So in networking class they taught us the OSI model, TCP, CDMA, congestion, frames, etc.

What I would like to know if standards that have been around for 20-30 years like TCP, are burnt into today’s hardware, or can someone come up with say TCPX, write the code, deploy it to two machines on the network and use that protocol for communication? Since this doesn’t affect how to find someone on the network, I assume it’s not an issue on generic hardware.

But say a custom IP protocol was developed. Would incompatible network hardware drop those packets since it can’t understand where it needs to be sent?

What I’m trying to figure out is how low (or high? never understood the model orientation) can someone go on the stack with custom implementations before the network between them can no longer transmit data.