[SIPForum-discussion] Regarding 180 ringing

[Bob Penfield]

If the UAC is a SIP phone, at some point the user will get tired of waiting and hang up causing the UAC to send a CANCEL. For a PSTN gateway, there would be a signal from the PSTN that the caller hung up (probably some sort of Release-Complete message), which would also cause the UAC to send a CANCEL.

If there are any proxies between the UAC and the UAS, they will maintain the transaction state for a period of Timer C (default of 180 seconds), which will restart with each provisional response it sees going from the UAS to the UAC.

Certainly a UA implementation is free to have some sort of maximum time that it waits for an answer after an early dialog is established by the provisional response before it gives up and sends a CANCEL. Probably a value less than the default Timer C value would be appropriate (so that the CANCEL does not hit a proxy that has discarded the transaction state).

See the discussions of Timer C in RFC 3261 - sections 16.6, 16.7, 16.8, and 18.

cheers,
(-:bob

________________________________
From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of Garron, James
Sent: Tuesday, May 05, 2009 3:49 PM
To: vijay kant gupta; discussion at sipforum.org
Subject: Re: [SIPForum-discussion] Regarding 180 ringing

Interesting question.

I believe that once you receive the provisional response putting the call into the proceeding state you would reset Timer B (T1*64), and that the call would stay in the proceeding state until receiving a final response of until Timer B is expires.  Of course if there were a retransmission of the provisional response that would reset Timer B again.

Jim


________________________________
From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of vijay kant gupta
Sent: Tuesday, May 05, 2009 1:48 AM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] Regarding 180 ringing

Hi ,

My question is

Q if uac receive 180 ringing and he didn't get any final response "under proceeding state so at that time which timer get expire and what is the duration for that timer?


Fig:--

                               |INVITE from TU

             Timer A fires     |INVITE sent

             Reset A,          V                      Timer B fires

             INVITE sent +-----------+                or Transport Err.





               +---------|           |---------------+inform TU

               |         |  Calling  |               |

               +-------->|           |-------------->|

                         +-----------+ 2xx           |





                            |  |       2xx to TU     |

                            |  |1xx                  |

    300-699 +---------------+  |1xx to TU            |

   ACK sent |                  |                     |





resp. to TU |  1xx             V                     |

            |  1xx to TU  -----------+               |

            |  +---------|           |               |

            |  |         |Proceeding |-------------->|





            |  +-------->|           | 2xx           |

            |            +-----------+ 2xx to TU     |

            |       300-699    |                     |

            |       ACK sent,  |                     |





            |       resp. to TU|                     |

            |                  |                     |      NOTE:

            |  300-699         V                     |

            |  ACK sent  +-----------+Transport Err. |  transitions





            |  +---------|           |Inform TU      |  labeled with

            |  |         | Completed |-------------->|  the event

            |  +-------->|           |               |  over the action





            |            +-----------+               |  to take

            |              ^   |                     |

            |              |   | Timer D fires       |

            +--------------+   | -                   |





                               |                     |

                               V                     |

                         +-----------+               |

                         |           |               |





                         | Terminated|<--------------+

                         |           |

                         +-----------+



                 Figure 5: INVITE client transaction



Need to modify RFC 3261 for handling that response or not , please specify your valuable comment .






ThanKs in advance



Regards



Vijay Gupta

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://sipforum.org/pipermail/discussion/attachments/20090505/be3f2b6c/attachment-0002.html>