On MSMQ independent clients, the MSMQ service sends out a broadcast when it starts, and monitors all replies. If a site controller other than the independent client's current site controller replies, and if the new site controller can communicate with the site controller in the independent client's original site, the independent client connects to the new site.
If you have more than one site controller in a broadcast segment (for example, in an MSMQ lab) more than one site controller can reply to the independent client's broadcast. If one of the site controllers that replies is the controller for the independent client's current site, the independent client does not connect to another site.
If the site controller for the independent client's current site is offline, the independent client does not move to a new site.