1. Introduction

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", "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.

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