Internet telephony refers to communication services – voice, facsimile, and/or voice-messaging applications –that are transported via the Internet, rather than the Public Switched Telephone Network (PSTN). The basic steps involved in originating an Internet telephone call are conversion of the analog voice signal to digital format and compression/translation of the signal into Internet protocol (IP) packets for transmission over the Internet; the process is reversed at the receiving end.

It is becoming increasingly common for telecommunications providers to use VoIP technology over dedicated and public IP networks to connect switching stations and to interconnect with other telephone networks. It will upgrade their existing systems while embracing Internet technologies such as the Web, email, instant messaging , presence, and video conferencing. It will also allow existing VoIP systems to interface with conventional PSTN and mobile phone networks.

Dual mode telephones are expected to make VoIP more popular. They allow seamless handover between a cellular network and a Wi-Fi enable network. These phones have SIP (Session Initiation Protocol) clients built into the firmware. These enables users to make calls when they move from an outside cellular service to an internal Wi-Fi network. These bundling means the user no longer have to carry a desktop phone and a cell phone which reduce their cost.