I have two IDV servers (replicated, IDV1 & IDV2) and would like to do
bi-directional synchronization with two AUTH servers (replicated, AUTH1
& AUTH2).

From the information above, how many NDS2NDS drivers do I need to have
if I want the driver to support these scenarios:

1. Normal: IDV1 <-> AUTH1
2. IDV1 is down: IDV2 <-> AUTH1
3. AUTH1 is donw: IDV1 <-> AUTH2
4. IDV1 & AUTH1 are down: IDV2 <-> AUTH2

I confuse because it allows single value in Authentication Context in
Authentication Parameters.