Transcript Networks

Strand 3.3 of IT Systems
Networks
What is a network?
A Network is a collection of computers
and devices connected together, often
wirelessly via communication devices
and transmission media, allowing
computers to share resources.
Advantages of Networking
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Facilitating communications
Sharing hardware
Sharing data and information
Sharing software
Transferring funds
LAN’s, MAN’s, WAN’s & BAN’s
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Networks usually fall under the 3
categories:
– Local Area Network (LAN)
– Metropolitan Area Network (MAN)
– Wide Area Network (WAN)
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Future developments in Networks
– Body Area Networks (BAN); where a
series of wearable or implented body
sensors can turn the human body into a
router for wireless communication devices,
allowing data to be transmitted from the
body to technology in order to achieve a
task.
– For example, saving a word processing
document to a portable wrist device and
than walking to a touch activated printer.
Local Area Network (LAN)
a LAN is a network that connects
computers and devices in a limited
geographical area such as a home, school
computer lab, office building or closely
positioned group of buildings around
university or college.
 Node – each computer or device on a
network, such as a desktop, printer/fax,
large hard disks. Nodes are connected by
via cables.
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Wireless LAN (WLAN)
Is a LAN that has no physical connection
between nodes.
 Each node such as a computer or other
devices must have wireless capability,
wireless network card, USB network
adapter, Express Card module, PC Card
or flash card. E.g. Wireless access point
like a wireless modem for Internet access,
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Metropolitan Area Network (MAN)
high speed network that connects local
area networks in a city or town and
handles the communications activity
across that region. Made up of one or
more LAN’s, but covers a smaller
geographic area compared to a MAN.
 MAN network providers are telephone
companies, cable TV operators and other
organisations associated with MAN.
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Wide Area Network (WAN)
Covers a large geographic area like a city,
country, state, emirate or globally using
communication channels that combine
many types of media such as telephone
lines, cables and radio waves.
 The Internet is the largest WAN.
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Network Architecture
Is the layout of computers, devices and
various media in a network.
 Can be categorised as:
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◦ Client/server
◦ Peer-to-Peer
Client/Server Network
use to network 10 or more computers
 Where one or more computers act as a
server (master computer) or host computers
 A Client is other computers or mobile
devices on the network that rely on the
server for their resources or instructions in
order to use other devices like a printer. For
example, a server might store a database of
customers. The clients on the network access
the customer database on the server.
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Client/Server Network
Advantages:
Centralized management, Strong Security, Expansion and Create redundant
systems
Disadvantages:
Expensive, difficult to implement and Central Point of failure
Peer-to-Peer Network
use to network 10 or less computers
 Each computer or Peer can work as a
server and as a client
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Peer-to-Peer Network
Advantages:
Lower Cost, Easy to setup and good for temporary network setup
Disadvantages:
Limited growth, No central location, Weak Security, To many passwords
Internet Peer-to-Peer Network
A network that allows users to access each
other’s hard disk and exchange files directly
over the Internet.
 Sometimes referred to as a file sharing network
 Examples are:
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Bit Torrent
Gnutella
Kazaa
Lime Wire – used to swap music files via Web
Business Benefits to P2P
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Companies & employees exchange files
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In e-commerce, it allows buyers & sellers to
share information like database records
Network Topologies
Topology – is the physical layout of
computers and devices in a
communications network
 3 network topologies are:
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◦ Bus Network
◦ Ring Network
◦ Star Network
Bus Network
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This network is made up of:
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A bus
Cables
Personal computers
Other devices like a printer, modem, switch/hub
Bus Network
◦ Advantages of a bus network are that
computers can connect and disconnect
without affecting the other machines.
◦ Disadvantages of a bus network are
bandwidth, if two machines are hogging the
bus as they exchange some huge files, then
the others have to wait.
◦ problem becomes worse as the network
grows. So a bus is good for small to medium
sized networks.
Ring Network
This network is made up of:
 Cable connections
 Server
 Client computers
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Other devices like a printer, modem, switch/hub
Ring Network
◦ Advantages of a bus network are: that it is simple
to set up with no complicated addressing needed.
So its useful for small office networks
◦ Disadvantages of a bus network are: is that if one
of the links is broken then computers on one side
of the break can't communicate with those on the
other side.
Star Network
This network is made
up of:
 Switch/hub
 Server
 Client computers
 Cable connections
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Other devices like a
printer, modem, switch/hub
Star Network
◦ Advantages of a bus network are: that each
link to the server is independent of the
others so the computers do not have to share
bandwidth with each other (unlike a bus
arrangement).
◦ Disadvantages of a bus network are: that
more cabling is needed that other network
arrangements.
◦ if the central server is broken, then the whole
network is broken.
Intranets
What is the difference between the Internet and an
Intranet?
 An Intranet is a private network within a company
and it is only available to staff or members of the
organisation.
 The Internet is a computer network that connects
computers worldwide or public network
 An Intranet example are applications containing
information related to a company, for example,
policies, procedures, rules, contact lists, social events,
newsletters etc.
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What is an extranet?
An Extranet is a computer network that
allows businesses outside the central
company to access their network.
 For example, the car company Ford has its
own (huge) internal computer network that
spans the world. However, it allows some of
its main suppliers direct access to a small
part of the network in order to allow them
to share data with Engineers and Purchasing
staff.
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Network Communication Standards
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Network standards are
guidelines that specify
the way computers
access the medium to
which they are attached,
the types of medium
used, the speeds used
on different types of
networks, and types of
physical cable and/or
the wireless technology
used.
Protocols
A protocol is a set of rules for the exchange
of data between a terminal and a computer
or between 2 computers.
 For example transmission speed. If one
machine is talking at 56,600bps and the
other is listening at 28,800 bps, the message
doesn’t get through.
 Protocols include prearranged messages
such as “are you ready?” ; “I am about to
start sending a data file”
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Protocols
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Protocols for both wired and wireless networks include:
1. Ethernet
2. Token ring
3. TCP/IP
4. Wi-Fi
5. Bluetooth
6. UWB
7. IrDA
8. RFID
9. WiMAX
10. WAP
Ethernet
A network standard that specifies no central
PC or device on the network (nodes) when
data is transmitted
 Is based on bus topology, but can be wired
on a star pattern
 Controls how devices (e.g. Modems, routers,
ec) share access to media (e.g. Cables &
lines) and how devices transmit data over
communications channel.
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Ethernet
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Examples of Ethernet
are cables that plug
into PC’s and other
devices like printers
for networks
Token Ring
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A token is a series of bits
that function like a ticket
Only a device at a time with a
token can transmit data over
the network
Token ring is based on ring
topology
Physical configuration of a
network includes cables,
network cards and devices
Data transfer rate can either
4 Mbps, 16Mpbs, 100 Mbps or
1 Gbps
TCP/IP
Transmission Control Protocol/Internet Protocol (TCP/IP)
 TCP is responsible for checking that data has been delivered
correctly from your computer (the client) to another
computer (the server). If data is lost, then TCP requests that
the data is re-sent.
 packets are small pieces of a message divided up for
transmission
 PC’s use TCP/IP for uploading web pages over the Internet.
Web page is broken up into packets with its own address
and reassembled once the web page arrives at your
computer.
 Routers send packets over the Internet from web server to
your PC
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How TCP/IP sends data as Packets
Wi-Fi
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Wireless fidelity or 802.11
Uses radio technology within a LAN
802.11 standards are 2 wireless devices communicate over
the air
Wi-Fi works in conjunction with TCP/IP when accessing the
Internet
Wi-Fi network is popular with hot spots, where users can
connect to the Internet in shopping malls
Many homes & shops use Wi-Fi to network computers &
devices wirelessly
In open areas Wi-Fi range is up to a range of 30 meters or
more
University’s/colleges use Wi-Fi mesh network
How Wi-Fi technology works
Bluetooth
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Bluetooth or 802.15
Wireless technology that
enables Mobile phones,
Handheld computers &
PC’s to communicate
with each other
regardless of OS
Uses radio technology
like Wi-Fi to transmit
data only up to a range
of 10 meters
Used for room-size
personal area networks
(PAN)
A Bluetooth devices contains a small
chip that allows it communicate with
other Bluetooth devices. If device is
not Bluetooth enabled, than a
Bluetooth wireless port adapter will
convert existing USB port into a
Bluetooth port
Ultra-Wideband
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A low power, short-range radio wave technology
Transmits ultra-high-speed signals over a wide
spectrum of frequencies
At 10 meters, data is transferred at 110 Mbps
up to 2 meters, data is transferred at 480 Mpbs
Best suited for transmission of large files like video,
graphics & audio
For example files are transferred wirelessly from a
digital video camera to a media player or displaying a
slide show on a projector.
IrDA
Is infrared technology
 Has a 1 meter range
 Approximate speed of 9600 bps
 Used for data exchange between personal
digital assistants (PDA’s)
 Requires a clear line of sight between
sending and receiving data.
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Radio Frequency Identification
Radio frequency identification
 A reading tool that uses radio waves to communicate with
RFID tags
 RFID tag or transponder broadcasts its unique ID number to
the reader, which digitizes the info for input into a computer
 RFID tags or transponders can be cards, car sticker on a
windscreen, grain of rice, bar codes on books, etc..
 The tag consists of an antenna and memory chip that
transmits information via radiowaves
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How
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RFID Toll Works
Student task: Read page 481, fig 9-21 and
create a flow chart on how road tolls work
using RFID standards. E.g. Refer to road tolls
in Dubai. Email your work through to Mr.
Greg
RFID versus Bar Codes
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Bar code reader – a tool that uses light to read universal product codes,
inventory codes and other codes created out of patterns of variable-width
bars. E.g. Used at check outs in supermarkets
Bar code readers are attached to point-of-sale (POS) terminals
POS send scanned information to a computer, it determines price,
calculates taxes and totals and records transaction
Reading text from books, magazines & other printed documents is challenging
RFID readers use radio waves to communicate with RFID tags
RFID tags can be read from a greater distance
Hard plastic antitheft cards attached to clothes at shops contain RFID tags
for security purposes
RFID tags used to identify books, goods on pallets, etc
RFID tags are designed to be read by computers quickly and accurately
WiMAX
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Worldwide interoperability for microwave access or
802.16
Is a network standard used for wireless devices
A wireless alternative to cable or DSL services
A powerful tool for connecting Wi-Fi networks
Provides wireless broadband Internet access at a
good price over long distances to business and home
users
Many mobile devices have built in WiMAX standards
WiMAX Towers
WiMAX towers have a 48 km radius, connects
to the Internet or to another WiMAX tower
WAP
Wireless application protocol
 Determines how mobile
devices like smart phones can
display content of Internet
services such as Web, email
and chat rooms.
 Uses a client/server network
 Mobile devices contain client
software that connects to the
server of the ISP
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Communications Software
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Consists of programs that:
1. Help users establish a connection to a another
computer or network
2. Manage the transmission data, instructions and
information
3. Provide an interface for users to communicate
with one another
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Examples of application software for
communications are e-mail, FTP, web
browser, chat rooms, instant messaging,
video conferencing and VoIP
Communications over the Network
Public switched telephone network (PSTN)
is a worldwide telephone system that
handles voice-oriented telephone calls
 Data, instructions and information are
transmitted over telephone network using
dial up lines or dedicated lines.
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Dial up Lines
Is a temporary connection that uses one or more
analog telephone lines for communicates
 Costs more to operate than a phone call
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Dedicated Lines
Is a type of always on connection that is
established between two communications
devices
 Five types of dedicated lines are:
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ISDN lines
DSL
FTTP
T-carrier lines
ATM
ISDN Lines
ISDN stands for integrated
services digital network
 Used for small business and
home users
 Is a standard for digital
transmission of data over
standard copper telephone lines
 Can carry 3 or more signals
through a telephone line, by
multiplexing the signal
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DSL
Digital subscriber line
 Transmits at fast speeds on copper telephone
wires
 ADSL is the most popular DSL type
 ADSL-asynchronous digital subscriber line
 ADSL supports faster transfer speeds when
receiving or downstreaming data and
sending or upstreaming data
 ADSL is ideal for Internet access
 Do ADSL connections transmit data
downstream faster than upstreaming?
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FTTP
Fiber to the premises
 Uses fiber optic cables to provide extremely
high-speed Internet access
 2 types of FTTP are FTTH & FTTB
 FTTH for home users
 FTTB for organisations
 With FTTP service, an optic terminal receives
signals and transfers them to a router
connected to your computer.
 Will become more affordable when the cost
of fiber optics decreases
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T-Carrier Lines
Are long distance telephone lines that carry many signals over
single communication lines
 Uses multiplexing, to provide very fast data transfer rates
 T1 line is the most popular with Internet access providers,
when providing services to homes and small businesses
 T1 gets slower when more users are added
 T3 is equal in speed to T1
 T3 lines are very expensive
 T3 include large organisations, telecommunication companies
 WAN like the Internet use T3 lines
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ATM
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Asynchronous transfer mode
Carries voice, data, video and multimedia
Transfer data at very high speed
Used for Internet,
Gradually replacing T3 lines as the standard for data
transmission
Communications Devices
Is any type of hardware capable of transmitting
data, instructions, information between a
sending device and a receiving device.
 At the sending device a set of instructions are
initiated to transmit data, instructions or
information
 At the receiving device the transmission of
data, instructions or information is received
from other devices.
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Types of communication devices
Dial-up modems
 Digital modems; ISDN, DSL & Cable
 Wireless modems
 Network cards
 Wireless access points (WAP)
 Routers
 Hubs
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Dial-Up Modems
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Converts digital signals to analogue signals, so data to travel
along telephone lines
Dial-up means connecting to the Internet or the WorldWide-Web by using an old-fashioned analogue modem
Dial-up connection is very slow at 56kbs compared to
broadband 512kb and more.
Other devices than computers like fax-machine can convert
scanned digitised image into an analog signal that is sent to a
recipient’s fax machine.
Digital Modems
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Digital modem sends and receives data to and from a digital
line
Being ISDN, DSL and Cable modems
ISDN modem- sends digital data and information from a
computer to an SIDN line and receives digital data and from
an IDSN line
DSL – Digital subscriber line
 Transmits at fast speeds on copper telephone wires
offer Internet broadband speeds and beyond.
The more commonly used abbreviation is ADSL
Cable modems – digital modem that sends and receives digital
data over the cable television network
Wireless Modems
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It just helps network connect to the internet wirelessly, via
technology that uses Radio frequencies to transmit and
receive data.
A popular wireless network technology is called "Wi-Fi".
Wireless modems can be available with USB flash drive and
other PC cards etc.
Easy to connect and portable and easy to use
Connection can be interrupted and could be slow because
of range.
Network Cards
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Communication device that enables a computer or device that
does not have a built in networking capability to access to a
network.
There are network cards that provide wireless data
transmission which are called wireless network cards
Network card follows the guidelines of a particular network
communications standard such as Ethernet or token ring.
Network cards are required in every machine connected to
the network.
They allow the signal from the network to be transmitted to
the machine – this could be via a fixed cable, infra red or radio
waves.
NICs slot into the Motherboard
Wireless Access Points
A central communication
device
 allows computers and devices
to transfer data wirelessly
among themselves
 Transfers data wirelessly to a
wired network
 WAP allows students to
wirelessly work from
classrooms, a library and other
locations
 To access a network, a laptop
or mobile device must have a
built-in wireless capability or a
wireless network card
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Routers
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A router allows multiple connections
Many are protected via firewalls of different strengths
Some routers include abilities to print via wireless
connectivity
Can use a DSL modem or a normal cable modem
A router will accept incoming data packets arriving from a
connected L AN,
router reads the destination address embedded in each data
packet and works out which of the other LANs is connected
to the best one to use for that particular data packet.
Hubs and Switches
network hub is a hardware device that connects multiple
computers in a network.
 It allows networked computers to share data packets.
 A switch is a component which is used within a computer
network.
 A switch has a number of ports and it stores the addresses of
all network devices that are directly or indirectly connected to
it on each port.
 As a data packet comes into the switch, its destination address
is examined and a direct connection is made between the
sending and receiving machines
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Home Networks
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Connects computers and devices together
Home networks have the following capabilities:
◦ Connect to the Internet
◦ Share a single high-speed Internet connection
◦ Access files and programs on the other computers in the
home
◦ Share peripherals such as a printer, scanner, external hard
drive, optical disc drive
◦ Connect game consoles to the Internet
◦ Subscribe to and use VoIP
Wired Home Networks
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A home network can be wired or wireless or both.
Wired home networks are:
◦ Ethernet network
◦ Powerline cable network
◦ Phoneline network
Wireless Home Networks
Most wireless home networks use a Wi-Fi
networks that sends data up to 1,500 ft.
 Computers accessing a Wi-Fi network use
built in wireless networking capabilities or
wireless network cards
 In wireless networks one PC will connect to a
router/wireless access point
 Walls, ceilings and electrical can run
interference with wireless network signals
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Communications Channel
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Is the transmission media on which data, instructions or
information travel in a communications systems.
Bandwidth – being the amount of data, instructions,
information that can travel over a communications channel
Latency – the time it takes a signal to travel from location to
the next in a network
Transmission media – are materials that can carry a signal e.g.
Fiber optics, copper twisted wires, etc
Broadband - can carry multiple channels of data. Each
channel can carry a different signal e.g. moving images, sound
or text. With broadband more data can be carried at the
same time.
Physical transmission Media
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Physical transmission media used in communications include:
◦ Twisted-pair cable
◦ Coaxial cable
◦ Fiber-optic cable
Wireless Transmission Media
More convenient than installing cables
 Types of wireless transmission media include:
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Infrared
Broadcast radio
Cellular radio
Microwave radio
Communications satellite
NETWORK REVIEW
Page 503 of Discovering Computers
 true/false questions1-11
 multiple choice questions 1-8
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