RFC 文档RFC 9977 - Publishing End-Site Prefix Lengths2. 需求语言本页总览2. 需求语言2. 需求语言 本文档中的关键词 "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" 只有在全部大写出现时, 才按 BCP 14 [RFC2119] [RFC8174] 中的描述解释.