| Internet-Draft | HTTP/3 over QMux | June 2026 |
| Oku, et al. | Expires 28 December 2026 | [Page] |
This document specifies how to use HTTP/3 over QMux.¶
This note is to be removed before publishing as an RFC.¶
Discussion of this document 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/.¶
Source for this draft and an issue tracker can be found at https://github.com/kazuho/draft-kazuho-httpbis-http3-on-streams.¶
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As of 2026, HTTP/2 [HTTP/2] remains the most widely used version of HTTP across the Internet, although the adoption rate of HTTP/3 [HTTP/3] is increasing rapidly.¶
HTTP/3 has several advantages over HTTP/2, primarily due to its use of QUIC [QUIC] as the transport layer protocol, which provides features like stream multiplexing without head-of-line blocking and low-latency connection establishment.¶
However, given that QUIC's availability and accessibility are not as universal as TCP's, a complete migration of all HTTP/2 traffic to QUIC-based HTTP/3 seems unlikely.¶
This situation necessitates HTTP deployments to support both transport protocols and their respective HTTP versions for the foreseeable future.¶
Maintaining dual support is costly, as the two protocols differ in many aspects such as wire-encoding, flow control and stream multiplexing machinery, and HTTP header compression. Extensions operating at the HTTP wire encoding layer must be developed and implemented for both HTTP/2 and HTTP/3, and both protocol stacks require ongoing maintenance to address bugs, performance issues, and vulnerabilities.¶
To address this redundancy, this specification defines the method of running HTTP/3 over QMux version 1 [QMUX], which enables the operation of HTTP/3 over TCP and TLS without any modifications.¶
Consequently, design, implementation, and maintenance efforts can concentrate on a single HTTP version: 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.¶
HTTP/3 functions over QUIC version 1, employing the set of operations (i.e., API) defined in Section 2.4 and Section 5.3 of [QUIC]. HTTP/3 over QMux version 1 utilizes the same set of operations that are available in QMux.¶
HTTP/3 uses QPACK [QPACK] for field compression as described in Section 4.2.1 of [HTTP/3]. QPACK is designed to operate over QUIC version 1, which does not provide guarantees of global ordering across streams. It provides flexibility for implementations to balance resilience against head-of-line blocking and optimal compression ratio (Section 2.1.2 of [QPACK]).¶
QMux version 1 operates on top of a transport layer that guarantees
in-order delivery and guarantees global ordering across streams. When HTTP/3
over QMux is used, QPACK decoders will never be blocked due to packet losses.
To improve compression efficiency, QPACK encoders can reference a dynamic table
entry as soon as the entry is emitted to the underlying transport, regardless of
the SETTINGS_QPACK_BLOCKED_STREAMS value advertised by the peer.¶
HTTP/3 over QMux version 1 can be used for “https” URI schemes defined in Section 4.2 of [HTTP] with the same default port number as HTTP/1.1 [HTTP/1.1].¶
When a client uses HTTP/3 over QMux for an "https" URI scheme, it uses TLS [TLS] with ALPN [ALPN] as described in Section 8 of [QMUX]. The ALPN ID for the final, published RFC is "h3qx". Until such an RFC exists, implementations MUST NOT identify themselves using this string.¶
[[RFC editor: please remove this section before publication.]]¶
This draft describes HTTP/3 over draft version of QMux. In order to support interoperability over revisions, HTTP/3 over QMux drafts define an ALPN ID that captures both this document revision and the QMux revision in use.¶
The ALPN ID defined by this draft revision is "h3qx-01", which represents HTTP/3 over draft-ietf-quic-qmux-01.¶
The security considerations from Section 10 of [HTTP/3] and Section 12 of [QMUX] apply.¶
If this document is adopted and published as an RFC, it will have an action to create a new registration for the identification of HTTP/3 over QMux version 1 in the "TLS Application-Layer Protocol Negotiation (ALPN) Protocol IDs" registry established in [ALPN].¶
TODO acknowledge.¶