Question why is network file sharing speed limited to around 100mbps

Jun 24, 2022
I have file sharing setup on 2 computers on my network, both are pretty modern and have nvm ssd drives and at least 1gb ethernet. They are both connected to the same 1gig switch with cat6 cables and both get around 600mbps download speeds on the internet.

When reading or writing any file from one pc to another (not over the internet, via LAN) transfer speeds cap at 111mbps or so. Why?

Also where is the bottleneck?

I read on this ( thread that a theoretical expected speed for this situation on a 100mbps system instead of a 1gig system would be around 12.5mbps which would scale to 125mbps in my case which is pretty accurate given some overhead. Why is this the theoretical max transfer speed and upgrading what parts of the system would raise that theoretical cap?