2.1.3 System Components
The File Access Services protocols interact with several external components as depicted in the following figure:

Figure 1: FAS System components and external components
Following are the components that interact with the FAS System.
Application: Represents a typical program with which a user interacts.
Content Caching and Retrieval services: Used to implement BranchCache caching of file server content. Branch caching does not function if these services are absent.
Browser Service: Provides a list of computers in a workgroup or domain environment, and their associated services.
Authentication Services: Used by file services to authenticate client and server principals.
Directory Services: Used for storing DFS namespace metadata.
Policy Manager: Uses the FAS System for downloading group policy information from the SYSVOL share to the group policy client, which behaves for this purpose as a File Access Services Application.
Network Information service: Used for enumerating sets of NFS client computers, as defined in the Netgroups table.
User Name Mapping Service: Used for enumerating identity mapping information for user and group accounts, in order to convert between AUTH_SYS style identity and Windows account names.
Print Services: Depends on the FAS System for transferring a print image file to the print server.
File Service: An abstraction of the software running on a file server that provides remote file access to one or more users. The service can also be managed by one or more administrators. Internally, it contains a datastore to persist changes made to files through the file access protocols. The datastore is an implementation-dependent local file system. A file service provides an abstraction of SMB Service, NFS Service, WebDAV Service, and DFS Service.
File Client: The abstractions of low-level protocol state and operating software that run on application and administrative nodes, respectively. The client is used by applications to effect communication with the remote components of the File Access Services.
Application and Admin Tool: Represent typical programs with which a user and an administrator interact, respectively. This is a somewhat arbitrary distinction, and many programs have both Application and Admin Tool features. For example, a graphical shell is frequently used directly by a user to perform personal file management tasks. This type of program is classified as an application, but it certainly has some aspects of an admin tool. For more details about admin tools, see [MS-FSMOD].