Subject: [MEDIACTRL] Control Framework SDP Review - Issue 4

From: Chris Boulton <[email-masked]>
Date: Fri, 02 Oct 2009 14:46:13 +0100

Issue 4:

I also note that as far as I can tell, neither SDP nor the CFW SYNC
message provides any indication of whether a given endpoint thinks it's
a Control Client or a Control Server.  It seems this is supposed to be
implicit based on the directionality of the initial SIP INVITE request
that set up the call, but in some cases this can get confused in SIP
(notably given third-party call control), and I'm sure the results could
be odd, and hard to diagnose, if two clients or two servers accidentally
end up connected.  Perhaps this should be a property of the relevant
control package, rather than of CFW proper, but it seems like it should
be addressed.

[Chris] The 'roles' of the client and server are logical within the the Media Control Channel Framework and is not tied to the directionality of the SIP INVITE.  It is really up to the Control package to specify 'if' and 'when' messages can be sent (in the template).  The draft states:

'Consider the following simple example for session establishment
   between a Client and a Server (Note: Some lines in the examples are
   removed for clarity and brevity).  Note that the roles discussed are
   logical and can change during a session, if the Control Package
   allows.'

I will expand on this text and make it clearer to the reader that the roles are logical.  Is that acceptable?

-- 
Chris Boulton
CTO & Co-founder
NS-Technologies <http://www.ns-technologies.com>
m: +44.7876.476681

---

From: "Jonathan Lennox" <[email-masked]>
Date: Fri, 2 Oct 2009 11:18:26 -0400

I think the text is reasonably clear, but my concern is that for
packages where there *are* fairly strict role differences between the
client and the server, there's no easy way to detect the error when two
clients or two servers end up connected.  (I suppose if two clients end
up connected, you'll get error messages when an unexpected request is
received, but two servers might just sit there forever waiting for the
other guy to ask for something.)
 
As I said, though, since the roles are package-dependent, maybe this
should be a package attribute.  Presumably there could be packages which
are fully symmetric.

-- 
Jonathan Lennox
Vidyo, Inc
[email-masked]

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]]
On
> Behalf Of Chris Boulton
> Sent: Friday, October 02, 2009 9:46 AM
> To: [email-masked]
> Subject: [MEDIACTRL] Control Framework SDP Review - Issue 4
> 
> Issue 4:
> 
> [Chris] The 'roles' of the client and server are logical within the
the
> Media Control Channel Framework and is not tied to the directionality
> of the SIP INVITE.  It is really up to the Control package to specify
> 'if' and 'when' messages can be sent (in the template).  The draft
> states:
> 
> _______________________________________________
> MEDIACTRL mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/mediactrl
> Supplemental Web Site:
> http://www.standardstrack.com/ietf/mediactrl