\section*{Changes in Version -04}

Since version -03, the following changes have been made. 

\begin{itemize}
\item The introduction has been reorganized and large parts rewritten. 

\item {\CONNECTED} changed to {\ACK}, as it applies to all responses,
not just 200.

\item Status code 181 (Queued) and \header{Call-Disposition:  Queue} added.

\item Status code 481 (Invalid Call-ID) added.

\item Status code 482 (Loop Detected) added. Via description contains
motivation. 

\item Allow phone numbers in SIP URL for easy connection to Internet
telephony gateways.

\item Added \header{Also} header for third-party connectivity.

\item When doing parallel searches, pending searches should be aborted
when one address was successful. The phone call may be ringing on a
number of workstations where the user is logged in and would keep
ringing.

\item Added \header{duration} parameter to \header{Retry-After} to indicate
how long the callee is likely to be reachable at the address given.

\item Changed \header{Sequence} to \header{CSeq} for consistency with RTSP.

\end{itemize}
