1. Is PSTN for 2G and 3G calls and possibly 4G VoLTE calls in the early days and VoIP would be calls made through the PDN? 2. I am a little lost of after the user is authenticated on the IMS and the SIP connection is made at the SCSCF, how does the PGW know to forward User A call traffic to User B. Does the IMS use the SCSCF to tell the Media Gateway to tell the PGW to allocate radio resources for the VoLTE call?