\section{Changes Made in Version 04}

\begin{itemize}

%jdr 5/29/01
\item Removed Unsupported as a request header from Table \ref{tab:headers2}.

\item Clarified SDP procedures for changing IP address and
port. Specifically, spelled out the duration for which a UA needs to
received media on the old port and address.

%jdr 6/01/01
\item Added text in the SDP session which recommends that the answerer
use the same ordering of codecs as used on the offer, in order to help
ensure symmetric codec operation under normal conditions.

%jdr 6/01/01
\item Fixed bug in the example in the SDP section, where the new media
line was listed at the top. Should have been the bottom.

%jdr 6.01.01
\item \header{Authorization} credentials are cached based on the URL
of the \header{To} header, not the entire \header{To} header as 10.48
implied.

%jdr 6.01.01
\item Section 10.31, on \header{Proxy-Authenticate}, indicated that a
server responds with a 401 if the client guessed wrong. This is
incorrect. It should be 407.

%jdr 6.01.01
\item Section 10.14, removed motivational text about \header{Contact}
allowing an {\INVITE} to be routed directly between end systems, since
its confusing.  Some have interpreted to mean that \header{Record-Route}
is ignored when \header{Contact} is present.

\item Added reference to SCTP RFC.

%jdr 6.10.01
\item Updated 2.2 to allow non-SIP URLs in {\OPTIONS} and 2xx to
{\OPTIONS}. 

%jdr 6.10.01
\item Fixed example in 20.5. Added {\ACK} for 487, and added
\header{To} tag to 487 response.

%jdr 6.12.01
\item Clarified further URL comparisons. Its only URL parameters
without defaults that are ignored if not present in both URLs.

%jdr 6.12.01
\item Section 1.5.2, UDP mandatory for all. TCP is a {\SHOULD} for UA,
{\MUST} for proxy, registrar, redirect servers.

%jdr 6.12.01
\item Brought syntax for \header{Contact}, \header{Via}, and the SIP
URL into alignment between the text and postscript versions.

%jdr 6.12.01
\item Updated the text in section 6 which said that the ordering of
header fields follows HTTP, with the exception of \header{Via}, where
order matters. However, the HTTP spec says that order matters, so this
sentence is redundant and confusing. The sentence was removed.

%jdr 6.12.01
\item Added e lines to SDP examples in the Examples section.

%jdr 6.14.01
\item Rewrote \header{Allow} discussion, more formally defining its
semantics and usage cases.

%jdr 6.15.01
\item Updated text on 604 status, to indicate that its based on the
\header{Request-URI}, not the \header{To}.

%jdr 6.15.01
\item Added response registrations to IANA considerations. Provided
more details on registration process.

%jdr 6.22.01
\item Clarified that only a UAS rejects a request because the
\header{To} tag doesn't match a local value.

%jdr 6.25.01
\item Clarified that stateless proxies need to route based on static
criteria only.

%jdr 6.25.01
\item Proxy and UAC {\CANCEL} generation upon 2xx, 6xx if it forked is
now a {\SHOULD}; used to be a {\MAY}. 

%jdr 6.25.01
\item Added text saying that a UAS {\SHOULD} send a {\BYE} if it never
gets an {\ACK} for a 2xx establishing a call leg.

%jdr 6.25.01
\item Added text saying that a UAS {\SHOULD} send a re-{\INVITE} if it
never gets an {\ACK} for a 2xx to a re-{\INVITE}.

%jdr 6.25.01
\item Added text on 503 processing, indicating that a client should
try a different server when receiving a 503, and that a proxy
shouldn't forward a 503 upstream unless it can't service any
other requests.

%jdr 7.03.01
\item Removed motivational text in Section 10.43 on \header{Via}
headers since its not consistent with the text before it.

%jdr 7.06.01
\item Changed IPSec reference to RFC~2401, from RFC~1825.

%jdr 7.11.01
\item Updated retransmission defininition in 17.3.4 to be consistent
with the rest of the spec.

%jdr 7.16.01
\item Softened the language for insertion of the transport param in
the record-route. Specifically, it can be inserted in private networks
where it is known apriori that the specific transport is supported.

%jdr 7.20.01
\item Updated definition of B2BUA.

%jdr 7.20.01
\item Added text to section on 420 processing, which mandates that the
client retry the request without extensions listed in the
\header{Unsupported} header in the response.

%jdr 7.20.01
\item Allow \header{Authentication-Info} header to be used for HTTP
digest. 

\end{itemize}