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.