> -----Original Message----- > From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] > Sent: 22 October 2007 01:53 > To: [email protected] > Subject: [Sip] Use of the Require header in responses > > This message is to clarify an issue that has been causing me some > confusion, namely the meaning and use of the Require header in > responses. I hope it helps others avoid my mistakes. > > The bulk of RFC 3261 (including section 8.1.1.9 "Supported and > Require", 20.32 "Require", and 20.37 "Supported") describes the use of > the Supported and Require headers in a very straightforward way: > Supported is used to inform the other end of a dialog that the UA > supports the specified extensions. Require is used in requests to > compel the other UA to reject a request if the other UA does not > support the specified extensions. > > Within this framework, using Require in a response is pointless -- if > the UAC does not support the extension, it would be required to > discard the response, thus leaving it with no way of knowing that the > UAS wants to make use of the extension. > > However, there is separate meaning for Require when it is used in a > response, namely to indicate that the UAS has performed some > particular processing specified in the extension in question. > > This use is described in section 8.2.4 "Applying Extensions": > > Any extensions applied to a non-421 response MUST be listed in a > Require header field included in the response. Of course, > the server > MUST NOT apply extensions not listed in the Supported > header field in > the request. > > Of course, exactly what processing is implied by a Require header in a > response is determined by the specification of the extension in > question. > > If I recall correctly, there are three extensions or proposed > extensions that use Require headers in responses routinely. One is > the GRUU extension, but I've forgotten the other two. [JRE] I think RFC 3262 is one such extension.
John _______________________________________________ Sip mailing list https://www1.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use [EMAIL PROTECTED] for questions on current sip Use [EMAIL PROTECTED] for new developments on the application of sip
