Certification Authority Authorisation

The CAA resource record (RFC 8659 section 4.1) — three fields: an 8-bit flag byte, an ASCII-alphanumeric property tag (1..255 bytes), and the property's value (free-form bytes).

Tags are compared case-sensitively when comparing T_caa RData objects. CAs are required by RFC 8659 to handle tags case-insensitively; that's a check for application-layer code, not for the wire-format codec. Use validCaaTag to verify a tag's syntactic constraints before encoding.

The Ord instance compares the flag byte, then tag length, then tag bytes, then value bytes — wire-encoding order, so it agrees with the canonical RR-content ordering of RFC 4034 section 6.2.

Verify a CAA tag's syntactic constraints: non-empty and made entirely of ASCII alphanumeric bytes (RFC 8659 section 4.2). Required before encoding; the decoder applies the same check and rejects a wire-form T_caa whose tag fails it.