I like the simplicity of it but I have a couple of questions/comments.
1.  I didn't want to make an assumption on the interface between the
softswitch and the media server - it does not have to be SIP
2  At what point would the SDP/dialog data be updated in the initial UA ? In
your sequence would this be between 6. & 7. after a 183 or 200 is received ?

John

-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Dale Worley
Sent: Friday, May 20, 2005 3:20 PM
To: [email protected]
Subject: RE: [Sip-implementors] UPDATE or INVITE Replaces.


> From: Wainwright, John
>
> In particular I am thinking about UA-->softswitch-->Media Server 
> sequence which plays an announcement/collect a new DN from the UA 
> forwards this
info
> to the softswitch ( in an application specific way ) who then sends 
> out an INVITE to the collected DN and UPDATES the initial UA with this 
> dialog information in order to connect the call.  The initial UA would 
> be in an early media type state in effect waiting for the UPDATE from 
> the
softswitch.

That sequence seems excessively heavy-weight.  What seems easier to me is
this sequence:

1. INVITE from UA to Softswitch.

2. INVITE from Softswitch to Media Server.

3. Media Server sends 183 back to UA to set up early dialog.

4. User sends information, Media Server collects and processes it to
determine required action.

5. Media Server sends 302 response to Softswitch, with:

    Contact:
<where-ever-call-should-be-forwarded-to>;var=data;var=data;var=data

Where the "var=data" items are various bits of information provided to the
Softswitch by the Media Server.

6. Softswitch processes the "var=data" items, and forwards the INVITE to the
correct destination.

7. UA is ultimately connected to the destination, which establishes media
with the UA.

There doesn't seem to be any need to send an UPDATE, as long as the Media
Server is willing to retry the 183 a few times to allow for its
unreliability.

Dale

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