Doesn't HTTP3 solve this with QUIC?
- Bandwidth sharing (“fair” scheduling) - Sender-driven congestion control
See: https://arxiv.org/pdf/2210.00714.pdf (pdf download)
1) It's not TCP
2) It's a PITA on a 'trusted' network because there is not "encryption off" mode
For internal datacentre traffic, it depends on the value of the data. But you will need to do application level encryption.
For links between datacentres, encrypting links based on rules is a sensible and not horrifically challenging thing to do. If you're big enough to have to worry about the volume of encrypted traffic, then you have rules based bandwidth priorities.
for virtually everyone else, just use wireguard or some other VPN with encryption.