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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 <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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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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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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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:
  1. 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.
  1. Design such that no system can tie up the resources of another

system unnecessarily.

  1. Avoidance of end-to-end retransmission.
  1. Separation of control signals from data traffic.
  1. Separation of vocoding-dependent parts from vocoding-independent

parts.

  1. Adaptation to the dynamic network performance.
  1. Optimal performance, i.e. guaranteed required bandwidth, and

minimized maximum delay.

  1. 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".

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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.

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 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>"

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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.

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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.

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    #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

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    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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 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

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    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

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       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

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    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)

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       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.

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                     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.

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 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.

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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.

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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.

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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.)

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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

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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.

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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.

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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

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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

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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.

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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.

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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]

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