[SIPForum-discussion] urgent 491

[=?gb2312?q?=D3=EA=20=B3=C2?=]

Hi, Herve and all,
  Now I am recording the SIP call flowing, but there is a  problem about the response 491 .
  The call flowing as follows£º
    UA1                        UA2     TIME
       

               Both way RTP Media
  ç==========================¨¨  
  [254]INVITE[SDP]   
  ç--------------------------     09:18:31:052
  [255]INVITE[SDP]  
  ----------------------------¨¨   09:18:31:065
      [256]100
  ----------------------------¨¨   09:18:31:065
      [257]491
  ----------------------------¨¨   09:18:31:065
      [259]100
  ç-------------------------------------       09:18:31:071
      [260]491
  ç-------------------------------------       09:18:31:071
                      [261] ACK
  ç----------------------------   09:18:31:071
                      [263]ACK
  -----------------------------¨¨   09:18:31:085
            [2639] INVITE [SDP]
  ---------------------------------------¨¨      09:19:01:092
  ¡­¡­¡­¡­
  As we can see, the session has already set up and the entire message in this flow have the same dialog-ID. Now both UA1 and UA2 re-invite each other just simultaneously, then they get 491 as response from the other one. Well, after 30s, the UA1 send a INVITE again which is NO.2639 with SDP. My question is :
  1.       Since no relevant message during the 30s space time, does the NO.2639 INVITE still belong to the call flow ?
  2.       Is the response 491 like 487, which means the existed session will be terminated?   
   
  In fact, the RFC3621 have just mentioned the UAC should start a timer when it received a 491 response, but not described what will happen, if the timer fires and the UAC don¡¯t attempt the re-INVITE once more.
   
  I look forward to the answer urgently,anything is helpful !
   
  RE
   
  Nora

       
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