Transcript Komunikasi, Jaringan, dan Pengamanannya

Komunikasi, Jaringan, &
Pengamanannya
Williams, B.K, Stacy C. Sawyer (2007).
Using Information Technology: A
Practical Introduction to Computers &
Communications. Seventh Edition,
McGraw-Hill, New York. ISBN-13: 978-007-110768-6
1
Learning Outcomes
Pada akhir pertemuan ini, diharapkan mahasiswa
akan mampu :
• menjelaskan pengertian komunikasi/
telekomunikasi, dan jaringan; perbedaan
antara data analog dan digital; jenis-jenis
media komunikasi,menjelaskan kegunaan
dan jenis-jenis media komunikasi nirkabel,
ancaman dan pengamanan jaringan, serta
teknologi komunikasi di masa depan.
2
Outline Materi
•
•
•
•
•
•
From the Analog to the Digital Age
Networks
Wired Communications Media
Wireless Communications Media
Cyberthreats, Hackers, & Safeguards
The Future of Communications
3
From the Analog to the
Digital Age
• Analog signals use variation
of a wave form to send
information
• The wave forms look like the
sine wave shown at right
• In FM signals the Frequency
is varied (Modulated)
• In AM signals the Amplitude
is varied (Modulated)
• Radios send signals this way
• Light works this way
• Hearing and phones work
this way
• Modems work this way
Sine Wave
1
0.5
0
Amplitude
-0.5
-1
S1
Frequency
6-4
From the Analog to the
Digital Age
Digital Signal
1
Time
6-5
41
37
33
29
25
21
17
13
9
0
5
Data
1
• Digital signals send data in terms
of 1s and 0s
• A digital signal may look like this
one at right
• Notice how the signal goes up
and down abruptly because the
only values that matter are 0 and
1 and the timing of when they
occur
• Computers use digital signals
• Newspaper photographs are
digital since they are made up of
little dots
S1
From the Analog to the
Digital Age
• Since computers use digital signals but phone
lines use analog, modems must translate from
digital to analog, send the signal along the
phone line, then translate back from analog to
digital at the other end
– The process is called “modulation/demodulation”
– Modulation means to translate from digital to analog
– Demodulation means to translate from analog to
digital
– Modems have to do all this just to use standard
analog voice phone lines
6-6
From the Analog to the
Digital Age
• Tape recorders, voices, and musical instruments are
analog while CDs are digital
• To burn a CD from a jam session, the digital recording
equipment must convert from analog to digital
– The analog-to-digital converter samples the sound and converts
the height of the wave to a number
– Samples of the sound wave are taken at regular intervals –
about 44,100 times each second
– Because the digital samples are played back
faster than our ears can react, it sounds to us
like a single continuous sound wave
6-7
From the Analog to the
Digital Age
• Digital sampling is similar to showing movies
– Movies show still pictures (frames)
– But they show them so fast that our eyes can’t react
in time
– So to us the series of still pictures look like continuous
motion
– Did you ever notice in movies when they show car
tires in motion they sometimes seem to move
backwards?
• This is because the tires are moving at a rate that is
incompatible with the frame rate of the movie, so our eyes
think the tires are really moving backwards when the car is
actually moving forward!
6-8
Networks
• A system of interconnected computers,
telephones, or other communications devices
that can communicate with one another and
share applications and data
• Before we had computer networks, people used
“sneakernet” to share data between computers
– Person 1 saved their document to a floppy disk
– Then they walked over to person 2’s desk (wearing
sneakers, of course) and handed over the disk to
person 2
– Person 2 loaded the disk into their computer to read
and edit the document
6-9
Networks
• Since the days of “sneakernet”, networks
have become standard. They enable us to:
– Share peripheral devices such as laser
printers
– Share programs and data
– Use e-mail and other communication
programs
– Backup critical information because it is
stored centrally
– Access shared databases
6-10
Networks
• WAN – Wide Area Network
• Covers a wide geographic area,
such as a country or the world
• Covers a city or a suburb
• MAN – Metropolitan Area
Network
• LAN – Local Area Network
• Connects computers and devices
in a limited geographic area such
as an office, building, or group of
nearby buildings
• Uses wired, cable, or wireless
connections to link a household’s
digital devices
• Uses short-range wireless
technology to connect an
individual’s personal electronics
like cellphone, PDA, MP3 player,
notebook PC, and printer
• HAN – Home Area Network
• PAN – Personal Area Network
6-11
Networks
• Client/Server
– Consists of clients, which are computers that request
data, and servers, which are computers that supply
data
– File servers act like a network-based shared disk
drive
– Database servers store data but don’t store programs
– Print servers connect one or more printers and
schedule and control print jobs
– Mail servers manage email
• Peer-to-Peer
– All computers on the network communicate directly
with each other without relying on a server
– For fewer than 25 PCs
6-12
Networks
• Peer-to-Peer (continued)
– Cheaper than client/server since servers are typically
more expensive than PCs
– There are often problems with knowing who has the
current version of documents and files
– Too slow for use in larger offices
• Legal considerations
– Downloading copyrighted material without paying
violates U.S. copyright laws
– Server-based online file sharing sites such as Napster
have been shut down
– Peer-to-Peer file-sharing sites such as Kazaa, Grokster,
and Gnutella have been more difficult to control since
there is no central server to shut down
– So publishers are suing individual downloaders instead
Watch out!
6-13
Don’t download illegally!
Networks
Intranets, Extranets, VPNs
• Intranets
– An organization’s private network that uses the
infrastructure and standards of the internet and the
web
• Extranets
– Private internets that connect not only internal
personnel but also selected suppliers and other
strategic parties
• Virtual Private Networks
– Private networks that use a public network, usually
the internet, to connect remote sites
6-14
Network
Components
• Connections
– Wired – twisted-pair, coaxial cable, or fiber-optic
– Wireless – infrared, microwave (Bluetooth), broadcast
(Wi-Fi) or satellite
• Hosts & Nodes
– Host: the central computer that controls the network
– Node: a device that is attached to the network
• Packets
– The format for sending electronic messages
– A fixed-length block of data for transmission
6-15
Network
Components
• Protocols
– The set of conventions governing the exchange of
data between hardware and/or software components
in a communications network
– Built into the hardware or software you are using
– Govern the packet design and transmission standards
– Examples are:
•
•
•
•
•
TCP/IP for LANs and internet
AppleTalk for older Mac networks
SIP for Voice over IP (VoIP)
CDMA for cellphones
IPX for older Novell networks
6-16
Network
Packets
• TCP/IP Packets carry four types of information
– Sender’s address (source IP number)
– Address of intended recipient (destination IP number)
– Number of packets the original data was broken into
• This happens because the amount of data the PC is sending
can be much larger than the space in a single packet
• So the data has to get broken up in one or more packets
• Then the packets have to be assigned a number like 1 of 6, 2
of 6, 3 of 6, 4 of 6, 5 of 6, and 6 of 6
– Packet number and sequence info for each packet
• Packets may arrive out of order (1, 6, 3, 2, 5, 4 for example)
• This information is used to resequence the packets and put
them back in the correct order (1, 2, 3, 4, 5, 6) so they can be
read
6-17
Network
Devices
• Daisy
Chain
• Used in peer-to-peer networks – direct
connections from one PC to the next
• Hub
• Used in small LANs to connect PCs and LAN
segments to each other. Forwards to all ports
• Switch
• Used in larger, busy LANs – faster than hubs
because it forwards only to correct
destination
6-18
Network
• Bridge
• Gateway
• Router
• Backbone
Devices
• Used to connect two networks of
the same type
• Connects two networks of different
types
• Connects multiple LANs together.
Routers are the internet backbone
• The main route that connects all
the gateways, routers, and other
computers in an organization
19
Network
Topologies
• Bus – all nodes are connected to a single wire or cable
• Ring – all nodes are connected in a continuous loop
• Star – all nodes are connected through a central host
6-20
Network
Packet Collision Schemes
• Collisions happen when two data packets are
going opposite directions on shared media
• Ethernet – deals with collisions
– All devices send data at once
– Collisions happen regularly
– Data is simply resent until it arrives
• Token ring – avoids collisions
$$$
– Devices take turns sending data
Pricier than
– Token is sent around the ring
Ethernet
– Wait to get the token, then send data
6-21
Wired Communications Media
• Communications media carry signals over a
communications path
– Twisted-Pair Wire
• 2 strands of insulated copper wire twisted around each other
• Twisting reduces interference (crosstalk) from electrical
signals
• Data rates are 1 – 128 Megabits per second
– Coaxial Cable
• Insulated copper wire wrapped in a metal shield and then in
an external plastic cover
• Used for cable TV and cable internet electric signals
• Carries voice and data up to 200 megabits per second
6-22
Wired Communications Media
• Communications media continued
– Fiber-optic cable
• Dozens or hundreds of thin strands of glass or
plastic that transmit beams of light, not electricity
• Can transmit up to 2 gigabits per second
• More expensive than twisted-pair or coax
• Lighter and more durable than twisted-pair or coax
• More difficult to tap into than twisted-pair or coax
6-23
Wired Communications
Media for the home
• Ethernet
– Pull Cat5 cables through the house (yourself or contractor)
– Connect to PC’s Ethernet network interface card (nic)
– For several PCs, get a hub or switch to connect them all
– 10 or 100 megabits per second
• HomePNA
– Uses existing telephone wiring and jacks
– Requires HomePNA nic in your PC
– Speeds of 10 – 240 megabits per second
• Homeplug
– Uses existing home electrical lines
– Speeds of 14 megabits per second
6-24
Wireless Communications Media
• Electromagnetic spectrum of radiation is the basis of all
telecommunications signals
– Includes the longest radio waves (9 kHz) and audio waves (sound),
up through gamma rays that come from nuclear decay (thousands of
gigahertz)
– Radio-frequency spectrum is the part of the electromagnetic
spectrum that we use for radio communication
6-25
Wireless Communications Media
Bandwidth
• Narrowband (or Voiceband)
– Used for regular telephone communications
– Transmission rate < 100 kilobits per second
• Medium Band
– Used for long-distance data transmission or to connect
mainframe and midrange computers
– Transmission rate 100 kb to 1 megabit per second
• Broadband
– For high-speed data and high-quality audio and video
– Transmission rate 1 megabit per second to 100 megabits
per second
• US households get 4 – 5 MB while Japanese get 100 MB
per second
6-26
Wireless Communications
Media
• Infrared Transmission
– Sends signals using infrared light
– Frequencies are too low to see (1-4 Mbits per
second)
• Broadcast Radio
– AM/FM, CB, ham, cellphones, police radio
– Sends data over long distances using a transmitter
and a receiver
• Microwave Radio
– Superhigh frequency radio waves (1 gigahertz)
– Requires line-of-sight transmitters and receivers
• Communications Satellites
6-27
Wireless
Communications Media
• Communications Satellites
– These are microwave relay stations in orbit around the earth
- Uplinking: transmitting a signal from ground station to a satellite
– Cover broad service area
– Cost $300 million to $700 million each + launch costs
– Can be placed at different heights: GEO, MEO, LEO
• GEO – geostationary earth orbit
– 22,300 miles up above earth
– Always above equator
• MEO – medium-earth orbit
– 5,000 – 10,000 miles up
• LEO – low-earth orbit
– 200 – 1,000 miles up
– Has less signal delay than GEO, MEO satellites
6-28
Wireless Communications Media
GPS
• Global Positioning System
– 24 earth-orbiting satellites continuously transmitting timed
radio signals
– Each satellite circles earth twice each day at 11,000 miles
up
– GPS receivers pick up transmissions from up to 4 satellites
and pinpoint the receiver’s location
– Accurate within 3 – 50 feet, with a norm of 10 feet
accuracy
– GPS receivers contain map files that are displayed based
on the GPS position to guide users
– Many GPS receivers have speech chips, too
6-29
Wireless Communications Media
One-way Pagers
• One-way pagers are radio receivers that receive
data sent from a special radio transmitter
– Radio transmitter sends out signals over the special
frequency
– Pagers are tuned to that frequency
– When a particular pager hears its own code, it
receives and displays the message
Discussion Question: Why do airplane rules require you to turn off pagers and
cellphones during flight?
Answer: Pilots use radar and radio to determine their position and
communicate with ground control. Pager and cellphone signals use radio, too,
and competing signals can interfere with each other
6-30
Wireless Communications Media
Long-Distance Wireless
• Two-way pagers: Blackberry and Treo
• 1G: First Generation Cellular
– Analog cellphones
– Designed for voice communication using a system of
hexagonal ground-area cells around transmitterreceiver cell towers
– Good for voice – less effective for data due to
handing off
• 2G: Second Generation Cellular
– Use same network of cell towers to send voice and
data in digital form over the airwaves
– Required digital receivers on original analog
celltowers
6-31
Wireless Communications Media
2G Wireless
• There are two competing, incompatible
standards
– CDMA – Code Division Multiple Access
• Transmission rates 14.4 kilobits per second
• Used by Verizon and Sprint
– GSM – Global System for Mobile Communications
• Transmission rates of 9.6 kilobits per second
• Used by Cingular and T-Mobile, as well as Western Europe,
Middle East and Asia
• US GSM and European GSM use different frequencies
6-32
Wireless Communications Media
2.5G Wireless
• Data speeds of 300–100 kilobits per
second
– GPRS – General Packet Radio Service
• An upgrade to 2.5G
• Speeds of 30 – 50 kilobits per second
– EDGE is Enhanced Data for Global Evolution
• A different 2.5G upgrade
• Speeds of up to 236 kilobits per second
6-33
Wireless Communications Media
3G Wireless
• Third generation wireless
– High speed data: 144 kilobits per second up to 2
megabits per second
Discussion
– Accept e-mail with attachments
Question: If your
cellphone can
– Display color video and still pictures
download and
– Play music
play music, do
you still need an
– Two important upgrades:
• EV-DO – Evolution Data Only
i-pod?
– Average speeds of 400 – 700 kilobits per second, peaks of 2
megabits per second
• UMTS – Universal Mobile Telecommunications System
– Average speed of 220 – 320 kilobits per second
6-34
Wireless Communications Media
Short-range Wireless
• Local Area Networks
– Range 50 – 150 feet
– Include Wi-Fi (802.11) type networks
• Personal Area Networks
– Range 30 – 32 feet
– Use Bluetooth, Ultra wideband, and wireless USB
• Home Automation networks
– Range 100 – 250 feet
– Use Insteon, Zigbee, and Z-Wave standards
6-35
Wireless Communications Media
Short-range Wireless
• Wi-Fi (802.11) networks
–
–
–
–
–
–
Wi-Fi b, a, and g correspond to 802.11b, 802.11a, and 802.11g
802.11 is an IEEE wireless technical specification
802.11b is older, transmits 11 megabits per second
802.11a is faster than b but with weaker security than g
802.11g is 54 megabits per second and transmits 50 ft
Wi-Fi n with MIMO extends range of Wi-Fi using multiple
transmitting and receiving antennas – 200 megabits per second
for up to 150 ft
• Warning! Security is disabled by default on Wi-Fi
6-36
Wireless Communications Media
Short-range Wireless
• Wi-Fi Security
– Why is it disabled by default?
• So non-technical users can get Wi-Fi working more easily
– Why should this bother me?
• A person with a $50 antenna can eavesdrop on everything
your computer sends over wireless from a block or two away
• This is called “wardriving”
– To read more about this problem, follow these links
• http://www.webopedia.com/TERM/W/wardriving.html
• http://www.wardriving.com/
6-37
Wireless Communications Media
Personal Area Wireless
• Bluetooth
– Short-range wireless standard to link cellphones, PDAs,
computers, and peripherals at distances up to 30 ft
– Named after King Harald Bluetooth, the Viking who
unified Denmark and Norway
– Transmits 720 kilobits per second
– When Bluetooth devices come into range of each other,
they negotiate. If they have information to exchange,
they form a temporary wireless network
– Bluetooth can also be used to eavesdrop on networks
– Turn it off on your cellphone unless you need it at that
time
6-38
Wireless Communications Media
Personal Area Wireless
• Ultra Wideband (UWB)
– Developed for military radar systems
– Operates in 480 megabit per second range up to 30 ft
– Uses a low power source to send out millions of
bursts of radio waves each second
– 100 times as fast as Bluetooth
• Wireless USB
– USB is the most used interface on PCs
– The wireless version could be a hit
– Range of 32 ft and maximum data rate of > 480
megabits per second
6-39
Wireless Communications Media
Short-Range Wireless for Home
• Insteon
– Combines electronic powerline and wireless technology
– Can send data at 13.1 kilobits per second with 150 ft range
– Replaces X10
• ZigBee
– Entirely wireless very power-efficient technology
– Can send data at 128 kilobits per second with 250 ft range
• Z-Wave
– Entirely wireless power-efficient technology
– Can send data at 127 kilobits per second to range of 100 ft
– Allows you to remotely program your house!
6-40
Cyberthreats, Hackers, &
Safeguards
• Problem: internet was begun to foster
collaboration among universities and scientists.
They trusted each other. No security was built into
the internet.
• Problem: the internet is open-access and is used
by some people who are not trustworthy, who take
advantage of the lack of built-in safeguards.
• Problem: Most people connect to the internet and
use their computers in LANs. All it takes is one
computer on a LAN that has been compromised
for all computers on it to be vulnerable.
6-41
Cyberthreats, Hackers, &
Safeguards
• Denial of Service Attacks
– Consist of making repeated requests of a computer or
network device, thereby overloading it and causing
legitimate requests to be ignored
– Used to target particular companies or individuals
• Worms
– A program that copies itself repeatedly into a
computer’s memory or disk drive
– May copy itself so much it crashes the infected
computer
– Famous worms include: Code Red, SQL Slammer,
Nimda, MyDoom, Sasser
– Primarily target PCs running Microsoft Windows
6-42
Cyberthreats, Hackers, &
Safeguards
• Viruses
– A deviant program that hides on a floppy, hard
drive, CD, or e-mail that causes unexpected side
effects such as destroying or corrupting data
– Viruses self-replicate and try to secretly distribute
themselves to other systems
– Famous viruses include the “I Love You” virus
– Viruses are published at the rate of about one per
day
– To see what the latest ones are, go to
• http://www.symantec.com/avcenter/vinfodb.html
6-43
Cyberthreats, Hackers, &
Safeguards
• Trojan Horses
– Programs that pretend to be a useful program
such as a free game or screensaver.
– Carry viruses or malicious instructions that
damage your computer or install a backdoor
or spyware
– Backdoors and spyware allow others to
access your computer without your
knowledge
6-44
Cyberthreats, Hackers, &
Safeguards
• How they spread
–
–
–
–
–
–
Via e-mail attachments
By infected floppies or CDs
By clicking on infiltrated websites
By downloading from infected files from websites
Through infiltrated Wi-Fi hotspots
From one infected PC on a LAN to another
• What can you do about it?
– Install anti-virus software and subscribe to the
automatic anti-virus update service
6-45
Cyberthreats, Hackers, &
Safeguards
• Hackers are either
– Computer enthusiasts, people who enjoy learning about
programming and computers (good)
– People who gain unauthorized access to computers or
networks, often for fun or to see if they can (not good)
• Crackers
– Malicious hackers who break into computers for
malicious purposes
• Script kiddies are technically unsophisticated teenagers who
use downloadable software for perform break-ins
• Hacktivists are hacker activists who break into systems for a
political purpose
• Black-hat hackers are those who break into computers to
steal or destroy information or to use it for illegal profit
• Cyberterrorists attack computer systems so as to bring
physical or financial harm to groups, companies, or nations
6-46
Cyberthreats, Hackers, &
Safeguards
• Safeguards
– Use antivirus software, and keep it current
– Install a firewall to monitor network traffic and filter out
undesirable types of traffic and undesirable sites
– Use robust passwords –
• Minimum 8 characters with letters, numbers, characters
• 4cats is not a good password, but f0UrK@tTz is
– Install antispyware software
– Encrypt financial and personal records so only you
can read them
– Back up your data, so if your PC is attacked and must
be reformatted, you can restore your data
– Never download from a website you don’t trust
– Consider Biometric authentication
6-47
Cyberthreats, Hackers, &
Safeguards
• Encryption
– The process of altering readable data into unreadable
form to prevent unauthorized access
• Uses powerful mathematical ciphers to create coded
messages that are difficult to break
– Two forms:
• Private Key encryption means the same secret key is used
by both the sender and receiver to encrypt and decrypt a
message
• Public Key encryption means that two keys are used
– The public key of the recipient is published and is used by the
sender to encrypt the message
– The private key of the recipient is secret and is the only way to
decrypt the message
6-48
Future of Communications
• This is a big area of development
• There is a lot of money to be made from faster
and more secure broadband communications
• Areas of development include
– Global high-speed low—orbital satellite networks for
rural internet and voice connectivity
– 4G wireless technology
– Photonics to speed up fiber-optic lines
– Software-defined radio
– Grid computing
6-49
Kesimpulan
50