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I thought it was bad enough how comcast will use your bandwidth you pay for to support their xfinity network.
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Also, Comcast bandwidth consumption by others does not count against your bill.
While it may not directly affect the bill, but it costs in other ways. The coaxis cable that came into your house can carry only so much, and you do pay for the electricity that powers the modem and such.
All three consumer-class ISP's (Optima, Fios, and Comcast/xfinity) in my area pushes their one-box solution: that one box does cable-modem, firewall/router, and WiFi AP (access point). You no longer directly control these. You go into their website to modify your WiFi AP and or your router settings.
If you use those one-box solution they are pushing... In Optima's case, they use a lone UBEE box doing DOCSIS 3.1, firewall, router, and WiFi. Following the UBEE user manual (from the UBEE site), I can ping the box, but the device displays an error when I tried to http into it. I know that IP is right since I can ping it, but I can't http into it. The optima-provided UBEE has the local web setup pages locked out. You must use Optima's site to get to your account page where you can edit some settings in the UBEE box. For router - only port forwarding and nothing else I could find. You can't do much with your WiFi AP either beyond changing the SSID and WAP password. The cable-ISP company has control all the way down to and including your WiFi AP. To add insult to injury, they also sell a "WiFi management service" you can add to your plan (at least comcast/xfinity do, not sure about Optima).
All three consumer-ISPs in my area (Fios, Optima, Xfinity/Comcast) has "nation wide WiFi" service you can add to your plan - to access WiFi everywhere they have a presence. You may well be logging onto a UBEE box / Verizon-G3100 like device in someone's business location or home. The owner/renter of the UBEE box pays a rental fee and pays the electricity to power that box while merely just getting just a virtual AP in his/her home. Other "nation wide WiFi" user
may well be logged into another virtual AP that is in that same box. I don't know if the ISP actually would go that far to have you fund their service, but what they deployed certainly can go that far.
I know in theory those boxes can go as high as 2.5Gb/s. Many older buildings has RG59 instead of RG6, possibly with a splitter or two already before getting into your location. 2.5Gb/s would be pushing the luck. What if the box is in your house/business while the dozen people in the coffee shop next door all happen to logon using their "nation wide WiFi" also from your cable company?
I am not a generous person when it comes to bandwidth and electrical bill. I use xFinity/comcast, with my own cable modem into my own firewall/router with my own WiFi AP. So I know at least the cable that comes into my house carry only my traffic - as long as I stay away from the "Amazon Sidewalk" types of things.