This document uses the following terms:
Active Directory: A general-purpose network directory service. Active Directory also refers to the Windows implementation of a directory service. Active Directory stores information about a variety of objects in the network. Importantly, user accounts, computer accounts, groups, and all related credential information used by the Windows implementation of Kerberos are stored in Active Directory. Active Directory is either deployed as Active Directory Domain Services (AD DS) or Active Directory Lightweight Directory Services (AD LDS). [MS-ADTS] describes both forms. For more information, see [MS-AUTHSOD] section 184.108.40.206.2, Lightweight Directory Access Protocol (LDAP) versions 2 and 3, Kerberos, and DNS.
Advanced Encryption Standard (AES): A block cipher that supersedes the Data Encryption Standard (DES). AES can be used to protect electronic data. The AES algorithm can be used to encrypt (encipher) and decrypt (decipher) information. Encryption converts data to an unintelligible form called ciphertext; decrypting the ciphertext converts the data back into its original form, called plaintext. AES is used in symmetric-key cryptography, meaning that the same key is used for the encryption and decryption operations. It is also a block cipher, meaning that it operates on fixed-size blocks of plaintext and ciphertext, and requires the size of the plaintext as well as the ciphertext to be an exact multiple of this block size. AES is also known as the Rijndael symmetric encryption algorithm [FIPS197].
authentication level: A numeric value indicating the level of authentication or message protection that remote procedure call (RPC) will apply to a specific message exchange. For more information, see [C706] section 220.127.116.11 and [MS-RPCE].
authoritative response: An authoritative response is one in which the server has all necessary resources to service the caller's request. If some of the resources are temporarily unavailable, then the server will indicate that its response is not authoritative. When a server does not return an authoritative response, it is reasonable for the caller to retry the request at another server. The reasons why a request is non-authoritative are always implementation-specific and could include any failure of the server to allocate necessary resources.
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.
checked build: A special build of a Windows NT operating system–based operating system that contains fewer compiler optimizations and more debugging checks than a production environment build. The purpose of the checked build is to make identifying and diagnosing operating system–level problems easier. For more information, see [MSDN-CHKBLD].
client challenge: A 64-bit nonce generated on the client side.
computer name: The DNS or NetBIOS name.
computer object: An object of class computer. A computer object is a security principal object; the principal is the operating system running on the computer. The shared secret allows the operating system running on the computer to authenticate itself independently of any user running on the system. See security principal.
credential: Previously established, authentication (2) 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.
database: For the purposes of the Netlogon RPC, a database is a collection of user accounts, machine accounts, aliases, groups, and policies, managed by a component. The database, or the component managing the database, must expose a mechanism to enable Netlogon to gather changes from and apply changes to the database. Additionally, it must export a database serial number in order to track changes for efficient replication.
delta: One of a set of possible changes that can be made to a database.
direct trust: A type of authentication functionality in which one domain accepts another domain as an authoritative source to provide object authentication and other Active Directory services for that other domain. For example, if a direct trust is established from domain, DOMAIN-A, to domain, DOMAIN-B, DOMAIN-A trusts DOMAIN-B. If a domain, DOMAIN-A, must authenticate an object, such as a user account, from a domain, DOMAIN-B, DOMAIN-A requests that DOMAIN-B authenticate the user account, and DOMAIN-A will treat the response from DOMAIN-B as reliable.
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.
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 (2) 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 18.104.22.168 and [MS-ADTS].
domain account: A stored set of attributes (2) representing a principal used to authenticate a user or machine to an Active Directory domain.
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 22.214.171.124.2 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 local group: An Active Directory group that allows user objects, global groups, and universal groups from any domain as members. It can additionally include, and be a member of, other domain local groups from within its domain. A group object g is a domain local group if and only if GROUP_TYPE_RESOURCE_GROUP is present in g!groupType; see [MS-ADTS] section 2.2.12, "Group Type Flags". A security-enabled domain local group is valid for inclusion within access control lists (ACLs) from its own domain. If a domain is in mixed mode, then a security-enabled domain local group in that domain allows only user objects as members.
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 tree: A set of domains that are arranged hierarchically, typically following an accompanying DNS hierarchy, with trusts between parents and children. An example domain tree might be a.example.com, b.example.com, and example.com; domain A and domain B each trust example.com but do not trust each other directly. They will have a transitive trust relationship through example.com.
encryption key: One of the input parameters to an encryption algorithm. Generally speaking, an encryption algorithm takes as input a clear-text message and a key, and results in a cipher-text message. The corresponding decryption algorithm takes a cipher-text message, and the key, and results in the original clear-text message.
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].
enterprise network: The network of computer systems in an organization, such as a corporation. An enterprise can span geographical locations and often includes a variety of computer types, operating systems, protocols, and network architectures.
forest: One or more domains that share a common schema and trust each other transitively. An organization can have multiple forests. A forest establishes the security and administrative boundary for all the objects that reside within the domains that belong to the forest. In contrast, a domain establishes the administrative boundary for managing objects, such as users, groups, and computers. In addition, each domain has individual security policies and trust relationships with other domains.
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 126.96.36.199.8.
globally unique identifier (GUID): A term used interchangeably with universally unique identifier (UUID) in Microsoft protocol technical documents (TDs). Interchanging the usage of these terms does not imply or require a specific algorithm or mechanism to generate the value. Specifically, the use of this term does not imply or require that the algorithms described in [RFC4122] or [C706] must be used for generating the GUID. See also universally unique identifier (UUID).
Hash-based Message Authentication Code (HMAC): A mechanism for message authentication (2) using cryptographic hash functions. HMAC can be used with any iterative cryptographic hash function (for example, MD5 and SHA-1) in combination with a secret shared key. The cryptographic strength of HMAC depends on the properties of the underlying hash function.
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.
Key Distribution Center (KDC): The Kerberos service that implements the authentication (2) 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. Windows KDCs are integrated into the domain controller role of a Windows Server operating system acting as a Domain Controller. It is a network service that supplies tickets to clients for use in authenticating to services.
Local Security Authority (LSA): A protected subsystem that authenticates and logs users onto the local system. LSA also maintains information about all aspects of local security on a system, collectively known as the local security policy of the system.
Local Security Authority (LSA) database: A Microsoft-specific terminology for the part of the user account database containing account privilege information (such as specific account rights) and domain security policy information.
mixed mode: A state of an Active Directory domain that supports domain controllers (DCs) running Windows NT Server 4.0 operating system. Mixed mode does not allow organizations to take advantage of new Active Directory features such as universal groups, nested group membership, and interdomain group membership. See also native mode.
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.
Netlogon: In a Windows NT-compatible network security environment, the component responsible for synchronization and maintenance functions between a primary domain controller (PDC) and backup domain controllers (BDC). Netlogon is a precursor to the directory replication server (DRS) protocol.
network logon: A software method in which the account information and credentials previously supplied by the user as part of an interactive logon are used again to log the user onto another network resource.
nonce: A number that is used only once. This is typically implemented as a random number large enough that the probability of number reuse is extremely small. A nonce is used in authentication protocols to prevent replay attacks. For more information, see [RFC2617].
one-way function (OWF): The calculation of a hash of the password using the Rivest-Shamir-Adleman (RSA) MD4 function. OWF is used to refer to the resulting value of the hash operation.
opnum: An operation number or numeric identifier that is used to identify a specific remote procedure call (RPC) method or a method in an interface. For more information, see [C706] section 188.8.131.52 or [MS-RPCE].
original equipment manufacturer (OEM) character set: A character encoding used where the mappings between characters is dependent upon the code page configured on the machine, typically by the manufacturer.
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.
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 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 context-dependent term commonly overloaded with three meanings. Note that much of the industry literature concerning RPC technologies uses this term interchangeably for any of the three meanings. Following are the three definitions: (*) The runtime environment providing remote procedure call facilities. The preferred usage for this meaning is "RPC runtime". (*) The pattern of request and response message exchange between two parties (typically, a client and a server). The preferred usage for this meaning is "RPC exchange". (*) A single message from an exchange as defined in the previous definition. The preferred usage for this term is "RPC message". For more information about RPC, see [C706].
RPC protocol sequence: A character string that represents a valid combination of a remote procedure call (RPC) protocol, a network layer protocol, and a transport layer protocol, as described in [C706] and [MS-RPCE].
secret key: A symmetric encryption key shared by two entities, such as between a user and the domain controller (DC), with a long lifetime. A password is a common example of a secret key. When used in a context that implies Kerberos only, a principal's secret key.
Security Account Manager (SAM): A centrally managed service, such as Active Directory Domain Services (AD DS), that enables a server to establish a trust relationship with other authorized servers. The SAM also maintains information about domains and security principals, and provides client-to-server information by using several available standards for access control lists (ACLs).
security account manager (SAM) built-in database: Microsoft-specific terminology for the part of the user account database that contains account information (such as account names and passwords) for accounts and groups that are pre-created at the database installation.
security context: An abstract data structure that contains authorization information for a particular security principal in the form of a Token/Authorization Context (see [MS-DTYP] section 2.5.2). A server uses the authorization information in a security context to check access to requested resources. A security context also contains a key identifier that associates mutually established cryptographic keys, along with other information needed to perform secure communication with another security principal.
security identifier (SID): An identifier for security principals in Windows 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 184.108.40.206.
security principal: A unique entity, also referred to as a principal, that can be authenticated by Active Directory. It frequently corresponds to a human user, but also can be a service that offers a resource to other security principals. Other security principals might be a group, which is a set of principals. Groups are supported by Active Directory.
security provider: A pluggable security module that is specified by the protocol layer above the remote procedure call (RPC) layer, and will cause the RPC layer to use this module to secure messages in a communication session with the server. The security provider is sometimes referred to as an authentication service. For more information, see [C706] and [MS-RPCE].
security support provider (SSP): A dynamic-link library (DLL) that implements the Security Support Provider Interface (SSPI) by making one or more security packages available to applications. Each security package provides mappings between an application's SSPI function calls and an actual security model's functions. Security packages support security protocols such as Kerberos authentication and NTLM.
Security Support Provider Interface (SSPI): A Windows-specific API implementation that provides the means for connected applications to call one of several security providers to establish authenticated connections and to exchange data securely over those connections. This is the Windows equivalent of Generic Security Services (GSS)-API, and the two families of APIs are on-the-wire compatible.
server: A computer on which the remote procedure call (RPC) server is executing.
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 instance 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 instance name, and "fabrikam.com" is the service name. See [SPNNAMES] for more information about SPN format and composing a unique SPN.
session key: A relatively short-lived symmetric key (a cryptographic key negotiated by the client and the server based on a shared secret). A session key's lifespan is bounded by the session to which it is associated. A session key has to be strong enough to withstand cryptanalysis for the lifespan of the session.
shared secret: A piece of data that is known only to the security principal and an authenticating authority; for example, a user and a domain controller. It is used to prove the principal's identity. A password is a common example of a shared secret. Also called a "secret key".
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].
sub-authentication package: An optional component that provides additional authentication functionality. If a sub-authentication package is installed, the authentication package calls the sub-authentication package before returning its authentication result. The request to verify by a sub-authentication package is indicated by the ParameterControl field of the LogonInformation parameter (see [MS-APDS] section 220.127.116.11.1, Verifying Responses with Sub-Authentication Packages).
transitive trust: The state of two domains establishing trust through an intermediary domain. For example, if domain A trusts domain B, and domain B trusts domain C, then domain A can be configured to trust domain C through transitive trust.
trust: To accept another authority's statements for the purposes of authentication and authorization, especially in the case of a relationship between two domains. If domain A trusts domain B, domain A accepts domain B's authentication and authorization statements for principals represented by security principal objects in domain B; for example, the list of groups to which a particular user belongs. As a noun, a trust is the relationship between two domains described in the previous sentence.
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].
Unicode: A character encoding standard developed by the Unicode Consortium that represents almost all of the written languages of the world. The Unicode standard [UNICODE5.0.0/2007] provides three forms (UTF-8, UTF-16, and UTF-32) and seven schemes (UTF-8, UTF-16, UTF-16 BE, UTF-16 LE, UTF-32, UTF-32 LE, and UTF-32 BE).
universally unique identifier (UUID): A 128-bit value. UUIDs can be used for multiple purposes, from tagging objects with an extremely short lifetime, to reliably identifying very persistent objects in cross-process communication such as client and server interfaces, manager entry-point vectors, and RPC objects. UUIDs are highly likely to be unique. UUIDs are also known as globally unique identifiers (GUIDs) and these terms are used interchangeably in the Microsoft protocol technical documents (TDs). Interchanging the usage of these terms does not imply or require a specific algorithm or mechanism to generate the UUID. Specifically, the use of this term does not imply or require that the algorithms described in [RFC4122] or [C706] must be used for generating the UUID.
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 (2) of the account object, as described in [MS-ADTS].
writable domain controller: A domain controller that performs originating updates and outbound replication.
MAY, SHOULD, MUST, SHOULD NOT, MUST NOT: These terms (in all caps) are used as defined in [RFC2119]. All statements of optional behavior use either MAY, SHOULD, or SHOULD NOT.