helpful, as this issue is been driving us absolutely nuts.

Will post another update after the service visit on Sunday.

Official Employee

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3K Messages

Hey @ckerwien! We hope you are doing well and having a good weekend so far. We just wanted to check to see how things went with your service visit. Was the tech able to spot any problems?

I am an Official Xfinity Employee.
Official Employees are from multiple teams within Xfinity: CARE, Product, Leadership.
We ask that you post publicly so people with similar questions may benefit from the conversation.
Was your question answered? Please, mark a reply as the Accepted Answer.tick

Visitor

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7 Messages

22 d ago

Thanks everyone for watching this issue and following-up -- although the Xfinity tech was super insightful and helpful, the issue was not resolved and continues to occur today. I am currently thinking through next steps, so let me summarize the visit highlights as well as some of Xfinity business practices that occurred during this support case...

  • Let me start by saying the tech was absolutely terrific: verified there is indeed an connectivity issue with modem dropping packets.
  • He swapped out owner-installed (ahem) coax cable from wall to modem with original, as I had swapped in a 6ft cable with an original 20ft cable installed in another room hoping the decreased distance would improve things...it didn't, nor did the cut down length xfinity cable with better shielding. Apparently coax cables bought from stores are meant for AV use not internet connectivity. No matter, issue continued with both cables, and at this point we're going through the punch list each connection at a time.
  • Observed there is noise on the electricity provided to the cable, which could be a culprit to dropping packets. Modems use the coax line to stay grounded, don't have a third prong, at least mine doesn't, and are more susceptible to electric variations. We tried both my office, which is 'home' for the modem, as well as in the garage directly attached to the xfinity house panel...the noise was actually worse in the garage than my office (?!), possibly indicating some issue among the wiring connections in the circuit breaker panel or in the house leading up to my office. Let me pause at this point for a few thoughts...
  • Is the modem being flakey? Maybe, maybe not. It's been in service for about 3 years, has been mostly reliable until this issue came up a year ago. I can swap it out, which takes some effort and time, as need to register a new modem back to Xfinity and get authorized. And I've heard a bunch of stories about other customers going that cycle with the issue not being resolved so ends up being a waste of time and increased frustration. But it's there. I'm currently using a CM500, which is Netgear's common modem from a couple of years ago, they have an upgraded CM600 now, and Motorola apparently has something. Both are on the approved xfinity list, not really sure if these are better.
  • Is the electricity in my house an issue? Gee this is a hard one to understand. It's 5 year old construction. If electricity to the modem is an issue...then why does that happen? The house electricity has noise...the lights stay on, the computer stays on, the router stays on, the frig stays on. If modems are so sensitive to noise, then why isn't there a modem that just deals with that? Or can't I just put it on a surge protector strip of some kind? The tech mentioned he has seen breaker panel wiring develop issues over time, and requires an electrician to help diagnose, and also that gigabit plan users are just as impacted as I am. Oy. Can't believe I'm the only one dealing with this.
  • We verified that the xfinity cable connection from street to house is fine.
  • We also verified that download/upload speeds are according to plan.
  • So...at this point I'm thinking through next steps. As I read through other Q&A in various support forums, the common response at this point is "looks like you have a problem with the lines in your house, need to figure that out, may need an electrician". This is fundamentally weird to me - cable modems can't handle noise variations in an electrical line when other devices in the home do? Unh.

  • Separate and related topic: Xfinity has two business practices during my support case that I wish would not be repeated...
    1) The follow-up call from "advanced tech support" saying the issue was resolved, which happened soon after I placed support ticket. This was confusing to me, the caller did not have any detail why the issue was resolved, but did not close the ticket and let the tech visit still happen. Whew.
    2) Soon after I posted a message on this forum, I was asked about my support experience. Soon after the tech left my house, I was asked how likely I was to recommend Xfinity to someone else. This is the business operations team making far too aggressive surveys to customers without knowing a customer's experience. Please ask them to stop this practice. I'm perfectly okay being asked to rate quality of custom support after an incident has been resolved, not before, and not about helping xfinity with their net promoter score.

    And to be clear: the folks chiming into this thread, as well as the initial support call and tech, have been great. I am grateful for everyone's insight and knowledge on this. I'm referring to some business practices above that should be changed.

So...I need to let all this marinate for a bit and think through next steps. Wondering if there is a better modem solution with better built-in electrics, or if an add-on of some kind would be helpful (surge protector, whatever). I understand an amplifier isn't going to help, I don't need a bad signal boosted any further.

Thanks again.

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