Subject: [Sipping] VoiceXML Dialog Servers

From: Michael Hammer <[email-masked]>
Date: Thu, 13 Sep 2001 16:40:17 -0400

Jonathan,

Expires:  Feb 2001 ??  Thought this just came out. :-)

The description on page 7 implies that there can be many servers running 
VSML interpreters simultaneously under the feature interaction control of 
the application server.  In 4.2 the effect of the BYE seems to be local to 
the application server. (?)  Shouldn't this also indicate that the 
application server has the responsibility to send BYE to all other servers 
related to that caller, so they can exit abnormally from any active or 
suspended scripts?  Cleaning up these stateful machines could avoid 
accumulation of hung scripts.

Second, when suspending the script, it appears that the script has the job 
of deciding when to "finish its sentence" (at an appropriate checkpoint) 
and reply to the re-Invite which suspends it, prior to the application 
server giving the go-ahead to the second server.  Are there any guidelines 
to how verbose an server can be?  Is there a way to interrupt one that is?

Third, there is no Security section to this document.  It appears to be 
anticipated that the dialog server will download scripts from the 
application server which is trusted.  Is it conceivable that the scripts 
are from third-party sources, even the user?  Is that out of scope for this 
document?

Mike 

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---

From: Paul Kyzivat <[email-masked]>
Date: Fri, 14 Sep 2001 11:19:01 -0400

Michael,

I will take a crack at your first question:

> accumulation of hung scripts.

The AS is acting as a 3pcc, coordinating call control for multiple
related calls. It receives the BYE from any of them, and is responsible
for doing the right thing, whatever that might be. In the example, the
AS has preempted the call to the stock service in order to give focus to
the notification service. When the AS receives a BYE from
thenotification service , it knows that the right thing to do is resume
the stock service. However, if it received a BYE from the user, the
right thing to do would be to send BYEs to both the stock service and
the notification service.

	Paul

P.S. the referenced document wasn't clear in the original message.
I learned offline that it is draft-rosenberg-sip-vxml-00.txt