This document uses the following terms:
access control entry (ACE): An entry in an access control list (ACL) that contains a set of user rights and a security identifier (SID) that identifies a principal for whom the rights are allowed, denied, or audited.
access control list (ACL): A list of access control entries (ACEs) that collectively describe the security rules for authorizing access to some resource; for example, an object or set of objects.
account: A user (including machine account), group, or alias object. Also a synonym for security principal or principal.
account database: The portion of the directory that maintains the accounts for the principals of the domain. In Windows NT-4 style domains, the account database includes all information in the domain; in Active Directory–style domains, the account database contains a subset of the entire LDAP-accessible directory that the Active Directory–style domain hosts.
Active Directory: The Windows implementation of a general-purpose directory service, which uses LDAP as its primary access protocol. Active Directory stores information about a variety of objects in the network such as user accounts, computer accounts, groups, and all related credential information used by Kerberos [MS-KILE]. Active Directory is either deployed as Active Directory Domain Services (AD DS) or Active Directory Lightweight Directory Services (AD LDS), which are both described in [MS-ADOD]: Active Directory Protocols Overview.
Active Directory Domain Services (AD DS): A directory service (DS) implemented by a domain controller (DC). The DS provides a data store for objects that is distributed across multiple DCs. The DCs interoperate as peers to ensure that a local change to an object replicates correctly across DCs. AD DS is a deployment of Active Directory [MS-ADTS].
Active Directory Lightweight Directory Services (AD LDS): A directory service (DS) implemented by a domain controller (DC). AD LDS is a deployment of Active Directory [MS-ADTS]. The most significant difference between AD LDS and Active Directory Domain Services (AD DS) is that AD LDS does not host domain naming contexts (domain NCs). A server can host multiple AD LDS DCs. Each DC is an independent AD LDS instance, with its own independent state. AD LDS can be run as an operating system DS or as a directory service provided by a standalone application (Active Directory Application Mode (ADAM)).
Active Directory-style domain: A domain that is created as described in [MS-ADTS] section 1. Active Directory-style domains implement Active Directory, LDAP, Kerberos authentication, and advanced configurations and features that are not supported in Windows NT 4.0-style domains.
ADCAP: The Active Directory Web Services Custom Action Protocol [MS-ADCAP].
application naming context (application NC): A specific type of naming context (NC), or an instance of that type, that supports only full replicas (no partial replicas). An application NC cannot contain security principal objects in Active Directory Domain Services (AD DS), but can contain security principal objects in Active Lightweight Directory Services (AD LDS). A forest can have zero or more application NCs in either AD DS or AD LDS. An application NC can contain dynamic objects. Application NCs do not appear in the global catalog (GC). The root of an application NC is an object of class domainDNS.
attribute: An identifier for a single or multivalued data element that is associated with a directory object. An object consists of its attributes and their values. For example, cn (common name), street (street address), and mail (email addresses) can all be attributes of a user object. An attribute's schema, including the syntax of its values, is defined in an attributeSchema object.
backup domain controller (BDC): A domain controller (DC) that receives a copy of the domain directory database from the primary domain controller (PDC). This copy is synchronized periodically and automatically with the primary domain controller (PDC). BDCs also authenticate user logons and can be promoted to function as the PDC. There is only one PDC or PDC emulator in a domain, and the rest are backup domain controllers.
binding: The string representation of the protocol sequence, NetworkAddress, and optionally the endpoint. Also referred to as "string binding". For more information, see [C706] section "String Bindings".
certificate: A certificate is a collection of attributes and extensions that can be stored persistently. The set of attributes in a certificate can vary depending on the intended usage of the certificate. A certificate securely binds a public key to the entity that holds the corresponding private key. A certificate is commonly used for authentication and secure exchange of information on open networks, such as the Internet, extranets, and intranets. Certificates are digitally signed by the issuing certification authority (CA) and can be issued for a user, a computer, or a service. The most widely accepted format for certificates is defined by the ITU-T X.509 version 3 international standards. For more information about attributes and extensions, see [RFC3280] and [X509] sections 7 and 8.
client: Synonym for client computer.
client computer: The client machine in the domain or network topology of clients, servers, and domain controllers. Alternatively, a computer that is not a domain controller server; the computer may or may not be joined to a domain.
configuration naming context (config NC): A specific type of naming context (NC), or an instance of that type, that contains configuration information. In Active Directory, a single config NC is shared among all domain controllers (DCs) in the forest. A config NC cannot contain security principal objects.
credential: Previously established, authentication data that is used by a security principal to establish its own identity. When used in reference to the Netlogon Protocol, it is the data that is stored in the NETLOGON_CREDENTIAL structure.
deleted-object: An object that has been deleted, but remains in storage until a configured amount of time (the deleted-object lifetime) has passed, after which the object is transformed to a recycled-object. Unlike a recycled-object or a tombstone, a deleted-object maintains virtually all the state of the object before deletion, and can be undeleted without loss of information. Deleted-objects exist only when the Recycle Bin optional feature is enabled.
directory: The database that stores information about objects such as users, groups, computers, printers, and the directory service that makes this information available to users and applications.
directory service (DS): A service that stores and organizes information about a computer network's users and network shares, and that allows network administrators to manage users' access to the shares. See also Active Directory.
directory tree: An LDAP directory service is organized into a hierarchical tree structure in which each directory object has exactly one parent directory object (except for one object that serves as the root of the tree) and zero or more child directory objects.
domain: A set of users and computers sharing a common namespace and management infrastructure. At least one computer member of the set must act as a domain controller (DC) and host a member list that identifies all members of the domain, as well as optionally hosting the Active Directory service. The domain controller provides authentication of members, creating a unit of trust for its members. Each domain has an identifier that is shared among its members. For more information, see [MS-AUTHSOD] section 22.214.171.124 and [MS-ADTS].
domain client: A client computer that is joined to a domain. The domain client can be a client or a server that offers other services to its clients. When the domain client acts as a supplicant to another domain client, the supplicant is referred to as a domain client in a workstation role and the latter as a domain client in a server role.
domain controller (DC): The service, running on a server, that implements Active Directory, or the server hosting this service. The service hosts the data store for objects and interoperates with other DCs to ensure that a local change to an object replicates correctly across all DCs. When Active Directory is operating as Active Directory Domain Services (AD DS), the DC contains full NC replicas of the configuration naming context (config NC), schema naming context (schema NC), and one of the domain NCs in its forest. If the AD DS DC is a global catalog server (GC server), it contains partial NC replicas of the remaining domain NCs in its forest. For more information, see [MS-AUTHSOD] section 126.96.36.199.2 and [MS-ADTS]. When Active Directory is operating as Active Directory Lightweight Directory Services (AD LDS), several AD LDS DCs can run on one server. When Active Directory is operating as AD DS, only one AD DS DC can run on one server. However, several AD LDS DCs can coexist with one AD DS DC on one server. The AD LDS DC contains full NC replicas of the config NC and the schema NC in its forest. The domain controller is the server side of Authentication Protocol Domain Support [MS-APDS].
domain controller server: A domain member, which can be a client or a server that offers other services to its clients. When the domain client acts as a supplicant to another domain client, the supplicant is referred to as a domain client in a workstation role and the latter as a domain client in a server role.
domain functional level: A specification of functionality available in a domain. Must be less than or equal to the DC functional level of every domain controller (DC) that hosts a replica of the domain's naming context (NC). For information on defined levels, corresponding features, information on how the domain functional level is determined, and supported domain controllers, see [MS-ADTS] sections 188.8.131.52 and 184.108.40.206. When Active Directory is operating as Active Directory Lightweight Directory Services (AD LDS), domain functional level does not exist.
Domain Name System (DNS): A hierarchical, distributed database that contains mappings of domain names to various types of data, such as IP addresses. DNS enables the location of computers and services by user-friendly names, and it also enables the discovery of other information stored in the database.
domain naming context (domain NC): A specific type of naming context (NC), or an instance of that type, that represents a domain. A domain NC can contain security principal objects; no other type of NC can contain security principal objects. Domain NCs appear in the global catalog (GC). A domain NC is hosted by one or more domain controllers (DCs) operating as AD DS. In AD DS, a forest has one or more domain NCs. A domain NC cannot exist in AD LDS. The root of a domain NC is an object of class domainDNS; for directory replication [MS-DRSR], see domainDNS.
endpoint: A network-specific address of a remote procedure call (RPC) server process for remote procedure calls. The actual name and type of the endpoint depends on the RPC protocol sequence that is being used. For example, for RPC over TCP (RPC Protocol Sequence ncacn_ip_tcp), an endpoint might be TCP port 1025. For RPC over Server Message Block (RPC Protocol Sequence ncacn_np), an endpoint might be the name of a named pipe. For more information, see [C706].
enumeration context: A session context that represents a specific traversal through a logical sequence of XML element information items using the Pull operation defined in WS-Enumeration specification. See [WSENUM].
extended control: A mechanism that is used to specify extension information in a Lightweight Directory Access Protocol (LDAP) version 3 operation. It is documented in [RFC2251] section 4.1.12, Controls, where it is referred to as a "control".
flexible single master operation (FSMO): A read or update operation on a naming context (NC), such that the operation must be performed on the single designated master replica of that NC. The master replica designation is "flexible" because it can be changed without losing the consistency gained from having a single master. This term, pronounced "fizmo", is never used alone; see also FSMO role, FSMO role owner, and FSMO object.
forest: For Active Directory Domain Services (AD DS), a set of naming contexts (NCs) consisting of one schema naming context (schema NC), one configuration naming context (config NC), one or more domain naming contexts (domain NCs), and zero or more application naming contexts (application NCs). Because a set of NCs can be arranged into a tree structure, a forest is also a set containing one or several trees of NCs. For AD LDS, a set of NCs consisting of one schema NC, one config NC, and zero or more application NCs. (In Microsoft documentation, an AD LDS forest is called a "configuration set".)
FSMO role: A set of objects that can be updated in only one naming context (NC) replica (the FSMO role owner's replica) at any given time. For more information, see [MS-ADTS] section 220.127.116.11.11. See also FSMO role owner.
fully qualified domain name (FQDN): (1) An unambiguous domain name that gives an absolute location in the Domain Name System's (DNS) hierarchy tree, as defined in [RFC1035] section 3.1 and [RFC2181] section 11.
global catalog (GC): A unified partial view of multiple naming contexts (NCs) in a distributed partitioned directory. The Active Directory directory service GC is implemented by GC servers. The definition of global catalog is specified in [MS-ADTS] section 18.104.22.168.8.
identity: An account that represents a person (user account), an application (service account), and computers that participate in the domain (machine accounts). A password is used by the system as proof of an identity.
Interface Definition Language (IDL): The International Standards Organization (ISO) standard language for specifying the interface for remote procedure calls. For more information, see [C706] section 4.
Kerberos: An authentication system that enables two parties to exchange private information across an otherwise open network by assigning a unique key (called a ticket) to each user that logs on to the network and then embedding these tickets into messages sent by the users. For more information, see [MS-KILE].
Key Distribution Center (KDC): The Kerberos service that implements the authentication and ticket granting services specified in the Kerberos protocol. The service runs on computers selected by the administrator of the realm or domain; it is not present on every machine on the network. It must have access to an account database for the realm that it serves. KDCs are integrated into the domain controller role. It is a network service that supplies tickets to clients for use in authenticating to services.
Lightweight Directory Access Protocol (LDAP): The primary access protocol for Active Directory. Lightweight Directory Access Protocol (LDAP) is an industry-standard protocol, established by the Internet Engineering Task Force (IETF), which allows users to query and update information in a directory service (DS), as described in [MS-ADTS]. The Lightweight Directory Access Protocol can be either version 2 [RFC1777] or version 3 [RFC3377].
member server: A server that is joined to a domain and is not acting as an Active Directory domain controller (DC). Member servers typically function as file servers, application servers, and so on and defer user authentication to the domain controller.
mutual authentication: A mode in which each party verifies the identity of the other party, as described in [RFC3748] section 7.2.1.
naming context (NC): An NC is a set of objects organized as a tree. It is referenced by a DSName. The DN of the DSName is the distinguishedName attribute of the tree root. The GUID of the DSName is the objectGUID attribute of the tree root. The security identifier (SID) of the DSName, if present, is the objectSid attribute of the tree root; for Active Directory Domain Services (AD DS), the SID is present if and only if the NC is a domain naming context (domain NC). Active Directory supports organizing several NCs into a tree structure.
NetBIOS: A particular network transport that is part of the LAN Manager protocol suite. NetBIOS uses a broadcast communication style that was applicable to early segmented local area networks. A protocol family including name resolution, datagram, and connection services. For more information, see [RFC1001] and [RFC1002].
Netlogon: The Netlogon Remote Protocol, as specified in [MS-NRPC].
Network Data Representation (NDR): A specification that defines a mapping from Interface Definition Language (IDL) data types onto octet streams. NDR also refers to the runtime environment that implements the mapping facilities (for example, data provided to NDR). For more information, see [MS-RPCE] and [C706] section 14.
NT Directory Service (NTDS): A previous name for Active Directory.
object class: A set of restrictions on the construction and update of objects. An object class can specify a set of must-have attributes (every object of the class must have at least one value of each) and may-have attributes (every object of the class may have a value of each). An object class can also specify the allowable classes for the parent object of an object in the class. An object class can be defined by single inheritance; an object whose class is defined in this way is a member of all object classes used to derive its most specific class. An object class is defined in a classSchema object. See section 1 of [MS-ADTS] and section 1 of [MS-DRSR].
originating update: An update that is performed to an NC replica via any protocol except replication. An originating update to an attribute or link value generates a new stamp for the attribute or link value.
policy: A collection of settings that contains global settings, profile settings, firewall rules, and connection security rules. Together these settings specify how the host firewall and Internet Protocol security (IPsec) behave on the client computer.
primary domain controller (PDC): A domain controller (DC) designated to track changes made to the accounts of all computers on a domain. It is the only computer to receive these changes directly, and is specialized so as to ensure consistency and to eliminate the potential for conflicting entries in the Active Directory database. A domain has only one PDC.
principal: A unique entity identifiable by a security identifier (SID) that is typically the requester of access to securable objects or resources. It often corresponds to a human user but can also be a computer or service. It is sometimes referred to as a security principal.
read-only domain controller (RODC): A domain controller (DC) that does not accept originating updates. Additionally, an RODC does not perform outbound replication. An RODC cannot be the primary domain controller (PDC) for its domain.
relative distinguished name (RDN): In the Active Directory directory service, the unique name of a child element relative to its parent in Active Directory. The RDN of a child element combined with the fully qualified domain name (FQDN) (2) of the parent forms the FQDN of the child.
relative identifier (RID): The last item in the series of SubAuthority values in a security identifier (SID) [SIDD]. It distinguishes one account or group from all other accounts and groups in the domain. No two accounts or groups in any domain share the same RID.
remote procedure call (RPC): A communication protocol used primarily between client and server. The term has three definitions that are often used interchangeably: a runtime environment providing for communication facilities between computers (the RPC runtime); a set of request-and-response message exchanges between computers (the RPC exchange); and the single message from an RPC exchange (the RPC message). For more information, see [C706].
replica domain controller / replica directory server: A server that contains a replicated copy of the directory and is able to answer client requests over any protocol that the directory service supports.
role: The domain role quantifies the relationship between a computer and a domain. Domain roles include the following: Joined: Linked to a domain for purposes of policy and security. Standalone: Not associated with any domain. Domain controller: Linked to a domain, and hosting that domain.
Secure Sockets Layer (SSL): A security protocol that supports confidentiality and integrity of messages in client and server applications that communicate over open networks. SSL supports server and, optionally, client authentication using X.509 certificates [X509] and [RFC5280]. SSL is superseded by Transport Layer Security (TLS). TLS version 1.0 is based on SSL version 3.0 [SSL3].
security descriptor: A data structure containing the security information associated with a securable object. A security descriptor identifies an object's owner by its security identifier (SID). If access control is configured for the object, its security descriptor contains a discretionary access control list (DACL) with SIDs for the security principals who are allowed or denied access. Applications use this structure to set and query an object's security status. The security descriptor is used to guard access to an object as well as to control which type of auditing takes place when the object is accessed. The security descriptor format is specified in [MS-DTYP] section 2.4.6; a string representation of security descriptors, called SDDL, is specified in [MS-DTYP] section 2.5.1.
security identifier (SID): An identifier for security principals that is used to identify an account or a group. Conceptually, the SID is composed of an account authority portion (typically a domain) and a smaller integer representing an identity relative to the account authority, termed the relative identifier (RID). The SID format is specified in [MS-DTYP] section 2.4.2; a string representation of SIDs is specified in [MS-DTYP] section 2.4.2 and [MS-AZOD] section 22.214.171.124.
security principal: An entity that is associated with a human user or a program that can be authenticated. At a minimum, it has two basic attributes, a name and an identifier, that uniquely identifies it and makes it meaningful to the system, administrators, and users. A security principal is also known as a principal or an account.
Server Message Block (SMB): A protocol that is used to request file and print services from server systems over a network. The SMB protocol extends the CIFS protocol with additional security, file, and disk management support. For more information, see [CIFS] and [MS-SMB].
service (SRV) resource record: A Domain Name System (DNS) resource record used to identify computers that host specific services, as specified in [RFC2782]. SRV resource records are used to locate domain controllers (DCs) for Active Directory.
service principal name (SPN): The name a client uses to identify a service for mutual authentication. (For more information, see [RFC1964] section 2.1.1.) An SPN consists of either two parts or three parts, each separated by a forward slash ('/'). The first part is the service class, the second part is the host name, and the third part (if present) is the service name. For example, "ldap/dc-01.fabrikam.com/fabrikam.com" is a three-part SPN where "ldap" is the service class name, "dc-01.fabrikam.com" is the host name, and "fabrikam.com" is the service name. See [SPNNAMES] for more information about SPN format and composing a unique SPN.
service ticket: A ticket for any service other than the ticket-granting service (TGS). A service ticket serves only to classify a ticket as not a ticket-granting ticket (TGT) or cross-realm TGT, as specified in [RFC4120].
site: A collection of one or more well-connected (reliable and fast) TCP/IP subnets. By defining sites (represented by site objects) an administrator can optimize both Active Directory access and Active Directory replication with respect to the physical network. When users log in, Active Directory clients find domain controllers (DCs) that are in the same site as the user, or near the same site if there is no DC in the site. See also Knowledge Consistency Checker (KCC). For more information, see [MS-ADTS].
SOAP: A lightweight protocol for exchanging structured information in a decentralized, distributed environment. SOAP uses XML technologies to define an extensible messaging framework, which provides a message construct that can be exchanged over a variety of underlying protocols. The framework has been designed to be independent of any particular programming model and other implementation-specific semantics. SOAP 1.2 supersedes SOAP 1.1. See [SOAP1.2-1/2003].
ticket-granting ticket (TGT): A special type of ticket that can be used to obtain other tickets. The TGT is obtained after the initial authentication in the Authentication Service (AS) exchange; thereafter, users do not need to present their credentials, but can use the TGT to obtain subsequent tickets.
tombstone: An object that has been deleted, but remains in storage until a configured amount of time (the tombstone lifetime) has passed, after which the object is permanently removed from storage. By keeping the tombstone in existence for the tombstone lifetime, the deleted state of the object is able to replicate. Tombstones exist only when the Recycle Bin optional feature is not enabled.
Transmission Control Protocol (TCP): A protocol used with the Internet Protocol (IP) to send data in the form of message units between computers over the Internet. TCP handles keeping track of the individual units of data (called packets) that a message is divided into for efficient routing through the Internet.
Transport Layer Security (TLS): A security protocol that supports confidentiality and integrity of messages in client and server applications communicating over open networks. TLS supports server and, optionally, client authentication by using X.509 certificates (as specified in [X509]). TLS is standardized in the IETF TLS working group.
trusted domain object (TDO): A collection of properties that define a trust relationship with another domain, such as direction (outbound, inbound, or both), trust attributes, name, and security identifier of the other domain. For more information, see [MS-ADTS].
user principal name (UPN): A user account name (sometimes referred to as the user logon name) and a domain name that identifies the domain in which the user account is located. This is the standard usage for logging on to a Windows domain. The format is: firstname.lastname@example.org (in the form of an email address). In Active Directory, the userPrincipalName attribute of the account object, as described in [MS-ADTS].
Windows NT 4.0-style domain: A domain that is created from Windows NT 4.0 operating system servers with an account database that includes all the information in the domain. Windows NT 4.0-style domains do not implement Active Directory, LDAP directories, or Kerberos authentication.
writable naming context (NC) replica: A naming context (NC) replica that accepts originating updates. A writable NC replica is always full, but a full NC replica is not always writable. Partial replicas are not writable. See also read-only full NC replica.
XML: The Extensible Markup Language, as described in [XML1.0].