[mdasen]

I think the issue is that the bandwidth is shared. One of the things Xfinity is working on is moving to mid/high-split DOCSIS 3.1 which increases uplink speeds by allocating a larger frequency range to uploads. Even with mid or high-split DOCSIS 3.1, you're still sharing 450Mbps or 1.5Gbps with everyone on the same node. Without mid/high-split, you're sharing 108Mbps with everyone on your node. Another part of the network upgrade is splitting nodes and bringing fiber closer to the customer. If a node is serving fewer customers, there's less bandwidth that's shared.

The max speeds of the standard aren't really things that they can give you. Theoretically, LTE networks can give you 5Gbps, but the real-world experience is different given a shared link and signal loss/interference.

As I noted, Xfinity is updating their network to mid/high-split DOCSIS 3.1 and they're going to be increasing upload speeds to 75-200Mbps depending on your plan. They're already offering 1.2Gbps download speeds in my market. They're also supposed to start trials of DOCSIS 4 later this year.

I don't say this because Xfinity is a good company or anything, but you can't just look at the max speeds of a standard.

[zokier]

Notably also PON networks, the predominant last-mile fiber tech, is also shared medium with splits afaik going as high as 1:128. So for example classic GPON/EPON with nominal 1Gbps capacity can mean possibly only <10Mbps per-subscriber bandwidth allocation.

[icedchai]

You are right, but with DOCSIS, you're generally sharing an order-of-magnitude smaller bandwidth allocation with many more users. Around here, there's 4 upstream channels available (roughly 120 megabits) shared across at least 200 homes.

Downstream is better, but it's still around a gigabit shared (32 DOCSIS channels.) Then you need to consider the RF issues that constantly plague cable networks, like ingress. Based on my personal experience, it can take months to get this fixed, if they'll even believe it's a problem. They'll open ticket for "outside plant" and not fix anything. At one point, I saw my upstream drop below a megabit! (And no, it wasn't my wiring or equipment.)

I recently switched to fiber, and it's night-and-day.

[xattt]

DOCSIS also carries unavoidable latency overhead in conversion to RF and back. This adds up.