2. Requirements

2. Requirements

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC 2119].

This document also uses internal conceptual variables to describe protocol behavior, as well as external variables that implementations must allow system administrators to change. The specific variable names, how their values change, and how their settings affect protocol behavior are provided to demonstrate protocol behavior. Implementations need not have them in the exact form described in this document, as long as their external behavior is consistent with the behavior described in this document.