Xfinity only allows 35 Mbps upload, but my modem supports 800 Mbps up (plus 2.5 Gbps down). Why is Xfinity artificially capping my speeds?

This would make sense... if the supported modems for 100 Mbps didn't have a fraction of the bandwidth mine does to begin with. They're DOCSIS 3.1, just like mine, and the stuff I see posted elsewhere mentions mid-split is the requirement, and the MB8611's upstream supports a frequency range of 5 to 85 MHz, which covers that split range. There's no technical reason they could possibly have to not negotiate 100 Mbps upload, and their notes about supported modems still only say that the behavior may be different, not that those are the actual hard requirements to get the speeds.

Anyway, that site even says my modem is optimized for the plan I selected, showing that plan is 35 Mbps, which just tells me Xfinity put me on the wrong plan despite what the labels and agent both say. There's some configuration issue on their end, I know it's not a technical or hardware issue.

Just another detail, I have other reasons to think I'm on a plan that isn't the "1 Gig" they promised - mainly that the plan listings show the plan they put me on (showing 35 Mbps), right next to a second plan I could choose to upgrade to also called "1 Gig", with different features supported (including 100 Mbps); and the Broadband Facts labels also have an option for my plan, which has no label at all, and then another tab in the list with a label, for "1 Gig", that shows the specs I expected. So, somewhere in their configuration for me, I know for a fact I have something that is registering as different than the plan I was told I was buying, and it seems that the plan I'm on is not even attempting to use the full upstream frequency my modem supports - because, I'm guessing, it's a legacy plan configuration they assigned me. Which, again, I get that the actual behavior and speeds may be different, but I at least expect that I am allowed the next-gen speeds, and that the connection to Xfinity uses the actual specification of my modem rather than being artificially capped because... who knows why.

@user_dw9rle​ wrote;

I know it's not a technical or hardware issue.

It is a hardware constraint.

https://www.google.com/search?q=does+the+8611+modem+support+mid+split&rlz=1C1CHBF_enUS937US937&oq=does+the+8611+modem+support+mid+split&gs_lcrp=EgZjaHJvbWUyBggAEEUYOTIHCAEQIRigATIHCAIQIRigATIHCAMQIRigATIHCAQQIRigAdIBCjUxODU4ajFqMTWoAgiwAgHxBTXF6Wn-gPb7&sourceid=chrome&source=chrome.rb&ie=UTF-8 

Mid split is literally the ability to reach greater upstream frequencies, i.e., putting the split at 85 MHz, which is supported by the hardware. If you're going to link to Google, where I have AI (that I assume you tried to show me) blocked, how about you share an actual source, please, because this modem supports upstream 85 MHz, which is mid split.

Thanks to both you and @EG for the responses, but I'm still not convinced that there's any real basis for this claim. The link they shared just had a Redditor (one with whom I have problems already) with a couple upvotes saying it's not mid-split, with no documentation to back that up at all - and I have documentation that it does support mid-split.

According to anything I can find, mid-split is literally when the split between upstream and downstream bandwidth spectrums is set at a higher frequency than sub-split, at 85 MHz (https://kb.veexinc.com/en/knowledge/what-is-mid-split-and-high-split-docsis). And the documentation for this modem is, also, showing that it supports upstream at 5 to 85 MHz, switchable from a sub-split configuration (5 to 42 MHz) according to Motorola themselves (https://en-us.support.motorola.com/ci/fattach/get/82899680/1703008337/redirect/1/filename/MB8611-DataSheet-21920.pdf).

So how can it not be mid-split? Looks like a fish, talks like a fish, etc., and I'm shocked that two apparently high-rated experts wouldn't think to actually address the issue with real information rather than a patronizing Google search, to be honest.

Hello, @user_dw9rle happy to check your residence to see if your area network has been enhanced to carry that mid-split signal. That being said the device recommendation list provided by @BruceW are the compatible modems we have tested and know will work on our network vs your MB8611 which may not work at full capacity on our mid-split network. I can also check your current internet plan to see if it allows for higher than 35 Mbps upload.

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