2. Notational Conventions

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" are interpreted as described in BCP 14 [RFC2119] [RFC8174] when they appear in all capitals.

ABNF definitions use the notation of [RFC5234]. ABNF rules not defined here are defined in [RFC5234], for example CRLF, WSP, DQUOTE, VCHAR, ALPHA, and DIGIT, or in [RFC6350].