To recap, these tasks should be performed to accomplish directory coexistence:
Identify external data sources and elements that need to coexist.
Identify the desired type of synchronization.
Determine the desired frequency of synchronization.
Determine the sensitivity of synchronized data.
Evaluate coexistence implementation options.
Consider performance implications on the directory service.
Design and implement a coexistence solution.
Monitor coexistence, and take action when you find a problem.