4. The Extended CONNECT Method

[RFC6455] requires the use of Connection and Upgrade header fields that are not part of HTTP/2. They MUST NOT be included in the CONNECT request defined here. [RFC6455] requires the use of a Host header field that is also not part of HTTP/2. The Host information is conveyed as part of the :authority pseudo-header field, which is required on every HTTP/2 transaction. Implementations using this extended CONNECT to bootstrap WebSockets do not do the processing of the Sec-WebSocket-Key and Sec-WebSocket-Accept header fields of [RFC6455] as that functionality has been superseded by the :protocol pseudo-header field.

The :protocol pseudo-header field MUST be included in the CONNECT request, and it MUST have a value of "websocket" (the string "websocket", not the value of the Sec-WebSocket-Protocol header field). The :scheme pseudo-header field MUST be included in the CONNECT request and MUST have a value of "http" or "https".

On requests bearing the :protocol pseudo-header field, the :authority pseudo-header field is interpreted according to Section 8.1.2.3 of [RFC7540] instead of Section 8.3 of that document.