| HTTPbis Working Group | M. Bishop |
| Internet-Draft | Akamai |
| Intended status: Standards Track | January 24, 2023 |
| Expires: July 28, 2023 |
The ORIGIN frame for HTTP/2 is equally applicable to HTTP/3, but needs to be separately registered. This document describes the ORIGIN frame for HTTP/3.¶
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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.¶
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.¶
Frame diagrams in this document use the format defined in Section 1.3 of [QUIC-TRANSPORT] to illustrate the order and size of fields.¶
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.¶
The ORIGIN frame has a nearly identical layout to that used in HTTP/2, restated here for clarity. The ORIGIN frame type is 0xc (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:¶
| Frame Type | Value | Specification |
|---|---|---|
| ORIGIN | 0xc | Section 2 |