> The TEXT-UTF8 rule is only used for descriptive field contents and
values that are not intended to be interpreted by the message parser.
Words of *TEXT-UTF8 contain characters from the UTF-8 charset (RFC
2279 [7]). The TEXT-UTF8-TRIM rule is used for descriptive field
contents that are n t quoted strings, where leading and trailing LWS
is not meaningful. In this regard, SIP differs from HTTP, which uses
the ISO 8859-1 character set.