[SIPForum-discussion] A question about INVITE fork

[Đani Vladislavić]

Hi,

it is possible that UAC receives second 180 if the 180 is triggered from the UAS2 side before it receives CANCEL. In that scenario, no action will be taken on UAC side (since it has already created confirmed dialog and this is the response that does not create confirmed dialog). The UAS2 will return 200OK for CANCEL and 487 for INVITE which will not be propagated by proxy to UAC.

regards,
Djani

--- On Fri, 5/8/09, Tomasz Zieleniewski <tzieleniewski at gmail.com> wrote:
From: Tomasz Zieleniewski <tzieleniewski at gmail.com>
Subject: Re: [SIPForum-discussion] A question about INVITE fork
To: "Sunny" <guangu.he at gmail.com>
Cc: "SIP FORUM" <discussion at sipforum.org>
Date: Friday, May 8, 2009, 10:39 PM

Hi,

If proxy is stateful it holds the information about incoming request, the requests which 
it sends as the result of this request processing by proxy core and request responses. 
In case when proxy forks the request, there may be many outgoing requests and responses

corresponding to different destinations.
In such case there are some rules about proxy behavior. When proxy forks the request, it
tries to choose the best answer for the request with the exception of 1xx and 2xx responses.

Any provisional response, except 100 which is sent hop by hop, must be sent upstream to UAC
immediately. But still proxy is unable to decide which transaction  will complete first.
That's why whenever proxy receives first 2xx response it forwards it immediately upstream to UAC

and cancels any other transactions it established downstream towards the destination.
So UAC will not receive second 180 response because this transaction would be canceled by proxy.

Kind regards,
- Tomasz Zieleniewski 



2009/5/6 Sunny <guangu.he at gmail.com>

Hi allI have a question about INVITE fork. see follow picture.
UAC                     Proxy            UAS1             UAS2   |---------INVITE----->|                      |                     |

   |                          |-------INVITE--->|                     |   |                          |----------------------|-------INVITE-->|   |                          |<-------200--------|                     |

   |<--------200---------- |                      |                     |   |----------ACK------->|                       |                    |   |                          |---------ACK----->|                    |

   |                          |                       |                    |   |                          |<-------------180---|--------------------|   |<------180-------------|


when UAC received UAS2 180, the UAC have not corresponding transaction,the UAC will discard 180 or other?
-- 
Thanks

Sunny



_______________________________________________

This is the SIP Forum discussion mailing list

TO UNSUBSCRIBE, or edit your delivery options, please visit http://sipforum.org/mailman/listinfo/discussion

Post to the list at discussion at sipforum.org




_______________________________________________
This is the SIP Forum discussion mailing list
TO UNSUBSCRIBE, or edit your delivery options, please visit
http://sipforum.org/mailman/listinfo/discussion
Post to the list at discussion at sipforum.org



      
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sipforum.org/pipermail/discussion/attachments/20090509/70a6fcb3/attachment-0002.html>