rfc841.txt

著名的RFC文档,其中有一些文档是已经翻译成中文的的.

      TABLE 1.    FIELDS USED IN MESSAGE PROCESSING FUNCTIONS        24
      TABLE 2.    HIGH-ORDER BITS IN THE IDENTIFIER OCTET            39
















































                                     vi



                             Federal Information
                     Processing Standards Publication 98
                               27 January 1983
                         Announcing the Standard for


                               MESSAGE FORMAT
                                     FOR
                       COMPUTER BASED MESSAGE SYSTEMS



      Federal  Information Processing Standards Publications are issued
      by the National Bureau of Standards pursuant to section 111(f)(2)
      of the Federal Property and Administrative Services Act of  1949,
      as  amended,  Public  Law 89-306 (79 Stat. 1127), Executive Order
      11717 (38 FR 12315, dated May 11, 1973), and Part 6 of  Title  15
      Code of Federal Regulations (CFR).

      Name  of  Standard.  Message  Format  for  Computer Based Message
      Systems (FIPS PUB 98).

      Category of Standard. Software Standard; Interchange Codes, Media
      and Data Files.

      Explanation.  This  standard  separates  information  so  that  a
      Computer  Based  Message  System  can  locate and operate on that
      information (which is found in the fields of messages).  This  is
      the  first of a family of standards which will ensure information
      interchange among Computer Based Message Systems.

      Approving Authority. Secretary of Commerce

      Maintenance Agency. Department of Commerce,  National  Bureau  of
      Standards (Institute for Computer Sciences and Technology).

      Cross Index. Not Applicable.

      Related Documents.


         a. American   National   Standard   Code  for  Information
            Interchange (ASCII), X3.4-1977,FIPS PUBS 1-1.

         b. American National Standard  Code  Extension  Techniques
            for  Use with the 7-bit Coded Character Set of American
            National  Standard   Code   (ASCII)   for   Information
            Interchange, X3.41-1974, FIPS PUB 35.

         c. National  Bureau  of Standards.  Calendar Date. Federal
            Information Processing Standards  Publication  4,  U.S.




                                      1



            Department  of Commerce / National Bureau of Standards,
            November, 1968.

         d. National Bureau of Standards. Data Encryption Standard.
            Federal Information  Processing  Standards  Publication
            46,  U.S.  Department  of  Commerce/National  Bureau of
            Standards, January, 1977.

         e. National Bureau of Standards. Representation  of  Local
            Time  of  the  Day for Information Interchange. Federal
            Information Processing Standards Publication  58,  U.S.
            Department  of Commerce / National Bureau of Standards,
            February 1979.

         f. National  Bureau  of   Standards.   Representation   of
            Universal  Time,  Local  Time Differentials, and United
            States   Time   Zone   References    for    Information
            Interchange.  Federal  Information Processing Standards
            Publication 59, U.S. Department of Commerce /  National
            Bureau of Standards, February, 1979.


      Applicability.  This  message  format standard applies to Federal
      departments  and  agencies  in  their  acquisition  and  use   of
      computer-based  message  systems (CBMS) and services in networked
      systems,   except   for   certain    single-processor    systems.
      Specifically,  the  standard  does not apply to a CBMS if it is a
      stand-alone system which is not  interconnected  with  any  other
      CBMS:  nevertheless, conformance with the standard is recommended
      under these circumstances particularly if there is a  possibility
      that  use  of another central processing unit, or interconnection
      with another system, will be required in the future.  Where a new
      CBMS node is incorporated into an existing network, the  standard
      applies  at  the  interface  between  CBMS's.  In  this instance,
      previously existing nodes may  accommodate  the  standard  either
      through  retrofit  or  by  the use of a translator.  In addition,
      networks  that  are  established  strictly  for  the  purpose  of
      supporting  research  in  computer  science or communications are
      exempt from complying with this standard.

      Subcommittee TC97/SC16  of  the  International  Organization  for
      Standardization   (ISO)  has  developed  a  reference  model  for
      describing communications between "open" systems.  (ISO/TC97/SC16
      DIS7498) This model is known as the ISO Reference Model for  Open
      Systems   Interconnection   (OSI).    It  divides  communications
      protocols   into   seven   layers,    ranging    from    physical
      interconnection   at   the  lowest  layer  to  data  exchange  by
      applications programs at the top.

      The NBS message format deals with data  used  by  an  application
      within  a  system; it is not a protocol.  Messages defined by the




                                      2



      NBS   message   format   would   be  manipulated  by  a  layer  7
      (Application) protocol.

      A message as referenced by the NBS message format is  a  unit  of
      communication from an originator to a recipient, exclusive of any
      message  heading  or  control information (often referred to as a
      message envelope).  An originator  and  recipient  are  typically
      people  but  may  be  roles  or  processes.   A role identifies a
      function within an organization as opposed to an  individual  who
      performs  that  function.  A process refers to a computer process
      that might originate or receive a message.

      Special Information. Certain characteristics distinguish  a  CBMS
      from  other  systems  for  sending  messages.    Originators  and
      recipients  may  be  terminal  users   or   processes   (discrete
      software).    A  system  in  which  the  originator  addresses  a
      particular terminal device rather than a particular recipient  is
      not  considered to be a CBMS.  The recipient's system need not be
      available when the originator sends a message.  The  message  can
      be  stored  in the originator's system or at an intermediate node
      in the network until the recipient's  system  becomes  available.
      In  addition,  a  CBMS  offers  both message creation and message
      processing facilities as part of the system.  A CBMS offers  text
      editing  facilities  to  assist  the user in the preparation of a
      message.   The  recipient  CBMS  stores  the  message  until  the
      recipient  chooses  to  read  it.    Message systems which do not
      provide these minimum functions are not considered CBMS's.

      The intent of the message format standard is to  allow  users  of
      different computer based message systems to send messages to each
      other.    The  standard  does  not  make  demands  on the message
      transfer system except that it transports messages transparently.
      The standard makes some simple demands on the  CBMS.    The  CBMS
      must  recognize  fields  within  the  message,  process fields in
      predetermined ways, create messages  in  the  correct  form,  and
      recognize  and  create  data  elements of messages in the correct
      format.  The standard does not dictate or constrain the  services
      that  the  CBMS  provides for users, or the way that messages are
      stored, represented, manipulated, or presented to the user by the
      CBMS.

      The standard does constrain the format  of  the  message  at  the
      interface  between  systems.   This guarantees that, whatever the
      source of the message, it arrives at the receiving system in  the
      standard   format.      The  message  format  standard  separates
      information into fields so that the CBMS can locate  and  operate
      on  that  information.   The message is converted from the format
      used within the originator's CBMS  to  the  standard  format  (if
      different)  on  leaving  the  originator's  CBMS.  The message is
      converted from the standard format to the format used within  the
      recipient's CBMS (if different) on entering the recipient's CBMS.




                                      3



      Specifications.  Federal  Information Processing Standard (FIPS),
      Message Format for Computer Based Message Systems (affixed).

      Qualifications. None

      Implementation Schedule. All  applicable  equipment  or  services
      ordered  on  or after 24 months from the date of issuance of this
      FIPS PUB, and all CBMS development initiated inhouse on or  after
      12  months  from the date of issuance of this FIPS PUB must be in
      conformance with this standard unless a waiver has been  obtained
      in  accordance  with the procedure described below.  An exception
      to this standard is made when procurement actions  are  into  the
      solicitation phase on the date of issuance of this FIPS PUB.

      Waivers.  Heads  of agencies may request that the requirements of
      this standard be waived in instances  where  it  can  be  clearly
      demonstrated  that  there  are  appreciable  performance  or cost
      advantages to be gained and that the  overall  interests  of  the
      Federal  Government  are  best  served  by granting the requested
      waiver.  Such waiver requests will be reviewed by and are subject
      to the approval of the Secretary of Commerce.  The waiver request
      must address the criteria stated above as the  justification  for
      the waiver.

      Forty-five  days should be allowed for review and response by the
      Secretary of Commerce.  Waiver requests shall be submitted to the
      Secretary of Commerce, Washington, D.C. 20230, and labeled  as  a
      Request   for  a  Waiver  to  a  Federal  Information  Processing
      Standard.  No agency shall take any action to  deviate  from  the
      standard  prior  to  the  receipt  of  a waiver approval from the
      Secretary of Commerce.  No agency  shall  begin  any  process  of
      implementation  or acquisition of non-conforming equipment unless
      it has already obtained such approval.

      Where to Obtain Copies. Either paper or microfiche copies of this
      Federal  Information  Processing  Standard,  including  technical
      specifications,  may  be  purchased  from  the National Technical
      Information  Service  (NTIS)  by  ordering  Federal   Information
      Processing Standard Publication (FIPS-PUB-98), Message Format for
      Computer  Based Message Systems.  Ordering information, including
      prices and delivery alternatives, may be obtained  by  contacting
      the   National   Technical   Information  Service  (NTIS),  U. S.
      Department of Commerce, Springfield,  Virginia  22161,  telephone
      number  (703)  487-4650.    Payment  may  be made by check, money
      order, purchase order, credit card, or deposit account.










                                      4

                                                      Executive Summary

                              EXECUTIVE SUMMARY




           The  message  format  specification addresses the problem of
      exchanging  messages  between  different  computer-based  message
      systems  (CBMSs).    This interchange problem can be addressed on
      several  levels.    One  level  specifies  the  physical   inter-
      connections,  another  specifies  how information travels between
      CBMSs, another specifies  form  and  meaning  of  messages  being
      interchanged.    The  highest  level  specifies  operations  on a
      message.  Each of these levels would be covered  by  a  different
      standard.

           This  message format specification addresses only the issues
      of form and meaning of messages at the points in time  when  they
      are  sent  from  one  CBMS and received by another.  Messages are
      composed of fields, containing different classes of  information.
      These  fields  contain  information about the message originator,
      message recipient, subject matter, precedence and  security,  and
      references  to  previous  messages,  as  well  as the text of the
      message.  Standard formats (syntax) for messages provide a  basis
      for  the  contents  of  messages  generated  by  one  CBMS  to be
      processed by another CBMS.  Standard meanings (semantics) for the
      components of a message facilitate standard interpretation  of  a
      message,  so  that  everyone receiving a message gets the meaning
      intended by its sender.

           Each CBMS that implements this message format  specification
      will  be  compatible  with  any  other  CBMS  that implements the
      specification, provided that the use of optional fields and  data
      elements  is  negotiated  in  advance.    This  ensures  that the
      contents of a message posted by one  CBMS  can  be  received  and
      interpreted by a different CBMS.

           This  message  format  specification has been developed as a
      result of examining CBMSs currently  in  use  in  commercial  and
      research  environments.    Three major design perspectives helped
      shape the message format specification.


        o  Viability.    The  message  format  specification   uses
           concepts  that  already work.  It has been designed with
           implementation concerns in mind.

        o  Compatibility.    The   message   format   specification
           contains concepts from existing CBMSs.  For this reason,
           many CBMS would already contain functions and components
           similar  to  those  required  to  implement  the message
           format specification.




                                      5

                                                      Executive Summary

        o  Extensibility.      This  message  format  specification
           defines a broad range of message content components  and
           requires  only an elementary subset of them.  This means
           that even a very simple CBMS can implement  the  message
           format  specification.  The message format specification
           contains a rich  set  of  optional  components  and,  in
           addition,  mechanisms  for  user  extensions  and future
           extensions to the message format specification.