Nist SIP on J2ME CDC environment ?

Thank you for your answers. 
I looked at JSR-180 and the implementation of Nokia, but before I invest more 
time, want to be clear about the questions on my head. 

I found a SIP presentation of “JAIN Technology Day
Munich, Germany“ from Emil Ivov. Hier is the URL:
http://www.isty.uvsq.fr/~hanszech/sipcom/docs/SIP.pdf

Where two slides show "Sip Communicator Project" uses in a dynamic environment 
like OSGi, the JAIN-SIP implementation (NIST-SIP) for J2ME CDC but JSR-180 for 
CLDC.

I would like to know: 
What are the advantages and disadvantages to operate with implementations of  
JAIN-SIP or JSR-180 on top of  GCF (Generic Connection Framework) in OSGi 
environment?

Detailed answers would be very helpful, also from the participants of Sip-
Communicator.

cincinak