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ART HTTP Internet-Draft This specification introduces a way to advertise the support for the extended CONNECT feature that is used for running the WebSocket protocol over a single stream of an HTTP/2 and HTTP/3 connection using HTTPS resource records . RFC EDITOR: please remove this section before publication Discussion of this draft takes place on the HTTP working group mailing list (ietf-http-wg@w3.org), which is archived at https://lists.w3.org/Archives/Public/ietf-http-wg/. Working Group information can be found at https://httpwg.org/; source code and issues list for this draft can be found at https://github.com/httpwg/http-extensions/labels/h3-websockets.

Introduction The mechanisms for running the WebSocket protocol over a single stream of an HTTP/2 and HTTP/3 connection are defined in and . For bootstrapping WebSockets from HTTP/2 and HTTP/3 extended CONNECT is used. Support for the extended CONNECT is advertised using HTTP/2 and HTTP/3 settings (see and ). Therefore, clients need to establish a HTTP/2 or HTTP/3 connection and wait for the setting frames to be exchanged to discover whether the connection can be used for the WebSocket requests. This specification adds a way to advertise the support for the extended CONNECT using HTTPS resource record which will eliminate the need for a HTTP/2 or HTTP/3 connection and introduce delays. The clients can skip trying a HTTP/2 or HTTP/3 connection if the support for the extended CONNECT is not advertised.

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 when, and only when, they appear in all capitals, as shown here.

Extending HTTPS DNS resource record This specification introduces the "extended-connect" SvcParamKey (see ) that indicates that a particular service endpoint supports the extended CONNECT feature defined in and . The presentation and wire format values for the "extended-connect" SvcParamKey MUST be empty. If the "extended-connect" key is present, "alpn" MUST also be specified with at least the h2 or h3 value.

The Client Behavior Upon receiving a HTTPS RR, a client should use the "extended-connect" SvcParamKey as an indication whether a particular service endpoint supports the extended CONNECT feature. If the key is not present the client should not try using QUIC or TCP with the alpn set to h2 for requests that need the feature, e.g. WebSocket, and should directly use HTTP/1.1. If the key is present, that is a strong indication that the service endpoint supports the feature and the client should attempt using HTTP/2 or HTTP/3 protocol. Due to difficulties of deployments the client may discover that the feature, although advertised, is not supported and in this case the client should fallback to using HTTP/1.1.

Security Considerations This specification only adds a hint of whether a feature is supported or not and therefore, it does not introduce additional security considerations beyond one described in and .

IANA Considerations This specification adds the following entry to the Service Parameter Keys (SvcParamKeys) registry: Number Name Meaning Format Reference 7 extended-connect Support of the extended CONNECT feature (This document) Section 3

Google The mechanism for running the WebSocket Protocol over a single stream of an HTTP/2 connection is equally applicable to HTTP/3, but needs to be separately registered. This document describes the mechanism for HTTP/3. Google Akamai Technologies Akamai Technologies This document specifies the "SVCB" and "HTTPS" DNS resource record (RR) types to facilitate the lookup of information needed to make connections to network services, such as for HTTP origins. SVCB records allow a service to be provided from multiple alternative endpoints, each with associated parameters (such as transport protocol configuration and keys for encrypting the TLS ClientHello). They also enable aliasing of apex domains, which is not possible with CNAME. The HTTPS RR is a variation of SVCB for use with HTTP [HTTP]. By providing more information to the client before it attempts to establish a connection, these records offer potential benefits to both performance and privacy. TO BE REMOVED: This document is being collaborated on in Github at: https://github.com/MikeBishop/dns-alt-svc (https://github.com/MikeBishop/dns-alt-svc). The most recent working version of the document, open issues, etc. should all be available there. The authors (gratefully) accept pull requests. Akamai The QUIC transport protocol has several features that are desirable in a transport for HTTP, such as stream multiplexing, per-stream flow control, and low-latency connection establishment. This document describes a mapping of HTTP semantics over QUIC. This document also identifies HTTP/2 features that are subsumed by QUIC, and describes how HTTP/2 extensions can be ported to HTTP/3. DO NOT DEPLOY THIS VERSION OF HTTP DO NOT DEPLOY THIS VERSION OF HTTP/3 UNTIL IT IS IN AN RFC. This version is still a work in progress. For trial deployments, please use earlier versions. Note to Readers Discussion of this draft takes place on the QUIC working group mailing list (quic@ietf.org), which is archived at https://mailarchive.ietf.org/arch/search/?email_list=quic. Working Group information can be found at https://github.com/quicwg; source code and issues list for this draft can be found at https://github.com/quicwg/base-drafts/labels/-http. This document defines a mechanism for running the WebSocket Protocol (RFC 6455) over a single stream of an HTTP/2 connection. This specification describes an optimized expression of the semantics of the Hypertext Transfer Protocol (HTTP), referred to as HTTP version 2 (HTTP/2). HTTP/2 enables a more efficient use of network resources and a reduced perception of latency by introducing header field compression and allowing multiple concurrent exchanges on the same connection. It also introduces unsolicited push of representations from servers to clients.This specification is an alternative to, but does not obsolete, the HTTP/1.1 message syntax. HTTP's existing semantics remain unchanged. In many standards track documents several words are used to signify the requirements in the specification. These words are often capitalized. This document defines these words as they should be interpreted in IETF documents. This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. RFC 2119 specifies common key words that may be used in protocol specifications. This document aims to reduce the ambiguity by clarifying that only UPPERCASE usage of the key words have the defined special meanings.

Acknowledgments