# Windows NT Server 4.0 Notes
Module 9: The Windows NT Networking Environment Networking capabilities are fully integrated into the Windows NT operating system. With its integrated network support, a single computer running Windows NT can interoperate, simultaneously, in the following network environments: Microsoft networks (NT, W95, WfW and LAN Manager) TCP/IP systems including Unix hosts Macintosh AppleTalk networks to provide Macintosh interoperability (Windows NT Server Services for Macintosh Novell Netware 3.x and 4.x MS-DOS and Windows 3.x should have networking capabilities separately installed.
Windows NT Network Architecture
The networking architecture of Windows NT is modular. This means: interoperability with multiple network environments the components are easily updated without affecting everything else new components can be added
Network Component Overview:
I/O Manager Component Overview The Windows NT networking components are integrated with the I/O manager in the Executive services. The components are organized into the following architectural layers: I/O Manager, a component of Executive Services, contains most of the Windows NT networking components which are organized into the following architectural layers, from "bottom" to "top": Network Adapter Card Drivers: This layer includes NDIS 4.0 and Adapter Card Drivers (NDIS 4.0 Library). Protocols: Includes TCP/IP (UNIX), NWLINK (NetWare), NetBEUI (MS Network), AppleTalk (AppleTalk-based network), DLC (SNA). File System Drivers: Includes Redirector and Server Each component communicates through a programming interface called a boundary layer. Boundary layer = the unified interface between the layers in the Windows NT network architecture model. These boundary layers modularize the Windows NT network architecture and provide a platform for developers to build distributed applications. There are two boundary layers in the Windows NT networking architecture model: NDIS 4.0 TDI
NDIS-Compatible Network Adapter Card Drivers:
NIC drivers talk to the hardware NDIS-compatible network card drivers coordinate communications between network adapter cards and the computer's hardware, firmware and software. Each network adapter card has a corresponding driver. The driver must be compatible with NDIS 4.0 to operate with computers running Windows NT 4.0. With NDIS, one or more protocols can be bound, independently, to one or more network adapter card drivers. NICs and their drivers are independent of system protocols ð changing protocols doesn't mean changing the NIC or drivers.
Network Component Overview:
NDIS allows the protocols to talk to the NIC drivers Network Device Interface Specification (NDIS) 4.0 NDIS 4.0 defines the software interface used by protocols to communicate with network adapter card drivers. Any NDIS 4.0 compatible protocol can communicate with a NDIS 4.0-compatible network adapter card driver. The initial communication channel between the protocol and the network adapter card driver is established through a process called binding In Windows NT, NDIS 4.0 is implemented in a module called Ndis.sys which is referred to as the NDIS 4.0 library or wrapper. The NDIS 4.0 library is code surrounding all of the NDIS device drivers. The library provides a uniform interface between protocol drivers and NDIS device drivers. In NT, NDIS 4.0 allows: Communication links between network adapter cards and associated drivers. Protocol drivers and NIC drivers to remain independent of each other. An unlimited number of NICs. An unlimited number of protocols to be bound to a single NIC.
Protocols
Protocols allow two computers to talk to each other Transport protocols provide communication sessions and ensure that data moves reliable between computers. They communicate with network adapter cards through NDIS 4.0 compatible drivers
Note: DLC is not used for general networking with Windows NT and is not considered a transport protocol.
Windows NT supports these protocols:
Protocol | Description
TCP/IP | Routable transport protocol; basis of the Internet.
NWLink IPX/SPX | An NDIS 4.0 compatible version of IPX/SPX. It allows communication with MS-DOS, OS/2, Windows or Windows NT through remote procedure calls (RPCs), Windows Sockets or Novell NetBIOS IPX/SPX.
NetBEUI | Fast and efficient non-routable protocol relying on broadcasts and used in small networks. Provides compatibility with existing LAN Manager, IBM LAN Server, Windows 95 and Windows for Workgroups.
AppleTalk | In Services for Macintosh to connect to Macintosh clients
DLC (Data Link Control) | Used as an interface with an SNA (System Network Architecture - IBM) mainframe and NETWORK PRINTERS DLC is not used for general networking with Windows NT and is not considered a transport protocol.
Transport Driver Interface:
TDI provides a common, accepted way for file system drivers to talk to protocols The TDI is a boundary layer that provides a common programming interface for file system drivers, such as the Workstation service (Redirector) or the Server service (Server), to communicate with the transport protocols. The TDI is a specification to which protocol drivers are written that allows the Redirectors and Server service to remain independent of the protocols. File System Drivers: File system drivers are used to access files. When a file is requested, a file system driver helps to service the request. Several major networking components are implemented as file system drivers, such as the Workstation service (redirector) and the Server service (server). The I/O manager controls file system drivers: Store files locally on hard disk using a file system driver such as Ntfs.sys. OR On remote networked computer using the Redirector file system driver. In Windows NT architecture, file system drivers are located above the TDI and allow user-mode applications to access system resources. Redirectors: The I/O manager determines if an I/O request is for a local disk or for a network resource. If the I/O request is for a network resource (i.e. not local -- OUTGOING), a Redirector accepts the I/O request and sends it to the appropriate network resource. The Windows NT Redirector (RDR) communicates with the transport protocols by means of the TDI. The redirector allows connection to servers running Windows NT, Windows for Workgroups, LAN Manager, LAN Server and other MS based servers. The Redirector is implemented as a Windows NT file system driver. Benefits: Applications can call the Windows NT I/O application programming interface (API) to access both local and remote computers. From the I/O manager perspective there is no difference between the two. Redirector can run in kernel mode and directly call other drivers and kernel mode components thereby improving the performance of the Redirector. Redirector can be dynamically loaded and unloaded. Redirector can easily coexist with other vendor's redirectors. Server Service: This service also resides above the TDI, it is implemented as a file system driver, and it directly interacts with other file system drivers to satisfy I/O requests. The Server service supplies the connections requested by client side redirectors ( i.e. IN-COMING requests) and provides these redirectors with access to the requested resources. If the service is not running, shared folders and printers are not accessible. When Server service receives a request from a remote computer asking to read a file that resides on the server, the following steps occur. Low-level network drivers receive the request, and then pass it to the Server service. Server service passes a read-file request to the appropriate local file system driver. Local file system driver calls lower-level, disk device drivers to access the file. Data is passed back to the local file system driver. Local file system driver passes data back to the Server service. Server service passes the data to the lower-level network drivers for transmission back to the client.
Interprocess Communications Mechanisms:
In distributed processing, a network connection that allows data to flow in both directions must exist between the client and server portions of a distributed application. This table describes Windows NT IPC mechanisms that are used to achieve these connections:
IPC mechanism | What this mechanism does.....
Named pipes (Two way channel) | builds a bi-directional communication channel between the client and the server provides guaranteed messaging services for distributed applications once a pipe is open, both the client and the server can read data from, and write data to the pipe (example WinLogon)
Mailslots (One way channel) | builds a unidirectional communication channel between the client and the server provide non-guaranteed messaging services for distributed applications can be used to identify other computers or services on the network, such as a Browser Service
Windows Sockets (WinSock) | enables distributed application to access transport protocols such as TCP/IP or IPX build a bi-directional guaranteed communication channel between the client and the server any non-Microsoft client uses sockets ð UNIX, for example
RPCs | calls a procedure that resides in a server process running on a remote machine
Network dynamic data exchange (NetDDE) | shares information between applications uses NetBIOS APIs to communicate with the underlying network components (example chat)
Distributed Component Object Model (DCOM) | distribute processes, using RPCs, across multiple computers so that the client and server components of an application can be placed in optimal locations on the network so DCOM integrates client/server applications across multiple computers
Accessing File and Print Resources
File and Print Sharing Components: Windows NT includes networking components that are required to share network resources on a server and to gain access to network resources from a client running Windows NT. The following table describes the purpose of each of these components.
Component | Purpose
Workstation service (Redirector) | Identifies the appropriate service that can provide the resources requested by the application; Redirector does this by accepting I/O requests for remote files, named pipes, or mailslots, and then redirecting the I/O request to a network service on another computer Redirector enables a client to be used to gain access to network resources including logging on to a domain connecting to a shared folder or printer use distribute applications
Server service | create and secure shared resources such as directories or printers accepts incoming I/O requests (such as reading or writing to a file) and then routes requested resources back to the client
MUP Multiple Universal Naming Convention Provider | connects to remote computer that accepts the Universal Naming Convention (UNC) frees applications from having to maintain UNC provider listings; this allows the client computer to have multiple redirectors installed and to browse through and gain access to network resources without having to provide a unique syntax to each network redirector
MPR Multiple Provider Router | supports multiple redirectors including Windows NT, NetWare and Banyan VINES; for each redirector there is a corresponding provider.dll the MPR is responsible for routing network requests to appropriate provider and redirector
File and Print Sharing Process:
When a process on a computer running Windows NT attempts to open a file that resides on a remote computer, Workstation and Server services fulfill the I/O request in following process: Client initiates an I/O request through a network command that tells the I/O manager to open a file I/O manager recognizes the remote file request; with assistance of MUP and MPR, it passes the request to the Redirector. Redirector passes the request to lower-level network drivers, which then transmit the request to the remote server for processing Server Service receives a request from remote computer asking to read a file that resides on the server’s local hard disk Server Service passes request to I/O manager I/O manager passes read request to local file system driver Local file system driver calls lower-level disk device drivers to access file When file is located, it is returned to the client that requested it through the same path.
Distributed File System:
Windows NT Distributed File System (Dfs) is a utility for Windows NT 4.0 that lets a network administrator logically organize multiple file servers and shares into a single directory structure, using a Dfs directory tree. Dfs Features: Easy browsing of file servers. Dfs allows creation of a single directory tree that includes all of the file servers and file shares in a group, division or entire organization. Dfs gives the user a single directory that can span an almost unlimited number of file servers and network directories making it easy to browse. administrator can create multiple trees and therefore have multiple "VIEWS" of the network. Easy integration with Windows 95 (Dfs product) and Windows NT Workstation 4.0 operating systems; Dfs helps users to make their desktop easier to use each user needs only one persistent connection to his or her Dfs tree (NOT multiple drive mappings to different shares all over) Doesn't work with MS-DOS or Mac clients Simple searches for files or data. Easy connection to the Internet and intranets. Multiple intranet servers can be placed in a single Dfs tree in a corporate intranet multiple inTERnet servers can be added without changing your www root directory structure. Provides EASY organization wide backup
Only NT SERVER can host Dfs but shares from NT Workstation and W95 clients can be grafted into Dfs trees
| Top of page
Comments and suggestions? E-mail me at grantwil@sk.sympatico.ca
Last Updated: Wednesday, March 10, 1999 | Grant Wilson, Tisdale, SK. Canada