The ORIGIN Extension in HTTP/3

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Table of Contents

1. Introduction

Existing RFCs define extensions to HTTP/2 [HTTP2] which remain useful in HTTP/3. Appendix A.2.3 of [HTTP3] 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.¶

2. The ORIGIN HTTP/3 Frame

The ORIGIN HTTP/3 frame allows a server to indicate what origin(s) ([RFC6454]) the server would like the client to consider as 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 should be sent on Stream 0, this should be interpreted to mean the HTTP/3 control stream. 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.¶

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

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

3. Security Considerations

This document introduces no new security considerations beyond those discussed in [ORIGIN] and [HTTP3].¶

4. IANA Considerations

This document registers a frame type in the "HTTP/3 Frame Type" registry ([HTTP3]).¶

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