Grade 11 CSS Lesson 3 Computer Network.pptx

Computer System Servicing NC II
Lesson 3: Computer Network

Technical Terms
• Bluetooth - wireless connection used to send and received messages
• Coverall - apparel suit won to protect the body
• E-mail - electronic messages received via internet
• Fax - abbreviation of facsimile; the electronic transmission of copies of
documents for reproduction at a remote location.
• Internet - abbreviation for internetwork. A set of corrupt networks made
up of a large number of smaller networks.
• Intranet - set of interconnected networks using the Internet
• Protocol Modem - translates between digital signals that the computer
uses, and analog signals suitable for transmission over telephone lines.
• Network - interconnected group of computers

• PDA - abbreviation for Personal Digital Assistant; a tiny pen-based palm top
computer that combines fax, e-mail and simple word processing into an easy-to-use
unit that fits, into pocket.
• OH&S - Occupational Health & Safety
• Peer-to-peer network - a network architecture in which driver files and printers on
every PC can be available to every other PC on the network. Policies - approach,
code, system, guidelines, theory, line
• Server - any computer that makes access to files, printing, communications, or
other services available to users of the network.
• Software - an application program or an operating system that the computer
executes
• Storage Media - devices used to store data from the computer.
• Topology - map of a network
• USB - abbreviation of Universal Serial Bus
• Wide Area Network - network that connects users across large distances, others
cross the geographical boundaries of cities or state.

A computer network is an interconnected group of computers.
Computer Network
In general, the term network can refer to any interconnected group or system.
More specifically, a network is any method of sharing information between two
systems (human or mechanical).

BENEFITS OF SHARING INFORMATION VIA NETWORK
In addition to reducing hardware costs by sharing expensive printers and other
peripherals among multiple users, networks provide additional benefits to the users.
 Software and data files can be shared for access by multiple users
 Electronic mail e-mail can be sent and received
 Collaboration features allow contributions by multiple users to a single document
 Remote-control programs can be used to troubleshoot problems or show new users
how to perform a task
SHARED HARDWARE COMPONENTS
Virtually, any storage or output device can be shared over a network, but the most
common devices to be used over a network include:
 Printers
 Disk drives
 CD-ROM and optical drives
 Modems
 Fax
 Tape backup units

Network topology
Network Topology signifies the way in which intelligent devices in the network
see their logical relations to one another. The use of the term "logical" here is
significant. That is, network topology is independent of the "physical" layout of the
network. Even if networked computers are physically placed in a linear
arrangement, if they are connected via a hub, the network has a Star topology,
rather than a Bus Topology. In this regard the visual and operational characteristics
of a network are distinct; the logical network topology is not necessarily the same
as the physical layout.
 Bus Topology
It is often used when network installation is small, simple or temporary. On a
typical bus network the cable is just 1 or more wires with no active electronics to
amplify the signal or pass it along from computer to computer. This makes the bus
a passive topology. When 1 computer sends a signal up the wire all the computers
receive the information but only one with the address that matches accepts the
information, the rest disregard the message.

Bus Topology
Advantages:
1)Easy to use and to understand.
2)Requires least amount of cable to connect the computers together. It is
therefore less expensive than other cabling arrangements.
3)It is easy to extend a bus; two cables can be joined into 1 longer cable with a
BNC, Barrel connector making a longer cable and allowing more computers
to join the
network.

Disadvantages:
1)Heavy network traffic can slow a bus considerably as only 1
computer can send a message at a time.
2)It is difficult to troubleshoot the bus. A cable break or loose
connector causes reflection and stops all the activity.

 STAR TOPOLOGY
In this kind of topology all the cables run from the computers to the
central location where they are all connected by a device called hub
or switch. Each computer on a star network communicates with a
central device that resends the message either to each computer or
only to the destination computer, example if it is a hub then it will send
to all and if it is a switch then it will send to only destination computer.
When network expansion is expected and when the greater reliability
is needed, star topology is the best.

Advantages:
1)It is easy to modify and add new computers without
disturbing the rest of the network.
2)The center of the star network is a good place to diagnose
the faults.
3)Single computer failure does not necessarily bring down the
whole star network.
Disadvantages:
1)If the central device fails, the whole network fails to operate.
2)Star networking is expensive because all network cables
must be pulled to one central point, requires more cable
than other network topologies.

 RING TOPOLOGY
In this type each computer is connected to the next computer
with the last one connected to the first. Each retransmits what it
receives from the previous computer. The message flows around
the ring in one direction. The ring network does not subject to
signal loss problem as a bus network experiences. There is no
termination because there is no end to the ring.

Advantages:
1)Each node has equal access.
2)Capable of high speed data transfer.
Disadvantages:
1)Failure of one computer on the ring can affect the whole network.
2)Difficult to troubleshoot the network.

Types of networks
Below is a list of the most common types of computer networks in
order of scale.
 Personal Area Network (PAN)
A personal area network (PAN) is a computer network used for
communication among computer devices close to one person. Some
examples of devices that may be used in a PAN are printers, fax
machines, telephones, PDA’s or scanners. The reach of a PAN is
typically within about 20-30 feet (approximately 6-9 meters).

Personal area networks may be wired with computer buses such as
USB] and FireWire. A wireless personal area network (WPAN) can also
be made possible with network technologies such as Bluetooth.

 Local Area Network (LAN)
A network covering a small geographic area, like a home, office, or
building. Current LANs are most likely to be based on Ethernet technology.
For example, a library will have a wired or wireless LAN for users to
interconnect local devices (e.g., printers and servers) and to connect to the
internet. All of the PCs in the library are connected by category 5 (Cat5)
cable, running the IEEE 802.3 protocol through a system of interconnection
devices and eventually connect to the internet. The cables to the servers
are on Cat 5e enhanced cable, which will support IEEE 802.3 at 1 GB/s.

The staff computers (bright green) can get to the color printer, checkout
records, and the academic network and the Internet. All user computers
can get to the Internet and the card catalog. Each workgroup can get to its
local printer. Note that the printers are not accessible from outside their
workgroup.
LAN
Hub
Server

Client/Server Vs Peer-to-Peer Networks
Although every computer on a LAN is connected to every
other, they do not necessarily mean all communicate with each
other. There are two basic types of LAN, based on
communication patterns between the machines, called
client/server networks and peer-to-peer networks.
Client/Server Networks
Every computer has a distinct role, that of either a client or a
server. A server is designed to share its resources among client
computers on the network. The Client/Server is composed of:

Servers
 These are located in secured areas, such as locked closets and data
centers, because they hold the organization's most valuable data
and do not have the accessed by operators on a continuous basis.
 The server runs a special network operating system such as:
Windows NT Server, Windows 2000 or Novell Netware.
Clients
 The rest of the computers on the network functions as client. A client
standard PC that is running an operating system such as DOS or
Windows.
Hub
Server
Client

Peer-to-Peer Network
In a peer-to-peer network, every computer is equal and can
communicate with other computer on a network to which it has been
granted access rights. Essentially, every computer in this network
functions as both server and client. Peer-to-peer network can be as small
as two computers as many as hundreds of units.
There is no theoretical limit to the size of a peer-
to-peer network, performance drops significantly
and security becomes a major headache on peer -
based network with more than 10 computers. Also,
Microsoft imposes a 10-station limit on computers
running Windows 2000 Professional who are
sharing resources with other system. For this
reason, it is better you switch to a client/server
network when your network climbs to 10 stations.

CAMPUS AREA NETWORK (CAN)
A network that connects two or more LANs but that is limited to a
specific and contiguous geographical area such as a college campus,
industrial complex, or a military base. A CAN may be considered a type
of MAN (metropolitan area network), but is generally limited to an area
that is smaller than a typical MAN. This term is most often used to
discuss the implementation of networks for a contiguous area. This
should not be confused with a Controller Area Network.

Metropolitan Area Network (MAN)
A Metropolitan Area Network is a network that connects two or more
Local Area Networks or Campus Area Networks together but does not
extend beyond the boundaries of the immediate town, city, or metropolitan
area. Multiple routers, switches & hubs are connected to create a MAN.

Wide Area Network (WAN)
A WAN is a data communications network that covers a relatively
broad geographic area (i.e. one city to another and one country to
another country) and that often uses transmission facilities provided by
common carriers, such as telephone companies. WAN technologies
generally function at the lower three layers of the OSI reference model:
the physical layer, the data link layer, and the network layer.

Global Area Network (GAN)
Global area networks (GAN) specifications are in development by
several groups, and there is no common definition. In general,
however, a GAN is a model for supporting mobile communications
across an arbitrary number of wireless LANs, satellite coverage areas,
etc. The key challenge in mobile communications is "handing off" the
user communications from one local coverage area to the next. In
IEEE Project 802, this involves a succession of terrestrial Wireless
local area networks (WLAN).

Internetwork
Two or more networks or network segments connected using
devices that operate at layer 3 (the 'network' layer) of the OSI
Basic Reference Model, such as a router. Any interconnection
among or between public, private, commercial, industrial, or
governmental networks may also be defined as an internetwork.
In modern practice, the interconnected networks use the
Internet Protocol. There are at least three variants of internetwork,
depending on who administers and who participates in them:
 Intranet
 Extranet
 Internet

Intranets and extranets may or may not have connections to the
Internet. If connected to the Internet, the intranet or extranet is
normally protected from being accessed from the Internet without
proper authorization. The Internet is not considered to be a part of
the intranet or extranet, although it may serve as a portal for access
to portions of an extranet.
Intranet
An intranet is a set of interconnected networks, using the Internet
Protocol and uses IP-based tools such as web browsers and ftp
tools, that is under the control of a single administrative entity. That
administrative entity closes the intranet to the rest of the world, and
allows only specific users. Most commonly, an intranet is the internal
network of a company or other enterprise.

An extranet is a network or internetwork that is
limited in scope to a single organization or entity but
which also has limited connections to the networks
of one or more other usually, but not necessarily,
trusted organizations or entities (e.g. a company's
customers may be given access to some part of its
intranet creating in this way an extranet, while at the
same time the customers may not be considered
'trusted' from a security standpoint). Technically, an
extranet may also be categorized as a CAN, MAN,
WAN, or other type of network, although, by
definition, an extranet cannot consist of a single
LAN; it must have at least one connection with an
external network.
Extranet

Internet
A specific internetwork, consisting of a worldwide interconnection
of governmental, academic, public, and private networks based
upon the Advanced Research Projects Agency Network (ARPANET)
developed by ARPA of the U.S. Department of Defense – also home
to the World Wide Web (WWW) and referred to as the 'Internet' with
a capital 'I' to distinguish it from other generic internetworks.
Participants in the Internet, or their service providers, use IP
Addresses obtained from address registries that control
assignments. Service providers and large enterprises also exchange
information on the reach ability of their address ranges through the
Border Gateway Protocol (BGP).

Activity #3: Identify the following. Choose your answer from the grid below.
______________ 1. The World Wide Web.
______________ 2. The internal network of a company or other enterprise.
______________ 3. A model for supporting mobile communications across an arbitrary
number of wireless LANs.
______________ 4. A data communications network that covers a relatively broad
geographic area.
______________ 5. A network that connects two or more Local Area Networks or Campus
Area Networks together.
______________ 6. It signifies the way in which intelligent devices in the network see their
logical relations to one another
______________ 7. It is the interconnected group of computers.
______________ 8. A network covering a small geographic area, like a home.
______________ 9. All the cables run from the computers to the central location where they
are all connected by hub.
______________10. Each computer is connected to the next computer with the last one
connected to the first.
Topology LAN GAN
Ring Topology Network MAN
Bus Topology WAN Internet
Star Topology Intranet Extranet

Grade 11 CSS Lesson 3 Computer Network.pptx

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Grade 11 CSS Lesson 3 Computer Network.pptx