Internet DRAFT - draft-duke-httpbis-quic-version-alt-svc
draft-duke-httpbis-quic-version-alt-svc
HTTP M. Duke
Internet-Draft Google
Intended status: Standards Track L. Pardue
Expires: 23 October 2023 Cloudflare
21 April 2023
An Alt-Svc Parameter and SvcParamKey for QUIC Versions
draft-duke-httpbis-quic-version-alt-svc-03
Abstract
HTTP Alternative Services (Alt-Svc) describes how one origin's
resource can be accessed via a different protocol/host/port
combination. Alternatives are advertised by servers using the Alt-
Svc header field or the ALTSVC frame. This includes a protocol name,
which reuses Application Layer Protocol Negotiation (ALPN)
codepoints. The "h3" codepoint indicates the availability of HTTP/3.
A client that uses such an alternative first makes a QUIC connection.
However, without a priori knowledge of which QUIC version to use,
clients might incur a round-trip latency penalty to complete QUIC
version negotiation, or forfeit desirable properties of a QUIC
version. This document specifies a new Alt-Svc parameter that
specifies alternative supported QUIC versions, which substantially
reduces the chance of this penalty.
Similarly, clients can retrieve additional instructions about access
to services or resources via DNS SVCB and HTTP Resource Records.
This document also defines a new SvcParamKey for these Resource
Records, which specifies the specific QUIC versions in use.
About This Document
This note is to be removed before publishing as an RFC.
The latest revision of this draft can be found at
https://martinduke.github.io/quic-version-alt-svc-parameter/draft-
duke-httpbis-quic-version-alt-svc.html. Status information for this
document may be found at https://datatracker.ietf.org/doc/draft-duke-
httpbis-quic-version-alt-svc/.
Discussion of this document takes place on the HTTP Working Group
mailing list (mailto: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/martinduke/quic-version-alt-svc-parameter.
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Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
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Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 23 October 2023.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions and Definitions . . . . . . . . . . . . . . . . . 4
3. The quicv Parameter . . . . . . . . . . . . . . . . . . . . . 4
4. The quicv SvcParamKey . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 6
References . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
Normative References . . . . . . . . . . . . . . . . . . . . . 6
Informative References . . . . . . . . . . . . . . . . . . . . 6
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 7
A.1. since draft-duke-httpbis-quic-version-alt-svc-01 . . . . 7
A.2. since draft-duke-httpbis-quic-version-alt-svc-00 . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
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1. Introduction
HTTP Alternative Services (Alt-Svc) [ALTSVC] describes how one
origin's resource can be accessed via a different protocol/host/port
combination. Alternatives are advertised by servers using the Alt-
Svc header field or the ALTSVC frame. This includes a protocol name,
which reuses codepoints from the Application-Layer Protocol
Negotiation (ALPN) TLS extension [RFC7301]. Servers can advertise
multiple alternatives, in which case the order reflects the server's
preferences (the first value being the most preferred).
Clients can ignore alternative services, or pick one at their
discretion. A client might use any details from the advertisement,
in addition to out of band information, in determining if an
alternative is suitable or preferred.
While ALPN was originally intend to allow multiple applications to
utilize TLS or DTLS on the same IP address and TCP or UDP port, ALPN
can also usefully identify the transport in an Alt-Svc context. The
"h3" ALPN codepoint informs the client that it can use HTTP/3
[RFC9114] for access, which in turn requires the QUIC transport
protocol [RFC8999].
QUIC is versioned. A client and server that both support a QUIC
version can, through a negotiation process, generally agree on that
version in no more than one round-trip. However, to avoid that
penalty clients might use the most commonly deployed QUIC version
(e.g. version 1 [RFC9000] at the time of writing), rather than the
version with the most desirable properties for the client's use case.
To avoid the round-trip, one solution would be to register unique
ALPN codepoints for each HTTP/3 and QUIC version combination.
However, this might complicate deployment of new versions and
deprecation of old ones: architecturally, an application should
provide its ALPN to its QUIC implementation. In this case, fully
deploying a new version in that implementation would require updating
all applications that use it.
Instead, this document specifies an Alt-Svc parameter that lists the
QUIC versions available to serve the resource. Clients that do not
understand this parameter will ignore it. They might default to the
most likely version, and/or incur a round-trip penalty in the event
of a mismatch. Clients that do process the parameter will connect
successfully using the most desirable version with high probability.
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Domain Name System (DNS) Service Binding (SVCB) and HTTPS Resource
Records [I-D.ietf-dnsop-svcb-https] allow the distribution of access
instructions beyond the IP address via DNS. This document also
specifies a new SvcParamKey for these Resource Records to distribute
QUIC version information with this technique.
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.
This document uses the Augmented BNF defined in [RFC5234] and imports
parameter from Section 3 of [ALTSVC].
3. The quicv Parameter
This document specifies the "quicv" Alt-Svc parameter, which lists
the QUIC versions supported by an endpoint, using the hexadecimal
representation of the version field in a QUIC long header, as
indicated in [RFC8999]. Senders MAY omit leading zeroes from version
numbers.
quicv = version-list
version-list = DQUOTE version 1*( OWS, "," OWS version-number) DQUOTE
version = 1*8 HEXDIG; hex-encoded QUIC version
Examples:
Alt-Svc: h3=":443"; quicv="1"
Alt-Svc: h3=":443"; quicv="709a50c4,1"
Alt-Svc: h3=":443"; quicv="709a50c4,1", h3=":1001"; quicv="709a50c4"
The order of entries in version-list reflects the server's preference
(with the first value being the most preferred alternative).
Note that the quicv parameter applies to a single associated entry in
the Alt-Svc list. Servers MUST NOT provide a quicv parameter to an
entry containing ALPN codepoint that does not potentially utilize
QUIC.
If the Alt-Svc information resolves to a server pool that
inconsistently supports different QUIC versions, the parameter SHOULD
only advertise versions that are supported throughout the pool.
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4. The quicv SvcParamKey
SVCB and HTTPS Resource Records can include the quicv SvcParamKey.
Its presentation format value and use are identical to the quicv Alt-
Svc Parameter. Its wire format value consists of the version numbers
in network byte order.
To include the quicv SvcParamKey in a resource record, it MUST also
include at least one ALPN that can be delivered over QUIC.
For example, consider a service configuration that advertisees two
QUIC versions on the default port, but only one version on a non-
default port.
In Alt-Svc, this could be represented as:
Alt-Svc: h3=":443"; quicv="709a50c4,1", h3=":1001"; quicv="709a50c4"
As HTTPS RRs, this could be represented as:
example.com IN HTTPS 1 . alpn=h2,h3 quicv=709a50c4,1
example.com IN HTTPS 1 . alpn=h3 port=1001 quicv=709a50c4
5. Security Considerations
This document inherits the security considerations of [ALTSVC],
especially the implications of "Changing Protocols" in Section 9.3.
There are few protocol properties guaranteed to hold across all QUIC
versions, so endpoints should be aware what capabilities are
intrinsic to the QUIC versions they are advertising.
This parameter reveals capabilities of the described server, but this
information is already available by inducing the server to generate a
QUIC version negotiation packet.
6. IANA Considerations
Please add this entry to the HTTP Alt-Svc Parameter Registry:
Alt-Svc Parameter: quicv
Reference: This document
Please add this entry to the Service Binding (SVCB) Parameter
Registry:
Number: TBD
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Name: quicv
Meaning: Supported QUIC versions
Format Reference: This document
Acknowledgments
Thanks to Ben Schwartz for his help with the Resource Record
formatting.
References
Normative References
[ALTSVC] Bishop, M. and M. Thomson, "HTTP Alternative Services",
Work in Progress, Internet-Draft, draft-ietf-httpbis-
rfc7838bis-00, 31 August 2021,
<https://datatracker.ietf.org/doc/html/draft-ietf-httpbis-
rfc7838bis-00>.
[I-D.ietf-dnsop-svcb-https]
Schwartz, B. M., Bishop, M., and E. Nygren, "Service
binding and parameter specification via the DNS (DNS SVCB
and HTTPS RRs)", Work in Progress, Internet-Draft, draft-
ietf-dnsop-svcb-https-12, 11 March 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-dnsop-
svcb-https-12>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", STD 68, RFC 5234,
DOI 10.17487/RFC5234, January 2008,
<https://www.rfc-editor.org/info/rfc5234>.
Informative References
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[RFC7301] Friedl, S., Popov, A., Langley, A., and E. Stephan,
"Transport Layer Security (TLS) Application-Layer Protocol
Negotiation Extension", RFC 7301, DOI 10.17487/RFC7301,
July 2014, <https://www.rfc-editor.org/info/rfc7301>.
[RFC9114] Bishop, M., Ed., "HTTP/3", RFC 9114, DOI 10.17487/RFC9114,
June 2022, <https://www.rfc-editor.org/info/rfc9114>.
[RFC8999] Thomson, M., "Version-Independent Properties of QUIC",
RFC 8999, DOI 10.17487/RFC8999, May 2021,
<https://www.rfc-editor.org/info/rfc8999>.
[RFC9000] Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
Multiplexed and Secure Transport", RFC 9000,
DOI 10.17487/RFC9000, May 2021,
<https://www.rfc-editor.org/info/rfc9000>.
Appendix A. Change Log
*RFC Editor's Note:* Please remove this section prior to
publication of a final version of this document.
A.1. since draft-duke-httpbis-quic-version-alt-svc-01
* No changes
A.2. since draft-duke-httpbis-quic-version-alt-svc-00
* Added SVCB and HTTPS Resource Records
Authors' Addresses
Martin Duke
Google
Email: martin.h.duke@gmail.com
Lucas Pardue
Cloudflare
Email: lucaspardue.24.7@gmail.com
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