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). With VoWiFi IPsec is used to establish a tunnel between UE (user equipment/phone) and mobile network operator packet core (EPDG node). So they're two different use cases.
More info: [0] https://en.wikipedia.org/wiki/IMS_security#IMS_Access_Security_for_SIP [1] 3G Security: 3GPP TS 33.203 - https://www.3gpp.org/DynaReport/33203.htm [2] Access to the 3GPP Evolved Packet Core (EPC) via non-3GPP access networks (VoWiFi) / 3GPP TS24.302- www.3gpp.org/dynareport/24302.htm On Thu, Nov 8, 2018 at 2:15 AM Tarko Tikan <ta...@lanparty.ee> wrote: > > hey, > > > This might be confusing VoLTE with VoWiFI. The latter will use IPSEC. > > Correct. What probably happened is that together with activating VoLTE, > VoWIFI was also activated on the device. Makes sense as VoLTE users are > typically moved to IMS environment. > > -- > tarko -- Yury.