rfc754.txt

RFC 相关的技术文档

RFC 754                                                     6 April 1979
Out-of-Net Host Addresses for Mail



      A problem arises about acknowledgements of mail receipt.  First
      the normal ARPANET message delivery mechanisms will say the mail
      is delivered when the FTP server puts the mail in the file for the
      routing deamon to examine.  Second if the routing deamon discovers
      an message is to be forwarded to a nonexistent user, care must be
      used to notify the original sender unambiguously.

      Changes:

         all composition programs

   B) GLOBAL NAMES INSIDE

      Example:

         Outside:  [---].NSW-MAIL@FWDR

         Inside:   To:       Joe@NSW, Bill@ISIA, Fred@NSW
                   CC:       Mike@NSW, Paul@NSW, John@ISIB
                   From:     Sam@ISIB

      Every mail composition program has to know that NSW is a very
      special host name, for which it uses a different mailbox argument
      and sends to the FWDR host.  The FTP server naturally puts all the
      NSW mail into a single mailbox file which the routing deamon
      examines.  The "answer" command works fine.  The routing deamon
      has to look at the inside header to determine where to forward the
      messages.  It has to check the "To:" and "CC:" lines.

      The sending programs must also send just one copy to the FWDR and
      routing deamon, the routing deamon will send copies to all NSW
      users it finds.  If this is not done, the deamon would have
      difficulty avoiding sending multiple copies to each destination
      user.  This is an advantage in terms of number of transmissions.

      A problem arises about acknowledgements of mail receipt.  First
      the normal ARPANET message delivery mechanisms will say the mail
      is delivered when the FTP server puts the mail in the file for the
      routing deamon to examine.  Second if the routing deamon discovers
      an message is to be forwarded to a nonexistent user, care must be
      used to notify the original sender unambiguously.

      Changes:

         all sending programs





Postel                                                          [page 6]


RFC 754                                                     6 April 1979
Out-of-Net Host Addresses for Mail



   C) GLOBAL NAMES OUTSIDE

      Example:

         Outside:  [---].Joe@NSW

         Inside:   To:       Joe@NSW, Bill@ISIA, Fred@NSW
                   CC:       Mike@NSW, Paul@NSW, John@ISIB
                   From:     Sam@ISIB

      No changes to mail composition or processing programs are needed.
      The FTP server has to put all the NSW users mail into a single
      mailbox file which the routing deamon examines.  The cheapest way
      to do this is to put all the names of the NSW users in the ARPANET
      user forwarding file with the same destination ARPANET mailbox.
      This means the local users of the FWDR host and the users in the
      destination networks share the name space for user names.  The
      routing deamon has to look at the inside header to determine where
      to forward the messages.  It has to check the "To:" and "CC:"
      lines.

      This appears to be the solution with the minimum change to
      existing software.  The "answer" command works fine.

      There is a problem with the name space, for example, if ISIA
      serves as FWDR host, then Fred@ISI and Fred@NSW cannot co-exist.
      Further, there is the database update problem.  Every time a new
      user is added to NSW or any of the hosts in any of the nets that
      the FWDR host serves the forwarding file at the FWDR host has to
      be updated.  The names added have to be unique so all user names
      assigned in NSW and all the hosts on all the networks served by
      the same FWDR host have to be oked by the "forwarding file data
      base administrator" before they can actually be used.  Also note
      that Fred@NSW and Fred@PRNET cannot be routed through the same
      FWDR host.

      This doesn't work too well, if the sending programs are not
      changed they will send one copy of this message for each NSW user
      and all these copies will end up in the file to be examined by the
      routing deamon.  If the FTP server code is not changed the outside
      information will be lost and the routing deamon will have no idea
      which NSW user this copy is for.  To do the job right with the
      information available the routing deamon would have to keep a
      substantial record about each message it handled checking to see
      if it received for, and send a copy to, each intended destination
      user.




Postel                                                          [page 7]


RFC 754                                                     6 April 1979
Out-of-Net Host Addresses for Mail



      A problem arises about acknowledgements of mail receipt.  First
      the normal ARPANET message delivery mechanisms will say the mail
      is delivered when the FTP server puts the mail in the file for the
      routing deamon to examine.  Second if the routing deamon discovers
      an message is to be forwarded to a nonexistent user, care must be
      used to notify the original sender unambiguously.

      Changes:

         ARPANET user forwarding file at FWDR host

   D) STRUCTURED NAMES

      Example:

         Outside:  [---].NSW-Joe@NSW

         Inside:   To:       NSW-Joe@NSW, Bill@ISIA, NSW-Fred@NSW
                   CC:       NSW-Mike@NSW, NSW-Paul@NSW, John@ISIB
                   From:     Sam@ISIB

      No changes to mail composition or processing programs are needed.
      The FTP server has to put all the NSW-x users mail into a single
      file which the routing deamon examines.  The FTP server can do
      this on the recognition of the "NSW-" prefix without knowing all
      the legal individual users.  In addition the FTP server puts the
      mailbox argument into the file with the message.  This is
      necessary to avoid the loss of the "outside" information.  The
      routing deamon can then look at the mailbox argument to determine
      where to forward the messages.  It need not look at the inside of
      the message at all.  The "answer" command works fine.

      A problem arises about acknowledgements of mail receipt.  First
      the normal ARPANET message delivery mechanisms will say the mail
      is delivered when the FTP server puts the mail in the file for the
      routing deamon to examine.  However, if the routing deamon
      discovers an message is to be forwarded to a nonexistent user, the
      deamon can easily tell the original sender the exact destination
      user that is unreachable.

      Changes:

         FTP server at FWDR host







Postel                                                          [page 8]


RFC 754                                                     6 April 1979
Out-of-Net Host Addresses for Mail



Summary:

                                 A         B        C        D
                               Single    Global   Global   Structured
                               Mailbox   Names    Names    Names
                                         Inside   Outside

   Criteria:

      1) What changes?         Composer  Composer None      FTP server

      2) How many?             100       100      0         1

      3) Routing information?  New       Old      Old       Old
                               Inside    Inside   Inside    Outside

      4) "Answer" command?     Changes   Same     Same      Same

      5) ARPANET name space    1 per     1 per    1 per     1 per
         use?                  FWDR      FWDR     user      user

   Goals:

      1) Software Change       Bad       Bad      Good      Good

      2) User Acceptance       Bad       Good     Good      Poor

      3) Future Compatibility  Bad       Poor     Poor      Fair

      4) Transition Software   Fair      Good     Bad       Good

   Conclusions:

      Solution D is recommended.

      Only solution D is based on the use of strictly "outside"
      information.  Please note that the existing ARPANET message
      DELIVERY system is based strictly on the use of "outside"
      information only.  Also note that the problems that keep coming up
      in ARPANET message processing & composition programs have to do
      with the different possibilities for syntax (and semanitcs) of the
      "inside" information.  This is a major advantage of solution D.








Postel                                                          [page 9]


RFC 754                                                     6 April 1979
Out-of-Net Host Addresses for Mail



      Please note that the syntax NET-USER@FWDR in the examples is not
      the only form that could be used.  Any of the following (or even
      others) would be fine:

         Net-User@FWDR       User-Net@FWDR
         Net/User@FWDR       User/Net@FWDR
         Net.User@FWDR       User.Net@FWDR
         Net.and.User@FWDR   User.on.Net@FWDR










































Postel                                                         [page 10]