What is a requirement for setting up a failover cluster on Windows Server?

Setting up a failover cluster on Windows Server requires Active Directory for several reasons. Firstly, Active Directory provides the necessary directory services that allow the cluster nodes to communicate effectively and authenticate each other. The nodes in a failover cluster need to be part of the same Active Directory domain to ensure that they can access shared resources and coordinate failover operations.

Active Directory also manages the cluster's identity and helps in maintaining the high availability of services by keeping track of which resources are available on which node. This allows for seamless transitions when one node fails, ensuring that services remain operational by moving the workloads to another node in the cluster.

While the other choices involve technologies and functions that may complement certain aspects of a computing environment, they are not essential for the fundamental operations required to establish a failover cluster. Network Access Control pertains more to security measures, virtualization technology relates to running virtual machines, and Server Message Block is a network file sharing protocol that is not specifically required for setting up a cluster.