Subject: [Sip] Session Timer Questions.

From: "Padhye, Chinmay" <[email-masked]>
Date: Tue, 27 Nov 2001 18:48:29 -0800

Hello,

	I have a confusion in one section of the session timer draft.
(version - 08)

	In section 7.1 it says -
	"The UAC MUST insert the Min-SE header into a re-INVITE request for
a particular call leg if it has ever received a 422 response to a previous
INVITE on the same leg, or if it has received an INVITE on that call leg
which contained a Min-SE header."
	
	This is talking about a re-INVITE. Is this correct? 

	The next sentence is -

	"Similarly, if no call leg has been established yet, a UAC MUST
insert the Min-SE header into an INVITE request for a particular call if it
has ever received a 422 response to a previous INVITE with the same Call-ID"

	The last sentence is confusing to me. First of all if no call leg
has been established then the 422 was for the initial INVITE. Is this
correct? Can a uac receive a 422 for the first INVITE and still consider the
call alive?

	If a uac receives a 422 error response to an INVITE with call id
(CID) 1, then is it a 'MUST' for the uac to reuse CID 1 for the second
INVITE with a new Session-Expires header? Why cant the uac use CID 2?

Regards,

Chinmay

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---

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 28 Nov 2001 00:22:30 -0500

> -----Original Message-----
> From: Padhye, Chinmay [mailto:[email-masked]]
> Sent: Tuesday, November 27, 2001 9:48 PM
> To: [email-masked]'; [email-masked]'
> Cc: [email-masked]'
> Subject: Session Timer Questions.
> 
> 
> Hello,
> 

Yes.

> correct? Can a uac receive a 422 for the first INVITE and 

There is no call; thats why it says you should insert the Min-SE if you ever
sent an INVITE previously with the same Call-ID value, and got a 422. So, I
send you an invite, I get a 422. Now, I try again. This attempt is NOT a
re-invite, but it shares the same call-id, so it includes a Min-SE.

> INVITE with a new Session-Expires header? Why cant the uac use CID 2?

It could, nothing can stop that. The idea is that the behavior of retrying
the invite is to use the same call-id. This is probably not clear in bis, in
fact, and it needs to be. Its discussed for 401/407, but not more generally.

-Jonathan R.

---
Jonathan D. Rosenberg, Ph.D.                72 Eagle Rock Ave.
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