HTTP Working GroupR. Hamilton
Intended status: Standards TrackJanuary 12, 2022
Expires: July 16, 2022

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.

About This Document

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1. Introduction

[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.

2. Conventions and Definitions

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.

3. Websockets Upgrade over HTTP/3

[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 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].

4. Security Considerations

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

5. IANA Considerations

This document registers a new setting in the "HTTP/3 Settings" registry (Section 11.2.2 of [HTTP3]).

Setting Name:
This Document
[ date of publication ]
Change Controller:
HTTP Working Group (

6. Normative References

Fielding, R., Nottingham, M., and J. Reschke, “HTTP Semantics”, Internet-Draft draft-ietf-httpbis-semantics-19 (work in progress), September 2021.
Bishop, M., “Hypertext Transfer Protocol Version 3 (HTTP/3)”, Internet-Draft draft-ietf-quic-http-34 (work in progress), February 2021.
Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels”, BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, <>.
Fette, I. and A. Melnikov, “The WebSocket Protocol”, RFC 6455, DOI 10.17487/RFC6455, December 2011, <>.
Nottingham, M. and E. Wilde, “Problem Details for HTTP APIs”, RFC 7807, DOI 10.17487/RFC7807, March 2016, <>.
Leiba, B., “Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words”, BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, <>.
McManus, P., “Bootstrapping WebSockets with HTTP/2”, RFC 8441, DOI 10.17487/RFC8441, September 2018, <>.


TODO acknowledge.

Author's Address

Ryan Hamilton