rfc741.txt

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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
















Cohen                                                          [Page ii]

NWG/RFC 741                                           DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)



                                PREFACE

   The major objective  of ARPA's  Network  Secure  Communications (NSC)
   project  is to develop  and demonstrate  the feasibility  of  secure,
   high-quality, low-bandwidth, real-time, full-duplex (two-way) digital
   voice communications  over  packet-switched  computer  communications
   networks.   This kind  of  communication  is  a  very  high  priority
   military  goal for all levels  of  command  and  control  activities.
   ARPA's  NSC projrct will supply digitized speech which can be secured
   by existing  encryption  devices.  The major goal of this research is
   to demonstrate  a digital  high-quality,  low-bandwidth, secure voice
   handling  capability  as part of the general military requirement for
   worldwide  secure voice communication.  The development at ISI of the
   Network  Voice Protocol  described herein is an important part of the
   total effort.





































Cohen                                                         [Page iii]

NWG/RFC 741                                           DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)



                            ACKNOWLEDGMENTS

   The Network Voice Protocol (NVP), implemented first in December 1973,
   and has been in use since then for local and transnet real-time voice
   communication over the ARPANET at the following sites:

      o    Information  Sciences  Institute,  for LPC and CVSD,  with  a
           PDP-11/45 and an SPS-41.

      o    Lincoln  Laboratory,  for LPC and CVSD,  with a TX2  and  the
           Lincoln FDP, and with a PDP-11/45 and the LDVT.

      o    Culler-Harrison,  Inc.,  for LPC,  with  the  Culler-Harrison
           MP32A and AP-90.

      o    Stanford Research Institute, for LPC, with a PDP-11/40 and an
           SPS-41.

   The NVP's success  in bridging  the  differences  between  the  above
   systems  is due mainly  to the cooperation  of  many  people  in  the
   ARPA-NSC  community,  including Jim Forgie (Lincoln Laboratory), Mike
   McCammon  (Culler-Harrison),  Steve Casner  (ISI)  and Paul  Raveling
   (ISI),  who participated  heavily  in the definition  of the  control
   protocol;   and   John   Markel   (Speech   Communications   Research
   Laboratory),  John Makhoul  (Bolt Beranek  & Newman,  Inc.) and Randy
   Cole (ISI),  who participated in the definition of the data protocol.
   Many other people  have contributed  to the NVP-based effort, in both
   software and hardware support.
























Cohen                                                          [Page iv]

NWG/RFC 741                                           DC 22 Nov 77 42444
Specifications for the Network Voice Protocol (NVP)



                            1.  INTRODUCTION

   Currently,  computer  communication  networks  are designed  for data
   transfer.   Since there  is  a  growing  need  for  communication  of
   real-time interactive voice over computer networks, new communication
   discipline  must be developed.   The current HOST-to-HOST protocol of
   the ARPANET,  which was designed  (and optimized)  for data transfer,
   was found  unsuitable  for  real-time  network  voice  communication.
   Therefore   this  Network  Voice  Protocol  (NVP)  was  designed  and
   implemented.

   Important design objectives of the NVP are:

      - Recovery  of loss of any message  without  catastrophic effects.
        Therefore  all answers have to be unambiguous, in the sense that
        it must be clear to which inquiry a reply refers.

      - Design  such that no system  can tie up the resources of another
        system unnecessarily.

      - Avoidance of end-to-end retransmission.

      - Separation of control signals from data traffic.

      - Separation of vocoding-dependent parts from vocoding-independent
        parts.

      - Adaptation to the dynamic network performance.

      - Optimal  performance,  i.e.  guaranteed  required bandwidth, and
        minimized maximum delay.

      - Independence from lower level protocols.

   The protocol consists of two parts:

      (1) The control protocol,

      (2) The data protocol.

   Control messages are sent as controlled (TYPE 0/0) messages, and data
   messages  may be sent as either controlled (TYPE 0/0) or uncontrolled
   (TYPE  0/3)   messages   (see  BBN  Report  1822  for  definition  of
   MESSAGE-TYPE).

   Throughout this document a "word" means a "16-bit quantity".






Cohen                                                           [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.




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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.



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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",