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The ORIGIN Extension in HTTP/3
RFC 9412

Document Type RFC - Proposed Standard (June 2023)
Author Mike Bishop
Last updated 2023-06-12
RFC stream Internet Engineering Task Force (IETF)
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IESG Responsible AD Francesca Palombini
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RFC 9412

Internet Engineering Task Force (IETF)                         M. Bishop
Request for Comments: 9412                                        Akamai
Category: Standards Track                                      June 2023
ISSN: 2070-1721

                     The ORIGIN Extension in HTTP/3


   The ORIGIN frame for HTTP/2 is equally applicable to HTTP/3, but it
   needs to be separately registered.  This document describes the
   ORIGIN frame for HTTP/3.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at

Copyright Notice

   Copyright (c) 2023 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Revised BSD License text as described in Section 4.e of the
   Trust Legal Provisions and are provided without warranty as described
   in the Revised BSD License.

Table of Contents

   1.  Introduction
     1.1.  Notational Conventions
   2.  The ORIGIN HTTP/3 Frame
     2.1.  Frame Layout
   3.  Security Considerations
   4.  IANA Considerations
   5.  References
     5.1.  Normative References
     5.2.  Informative References
   Author's Address

1.  Introduction

   Existing RFCs define extensions to HTTP/2 [HTTP/2] that remain useful
   in HTTP/3.  Appendix A.2 of [HTTP/3] describes the required updates
   for HTTP/2 frames to be used with HTTP/3.

   [ORIGIN] defines the HTTP/2 ORIGIN frame, which indicates what
   origins are available on a given connection.  It defines a single
   HTTP/2 frame type.

1.1.  Notational Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "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.

   The frame diagram in this document uses the format defined in
   Section 1.3 of [QUIC-TRANSPORT] to illustrate the order and size of

2.  The ORIGIN HTTP/3 Frame

   The ORIGIN HTTP/3 frame allows a server to indicate what origin or
   origins [RFC6454] the server would like the client to consider as one
   or more members of the Origin Set (Section 2.3 of [ORIGIN]) for the
   connection within which it occurs.

   The semantics of the frame payload are identical to those of the
   HTTP/2 frame defined in [ORIGIN].  Where HTTP/2 reserves stream 0 for
   frames related to the state of the connection, HTTP/3 defines a pair
   of unidirectional streams called "control streams" for this purpose.

   Where [ORIGIN] indicates that the ORIGIN frame is sent on stream 0,
   this should be interpreted to mean the HTTP/3 control stream: that
   is, the ORIGIN frame is sent from servers to clients on the server's
   control stream.

   HTTP/3 does not define a Flags field in the generic frame layout.  As
   no flags have been defined for the ORIGIN frame, this specification
   does not define a mechanism for communicating such flags in HTTP/3.

2.1.  Frame Layout

   The ORIGIN frame has a layout that is nearly identical to the layout
   used in HTTP/2; the information is restated here for clarity.  The
   ORIGIN frame type is 0x0c (decimal 12), as in HTTP/2.  The payload
   contains zero or more instances of the Origin-Entry field.

   HTTP/3 Origin-Entry {
     Origin-Len (16),
     ASCII-Origin (..),

   HTTP/3 ORIGIN Frame {
     Type (i) = 0x0c,
     Length (i),
     Origin-Entry (..) ...,

                       Figure 1: ORIGIN Frame Layout

   An Origin-Entry is a length-delimited string.  Specifically, it
   contains two fields:

   Origin-Len:  An unsigned, 16-bit integer indicating the length, in
      octets, of the ASCII-Origin field.

   ASCII-Origin:  An OPTIONAL sequence of characters containing the
      ASCII serialization of an origin ([RFC6454], Section 6.2) that the
      sender asserts this connection is or could be authoritative for.

3.  Security Considerations

   This document introduces no new security considerations beyond those
   discussed in [ORIGIN] and [HTTP/3].

4.  IANA Considerations

   This document registers a frame type in the "HTTP/3 Frame Types"
   registry defined by [HTTP/3], located at

   Value:  0x0c
   Frame Type:  ORIGIN
   Status:  permanent
   Reference:  Section 2
   Date:  2023-03-14
   Change Controller:  IETF
   Contact:  HTTP WG <>

5.  References

5.1.  Normative References

   [HTTP/2]   Thomson, M., Ed. and C. Benfield, Ed., "HTTP/2", RFC 9113,
              DOI 10.17487/RFC9113, June 2022,

   [HTTP/3]   Bishop, M., Ed., "HTTP/3", RFC 9114, DOI 10.17487/RFC9114,
              June 2022, <>.

   [ORIGIN]   Nottingham, M. and E. Nygren, "The ORIGIN HTTP/2 Frame",
              RFC 8336, DOI 10.17487/RFC8336, March 2018,

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <>.

5.2.  Informative References

              Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,

   [RFC6454]  Barth, A., "The Web Origin Concept", RFC 6454,
              DOI 10.17487/RFC6454, December 2011,

Author's Address

   Mike Bishop