CHAPTER 5
INTRODUCING NETWORK STANDARDS
Lesson 1: Open
Systems Interconnection (OSI) ….. 208
Lesson 2: The IEEE
802.x Standard ………………. 221
Lesson 3: Device Drivers and OSI ……………….. 225
Introduction
Hardware and Software manufacturers supply products for linking computers in a network.
Networking is fundamentally a form of communication, so the need for manufacturers
to take steps to ensure that their products could interact became apparent early in the
development of networking technology. When a company solely owns a product it is
known as proprietary.
Open Systems Interconnection
(OSI)
The OSI model represents the seven layers of the process by which data is packaged and
transmitted from the sending application through the physical wires to the receiving application.
In 1984 when Networking became an issue, these standards were
put into place. The
version of this is the ANSI.
Why do we need to layer the Data?
The entire process is too complicated, it is easier to layer into 7 separate levels and have each level
perform their own tasks.
Network
Communications
Network activity involves sending data from one computer to another. Network client software
operates at many different levels within the sending and receiving computers. Because of this
layered structure, this is often referred to as the protocol stack.
A Layered
Architecture
The OSI model is the best-known and most widely used guide
for visualizing the networking
environments. The OSI divides the network communication into seven layers. Layering specifies
different functions and services as data moves from one computer through the network cabling to
another computer. The OSI model defines how each layer communicates and works with the layers
immediately above and below it. For example, the session layer communicates and works with the
presentation and transport layers. The lowest layers 1 and 2, define the network’s physical media
and related tasks, such a putting data bits onto the network interface card NIC and cable.
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Interface
Each layer is separated by a boundary called an interface. All requests are passed from one layer, through
the interface, to the next layer. The Interface only talks to the neighboring layers on either side of each layer.
****** DEMOS 3-5 ****** Excellent
Addressing Packets
Most packets on the network are addressed to a specific
computer and, as a result, get the
of only one computer. Each NIC sees all packets sent on its cable segment, but it interrupts the
computer only if the packet’s address matches the card’s individual address.
Directing Packets
Network components use the addressing information in packets
to direct the packets to
destinations or to keep them away from network locations where they do not belong.
They use two types of forwarding, and they are:
Packet forwarding: Computers send a packet on to the next appropriate network components based
on the address in the packet’s header.
Packet filtering: Computers use criteria, such as an address, to select specific packets.
Windows NT and the OSI Reference Model
Microsoft simplifies the 7 layer model into 3: File System (Application, Presentation,
and Session), Transport
Protocols (Transport, Network) and Network Interface
Card Drivers, (Data-Link and Physical).
Windows NT uses drivers to provide for communication between the operating system and the
network. A driver is a device-specific control program that enables a computer to work with a
particular device, such as a printer or a disk drive. Every time you install a new piece of hardware,
such as a printer, sound card, or network card, you need to install the software drivers that
operate the card.
TCP/IP
This is not easy to install, but it is so widely used
because it is a free service, provided by the
government. It is hard to trouble-shoot. In the next couple of years you will run out of addresses
for the TCP/IP.
One advantage of Windows NT, is it will accept any type of Hardware or Software given to it,
it has become very adaptable, and compatible in the market.
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Windows NT Interfaces
Windows NT supports many different network redirectors, transport protocols and NIC’s.
To resolve the problem, Microsoft developed common interfaces, boundary layers to act as
translators between each layer.
Application Programming Interfaces (API’s)
The API are system routines that give programmers access to the services provided by the
operating system. Responsible for setting up the session between the sender and the receiver
on the Network.
Transport Driver Interfaces (TDI’s)
The TDI’s work
between the file system drives and the transport protocols.
The TDI’s decide on the fly which one it wants.
Network Driver Interface Specifications (NDIS’s)
The NDIS’s work
between the transport protocols and the NIC Drivers. As long as the NIC
driver is written to NDIS standards, it will communicate with the transport protocols.
Microsoft is very proud of the one, they developed it themselves. Review this for the MCSE test.
You can have multiple protocol bound to 1 card, instead of one NIC card/item.
The IEEE 802.X Standard
When local area networks (LAN’s) first began to emerge as potential business tools in the 70’s
the IEEE realized that there was a need to define certain LAN standards. The IEEE cares about the
physical standards, how the wiring works, and how long it should be etc.
Also know that there are currently 16 standards, but only memorize the ones below:
Important Standards
802.3 MAC layer for bus network CSMA/CD, Ethernet
802.4 MAC layer for bus network using token
passing
802.5 MAC layer for token ring networks
802.8 Fiberoptic
802.9
voice and data standards
For more information visit the IEEE website www.IEEE.org
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Enhancements to the OSI Model
The IEEE 802 project only cares about the last 2 layers the Data-Link and the Physical layer. The data Link
layer is broken into two:
LLC Logical Link Control
This sublayer manages data-link communication and defines the use of logical interface points called service
access points. (SAP.)
Media Access Control (MAC)
The MAC provides shared access to the physical layer for the
computers’ NICs. The MAC layer
communicated directly with the NIC and is responsible for delivering error-free data between two
computers on the network.
DEVICE DRIVERS AND OSI
NICs play an important role in
connecting a computer to the physical part of the network. Drivers
are
small software programs that enable a computer to work with a network card or other devices.
A Driver is software that enable a computer to work with a particular device. The software driver
tells the computer how to drive or work with the device so that the device performs the job it is
assigned in the way it is supposed to.
Each physical piece of hardware needs an individual driver, even RAM has a device driver.
Microsoft has a mini-driver, to make them compatible with other industry vendors. They allow you
to attach monitors, keyboards, mouses etc. from other companies, and they will operate correctly.
Drivers are currently on floppy’s, CD-ROM and Internet (not caught on yet, what if you are
down-loading your modem?????
Network Driver Interface Specification (NDIS)
Network Driver Interface specification (NDIS) is a standard that defines an interface for com-
munication between the MAC sublayer and the protocol drivers.
Protocol stack – Provides network communication
Adapter Driver – Controls the network interface hardware
Protocol Manager – Controls the activity between the protocol stack and the MAC
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Open Data-Link Interface (ODI)
Developed by Novell to simplify driver development for their network operating systems.
But it is crap, does not work. Novell does not support ODI at all any more.