2: Usage of keywords

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document and in all documents in it's subtree as well as all documents that are directly related to this document are to be interpreted as described in https://tools.ietf.org/html/bcp14[BCP 14], https://tools.ietf.org/html/rfc2119[RFC2119] and https://tools.ietf.org/html/rfc8174[RFC8174] when, and only when, they appear in all capitals, as shown here.