\section{Changes in Version -11}

Since version -10, the following changes have been made.  These changes
reflect IESG comments. 

\begin{itemize}
\item Respecting DNS TTL's for cacheing of queries changed from
{\SHOULD} to {\MUST}.

\item Default MTU for UDP requests changed from 1400 to 1500.

\item Added note to status 480 indicating that a redirect server could
use this as well to indicate that it doesn't know where the user is, for
example, because all of the user's contact information has expired.

\item Added description for status 305.  (May need to consider whether
we need both \header{Location} and \header{Contact} here, for
compatibility with HTTP.)

\item Use of CRLF for line termination is a {\SHOULD}.

\item Clarifications and minor changes in DNS procedures for finding a
SIP server.

\item Message retransmission timers exponentially back off 
(incorporated since -09).

\item BNF fixed up, changed TEXT BNF to allow for UTF-8.

\item More explicit rules on using HTTP basic and digest were
added. Proxy-to-proxy authentication is disallowed due to
incompatibilities with UDP transport.

\item IANA registered options are prefixed by org.iana.sip instead of
org.ietf.sip.

\item Date, Expires field only supports RFC 1123 formatting, as opposed
to HTTP, which also supports RFC 850 and asctime date formats.

\item Changed the default reason phrase for 413 to align with the
newest HTTP revision.

\item Added requirement for CRLF line termination in canonicalization
rules. Clarified canonicalization rules

\item Default language for \header{warn-text} changed from English to
i-default.

\item Use of transport and network level security changed to {\MAY} from
{\RECOMMENDED}.

\item Mandated use of the \header{name-addr} form in the \header{To}
field if \header{addr-spec} contains a semicolon, comma, or question
mark.  This is in line with \header{From} and \header{Contact}, but was
omitted from the To section accidentally in previous versions

\item Fixed deviation in BNF between ASCII and PostScript versions of
spec.

\item Made consistent the usage of the \header{Contact}
\header{expires} parameter.

\item Fixed inconsistency in usage of \header{Contact} header in 181 and
1xx responses.

\item Fixed inconsistency regarding encryption of \header{Call-ID}. 
\header{Call-ID} should be in the clear.

\item Rewrote SDP section for greater clarity; included discussion of
behavior for delayed session description.

\item Updated minimal requirements table, correcting inconsistencies
with the text.

\item Changed state diagram to include timing information.

\item Added \header{nonce} parameter in PGP \header{WWW-Authenticate}
and \header{Authorization} header fields to prevent replay attacks.

\item Fixed inconsistent use of quotation marks (between example and
syntax) for \header{version} and \header{pgp-algorithm} in PGP (Ch. 
14).

\item \header{delta-time} values may be capped at 2**32.

\end{itemize}
