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Slow Upload, but Download unaffected--- Upstream irregularities?

Regular Visitor

Slow Upload, but Download unaffected--- Upstream irregularities?

I have been using the Arris SB8200 for my Gigabit internet plan for 2 months now with no issue. For the purposes of this post, I will be speaking about the speeds from my desktop computer, which is connected via ethernet cable.

Around Aug 14th, my upload speeds have plummeted. To be clear- my plan is 1000 MB down, 35 MB up, so I am aware of the asymmetrical nature of my connection, but my upload now can barely hit 2.0 MB on Google's speed test. This seems accurate because although Ookla and Xfinity's speed tests are saying I am hitting 15 upload, when I try to stream to Twitch with a 4000 KB bitrate, my stream drops nearly all its frames. My download speed is its usual speedy self, consistently sitting at about 800+.


The upload speed issue has not been fixed by taking the following troubleshooting steps:

  • Power cycling the modem
  • Factory reset of the modem
  • Xfinity remote reboot of my modem
  • Booting my PC into Safe Mode with Networking to check for software issues

Finally, I have taken to investigating the modem via accessing its settings thru and have seen a consistent pop up of something called a "Dynamic Range Window Violation" in the SB8200's Event Log [Screenshot of Event Log]. After consulting with Arris' support forum, they informed me that I ideally should have all of my downstream and upstream channels within a certain range for the Power (dBmV). All of my channels fell within the range for my downstream bonded channels[screenshot of downstream], but I noticed that one of my Upstream Bonded Channels was outside of the recommended level of 45+ dBmV [Screenshot of Upstream Bonded Channels].

In closing, is there anything to be done about this without a service visit from a technician? I know due to COVID that Xfinity is refusing to send out technicians for anything short of complete service blackout (which I support), but my entire livelihood is dependent on being able to have a reliable upload speed to communicate with others.

Thank you in advance for any advice provided, I eagerly await any possible solutions to this predicament.

New Poster

Re: Slow Upload, but Download unaffected--- Upstream irregularities?

I am also having this exact same problem, down to the fact that I'm a twitch streamer, have the gig internet, same modem, and same errors on the modem.

New Poster

Re: Slow Upload, but Download unaffected--- Upstream irregularities?

Check your modems firmware. If it is not current try to update it. If it is the latest version then try to load a previous version.