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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:

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:

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:

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:

  1. NDIS 4.0
  2. 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.

Network Component Overview:

NDIS allows the protocols to talk to the NIC drivers

Network Device Interface Specification (NDIS) 4.0

Protocols

Protocols allow two computers to talk to each other

 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 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:

  1. Store files locally on hard disk using a file system driver such as NTfs.sys. OR
  2. 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.

The Redirector is implemented as a Windows NT file system driver. Benefits:

This service also

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.

 

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: 

       

       

    1. Client initiates an I/O request through a network command that tells the I/O manager to open a file
    2. I/O manager recognizes the remote file request; with assistance of MUP and MPR, it passes the request to the Redirector.
    3. Redirector passes the request to lower-level network drivers, which then transmit the request to the remote server for processing
    4. Server Service receives a request from remote computer asking to read a file that resides on the server’s local hard disk
    5. Server Service passes request to I/O manager
    6. I/O manager passes read request to local file system driver
    7. 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:

  • 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)
Only NT SERVER can host Dfs but shares from NT Workstation and W95 clients can be grafted into Dfs trees
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Last Updated: August 6, 2001 Grant Wilson, Edmonton, AB Canada