res.</li>
    </ul>
    <h2 id="Requirements">3. Requirements</h2>
    <p>
        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 
        <a href="http://www.ietf.org/rfc/rfc2119.txt">RFC 2119</a>.</p>
    <p>
        An implementation is not compliant if it fails to satisfy one or more
        of the MUST requirements for the protocols it implements.  An
        implementatio