\section{Terminology}
\label{sec:terminology}

In this document, the key words ``{\MUST}'', ``{\MUSTNOT}'',  
``{\REQUIRED}'', ``{\SHALL}'', ``{\SHALLNOT}'', ``{\SHOULD}'',
``{\SHOULDNOT}'', ``{\RECOMMENDED}'', 
``{\NOTRECOMMENDED}'',
``{\MAY}'', and ``{\OPTIONAL}''
are to be interpreted as described in RFC 2119 \citenorm{rfc2119} and
indicate requirement levels for compliant SIP implementations.
