Network Voice Protocol
Encyclopedia
The Network Voice Protocol (NVP) was a pioneering computer
network protocol for transporting human speech over packetized communications networks. It was an early example of Voice over Internet Protocol technology.
NVP was first implemented in December 1973 by computer networking researcher Danny Cohen of the Information Sciences Institute
(ISI), University of Southern California
, with funding from ARPA
's Network Secure Communications (NSC) program. The project's stated goals as stated in IETF RFC 741, published 1977, were "to develop and demonstrate the feasibility of secure, high-quality, low-bandwidth, real-time, full-duplex (two-way) digital voice communications over packet-switched computer communications networks.... [and to] supply digitized speech which can be secured by existing encryption devices. The major goal of this research is to demonstrate a digital high-quality, low-bandwidth, secure voice handling capability as part of the general military requirement for worldwide secure voice communication."
NVP was used to send speech between distributed sites on the ARPANET
using several different voice-encoding techniques, including linear predictive coding
(LPC) and continuously variable slope delta modulation
(CVSD). Cooperating researchers included Steve Casner, Randy Cole, and Paul Raveling (ISI); Jim Forgie (Lincoln Laboratory
); Mike McCammon (Culler-Harrison); John Markel (Speech Communications Research Laboratory); and John Makhoul (Bolt, Beranek and Newman).
The protocol consisted of two distinct parts: control protocols and a data transport protocol. Control protocols included relatively rudimentary telephony
features such as indicating who wants to talk to whom; ring tones; negotiation of voice encoding; and call termination. Data messages contained encoded speech. For each encoding scheme (vocoder) a frame was defined as a packet containing the negotiated transmission interval of a number of digitized voice samples.
NVP was used by experimental Voice Funnel
equipment (circa February 1981), based on BBN Butterfly computers, as part of ongoing ARPA research into packetized audio. ARPA staff and contractors used the Voice Funnel, and related video facilities, to do three-way and four-way video conferencing among a handful of East and West Coast sites.
NVP was transported over the Internet Stream Protocol (ST) and a later version called Stream Protocol, version 2 (ST-II), both connection-oriented versions of the Internet Protocol
(IP) and which carried the IP protocol version 5. These protocols may be viewed as early experiments in quality of service
and connection-oriented network protocols such as Asynchronous Transfer Mode
(ATM).
Computer
A computer is a programmable machine designed to sequentially and automatically carry out a sequence of arithmetic or logical operations. The particular sequence of operations can be changed readily, allowing the computer to solve more than one kind of problem...
network protocol for transporting human speech over packetized communications networks. It was an early example of Voice over Internet Protocol technology.
NVP was first implemented in December 1973 by computer networking researcher Danny Cohen of the Information Sciences Institute
Information Sciences Institute
The Information Sciences Institute is a research and development unit of the University of Southern California's Viterbi School of Engineering which focuses on computer and communications technology and information processing...
(ISI), University of Southern California
University of Southern California
The University of Southern California is a private, not-for-profit, nonsectarian, research university located in Los Angeles, California, United States. USC was founded in 1880, making it California's oldest private research university...
, with funding from ARPA
ARPA
Arpa and ARPA may refer to:Arpa* Arpa River in Armenia* Areni, Armenia - formerly called Arpa* Arpi, Armenia, also called Arpa* Turkish for Akhurian River in Turkey and Armenia* Italian for harp, sometimes used in scoresARPA...
's Network Secure Communications (NSC) program. The project's stated goals as stated in IETF RFC 741, published 1977, were "to develop and demonstrate the feasibility of secure, high-quality, low-bandwidth, real-time, full-duplex (two-way) digital voice communications over packet-switched computer communications networks.... [and to] supply digitized speech which can be secured by existing encryption devices. The major goal of this research is to demonstrate a digital high-quality, low-bandwidth, secure voice handling capability as part of the general military requirement for worldwide secure voice communication."
NVP was used to send speech between distributed sites on the ARPANET
ARPANET
The Advanced Research Projects Agency Network , was the world's first operational packet switching network and the core network of a set that came to compose the global Internet...
using several different voice-encoding techniques, including linear predictive coding
Linear predictive coding
Linear predictive coding is a tool used mostly in audio signal processing and speech processing for representing the spectral envelope of a digital signal of speech in compressed form, using the information of a linear predictive model...
(LPC) and continuously variable slope delta modulation
Continuously variable slope delta modulation
Continuously variable slope delta modulation is a voice coding method. It is a delta modulation with variable step size Continuously variable slope delta modulation (CVSD or CVSDM) is a voice coding method. It is a delta modulation with variable step size Continuously variable slope delta...
(CVSD). Cooperating researchers included Steve Casner, Randy Cole, and Paul Raveling (ISI); Jim Forgie (Lincoln Laboratory
Lincoln Laboratory
MIT Lincoln Laboratory, located in Lexington, Massachusetts, is a United States Department of Defense research and development center chartered to apply advanced technology to problems of national security. Research and development activities focus on long-term technology development as well as...
); Mike McCammon (Culler-Harrison); John Markel (Speech Communications Research Laboratory); and John Makhoul (Bolt, Beranek and Newman).
The protocol consisted of two distinct parts: control protocols and a data transport protocol. Control protocols included relatively rudimentary telephony
Telephony
In telecommunications, telephony encompasses the general use of equipment to provide communication over distances, specifically by connecting telephones to each other....
features such as indicating who wants to talk to whom; ring tones; negotiation of voice encoding; and call termination. Data messages contained encoded speech. For each encoding scheme (vocoder) a frame was defined as a packet containing the negotiated transmission interval of a number of digitized voice samples.
NVP was used by experimental Voice Funnel
Voice Funnel
The Voice Funnel was an experimental high-speed interface between digitized speech streams and a packet-switching communications network, in particular the ARPANET. It was built in the time frame from 1979 to 1981. It may be viewed as an early Voice over IP voice and video telephone.The Voice...
equipment (circa February 1981), based on BBN Butterfly computers, as part of ongoing ARPA research into packetized audio. ARPA staff and contractors used the Voice Funnel, and related video facilities, to do three-way and four-way video conferencing among a handful of East and West Coast sites.
NVP was transported over the Internet Stream Protocol (ST) and a later version called Stream Protocol, version 2 (ST-II), both connection-oriented versions of the Internet Protocol
Internet Protocol
The Internet Protocol is the principal communications protocol used for relaying datagrams across an internetwork using the Internet Protocol Suite...
(IP) and which carried the IP protocol version 5. These protocols may be viewed as early experiments in quality of service
Quality of service
The quality of service refers to several related aspects of telephony and computer networks that allow the transport of traffic with special requirements...
and connection-oriented network protocols such as Asynchronous Transfer Mode
Asynchronous Transfer Mode
Asynchronous Transfer Mode is a standard switching technique designed to unify telecommunication and computer networks. It uses asynchronous time-division multiplexing, and it encodes data into small, fixed-sized cells. This differs from approaches such as the Internet Protocol or Ethernet that...
(ATM).