Contributor
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19 Messages
Very bad latency and packet loss to Comcast CMTS Gateway (wired directly)
As the title states, I have been having very bad issues with latency and packet loss to my comcast gateway at the CMTS. I have connected directly to my router and also directly to my modem via cat6 to eliminate those as issues. I have replaced (now TWICE) my cable modem with approved comcast devices. I have had technicians come to my house (now FOUR times) and they have FULLY replaced all wiring from the POLE to my modem. I am ONLY using 1 modem, zero other devices (no tv, phone, etc). There are no splitters involved. Every wires is brand new and installed by comcast technician from the utility pole to my modem. This is pure RG6 quad shielded with zero splitters in the mix.
This has been going on for nearly 2 months now, and I'm at wits end. I have called support nearly 10 times, and they are completely and utterly useless. They keep trying to send more technicians, who come and then tell me to 'never have them send another technician, all your cables are brand new and test fine, the issue likely lies at the headend or CMTS."
This image is a typical day for me. Pings directly to my Comcast gateway at the CMTS will spike to 500ms or higher, and packet loss hovers in the 5-10% range. This is a single hop from my router, which shows ZERO packet loss and and avg latency of 3ms. I also have my modem disconnect and need a power cycle multiple times a week. This happens on ALL of my 3 modems (one older Motorola and 2 brand new devices - one Netgear and the other Arris).
Please see the linked image as evidence of this. This makes things like gaming, working, video chat and simple streaming from netflix/youtube nearly impossible. This issue occurs at all hours of the day.
Any help would be GREATLY appreciated as I am stuck with Comcast (no other service in my area). When it works, it works fine - up to 2 months ago I had zero issues and nothing changed at my location.
Tech support is very useless and often runs a single "your modem is online" test and then asks me to perform a speed test, which works fine. Speed tests do NOT count for latency or packet loss, they simply try to get as fast as possible and that typically shows 800-900Mbps on my 1Gb plan. My issue is EXTENSIVE latency and packet loss which makes actual usage very hard to live with.
Thank you very much for reading this and please, please dear god, help me 🙂
verywhitenoise
Contributor
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19 Messages
4 years ago
Even as I typed this message, my connection went to pot again. Completely unreliable.
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verywhitenoise
Contributor
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19 Messages
4 years ago
From my Netgear:
Help Center
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verywhitenoise
Contributor
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19 Messages
4 years ago
Another day - more insanely high packet loss: 15% avg with an average ping of 77 to my first hop gateway in comcasts network.
https://imgur.com/a/Be7ppHZ
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EG
Expert
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110K Messages
4 years ago
The downstream power is very high / out of spec. Is there a drop amplifier on the coax line that leads to the modem ? If so, try bypassing it and see.
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verywhitenoise
Contributor
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19 Messages
4 years ago
Thanks EG. There is nothing between the runs, just a barrel connector and it has no dB markings on it. This is all 100% fresh cable that a technician just ran, from pole to modem, including all connectors and cables. No splitters, etc.
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Jlavaseur
Problem Solver
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948 Messages
4 years ago
Just a thought, check and see if your modem/gateway has the puma 6 chipset, it has issues with latency
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EG
Expert
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110K Messages
4 years ago
What is the exact model number of your Netgear modem ?
The downstream power should be addressed regardless of anything else. It may be saturating / overdriving the front-end receiver of the modem which can cause packet loss / waveform distortion.
Perhaps it would be best to get a tech out to properly balance the line. Good luck !
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verywhitenoise
Contributor
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19 Messages
4 years ago
@EG Thank you for the information. It's the CM1000, and I also have an Arris SB8200 that I bought to rule out the modem itself. Is reducing the downstream power as simple as buying an attenuator and plopping it inline? As I said, I've had 5 technicians out and not a single one of them identified this issue. I have lost nearly all faith in the guys they send out.
Now that you've pointed me to a problem, I'll work on getting that sorted and report back if there is any improvement. Thank you again, I really appreciate the help!
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EG
Expert
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110K Messages
4 years ago
As a P.S. Please be advised that this may or may not be the root cause of the problem (YMMV). But it should be addressed regardless. This problem can also be being caused by a local cable segment / node traffic capacity / congestion problem.
Good luck with it !
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EG
Expert
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110K Messages
4 years ago
For that large amount of reduction needed, you would have to use a Forward Path Only attenuator so that it only knocks down the downstream power without affecting the upstream power, which happens to be good / in spec. If you used a 10 dB (or more) overall signal attenuator pad it would push the upstream power higher to out of spec levels and cause the very problems that you are trying to cure.
In regards to overall line attenuation, the upstream and the downstream power levels work in equal but opposite ways. It makes the downstream power go lower while it simultaneously makes the upstream power go higher.
You could try using two of these coupled together for a total of 12 dB downstream power reduction;
https://www.amazon.com/line-Signal-Forward-Attenuator-FPA6-54/dp/B07882H96R
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Highpingity
New Poster
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1 Message
4 years ago
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CCChe
Official Employee
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6.9K Messages
4 years ago
Hi @verywhitenoise! I hope all is well. I just wanted to check in with you to see if you've had any luck with the suggestions that our awesome expert @EG provided?
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CCChe
Official Employee
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6.9K Messages
4 years ago
Hi @Highpingity! Thank you for sharing your experience here on the Xfinity Forum! I'm sorry for the issues you're having as I know how important it is to have reliable services. I wanted to see if there is anyway me and my team can help. I want to review your account, your premise signal levels and check your local node to see if I can find a culprit. Can you send a private message with your first and last name and the numbers associated with your address? To send a message, click on my name, "ComcastChe," then click send a message.
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