Subject: [Sip] Re-Invite before ACK

From: "Miloslavsky Evgeny" <[email-masked]>
Date: Wed, 18 Jan 2006 19:44:06 +0200

Hello there.
What is an UAS behavior in case it recieves re-invite before it recieves
ACK to previously transmitted 200 OK for an initial Invite.
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From: Manish Joshi <[email-masked]>
Date: Wed, 18 Jan 2006 10:45:45 -0800 (PST)

Hi,
   
  The spec seems doesnt seem to be very clear on this. 
  An ACK to first Invite is a new transaction as the Invite transaction completed as soon as UAS sends final response as 200OK. UAC is now free to send a new re-invite along with the ACK to the first Invite. Now since the packet ordering is not _ensured_, a reinvite can always come to UAS before ACK and hence UAS should be able to accept it.
   
  BTW, this might also be an implementation option, where you chose to Ignore the re-invite in case the first INVITE did not have an offer and 200 OK was the one with the offer and ACK will contain the media-answer. 
   
  My two cents.
  -Manish

Miloslavsky Evgeny <[email-masked]> wrote:
      Hello there.
  What is an UAS behavior in case it recieves re-invite before it recieves ACK to previously transmitted 200 OK for an initial Invite.
_______________________________________________
Sip mailing list https://www1.ietf.org/mailman/listinfo/sip
This list is for NEW development of the core SIP Protocol
Use [email-masked] for questions on current sip
Use [email-masked] for new developments on the application of sip  

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From: "Brett Tate" <[email-masked]>
Date: Wed, 18 Jan 2006 14:15:45 -0500

> What is an UAS behavior in case it receives re-invite before 
> it receives ACK to previously transmitted 200 OK for an 
> initial Invite.

If the ACK is expected to contain an SDP, a 500 response with Retry-After
must be returned.  Otherwise I think that it is implementer specific to
accept it or return the 500 response.

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From: "James M. Polk" <[email-masked]>
Date: Wed, 18 Jan 2006 13:32:43 -0600

At 10:45 AM 1/18/2006 -0800, Manish Joshi wrote:
>An ACK to first Invite is a new transaction as the Invite transaction 
>completed as soon as UAS sends final response as 200OK. UAC is now free to 
>send a new re-invite along with the ACK to the first Invite.

I don't believe so.  I believe the stated behavior of the UAC is that it 
cannot send a new INVITE within a dialog until the ACK is sent.  The UAC is 
free to send any new INVITE outside of an existing dialog though. Section 
14.1 covers this I believe.

>Now since the packet ordering is not _ensured_, a reinvite can always come 
>to UAS before ACK and hence UAS should be able to accept it.

Section 14.2 faintly implies a 491 is appropriate for the reINVITE in this 
situation (prior to receiving the ACK to the original INVITE/200 OK exchange)

>
>BTW, this might also be an implementation option, where you chose to 
>Ignore the re-invite in case the first INVITE did not have an offer and 
>200 OK was the one with the offer and ACK will contain the media-answer.
>
>My two cents.
>-Manish
>
><http://us.rd.yahoo.com/mail_us/taglines/photobooks/*http://pa.yahoo.com/*http://us.rd.yahoo.com/mail_us/taglines/photos/evt=38088/*http://pg.photos.yahoo.com/ph//page?.file=photobook_splash.html>Photo 
>Books. You design it and we’ll bind it!

---

From: Manish Joshi <[email-masked]>
Date: Wed, 18 Jan 2006 11:42:15 -0800 (PST)

Iniline..

>>cannot send a new INVITE within a dialog until the ACK is sent. The UAC >>is free to send any new INVITE outside of an existing dialog though. >>Section 14.1 covers this I believe.

  Actually I think 14.1 supports more what I mentioned above:
   
  Quote:
  "   Note that a UAC MUST NOT initiate a new INVITE transaction within a
   dialog while another INVITE transaction is in progress in either
   direction.

      1. If there is an ongoing INVITE client transaction, the TU MUST
         wait until the transaction reaches the completed or terminated
         state before initiating the new INVITE."
  UNQUOTE
   
  ACK is a new transaction and receiving a final response (200OK) actually completes the INVITE transaction and hence UAC is free to Initiate a new (re)Invite transaction.

>Miloslavsky Evgeny wrote:

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---

From: Xiao Wang <[email-masked]>
Date: Fri, 20 Jan 2006 09:57:21 +0800

I  consider that ACK to INVITE's 200 OK is a individual transaction, but it
must send rapidly after receive

200 OK, otherwise it is no significance to acknowledge the INVITE
transaction. Even ACK send before the 

re-INVITE, for the reason of network delay, UAS may receive ACK after
re-INVITE.

 Deal with this scenario may be an implementation or client policy.

Xiao

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Manish
Joshi
Sent: Thursday, January 19, 2006 3:42 AM
To: James M. Polk; Miloslavsky Evgeny; [email-masked]
Subject: Re: [Sip] Re-Invite before ACK

Iniline..

"James M. Polk" <[email-masked]> wrote: 

>>cannot send a new INVITE within a dialog until the ACK is sent. The UAC
>>is free to send any new INVITE outside of an existing dialog though.
>>Section 14.1 covers this I believe.

Quote:

UNQUOTE

ACK is a new transaction and receiving a final response (200OK) actually
completes the INVITE transaction and hence UAC is free to Initiate a new
(re)Invite transaction.

>Yahoo! Photos - Showcase holiday pictures in hardcover
>Photo 
>Books. You design it and we'll bind it!

  _____  

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