[SIPForum-discussion] Difference between Update and Re-Invite

[Sam]

Hello,

The Session Initiation Protocol (SIP)  defines the INVITE method for the
initiation and modification of sessions.  However, this
   method actually affects two important pieces of state.  It impacts the
session (the media streams SIP sets up) and also the dialog (the
   state that SIP itself defines).  While this is reasonable in many cases,
there are important scenarios in which this coupling causes
   complications.

   The primary difficulty is when aspects of the session need to be modified
before the initial INVITE has been answered.  An example of
   this situation is "early media", a condition where the session is
established, for the purpose of conveying progress of the call, but
   before the INVITE itself is accepted.  It is important that either caller
or callee be able to modify the characteristics of that
   session (putting the early media on hold, for example), before the call
is answered.  However, a re-INVITE cannot be used for this
   purpose, because the re-INVITE has an impact on the state of the dialog,
in addition to the session.

   As a result, a solution is needed that allows the caller or callee to
provide updated session information before a final response to the
   initial INVITE request is generated.  The UPDATE method, defined here,
fulfills that need.  It can be sent by a UA within a dialog
   (early or confirmed) to update session parameters without impacting the
dialog state itself.



Regards
Sam


On Mon, Aug 9, 2010 at 12:07 PM, Deepak raj Siddharthan <
deepakraj.siddhu at gmail.com> wrote:

> Hello all,
>
> Can any one tell me the difference betweent the "Update" method and
> "Re-Invite" ?
>
> Thanks in advance
>
> Best Regards,
> Deepak
>
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