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Frequent disconnects, degraded service, no connection registration

Frequent Visitor

Frequent disconnects, degraded service, no connection registration

I have my own ARRIS SurfBoard SB6121 modem that I've used for almost 4 years without issue. The setup of everything in my current location is pretty much untouched, was working fine for over 2 years until the recent disconnects and larger issues I started seeing today. A few weeks ago I downgraded my Internet speeds from 120Mbps to 60Mbps. It may be a complete coincidence, but afterward I experienced one or two internet dropouts (that I was aware of) a week. Yesterday I lost internet 2-3 times, today I lost it and it was down for over an hour. There have been no service interruptions in my area and my neighbors indicate their internet has seemed to be fine (separate coax cabling). I'm hoping to get advice pointing to a possible connection issue or something else, not wanting to buy a replacement modem unless it seems like the likely cause. Prior today I was seeing about 70Mbps download and 6Mbps upload, very consistently. Now (if I have internet at all) I get around 20Mbps down and 0.9Mbps up.

 

The logs on the modem are flooded non-stop with T3 and T4 timeout errors;

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

-Started Unicast Maintenance Ranging - No Response received - T3 time-out

I've also seen some messages where 13 or so timeout messages were recieved and it forced a modem reboot.

 

On the status page most things are considered "Not started". In cases where these actually do get completed everything is successful down to "Register Connection", this fails. It says the "Cable Modem Status" is offline both when the other status' are done and not started, the difference being in the case where they are "Done" instead of "Not started" (with failed register connection) there is no working internet connection.

status.JPG

 

On the signal side of things, for the upstream I only seem to be getting 1 channel with successful ranging status. I believe the downstream SnR is fine, but could be higher and that the upstream power level is borderline too high. I live in a house split into 4 apartments so the cabling is a bit of a mess, but it looks like I have 2 coax extentions within the house and am also off a splitter. Setting up the modem before a splitter and extention does lower the upstream power level a tad but doesn't result in any speedtest changes or changes in modem status.

 

Here is a screencapture of current state, after the splitter and extensions:

status_latest.JPG

 

Here is a screen capture of before the splitter and a single extension:

beforesplitter.PNG

You can see the upstream and downstream channel IDs don't match, I have been seeing that a lot as well. The ranging status for the latter 3 channels is "Other" in this case and during a speedtest I was unable to get the upload portion to work at all. The downstream power level in this case is also positive instead of negative. The Downstream SnR is higher. Clearly if I could get a new direct connection, that would help the numbers- but that doesn't seem to be the issue since things still don't work setup that far down the line.

 

Any advice on things to try or investigate is appreciated!

Expert

Re: Frequent disconnects, degraded service, no connection registration

Can't see your pics. Since you are a new poster, they likely need to be approved by a Forum Admin. Or you may need to make a minimum number of posts.

You could try hosting them at one of those free third-party pic hosting sites and post the link to them here.



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Frequent Visitor

Re: Frequent disconnects, degraded service, no connection registration

Interesting! I reviewed the post after I submitted it and they were visible for a while, must have been locked down later.

 

Modem Status

Current Reading (behind splitter)

Earlier reading (before splitter)

 

 

Expert

Re: Frequent disconnects, degraded service, no connection registration

Do you need that splitter ? Because it's making your upstream power go too high.



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Frequent Visitor

Re: Frequent disconnects, degraded service, no connection registration

I do need a splitter, a different one might be better. Without the splitter however, the experience is the exact same right now and speeds were around what they should be for over 2 years before yesterday. Straightening out some cable has reduced my upstream power from 52dB to 50dB. Swapping out a particularly ratty looking cable reduced it to 44dB. Here is an updated snapshot of the signals.

2_24.JPG

Expert

Re: Frequent disconnects, degraded service, no connection registration

Can't see your latest pic.



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Frequent Visitor

Re: Frequent disconnects, degraded service, no connection registration

All images still show for me in this post, I guess I'll stop using the photos option here though.

 

February 24th, 2019

Frequent Visitor

Re: Frequent disconnects, degraded service, no connection registration

I have observed that my upload speed is consistently around 0.9-1.0Mbps at all times vs the 6.0 that I believe it should be. I have seen however that my download speeds seem to vary with the time of day, 20Mbps or so during the day, 15Mbps in the evening, and in the very early AM up around 30Mbps. I haven't noticed my connection drop in about 2 days, I'm not sure if seeing the signal stats over a longer duration (unerrored/correctable/uncorrectable codewords) will be helpful, but here is an updated snapshot of my signal down the full length of my cable:

2-26-19_Residence Cable Modem Signal

 

Upon a fresh reboot, there are a few other error messages aside from the repeating "T3 time out" and "T4 time out" mentioning CM and TCS, here is a snapshot of that:

2-26-19_Residence Error Log

 

In an attempt to rule out the interior cabling, I connected the modem to a point about 3 feet into the basement, as close to the exterior connection as possible.

2-26-19_Direct Connection

I can't use that point for day-to-day, I just temporarily cut the modem in there for debug purposes. The behavior is the same, only 1 locked channel and partial internet speeds with the same error messages.

 

This leads me to think that the issue must either be with the modem, or external from the house (house to pole, or more widespread Comcast issue). I'm no expert with reading the signal levels but it seems like the signal in my residence looks pretty good? Is there anything concerning at all about the most "direct" connection having such a low upstream power level? Anything that could help rule out or condemn the modem would be helpful!

 

Diamond Problem Solver

Re: Frequent disconnects, degraded service, no connection registration

@caldoer
Have you thought maybe it’s time to upgrade your equipment to something more recent?

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Expert

Re: Frequent disconnects, degraded service, no connection registration

I agree. Even though that may not be the root cause of the problem, you should upgrade that modem to one that offers more downstream channels. There would be more redundancy that way.

 

This one has a rock solid reputation, and the price is right !;

 

https://www.amazon.com/ARRIS-SURFboard-SB6183-Docsis-Packaging/dp/B00MA5U1FW

 

The upstream power is NOT "too low" in your latest pic, it is within specs.

 

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) 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 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 !



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Official Employee

Re: Frequent disconnects, degraded service, no connection registration

 

caldoer, EG suggested, I believe there is an issue with how your modem is communicating (or not, in this case) with the CMTS. Let's take a closer look at those timeouts and signal levels. Please send me a private message with your full name for further assistance. 

 

KenF


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Frequent Visitor

Re: Frequent disconnects, degraded service, no connection registration

I picked up a NETGEAR CM500 to test, as mentioned might as well go for the extra channels even if it wasn't the issue. I get a cable signal and can do a speedtest, but unfortunately can't actually browse the internet. It seems like Comcast was only able to partially register it, on the phone they indicated that it wasn't connected at all... Definitely looking like an external connection problem now. The signal seems to indicate better SnR but just like my ARRIS is only able to lock a single upstream channel. The download speed is also about 50% of what I see on the ARRIS- upload being the same.

NETGEAR CM500

 

I'm back on the ARRIS for now, based on everything maybe it is a miracle I have an internet connection at all right now. I have been in communication with ComcastAndrew who has been very helpful and it seems like having a tech over is all that is left to do.

Official Employee

Re: Frequent disconnects, degraded service, no connection registration

I picked up a NETGEAR CM500 to test, as mentioned might as well go for the extra channels even if it wasn't the issue. I get a cable signal and can do a speedtest, but unfortunately can't actually browse the internet. It seems like Comcast was only able to partially register it, on the phone they indicated that it wasn't connected at all... Definitely looking like an external connection problem now. The signal seems to indicate better SnR but just like my ARRIS is only able to lock a single upstream channel. The download speed is also about 50% of what I see on the ARRIS- upload being the same.

NETGEAR CM500

 

I'm back on the ARRIS for now, based on everything maybe it is a miracle I have an internet connection at all right now. I have been in communication with ComcastAndrew who has been very helpful and it seems like having a tech over is all that is left to do.

Your CM500 never registered on the back end so that's why you were told it wasn't connected at all. There is literally no trace of it. If you'd like to activate it again, we can try that and I'll make sure it's provisioned properly on my end. 

 

Definitely agree that we need to send a truck especially since there are reports of inside ingress which might be the culprit of all of our issues.

 

KenF


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Re: Frequent disconnects, degraded service, no connection registration

The tech came by and cut/replaced the coax connectors throughout the basement as well as in the box outside (several there, 4 room apt). Spent some time on the pole and then confirmed there was no longer a noise/ingress issue. Even picked up the cablebox I hadn't yet returned for the service I dropped previously.

 

I was still seeing lower speeds but no errors in the modem logs and full upstream locks- turned out to be something I'd tweaked with my router trying to figure out what was going on earlier. Reverted the router and everything is back to normal and better than it was before my problems began! Now I just need to swap out the 4x4 modem for the 16x4.

 

Big thanks to EG and KenF for the assistance.

Official Employee

Re: Frequent disconnects, degraded service, no connection registration

caldoer, awesome glad to hear the tech appointment went well and you're seeing improvement. Thanks for being a customer!


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Expert

Re: Frequent disconnects, degraded service, no connection registration


@caldoer wrote:

 

Big thanks to EG and KenF for the assistance.


Quite welcome ! It's why we lurk !  Smiley Happy



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