[Dovecot] OT: parallel connections to the IMAP server

cl at isbd.net cl at isbd.net
Fri Aug 11 14:16:56 EEST 2006

On Fri, Aug 11, 2006 at 01:09:03PM +0200, Jan Kundrát wrote:
> cl at isbd.net wrote:
> >> Well, speaking from the client's perspective, it makes perfect sense to
> >> have five idling connections to five mailboxes that are expected to
> >> receive new mails rather than doing periodical STATUS polls on them. No
> >> client should rely on such a behavior, though, and a lot of people would
> >> probably say that it's insane to open 100 concurrent connections. I'd
> >> agree with them :)
> >>
> > Another issue with this problem is that it should be totally hidden
> > from the user.  I've seen this happening with Thunderbird which, if I
> > remember correctly, defaults to a maximum of five connections and even
> > this often conflicts with ISP (and other) IMAP setups.  The result is
> > an error message which 99% of users can't understand and can't fix.
> > 
> > The MUA and the IMAP server should 'negotiate' a mutually acceptable
> > number of ports.
> Any ideas about the proper negotiation algorithm? The easiest way would
> be to try opening as many connections as desired, until the server
> starts killing them. That won't be much robust, though, as the server
> can close the connection for variety of other reasons.
> The best way that comes to my mind is limiting the number of parallel
> connections in client's config.
Except that there's no one value that would be right for all
situations - so then how does the user know what value to set?

What I was suggesting probably isn't in the IMAP RFC (if that's what's
driving all this).  One needs the IMAP server to tell the MUA how many
simultaneous connections it will allow.

Chris Green (chris at halon.org.uk)

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