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Directory Services in Windows Server 2025

Directory services such as Active Directory Domain Services (AD DS) and DNS are the backbone of Windows-based networks. They enable centralized management of users, groups, devices, and resources. Concepts like domains, trees, forests, domain controllers (DCs), trust relationships, and organizational units (OUs) form the structure of AD. By installing AD DS and DNS roles and promoting a server to a DC, organizations can build secure, scalable, and efficient IT infrastructures.

Active DirectoryDomain ControllerDNS

~2 min read • Updated Dec 16, 2025

1. Active Directory Infrastructure


Active Directory is a distributed directory service that organizes and manages network resources in a hierarchical structure. It stores objects such as users, computers, printers, and services, each with unique attributes like SIDs, group memberships, and ACLs. The architecture includes:


  • Domain: Basic unit of administration and security.
  • Tree: Collection of domains in a contiguous namespace.
  • Forest: Highest level, grouping multiple trees.

2. Importance of Active Directory


  • Centralized Management: Manage users and resources from one location.
  • Enhanced Security: Use of SIDs and ACLs to protect resources.
  • Scalability: Seamless integration of new users and devices.
  • Policy Enforcement: Apply Group Policies across the network.

3. Core Protocols Supporting AD


  • LDAP: Standard protocol for querying and managing directory data.
  • Kerberos: Authentication protocol using tickets for secure identity verification.
  • DNS: Resolves domain names to IP addresses and supports AD-specific functions.

4. Tools for Administering AD


  • Active Directory Administrative Center: Manage users, groups, and OUs.
  • Domains and Trusts: Configure trust relationships and domain functional levels.
  • Sites and Services: Manage replication and global catalog servers.
  • PowerShell AD Module: Automate and script AD tasks.

5. Domain Controllers (DCs)


Domain Controllers authenticate users and authorize access to resources. In Windows Server 2025, all DCs share equal responsibility, replacing the old PDC/BDC model with multi-master replication for reliability and scalability.


6. Domains, Trees, and Forests


Domains group users and resources under unified policies. Domains can form Domain Trees with hierarchical parent-child relationships, inheriting policies from parent domains. Multiple trees combine into a Forest, the top-level AD structure.


Conclusion


Understanding AD DS, DNS, Domain Controllers, domains, trees, and forests equips IT professionals to build secure and scalable infrastructures in Windows Server 2025.


Written & researched by Dr. Shahin Siami

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