ietf-smtp
[Top] [All Lists]

Re: MS vs. pop and imap (alternate response)

2004-05-30 11:48:30

Hi Pete,

--On Sunday, May 30, 2004 01:06:12 PM -0500 Pete Resnick <presnick(_at_)qualcomm(_dot_)com> wrote:

1. How do we model the components and downstream interactions of srv1
and pc1:

       |
      MTA
       |
  +--<srv1>--+
  |          |
  | messages |
  |          |
  +----------+
       |
      <pc1>

pc1 does not retain any messages. Repeated readings of the same
message require repeated retrievals from srv1.

srv1 - MDA
messages - MS
pc1 - MUA
line between MTA and srv1 - SMTP
line between messages and pc1 - POP or IMAP or local access

This would make for an amazingly stupid POP client, a somewhat stupid
IMAP client, and a use of a local access client that would piss-off some
sys admins.

No! There is a well defined usage case for this: kiosk clients that do not leave messages behind in a local cache. This is vital for any public access email stations. Often people just get by with webmail in such cases but there is no reason why a full blown desktop client can't offer the same and thus provide the richer desktop GUI interaction with email over the limited GUI a browser can provide.

2. How do we model the components and downstream interactions of srv2
and pc2:

       |
      MTA
       |
  +--<srv1>--+
  |          |
  | messages |
  |          |
  +----------+
       |
  +--<pc1>---+
  |          |
  | messages |
  |          |
  +----------+

Messages are retained on pc1 and not on srv1.

srv1 - MDA
messages under srv1 - MS
pc1 - MUA
messages under pc1 - MUA's local cache of messages (same for /bin/mail
messages in ~/Mail, POP client's mailboxes, or IMAP client's cached data)
line between MTA and srv1 - SMTP
line between messages and pc1 - POP or IMAP or local access

These two implementations/configurations are not architecturally
different.

There is a third option: messages kept on both server and client with synchronisation.

In fact this is what I call the 'three modes of IMAP':

Online mode: client has no local cache of data, always re-fetches messages from the server. This effectively implements kiosk mode.

Offline mode: client does 'pop-over-imap' and pulls all messages down to the client cache and deletes from the server. Whilst that is a viable use of IMAP, its a pretty pointless one, and I don't know of any clients that actually behave that way.

Disconnected mode: client maintains a cache of messages that are on the server and synchronizes changes between the two. The client may really be in a situation where it connects/disconnects from the network, or it may be connected but uses the local cache to speed up the 'online mode' where local caching is allowed.



--
Cyrus Daboo


<Prev in Thread] Current Thread [Next in Thread>