[zare_st]

But the stuff that carries TCP is IP. That's why TCP can work seamlessly, because it uses identification from a previous layer. Consider I bind a server to an ID, and not IP:port, the operating system running it must know how to communicate that via IP, so there will be a corellation map somewhere and that map needs to be synchronized between all peers that wish to host the roaming server.

Otherwise you're just switching port (16-bit) value to arbitrary 32-bit identifier.

[mlyle]

If TCP didn't use L3 source and destination addresses to distinguish connections, it could be more easily taught to deal with:

* Clients roaming between L3 addresses

* Clients/servers with multiple L3 addresses

[alexey-salmin]

But... it doesn't? TCP has no notion of IP address in the protocol, only the port. TCP with changing IPs can work e.g. on top of an ip-ip tunnel with applications not being aware at all.

[EvanAnderson]

The protocol would have to handle binding the network to the transport. MPTCP and SCTP both handle that via registering and un-register network layer endpoints. This parallel universe TCP would be the same in that regard.

(I did say I was oversimplifying...