Softphone

A softphone is a software program for making telephone calls over the Internet using a general purpose computer, rather than using dedicated hardware. Often a softphone is designed to behave like a traditional telephone, sometimes appearing as an image of a phone, with a display panel and buttons with which the user can interact. A softphone is usually used with a headset connected to the sound card of the PC, or with a USB phone.[1]

Applications

See Comparison of VoIP software

Communication protocols

To communicate, both end-points must support the same Voice-over-IP protocol, and at least one common audio codec.

Many service providers use the Session Initiation Protocol (SIP) standardized by the Internet Engineering Task Force (IETF). Skype, a popular service, uses proprietary protocols, and Google Talk leverages the Extensible Messaging and Presence Protocol (XMPP).

Some softphones also support the Inter-Asterisk eXchange protocol (IAX), a protocol supported by the open-source software application Asterisk.

Features

A typical softphone has all standard telephony features (DND, Mute, DTMF, Flash, Hold, Transfer etc.) and often additional features typical for online messaging, such as user presence indication, video, wide-band audio. Softphones provide a variety of audio codecs, a typical minimum set is G.711 and G.729.

Requirements

To make voice calls via the Internet, a user typically requires the following:

See also

References