[Dovecot] How to define ldap connection idle

[Aliet Santiesteban Sifontes]

I'm having a problem with dovecot ldap connection when ldap server is in
another firewall zone, firewall kills the ldap connection after a
determined period of inactivity, this is good from the firewall point of
view but is bad for dovecot because it never knows the connections has been
dropped, this creates longs timeouts in dovecot and finally it reconnects,
meanwhile many users fails to authenticate, I have seen this kind of post
in the list for a while but can't find a solution for it, so my question is
how to define a idle ldap time in dovecot so it can reconnect before the
firewall has dropped the connection or just close the connection under
inactivity so when a user authenticate doesn't fails for a while until
dovecot detects that the connection has hanged. Is this a feature request
or there is already a configuration for this???
Thank's in advance and congrats tu Timo for this great app.