[SIPForum-discussion] Regarding To-Tag in 180 Ringing

[Raj Jain]

It is not optional for non-100 provisional responses. Here is a quote
from section 8.2.6.2 of RFC 3261

   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.

On Thu, Oct 23, 2008 at 12:57 PM, saraswati sp <saraswatisp at gmail.com> wrote:
> Hi everyone,
>
>     Is generation of To-Tag Mandatory/Optional in 180 provisional response??
>
> If Optional, then under which condition is it generated??
>
> Thanks in advance.
>
> Regards,
> Saras.
>
>
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