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Active Directory Domain Services Primer

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Microsoft MVPs discuss the traditional Active Directory service, Active Directory Domain Services (AD DS), and touch on the information needed to understand what AD DS is and how it has become the most common enterprise directory platform in use today.

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This chapter is from the book

Microsoft’s Active Directory technologies have come a long way since their original release with Windows 2000 Server. From a single product referred to simply as Active Directory, or AD, Windows Server 2016 now encompasses a total of five separate Active Directory technologies. Each of these technologies is similar—they all exist to supply directory services and to serve as a platform for future integration of Microsoft technologies. The additional four Active Directory services roles in Windows Server 2016 are Active Directory Lightweight Directory Services (AD LDS), Active Directory Federation Services (AD FS), Active Directory Certificate Services (AD CS), and Active Directory Rights Management Services (AD RMS).

The focus of this chapter is on the traditional Active Directory service, Active Directory Domain Services (AD DS), and touches on the information needed to understand what AD DS is and how it has become the most common enterprise directory platform in use today. This chapter initially focuses on describing a history of directory services in general. It then proceeds to give a primer on AD DS itself as a technology. Finally, specific changes made to Active Directory technologies in general are outlined at the end of the chapter, including all new improvements introduced in the Windows Server 2016 version of AD DS. The additional Active Directory services outside of AD DS are covered in subsequent chapters, primarily in Chapter 8, “Creating Federated Forests and Lightweight Directories.”

The Evolution of Directory Services

Directory services have existed in one form or another since the early days of computing to provide basic lookup and authentication functionality for enterprise network implementations. A directory service provides detailed information about a user or object in a network, much in the same way that a phone book is used to look up a telephone number for a provided name. For example, a user object in a directory service can store the phone number, email address, department name, and as many other attributes as an administrator desires.

Directory services are commonly referred to as the white pages of a network. They provide user and object definition and administration. Early electronic directories were developed soon after the invention of the digital computer and were used for user authentication and to control access to resources. With the growth of the Internet and the increase in the use of computers for collaboration, the use of directories expanded to include basic contact information about users. Examples of early directories included MVS PROFS (IBM), Grapevine’s Registration Database, and WHOIS.

Application-specific directory services soon arose to address the specific addressing and contact-lookup needs of each product. These directories were accessible only via proprietary access methods and were limited in scope. Applications utilizing these types of directories were programs such as Novell GroupWise Directory, Lotus Notes, and the UNIX sendmail /etc/aliases file.

The further development of large-scale enterprise directory services was spearheaded by Novell with the release of Novell Directory Services (NDS) in the early 1990s. It was adopted by NetWare organizations and eventually was expanded to include support for mixed NetWare/NT environments. The flat, unwieldy structure of NT domains and the lack of synchronization and collaboration between the two environments led many organizations to adopt NDS as a directory service implementation. It was these specific deficiencies in NT that Microsoft addressed with the introduction of AD DS.

The development of the Lightweight Directory Access Protocol (LDAP) corresponded with the growth of the Internet and a need for greater collaboration and standardization. This nonproprietary method of accessing and modifying directory information that fully utilized TCP/IP was determined to be robust and functional, and new directory services implementations were written to utilize this protocol. AD DS itself was specifically designed to conform to the LDAP standard.

Reviewing the Original Microsoft Directory Systems

Exchange Server 5.5 ran its own directory service as part of its email environment. In fact, AD DS took many of its key design components from the original Exchange directory service. For example, the AD DS database uses the same Jet database format as Exchange 5.5 and the site replication topology is similar in many ways.

Several other Microsoft applications ran their own directory services, namely Internet Information Server and Site Server. However, each directory service was separate from the others, and integration was not very tight between the different implementations.

Outlining the Key Features of Active Directory Domain Services

Five key components are central to AD DS’s functionality. As compatibility with Internet standards has become required for new directory services, the existing implementations have adjusted and focused on these areas:

  • TCP/IP compatibility—Unlike some of the original proprietary protocols such as IPX/SPX and NetBEUI, the Transmission Control Protocol/Internet Protocol (TCP/IP) was designed to be cross-platform. The subsequent adoption of TCP/IP as an Internet standard for computer communications has propelled it to the forefront of the protocol world and essentially made it a requirement for enterprise operating systems. AD DS and Windows Server 2016, like all previous versions, utilize the TCP/IP protocol stack as their primary method of communications.

  • Lightweight Directory Access Protocol support—LDAP has emerged as the standard Internet directory protocol and is used to update and query data within the directory. AD DS directly supports LDAP.

  • Domain name system (DNS) support—DNS was created out of a need to translate simplified names that can be understood by humans (such as www.cco.com) into an IP address that is understood by a computer (such as The AD DS structure supports and effectively requires DNS to function properly.

  • Security support—Internet standards-based security support is vital to the smooth functioning of an environment that is essentially connected to millions of computers around the world. Lack of strong security is an invitation to be hacked, and Windows Server 2016 and AD DS have taken security to greater levels. Support for IP Security (IPsec), Kerberos, certificate authorities, and Secure Sockets Layer (SSL) encryption is built in to Windows Server 2016 and AD DS.

  • Ease of administration—Although often overlooked in powerful directory services implementations, the ease in which the environment is administered and configured directly affects the overall costs associated with its use. AD DS and Windows Server 2016 are specifically designed for ease of use to lessen the learning curve associated with the use of a new environment. Windows Server 2016 also enhanced AD DS administration with the introduction of the Active Directory Administration Center, Active Directory Web Services, and an Active Directory module for Windows PowerShell command-line administration that has been greatly improved from the one originally included in Windows Server 2008, Windows Server 2008 R2, and Windows Server 2012 and Windows Server 2012 R2. PowerShell support in Windows Server 2016 AD DS has been significantly extended over earlier versions. You can now fully troubleshoot and completely automate provisioning of domain controllers and entire forests from the command line. This was essential with the arrival of the core implementation of the server, and now Nano server, both of which can be enrolled in directory services from the command-line interface. In addition, Windows Server 2016 also allows for better domain controller virtualization support, a concept that has been further expanded in this version. We will explore it more fully in this section of the book.

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