From MySQL .NET Connector 6.0 a new connection string parameter has been added. The new parameter are called keepAlive, and are used to indicated server ping intervals in seconds.
This parameter are used to ensure database connection aren't dropped, fx. by firewalls due to inactivity. If the connection are dropped, the connection timeout are not obeyed.
A longer discussion and explanation can be found in this bug report, http://bugs.mysql.com/bug.php?id=40684. Currently the parameter aren't documented anywhere in the online .NET Connector documentation.