Network Voice Protocol
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The Network Voice Protocol (NVP) was a pioneering
computer A computer is a machine that can be programmed to Execution (computing), carry out sequences of arithmetic or logical operations (computation) automatically. Modern digital electronic computers can perform generic sets of operations known as C ...
network protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any kind of variation of a physical quantity. The protocol defines the rules, syntax, semantics and synchroniza ...
for transporting human
speech Speech is a human vocal communication using language. Each language uses Phonetics, phonetic combinations of vowel and consonant sounds that form the sound of its words (that is, all English words sound different from all French words, even if ...
over
packet Packet may refer to: * A small container or pouch ** Packet (container), a small single use container ** Cigarette packet ** Sugar packet * Network packet, a formatted unit of data carried by a packet-mode computer network * Packet radio, a form ...
ized communications networks. It was an early example of
Voice over Internet Protocol Voice over Internet Protocol (VoIP), also called IP telephony, is a method and group of technologies for the delivery of voice communications and multimedia sessions over Internet Protocol (IP) networks, such as the Internet. The terms Internet t ...
technology.


History

NVP was first defined and implemented in 1974, with definition led by the “Speech” project at ISI, the USC Information Sciences Institute following initial work begun in 1973. ISI leadership was by Danny Cohen of the
Information Sciences Institute The USC Information Sciences Institute (ISI) is a component of the University of Southern California (USC) Viterbi School of Engineering, and specializes in research and development in information processing, computing, and communications techno ...
(ISI),
University of Southern California The University of Southern California (USC, SC, or Southern Cal) is a Private university, private research university in Los Angeles, California, United States. Founded in 1880 by Robert M. Widney, it is the oldest private research university in C ...
, with funding from ARPA's Network Secure Communications (NSC) program. The project's stated goals 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... nd tosupply 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’s first demonstration was in August 1974 between the groups at ISI and MIT Lincoln Labs. That was history’s first “phone call” using a computer network. It was partly enabled by users of vocoders custom-built by BB&N, Bolt Beranek, and Newman. Work as a whole involved many other researchers nationally. Necessary subnet (IMP-to-IMP) changes for real-time packet forwarding were discussed at ISI in March 1974, chaired by Bob Kahn, DARPA’s program director for the speech project. At the end of the meeting, he summarized actions and directed BB&N to make the required subnet updates. NVP was used to send speech between distributed sites on the
ARPANET The Advanced Research Projects Agency Network (ARPANET) was the first wide-area packet-switched network with distributed control and one of the first networks to implement the TCP/IP protocol suite. Both technologies became the technical fou ...
using several different voice-encoding techniques, including
linear predictive coding Linear predictive coding (LPC) is a method 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 (CVSD or CVSDM) is a voice coding method. It is a delta modulation with variable step size (i.e., special case of adaptive delta modulation), first proposed by Greefkes and Riemens in 1970. CVSD encodes ...
(CVSD). Cooperating researchers included Steve Casner, Randy Cole, and Paul Raveling (ISI); Jim Forgie (
Lincoln Laboratory The MIT Lincoln Laboratory, located in Lexington, Massachusetts, is a United States Department of Defense federally funded research and development center chartered to apply advanced technology to problems of national security. Research and dev ...
); Mike McCammon (Culler-Harrison); John Markel (Speech Communications Research Laboratory);
John Makhoul John Makhoul is a Lebanese-American computer scientist who works in the field of speech and language processing. Dr. Makhoul's work on linear predictive coding was used in the establishment of the Network Voice Protocol, which enabled the trans ...
(
Bolt, Beranek and Newman Raytheon BBN (originally Bolt Beranek and Newman Inc.) is an American research and development company, based next to Fresh Pond in Cambridge, Massachusetts, United States. In 1966, the Franklin Institute awarded the firm the Frank P. Brown ...
), and Rod McGuire and
Philip Rubin Philip E. Rubin (born May 22, 1949) is an American cognitive scientist, technologist, and science administrator known for raising the visibility of behavioral and cognitive science, neuroscience, and ethical issues related to science, techn ...
(
Haskins Laboratories Haskins Laboratories, Inc. is an independent 501(c) non-profit corporation, founded in 1935 and located in New Haven, Connecticut, since 1970. Haskins has formal affiliation agreements with both Yale University and the University of Connecticut; ...
). NVP was used by experimental
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 ...
equipment (circa February 1981), based on
BBN Butterfly The BBN Butterfly was a massively parallel computer built by Bolt, Beranek and Newman in the 1980s. It was named for the "butterfly" multi-stage switching network around which it was built. Each machine had up to 512 CPUs, each with local memory, ...
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 US East and West Coast sites. Credit also is due to Dave Retz and his group at the UC Santa Barbara Speech Communication Laboratory. ISI used his operating system, ELF, for the early development of speech networking, including extension to speech conferencing.


Protocol

The protocol consisted of two distinct parts: control protocols and a data transport protocol. Control protocols included relatively rudimentary
telephony Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is i ...
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 transported over the
Internet Stream Protocol The Internet Stream Protocol (ST) is a family of experimental protocols first defined in Internet Experiment Note IEN-119 in 1979, and later substantially revised in RFC 1190 (ST-II) and RFC 1819 (ST2+). The protocol uses the version number 5 in ...
(ST) and a later version called Stream Protocol, version 2 (ST-II), both connection-oriented versions of the
Internet Protocol The Internet Protocol (IP) is the network layer communications protocol in the Internet protocol suite for relaying datagrams across network boundaries. Its routing function enables internetworking, and essentially establishes the Internet. IP h ...
(IP) and which carried the IP protocol version 5. These protocols may be viewed as early experiments in
quality of service Quality of service (QoS) is the description or measurement of the overall performance of a service, such as a telephony or computer network, or a cloud computing service, particularly the performance seen by the users of the network. To quantitat ...
and connection-oriented network protocols such as
Asynchronous Transfer Mode Asynchronous Transfer Mode (ATM) is a telecommunications standard defined by American National Standards Institute (ANSI) and ITU-T (formerly CCITT) for digital transmission of multiple types of traffic. ATM was developed to meet the needs of ...
(ATM).


References


External links

*{{Commons category inline VoIP protocols Audio network protocols