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Copyright © www.networkel.com
4- Wireless LAN
4.1 Wireless LAN Overview
4.2 Wireless LAN Operations
4.3 Wireless LAN Security
4.4 Wireless LAN Configuration
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4.1 Wireless LAN Overview
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WHY WE NEED WIRELESS NETWORK ?
• Today, mobility is very important
• People want to connect to a LAN or
internet from almost everywhere
( Home, cafe, stadium etc. )
• Solution : Wireless Network
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ADVANTAGES OF WIRELESS
• Cost reduction (no cabling
requirement)
• Flexibility (location independent)
• Productivity
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WIRELESS TECHNOLOGIES
• WI-FI : Network connection up to
7 Gbps (IEEE 802.11 Standards)
• Blueetooth : Up to 14 Mbps
transmission (IEEE 802.15)
• Wi-MAX : Up to 50 km wireless
broadband connection (Up to
1gbps)
• Cellular Broadband : 3G, 4G
• Satellite Broadband : Broadband
from directional satellite dish
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IEEE 802.11 WI-FI STANDARDS
• Set of media access control (MAC) and physical layer (PHY)
specifications for implementing wireless local area network
(WLAN) communication.
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WIRELESS LAN vs WIRED LAN
Characteristic 802.11 WLAN Ethernet LAN
Physical Layer Radio Frequency (Very Low) Cable
Media Access Collision Avoidance Collision Detection
Availability Everybody in the range of AP Cable connection required
Signal Interference Yes Inconsequential
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WIRELESS NETWORK INTERFACE CARDS
• Provides wireless connection to
Access to wireless networks
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WIRELESS MODEM
• Provides wireless broadband
connection for home users over
WI-FI
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BUSINESS WIRELESS SOLUTIONS
• Provides wireless LAN connection
for corporate users
• Autonomous AP : Access points
are configured individually
• Controller-Based AP : Access
points are managed by a
controller. Controller can provide
a single configuration for multiple
APs
R1
SW1
PC2PC1
AUTONOMOUS OR
CONTROLLER-BASED AP
PC3
Laptop - 1
Laptop - 2
Laptop - 3
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WIRELESS ANTENNAS
• Omnidirectional : Radiation cone
is 360 degrees, working in all
directions
• Directional : Refers to signal
coverage in a specified direction
• Yagi : Used for moving Wi-Fi
signals to longer distances
(Directional)
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802.11 TOPOLOGY MODES
• Ad Hoc Mode : Direct wireless
connection without an AP
• Infrastructure Mode : Wireless
connection with an AP
Basic Service Area
Extended Service Area
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AD HOC MODE
Laptop - 1 Laptop - 2
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INFRASTRUCTURE MODE (BSA)
Laptop - 1
Laptop - 2
• Basic Service Area
• Number of APs : 1
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INFRASTRUCTURE MODE (ESA)
• Extended Service Area
• Number of APs : 2 or more
R1
SW2
PC2 PC3Laptop - 1
Laptop - 2
Laptop - 3
SW1
PC1
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4.2 Wireless LAN Operations
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802.11 FRAME
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CSMA / CA
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CLIENT – ACCESS POINT CONNECTION
DISCOVER AP ( Active – Client must know SSID or Passive – AP advertises SSID
AUTHENTICATE (Open authentication (no pw.) or Shared Keys
ASSOCIATE
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CONNECTION PARAMETERS
• SSID : Used as an identifier for a wireless
LAN, and is intended to be unique for a
particular area (Name of AP)
• Security Key : Used for client
authentication
• Security Mode : WEP / WPA / WPA2
• Network Mode : 802.11a/b/g/n/ac/ad
• Channel Settings : Frequency band
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FREQUENCY CHANNEL SATURATION
• Frequency channels are used for
communication between sender
and wireless receiver devices
• If channel is used so much by
clients, it can saturate
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FREQUENCY CHANNEL SATURATION (cont)
• To decrease the saturation ;
Direct-sequence spread spectrum (DSSS) : Spread
radio energy over a channel (802.11b)
Frequency-hopping spread spectrum (FHSS) : Use the
whole band in small intervals (802.11)
Orthogonal Frequency-Division Multiplexing
(OFDM) : Multiple transmissions simultaneously over
a single channel (802.11a/g/n/ac)
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4.3 Wireless LAN Security
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WIRELESS DOS ATTACKS
• DOS attacks are easily executed in a
wireless network.
• Emitting a very strong RF interference on
the channel in which the wireless
network is operating on will increase the
noise on that channel and thus causing
interference to all wireless networks that
are operating at / near that channel
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ROUGE ACCESS POINT
• Access point that has been installed on a
secure network without explicit
authorization to capture client data or
information such as MAC address
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MAN IN THE MIDDLE ATTACK
• Attacker secretly relays and
possibly alters the communication
between two parties who believe
they are directly communicating
with each other.
• An attacker within reception
range of an unencrypted Wi-Fi
wireless access point can insert
himself as a man-in-the-middle
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HOW TO SECURE YOUR WIRELESS NETWORK ?
• Use shared key authentication (WEP / WPA / WPA2) and
encryption to secure your wireless network
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4.4 Wireless LAN Configuration
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WIRELESS ROUTER CONFIGURATION
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WIRELESS ROUTER CONFIGURATION (cont.)
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WIRELESS ROUTER CONFIGURATION (cont.)
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WIRELESS ROUTER CONFIGURATION (cont.)
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