Tuesday, December 1, 2009

Introduction to Softphones

Softphone is a term derived from the Software Telephone and it is a program that enables Voice over Internet Protocol (VoIP). It allows making calls over the internet using a general purpose computer, Laptop or other computing devices like PDAs. Softphones are not using dedicated hardware for it, but it is configured to work with the computer’s external hardware devices like microphone, Web camera, and speakers. Usually the Softphones are behaved like the traditional phones and it may be implemented with a image of real phone with a panel and buttons to use for the interactions with the user.

The concept of the IP telephony has been available from number of years, but they were not popular as today. The world’s first VoIP softphone was VocalTec’s internet phone which was introduced in 1995. But the softphones have become widely spread today with the fast growth of internet usage on homes, businesses and government offices. Usually the Softphones services are provided by an Internet Telephony Service Provider. The types of calls can be categorized as PC to PC and PC to 3G phone calls. Usually the providers allows to make PC to PC calls with free of charge and PC to 3G phone calls and 3G phone to PC calls are charged.

Softphone use open standard IP signaling protocol – SIP (Session Initiation Protocol) that can be used in conjunction with the IP PBX in a enterprise. It converts video and audio to IP packets which contains the RTP data and vice versa in VoIP telephone service. So for the communication with a softphone, the protocols like SIP, SDP (Session Description Protocol) and RTP (Real Time Protocol) are used. In order to establish a successful communication, the both end points should have same communication protocols and at least a single common codec for both audio and video.
There are popular Internet Telephony Service Providers like Skype, Google Talk and Vonage who are provided their own softphones to install in the user’s PC. The problems with these softphones are they are not interoperable and we can’t place a direct call between them.

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