CHAPTER 9

THE WINDOWS NT NETWORKING ENVIRONMENT

Lesson 1: Windows NT Network Architecture:

The Windows NT operating systems are designed for client/server computing. Or connecting the

Workstation (client) to the Server. A computer running Windows NT can simultaneously

interoperate with the following network environments:

• Microsoft networks, including Windows NT, Microsoft Windows 95, Microsoft Windows for

Workgroups, and Microsoft LAN Manager.

• Transmission Control Protocol/Internet Protocol (TCP/IP) networks, including UNIX hosts.

Remote Access Systems. RAS

• AppleTalk-based networks (made possible through the Windows NT Server Services for the

Macintosh).

• Novell NetWare 3.x and 4.x networks.

Network Component Overview

I/O Manager, a component of Executive Services, contains most of the Windows NT networking

components. The components within I/O Manager have the following architectural layering:

Network adapter card drivers that are compatible with the network device interface specification

(NDIS 4.0) These drivers link computers running Windows NT to the network through

corresponding network adapter cards and protocols.

Protocols that enable the reliable flow of data between computers on a network.

File System drivers that enable applications to access local and remote system resources.

Each component communicates through programming interfaces called boundaries.

A boundary is the unified interface between the functional layers in the Windows NT network

architecture model. Creating boundaries as breakpoints in the network layers helps open the

networking components of the operating system to outside development by making it easier

for vendors to develop network drivers and services.

These boundary layers modularize the Windows NT network architecture and provide a platform

for developers to build distributed applications. For example, vendors developing transport

protocols need to program only between the boundary layers instead of the programming for the

entire Open Systems Interconnection (OSI) model.

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There are two boundary layers in the Windows NT networking architecture model: Transport

Driver Interface (TDI) and network device interface specification (NDIS) 4.0.

NDIS-Compatible Network Adapter Card Drivers

NDSI-compatible network adapter card drivers coordinate communications between network

adapter cards and the computer’s hardware, firmware and software. Network adapter cards

are the physical interface between the computer and the network cable.

Each network adapter card can have one or more corresponding drivers. These drivers must be

compatible with NDIS 4.0 to operate with computers running Windows NT 4.0. With NDIS 4.0,

one or more protocols can be bound, independently, to one or more network adapter card drivers.

Because network adapter cars and their corresponding drivers are independent of the protocols,

changing protocols does not require a reconfiguration or network adapter cards.

Network Device Interface Specification 4.0

The network device interface specification (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 any NDIS 4.0 compatible network adapter card driver. Therefore,

a protocol does not need to include blocks of code written for specific network adapter card drivers.

NDIS Advantages:

• Microsoft and 3COM developed it
• Multiple protocol to one NIC.
• TCP/IP eats up a lot of RAM, years before if small RAM this was a problem, but

not so much today.

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, and contains supporting routines that make it easier to develop an NDIS driver.

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In Windows NT, NDIS 4.0 allows:

• Communication links between network adapter cards and associated drivers.
• Protocols and network adapter card drivers to remain independent of each other.
• An unlimited number of network adapter cards.
• An unlimited number of protocols to be bound to a single network adapter card.

Protocols

Protocols govern communication between two or more host computers. Some protocols are

commonly referred to as transport protocols. For example, TCP/IP, NWLink, NetBEUI,

and AppleTalk are transport protocols. In the Windows NT network architecture, protocols

are located above the NDIS 4.0 interface.

Protocols communicate with network adapter cards through NDIS 4.0 compatible network

adapter card drivers. Windows NT supports multiple protocols, bound simultaneously to one

or more adapters.

The DLC or Data Link Control is also listed as a protocol. However, the DLC protocol is not

a transport protocol. DLC is used primarily for accessing printers connected directly to the

network and for accessing systems network architecture (SNA) Mainframes.

The following protocols are included with Windows NT Server and Windows NT Workstation:

Transmission Control Protocol/Internet Protocol (TCP/IP). A routable networking protocol

that supports wide area networks (WANs). TCP/IP is the protocol used on the Internet.

NOTE: TCP and UDP have completely different ports.

NWLink IPX/SPX compatible transport. An NDIS 4.0-compatibile version of the Internetwork

Packed Exchange/Sequenced Packet Exchange (IPX/SPX)

Protocol. NWLink allows users to communicate with MS-DOS, OS/2, Windows, or other

computers running Windows NT through remote procedure calls (RPCs), Windows Sockets, or

Novell NetBIOS IPX/SPX.

NetBEUI. A very small fast and efficient non-routable protocol that relies heavily on broadcasts,

and is commonly used in smaller networks. NetBEUI cannot go out onto the Internet. NetBEUI

provides compatibility with existing LAN Manager, LAN Server, Windows 95 and Windows for

Workgroup installations.

AppleTalk. Used for Services for Macintosh on a computer running Windows NT Server to host

connections from Apple Macintosh clients.

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Data link control (DLC). Traditionally used as an interface with SNA mainframes and printers

that are directly connected to the network. It cannot be used, however, to establish file and print

connections to another computer.

LAN Manager provides the following:

• Interoperability is quite strong
• NetBEUI
• RAS
• AppleTalk
• Netware 3.0 and forwards
• If the kernel mode is down the entire system will go down, but if the user mode is down it will

not take down the entire system.

Transport Driver Interface

The Transport Driver Interface is a boundary layer that provides a common programming interface

for file system drivers, such as the Workstation service (Redirector) or Server service (Server), to

communicate with the transport protocols. The TDI allows the Redirector and Server to remain

independent of the protocols.

Because the TDI allows networking components to be independent of each other, protocols can

be added, removed, or changed without reconfiguring the entire network subsystem.

TDI protocols makes the protocol transmission seem transparent to the user.

File System Drivers

File system drivers are used to access files. Any time you request a file, whether it is a request to

perform a read or write operation, a file system driver is involved. For example, if you request a

file on an NTFS partition, the Ntfs.sys file system driver is involved in servicing your request.

Several major networking components are implemented as file system drivers, such as the

Workstation (redirector) and Server Services.

The I/O Manager controls file system drivers. I/O Manager can store files locally on a hard disk

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Redirector

The I/O Manager determines if the I/O request is for a local disk or for a network resource. If the I/O

request is for a network resource, the Redirector accepts the I/O request and sends or redirects

the request to the appropriate network resource. The Windows NT Redirector (RDR) is a

component that resides above the TDI and communicates with the transport protocols by means

of the TDI interface. The redirector allows connection to Windows for Workgroups, LAN Manger,

LAN Server, and other Microsoft network-based services.

The Redirector is implemented as a Windows NT file system driver. Implementing a redirector

as a file system driver provides the following benefits:

• Applications can call the Windows NT I/O API to access files on both local and

remote computers.

• From the I/O Managers perspective, there is no difference between accessing files

stored locally on a hard disk and using the Redirector to access files remotely

on a computer on the network.

• The Redirector can run in kernel mode and directly call other drivers and other kernel-mode

components, such as Cache Manager, thereby improving the performance of the Redirector.

• The Redirector can be dynamically loaded and unloaded, like any other file system driver.
• The Redirector can easily coexist with other vendor’s redirectors that have been

installed on your computer.

Server

Windows NT includes a second component, the Server service (Server). Like the Redirector,

the Server resides above the TDI, is implemented as a file system driver, and directly interacts

with various other file system drivers to satisfy I/O requests, such as reading or writing to a file.

The Server service supplies the connections requested by client-side redirectors and provides

them with access to the resources they request.

When the Server service receives a request from a remote computer asking to read a file that

resides on the server’s local hard drive, the following occurs:

• The low-level network drivers receive the request and pass it to the Server service.
• The Server service passes a read-file request to the appropriate local file system driver.
• The local file system driver calls lower-level, disk device drivers to access the file.
• The data is passed back to the local file system driver.
• The local file system driver passes the data back to the Server service.

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• The Server service passes the data to the lower-level network driver for transmission back
• to the client computer.
• The binding order, should be attached to the most frequent protocol on the top. The
• workstation protocol order is very critical.

On the Server, the binding order is not as important.

Lesson 2: Distributed Processing

A computer running Windows NT can divide applications into components: a front-end

component that runs on a client, and a back-end component that runs on a server.

The distribution allows an application to take better advantage of hardware resources, such as

multiple processors or large amounts of RAM, that are distributed on the network. Computers

running Windows NT use interprocess communication (IPC) mechanisms to create client/server

connections that support distributed processing.

Distributed Application Overview

In a typical distributed application, a computing task is divided into processes: front-end

processes that require minimal resources and run on a client, and back-end processes that

require large amounts of data, number calculations, shared processing rules, or specialized

hardware that run on a server. The server shares its processing power, carrying out tasks

on behalf of clients.

Clients – Clients runs the user interface portion of an application.

Server – Server shares its processing power and carries out tasks on behalf of clients.

NOTE: Computers running Windows NT can perform the role of either the client or the server

for distributed application support. The client and server components can be parts of a

common application, such as Microsoft Exchange Server, or can be parts of different

applications, such as Microsoft Access communicating with Microsoft SQL Server.

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IPC Mechanisms **** Know this chart ***

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.

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IPC Mechanisms This IPC mechanism is used to

Named Pipes Build a bidirectional communication channel between

a client and server. Named pipes provide guaranteed

messaging services for distributed applications. Once

a pipe is open, both client and server can read data

from, and write data to the pipe. The WinLogon

process is an example of an application that uses

named pipes.

Mailslots Are well-known ports, from 0-1023.

(sockets) Build a unidirectional communication channel between

a client and server. Mailslots provide second-class,

non-guaranteed messaging services for distributed

applications. They can be used to identify other

computers or services on a network, such as the

browser service.

Windows Sockets Enable a distributed application to access transport

(WinSock) protocols, such as TCP/IP and IPX. WinSock can be

used to build a bi-directional, guaranteed communica-

tion channel between a client and a server.

Remote procedure calls Allow a distributed application to call procedures

(RPCs) available on various computers in a network.

Must work properly.

Network dynamic Share information between applications. NetDDE

Data exchange uses NetBIOS APIs to communicate with the

(NetDDE) underlying network components. Chat is an

example of a NetDDE-based utility.

Distributed Distribute processes, using RPCs, across multiple

Component Object computers so that the client and server components

Model (DCOM) of an application can be placed in optimal locations

on the network. You can build the programs into

models, and then implement as an entire program.

DCOM eats up a lot of RAM.

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Lesson 3: Accessing file and Print Resources:

A computer running Windows NT typically has at least one redirector and a server component that are

used for accessing and sharing file and print resources on a network.

Along with these components, there are additional components called the multiple universal naming

convention provider (MUP) and the Multiple Provider Router (MPR) that are needed to access file

and print resources on a network.

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Component Purpose

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Workstation Identify the appropriate service that can provide the resources

Service (RDR) requested by an application. The Redirector accepts I/O

requests for remote files, named pipes, or mailslots and

redirecting the I/O request to a network service on another

computer. The RDR gains access to the network log, and

connects to the domain to share folders and printers.

Server service Share and secure resources, such as directories and printers.

(SRV) The Server service accepts incoming I/O requests, such as

a request to write or read to a file, and routes the requests

resources back to the clients.

EXERCISE: Control Panel/Services/alerter

You can disable services if you want to. DDE has a

Default of “manual”. Turn them off if you do not need them.

Multiple Connect to a remote computer that accepts the universal

Universal naming convention (UNC). An example of a UNC is

Naming \\server_name\share_name\subfolder\file_name.

Convention

Provider

(MUP)

Multiple Support multiple redirectors, including Windows NT,

Provider Router NetWare, and Banyan Vines. For each redirector that is

(MPR) installed, there is also a corresponding Provider.dll.

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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, the Workstation (Redirector) and Server services complete the following steps

to fulfill the I/O request:

A client initiates an I/O request through a network command that tells the I/O Manager to open a file.

The I/O Manager recognizes the remote file request. With the assistance of the MUP or the MPR,

it passes the request to the Redirector. The Redirector (RDR) passes the request to lower-level

network drivers, which transmit it to the remove server for processing.

The Server Service (SVR) receives a request from a remote computer asking it to read a

file that resides on the server’s local hard disk. The Server service (SVR) passes the request to the

I/O Manager.

The I/O Manager passes the read request to the local file system driver.

The local file system driver calls lower-level disk device drivers to access the file. Once the file is

located, it is returned to the client that requested it through the same path.

Summary:

• Networking capabilities are fully integrated into the Windows NT operating system.
• By providing both client and server capabilities, a computer running Windows NT

can be either a client or a server in a distributed application environment.

• Windows NT also provides file and print sharing capabilities.
• I/O Manager, a component of the Executive Services, contains most of the Windows
• NT networking components. These components include network adapter cards and

their drivers, network protocols, and file system drivers.

• NDSI 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 any NDIS 4.0 compatible network adapter card driver.

• Computers running Windows NT use IPC mechanisms to create client/server

connections that support distributed processing. These include named pipes, mailslots,

• Windows Sockets, remote procedure calls (RPCs), network dynamic data exchange
• (NetDDE), and distributed Component Object Model (DCOM).