-----Original Message-----
From: Doug Hurtig [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, June 06, 2001 6:26 PM
To: [EMAIL PROTECTED]
Subject: [Sip-implementors] To tag in 180 but not in final response
>Hi,
> I have a scenario in which a UAC sends an INVITE and then receives
> a 180. The 180 includes a to header with a tag. After the 180 is
received
> a "408 Request Timeout" final response is received. The 408 final
response
> does have a to header tag.
> I was under the impression that the UAS would send the same to tag once
> it sent the to tag. Without the to tag in the 408 final response the
UAC
>cannot
> tell if the 408 is from the same proxy or from a proxy which received a
>forked
> copy of the INVITE.
I think you mean to say "the 408 final response does NOT have a To header
tag". This is an error on the UAS, which is supposed to include a To tag in
all final responses.
Furthermore, if the UAS sets the tag in the 18x, it MUST use that same tag
in a final response. I don't think this is spelled out in the spec, but I
will add text saying that.
> If the UAS sends the 408 with a tag it will be accepted by the UAC even
if
> the 180 was never received by the UAC. This would occur as the final
>response
> would be the first response with a tag for the transaction.
> Are there valid cases in which the UAC should accept a subsequent
response
> without a to header tag once a response is received with a to header
tag?
This could happen if the request forks, and you get a 18x from one UAS, and
then later the 4xx from a different UAS. The 18x will have a tag from the
first UAS, and the 4xx is supposed to have a different tag, but some
implementations are bad in this regard, and for robustness, you might want
to accept that as if the tag were there of value zero.
-Jonathan R.
--
Regards,
Doug Hurtig
Tekelec
2425 N. Central Expressway
Richardson, Texas 75080
[EMAIL PROTECTED]
972.301.1203
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---
Jonathan D. Rosenberg, Ph.D. 72 Eagle Rock Ave.
Chief Scientist First Floor
dynamicsoft East Hanover, NJ 07936
[EMAIL PROTECTED] FAX: (973) 952-5050
http://www.jdrosen.net PHONE: (973) 952-5000
http://www.dynamicsoft.com
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