[yangl1996]

There are also the "middle boxes" that networking researchers talk a lot about. Such devices sit in the middle of a link and easily become unhappy if the packets transmitted do not fit some (possibly outdated or buggy) predefined scheme. Think of cooperate firewalls with "deep pack inspection" that intelligently shut down connections they do not like. Once all middle box vendors start to assume a certain way that a protocol (say, TCP) should behave, it's impossible to change the protocol because it will break the middle boxes.

Encrypting QUIC datagrams prevents middle box vendors from assuming anything about QUIC (at least the encrypted part), so that QUIC can change if there's a need in the future without worrying about supporting legacy middle boxes. Although I do agree using UDP does not allow QUIC to break out from any ossification in UDP itself.

[randomifcpfan]

Yes, exactly. See this lwn article for more discussion of ossification: https://lwn.net/Articles/745590/

[BlueTemplar]

> SCTP has been around for years, but middleboxes still do not recognize it and tend to block it. As a result, SCTP cannot be reliably used on the net. Actually deploying a new IP-based protocol, he said, is simply impossible on today's Internet.

Well, IPv6 shows that it's hard, but possible.

Also see how new broadcast "protocols" were forced on TV manufacturers by various governments worldwide.

[unethical_ban]

Most enterprise security vendors at the moment are advising their customers to block QUIC at the perimeter to force fallback to HTTPS so their TLS decryption can function.

There are valid, ethical reasons for an organization to want to see unencrypted network traffic at their perimeter, and until that problem is solved, you better not go QUIC-only if you are in the business to make money.