This is a device allowing a user to make VoIP calls using session initiation protocol (SIP). SIP is a telecommunication technology developed as a fast, easy standard for delivering IP-based data, voice, and video communications.
Rates of the call shop are usually defined by the administrator, but the rate plans are managed in the main database of the billing system. All the rates are dependent on the charging policy; in case of a destination based billing rates are specified according to the area codes in the supported destinations.