Value,Description,Expected Version Tokens,Reference
HTTP,Hypertext Transfer Protocol,"any DIGIT.DIGIT (e.g., ""2.0"")","[RFC9110, Section 2.5]"
TLS,Transport Layer Security,"ANY DIGIT.DIGIT (e.g., ""1.2"")",[RFC2817]
WebSocket,The Web Socket Protocol,,[RFC6455]
websocket,The Web Socket Protocol,,[RFC6455][RFC8441]
h2c,Hypertext Transfer Protocol version 2 (HTTP/2) (OBSOLETE),,"[RFC9113, Section 3.1]"
connect-udp,Proxying of UDP Payloads,,[RFC9298]
connect-ip,Proxying of IP Payloads,,[RFC9484]