rfc984.txt

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   efficiently than they could (since users must make changes locally
   and then run the action-processing/synchronization program, rather
   than simply making changes interactively).

   Another important reason for limiting operation to batch mode is that
   it allows a very simple locking scheme to prevent problems raised by
   concurrent state updates.  A user may have several clients; it is
   therefore likely that the repository could get into a variety of
   inconsistent states as different clients try to change the
   repository's global mail state at the same time.  To prevent these
   inconsistencies, a user's mail state is locked as soon as a client
   connects to the repository.  The lock is released when the client
   disconnects from the repository. This locking scheme is simple to
   implement, but makes interactive-mode operation very cumbersome: if a
   user remains constantly connected to the network (i.e. in interactive
   mode), the repository would be unavailable to any of the user's other
   clients for an unacceptable length of time.

8. Conclusions

   Pcmail is now used by a small community of people at the MIT
   Laboratory for Computer Science.  The repository design works well,
   providing a fairly efficient means of storing and maintaining mail
   state for several users.  Members of another research group at LCS
   are currently working on a replicated, scaleable version of the
   repository designed to support a very large community of users with
   high availability.  This repository also uses DMSP and has
   successfully communicated with clients that use the current
   repository implementation.  DMSP therefore seems to be useable over
   several flavors of repository design. The clients, being PCs, are
   unfortunately very limited in the way of resources, making local mail
   state manipulation difficult at times.  Synchronization is also


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RFC 984                                                         May 1986
PCMAIL


   relatively time consuming due to the low performance of the PCs.  The
   "batch-mode" of client operation is very useful for portable
   computers that spend a large percentage of their time unplugged and
   away from a network. It is somewhat less useful for the majority of
   the clients, which are always connected to the network and could make
   good use of an "interactive-mode" state manipulation.











































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RFC 984                                                         May 1986
PCMAIL


I. DMSP Protocol Specification

   Following is a list of DMSP block types and DMSP operations by object
   type.  Again, "=>" marks blocks flowing from client to repository;
   "<=" marks blocks flowing from repository to client.

      General operations:

         => or <= 503 (abort-request) [why:str]
         (no acknowledgement)

         => 504 (start-debug) []
         <= 500 (ok) [] |
            501 (failure) [why:str]

         => 505 (end-debug) []
         <= 500 (ok) []

         => 506 (send-version) [version:card]
         <= 500 (ok) [] |
            501 (failure) [why:str]

         => 507 (log-message) [message:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]

         => 508 (send-message) [message:seq[str]]
         <= 500 (ok) [] |
            501 (failure) [why:str]

      User operations:

         => 600 (login) [name:str, password:str,
                         client:str, create-client-object?:bool
                         batch-mode-flag:bool]
         <= 500 (ok) [] |
            501 (failure) [why:str] |
            705 (force-client-reset) []

         => 601 (logout) []
         <= 500 (ok) []

         => 602 (add-user) [name:str, password:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]




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         => 603 (remove-user) [user:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]

         => 604 (set-password) [old:str, new:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]

      Client operations:

         => 700 (list-clients) []
         <= 701 (client-list) [client-list:seq[
                               rec[name:str], status:card]]

         => 702 (add-client) [client:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]

         => 703 (remove-client) [client:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]

         => 704 (reset-client) [client:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]

      Mailbox operations:

         => 800 (list-mailboxes) []
         <= 801 (mailbox-list) [mailbox-list:seq[
                                rec[mailbox:str,
                                    next-uid:lcard,
                                    num-msgs:card,
                                    num-unseen-msgs:card]]]

         => 802 (add-mailbox) [mailbox:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]

         => 803 (remove-mailbox) [mailbox:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]

         => 808 (expunge-mailbox) [mailbox:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]



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RFC 984                                                         May 1986
PCMAIL


         => 809 (reset-mailbox) [mailbox:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]

      Address operations:

         => 804 (list-addresses) [mailbox:str]
         <= 501 (failure) [why:str] |
            805 (address-list) [address-list:seq[str]]

         => 806 (add-address) [mailbox:str, address:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]

         => 807 (remove-address) [mailbox:str, address:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]

      Message operations:

         => 1100 (get-descriptor-flags) [mailbox:str, uid:lcard]
         <= 1101 (descriptor-flags) [flags:seq[bool]] |
            501 (failure) [why:str]

         => 1102 (get-descriptors) [mailbox:str,
                                    low-uid:lcard,
                                    high-uid:lcard]
         <= 501 (failure) [why:str] |
            1103 (descriptor-list) [descriptor-list:seq[
                   ch[
                     expunged[uid:lcard],
                     descriptor[rec[uid:lcard,
                                    flags:seq[bool],
                                    from-field:str,
                                    to-field:str,
                                    date-field:str,
                                    subject-field:str,
                                    nun-bytes:lcard,
                                    num-lines:lcard]
                          ]]]]









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RFC 984                                                         May 1986
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         => 1105 (get-changed-descriptors) [mailbox:str,
                                            max-to-send:card]
         <= 501 (failure) [why:str] |
            1103 (descriptor-list) [descriptor-list:seq[
                   ch[
                     expunged[uid:lcard],
                     descriptor[rec[uid:lcard,
                                    flags:seq[bool],
                                    from-field:str,
                                    to-field:str,
                                    date-field:str,
                                    subject-field:str,
                                    num-bytes:lcard,
                                    num-lines:lcard]
                         ]]]]

         => 1106 (reset-changed-descriptors) [
                         mailbox:str,
                         start-uid:lcard,
                         end-uid:lcard]
         <= 500 (ok) [] |
            501 (failure) [why:str]

         => 1107 (get-message-text) [mailbox:str,
                                     uid:lcard]
         <= 501 (failure) [why:str] |
            1110 (message) [message:seq[str]]

         => 1108 (print-message) [mailbox:str,
                                  uid:lcard,
                                  printer-name:str]
         <= 500 (ok) [] |
            501 (failure) [why:str]

         => 1109 (set-flag) [mailbox:str,
                             uid:lcard,
                             flag-number:card,
                             flag-setting:bool]
         <= 500 (ok) [] |
            501 (failure) [why:str]

         => 1111 copy-message[source-mailbox:str,
                              target-mailbox:str,
                              source-uid:lcard]
         <= 500 (ok) [] |
            501 (failure) [why:str]



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RFC 984                                                         May 1986
PCMAIL


   DMSP block types by number

      General block types