What directory service is used with Windows domain?

Active Directory is the directory service used with Windows domains, serving as a critical component for managing network resources in a Windows environment. It provides several key functions including user authentication, authorization, and management of various resources such as computers, users, and services.

Active Directory utilizes a hierarchical structure that organizes resources in a domain-based model, allowing for a centralized management and easier access control across an entire organization. This also supports group policies to enforce security settings and configurations across all machines in the domain.

In contrast, while LDAP (Lightweight Directory Access Protocol) is a protocol that can be used for accessing directory information services, it is not a directory service itself but rather a means of interacting with one, such as Active Directory. Novell Directory Services and Oracle Directory Services are also directory services, but they are not specifically designed for or integrated with Windows domains, making them less relevant in this context.

Thus, Active Directory stands out as the primary and most commonly used directory service specifically designed to work within Windows environments, which is why it is the correct answer.