This document defines and describes various aspects of computer networks. It begins by defining a network as a group of connected computers that can share files and resources. It then discusses some key advantages of networks like sharing information and workload. The document also outlines basic network components like hardware, software and applications. It proceeds to describe different network types including LAN, MAN and WAN. It concludes by explaining common network topologies, hardware, cabling and Internet-related topics.

1. Sentra Computer
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Melaku A.

2. Sentra Computer
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Sep 2013
Melaku A.

3. Definition of network
network A group of computers and
associated peripheral devices connected by
a communications channel capable of
sharing files and other resources among
several Users.
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4. Some advantages of a network system
Sharing information (or data)
Sharing of software application systems.
Distribution of computing load on computers
Sharing of costly special devices by several computer users.
Ex. Printer ,modem, scanner…
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5. Basic network components
Application software
Network software
Network hardware
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6. Sentra Computer
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7. Speed of Data transmission
Narrow band
 Telegraph lines
Voice band
 Telephone lines
Broad band
 Recent technology

8. Types of Networks
Networks may be classified based on a number of parameters:
Geographic location
Control
1. Centralized
I.
II.
Dumb Terminals
Intelligent Terminals
 LAN
 MAN
 WAN
2. Distributed
I.
II.
Client /server
Peer –to –peer
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9. Client/server
Servers
Computers that
provide shared
resources to network
users.
Clients
Computers that access
shared network
resources provided by
a server.
F ile S erv er
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10. Peer-to-Peer
All the computers are equal and therefore are known as peers
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11. Local Area Network (LAN)
•May be located within a single building or campus
•A LAN can range from simple (two computers
connected by a cable) to complex
LAN
M AN
LAN
WA
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12. Metropolitan Area Network (MAN)
•A larger version of a LAN
•May span several corporate offices or an entire city
M
LAN
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13. WAN (Wide Area Network)
A wide area network (WAN), on the other hand, has no geographical limit.
 It can connect computers and other devices on opposite sides of the world.
 A WAN is made up of a number of interconnected LANs
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14. Network topology
The map of a network
the arrangement or physical layout of computers, cables, and other
components on the network.
Physical layout
Design
Diagram
Map
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15. Standard Topologies
 Bus
 Star
 Ring
 Mesh
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16. 1. Star topology
Each computer are connected to a hub
If the central point fails, the entire network goes down
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17. 2. Bus Topology
Referred to as a "linear bus“
a trunk (a backbone or segment)
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18. 3. Ring topology
connects computers on a single circle of cable
Failure of one computer have an impact on the entire network.
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19. 4. Mesh topology
Each computer is connected to every other computer by separate cabling
offers superior redundancy and reliability
Use a lot of cabling
If one cable fails, another will take over the traffic
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20. Hybrid topologies
Star bus topology
Star ring topology(star-wired ring)
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21. Hardware
NIC
The Network Interface Card (NIC), also known as a network adaptor,
acts as the interface between the computer and the physical network connection
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22. Most NICs for desktops are either integrated into the motherboard or are an
expansion card that fits into an expansion slot.
Most NICs for laptops are either integrated into the motherboard or fit into a
PC Card or Express Bus expansion slot.
USB network adapters plug into any available USB port and can be used with
both desktops and laptops.
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23. Sentra Computer
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24. Modem
Modulates a carrier signal to encode digital information and
Demodulate (digital to signal)
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26. Repeater
connects two network segments and broadcasts data between them.
It amplifies the signal, thereby extending the usable length of the bus.
bridge
Acts as an interface between two sets of nodes
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27. Hub
center point in a star topology
contains 4, 8, 16 or even more different ports
it broadcasts data received by any of the ports to all
other ports on the hub
Hubs can be
active,
passive or
 hybrid
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29. switch
A switch is similar to a bridge,
It has multiple ports.
Can also be seen as a more intelligent hub
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30. Router
used to connect different network segments to internet
unlike a bridge, a router can be used to connect networks
that use different network technologies.
Routers are very commonly found in the hardware
infrastructure that forms the basis of the Internet
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32. Connection Cabling
Coaxial
Twisted pair
Shielded
Unshielded
Fibre-optic
Radio wave signal
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33. Coaxial cable
relatively inexpensive, and it was light, flexible, and easy
consists of a core of copper wire surrounded by
insulation, a braided metal shielding, and an outer cover
Designed to carry a high frequency or broadband signal
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34. Fiber optic
Transparent thin fiber made of glass or
plastic for transmitting light
Very fast to transmit data and so expensive
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35. Sentra Computer Engineering,
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36. Twisted pair cable
consists
of two insulated strands of copper wire
twisted around each other
Types
1. unshielded twisted-pair (UTP) and
2. shielded twisted-pair (STP) cable.

37. Sentra Computer
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38. UTP
The most popular type of twisted-pair cable
Fast and the most popular LAN cabling
It is cheap and easy to use
Its performance over long distances is not as good as
coaxial cable
Most telephone systems use UTP cable (with the RJ11
connector), and many LANs nowadays also use UTP
(with the RJ45 connector).
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39. STP
Higher quality than UTP, but more
expensive and less popular.
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40. Worlds greatest WAN
Links millions of computer around the globe
Common features
Make information available to others
Search information provided by others
Distribute information & communicate
with others ………
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41. Every site on the Internet has an address
Internet addresses are called URLs (Uniform
Resource Locators)
Eg http://www.sentra.com/basic/list.htm
https://www.facebook.com/ukmxl/photo.htm
Domain types
.edu
.com
.gov
.mil
.net
.org
Country codes
.et
.uk
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42. WWW:- newest Internet services that allows to access documents
from any computer from the network
Website:- document address on one computer in the network
Webpage, homepage….
Search engine:- a website used to find (search) data from different
computers on the network
Chat Engine:- social networks used to direct communication
Facebook, msn, Google talk….
E-mail:- most widely used service in the internet
sending text and any multimedia messages to different
users over networks
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