been widely used in VoIP applications, such as the G.729.1 wideband codec introduced in 2006, Apple's FaceTime (using AAC-LD) introduced in 2010, the CELT codec introduced in 2011, the Opus codec introduced in 2012, and WhatsApp's voice calling feature introduced in 2015. Milestones 1966: Linear predictive coding (LPC) proposed by Fumitada Itakura of Nagoya University and Shuzo Saito of Nippon Telegraph and Telephone (NTT). 1973: Packet voice application by Danny Cohen. 1974: The Institute of Electrical and Electronics Engineers (IEEE) publishes a paper entitled "A Protocol for Packet Network Interconnection". 1974: Network Voice Protocol (NVP) tested over ARPANET in August 1974, carrying barely audible 16kpbs CVSD encoded voice. 1974: The first successful real-time conversation over ARPANET achieved using 2.4kpbs LPC, between Culler-Harrison Incorporated in Goleta, California, and MIT Lincoln Laboratory in Lexington, Massachusetts. 1977: Danny Cohen and Jon Postel of the USC Information Sciences Institute, and Vint Cerf of the Defense Advanced Research Projects Agency (DARPA), agree to separate IP from TCP, and create UDP for carrying real-time traffic. 1981: IPv4 is described in RFC 791. 1985: The National Science Foundation commissions the creation of NSFNET. 1985: Code-excited linear prediction (CELP), a type of LPC algorithm, developed by Manfred R. Schroeder and Bishnu S. Atal. 1986: Proposals from various standards organizations for Voice over ATM, in addition to commercial packet voice products from companies such as StrataCom 1991: Speak Freely, a voice-over-IP application, was released to the public domain. 1992: The Frame Relay Forum conducts development of standards for Voice over Frame Relay. 1992: InSoft Inc. announces and launches its desktop conferencing product Communique, which included VoIP and video. The company is credited with developing the first generation of commercial, US-based VoIP, Internet media streaming and real-time Internet telephony/collaborative software and standards that would provide the basis for the Real Time Streaming Protocol (RTSP) standard. 1993 Release of VocalChat, a commercial packet network PC voice communication software from VocalTec. 1994: MTALK, a freeware LAN VoIP application for Linux 1995: VocalTec releases Internet Phone commercial Internet phone software. Beginning in 1995, Intel, Microsoft and Radvision initiated standardization activities for VoIP communications system. 1996: ITU-T begins development of standards for the transmission and signaling of voice communications over Internet Protocol networks with the H.323 standard. US telecommunication companies petition the US Congress to ban Internet phone technology. G.729 speech codec introduced, using CELP (LPC) algorithm. 1997: Level 3 began development of its