Kapil, Here is my two cents for your query whether is allowed in 18 and 2xx or not and why one has not seen any usage of reason header in 18x and 200ok so far but has seen it only in error responses.
First one is already answered by you and our friends by referring to RFC-3326. But RFC-3326 also states that: " Note that the Reason header field is usually not needed in responses because the status code and the reason phrase already provide sufficient information." Which means that generally whenever we are sending responses we already have enough information carried in respLn, so there is no unique reason for including "reason header". But let us take the case of SIP-PSTN interworking, where ISUP side may be releasing the call with some cause-value. Now there is an RFC to specify ISUP cause to SIP response code mapping. But let us say for some reason if the orginating guy is interested in uniquely knowing the ISUP side cause value and reason rather than referring to this ISUP-SIP mapping table which may be mapping multiple causes to same resp code. In that case uniquely passing ISUP side release cause value can be done by including that information in reason header of "error responses 4xx-6xx". Right. That would be one reason I think we still see error responses carrying "reason header". I can not think of any such thing which can be carried in 18x, 2xx and 3xx which is not already carried in respLn as indicated above in RFC-3326 reference. Best Regards, Indresh K Singh >>-----Original Message----- >>From: [email protected] >>[mailto:[email protected]] On >>Behalf Of ext Kapil Saxena >>Sent: Thursday, August 13, 2009 5:30 AM >>To: [email protected] >>Subject: [Sip-implementors] Can Reason header be inluded in >>18x and 200 OKresponses to INVITE ? >> >>RFC 3326 states following: >> >> >>The Reason header field MAY appear in any request within a dialog, in >> >> any CANCEL request and in any response whose status code explicitly >> >> allows the presence of this header field. The syntax of the header >> >> field follows the standard SIP parameter syntax. >> >>Does it imply that 18x and 200 OK can also contain Reason >>header ? I have come across examples where "Reason" header is >>included in >>INVITE, CANCEL, BYE, 4xx responses but have not found any 1xx >>or 200 OK (for INVITE) containing "Reason" header ? >> >>Pl. clarify ? >> >>Thanks >>Kapil Saxena >>_______________________________________________ >>Sip-implementors mailing list >>[email protected] >>https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors >> _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
