On 9/19/2011 7:36 AM, Tom Clark wrote:
Hi Paul,
It's coming from the same IP address through his ADSL. Hence he gets the
problem with max_userip_connections.
I think I tracked down the problem. He's been using K9 mail which seems to
have a problem where it doesn't release a connection and has 1 connection
per subscribed folder....
The reasoning behind the multiple socket communication design in the
IMAP protocol is flawed, thus we end up with problems like yours, and
others. It may have looked good on the white board but it doesn't seem
to add benefit in production--only add problems. At least from an SA's
perspective. Just about every other modern internet protocol gets by
with a single socket, and many of those applications are more complex
than IMAP.
Multiple virtual channels are a good idea at the data link layer of WAN
communications links, and work well there. They're a lousy idea at the
application layer, however, as the IMAP protocol clearly demonstrates.
Everything IMAP does over multiple sockets could have been accomplished
over a single socket, with no noticeable decrease in performance, but
with fewer SA headaches and fewer server resources consumed.
I eagerly await a successor to the current version of IMAP, which will
hopefully do away with this problematic, unnecessary, multiple socket
nonsense. It may be a long wait, unfortunately...
--
Stan
