@JasGot said in Wi-Fi calling?:
@Pete-S said in Wi-Fi calling?:
I did some more research and it turns out that WiFi calling is using some familiar protocols but it's not the same as VoIP using SIP/RTP.
Actually another name for Wi-Fi Calling is the more official VoWiFi.
It's using a protocol called GAN (Generic Access Network) that is based on IMS, IPsec and ePDG. And IMS is using SIP for signaling.
Basically it's a way of sending the same packets that would go over the cell network over internet instead. It uses the SIM card for security and authentication. It's data is encapsulated in an IPsec tunnel - which is why it only works if IPsec ports and packets are allowed in the firewall.
Related technology that works in a very similar way is VoLTE, which is Voice over the 4G/LTE network.
Did you happen to learn if it uses the SS7 network? It would be very intersting if VoWiFi avoided the SS7.
Why do you care? That is a back-haul PSTN network between carriers that you have no access or say about.
But the correct answer is, "not while the call is a 'Vo' (Voice over) anything." At that point it is traveling over data networks. Which, by definition, cannot be switched telephone signalling.