[Dovecot] OT: parallel connections to the IMAP server

[cl at isbd.net]

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)