Internet-Draft SETTINGS_ENABLE_WEBSOCKETS January 2023
Yamamoto Expires 11 July 2023 [Page]
8441, 9220 (if approved)
Intended Status:
Standards Track
山本 桃歌 (M. Yamamoto)
The University of Tokyo/WIDE Project

SETTINGS_ENABLE_WEBSOCKETS settings parameter for HTTP/2 and HTTP/3


This document proposes a new HTTP settings parameter, SETTINGS_ENABLE_WEBSOCKETS. This parameter indicates whether the server supports bootstrapping WebSockets over the established connection.

Discussion Venues

This note is to be removed before publishing as an RFC.

Discussion of this document takes place on the HTTP Working Group mailing list (, which is archived at

Source for this draft and an issue tracker can be found at

Status of This Memo

This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79.

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This Internet-Draft will expire on 11 July 2023.

Table of Contents

1. Introduction

The mechanisms for running the WebSocket protocol [RFC6455] over a single stream of an HTTP/2 and HTTP/3 connection is defined in [RFC8441] and [RFC9220]. The extended CONNECT mechanism is used for bootstrapping WebSockets from HTTP/2 and HTTP/3. Support for the extended CONNECT mechanism is advertised using HTTP/2 and HTTP/3 settings parameter SETTINGS_ENABLE_CONNECT_PROTOCOL.

However, the support of extended CONNECT does not necessarily indicate support for WebSockets over that HTTP connection. Other protocols such as [WEBTRANSPORT] also use extended CONNECT and send SETTINGS_ENABLE_CONNECT_PROTOCOL settings parameters as well.

Suppose the server supports extended CONNECT but not bootstrapping WebSockets over that HTTP connection. In this case, the client sending a WebSocket handshake request will result in a response of 501 (Not Implemented) status code (Section 15.6.2 of [HTTP]), and the client would need to fall back to trying the WebSocket handshake over HTTP/1.

This is why a SETTINGS_ENABLE_WEBSOCKETS settings parameter is needed.

2. SETTINGS_ENABLE_WEBSOCKETS settigs parameter for H2 and H3

This document adds a new SETTINGS parameter to those defined by [HTTP/3] Section 11.2.2 and [HTTP/2] Section 11.3.

The new parameter name is SETTINGS_ENABLE_WEBSOCKETS. The value of the parameter MUST be 0 or 1, with 0 being the default.

A sender MUST NOT send a SETTINGS_ENABLE_WEBSOCKETS parameter with the value of 0 after previously sending a value of 1.

If the server supports bootstrapping WebSockets over the HTTP connection, it SHOULD include the SETTINGS_ENABLE_WEBSOCKETS parameter in the SETTINGS frame with a value of 1. If the server does not support bootstrapping WebSockets over the HTTP connection it SHOULD send the parameter with a value of 0.

A client MUST not send this setting parameter. Receipt of this parameter by a server does not have any impact.

The SETTINGS_ENABLE_WEBSOCKETS parameter would allow the client to determine in advance whether the server supports WebSockets over the connection for HTTP/2 or HTTP/3. This allows the client to avoid sending unnecessary WebSocket handshake requests on HTTP connections that do not support WebSockets.

This mechanism will improve compatibility with other extended CONNECT-based protocols.

For compatibility with past implementations which do not use this parameter, clients MAY initiate a WebSocket request without the receipt of this parameter.

3. Security Considerations

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

4. IANA Considerations

4.1. HTTP3

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

Value: TBD


Default: 0

Status: permanent

Specification: This document

Change Controller: IETF

Contact: HTTP Working Group (

4.2. HTTP2

This document registers a new entry in the "HTTP/2 Settings" registry (Section 11.1 of [HTTP/2]).

Code: TBD


Default: 0

Status: permanent

Specification: This document

Change Controller: IETF

Contact: HTTP Working Group (

5. References

5.1. Normative References

Fielding, R., Ed., Nottingham, M., Ed., and J. Reschke, Ed., "HTTP Semantics", RFC 9110, DOI 10.17487/RFC9110, , <>.
Thomson, M., Ed. and C. Benfield, Ed., "HTTP/2", RFC 9113, DOI 10.17487/RFC9113, , <>.
Bishop, M., Ed., "Hypertext Transfer Protocol Version 3 (HTTP/3)", RFC 9114, DOI 10.17487/RFC9114, , <>.
Fette, I. and A. Melnikov, "The WebSocket Protocol", RFC 6455, DOI 10.17487/RFC6455, , <>.
McManus, P., "Bootstrapping WebSockets with HTTP/2", RFC 8441, DOI 10.17487/RFC8441, , <>.
Hamilton, R., "Bootstrapping WebSockets with HTTP/3", RFC 9220, DOI 10.17487/RFC9220, , <>.

5.2. Informative References

Vasiliev, V., "The WebTransport Protocol Framework", Work in Progress, Internet-Draft, draft-ietf-webtrans-overview-04, , <>.


TODO acknowledge people.

Thank you for reading this draft. :)

Author's Address

Momoka Yamamoto
The University of Tokyo/WIDE Project
Additional contact information:
山本 桃歌
The University of Tokyo/WIDE Project