first softswitch, a term they coined in 1998. 1999: The Session Initiation Protocol (SIP) specification RFC 2543 is released. Mark Spencer of Digium develops the first open source private branch exchange (PBX) software (Asterisk). A discrete cosine transform (DCT) variant called the modified discrete cosine transform (MDCT) is adopted for the Siren codec, used in the G.722.1 wideband audio coding standard. The MDCT is adapted into the LD-MDCT algorithm, used in the AAC-LD standard. 2001: INOC-DBA, first inter-provider SIP network deployed; also first voice network to reach all seven continents. 2003: First released in August 2003, Skype was the creation of Niklas Zennström and Janus Friis, in cooperation with four Estonian developers. It quickly became a popular program that helped democratise VoIP. 2004: Commercial VoIP service providers proliferate. 2006: G.729.1 wideband codec introduced, using MDCT and CELP (LPC) algorithms. 2007: VoIP device manufacturers and sellers boom in Asia, specifically in the Philippines where many families of overseas workers reside. 2009: SILK codec introduced, using LPC algorithm, and used for voice calling in Skype. 2010: Apple introduces FaceTime, which uses the LD-MDCT-based AAC-LD codec. 2011: Rise of WebRTC technology which allows VoIP directly in browsers. CELT codec introduced, using MDCT algorithm. 2012: Opus codec introduced, using MDCT and LPC algorithms. See also Audio over IP Communications Assistance For Law Enforcement Act Comparison of audio network protocols Comparison of VoIP software Differentiated services High bit rate audio video over Internet Protocol Integrated services Internet fax IP Multimedia Subsystem List of VoIP companies Mobile VoIP Network Voice Protocol RTP payload formats SIP trunking UNIStim Voice over LTE VoiceXML VoIP VPN VoIP recording Notes References External links Broadband Videotelephony Audio network protocols Office equipment