hey,
IMS 3GPP specification requires SIP integrity and confidentiality. You may see IPsec/IPsec security association on the device when it is communicating and/or registered with P-CSCF (uses SIP protocol).
Correct. While IPsec might be an option, all popular terminals support SIP-TLS. Our VoLTE implementation happily uses SIP-TLS + IPv6 only bearer without any IPsec.
With VoWiFi IPsec is used to establish a tunnel between UE (user equipment/phone) and mobile network operator packet core (EPDG node).
Correct, ePDG usecase is totally different and also applicable for more services than just voice.
-- tarko
