compatible equipment

If you have voice service and want to buy a modem you want a Netgear CM2050V.  It's the only one that supports full DOCSIS 3.1 speeds including DOCSIS 3.1 upload that also supports voice service.  I have one, and I've seen it hit 2200/350 on a 2100/300 plan.  They had some trouble with upload speeds and it took almost 2 years to get it sorted but it's finally fixed and running at full upload speed.  Download was always full speed.  Alternatively you can rent a gateway from Comcast.  The CM2050V is a straight modem (plus a couple RJ-11 plugs for a phone), so you'll need a router if you don't already have one.  Cable TV service is irrelevant.  It's having voice service that's important, as that severely limits your choices.  If you decide to ditch the voice service there are a bunch of other options.  Also much cheaper options.  CM2050V is ~$350.  Hitron Coda56 is $100 and just as fast, but lacks voice support.  So +$250 for voice support.  I got mine several years ago when anything DOCSIS 3.1 was pricey, so the price didn't seem so bad at the time.  You can check other supported models here:  Device Info - Xfinity Compatible Modems I'd get something from the "Compatible Modems for Enhanced Speeds" list.  All the others will be deprecated and kicked off the network sooner as Comcast upgrades their network over time.  Right now DOCSIS 3.0 still works, but they're working on getting rid of it.  That may be why you got that notice.  Arris TM822 is a DOCSIS 3.0 modem.  Either that or they gave you a "free" speed increase and now your plan is faster than your modem can handle.  You might be able to lower your plan, save a few bucks, and keep your gear a bit longer.  Then end is coming though.  They'll boot DOCSIS 3.0 off the network in not too long.  Might still be a few years, but it's coming.