The ORIGIN Extension in HTTP/3Akamaimbishop@evequefou.be
Applications and Real-Time
HTTPbisInternet-DraftThe 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.IntroductionExisting RFCs define extensions to HTTP/2 which remain useful in HTTP/3. describes the required updates for HTTP/2 frames to be used with HTTP/3. defines the HTTP/2 ORIGIN frame, which indicates what origins are available on a given connection. It defines a single HTTP/2 frame type.Notational ConventionsThe 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 when, and only when, they appear in all capitals, as shown here.Frame diagrams in this document use the format defined in to illustrate the order and size of fields.The ORIGIN HTTP/3 FrameThe ORIGIN HTTP/3 frame allows a server to indicate what origin(s) () the server would like the client to consider as members of the Origin Set () for the connection within which it occurs.The semantics of the frame payload are identical to those of the HTTP/2 frame defined in . 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 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.Frame LayoutThe 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 (..) …,
}
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 () that the sender asserts this connection is or could be authoritative for.
Security ConsiderationsThis document introduces no new security considerations beyond those discussed in and .IANA ConsiderationsThis document registers a frame type in the “HTTP/3 Frame Type” registry ().Frame TypeValueSpecificationORIGIN0xcHTTP/2HTTP/3The ORIGIN HTTP/2 FrameKey words for use in RFCs to Indicate Requirement LevelsAmbiguity of Uppercase vs Lowercase in RFC 2119 Key WordsQUIC: A UDP-Based Multiplexed and Secure TransportThe Web Origin Concept