Subject: [MEDIACTRL] draft-ietf-mediactrl-sip-control-framework questions

From: "Henry Lum" <[email-masked]>
Date: Wed, 6 Jan 2010 13:51:59 -0800

Hi,

I am new to this set of drafts for media control, and I have and some
general questions on the latest draft (11) of the framework:

-          Section 3 mentions that the control connections are
orthogonal to media sessions, does that mean a control server can
control call legs that are not negotiated with application/cfw? In other
words, a control client can use dedicated control channel to control all
other calls that the control client sends to the control server.

-          If the control client or server detects that the underlying
control channel has failed (let's say the TCP connection has dropped for
whatever reason), does the SIP dialog implicitly terminate? Can the
client with active connection reestablish the connection using the same
TCP parameters negotiated in the SDP? Does it require an new
offer/answer exchange to re-establish the TCP connection?

-          Is the application/cfw MIME type required to be placed in the
Content-Type of the SIP messages? The examples in the draft use
application/sdp in the content type, then what is this new MIME type
for? 

-          Section 4.1 says that you cannot define more than one control
channel with multiple m= lines. Does that mean if I need to create
redundant control channels I must use multiple SIP dialogs?

-          If control server sees multiple m= lines, then should it
reject the extra ones with port set to "0" or should control server
terminate the dialog?

-          I'm a bit confused with the general usage of REPORT method,
is the only usage for REPORT is when CONTROL method takes a long time to
respond? I see that the framework CONTROL response can embed content in
the response message itself, rather than needing to use REPORT to embed
content. Would there be other non-timeout cases where a package require
that REPORT to be used? 

-          If an asynchronous operation takes a long time to complete,
wouldn't it be better for the control server to use a separate CONTROL
message instead of relying on maintaining a sequence of REPORT messages
to report the status of the original request?

I'll have more questions about the IVR and mixer package after I read
through them.

Thanks!
Henry

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