[SIPForum-discussion] Need clarification on Re-Invite ..

[Sriram Subramanian]

Hello,
        Please find my answers inline

A calls B. B is ringing. Now, I want to simulate a scenario wherein  A sends
Re-Invite to B and B responds accordingly. What actually makes A send
Re-invite to B before the session is established(do we need any extra
configurations to simulate this scenario). Any real time scenarios in this
regard is much helpful.

Sriram:In The above scenario said you cannot send a Re-Invite as the intial
session has syill not been setup.You can only send an UPDATE .As said by one
of the members a classic example can be an IVR (Early Media Negotiation) for
the UPDATE.

And what’s the exact difference between UPDATE and RE-INVITE. I had read
somewhere UPDATE is sent before the session is established whereas Re-Invite
is sent after the session is established.

Sriram:Exact difference is Re-INVITE takes a bit longer time and can only be
sent after an initial session has been established wheras an UPDATE can be
sent before the initial INVITE TRANSACTION has been completed and is also a
much faster mechanism for Modifying the session parameters.Moreover the
Update originator should have reserved the QOS parameters before it sends an
UPDATE out.Re-INVITE can be used for supplementary services like Call Hold
,Call Transfer(Invite based),Conference(INVITE based) etc.
Regards,
Sriram
Senior Engineer ,CARC
On Mon, Apr 26, 2010 at 12:20 PM, Murali Vuppandla <mvuppand at cisco.com>wrote:

>  There are two SIP  subscribers A and B configured with G729 codec.
>
>
>
> A calls B. B is ringing. Now, I want to simulate a scenario wherein  A
> sends Re-Invite to B and B responds accordingly. What actually makes A send
> Re-invite to B before the session is established(do we need any extra
> configurations to simulate this scenario). Any real time scenarios in this
> regard is much helpful.
>
>
>
> And what’s the exact difference between UPDATE and RE-INVITE. I had read
> somewhere UPDATE is sent before the session is established whereas Re-Invite
> is sent after the session is established.
>
>
>
> Please clarify me on this.
>
>
>
> Regards,
>
> Murali.
>
>
>
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