Directors can be used to authenticate Lync Server user requests, but do not home user accounts, or provide presence or conferencing services. Directors are most useful in deployments that enable external user access, where the Director can authenticate requests before sending them on to internal servers. Directors can also improve performance in organizations with multiple Front End pools.

Director Server Scalability

For performance, one physical Director should be deployed for every 15,000 users who will access a site remotely. At a minimum it is recommend deploying two Directors for high availability.