Sorry for the late reply. I am not sure what you mean by how. Vocaltec uses H.323 v2 so does Cisco. Standard call flow:
Setup w/ Fast start–
GKRCS is Gate Keeper Routed Call Signaling model, where all signaling flows go through the GK. This is to allow enhanced features through the GK.
If you have any further questions you can reply here and I will be notified.