2. Introduction
When PCs first appeared in businesses software
programs, were designed for a single user. There
were few obvious advantages of connecting PCs,
and the technology was not adequate for doing
so.
As computers spread throughout business,
developers begun offering complex software
designed for multiple users.
Many organizations rapidly learned the
importance of connecting PCs.
Data communication- the electronic transfer of
data between computers- became a major focus
the computer industry.
3. During the past decade, networking
technology has become the most explosive
area of growth in the entire computer
industries.
A network, is a collection of computers and
other hardware components interconnected
by communication channels that allow
sharing of resources and information.
4. Uses of Networks
A network is a set of technologies – including
hardware, software, and media- that can be
used to connect computers together, enabling
them to communicate, exchange information,
and share resources in real time.
Networks allows users to access shared
data and programs almost instantly.
Networks open up new ways to communicate
such as email and instant messaging.
By allowing users to share expensive
hardware resources such as printers,
networks reduce the cost of running an
organization.
5. Uses/ importance of network
Personal communication/ interactive
entertainment:-
Video conferencing – enables real-time
communication over a distance by allowing
people at two or more sites to communicate with
each other by seeing a video picture of the people
at the other side.
Audio/ tele-conferencing- provides an audio link
similar to that of a conventional telephone.
Data-conferencing- enables participants at two or
more sites to have a shared workspace on their
computer desktops.
Easier data backup
6. Types of Networks
LAN - Local Area Networks- A Local
Area Network (LAN) is a relatively small
network that is confined to a small
geographic area, such as a single office or
a building. Laptops, desktops, servers,
printers, and other networked devices
that make up a LAN are located relatively
close to each other. A key characteristic is
that all of the equipment that comprises a
LAN, is owned by a s-ingle entity.
7. Types of networks
Wide Area Networks-A Wide Area
Network (WAN) covers a significantly
larger geographic area than LANs or
MANs. A WAN uses public networks,
telephone lines, and leased lines to tie
together smaller networks such as LANs
and MANs over a geographically
dispersed area. Connecting devices in
different geographic areas together for
information sharing, WANs are an
important piece of enterprise networks.
8. Types of computer networks cont..
Hybrid Networks:-
Campus Area Networks - Networking
spanning with multiple LANs but smaller
than a Metropolitan area network,
MAN. This kind of network mostly used
in relatively large universities or local
business offices and buildings.
9. Wireless - Local Area Network
A LAN, local area networks based on
wireless network technology mostly
referred as Wi-Fi. Unlike LAN, in
WLAN no wires are used, but radio
signals are the medium for
communication. Wireless network cards
are required to be installed in the
systems for accessing any wireless
network around. Mostly wireless cards
connect to wireless routers for
communication among computers or
accessing WAN, internet.
10. Metropolitan Area Network
The term Metropolitan Area Network (MAN) is
typically used to describe a network that spans
a citywide area or a town. MANs are larger
than traditional LANs and predominantly use
high-speed media, such as fiber optic cable, for
their backbones. MANs are common in
organizations that need to connect several
smaller facilities together for information
sharing. This is often the case for hospitals that
need to connect treatment facilities, outpatient
facilities, doctor's offices, labs, and research
offices for access to centralized patient and
treatment information. MANs share many of
the same security threats as LANs, but on a
larger scale.
11. Personal Area Network-A more recent term used to describe
a type of network is a Personal Area Network (PAN). PAN
networks are usually wireless, established in an on-demand or
ad-hoc fashion when needed to communicate between two or
more devices. PAN networks can be used between devices
owned by two different parties, or between two devices owned
by one person, such as a PDA and a laptop or mobile phone.
These networks are usually characterized as short-range, often
limited to 10 meters or less in range.
An example of a PAN technology is Bluetooth wireless
networking. Bluetooth is designed as a cable-replacement
technology, allowing users to discard the serial and USB cables
used by many of today's peripheral devices and rely on a
Bluetooth PAN for communication. Bluetooth PANs support up
to 7 devices in a single network and can be used for proprietary
protocols (such as PDA synchronization) or standards-based
protocols, including Internet access over IP and the Bluetooth
Network Encapsulation Protocol (BNEP).
12. NETWORK STRUCTURE
Server based Networks - As the
name suggests server-based networking is
a network where resources, files and
security are all handled by dedicated
servers. Such systems often require
specialist software such as network
operating systems and hardware such as
print servers.
13. Advantages
Can easily cope with
thousands of users.
Backup, security and
account control are
all central.
Software can be
shared between the
computers.
Disadvantages
If one of the servers
go down all the
users are affected
and it may even
bring the whole
network down.
More expensive to
setup and maintain.
14. Client/Server networks
Client/server systems allow the network to
centralize functions and applications in one or
more dedicated file servers. 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
system provides the mechanism to integrate all
the components of the network and allow
multiple users to simultaneously share the same
resources irrespective of physical location.
15. Advantages
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.
16. Disadvantages
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.
17. Peer-to-peer Networks
Peer-to-peer network 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.
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.
18. Advantages
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
Decentralized - No
central repository for
files and applications.
Security - Does not
provide the security
available on a
client/server network.
19. NETWORK TOPOLOGIES
Topology is the logical layout of cables and
devices that connects the nodes of the network.
Network topologies are categorized into the
following basic types:
bus
star
tree
mesh
20. Bus topology
Bus networks use a common backbone to
connect all devices.
A single cable, the backbone functions as a
shared communication medium that devices
attach or tap into with an interface connector.
A device wanting to communicate with another
device on the network sends a broadcast
message onto the wire that all other devices see,
but only the intended recipient actually accepts
and processes the message.
22. Advantages
Easy to connect a
computer or
peripheral to a linear
bus.
Requires less cable
length than a star
topology.
Disadvantages
Entire network shuts
down if there is a break
in the main cable.
Terminators are
required at both ends of
the backbone cable.
Difficult to identify the
problem if the entire
network shuts down.
Not meant to be used as
a stand-alone solution in
a large building
23. Star Topology
A star topology is designed with each node (file server,
workstations, and peripherals) connected directly to a
central network hub, switch, or concentrator.
Data on a star network passes through the hub, switch,
or concentrator before continuing to its destination.
The hub, switch, or concentrator manages and controls
all functions of the network. It also acts as a repeater
for the data flow. This configuration is common with
twisted pair cable; however, it can also be used with
coaxial cable or fiber optic cable.
25. Advantages
Easy to install and
configure.
No disruptions to
the network when
connecting or
removing devices.
Easy to detect faults
and to remove parts.
Disadvantages
Requires more cable
length than a linear
topology.
If the hub, switch, or
concentrator fails,
nodes attached are
disabled.
More expensive than
linear bus topologies
because of the cost
of the hubs, etc.
26. Tree or Expanded Star
Topology
A tree topology combines characteristics
of linear bus and star topologies. It
consists of groups of star-configured
workstations connected to a linear bus
backbone cable. Tree topologies allow
for the expansion of an existing network,
and enable schools to configure a
network to meet their needs.
27.
28. Advantages
Point-to-point
wiring for individual
segments.
Supported by several
hardware and
software vendors
Disadvantages
Overall length of
each segment is
limited by the type
of cabling used.
If the backbone line
breaks, the entire
segment goes down.
More difficult to
configure and wire
than other
topologies.
29. Mesh Topology
Mesh topologies involve the concept of
routes. Unlike each of the previous topologies,
messages sent on a mesh network can take any
of several possible paths from source to
destination.
Some WANS, most notably the Internet,
employ mesh routing.
A mesh network in which every device
connects to every other is called a full mesh.
30.
31. Advantages
Point-to-point line
configuration makes
identification and isolation
of faults easy.
Messages travel through a
dedicated line, directly to
the intended recipient;
privacy and security are thus
enhanced.
Should a fault occur in a
given link, only those
communications between
that specific pair of devices
sharing the link will be
affected.
Disadvantages
The more extensive
the network, in terms
of scope or of physical
area, the greater the
investment necessary
to build it will be, due,
among other
considerations, to the
amount of cabling and
the number of
hardware ports it will
require. For this
reason, such networks
are uncommon.
32. NETWORK MEDIA
Media refers to the means used to link a network’s
nodes together.
There are many different types of transmission media,
the most popular being twisted pair wire, coaxial cable
and fiber optic.
In wireless networks, the atmosphere itself acts as a
medium because it carries the wireless signals that nodes
and servers use to communicate.
33. Wire-Based Media
Twisted-pair - comes in two varieties: shielded and
unshielded. Unshielded twisted pair (UTP) is the most
popular.
The cable has four pairs of wires inside the jacket. Each pair
is twisted with a different number of twists per inch to help
eliminate interference from adjacent pairs and other
electrical devices.
The tighter the twisting, the higher the supported
transmission rate and the greater the cost per foot.
The EIA/TIA (Electronic Industry
Association/Telecommunication Industry Association) has
established standards of UTP.
34. Twisted Pair cable
Advantages
UTP is less expensive than
dedicated coaxial or fiber.
UTP is physically smaller
than coax and many other
cable types .
UTP is a very easy media
to install and reconfigure .
TP is easy to terminate .
Disadvantages
Susceptible to
electromagnetic
interference and
eavesdroppings
Can produce signaling
delay, known as skew, in
video application that send
information across multiple
parallel signal wires.
35. Wire-Based media cont….
Coaxial Cable-comprises of a central conductor, the part of
the cable carrying the signal, that is surrounded by a
dielectric, or non-conducting insulator, a solid woven metal
shielding layer and a protective plastic outer coating.
36. Coaxial Cable
Advantages
Largely immune to electric
noise
Can carry data at higher
rates over long distances
than UTP.
Installation is relatively
simple though the bulky
and thicker cables are
difficult
Disadvantages
It is susceptible to EMI and
eavesdropping although it
resists EMI better than TP
Reconfiguration is difficult.
37. Fiber Optic Cable
Consists of an extremely thin cylinder of glass called the core,
that is surrounded by a concentric layer of glass known as
cladding.
Light travels along the cable core known as waveguide. The
purpose of cladding is to reflect the light signals back into the
waveguide as efficiently as possible so that the light signal travels
along the waveguide by multiple (internal) reflections.
The center core of fiber cables is made from glass or plastic
fibers. A plastic coating then cushions the fiber center, and
kevlar fibers help to strengthen the cables and prevent breakage.
The outer insulating jacket made of teflon or PVC.
38. It transmits light rather than electrical signal, eliminating
the problem of electrical interference.
This makes it ideal for certain environments that contain a
large amount of electrical interference.
It has also made it the standard for connecting networks
between buildings, due to its immunity to the effects of
moisture and lighting.
Fiber optic cable has the ability to transmit signals over
much longer distances than coaxial and twisted pair. It also
has the capability to carry information at vastly greater
speeds.
39. This capacity broadens communication possibilities to
include services such as video conferencing and
interactive services. The cost of fiber optic cabling is
comparable to copper cabling; however, it is more
difficult to install and modify.
10BaseF refers to the specifications for fiber optic
cable carrying Ethernet signals.
There are two common types of fiber cables -- single
mode and multimode. Multimode cable has a larger
diameter; however, both cables provide high
bandwidth at high speeds. Single mode can provide
more distance, but it is more expensive.
40. NETWORK PROTOCOLS
Protocols are procedures or rules used by
networked computers to communicate. For two
computers to communicate they must have a
protocol in common.
Some of the most common protocols today
include:
TCP/IP- the protocol of the Internet and is
required on any computer that must
communicate across the Internet.
41. IPX/SPX – a proprietary protocol of Novell, IPX/SPX
has been used in most versions of the Netware network
operating system for networking offices throughout the
world. Newer versions of Netware also support TCP/IP
NetBIOS/NetBEUI – a relatively simple protocol that
has no real configurable parameters, NetBIOS/NetBEUI
sends message to every computer that can receive them.
It is an excellent protocol for networking small offices or
homes, but it does not expand well into larger
environments.
42. DATA COMMUNICATION WITH STANDARD
TELEPHONE LINES AND MODEMS
Data communication is the transmission of electronic data over
some media e.g. cables, microwaves
Elements/components of data communication:-
Message – the message is the information (data) to be
communicated
Sender/transmitter – the device that sends the data message
Receiver – the device that receives the data
Medium – transmission medium is the physical path by which a
message travels from sender to receiver e.g. cables wireless
transmission media etc.
Protocol – rules that govern data communication. It represents
an agreement between the communicating devices.
43. Data Transmission
Data may be transferred from one device to another by
means of some communication media.
The electromagnetic or light waves that transfer data from
one device to another device in encoded form are called
signals. Data transmissions across the network can occur in
two forms i.e.:
Analog signal
Digital signal
44. Analog Signaling
The transfer of data in the form of electrical
signals or continuous waves is called analog signal
or analog data transmission.
An analog signal is measured in volts and its
frequency in hertz (Hz).
45. Digital Signaling
The transfer of data in the form of digit is called digital signal
or digital data transmission.
Digital signals consist of binary digits 0 & 1. Electrical pulses
are used to represent binary digits.
Data transmission between computers is in the form of
digital signals.
46. Digital Data Connections
To transfer digital data over analog telephone
lines, computers must use modems.
When a computer sends data, its modem
translates digital data into analog signals for
transmission over standard telephone lines.
At the receiving end, the computer’s modem
converts the analog signals back into digital
data.
Using digital connections, businesses and
homes can transmit data many times faster
than is possible over standard phone lines.
47. Connecting to the internet through
wires
There are many ways to obtain access to the internet. The
method varies according to the type of computer system
being used and the types of connections offered.
Some connections are dial-up, must be initiated every time
you desire internet access.
Other connection types remain open available 24/7
48. Dial-up Connections
Used in homes, small offices and individuals to connect to
the internet by use of telephone lines and a 56kbs modem.
The easiest way to create this kind of connection is by setting
up an account with an internet service provider (ISP).
The ISP maintains bank of modems at its facility to process
the incoming dial-up requests from customers
the computer uses it
modem to dial a telephone number given by the ISP. This
establishes a connection between the computer and the ISP
server.
It is temporary – it begins when ISP’s server “answers” the
call and ends when the PC or ISP’s server “hang up”
49. High speed broadband connections
The term broadband refers to the wide bandwidth
characteristics of a transmission medium and its ability to
transport multiple signals and traffic types simultaneously.
To be considered broadband, the connection must be able to
transmit data at a rate faster than dial up connection.
50. Integrated Service Digital Network
(ISDN) Service
I a digital telephone service that simultaneously transmits
voice, data and control signaling over a single telephone line.
ISDN service operates on standard phone lines but requires a
special modem and phone service.
51. Digital Subscriber Line (DSL)
Service
Similar to ISDN in its use of the telephone network, but it
uses more advanced digital signal processing and algorithms
to compress more signals through the telephone lines.
It provides simultaneous data, voice and fax transmission on
the same line
52. Cable modem
Many cable television companies now use a portion of their
network’s bandwidth to offer internet access through
existing cable Tv connections
This internet connection option is called cable modem
service because of the need to use a special cable modem to
connect.
Cable TV transmit data over coaxial cable which transmits
data as much as 100 times more than common telephone
lines.
User can access internet from his/her computer and watch
cable TV at the same time over the same cable connection
and without the two data streams interfering each other
53. Wireless connections
Wireless networks use high frequency radio signals, infrared
light beams, or lasers to communicate between the
workstations, servers, or hubs. Each workstation and file
server on a wireless network has some sort of
transceiver/antenna to send and receive the data.
Information is relayed between transceivers as if they were
physically connected. For longer distance, wireless
communications can also take place through cellular
telephone technology, microwave transmission, or by
satellite.
54. Wireless standards and
speeds
The Wi-Fi Alliance is a global, non-profit organization that
helps to ensure standards and interoperability for wireless
networks, and wireless networks are often referred to as
WiFi (Wireless Fidelity). The original Wi-Fi standard (IEEE
802.11) was adopted in 1997. Since then many variations
have emerged (and will continue to emerge). Wi-Fi
networks use the Ethernet protocol.
55. Wireless standards and
speeds
Standard Max Speed Typical range
802.11a 54mbps 150 feet
802.11b 11 Mbps 300 feet
802.11g 54 Mbps 300 feet
802.11n 100 Mbps 300+ feet
