Bootstrapping WebSockets with HTTP/3

The mechanism for running the WebSocket Protocol over a single stream of an HTTP/2 connection is equally applicable to HTTP/3, but the HTTP version-specific details need to be specified. This document describes how the mechanism is adapted for HTTP/3.¶

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[RFC8441] defines an extension to HTTP/2 which is also useful in HTTP/3. This extension makes use of an HTTP/2 setting. Appendix A.3 of [HTTP3] describes the required updates for HTTP/2 settings to be used with HTTP/3.¶

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here.¶

[RFC8441] defines a mechanism for running the WebSocket Protocol [RFC6455] over a single stream of an HTTP/2 connection. It defines an Extended CONNECT method which specifies a new ":protocol" pseudo header field and new semantics for the ":path" and ":authority" pseudo header fields. It also defines a new HTTP/2 setting sent by a server to allow the client to use Extended CONNECT.¶

The HTTP/3 stream closure is also analogous to the TCP connection closure of [RFC6455]. Orderly TCP-level closures are represented as a FIN bit on the stream (Section 4.2 of [HTTP3]). RST exceptions are represented with an stream error (Section 8 of [HTTP3]) of type H3_REQUEST_CANCELLED (Section 8.1 of [HTTP3]).¶

The semantics of the headers and setting are identical to those in HTTP/2 as defined [RFC8441]. Appendix A.3 of [HTTP3] requires that HTTP/3 settings be registered separately for HTTP/3. The SETTINGS_ENABLE_CONNECT_PROTOCOL value is 0x08 (decimal 8), as in HTTP/2.¶

If a server which advertises support for Extended CONNECT but receives an Extended CONNECT request with a ":protocol" value that is unknown or is not supported, the server SHOULD respond to the request with a 501 (Not Implemented) status code (Section 15.6.2 of [HTTP]). A server MAY provide more information via a Problem Details response [RFC7807].¶

This document introduces no new security considerations beyond those discussed in [RFC8441].¶

This document registers a new setting in the "HTTP/3 Settings" registry ([HTTP3]).¶

TODO acknowledge.¶