1.1 Glossary

This document uses the following terms:

8.3 name: A file name string restricted in length to 12 characters that includes a base name of up to eight characters, one character for a period, and up to three characters for a file name extension. For more information on 8.3 file names, see [MS-CIFS] section 2.2.1.1.1.

DFS namespace name: The second path component of a DFS path. In the DFS path \\MyDomain\MyDfs\MyDir, the DFS namespace name is MyDfs.

DFS server: A server computer that runs the DFS service required to respond to DFS referral requests. Also interchangeably used to refer to the DFS service itself.

DFS target: Either a DFS root target server or a DFS link target server.

Distributed File System (DFS): A file system that logically groups physical shared folders located on different servers by transparently connecting them to one or more hierarchical namespaces. DFS also provides fault-tolerance and load-sharing capabilities.

Distributed File System (DFS) client: A computer that is used to access a DFS namespace. It also can refer to the DFS software on a client that accesses the DFS namespace.

Distributed File System (DFS) client target failback: An optional feature that, when enabled, permits a DFS client to revert to a more optimal DFS target at an appropriate time after a DFS client target failover. The term "failback" refers to DFS client target failback. The DFS Referral Protocol, as specified in [MS-DFSC], describes the mechanisms by which a DFS server provides a list of DFS targets in decreasing order of optimality to the client.

Distributed File System (DFS) client target failover: When a DFS referral response has multiple targets, a DFS client attempts to find the first target that is both available and accessible. If the first DFS target in the list is not available or accessible, the DFS client determines whether the next target in the list is available and accessible. The client repeats this process until an available and accessible target is found or no more targets are left in the list of targets. DFS clients support DFS client target failover only for operations involving pathnames. The term "failover" refers to DFS client target failover. The DFS Referral Protocol, as specified in [MS-DFSC], describes the mechanisms by which a DFS server provides a list of DFS targets in decreasing order of optimality to the client.

Distributed File System (DFS) in-site referral mode: A mode in which DFS root or DFS link referral requests to a DFS server result in DFS referral responses with only those DFS targets in the same Active Directory Domain Services (AD DS) site as the DFS client requesting the DFS referral. When this mode is disabled, there is no restriction on the AD DS site of the targets returned in the referral response. This can be enabled per DFS namespace. If there are no DFS targets in the same AD DS site as the client, the DFS referral response could be empty.

Distributed File System (DFS) interlink: A special form of DFS link whose link target is a DFS domain-based namespace.

Distributed File System (DFS) link: A component in a DFS path that lies below the DFS root and maps to one or more DFS link targets. Also interchangeably used to refer to a DFS path that contains the DFS link.

Distributed File System (DFS) link target: The mapping destination of a link. A link target can be any Universal Naming Convention (UNC) path. For example, a link target could be a share or another Distributed File System (DFS) path.

Distributed File System (DFS) metadata: Information about a Distributed File System (DFS) namespace such as namespace name, DFS links, DFS link targets, and so on, that is maintained by a DFS server. For domain-based DFS, the metadata is stored in an Active Directory Domain Services (AD DS) object corresponding to the DFS namespace. For a stand-alone DFS namespace, the DFS root target stores the DFS metadata in an implementation-defined manner; for example, in the registry.

Distributed File System (DFS) namespace: A virtual view of shares on different servers as provided by DFS. Each file in the namespace has a logical name and a corresponding address (path). A DFS namespace consists of a root and many links and targets. The namespace starts with a root that maps to one or more root targets. Below the root are links that map to their own targets.

Distributed File System (DFS) namespace, domain-based: A DFS namespace that has configuration information stored in the Active Directory directory service. The DFS namespace can span over a distributed system that is organized hierarchically into logical domains, each with a domain controller (DC). The path to access the root or a link starts with the host domain name. A domain-based DFS root can have multiple root targets, which offers fault tolerance and load sharing at the root level.

Distributed File System (DFS) namespace, standalone: A DFS namespace that has metadata stored locally on the host server. The path to access the root or a link starts with the host server name. A stand-alone DFS root has only one root target. Stand-alone roots are not fault-tolerant; when the root target is unavailable, the entire DFS namespace is inaccessible. Stand-alone DFS roots can be made fault tolerant by creating them on clustered file servers.

Distributed File System (DFS) path: Any Universal Naming Convention (UNC) path that starts with a DFS root and is used for accessing a file or directory in a DFS namespace.

Distributed File System (DFS) referral: A DFS client issues a DFS referral request to a DFS root target or a DC, depending on the DFS path accessed, to resolve a DFS root to a set of DFS root targets, or a DFS link to a set of DFS link targets. The DFS client uses the referral request process as needed to finally identify the actual share on a server that has accessed the leaf component of the DFS path. The request for a DFS referral is referred to as DFS referral request, and the response for such a request is referred to as DFS referral response.

Distributed File System (DFS) referral site costing: When appropriately enabled for a DFS namespace, an optional feature that results in a DFS referral response. In the referral response, targets are grouped into sets based on increasing Active Directory Domain Services (AD DS) site cost from the DFS client that is requesting the referral to the DFS target server. When this feature is disabled, the referral response consists of at most two target sets: one set consisting of all DFS targets in the same AD DS site as the DFS client, and the other set consisting of DFS targets that are not in the same AD DS site as the DFS client.

Distributed File System (DFS) root: The starting point of the DFS namespace. The root is often used to refer to the namespace as a whole. A DFS root maps to one or more root targets, each of which corresponds to a share on a separate server. A DFS root has one of the following formats "\\<ServerName>\<RootName>" or "\\<DomainName>\<RootName>". Where <ServerName> is the name of the root target server hosting the DFS namespace; <DomainName> is the name of the domain that hosts the DFS root; and <RootName> is the name of the root of a domain-based DFS.  The DFS root has to reside on an NTFS volume.

Distributed File System (DFS) root target: A server that hosts a DFS root of a DFS namespace. A domain-based DFS namespace can have multiple DFS root targets; a standalone DFS namespace can have only one DFS root target.

domain: A set of users and computers sharing a common namespace and management infrastructure. At least one computer member of the set has to 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 1.1.1.5 and [MS-ADTS].

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 1.1.1.5.2 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 name: A name with a structure indicated by dots.

domain-based DFS namespace: A DFS namespace that has configuration information stored in domain services. The DFS namespace can span a distributed system that is organized hierarchically into logical domains. The path to access a domain-based DFS namespace starts with the host domain name. A domain-based DFS namespace can have multiple DFS root targets, which offers high availability and load sharing at the DFS root level.

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.

host name: The name of a host on a network that is used for identification and access purposes by humans and other computers on the network.

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].

share: A resource offered by a Common Internet File System (CIFS) server for access by CIFS clients over the network. A share typically represents a directory tree and its included files (referred to commonly as a "disk share" or "file share") or a printer (a "print share"). If the information about the share is saved in persistent store (for example, Windows registry) and reloaded when a file server is restarted, then the share is referred to as a "sticky share". Some share names are reserved for specific functions and are referred to as special shares: IPC$, reserved for interprocess communication, ADMIN$, reserved for remote administration, and A$, B$, C$ (and other local disk names followed by a dollar sign), assigned to local disk devices.

share name: The name of a share.

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].

site cost: An administrator-defined numerical value meant to indicate the bandwidth or actual monetary cost of transmitting data between two sites. Only a comparison between two site cost values is meaningful, with a lower site preferred to a higher site cost.

stand-alone DFS namespace: A DFS namespace that has DFS metadata stored locally on the host server. The path to access the DFS root or a DFS link starts with the DFS root target host name. A stand-alone DFS namespace has only one DFS root target. Stand-alone DFS roots are not fault-tolerant; when the DFS root target is unavailable, the entire DFS namespace is inaccessible. Stand-alone DFS roots can be made fault-tolerant by being created on clustered file servers.

target set: A consecutive list of referral entries. A DFS referral response consists of DFS targets that are grouped into sets based on various policies. One policy groups DFS targets into two sets: one consisting of all DFS targets in the same site as the DFS client, and the other consisting of all remaining DFS targets. Another policy creates DFS target sets, where each set contains DFS targets that have the same site cost from the DFS client's perspective, in increasing order of cost. By assigning non-default priorities to DFS targets, other policies are possible. For more information, see [MSDFS].

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).

Universal Naming Convention (UNC): A string format that specifies the location of a resource. For more information, see [MS-DTYP] section 2.2.57.

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.