RFC 741 (rfc741) - Page 1 of 30
Specifications for the Network Voice Protocol (NVP)
Alternative Format: Original Text Document
NWG/RFC 741 DC 22 Nov 77 42444
SPECIFICATIONS FOR THE
NETWORK VOICE PROTOCOL (NVP)
and
Appendix 1: The Definition of Tables-Set-#1 (for LPC)
Appendix 2: Implementation Recommendations
NSC NOTE 68
(Revision of NSC Notes 26, 40, and 43)
Danny Cohen, ISI
January 29, 1976
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
CONTENTS
PREFACE iii
ACKNOWLEDGMENTS iv
INTRODUCTION 2
THE CONTROL PROTOCOL 2
Summary of the CONTROL Messages 3
Definition of the CONTROL Messages 4
Definition of the and
Negotiation Tables 8
On RENEGOTIATION 10
The Header of Data Messages 10
THE LPC DATA PROTOCOL 13
EXAMPLES FOR THE CONTROL PROTOCOL 15
APPENDIX 1: THE DEFINITION OF TABLES-SET-#1 18
General Comments 20
Comments on the PITCH Table 20
Comments on the GAIN Table 21
Comments on the INDEX7 Table 21
Comments on the INDEX6 Table 21
Comments on the INDEX5 Table 21
The PITCH Table 22
The GAIN Table 24
The INDEX7 Table 25
The INDEX6 Table 26
The INDEX5 Table 27
APPENDIX 2: IMPLEMENTATION RECOMMENDATIONS 28
REFERENCES 30
Cohen [Page ii]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
PREFACE
The major objective of ARPA's Network Secure Communications (NSC)
project is 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. This kind of communication is a very high priority
military goal for all levels of command and control activities.
ARPA's NSC projrct will 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. The development at ISI of the
Network Voice Protocol described herein is an important part of the
total effort.
Cohen [Page iii]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
ACKNOWLEDGMENTS
The Network Voice Protocol (NVP), implemented first in December 1973,
and has been in use since then for local and transnet real-time voice
communication over the ARPANET at the following sites:
o Information Sciences Institute, for LPC and CVSD, with a
PDP-11/45 and an SPS-41.
o Lincoln Laboratory, for LPC and CVSD, with a TX2 and the
Lincoln FDP, and with a PDP-11/45 and the LDVT.
o Culler-Harrison, Inc., for LPC, with the Culler-Harrison
MP32A and AP-90.
o Stanford Research Institute, for LPC, with a PDP-11/40 and an
SPS-41.
The NVP's success in bridging the differences between the above
systems is due mainly to the cooperation of many people in the
ARPA-NSC community, including Jim Forgie (Lincoln Laboratory), Mike
McCammon (Culler-Harrison), Steve Casner (ISI) and Paul Raveling
(ISI), who participated heavily in the definition of the control
protocol; and John Markel (Speech Communications Research
Laboratory), John Makhoul (Bolt Beranek & Newman, Inc.) and Randy
Cole (ISI), who participated in the definition of the data protocol.
Many other people have contributed to the NVP-based effort, in both
software and hardware support.
Cohen [Page iv]
NWG/RFC 741 DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)
1. INTRODUCTION
Currently, computer communication networks are designed for data
transfer. Since there is a growing need for communication of
real-time interactive voice over computer networks, new communication
discipline must be developed. The current HOST-to-HOST protocol of
the ARPANET, which was designed (and optimized) for data transfer,
was found unsuitable for real-time network voice communication.
Therefore this Network Voice Protocol (NVP) was designed and
implemented.
Important design objectives of the NVP are:
- Recovery of loss of any message without catastrophic effects.
Therefore all answers have to be unambiguous, in the sense that
it must be clear to which inquiry a reply refers.
- Design such that no system can tie up the resources of another
system unnecessarily.
- Avoidance of end-to-end retransmission.
- Separation of control signals from data traffic.
- Separation of vocoding-dependent parts from vocoding-independent
parts.
- Adaptation to the dynamic network performance.
- Optimal performance, i.e. guaranteed required bandwidth, and
minimized maximum delay.
- Independence from lower level protocols.
The protocol consists of two parts:
(1) The control protocol,
(2) The data protocol.
Control messages are sent as controlled (TYPE 0/0) messages, and data
messages may be sent as either controlled (TYPE 0/0) or uncontrolled
(TYPE 0/3) messages (see BBN Report 1822 for definition of
MESSAGE-TYPE).
Throughout this document a "word" means a "16-bit quantity".
Cohen
