[SIPForum-discussion] a question about re-invite

abhishek.chattopadhyay at wipro.com abhishek.chattopadhyay at wipro.com
Thu Jun 4 08:21:19 UTC 2009

Hello Nancy,

SIP RE-Invite method is a mechanism of refreshing the session primarily and not changing the session itself.

Moreover if suppose A and B are in session and somehow B wants A to talk to C then the method refer would be used.
There are other implementations where a re-invite is sent to achieve the same objective. This depends upon implementation largely.
The fact all such cases where re-invite is used in place of refer to achieve similar functionalities there are serious resource compromises to mitigate.

Moving further 
Answer to question one: 
If I consider A,B,C are all UAC then no as because C would not be ready to receive a response for the request it never generated and would discard it. 
Such a scenario can be seen where A receives a Request from C and then generates the Invite towards B on behalf of C.

Answer to question two:
Call-id, to tag, from tag are session wise unique in the space and time, they might not be used by other clients as they would be used to identify dialog and session between agents.


-----Original Message-----
From: discussion-bounces at sipforum.org [mailto:discussion-bounces at sipforum.org] On Behalf Of fanyanping
Sent: Wednesday, June 03, 2009 9:38 AM
To: discussion at sipforum.org
Subject: [SIPForum-discussion] a question about re-invite

Hi all,
my understanding of a SIP reinvite is that it modifies the media session. Is
it capable of modifying the address of the send too? for example, A is
talking to B, can A send a reinvite to B with C's address instead of its own
another example,A is talking to B,recorded as dialog1, C knows the
information of the dialog1,  can C sends a reinvite to B instead of the
dialog1, the dialog bewteen C and B has the same Call-ID, from-tag, to-tag
as dialog1?

Best Regards.

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