The Workstation Service

All user mode requests go through the Workstation service. This service consists of two components:

• The user-mode interface.

• The redirector (RDR.SYS) — A file system driver that interacts with the lower level network drivers via the TDI interface.

The Workstation service receives the user request and passes it to the kernel mode redirector.

Workstation Service Dependencies

The Workstation service is dependent on the following components:

• A protocol that exposes the TDI interface at its top level must be started for the Workstation service to load.

• Multiple Universal Naming Convention Provider (MUP)

The Workstation Service (Redirector) as a File System Driver

The redirector is a component through which one computer gains access to another computer. The Windows NT redirector allows connection to Windows NT, Windows for Workgroups, LAN Manager, LAN Server, and other MS-Net servers. The redirector communicates to the protocols via the TDI interface.

The redirector is implemented as a Windows NT file system driver. Implementing a redirector as a file system has several benefits:

Allows applications to call a single API (namely the Windows NT I/O API) to access files on local and remote computers. From the I/O Manager's perspective, there is no difference between accessing files stored on a remote networked computer and accessing those stored locally on a hard disk.

Runs in kernel mode so it can directly call other drivers and other kernel mode components such as the Cache Manager. This improves the performance of the redirector.

• It can be loaded and unloaded dynamically, just like any other file system driver.

• It can coexist easily with other redirectors.

Accessing a Remote File

When a process on a Windows NT computer tries to open a file that resides on a remote computer, the following steps occur:

• The process calls the I/O Manager to request that the file be opened.

• The I/O Manager recognizes that the request is for a file on a remote computer, so it passes it to the redirector file system driver.

• The redirector passes the request to lower-level network drivers that transmit it to the remote Server for processing.