rfc806.txt

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Network Working Group
Request for Comments: 806




      
      Proposed Federal Information Processing Standard




      SPECIFICATION FOR MESSAGE FORMAT FOR 
      COMPUTER BASED MESSAGE SYSTEMS




      National Bureau of Standards
      Institute for Computer Sciences and Technology







      September 1981











      

      
      
      


      
      





                              TABLE OF CONTENTS




                                                                   Page



      EXECUTIVE SUMMARY                                               1



      1.  INTRODUCTION                                                3


          1.1  Guide to Reading This Document                         3
          1.2  Vendor-Defined Extensions to the Specification         4
          1.3  The Scope of the Message Format Specification          4
          1.4  Issues Not Within the Scope of the Message Format      4
               Specification
          1.5  Relationship to Other Efforts                          5



      2.  A SIMPLE MODEL OF A CBMS ENVIRONMENT                        6


          2.1  Logical Model of a CBMS                                8
          2.2  Relationship to the ISO Reference Model for Open      10
               Systems Interconnection
          2.3  Messages and Fields                                   10
          2.4  Message Originators and Recipients                    11



      3.  SEMANTICS                                                  12


          3.1  Semantics of Message Fields                           12
               3.1.1  Types of fields                                12
               3.1.2  Semantic Compliance Categories                 13
               3.1.3  Originator fields                              13
               3.1.4  Recipient fields                               14
               3.1.5  Date fields                                    15
               3.1.6  Cross-reference fields                         16
               3.1.7  Message-handling fields                        16
               3.1.8  Message-content fields                         17
               3.1.9  Extensions                                     18




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          3.2  Message Processing Functions                          18
               3.2.1  Message creation and posting                   19
               3.2.2  Message reissuing and forwarding               20
                    3.2.2.1  Redistribution                          22
                    3.2.2.2  Assignment                              22
               3.2.3  Reply generation                               23
               3.2.4  Cross referencing                              24
                    3.2.4.1  Unique identifiers                      24
                    3.2.4.2  Serial numbering                        24
               3.2.5  Life span functions                            25
               3.2.6  Requests for recipient processing              25
                    3.2.6.1  Message circulation                     26
          3.3  Multiple Occurrences and Ordering of Fields           26



      4.  SYNTAX                                                     28


          4.1  Introduction                                          28
               4.1.1  Message structure                              28
               4.1.2  Data elements                                  29
                    4.1.2.1  Primitive data elements                 30
                    4.1.2.2  Constructor data elements               30
               4.1.3  Properties                                     30
                    4.1.3.1  Printing-names                          30
                    4.1.3.2  Comments                                31
               4.1.4  Data compression and encryption                31
               4.1.5  Data sharing                                   31
          4.2  Overview of Syntax Encoding                           32
               4.2.1  Identifier Octets                              32
               4.2.2  Length code and Qualifier components           33
                    4.2.2.1  Length Codes                            35
                    4.2.2.2  Qualifier                               36
               4.2.3  Property-List                                  38
               4.2.4  Data Element Contents                          38
          4.3  Data Element Syntax                                   39
               4.3.1  Data elements                                  39
                    4.3.1.1  Primitives                              42
                    4.3.1.2  Constructors                            44
               4.3.2  Using data elements within message fields      48
               4.3.3  Properties and associated elements             49
               4.3.4  Encryption identifiers                         49
               4.3.5  Compression identifiers                        49
               4.3.6  Message types                                  50



      SUMMARY OF APPENDIXES                                          51



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      APPENDIX A.  FIELDS -- IMPLEMENTORS' MASTER REFERENCE          52



      APPENDIX B.  DATA ELEMENTS -- IMPLEMENTORS' MASTER REFERENCE   57



      APPENDIX C.  DATA ELEMENT IDENTIFIER OCTETS                    65



      APPENDIX D.  SUMMARY OF MESSAGE FIELDS BY COMPLIANCE           66
                   CATEGORY


          D.1  REQUIRED Fields                                       66
          D.2  BASIC Fields                                          66
          D.3  OPTIONAL Fields                                       66



      APPENDIX E.  SUMMARY OF MESSAGE SEMANTICS BY FUNCTION          68


          E.1  Circulation                                           68
          E.2  Cross Referencing                                     68
          E.3  Life spans                                            68
          E.4  Delivery System                                       68
          E.5  Miscellaneous Fields Used Generally                   69
          E.6  Reply Generation                                      69
          E.7  Reissuing                                             69
          E.8  Sending (Normal Transmission)                         69



      APPENDIX F.  SUMMARY OF DATA ELEMENT SYNTAX                    70



      APPENDIX G.  SUMMARY OF DATA ELEMENTS BY COMPLIANCE CATEGORY   72


          G.1  BASIC Data Elements                                   72
          G.2  OPTIONAL Data Elements                                72



      APPENDIX H.  EXAMPLES                                          74




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          H.1  Primitive Data Elements                               74
          H.2  Constructor Data Elements                             76
          H.3  Fields                                                81
          H.4  Messages                                              84
          H.5  Unknown Lengths                                       88



      REFERENCES                                                     92



      INDEX                                                          94








































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                               LIST OF FIGURES




      FIG. 1.    LOGICAL MODEL OF A COMPUTER BASED MESSAGE SYSTEM     8
      FIG. 2.    MESSAGE FORWARDING AND REDISTRIBUTION               21
      FIG. 3.    EXAMPLE OF MESSAGE CIRCULATION                      27
      FIG. 4.    STRUCTURE OF IDENTIFIER OCTETS                      34
      FIG. 5.    ENCODING MECHANISM FOR QUALIFIERS AND LENGTH        35
                 CODES
      FIG. 6.    REPRESENTATION OF LENGTH CODES                      36
      FIG. 7.    EXAMPLES OF LENGTH CODES                            37
      FIG. 8.    EXAMPLES OF QUALIFIER VALUES                        38








































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