rfc841.txt

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      RFC 841


      FIPS Pub 98





      SPECIFICATION FOR MESSAGE FORMAT FOR COMPUTER
      BASED MESSAGE SYSTEMS




      








      27 January 1983




















      National Bureau of Standards


      This RFC is FIPS 98.  The purpose of distributing this document
      as an RFC is to make it easily accesible to the ARPA research
      community.  This RFC does not specify a standard for the ARPA
      Internet.










                              TABLE OF CONTENTS




                                                                   Page



      EXECUTIVE SUMMARY                                               5



      1.  INTRODUCTION                                                7


          1.1  Guide to Reading This Document                         7
          1.2  Vendor-Defined Extensions to the Specification         8
          1.3  The Scope of the Message Format Specification          8
          1.4  Issues Not Within the Scope of the Message Format      8
               Specification
          1.5  Relationship to Other Efforts                          9



      2.  A SIMPLE MODEL OF A CBMS ENVIRONMENT                       10


          2.1  Logical Model of a CBMS                               12
          2.2  Relationship to the ISO Reference Model for Open      14
               Systems Interconnection
          2.3  Messages and Fields                                   14
          2.4  Message Originators and Recipients                    15



      3.  SEMANTICS                                                  17


          3.1  Semantics of Message Fields                           17
               3.1.1  Types of fields                                17
               3.1.2  Semantic Compliance Categories                 18
               3.1.3  Originator fields                              18
               3.1.4  Recipient fields                               19
               3.1.5  Date fields                                    20
               3.1.6  Cross-reference fields                         21
               3.1.7  Message-handling fields                        22
               3.1.8  Message-content fields                         23
               3.1.9  Extensions                                     23






                                      i



          3.2  Message Processing Functions                          24
               3.2.1  Message creation and posting                   24
               3.2.2  Message reissuing and forwarding               25
                    3.2.2.1  Redistribution                          26
                    3.2.2.2  Assignment                              28
               3.2.3  Reply generation                               28
               3.2.4  Cross-referencing                              29
                    3.2.4.1  Unique identifiers                      29
                    3.2.4.2  Serial numbering                        30
               3.2.5  Life span functions                            30
               3.2.6  Requests for recipient processing              31
                    3.2.6.1  Message circulation                     31
          3.3  Multiple Occurrences and Ordering of Fields           31



      4.  SYNTAX                                                     34


          4.1  Introduction                                          34
               4.1.1  Message structure                              34
               4.1.2  Data elements                                  35
                    4.1.2.1  Primitive data elements                 36
                    4.1.2.2  Constructor data elements               36
               4.1.3  Properties                                     36
                    4.1.3.1  Printing-names                          37
                    4.1.3.2  Comments                                37
               4.1.4  Data compression and encryption                37
          4.2  Overview of Syntax Encoding                           37
               4.2.1  Identifier Octets                              38
               4.2.2  Length code and Qualifier components           39
                    4.2.2.1  Length Codes                            41
                    4.2.2.2  Qualifier                               42
               4.2.3  Property-List                                  44
               4.2.4  Data Element Contents                          44
          4.3  Data Element Syntax                                   44
               4.3.1  Data elements                                  45
                    4.3.1.1  Primitives                              47
                    4.3.1.2  Constructors                            49
                    4.3.1.3  Data Elements that Extend this Speci-   52
                             fication
               4.3.2  Using data elements within message fields      53
               4.3.3  Properties and associated elements             54
               4.3.4  Encryption identifiers                         54
               4.3.5  Compression identifiers                        54
               4.3.6  Message types                                  55









                                     ii



      SUMMARY OF APPENDIXES                                          56



      APPENDIX A.  FIELDS -- IMPLEMENTORS' MASTER REFERENCE          57



      APPENDIX B.  DATA ELEMENTS -- IMPLEMENTORS' MASTER REFERENCE   63



      APPENDIX C.  DATA ELEMENT IDENTIFIER OCTETS                    71



      APPENDIX D.  SUMMARY OF MESSAGE FIELDS BY COMPLIANCE CATE-     72
                   GORY


          D.1  REQUIRED Fields                                       72
          D.2  BASIC Fields                                          72
          D.3  OPTIONAL Fields                                       72



      APPENDIX E.  SUMMARY OF MESSAGE SEMANTICS BY FUNCTION          74


          E.1  Circulation                                           74
          E.2  Cross-Referencing                                     74
          E.3  Life Spans                                            74
          E.4  Delivery System                                       74
          E.5  Miscellaneous Fields Used Generally                   75
          E.6  Reply Generation                                      75
          E.7  Reissuing                                             75
          E.8  Sending (Normal Transmission)                         75



      APPENDIX F.  SUMMARY OF DATA ELEMENT SYNTAX                    76



      APPENDIX G.  SUMMARY OF DATA ELEMENTS BY COMPLIANCE CATEGORY   78


          G.1  BASIC Data Elements                                   78
          G.2  OPTIONAL Data Elements                                78






                                     iii



      APPENDIX H.  EXAMPLES                                          80


          H.1  Primitive Data Elements                               80
          H.2  Constructor Data Elements                             82
          H.3  Data Elements that Extend this Specification          87
          H.4  Fields                                                88
          H.5  Messages                                              90
          H.6  Unknown Lengths                                       94
          H.7  Message Encoding Using Vendor-Defined Fields          97
               H.7.1  Example of a JANAP-128 Message                 97
               H.7.2  Encoding of Example using the FIPS Message     97
                      Format
               H.7.3  Field Mappings of JANAP-128 to FIPS Format    101
               H.7.4  Vendor-Defined Fields                         101



      REFERENCES                                                    103



      INDEX                                                         105
































                                     iv



                               LIST OF FIGURES




      FIG. 1.    LOGICAL MODEL OF A COMPUTER-BASED MESSAGE SYSTEM    12
      FIG. 2.    MESSAGE FORWARDING AND REDISTRIBUTION               27
      FIG. 3.    EXAMPLE OF MESSAGE CIRCULATION                      32
      FIG. 4.    STRUCTURE OF IDENTIFIER OCTETS                      39
      FIG. 5.    ENCODING MECHANISM FOR QUALIFIERS AND LENGTH        40
                 CODES
      FIG. 6.    REPRESENTATION OF LENGTH CODES                      42
      FIG. 7.    EXAMPLES OF QUALIFIER VALUES                        43