How does the Ecessa appliance provide failover in the event one of the WAN links goes down?

Ecessa appliances load balance network sessions by using an intelligent algorithm that selects the WAN link to use based on available bandwidth and utilization. During a WAN outage event, the appliance will ignore the failed link and redirect traffic over the other available WAN link(s). The appliance will continue to monitor the links with line testing to automatically detect when the failed WAN becomes operational at which point it will begin to use it again.

By default, when a WAN becomes operational (the status changes from down to up) the WAN line is available for use immediately, however there instances where the link is unstable and changes status frequently between down/up (sometimes referred to as the WAN "flapping" or "bouncing"). The Delayed Line Status Reporting setting located on the Services page will delay link status changes to overcome this problem. If the WAN remains stable for the configured "Delay X seconds" where "X" is the desired amount of time - default is 10 - then the link status will change from down to up. This setting does not affect the status change if a failure is detected (changing the status from up to down). 

Any sessions that were routed over the WAN during the outage event will not transfer to the other links which will cause those connections to fail. However, each new session will be routed over one of the available WANs and would succeed.