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+NWG/RFC 741 DC 22 Nov 77 42444
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+ SPECIFICATIONS FOR THE
+
+ NETWORK VOICE PROTOCOL (NVP)
+
+ and
+
+ Appendix 1: The Definition of Tables-Set-#1 (for LPC)
+
+ Appendix 2: Implementation Recommendations
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+ 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 <WHAT> and <HOW>
+ 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
+
+
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+
+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.
+
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+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.
+
+
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+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 [Page 1]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ 2. THE CONTROL PROTOCOL
+
+ Throughout this document the 12-bit MESSAGE-ID (see BBN Report 1822)
+ is referred to as LINK (its 8 MSBs) and SUB-LINK (its 4 LSBs).
+
+ The control protocol starts with an initial connection phase on link
+ 377 and continues on other links assigned at run time.
+
+ Four links are used for each voice communication:
+
+ Link L will be used for control, from CALLER to ANSWERER.
+ Link K will be used for control, from ANSWERER to CALLER.
+ Link L+1 will be used for data, from CALLER to ANSWERER.
+ Link K+1 will be used for data, from ANSWERER to CALLER.
+
+ Both L and K should be between 340 and 375 (octal). L and K need not
+ differ.
+
+ The first message (CALLER to ANSWERER) on link 377 indicates which
+ user wants to talk to whom and specifies K. As a response (on K), the
+ ANSWERER either refuses the call or accepts it and assigns L.
+
+ The CALLER then calls again (this time on link L). The ANSWERER
+ initiates a negotiation session to verify the compatibility of the
+ two parties.
+
+ The negotiation consists of suggestions put forth by one of the
+ parties, which are either accepted or rejected by the other party.
+ The suggesting party in the negotiation is called the NEGOTIATION
+ MASTER. The other party is called the NEGOTIATION SLAVE. Usually the
+ ANSWERER is the negotiation master, unless agreed otherwise by the
+ method described later.
+
+ If the negotiation fails, either party may terminate the call by
+ sending a "GOODBYE". If the negotiation is successfully ended, the
+ ANSWERER rings bells to draw human attention and sends "RINGING" to
+ the CALLER. When the call is answered (by a human), a "READY" is sent
+ to the CALLER and the data starts flowing (on L+1 and K+1). However,
+ a "READY" can be sent without a preceeding "RINGING".
+
+ This bell ringing occurs only after the initial call (not after
+ renegotiation).
+
+ The assignment of L and K cannot be changed after the initial
+ connection phase.
+
+ Only one control message can be sent in a network-message. Extra bits
+ needed to fill the network-message are ignored.
+
+
+
+
+Cohen [Page 2]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ The length of control messages should never exceed a single-packet
+ (i.e., 1,007 data bits).
+
+ Control messages not recognized by their receiver should be ignored
+ and should not cause any error condition resuting in termination of
+ the connection. These messages may result from differences in
+ implementation level between systems.
+
+ SUMMARY OF THE CONTROL MESSAGES
+
+ #1 "1,<WHO>,<WHOM>,K"
+
+ #2 "2,<CODE>" or only "2"
+
+ #3 "3,<WHAT>,<N>,<HOW(1),...HOW(N)>"
+
+ #4 "4,<WHAT>,<HOW>"
+
+ #5 "5,<WHAT>,<HOW>" or only "5,<WHAT>"
+
+ #6 "6,L" or only "6"
+
+ #7 "7"
+
+ #8 "8"
+
+ #9 "9"
+
+ #10 "10,<ID>"
+
+ #11 "11,<ID>"
+
+ #12 "12,<IM>"
+
+ #13 "13,<YM>,<OK>"
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Cohen [Page 3]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ DEFINITION OF THE CONTROL MESSAGES
+
+ #1 CALLING (on 377 and L)
+
+ This call is issued first on link 377 and later on link L. Its
+ format is "1,<WHO>,<WHOM>,K", where <WHO> and <WHOM> are words
+ which identify respectively the calling party and the party
+ that is being called, and K is as defined above. The format of
+ the <WHO> and <WHOM> is:
+
+ (HHIIIIIIXXXXXXXX)
+
+ where HH are 2 bits identifying the HOST, followed by 6 bits
+ identifying the IMP, followed by 8 bits identifying the
+ extension (needed because there may be more than one
+ communication unit on the same HOST).
+
+ The system which sends this message is defined as the CALLER,
+ and the other system is defined as the ANSWERER.
+
+ #2 GOODBYE (TERMINATION, on L or K)
+
+ This message has the purpose of terminating calls at any stage.
+
+ ICP can be terminated (on K) either negatively by sending
+ either a single word "2" ("GOODBYE") or the two words
+ "2,<CODE>", or positively by sending the two words "6,L", as
+ described later.
+
+ After the initial connection phase, calls can be terminated by
+ either the CALLER (on L) or the ANSWERER (on K). This
+ termination has two words: "2,<CODE>", where <CODE> is the
+ reason for the termination, as specified here:
+
+ 0. Other than the following.
+
+ 1. I am busy.
+
+ 2. I am not authorized to talk with you.
+
+ 3. Request of my user.
+
+ 4. We believe you are down.
+
+ 5. Systems incompatibility (NEGOTIATION failure).
+
+ 6. We have problems.
+
+ 7. I am in a conference now.
+
+
+
+Cohen [Page 4]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ 8. You made a protocol error.
+
+ #3 NEGOTIATION INQUIRY (on L or K)
+
+ Sent by the NEGOTIATION MASTER for compatibility verification.
+ The format is:
+
+ "3,<WHAT>,<LIST-LENGTH>,<HOW-LIST>", meaning
+
+ "CAN-YOU-DO,<WHAT>,<LIST-LENGTH>,<HOW-LIST>".
+
+ The <HOW-LIST> is a list of pointers into agreed-upon tables,
+ as shown below.
+
+ #4 POSITIVE NEGOTIATION RESPONSE (on L or K)
+
+ Sent by the NEGOTIATION SLAVE in response to a NEGOTIATION
+ INQUIRY. The format is:
+
+ "4,<WHAT>,<HOW>", meaning: "I-CAN-DO,<WHAT>,<HOW>".
+
+ #5 NEGATIVE NEGOTIATION RESPONSE (on L or K)
+
+ Sent by the NEGOTIATION SLAVE in response to a NEGOTIATION
+ INQUIRY. The format is either:
+
+ "5,<WHAT>,0", meaning "I-CAN'T-DO-<WHAT>-IN-ANY-OF-THESE-WAYS",
+
+ or: "5,<WHAT>,N", meaning inability to accept any of the
+ options offered in the INQUIRY, but using "N" as a suggestion
+ to the ANSWERER about another possibility. Examples are
+ presented later in this report.
+
+ #6 READY (on L or K)
+
+ Sent by either party to indicate readiness to accept data. Its
+ format is "6,L" in the reply to the initial call, and "6"
+ thereafter.
+
+ #7 NOT READY (on L or K)
+
+ Sent by either party to indicate unreadiness to accept data. It
+ is always a single word: "7".
+
+ #8 INQUIRY (on L or K)
+
+ Sent by either party to inquire about the status of the other.
+ It is always a single word: "8". It is answered by #6, #7, or
+ #9.
+
+
+
+Cohen [Page 5]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ #9 RINGING (on K)
+
+ Sent by the ANSWERER after the negotiations have been
+ successfully terminated and human permission is needed to
+ proceed further. The ringing will continue for 10 seconds, and
+ then stop, UNLESS a #8 is received. This message is always a
+ single word: "9".
+
+ #10 ECHO REQUEST (on L or K)
+
+ Sent by whichever party is interested in measuring the network
+ delays. Its only purpose is to be echoed immediately. The
+ format is "10,<ID>", where <ID> is any word used to identify
+ the ECHO.
+
+ #11 ECHO (on L or K)
+
+ Sent in response to ECHO REQUEST. The format is "11,<ID>",
+ where <ID> is the word specified by #10. The implementation of
+ this feature is not compulsory, and no connection should be
+ terminated due to lack of response to ECHO-REQUEST.
+
+ #12 RENEGOTIATION REQUEST (on L or K)
+
+ Can be sent by either party at ANY stage after LINKS are agreed
+ upon. This message consists of the two words "12,<IM>". If the
+ word <IM> (for I MASTER) is non-zero, the sender of this
+ message requests to be the NEGOTIATION MASTER. If it is zero,
+ the receiver of this message is requested to be the NEGOTIATION
+ MASTER. Renegotiation is described later.
+
+ #13 RENEGOTIATION APPROVAL (on L or K)
+
+ This message may be sent by either party in response to
+ RENEGOTIATION REQUEST. It consists of the three words
+ "13,<YM>,<OK>". If <OK> is non-zero, this is a positive
+ acknowledgment (approval). If it is zero, this is a negative
+ acknowledgment (i.e., refusal). <YM> is set to be equal to the
+ <IM> of #12, for identification purposes.
+
+ Messages #7, #8, and #9 are always a single word. Messages #1, #3,
+ #4, and #5 are several words long. Messages #2 and #6 are either a
+ single word or two words long. #10, #11 and #12 are always 2 words
+ long. Message #13 is always 3 words long. Message #1 is always 4
+ words long.
+
+ Message #1 is sent only by the CALLER, #3 only by the NEGOTIATION
+ MASTER, and #4 and #5 only by the NEGOTIATION SLAVE. Message #9 is
+
+
+
+
+Cohen [Page 6]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ sent only by the ANSWERER. All the other control messages may be
+ sent by either party.
+
+ The last <HOW> which was both suggested by the NEGOTIATION MASTER
+ (in #3) and accepted by the NEGOTIATION SLAVE (in #4) for each
+ <WHAT> is assumed to be in use.
+
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+Cohen [Page 7]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ DEFINITION OF THE <WHAT> AND <HOW> NEGOTIATION TABLES:
+
+ <WHAT> <HOW>
+
+ 1. VOCODING * 1. LPC
+ + 2. CVSD
+ 3. RELP
+ 4. DELCO
+
+ 2. SAMPLE PERIOD
+
+ (in microseconds) N. N (*150) (+62)
+
+ 3. VERSION
+
+ * 1. V1 (see definition below)
+ + 2. V2 (see definition below)
+
+ 4. MAX MSG LENGTH (in bits)
+
+ NVP header included N. N (*976 and +976)
+ (32 bits) but not HOST/IMP
+ leader and not HOST/IMP padding
+
+ 5. If LPC:
+
+ Degree N. For N coefficients (*10)
+
+ If CVSD:
+
+ Time Constant
+ (in milliseconds) N. N (+50)
+
+ 6. Samples per Parcel N. N (*128) (+224)
+
+ 7. If LPC:
+
+ Acoustic Coding * 1. SIMPLE (see below)
+ 2. OPTIMIZED
+
+ 8. If LPC:
+
+ Info Coding * 1. SIMPLE (see below)
+ 2. OPTIMIZED
+
+
+
+
+
+
+
+
+Cohen [Page 8]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ 9. If LPC:
+
+ Pre-emphasis N. N (*58, for
+ 1 - mu x [Z**-1] mu = 58/64 = 0.90625)
+ N = 64 x mu
+
+ 10. If LPC:
+
+ Table-set N. N (*1)
+ See definition of Set #1
+ in Appendix 1
+
+ (* indicates recommended options for LPC)
+ (+ indicates recommended options for CVSD)
+
+ No parameter (<WHAT>) should be inquired about by the NEGOTIATION
+ MASTER if some option (<HOW>) for it has been previously accepted
+ by the NEGOTIATION SLAVE implicitly in the "VERSION". The purpose
+ of this restriction is to avoid a possible conflict between
+ individual parameters and the VERSION-option.
+
+ Version 1 (V1) is defined as:
+
+ 1-1 LPC
+ 2-150 150 microseconds sampling
+ 3-1 V1
+ 5-10 10 coefficients
+ 6-128 128 samples per parcel
+ 7-1 SIMPLE acoustic coding
+ 8-1 SIMPLE information coding
+ 9-58 mu = 58/64 = 0.90625
+ 10-1 Tables set #1
+
+ Version 2 (V2) is defined as:
+
+ 1-2 CVSD
+ 2-62 62 microseconds sampling (16 KHz sampling)
+ 3-2 V2
+ 5-50 50 msec time constant
+ 6-192 192 samples per parcel
+
+ Note that this defines every negotiated parameter, except MAX
+ MSG LENGTH.
+
+ SIMPLE and OPTIMIZED codings will be described below in Section
+ 3.
+
+ All the negotiation is managed by the NEGOTIATION MASTER, who
+ decides how much negotiation is needed, and what to do in case
+
+
+
+Cohen [Page 9]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ some discrepancy (incompatibility) is discovered: either to try
+ alternative options or to abort the connection. Upon completion
+ of successful negotiation, the NEGOTIATION MASTER sends either
+ #9 (RINGING) only if it is the ANSWERER and if this is an
+ initial connection, else it sends #6 (READY-FOR-DATA), and
+ probably inquires with #8 about the readiness of the other
+ party. The inquiries (#8) before the successful completion of
+ the negotiation are ignored. However, these inquiries after the
+ first RINGING (#9) and before the first READY (#6) are needed
+ to keep the ANSWERER ringing.
+
+ Note that the negotiation process can be shortened by using the
+ VERSION option, as shown in the examples that follow.
+
+ ON RENEGOTIATION
+
+ At any stage after links are agreed upon, either party might
+ request a RENEGOTIATION. If the request is approved by the other
+ party, either party might become the NEGOTIATION MASTER, depending
+ on the type of renegotiation request. When renegotiation starts,
+ no previously negotiated agreements (except LINK numbers) hold,
+ and all items have to be renegotiated from scratch. Note that
+ renegotiation may entirely replace the negotiation phase and
+ allows the CALLER to be the NEGOTIATION MASTER.
+
+ Upon issuance (or reception) of RENEGOTIATION REQUEST, all data
+ messages are ignored until the positive indication of the
+ successful completion of the renegotiation (#6).
+
+ After the completion of renegotiation, the frame-count (see the
+ section on MESSAGE-HEADER) may be reset to zero.
+
+ THE HEADER OF DATA MESSAGES
+
+ Data messages are the messages which contain vocoded speech. The
+ first 32 bits of each data message is the MESSAGE-HEADER, which
+ carries sequence and timing information as described below.
+
+ For each vocoding scheme a "FRAME" is defined as the transmission
+ interval (as agreed upon at the negotiation stage in <WHAT#6>).
+ Since this interval is defined by the number of samples, its
+ duration can be found by multiplying the sampling period <WHAT#2>
+ by the interval length (in samples) <WHAT#6>. For example, in V1
+ the sampling period is 150 microseconds and the transmission
+ interval is 128 samples, which yields:
+
+ 128*150 microseconds = 19.2 milliseconds.
+
+ The data describing a FRAME is called a PARCEL. Each parcel has a
+
+
+
+Cohen [Page 10]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ serial number. The first parcel created after the completion of
+ the negotiation (or every RENEGOTIATION) has the serial number
+ zero. Each message contains an integral number of parcels.
+
+ The serial number of the first parcel in the message is put in the
+ first 16 bits of the message and is referred to as the
+ MESSAGE-TIME-STAMP. Note that this time stamp is synchronized with
+ the data stream. Note also that these 16 bits are actually the
+ third word of the message, following the 2 words used as
+ IMP-to-HOST leader (see BBN Report 1822).
+
+ The next bit in the header is the WE-SKIPPED-PARCELS bit, which is
+ described later. The next 7 bits tell how many parcels there are
+ in the message; this number is called the COUNT, or the
+ PARCEL-COUNT.
+
+ Note that if message number N has the time stamp T(N) and the
+ count C(N), then T(N+1) must be greater than or equal to
+ T(N)+C(N). Usually T(N+1) = T(N)+C(N), unless the XMTR decided not
+ to send some parcels due to silence. If this happens then the
+ WE-SKIPPED-PARCELS bit is set to ONE, else it is set to ZERO.
+ Hence, if T(N+1) is found by the RCVR to be greater than T(N)+C(N)
+ and the WE-SKIPPED-PARCELS is zero, some message must be lost.
+
+ Note that by definition the time stamps on messages monotonically
+ increase, except for wrap-around.
+
+ The message header structure is illustrated by the following
+ diagram:
+
+ WORD 1 WORD 2 WORD 3 WORD 4
+!................!................!................!................!...
+!P000TTTTHHIIIIII!LLLLLLLLZZZZZZZZ!TTTTTTTTTTTTTTTT!WCCCCCCCSSSSSSSS!DDD
+!................!................!................!^...............!...
+!<--HOST/IMP-OR-IMP/HOST-LEADER-->!<--TIME-STAMP-->!^<COUNT><-SAVE->!<-D
+ ^
+ WE-SKIPPED-PARCELS
+
+ P = PRIORITY (one bit = 1)
+ T = MESSAGE TYPE (4 bits = 0011)
+ L = link ("L" OR "K", 8 bits, greater than 337 octal)
+ D = data bits (from here to the end of the message)
+
+ ZZZZZZZZ = 8 ZERO bits
+ HHIIIIII = HOST (8 bits, destination or source)
+ CCCCCCC = parcel COUNT (7 bits)
+ SSSSSSSS = 8 bits saved for future applications
+ TTTTTTTTTTTTTTTT = TIME STAMP (16 bits)
+
+
+
+
+Cohen [Page 11]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ The first parcel sent by either party after the NEGOTIATION or
+ RENEGOTIATION should have the serial number set to zero.
+
+ During silence periods, the XMTR might send a "6" or "7"
+ message periodically. If it does not do so, the RCVR might
+ interrogate the livelihood of the XMTR by sending periodically
+ "8" ("ARE-YOU-THERE?") or #10 (ECHO-REQUEST) messages.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Cohen [Page 12]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ 3. THE LPC DATA PROTOCOL
+
+ The DATA sent at each transmission interval is called a PARCEL.
+
+ Network messages always contain an integral number of PARCELs.
+
+ There are two independent issues in the coding. One is, obviously,
+ the acoustic coding, i.e., which parameters have to be transmitted.
+ SIMPLE acoustic coding is sending all the parameters at every
+ transmission interval. OPTIMIZED acoustic coding sends only as little
+ as acoustically needed. DELCO is an example of OPTIMIZED acoustic
+ coding.
+
+ In this document only the format of the SIMPLE acoustic coding is
+ defined.
+
+ All the transmitted parameters are sent as pointers into agreed-upon
+ tables. These tables are defined as two lists of values. The
+ transmitter table {X(J)} is used in the following way: The value V is
+ coded as the code J if X(J-1) < V =< X(J). The receiver table {R(J)
+ is used to retrieve the value R(J) if the code J was received. X(-1)
+ is implicitly defined as minus-infinity, and X(Jmax) is explicitly
+ defined as plus-infinity.
+
+ For each parameter, {X(J)} and {R(J)} may be defined independently.
+
+ The second coding issue is the information coding technique. The
+ SIMPLE (information-wise) way of sending the information is to use
+ binary coding for the codes representing the parameters. The
+ OPTIMIZED way is to compute distributions for each parameter and to
+ define the appropriate coding. It is very probable that the PITCH and
+ GAIN will be decoded absolutely in the first PARCEL of each message,
+ and incrementally thereafter.
+
+ At present, only the SIMPLE (information-wise) coding is used.
+
+ The details of the LPC data protocol and its Tables-Set-#1 can be
+ found in Appendix 1.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Cohen [Page 13]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ Following is the definition for the format of the SIMPLE-SIMPLE
+ coding, according to Tables-Set-#1:
+
+ For each parcel:
+
+ PITCH 6 bits (PITCH=0 for UNVOICED)
+
+ GAIN 5 bits
+
+ I(1) 7 bits
+
+ I(2) 7 bits
+
+ I(3) 6 bits
+
+ I(4) 6 bits
+
+ I(5) 5 bits
+
+ I(6) 5 bits
+
+ I(7) 5 bits
+
+ I(8) 5 bits
+
+ I(9) 5 bits
+
+ I(10) 5 bits
+
+ where each of the I(j) is an index for inverse sine coding. If
+ K(j)=arcsin(Theta(j)) and N bits are assigned for its transmission,
+ then I(j)=(Theta(j)/Pi)*2**N.
+
+ Hence at each transmission interval (128 samples times 150
+ microseconds) 67 bits are sent, which results in a data rate of 3490
+ bps. Since this bandwidth is well within the capabilities of the
+ network, SIMPLE-SIMPLE coding is used, which requires the least
+ computation by the hosts. Note that this data rate is a peak rate,
+ without the use of silence.
+
+
+
+
+
+
+
+
+
+
+
+
+
+Cohen [Page 14]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ 4. EXAMPLES FOR THE CONTROL PROTOCOL
+
+ Here is an example for a connection:
+
+ (377) C: 1,<WHO>,<WHOM>,340 Please talk to me on 340/341.
+
+ (340) A: 2,1 I refuse, since I'm busy.
+
+ Another example:
+
+ (377) C: 1,<WHO>,<WHOM>,360 Please talk to me on 360/361.
+
+ (360) A: 6,350 OK. You talk to me on 350/351.
+
+ (350) C: 1,<WHO>,<WHOM> I want to talk to you.
+
+ (360) A: 3,1,1,2 Can you do CVSD? (ANSWERER tries
+ to be the NEGOTIATION MASTER)
+
+ (350) C: 12,1 I want to be it.
+
+ (360) A: 13,1 That's OK with me.
+
+ (350) C: 3,1,1,2 Can you do CVSD?
+
+ (360) A: 5,1,1 No, but I can do LPC.
+
+ (350) C: 3,1,1,3 Can you do RELP?
+
+ (360) A: 5,1,1 No, but I can do LPC.
+
+ (350) C: 3,1,1,1 How about LPC?
+
+ (360) A: 4,1,1 LPC is fine with me.
+
+ (350) C: 3,2,1,150 Can you use 150 microseconds
+ sampling?
+
+ (360) A: 4,2,150 I can use 150 microseconds.
+
+ (350) C: 3,4,3,976,1040,2016 Can you use 976, 1040, or 2016
+ bits/msg?
+
+ (360) A: 4,4,976 I can use 976.
+
+ (350) C: 3,5,1,10 Can you send 10 coefficients?
+
+ (360) A: 4,5,10 I can send 10.
+
+
+
+
+Cohen [Page 15]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ (350) C: 3,6,1,64 Can you use a 64 sample
+ transmission?
+
+ (360) A: 4,6,64 I can use 64.
+
+ (350) C: 3,7,2,1,2 SIMPLE or OPTIMIZED acoustic
+ coding?
+
+ (360) A: 4,7,2 OPTIMIZED!
+
+ (350) C: 3,8,1,1 Can you do SIMPLE info coding?
+
+ (360) A: 4,8,1 I can do SIMPLE.
+
+ (350) C: 3,9,1,58 mu = 0.90625?
+
+ (360) A: 4,9,58 Fine with me.
+
+ (350) C: 3,10,1 Table set #1?
+
+ (360) A: 4,10,1 Of course!
+
+ (350) C: 6 I am ready. (Note: No "RINGING"
+ sent)
+
+ (350) C: 8 And you?
+
+ (360) A: 6 I am ready, too.
+
+ ....... Data is exchanged now,
+
+ ....... on 351 and 361.
+
+ (350) C: 10,1234 Echo it, please.
+
+ (360) A: 11,1234 Here it comes!
+
+ .......
+
+ (360) A: 10,3333 Now ANSWERER wants to measure
+
+ (350) C: 11,3333 ...the delays, too.
+
+ .......
+
+ (???) X: 2,3 Termination by either user.
+
+
+
+
+
+
+Cohen [Page 16]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ Another example:
+
+ (377) C: 1,<WHO>,<WHOM>,360 Please talk to me on 360/361.
+
+ (360) A: 6,340 Fine. You send on 340/341.
+
+ (340) C: 1,<WHO>,<WHOM> I want to talk to you.
+
+ (360) A: 3,3,1,1 Can you use V1?
+
+ (340) C: 4,3,1 Yes, V1 is OK.
+
+ (360) A: 3,4,1,1984 Can you use up to 1984 bits/msg?
+
+ (340) C: 5,4,976 No, but I can use 976.
+
+ (360) A: 3,4,1,976 Can you use up to 976 bits/msg?
+
+ (340) C: 4,4,976 I can use 976.
+
+ (360) A: 9 Ringing (note how short this
+ negotiation is!!).
+
+ .......
+
+ (340) C: 8 Still there?
+
+ (360) A: 9 Still ringing.
+
+ .......
+
+ (340) C: 8 Still there?
+
+ (360) A: 9 Still ringing.
+
+ .......
+
+ (340) C: 8 How about it?
+
+ (360) A: 9 Still ringing.
+
+ (340) C: 2 Forget it! (No reason given.)
+
+
+
+
+
+
+
+
+
+
+Cohen [Page 17]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ APPENDIX 1
+
+
+
+ THE DEFINITION OF:
+
+ TABLES-SET-#1
+
+
+
+
+
+
+ by
+
+ John D. Markel
+
+ Speech Communication Research Laboratory
+
+ Santa Barbara, California
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Cohen [Page 18]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ TABLES-SET-#1
+
+ This set includes tables for:
+
+
+
+
+
+ PITCH - 64 values, PITCH table
+ GAIN - 32 values, GAIN table
+ I( 1) - 128 values, INDEX7 table
+ I( 2) - 128 values, INDEX7 table
+ I( 3) - 64 values, INDEX6 table
+ I( 4) - 64 values, INDEX6 table
+ I( 5) - 32 values, INDEX5 table
+ I( 6) - 32 values, INDEX5 table
+ I( 7) - 32 values, INDEX5 table
+ I( 8) - 32 values, INDEX5 table
+ I( 9) - 32 values, INDEX5 table
+ I(10) - 32 values, INDEX5 table
+
+ These tables are defined specifically for a sampling period of 150
+ microseconds.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Cohen [Page 19]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ GENERAL COMMENTS
+
+ The following tables are arranged in three columns, {X(j)}, {j},
+ and {R(j)}. Note that the entries in the {X(j)} column are half a
+ step off the other columns. This is to indicate that INTERVALS
+ from X-domain (pitch, gain, and the Ks) are mapped into CODES {j},
+ which are transmitted over the network, to be translated by the
+ receiver into the {R(j)}. These intervals are defined as
+ OPEN-CLOSE intervals. For example, the PITCH value (at the
+ transmitter) of 4131 belongs to the interval "(4024,4131]", hence
+ it is coded as j=6 which is mapped by the receiver to the value
+ 21. Similarly, the value of 2400 for INDEX7 is found to belong to
+ the interval "(2009,2811]", coded into the CODE 3 and mapped back
+ into 2411.
+
+ Note that if N bits are used by a certain CODE, then there are
+ 2**N+1 entries in the X-table, but only 2**N entries in the
+ R-table.
+
+ The transformation values used for PITCH, GAIN, and the
+ K-parameters (in the X- and R-tables) are as defined in NSC Note
+ 42.
+
+ Values above and below the range of the X-table are mapped into
+ the maximum and minimum table indices, respectively.
+
+ Note that R(J) of INDEX5 is identical to R(2J) of INDEX6, and that
+ R(J) of INDEX6 is identical to R(2J) of INDEX7. Therefore, it is
+ possible to store only the R-table of INDEX7, without the R-tables
+ of INDEX5 and INDEX6.
+
+ In the SPS-41 implementation there is no need to store any R-table
+ for the K-parameters. The transmitted index can be used directly
+ (with the appropriate scaling) as an index into the SPS built-in
+ TRIG tables.
+
+ COMMENTS ON THE PITCH TABLE
+
+ The level J=0 defines the UNVOICED condition. The receiver maps it
+ into the number of samples per frame (here 128).
+
+ This PITCH table differs significantly from previous tables and
+ supersedes the table published in NSC Note 36. Details of the
+ calculation of the table can be found in NSC Note 42. Immediate
+ questions should be referred to John Markel.
+
+
+
+
+
+
+
+Cohen [Page 20]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ COMMENTS ON THE GAIN TABLE
+
+ The level J=0 defines absolute silence.
+
+ This table is designed for a maximum of 12-bit A/D input, and
+ allows for a dynamic range of 43.5 dB.
+
+ NSC Notes 36, 45, 56 and 58 supply background for the GAIN table.
+ Gain is the energy of the pre-emphasized, windowed signal.
+
+ This table is the NEW GAIN table. NSC Notes 56 and 58 explain the
+ reasoning behind the NEW GAIN.
+
+ COMMENTS ON THE INDEX7 TABLE
+
+ Positive values are coded into the range [0-63, decimal]. Negative
+ values are coded into the 7-bits two's complement of the codes of
+ their absolute value [65-127, decimal].
+
+ Note that all values -403 < V < 403 are coded as (and mapped into)
+ 0. Note also that the code -64 (100 octal) is never used.
+
+ In SPS-41 implementation, the R-table is not needed, since
+ TRIG(2J) is the needed value R(J).
+
+ COMMENTS ON THE INDEX6 TABLE
+
+ Positive values are coded into the range [0-31, decimal]. Negative
+ values are coded into the 6-bits two's complement of the codes of
+ their absolute values [33-63, decimal].
+
+ Note that all values -805 < V < 805 are coded as (and mapped into)
+ 0. Note also that the code -32 (40 octal) is never used.
+
+ In SPS-41 implementation, the R-table is not needed, since
+ TRIG(4J) is the needed value R(J).
+
+ COMMENTS ON THE INDEX5 TABLE
+
+ Positive numbers are coded into the range [0-15, decimal].
+ Negative numbers are coded into the 5-bits two's complement of
+ their absolute values, i.e., [17-31, decimal].
+
+ Note that all values -1609 < V < 1609 are coded as (and mapped
+ into) 0. Note also that the code -16 (20 octal) is never used.
+
+ In SPS-41 implementation, the R-table is not needed, since
+ TRIG(8J) is the needed value R(J).
+
+
+
+
+Cohen [Page 21]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ THE PITCH TABLE (as of 10-29-74)
+
+ X(J) J R(J) X(J) J R(J) X(J) J R(J)
+
+ 0 6002 10770
+ 0 128* 21 33 42 61
+ 0 6168 11080
+ 1 18 22 34 43 63
+ 3630 6338 11399
+ 2 19 23 35 44 65
+ 3724 6515 11728
+ 3 19 24 36 45 67
+ 3821 6696 12067
+ 4 20 25 37 46 69
+ 3921 6883 12417
+ 5 20 26 38 47 71
+ 4024 7075 12776
+ 6 21 27 39 48 73
+ 4131 7274 13147
+ 7 22 28 40 49 75
+ 4240 7478 13529
+ 8 22 29 41 50 77
+ 4353 7689 13922
+ 9 23 30 43 51 80
+ 4469 7905 14327
+ 10 24 31 44 52 82
+ 4588 8129 14745
+ 11 24 32 45 53 85
+ 4711 8359 15175
+ 12 25 33 47 54 87
+ 4838 8596 15618
+ 13 26 34 48 55 90
+ 4969 8840 16075
+ 14 27 35 50 56 93
+ 5104 9092 16545
+ 15 27 36 51 57 95
+ 5242 9351 17029
+ 16 28 37 53 58 98
+ 5385 9618 17529
+ 17 29 38 54 59 101
+ 5533 9894 18043
+ 18 30 39 56 60 104
+ 5684 10177 18572
+ 19 31 40 57 61 107
+ 5841 10469 19118
+ 20 32 41 59 62 111
+ 6002 10770 19681
+ 63 114
+ infinity
+
+
+
+Cohen [Page 22]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ Note: This table has only 58 different intervals defined, since 5
+ values are repeated in the R(j) table.
+
+ * This value is the "Transmission Interval" (measured in samples)
+ as defined in item #6 of the NEGOTIATION.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Cohen [Page 23]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ THE GAIN TABLE (as of 9-17-75)
+
+ X(J) J R(J) X(J) J R(J)
+
+ 0 225
+ 0 0 16 245
+ 20 266
+ 1 20 17 289
+ 22 315
+ 2 24 18 342
+ 26 372
+ 3 28 19 404
+ 30 439
+ 4 33 20 478
+ 36 519
+ 5 39 21 565
+ 42 614
+ 6 46 22 667
+ 50 725
+ 7 54 23 789
+ 59 857
+ 8 64 24 932
+ 70 1013
+ 9 76 25 1101
+ 83 1197
+ 10 90 26 1301
+ 98 1415
+ 11 106 27 1538
+ 116 1672
+ 12 126 28 1818
+ 137 1976
+ 13 148 29 2148
+ 161 2335
+ 14 175 30 2539
+ 191 2760
+ 15 207 31 3000
+ 255 infinity
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Cohen [Page 24]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ INDEX7 TABLE (as of 9-23-74)
+
+ X(J) J R(J) X(J) J R(J) X(J) J R(J)
+
+ 0 15800 27897
+ 0 0 21 16151 42 28106
+ 402 16500 28311
+ 1 804 22 16846 43 28511
+ 1206 17190 28707
+ 2 1608 23 17531 44 28899
+ 2009 17869 29086
+ 3 2411 24 18205 45 29269
+ 2811 18538 29448
+ 4 3212 25 18868 46 29622
+ 3612 19195 29792
+ 5 4011 26 19520 47 29957
+ 4410 19841 30118
+ 6 4808 27 20160 48 30274
+ 5205 20475 30425
+ 7 5602 28 20788 49 30572
+ 5998 21097 30715
+ 8 6393 29 21403 50 30853
+ 6787 21706 30986
+ 9 7180 30 22006 51 31114
+ 7571 22302 31238
+ 10 7962 31 22595 52 31357
+ 8351 22884 31471
+ 11 8740 32 23170 53 31581
+ 9127 23453 31686
+ 12 9512 33 23732 54 31786
+ 9896 24008 31881
+ 13 10279 34 24279 55 31972
+ 10660 24548 32058
+ 14 11039 35 24812 56 32138
+ 11417 25073 32214
+ 15 11793 36 25330 57 32286
+ 12167 25583 32352
+ 16 12540 37 25833 58 32413
+ 12910 26078 32470
+ 17 13279 38 26320 59 32522
+ 13646 26557 32568
+ 18 14010 39 26791 60 32610
+ 14373 27020 32647
+ 19 14733 40 27246 61 32679
+ 15091 27467 32706
+ 20 15447 41 27684 62 32729
+ 15800 27897 32746
+ 63 32758
+ infinity
+
+
+
+Cohen [Page 25]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ INDEX6 TABLE (as of 9-23-74)
+
+ X(J) J R(J) X(J) J R(J)
+
+ 0 22595
+ 0 0 16 23170
+ 804 23732
+ 1 1608 17 24279
+ 2411 24812
+ 2 3212 18 25330
+ 4011 25833
+ 3 4808 19 26320
+ 5602 26791
+ 4 6393 20 27246
+ 7180 27684
+ 5 7962 21 28106
+ 8740 28511
+ 6 9512 22 28899
+ 10279 29269
+ 7 11039 23 29622
+ 11793 29957
+ 8 12540 24 30274
+ 13279 30572
+ 9 14010 25 30853
+ 14733 31114
+ 10 15447 26 31357
+ 16151 31581
+ 11 16846 27 31786
+ 17531 31972
+ 12 18205 28 32138
+ 18868 32286
+ 13 19520 29 32413
+ 20160 32522
+ 14 20788 30 32610
+ 21403 32679
+ 15 22006 31 32729
+ 22595 infinity
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Cohen [Page 26]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ INDEX5 TABLE (as of 9-23-74)
+
+ X(J) J R(J) X(J) J R(J)
+
+ 0 22006
+ 0 0 8 23170
+ 1608 24279
+ 1 3212 9 25330
+ 4808 26320
+ 2 6393 10 27246
+ 7962 28106
+ 3 9512 11 28899
+ 11039 29622
+ 4 12540 12 30274
+ 14010 30853
+ 5 15447 13 31357
+ 16846 31786
+ 6 18205 14 32138
+ 19520 32413
+ 7 20788 15 32610
+ 22006 infinity
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Cohen [Page 27]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ APPENDIX 2
+
+ IMPLEMENTATION RECOMMENDATIONS
+
+ (1) It is recommended that the priority-bit be turned ON in the
+ HOST/IMP header.
+
+ (2) It is recommended that in all abbreviations, "R" be used for
+ Receiver and "X" for Transmitter.
+
+ (3) The following identifiers and values are recommended for
+ implementations:
+
+ SLNCTH 30 SILENCE-THRESHOLD.
+
+ Used for LONG-SILENCE definition. See below. Measured in the
+ same units as GAIN, in its X-table.
+
+ TBS 1.000 sec TIME-BEGIN-SILENCE.
+
+ LONG-SILENCE is declared if GAIN<SLNCTH for more than TBS.
+
+ TAS 0.500 sec TIME-AFTER-SILENCE.
+
+ A delay introduced by the receiver after the end of
+ LONG-SILENCE, before restarting the playback.
+
+ TES 0.150 sec TIME-END-SILENCE.
+
+ The amount of time the transmitter backs up at the end of a
+ LONG-SILENCE in order to ensure a smooth transition back to
+ speech.
+
+ TRI 2.000 sec TIME-RESPONSE-INITIAL.
+
+ Time for waiting for response for an initial call (#1 and #3).
+ The initial call is repeated every TRI until an answer arrives,
+ or until TRIGU expires.
+
+ TRIGU 20.000 sec TIME-RESPONSE-INITIAL-GIVEUP.
+
+ If no response to an initial call is received within TRIGU
+ after the FIRST initial call, the system gives up, assuming the
+ other system is down.
+
+ TRQ 1.000 sec TIME-RESPONSE-INQUIRY.
+
+ If no response to an inquiry (#8) is received within TRQ, the
+ inquiry is repeated.
+
+
+
+Cohen [Page 28]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ TRQGU 10.000 sec TIME-RESPONSE-INQUIRY-GIVEUP.
+
+ If no response to an inquiry is received within TRQGU from the
+ FIRST inquiry, the system gives up, assuming the other system
+ is down.
+
+ TBDA 3.000 sec TIME-BETWEEN-DATA-ARRIVAL.
+
+ If no data arrives within TBDA, an INQUIRY (#8) is sent. This
+ repeats every TBDA.
+
+ TNR 2.000 sec TIME-NOT-READY.
+
+ If the other system is in the NOT-READY (#7) state for more
+ than TNR, an INQUIRY (#8) is sent. This repeats every TNR.
+
+ TNRGU 10.000 sec TIME-NOT-READY-GIVEUP.
+
+ If the other system is in the NOT-READY (#7) state for more
+ than TNRGU, then the system gives up, assuming the other
+ system is down.
+
+ TBIN 3.000 sec TIME-BUFFER-IN.
+
+ The input buffer size is equivalent to the time period TBIN
+ (and its size is the DATA-RATE multiplied by the period
+ TBIN). If the INPUT QUEUE ever gets to be longer than TBIN,
+ data is discarded.
+
+ TBOUT 3.000 sec TIME-BUFFER-OUT.
+
+ The output buffer size is equivalent to the time period TBOUT
+ (and its size is the DATA-RATE multiplied by the period
+ TBOUT). If the OUTPUT QUEUE ever gets to be longer than
+ TBOUT, data is discarded.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Cohen [Page 29]
+
+NWG/RFC 741 DC 22 Nov 77 42444
+Specifications for the Network Voice Protocol (NVP)
+
+
+
+ REFERENCES
+
+ Bolt Beranek & Newman, Inc., Report No. 1822, Interface Message
+ Processor: Specifications for the Interconnection of a Host and an
+ IMP.
+
+ NSC Note 42 (in progress).
+
+ NSC Note 36, Proposal for NSC-LPC Coding/Decoding Tables, by J. D.
+ Markel, Speech Communications Research Laboratory, Inc., July 20,
+ 1974.
+
+ NSC Note 45, Everything You Always Wanted to Know about Gain, by E.
+ Randolph Cole, USC/Information Sciences Institute, October 11, 1974.
+
+ NSC Note 56, Nothing to Lose, but Lots to Gain, by John Makhoul and
+ Lynn Cosell, Bolt Beranek & Newman, Inc., March 10, 1975.
+
+ NSC Note 58, Gain Again, by Randy Cole, USC/Information Sciences
+ Institute, March 12, 1975.
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+
+Cohen [Page 30]