In the Authenticated Servers section for user sources, we can change the order of the our AD servers for each Zenworks primary server (move up/down). How is this order evaluated?

Is it a round-robin style, or quickest to respond? .... ?
Does it attempt to connect to one and if fails attempts the next? If so does it do it bottom-up or top-down?

We just can't figure out how the order is affecting the ldap lookups coming from certain primary servers. There is no help for this page (it seems to miss out the Authenticated Servers section). It appears (for us) that the last AD server in the order is the one that is getting the most requests. We don't see this as expected.