Re: Query regarding Owner IP in SDP field.

In North America, per the Telcordia specs, XFER is actually a subfeature of
CONF.  That is, they are the same feature, and the only way to know the
state of the call is to trace from the CONF controller.  From the
transferor/conferor one can tell what the state is by watching the state
transitions and watching the call leg setup/teardown.  For the
transferees/conferees, the only thing you will be able to tell is whether
they are connected or not.
 
Modifying the SDP mid-call can be any number of features, and is not
necessarily indicative of CONF/XFER.  Transition to fax, for instance, will
involve a change in the SDP.
 
As for the call flows document, there was never an updated version once the
one you reference expired.  I suggest that you acquire the correct feature
requirements documents for the region you are interested in and study the
feature flows.  Once you understand the feature in question, it will be
easier to trace through the H.248 messaging to determine what is going on.
 
Kevin


  _____  

From: [email protected] [mailto:[email protected]] On Behalf Of
nupur gupta
Sent: Tuesday, December 16, 2008 6:16 AM
To: [email protected]
Subject: Re: [Megaco] Query regarding Owner IP in SDP field.


Hi Kevin,

Thanks for the reply.

Actually the point is that if a person is tapping the messages exchanged
between MG and MGC (unaware of the Call processing requirements outlined at
MGC), then just by looking at these messages what is the way of
differentiating between Call Transfer and Call Conference?

I understand that whenever a MODIFY request with SDP in remote desciptor is
recieved (for a Ephemeral termination whose Remote is alreday set) then
either Transfer or Conference is taking place, but still not do know which
service exactly and how to find out and differentiate.

Between MG2 and MGC (as per the call flows), using Notify event this can be
done:
      a)Flash followed by On Hook for Transfer
      b)Flash follwoed by Flash for Conference
But how between MG1 and MGC or MG3 and MGC?

Also, if anyone has the link of latest draft for MEGACO Call Flows, then
please share with me the same. 

Thanks and Regards,
Nupur Gupta
Software Engineer
Aricent Technologies ltd.




On Mon, Dec 15, 2008 at 6:10 PM, Kevin Boyle <[email protected]> wrote:


Last I checked, the draft you reference has been expired for 3.5 years.  I
wouldn't put much stock in expired drafts.

As for conference vs. transfer, there are specific call processing
requirements for each outlined by the various regional SDOs.  These call
processing requirements are carried out, and billed for, by the MGC.  Since
the MG should just do what it is commanded by the MGC and has little to no
call processing knowledge, why does it need to know whether a particular
manipulation is any particular feature?

Kevin


-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of
nupur gupta
Sent: Monday, December 15, 2008 5:50 AM
To: [email protected]
Subject: [Megaco] Query regarding Owner IP in SDP field.

Hi All,

Referring to the call flow examples, for Call Transfer and Call Conference,
given in the following:
http://tools.ietf.org/html/draft-ietf-megaco-callflows-04

As far as my understanding goes, the only way to differentiate between Call
Transfer and Call Conference at MG1/MG3 is to analyze the Owner IP field in
SDP part of MODIFY message (Step 37 and step 39, Sec 8.1).
If the owner IP received in SDP in Modify is same as previously received
owner IP, then it is Call Conference else it Call Transfer.

How ever, as per RFC3525, the owner IP field is optional and hence not
necessarily present in the SDP part.
So what is other way (and may be more concrete approach) to distinguish
between Call Transfer and Call conference at MG1 and MG3?

Thanks and Regards,
Nupur Gupta,
Software Engineer,
Aricent technologies ltd.

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