[SIPForum-discussion] 100 Tring for Re-invite

[hemanth kumar]

To classify an INVITE as a reINVITE, the dialog ID(From tag, To tag and call-id) of reINVITE should be the same as INVITE. In that case, when a UAC sends a reINVITE, it would have the To tag. when it reaches proxy, proxy would build 100 Trying from the reINVITE received. Hence 100 Trying would also have a To Tag no matter who builds the 100 Trying message(Proxy or UAS).

  -Hemanth
   
  
Rajnish Jain <rj at pscientific.com> wrote:
      No. 
   
  Remember 100-Trying is a hop-by-hop (not end-to-end) message. If it helps understanding, think of it like a transaction-layer message instead of a dialog-layer message. 
   
  If the UAC (the generator of the RE-INVITE transaction) receives a 100-Trying, that response has been most likely generated by the UAC's next hop proxy. In such a case, the 100-Trying can not contain To-tag.
   
  So, what happens when there is no proxy between the UAC and the UAS (the case presented in the question)? In this case, it depends on the UAS implementation whether it sends To-tag in the 100-Trying or not. The UAC should be prepared to handle either scenarios. 
   
  It is most likely that the UAS will NOT add the To-tag in 100-Trying (in most cases the 100-Trying is generated independently by the UAS' transaction layer which has no clue about the dialog and therefore the To-tag).  
   

      
---------------------------------
  From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of hemanth kumar
Sent: Wednesday, November 08, 2006 10:53 PM
To: Manpreet Singh; Rajangam.Subramanian at alcatel.com; discussion at sipforum.org
Subject: Re: [SIPForum-discussion] 100 Tring for Re-invite


  
  Hi,
   
  100 Trying is built from the INVITE message. As the reINVITE would have all the information related to a dialog, 100 Trying for reINVITE would be generated based on the reINVITE. Hence it would have all the information related to dialog
  including To-tag.
   
  Regards
  Hemanth

Manpreet Singh <msingh at ibasis.net> wrote:
      I believe the 100 Trying to the Re-invite must carry the To-Tag. It doesn't explicitly say anywhere for 100trying whether it can or cannot carry  a To-Tag when the INVITE carries it. It does say its optional to send for 100trying when the initial invite didn't carry one. So I guess the rules in section 8.6.2 in rfc 3261 would apply for 100Trying for a re-invite. 
  Manpreet 
  -----Original Message----- 
From: Rajangam.Subramanian at alcatel.com [mailto:Rajangam.Subramanian at alcatel.com] 
Sent: Thursday, October 19, 2006 3:29 PM 
To: discussion at sipforum.org 
Subject: [SIPForum-discussion] 100 Tring for Re-invite 
  Hello all, 
    I a query related to 100 Trying response for RE-Invite message. 
  The following is the scenario. A and B are 2 SIP UA's. A successful SIP call is established between A and B. 
  Now A wants to invoke some service and sends a Re-INVITE to B. 
This Re-Invite to B will have a valid"To-tag" in the To header (as this is a re-invite) 
  B sends a 100 Trying for this RE-Invite. 
  My Question is: Is it necessary for  this 100 Trying to Re-Invite to have To-tag. Or can UA B send a 100 trying with out a to-tag.
          
Regards, 
Rajangam 
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Chenji Hemanth Kumar 
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Chenji Hemanth Kumar 
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Ph: 23404007 
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 Send instant messages to your online friends http://uk.messenger.yahoo.com 
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