In the broader world of tech, is the backbone of services like VoLTE (Voice over LTE) and VoWiFi (Wi-Fi Calling). It is the "handshake" that tells the network who is calling whom and when the conversation starts or ends.
It allows you to use your "office number" or "fixed line" from anywhere in the world using a mobile app. 2. Why People Use It
You don't "download" the SIP protocol itself; instead, you download a (a softphone app) and configure it with your Mobilis account details.
You can receive calls made to your office landline directly on your smartphone. 3. How to "Download" and Set It Up
Popular third-party apps include Zoiper , Linphone , or GS Wave , which are available on the Google Play Store and Apple App Store.