Download MODULE NAME: INFORMATION TECHNOLOGY 2

MODULE NAME: FUNDAMENTALS OF INFORMATION TECHNOLOGY
TOPIC: Telecommunication and Computer Networks
LECTURE 11
NETWORK COMPONENTS
Network components can be placed into two categories: Hardware and software.
The hardware components of a network include the Network Interface card (NIC), Hub,
Client, server while the software focuses on the different network operating systems
(NOS).
NETWORK INTERFACE CARD
(NIC)
A (NIC) is a computer circuit board or
card that is installed in a computer so
that it can be connected to a network.
Personal computers and workstations on
a local area network (LAN) typically
contain a network interface card
specifically designed for the LAN
transmission technology, such as
Ethernet or Token Ring. Network
interface cards provide a dedicated, fulltime connection to a network. Most
home and portable computers connect to
the Internet through as-needed dial-up
connection. The modem provides the
connection interface to the Internet
service provider.
MODEM – Short for modulatordemodulator. This device enables a
computer to transmit data over telephone or
cable lines. It converts digital signals to
analog signals and vice versa.
(modulation/de-modulation). Computer
information is stored digitally whereas
information transmitted over telephone lines
is transmitted in the form of analog waves.
The device converts between the two forms.
These devices can be internal or external.
The internal ones come as an expansion
board that you can insert into a vacant
expansion slot.
REPEATERS
A repeater is a simple device that is used
to expand LANs over larger distances by
connecting segments. They
regenerate/amplify the signal.
HUBS
Hubs, also known as concentrators or
multiport repeaters, are used in
star/hierarchical networks to connect
multiple stations. A hub takes the
incoming signal from one port and
forwards it to all other ports. There are
two main types of hubs: passive and
active. A passive hub simply splits the
signal and forwards it. An active hub
takes the incoming frames, amplifies the
signal, and forwards it. Some hubs can
be managed allowing individual port
configuration and traffic monitoring,
these are known as intelligent or
managed hubs.
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Switches were developed to improve
network performance even more. Some
of the main differences between
switches and bridges are:
The following is a picture of a Fast Ethernet hub.
- Switches have more ports than bridges.
Switches are meant to replace hubs and
improve network performance by
creating a separate collision domain per
port.
- Bridges switch in software whereas
switches switch in hardware (integrated
circuits).
- Switches offer more variance in speed.
BRIDGES
Bridges are more intelligent than hubs.
They are used to increase network
performance by segmenting networks in
separate collision domains.
SWITCHES
GATEWAY – a) A combination of
hardware and software that connects
networks that use different protocols. b) A
node on a network that serves as an entrance
to another network. c) An earlier term for
router. The gateway node often acts as a
proxy server and firewall. The proxy server
sits between the client application and the
real server and intercepts all messages
entering and leaving the network and checks
if it can fulfil the requests itself, if not, then
it forwards the request to the real server. It
also hides the true network addresses. The
purpose of the proxy server is to improve
performance and to filter requests (e.g.
prevent users from accessing a specific set
of websites.
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Architecture
of most networks. It is a very fast
computer with a large amount of RAM
and storage space, along with a fast
network interface card. The network
operating system software resides on this
computer, along with any software
applications and data files that need to
be shared.
As illustrated below, bridges control collision
domains; they do not control broadcast domains:
Networks can be broadly classified as
using either a peer-to-peer or
client/server architecture.
File Servers
Computers and devices that allocate
resources for a network are called
servers. A file server stands at the heart
The file server controls the
communication of information between
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the nodes on a network. For example, it
may be asked to send a word processor
program to one workstation, receive a
database file from another workstation,
and store an e-mail message during the
same time period. This requires a
computer that can store a lot of
information and share it very quickly.



system allows only one user to run
one or more programs at a time.
An NOS has more security control
features. It also controls a network,
establish internet connection and
allows more than one computers to
talk to each other.
An NOS allows for the management
of files on other computers.
NOS typically resides on a server.
What is a Network Operating System?
Unlike operating systems, such as DOS
and Windows, which are designed for
single users to control one computer,
network operating systems (NOS)
coordinate the activities of multiple
computers across a network. The
network operating system acts as a
director to keep the network running
smoothly.
Similarities and Differences between a
Single-User Operating system and a
Network Operating System
Similarities
 Controls/manages the computer
hardware (e.g. memory)
 Provides a user interface
 Allows more than one program to
run at the same time.
 Schedules jobs and configures
devices
 Manages programs
 Provides file management and other
utilities
 Starts the computer
The two major types of network
operating systems are:

Peer-to-Peer

Client/Server
Peer-to-Peer
Peer-to-peer network operating systems
allow users to share resources and files
located on their computers and to access
shared resources found on other
computers. However, they do not have a
file server or a centralized management
source (See fig. 1). In a peer-to-peer
network, all computers are considered
equal; they all have the same abilities to
use the resources available on the
network. Peer-to-peer networks are
designed primarily for small to medium
local area networks. AppleShare and
Windows for Workgroups are
examples of programs that can function
as peer-to-peer network operating
systems.
Differences
 A network operating system (NOS)
is an operating system that organizes
and coordinates how multiple users
access and share resources on a
network. A single user operating
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the same resources irrespective of
physical location. Novell Netware and
Windows 2000 Server are examples of
client/server network operating systems.
Advantages of Client – ServerNetwork
Fig. 1. Peer-to-peer network

Centralized - Resources and data
security are controlled through
the server.

Scalability - Any or all elements
can be replaced individually as
needs increase.

Flexibility - New technology can
be easily integrated into system.

Interoperability - All components
(client/network/server) work
together.

Accessibility - Server can be
accessed remotely and across
multiple platforms.
Advantages of Peer-to-Peer Network


Less initial expense - No need for
a dedicated server.
Setup - An operating system
(such as Windows XP) already in
place may only need to be
reconfigured for peer-to-peer
operations.
Disadvantages of Peer-to-Peer
Network


Decentralized - No central
repository for files and
applications.
Security - Does not provide the
security available on a
client/server network.
Disadvantages of a Client/Server
Network

Expense - Requires initial
investment in dedicated server.

Maintenance - Large networks
will require a staff to ensure
efficient operation.

Dependence - When server goes
down, operations will cease
across the network.
Client/Server
Client/server network operating systems
allow the network to centralize
functions and applications in one or
more dedicated file servers (See fig. 2).
The file servers become the heart of the
system, providing access to resources
and providing security. Individual
workstations (clients) have access to the
resources available on the file servers.
The network operating system provides
the mechanism to integrate all the
components of the network and allow
multiple users to simultaneously share
Examples of Network Operating
Systems
The following list includes some of the
more popular peer-to-peer and
client/server network operating systems.
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
AppleShare

Microsoft Windows Server

Novell Netware

UNIX

Windows

Microsoft Windows .NET Server
2003

IBM’s OS/2 Warp Server
3. Give two examples of a network
operating system.
4. Explain the concept of the client/
server architecture.
5. Why would the administration of
a school be more inclined to set
up a client/server architecture?
What is a Protocol?
A protocol is a set of rules that governs
the communications between computers
on a network. These rules include
guidelines that regulate the following
characteristics of a network: access
method, allowed physical topologies,
types of cabling, and speed of data
transfer.
The most common protocols are:

Ethernet

LocalTalk

Token Ring

Fiber Distributed Data
Interface (FDDI)

Asynchronous Transfer
Mode (ATM)
Tutorial Questions
1. Identify and explain the use of
three hardware components that
is required to set up a network.
2. What is a network operating
system?
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