[SIPForum-discussion] Is to-tag mandatory ?

[Garron, James]

8.2.6 Generating the Response

When a UAS wishes to construct a response to a request, it follows the general procedures detailed in the following subsections. Additional behaviors specific to the response code in question, which are not detailed in this section, may also be required.

Once all procedures associated with the creation of a response have been completed, the UAS hands the response back to the server transaction from which it received the request.
8.2.6.2 Headers and Tags

The From field of the response MUST equal the From header field of the request. The Call-ID header field of the response MUST equal the Call-ID header field of the request. The CSeq header field of the response MUST equal the CSeq field of the request. The Via header field values in the response MUST equal the Via header field values in the request and MUST maintain the same ordering.

If a request contained a To tag in the request, the To header field in the response MUST equal that of the request. However, if the To header field in the request did not contain a tag, the URI in the To header field in the response MUST equal the URI in the To header field; additionally, the UAS MUST add a tag to the To header field in the response (with the exception of the 100 (Trying) response, in which a tag MAY be present). This serves to identify the UAS that is responding, possibly resulting in a component of a dialog ID. The same tag MUST be used for all responses to that request, both final and provisional (again excepting the 100 (Trying)). Procedures for the generation of tags are defined in Section 19.3<http://10.158.143.150/wiki/RFC/RFC3261.htm#sec-19.3>.


From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of vikas jain
Sent: Friday, July 27, 2012 9:10 AM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] Is to-tag mandatory ?

Hello All,

Is to-tag mandatory for 3xx-6xx responses ( specially in 302 response ) ? I didn't find it in RFC 3261.
Please help.

Thanks,
Vikas Jain
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