4 Messages
Very slow Internet Download Speeds even after Xfinity repairs in my area
Even after Xfinity completed repairs in my area for performance related issues and even though I worked with Xfinity support, I continue to get extremely slow internet download speeds (about 10-20% of my provisioned speed).
Generally speaking, my upload speed via Speedtest.net have stayed well within my 20 Mbps provisioned speed. My download speed via Speedtest.net, which is provisioned for either 800 or 900 Mbps, dropped very low providing only 10-20% of my provisioned speed.
As I write this post, I continue to see these extremely slow speeds . I'm troubleshot this issue with Xfinity support (Ticket Number: [Edited: "Personal Information"]) and this post is part of that troubleshooting effort, although I encourage anyone with any insights into this problem to offer assistance.
My cable modem is a Netgear CM1000.
Below are extensive details about the issue.
Cable Modem Details
Netgear CM1000
Logs (after rebooting the cable modem)
Note that the logs are captured across two images
[Edited: "Personal Information"]
[Edited: "Personal Information"]
Here are the logs in text format.
2024-12-20, 20:48:43 Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-20, 20:48:42 Notice (6) DS profile assignment change. DS Chan ID: 33; Previous Profile: ; New Profile: 1 2 3 .; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-20, 20:48:41 Notice (6) DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3 .; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"]0;CM-QOS=1.1;CM-VER=3.1
Time Not Established Notice (6) Honoring MDD; IP provisioning mode = IPv6
Time Not Established Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-20, 16:57:49 Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Time Not Established Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-20, 16:56:19 Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Time Not Established Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-20, 16:49:56 Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-20, 16:49:55 Critical (3) No Ranging Response received - T3 time-out; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-20, 16:49:52 Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Time Not Established Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-20, 15:52:02 Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Time Not Established Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-20, 15:50:57 Critical (3) Resetting the cable modem due to docsDevResetNow
2024-12-20, 15:31:06 Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Time Not Established Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-20 15-30-01 Critical (3) Resetting the cable modem due to docsdevResetNow
2024-12-20, 12:57:14 Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Time Not Established Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-19, 12:23:27 Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-19, 12:23:26 Critical (3) No Ranging Response received - T3 time-out; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-19, 12:23:19 Critical (3) UCD invalid or channel unusable; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-19, 12:23:19 Critical (3) SYNC Timing Synchronization failure - Loss of Sync; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-19, 12:22:56 Critical (3) UCD invalid or channel unusable;CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
2024-12-19, 12:18:37 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-19, 12:18:32 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-19, 12:18:32 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-19, 12:18:31 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-19, 12:18:29 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-19, 12:18:28 Critical (3) Received Response to Broadcast Maintenance Request, But no Unicast Maintenance opportunities received - T4 time out; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
2024-12-19, 12:18:26 Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing; CM-MAC=;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1
Connection Information
Note that the connection information is captured across two images
Timeline Details
Yesterday I received a text message at 12:17 pm from Xfinity stating that there were performance issues in my area and work was being done to revolves these issues.
Then, at 1:39 pm, I received a text message from Xfinity stating that the work had been completed.
Performance
Below are graphs showing results for speed tests using Speedtest.net, executed at the command line periodically to monitor my internet performance.
5 Day Performance
2 Day Performance
Detailed Speedtest Results
Here are a few Speedtest.net results from the above graphs with details and links.
12/20/2024 at 8:30 PM
https://www.speedtest.net/result/c/aa5d9da2-3027-4bcd-ade3-fdbc65f41b6e
12/20/2024 at 7:29 PM
https://www.speedtest.net/result/c/aa2bace2-7097-43ce-9d26-16dfa89ee45b
12/20/2024 at 6:30 PM
https://www.speedtest.net/result/c/4139107e-643f-47b2-bdff-843dce7250fa
XfinityJanelle
Official Employee
•
1.5K Messages
4 months ago
Hey @pmb1976 , Thank you for visiting our official Xfinity Forums Community support page. We greatly appreciate you taking the time to share your experience regarding the download speeds. I would be more than happy to offer my assistance looking into this further for you. Are you also hooked up with an external router? Did this just start happening after the maintenance or was it going on before?
2
0
EG
Expert
•
110K Messages
4 months ago
@pmb1976 @XfinityJoe
Please circle back here and post any possible solutions for the issue here in these open public 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.
0
0
pmb1976
4 Messages
4 months ago
Hi,
After a good amount of troubleshooting, my cable modem is now consistently getting 700 Mbps download and 5 Mbps upload. That's a great improvement from before but not the speeds I'm paying for.
In speaking to Xfinity support, I found out that my cable modem (Netgear CM1000) is getting a "default" bootfile rather than the bootfile for my speed tier, namely Superfast which is rated for 800 Mbps download/20 Mbps upload. The Xfinity support representative indicated to me on the phone that that system does *NOT* provide her the ability to select the Superfast speed tier for my Netgear CM1000 and that's likely because the Netgear CM1000 isn't approved for that speed tier.
However, Netgear CM1000 does support the speeds for the Superfast speed tier.
Source: https://www.netgear.com/home/wifi/modems/cm1000/
Additionally, I have had this modem for 5 years and, only until recently, I have been getting well above the 800 Mbps. Here is the last year of speed test results using SpeedTest.net:
Some of the performance issues as of late have, at least in part, been due to wiring issues and outages, etc.
This seems like a possible change in Xfinity's provisioning systems and/or policies with regards to the Netgear CM1000. Can a representative from Xfinity speak to whether the Netgear CM1000 is no longer supported for the Superfast speed tier (rather than this being, say, caused by a technical mistake)?
Thanks,
Paolo
(edited)
0
0
user_0be737
Visitor
•
1 Message
4 months ago
I am experiencing the same issue with the Xfinity CM1100. It worked flawlessly at rates over 300 Mbps for the past few months. Following Xfinity repairs in my neighborhood, my CM1100 can now only get up to 150-170Mbps.
NETGEAR® genie CM1100
Hardware Version 2.02
Firmware Version V10.01.07
Logs:
2024-12-30, 21:50:38 Critical (3) UCD invalid or channel unusable;CM-MAC=X.X.X.X;CM-QOS=1.1;CM-VER=3.1;
2024-12-30, 21:50:38 Notice (6) DS profile assignment change. DS Chan ID: 33; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=X.X.X.x;CMTS-MAC=X.X.X.x;CM-QOS=1.1;CM-VER=3.1;
2024-12-30, 21:50:37 Notice (6) DS profile assignment change. DS Chan ID: 32; Previous Profile: ; New Profile: 1 2 3.;CM-MAC=X.X.X.x;CMTS-MAC=X.X.X.x;CM-QOS=1.1;CM-VER=3.1;
2024-12-30, 21:50:23 Notice (6) Honoring MDD; IP provisioning mode = IPv6
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=X.X.X.X;;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
2024-12-30, 21:34:54 Critical (3) UCD invalid or channel unusable;CM-MAC=X.X.X.X;;CMTS-MA=X.X.X.X;;CM-QOS=1.1;CM-VER=3.1;
2024-12-30, 21:34:33 Critical (3) UCD invalid or channel unusable;CM-MAC=X.X.X.X;;CMTS-MAC=[Edited: "Personal Information"];CM-QOS=1.1;CM-VER=3.1;
Time Not Established Critical (3) SYNC Timing Synchronization failure - Failed to acquire QAM/QPSK symbol timing;CM-MAC=X.X.X.X;;CMTS-MAC=00:00:00:00:00:00;CM-QOS=1.1;CM-VER=3.1;
(edited)
1
0
pmb1976
4 Messages
4 months ago
I decided to purchase an Arris S34 in order to resolve my speed issues. It's part of the "next gen" devices. If you are willing to speed $200 and have the money, I think it's a good way to future proof your cable modem investment for as long as possible. The Arris S34 came out just 2-3 months ago and is considered a "Next Gen" device, which I believe means it supports the faster upload speeds Comc ast is now offering. I can confirm that I'm getting 120 Mbps now (rather than 20 Mbps) which is actually pretty useful in my case as I back up to a remote server.
I've had my Netgear CM1000 for close to 5 years and it's paid for itself many times over so I can't complain too much about the situation. It's a shame, though, that Xfinity seems to "discontinue" seemingly good modems (assuming that's what actually happened). But then again I imagine that supporting firmware deployments to older customer owned equipment costs money.
Paolo
1
0