[Kroupware] Re: Questions about Kmail IMAP-client

[Marc Mutz]

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On Friday 21 February 2003 12:56, Paul de Vrieze wrote:
> > You confuse offline IMAP with disconnected IMAP. The first one is
> > using IMAP as a POP3 replacement (ie. fetch'n'delete), while the
> > latter periodically reconnects to the server to sync local cache
> > and remote server.
>
> No, this is actually also offline IMAP. On-line IMAP gets notified by
> the server of updates in the mailfolder. In this respect the
> (non-kroupware) kmail is particularly misbehaved as it uses two
> connections when checking new folders. There is no necessity for that
> at all. Considering autonotification and a well-behaved IMAP server
> (we all know there are too many which aren't) online imap should be
> faster.

OK, to get this straight once and for all (I hope :-):

=2D- begin rfc 1733 excerpt --
   There are three fundamental models of client/server email: offline,
   online, and disconnected use.  IMAP4 can be used in any one of these
   three models.

   The offline model is the most familiar form of client/server email
   today, and is used by protocols such as POP-3 (RFC 1225) and UUCP.
   In this model, a client application periodically connects to a
   server.  It downloads all the pending messages to the client machine
   and deletes these from the server.  Thereafter, all mail processing
   is local to the client.  This model is store-and-forward; it moves
   mail on demand from an intermediate server (maildrop) to a single
   destination machine.

   The online model is most commonly used with remote filesystem
   protocols such as NFS.  In this model, a client application
   manipulates mailbox data on a server machine.  A connection to the
   server is maintained throughout the session.  No mailbox data are
   kept on the client; the client retrieves data from the server as is
   needed.  IMAP4 introduces a form of the online model that requires
   considerably less network bandwidth than a remote filesystem
   protocol, and provides the opportunity for using the server for CPU
   or I/O intensive functions such as parsing and searching.

   The disconnected use model is a hybrid of the offline and online
   models, and is used by protocols such as PCMAIL (RFC 1056).  In this
   model, a client user downloads some set of messages from the server,
   manipulates them offline, then at some later time uploads the
   changes.  The server remains the authoritative repository of the
   messages.  The problems of synchronization (particularly when
   multiple clients are involved) are handled through the means of
   unique identifiers for each message.

   Each of these models have their own strengths and weaknesses:

      Feature                               Offline Online  Disc
      -------                               ------- ------  ----
      Can use multiple clients               NO      YES     YES
      Minimum use of server connect time     YES     NO      YES
      Minimum use of server resources        YES     NO      NO
      Minimum use of client disk resources   NO      YES     NO
      Multiple remote mailboxes              NO      YES     YES
      Fast startup                           NO      YES     NO
      Mail processing when not online        YES     NO      YES

=2D- end rfc 1733 excerpt --


=2D-=20
The DMCA is unconstitutional, but they don't care. Until it's ruled
unconstitutional, they've won. If they can scare software companies,
ISPs, programmers, and T-shirt manufacturers [...] into submission,
they've won for another day. The entertainment industry is fighting a
holding action, and fear, uncertainty, and doubt are their weapons. We
need to win this, and we need to win it quickly. Every day we don't
win is a loss.                 -- Bruce Schneier, Crypto-Gram Aug 2001

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