• Chapter 1. Installing and Configuring Windows Server 2003
  • software development Company Server 2003
  • Chapter 1. Installing and Configuring Windows Server 2003
  • New Features in Windows Server 2003
  • Best Practices
  • Moving Forward
  • Version Comparisons
  • Hardware Recommendations
  • Installation Checklist
  • Functional Overview of Windows Server 2003 Setup
  • Installing Windows Server 2003
  • Post Setup Configurations
  • Functional Description of the Windows Server 2003 Boot Process
  • Correcting Common Setup Problems
  • Chapter 2. Performing Upgrades and Automated Installations
  • New Features in Windows Server 2003
  • NT4 Upgrade Functional Overview
  • Upgrading an NT4 or Windows 2000 Server
  • Automating Windows Server 2003 Deployments
  • Moving Forward
  • Chapter 3. Adding Hardware
  • New Features in Windows Server 2003
  • Functional Description of Windows Server 2003 Architecture
  • Overview of Windows Server 2003 Plug and Play
  • Installing and Configuring Devices
  • Troubleshooting New Devices
  • Moving Forward
  • Chapter 4. Managing NetBIOS Name Resolution
  • New Features in Windows Server 2003
  • Moving Forward
  • Overview of Windows Server 2003 Networking
  • Name Resolution and Network Services
  • Network Diagnostic Utilities
  • Resolving NetBIOS Names Using Broadcasts
  • Resolving NetBIOS Names Using Lmhosts
  • Resolving NetBIOS Names Using WINS
  • Managing WINS
  • Disabling NetBIOS-over-TCP/IP Name Resolution
  • Chapter 5. Managing DNS
  • New Features in Windows Server 2003
  • Configuring a Caching-Only Server
  • Configuring a DNS Server to Use a Forwarder
  • Managing Dynamic DNS
  • Configuring Advanced DNS Server Parameters
  • Examining Zones with Nslookup
  • Command-Line Management of DNS
  • Configuring DHCP to Support DNS
  • Moving Forward
  • Overview of DNS Domain Structure
  • Functional Description of DNS Query Handling
  • Designing DNS Domains
  • Active Directory Integration
  • Configuring DNS Clients
  • Installing and Configuring DNS Servers
  • Configuring Secondary DNS Servers
  • Integrating DNS Zones into Active Directory
  • Chapter 6. Understanding Active Directory Services
  • New Features in Windows Server 2003
  • Active Directory Support Files
  • Active Directory Utilities
  • Bulk Imports and Exports
  • Moving Forward
  • Limitations of Classic NT Security
  • Directory Service Components
  • Brief History of Directory Services
  • X.500 Overview
  • LDAP Information Model
  • LDAP Namespace Structure
  • Active Directory Namespace Structure
  • Active Directory Schema
  • Chapter 7. Managing Active Directory Replication
  • New Features in Windows Server 2003
  • Replication Overview
  • Detailed Replication Transaction Descriptions
  • Designing Site Architectures
  • Configuring Inter-site Replication
  • Controlling Replication Parameters
  • Special Replication Operations
  • Troubleshooting Replication Problems
  • Moving Forward
  • Chapter 8. Designing Windows Server 2003 Domains
  • New Features in Windows Server 2003
  • Design Objectives
  • DNS and Active Directory Namespaces
  • Domain Design Strategies
  • Strategies for OU Design
  • Flexible Single Master Operations
  • Domain Controller Placement
  • Moving Forward
  • Chapter 9. Deploying Windows Server 2003 Domains
  • New Features in Windows Server 2003
  • Preparing for an NT Domain Upgrade
  • In-Place Upgrade of an NT4 Domain
  • In-Place Upgrade of a Windows 2000 Forest
  • Migrating from NT and Windows 2000 Domains to Windows Server 2003
  • Additional Domain Operations
  • Moving Forward
  • Chapter 10. Active Directory Maintenance
  • New Features in Windows Server 2003
  • Loss of a DNS Server
  • Loss of a Domain Controller
  • Loss of Key Replication Components
  • Backing Up the Directory
  • Performing Directory Maintenance
  • Moving Forward
  • Chapter 11. Understanding Network Access Security and Kerberos
  • New Features in Windows Server 2003
  • Windows Server 2003 Security Architecture
  • Security Components
  • Password Security
  • Authentication
  • Analysis of Kerberos Transactions
  • MITv5 Kerberos Interoperability
  • Security Auditing
  • Moving Forward
  • Chapter 12. Managing Group Policies
  • New Features in Windows Server 2003
  • Group Policy Operational Overview
  • Managing Individual Group Policy Types
  • Moving Forward
  • Chapter 13. Managing Active Directory Security
  • New Features in Windows Server 2003
  • Overview of Active Directory Security
  • Using Groups to Manage Active Directory Objects
  • Service Accounts
  • Using the Secondary Logon Service and RunAs
  • Using WMI for Active Directory Event Notification
  • Moving Forward
  • Chapter 14. Configuring Data Storage
  • New Features in Windows Server 2003
  • Functional Description of Windows Server 2003 Data Storage
  • Performing Disk Operations on IA32 Systems
  • Recovering Failed Fault Tolerant Disks
  • Working with GPT Disks
  • Moving Forward
  • Chapter 15. Managing File Systems
  • New Features in Windows Server 2003
  • Overview of Windows Server 2003 File Systems
  • NTFS Attributes
  • Link Tracking Service
  • Reparse Points
  • File System Recovery and Fault Tolerance
  • Quotas
  • File System Operations
  • Moving Forward
  • Chapter 16. Managing Shared Resources
  • New Features in Windows Server 2003
  • Functional Description of Windows Resource Sharing
  • Configuring File Sharing
  • Connecting to Shared Folders
  • Resource Sharing Using the Distributed File System (Dfs)
  • Printer Sharing
  • Configuring Windows Server 2003 Clients to Print
  • Managing Print Services
  • Moving Forward
  • Chapter 17. Managing File Encryption
  • New Features in Windows Server 2003
  • File Encryption Functional Description
  • Certificate Management
  • Encrypted File Recovery
  • Encrypting Server-Based Files
  • EFS File Transactions and WebDAV
  • Special EFS Guidelines
  • EFS Procedures
  • Moving Forward
  • Chapter 18. Managing a Public Key Infrastructure
  • New Features in Windows Server 2003
  • Moving Forward
  • PKI Goals
  • Cryptographic Elements in Windows Server 2003
  • Public/Private Key Services
  • Certificates
  • Certification Authorities
  • Certificate Enrollment
  • Key Archival and Recovery
  • Command-Line PKI Tools
  • Chapter 19. Managing the User Operating Environment
  • New Features in Windows Server 2003
  • Side-by-Side Assemblies
  • User State Migration
  • Managing Folder Redirection
  • Creating and Managing Home Directories
  • Managing Offline Files
  • Managing Servers via Remote Desktop
  • Moving Forward
  • Chapter 20. Managing Remote Access and Internet Routing
  • New Features in Windows Server 2003
  • Configuring a Network Bridge
  • Configuring Virtual Private Network Connections
  • Configuring Internet Authentication Services (IAS)
  • Moving Forward
  • Functional Description of WAN Device Support
  • PPP Authentication
  • NT4 RAS Servers and Active Directory Domains
  • Deploying Smart Cards for Remote Access
  • Installing and Configuring Modems
  • Configuring a Remote Access Server
  • Configuring a Demand-Dial Router
  • Configuring an Internet Gateway Using NAT
  • Chapter 21. Recovering from System Failures
  • New Features in Windows Server 2003
  • Functional Description Ntbackup
  • Backup and Restore Operations
  • Recovering from Blue Screen Stops
  • Using Emergency Management Services (EMS)
  • Using Safe Mode
  • Restoring Functionality with the Last Known Good Configuration
  • Recovery Console
  • Moving Forward
  • Who Should Read This Book
  • Who This Book Is Not For
  • Conventions
  • Acknowledgments
  • About the Author
  • About the Technical Reviewers
  • Index
  • Index A
  • Index B
  • Index C
  • Index D
  • Index E
  • Index F
  • Index G
  • Index H
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  • Preface
  • Previous Section Next Section

    LDAP Information Model

    A directory service may be a bit fancier than the database you use to tally the overtime pay you've lost since taking your salaried administrator position a few years back, but the principles of operation are pretty much the same.

    Object-Oriented Database

    In X.500 terminology, the directory service database is called a Directory Information Base (DIB). If you think of an old-style library card catalog system as a kind of directory service, one of those big oak cabinets with rows of drawers would be a DIB.

    The X.500 directory service structure was developed at a time when object-oriented databases represented leading-edge technology. If your only exposure to database technology has been more modern relational databases, the design constraints of an object database can look a little strange.

    In an object-oriented database, each record (object) occupies a unique position in a hierarchical namespace. The object's name and path traces its origins to the top of the namespace, in much the same way that a Daughter of the American Revolution traces her forebears back to the Mayflower. A file system is an example of an object-oriented database.

    Object databases consist of big, structured sequential files connected by a set of indexes that are themselves nothing more than big, structured sequential files. This underlying database technology is called Indexed Sequential Access Method, or ISAM. You'll see this term in the Event log and other reports.

    The ESE database engine exposes the flat ISAM structure as a hierarchy of objects. In addition, Microsoft makes extensive use of COM technology by representing Active Directory objects as COM objects via the Active Directory Services Interface (ADSI).

    Classes and Attributes

    A directory service contains information about specific types of objects, such as User objects, Computer objects, and so forth. These are called object classes. A class is a bundle of attributes with a name. Figure 6.4 shows how attributes and classes are related.

    Figure 6.4. Classes and attributes in a directory service.

    graphics/06fig04.gif

    Attributes and Properties

    Attributes are also often called properties. There is a difference between these two terms, but it is so subtle that most reference manuals, including this one, use them interchangeably.

    The attributes associated with a particular object class differentiate it from other object classes. For example, User objects have different attributes than Computer objects or IP Security objects. Using a library card catalog as an example, different card formats represent different classes of items. A certain card format is used to record entries for Books. Another format is used for Tapes. The card format for Books would have spaces for Title, Author, ISBN, and so forth. A card for Tapes would have spaces for those entries plus additional spaces for Read-By and Play-Time.

    An object class, then, is really nothing more than a bundle of attributes with a name. RFC 2256, "A Summary of the X.500(96) User Schema for use with LDAPv3," defines 21 classes and 55 attributes for use in a standard LDAP directory service. Active Directory adds quite a few more for a total of about 200 object classes and 1500 attributes.

    Classes also define the scope of a directory service database. You would not expect to find cards in a library card catalog representing Off-The-Road Vehicles or Double-Meat Hamburgers. Microsoft engineers defined the initial scope of Active Directory by including a certain set of object classes and attributes. This list can be extended by other applications or by administrators. For example, your organization could create attributes and classes for storing badge numbers and social security numbers in Active Directory.

    Class Inheritance

    Directory service designers strive to limit complexity by defining the minimum number of classes and attributes necessary to describe the objects of interest that need to be stored in the directory service database.

    For example, in a library card catalog, it would be a mistake to create a class called Somewhat-Less-Than-Riveting-Early-20th-Century-American-Novels, even though it seems like quite a few objects would fit that class. In relation to the overall scope of a library, this classification would be too narrow. It would be better to have an attribute called Boring with a Boolean value. You could assign this attribute to the Book class so that objects derived from that class would get a Boring attribute that could be given a value of Yes or No or left empty. You could also assign the Boring attribute to the Periodical, Tape, and Video classes, as well.

    A directory can have hundreds of classes and many hundreds of attributes. If the attributes for each class had to be separately defined, the sheer number of perturbations would make the directory look less like a tree and more like an example of German expressionism.

    Fortunately, attributes associated with a particular class often overlap those of other classes. For example, the attribute list for the Mailbox class includes all the attributes associated with the Mail-Recipient class with one addition, the Delivery-Mechanism attribute. So, instead of separately defining all the attributes in Mailbox class, LDAP allows the class to be defined as a child of the Mail-Recipient class. This permits it to inherit the attributes of its parent. The designer need only stipulate the new additional attribute or attributes that make the subordinate class unique.

    Attributes flow down the hierarchy of object classes like genes in a family tree. Figure 6.5 shows an example of class inheritance for the Computer object class.

    Figure 6.5. Inheritance diagram for the Computer object class.

    graphics/06fig05.gif

    All LDAP classes derive from a class called Top. This makes it possible to define certain attributes that every class would have in common. For example, every class needs a Common-Name attribute. The attribute is assigned to Top and the rest of the classes inherit it.

    Think of Top as a director who never actually appears on camera but leaves a distinctive mark on the production. Top is an Abstract class, one of three class types in LDAP. They are as follows:

    • Abstract. Classes that exist solely to derive other object classes. There are 14 abstract classes in the Active Directory. Examples include Top, Device, Person, and Security Object.

    • Structural. Classes that have objects in Active Directory. Examples include User, Group, and Computer.

    • Auxiliary. Used to extend the definition of an Abstract class for specialized purposes. There are only six of these classes in Active Directory: Mail-Recipient, Dynamic-Object, MS-MMS Object, Sam-Domain, Sam-Domain-Base, and Security-Principal.

    These three class types act like assembly line robots designed to produce things called "objects." The Structural classes are the tools and dies that stamp and shape the objects. The Abstract classes are the mill workers and pattern makers that build the tools and dies. The Auxiliary classes act like a custom shop at the end of the line where special versions of standard objects are turned out.

    Object Instances

    Each object in Active Directory is derived from a specific object class. Another way of saying this is that an object represents an instance of a class. Each instance of an object class differs from another instance by having different values for its attributes.

    Remember the movie Elephant Man? In a great scene, the lead character, John Merrick, stands in front of a curious mob and exclaims, "I am not an elephant. I am a human being." Had Mr. Merrick been a directory services designer, he could have clarified his point by adding, "I am an instance of the Human Being class, not the Elephant class. And the only difference between you and me is a relatively minor attribute of mine that has a different value from yours. So lay off, will you?"

    Defining suitable attributes for an object class can be slippery. Subtle differences may force a designer to create a new class. If you were designing a library card catalog, you might start out by defining a class called Tape with an attribute called Type that has two permitted values, Audio and Video. This decision forces you to define attributes for the Tape class that fully defines both audiotapes and videotapes. After months of agonizing, you might decide that the properties of audio and video tapes are so different that they warrant creating two classes, AudioTape and VideoTape, each with their own unique attribute sets. There are many instances in Active Directory and LDAP where two object classes differ by only one or two attributes.

    Schema

    A database schema defines the content and structure of the database. In a library card catalog, the schema would be a set of procedures and rules set down by the librarian. "Books go on green cards," she tells you. "Videos go on red cards. File the cards alphabetically by Title in this cabinet and by Subject in that cabinet." So on and so on. The schema for an LDAP directory service defines these items:

    • The attributes associated with each object class

    • The permissible object classes

    • The parent-child relationship of object classes, which in turn determines attribute inheritance

    • The data type associated with each attribute

    • The physical representation of the object in the user interface

    The schema can take the form of an external table that acts as data dictionary or an internal table that is structured using the same rules as the database itself. Active Directory uses an internal schema. Many of the design constraints we'll see in the next chapter stem from the necessity to keep a consistent schema throughout all the servers that host a copy of the directory database.

    Later in this chapter, we'll see how to modify the Active Directory schema to add new attributes and object classes that can be used by applications to support network operations.

    LDAP Information Model Summary

    Here are the important information model concepts to carry forward with you when you start designing an Active Directory system for your own organization:

    • LDAP uses an object-oriented database. The database engine for Active Directory is the Extensible Storage Engine, or ESE.

    • An object class defines a unique set of attributes for a particular type of object.

    • Object classes inherit attributes from their parents. This permits the designer to identify only the new attributes for a new object class.

    • Each object is an instance of an object class. The attributes for the object are assigned values that describe that particular object.

    • A schema defines the content and structure of the LDAP database. In the case of Active Directory, the schema is contained within the directory itself.

    • The directory schema must be consistent on every server hosting a copy of the database.

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