Transcript LANs and WLANs

Chapter 5
LANs and WLANs
Computer Concepts 2012
5 Chapter Contents
 Section A: Network Building Blocks
 Section B: Wired Networks
 Section C: Wireless Networks
 Section D: Using LANs
 Section E: Security Through Encryption
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5 FastPoll True/False Questions
Answer A for True and B for False
 050100 In a network, a server is a computer that provides
services to other computers called peers.
 050200 Star, ring, and mesh are examples of network
topologies.
 050300 When you send an e-mail message over a network,
it is chopped up into packets.
 050400 The IP address assigned to your computer on the
Internet is derived from your computer’s MAC address.
 050500 Some network technologies use home telephone or
electric cabling for computer networks.
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5 FastPoll True/False Questions
Answer A for True and B for False
050600 The most popular type of wired network is
Ethernet.
050700 Network speeds are measured in
megabytes and gigabytes.
050800 Many wireless networks use radio waves to
transmit data.
050900 Bluetooth is a wireless technology used for
WANs.
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5 FastPoll True/False Questions
Answer A for True and B for False
051000 A wireless infrastructure network uses a
centralized broadcasting device, such as a wireless
access point or router.
051100 Wireless networks are less secure than
wired networks.
051200 WEP, WPA, and PSK are examples of WiFi networks.
051300 Public key encryption uses a public key to
encrypt messages, but a private key is required to
decrypt messages.
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SECTION
A
Network Building Blocks
 Network Classifications
 LAN Standards
 Network Devices
 Clients, Servers, and Peers
 Physical Topology
 Network Links
 Communications Protocols
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5 Question
052100 Networks come in many sizes and use
many different technologies, yet they all need to
communicate with each other. What is the key to
network intercommunication?
– A. Packet switching
– B. Network protocols
– C. Network topology
– D. Peer-to-peer technology
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5 Network Classifications
 Personal Area Network (PAN) – interconnection of personal
digital devices or consumer electronics
 Local Area Network (LAN) – usually connects computers in a
single building
 Metropolitan Area Network (MAN) – public high-speed
network with range of about 50 miles
 Wide Area Network (WAN) – covers a large geographical
area and typically consists of several smaller networks
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5 LAN Standards
 LAN technologies are standardized by the Institute of
Electrical and Electronics Engineers (IEEE) Project 802 –
Local Network Standards
– IEEE 802.3
– ARCnet
– Token Ring
– FDDI
– Ethernet
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5 Network Devices
 Each connection point on a network is referred to as a node
 To connect to a LAN, a computer requires network circuitry,
sometimes referred to as a network interface card (NIC)
 A networked peripheral, or network-enabled peripheral, is
any device that contains network circuitry to directly connect
to a network
 A network device, or network appliance, is any electronic
device that broadcasts network data, boosts signals, or
routes data to its destination
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5 Network Devices
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5 Clients, Servers, and Peers
 Network devices can function as clients or as servers
– Application server
– File server
– Print server
 Networks that include one or more servers can operate in
client/server mode
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5 Physical Topology
 The arrangement of devices in a network is referred to as its
physical topology
– Star
– Ring
– Bus
– Mesh
– Tree
 Two similar networks can
be connected by a device
called a bridge
 Gateway is a generic term
for any device or software
code used to join two networks
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5 Network Links
 A communications channel, or link, is a physical path or
frequency for signal transmissions
 Bandwidth is the transmission capacity of a communications
channel
– Broadband
– Narrowband
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5 Communications Protocols
 Rules for efficiently transmitting data from one network node
to another:
– Divide messages into packets
– Affix addresses to packets
– Initiate transmission
– Regulate flow of data
– Check for transmission errors
– Acknowledge receipt of transmitted data
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5 Communications Protocols
 A packet is a “parcel” of
data that is sent across a
computer network
– Circuit-switching
technology vs. packet
switching technology
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5 Communications Protocols
 Every packet that travels over a network includes the
address of its destination device
 A MAC address is a unique number assigned to a network
interface card when it is manufactured
 An IP address is a series of numbers used to identify a
network device
 IP addresses can also be obtained through DHCP
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SECTION
B
Wired Networks
 Wired Network Basics
 Ethernet
 Ethernet Equipment
 Ethernet Setup
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5 Question
052200 Suppose you’re setting up a network in your
home or apartment. You want all of the computers
to access the cable modem that provides Internet
access. What is the one additional component that
you should purchase to tie the network together?
– A. A router
– B. A network interface card
– C. A file server
– D. A HomePlug Ethernet port
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5 Wired Network Basics
 A wired network uses cables to connect network devices
 Wired networks are fast, secure, and simple to configure
 Devices tethered to cables
have limited mobility
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5 Ethernet
 Simultaneously broadcasts data packets to all network
devices
– IEEE 802.3
– CSMA/CD protocol
 Vary in speed from 10Mbps to 100Gbps
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5 Ethernet
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5 Ethernet Equipment
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5 Ethernet Equipment
 Ethernet adapter (designed to support the Ethernet
protocols)
 Network hub
 Network switch
 Network router
 RJ45 connector
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5 Ethernet Setup
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5 Ethernet Setup
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5 Ethernet Setup
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C
Wireless Networks
 Wireless Basics
 Bluetooth
 Wi-Fi
 Wi-Fi Equipment
 Wi-Fi Setup
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5 Question
 052300 When you’re setting up a wireless network, you see
an option asking if you want to broadcast the network SSID.
You should:
– A. Change the default SSID and broadcast it.
– B. Turn SSID broadcasting off so that hackers don’t
know the network’s encryption key.
– C. Make sure SSID is broadcasting so that your network
is protected by strong encryption.
– D. Activate SSID broadcasting or else the network
devices won’t be able to send data to the router.
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5 Wireless Basics
 A wireless network transports data from one device to
another without cables or wires
– RF signals
• Transceiver
– Microwaves
– Infrared light
 Slower than wired networks
 Security concerns
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5 Bluetooth
 Bluetooth is a short-range, wireless network technology
designed to make its own connections between electronic
devices, without wires, cables, or any direct action from a
user
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5 Wi-Fi
 Wireless networking technologies that are compatible with
Ethernet
 MIMO technology uses two or more antennas to send
multiple sets of signals between network devices
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5 Wi-Fi Equipment
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5 Wi-Fi Equipment
 If your computer is not pre-equipped with wireless circuitry,
you can purchase and install a Wi-Fi adapter
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5 Wi-Fi Equipment
 Wireless network setups
– Wireless ad-hoc network
– Wireless infrastructure network
• Wireless
access point
• Wireless
router
– MiFi
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5 Wi-Fi Setup
 Set up the router
 Connect to the router with a computer
 Configure the router
 Access the router setup utility
 Create a new router password
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5 Wi-Fi Setup
 Enter an SSID for the network
 Activate WEP, WPA, or PSK and create an encryption key
 Set up the wireless workstations
 Connect an Internet access device
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5 Wi-Fi Setup
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5
SECTION
D
Using LANs
 LAN Advantages and Challenges
 Sharing Files
 Sharing Printers
 Network Troubleshooting
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5 Question
052400 There are many ways to share files among
the computers on a network. Which one of the
following is the LEAST secure way to share files?
– A. Use a file server.
– B. Activate file sharing for the root directory of all
the computers in the network.
– C. Designate specific folders on your computer
as shared.
– D. Put files you want to share in the Public
folder.
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5 LAN Advantages
and Challenges
 LANs enable people to work together
 Sharing networked software can reduce costs
 Sharing data on a LAN can increase productivity
 Sharing networked hardware can reduce costs
 Sharing networked hardware can provide access to a wide
range of services and specialized peripheral devices
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5 LAN Advantages
and Challenges
 Resources become unavailable when network malfunctions
 Networks may be vulnerable to unauthorized access
– More vulnerable than standalone computers
 Wireless networks can be tapped from any computers within
range of the wireless signal
 Networked computers are susceptible to an increasing
number of worms, Trojan horses, and blended threats
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5 Sharing Files
 If you use Windows, it
automatically detects
available LANs any time
you turn on a workstation
 To connect to a shared
resource, you might be
asked for a user ID and
password
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5 Sharing Files
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5 Sharing Files
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5 Sharing Files
 A homegroup is a collection of trusted networked computers
that automatically share files and folders
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5 Sharing Printers
 Three setups allow for printer sharing:
– Set up printer sharing using a workstation printer
– Set up printer sharing using a print server
– Install printer with built-in networking
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5 Sharing Printers
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5 Troubleshooting
 Network problems can stem from a variety of sources
– Cables
– Signal strength
– Security
– Interference
– Network devices
– Settings
– Switches
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SECTION
E
Security Through Encryption
 Wi-Fi Security
 Encryption
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5 Question
052500 As part of the process of setting up a wired
network, what should you remember to do?
– A. Assign an IP address to each network device.
– B. Remove the Ethernet card from any computer
that has one.
– C. Enable wireless security.
– D. Disable the SSID.
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5 Wi-Fi Security
 Wireless networks are much more susceptible to
unauthorized access and use than wired networks
 LAN jacking, or war driving, is the practice of intercepting
wireless signals by cruising through an area
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5 Wi-Fi Security
 Wireless encryption scrambles data transmitted between
wireless devices and then unscrambles the data only on
devices that have a valid encryption key
– WEP (Wired Equivalent Privacy)
– WPA (Wi-Fi Protected Access)
– WPA2
– PSK
 Activate encryption by using a wireless network key
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5 Wi-Fi Security
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5 Encryption
 Encryption transforms a message so that its contents are
hidden from unauthorized readers
– Plaintext has not yet been encrypted
– An encrypted message is referred to as ciphertext
 Decryption is the opposite of encryption
– Cryptographic algorithm
– Cryptographic key
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5 Encryption
 Weak vs. strong encryption
 AES (Advanced Encryption Standard)
 Encryption methods can be broken by the use of expensive,
specialized, code-breaking computers
– Brute force attack
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5 Encryption
 Public key encryption (PKE) eliminates key-distribution
problem, by using one key to encrypt a message and
another key to decrypt the message
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5 Encryption
 When personal computer users want to encrypt e-mail or
other documents, they turn to public key encryption software
called PGP (Pretty Good Privacy)
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5 What Do You Think?
 053100 Have you ever accessed a free WLAN?
– A. Yes
B. No
C. Not sure
 053200 Do you believe that rogue WLANs can survive
alongside for-profit broadband ISPs?
– A. Yes
B. No
C. Not sure
 053300 Are broadband providers justified in limiting the
terms of their service agreements to “one subscription, one
customer”?
– A. Yes
B. No
C. Not sure
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Chapter 5 Complete
Computer Concepts 2012