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 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 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.
- 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.
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 servers 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.
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 |
|