26 Mar
2018
26 Mar
'18
10:49 p.m.
On Mon, Mar 26, 2018 at 10:27:35PM +0200, Henning Westerholt wrote:
I would think this is normal UAC/UAS behavior for SIP
request handling:
RFC 3261, sect. 8.2.6.2:
"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. "
Honestly, in ten years of doing SIP, this is the first time I am
confronting this question. I was accustomed to the notion that To tags
are only added to a reply when it is desirable to form an early dialog
(in the case of a non-100 1xx reply). But the passage you quote seems to
settle it.
--
Alex Balashov | Principal | Evariste Systems LLC
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