4. Wireless Computer Networking
• Wireless technologies use electromagnetic
waves to carry information between devices.
• An electromagnetic wave is the same
medium that carries radio signals through
products conform to
the 802.11 "Wi-Fi"
5. Advantages of WiFi
• Mobility – allows for easy connection of both
stationary and mobile clients
• Scalability – allow more users (coverage area)
• Flexibility – provide anytime connectivity
• Cost Saving – equipment costs
• Reduce Installation Time – easy to install
6. Disadvantages of WiFi
• Interference - due to weather, other wireless
devices, or obstructions like walls.
• Speed - Wireless connections are slower.
• Price - Wireless hardware is more expensive.
• Technology – WLAN technology continues to
involve. The speed and technology (not fix as
7. Wireless Technologies
• Infrared (IR)
– Infrared (IR) is relatively low energy and cannot
penetrate through walls or other obstacles.
– Used to connect and move data between devices
such as Personal Digital Assistants (PDAs) and
8. Wireless Technologies (cont…)
• Radio Frequency (RF)
– RF waves can penetrate through walls and other
obstacles, allowing a much greater range than IR.
Bluetooth is a technology that makes use of the 2.4
GHz band. It is limited to low-speed, short-range
communications, but has the advantage of
communicating with many devices at the same time.
IEEE 802.11 standards - transmit at a much higher
power level, which gives them a greater range.
11. Answer Me…. WPAN / WLAN /
1. Naim call his friend using his cell phone?
2. Upload files to Emma’s laptop from her PDA’s?
3. Checking email using laptop at a wireless
4. Bella uses a wireless Bluetooth to listen to music
from his mp3 player?
12. WLAN Standards
• IEEE 802.11 standard governs the WLAN
• There are four amendments to the IEEE
15. WLAN Components
• Wireless Client/STA (STAtion) – Any host
device that connect to a wireless network.
• Access Point – Control access between
wired and wireless network, acts as media
17. WLAN Components (cont…)
• Antenna – Used on APs and Wireless
bridges, increases the output signal strength
from a wireless device
18. Service Set Identifier (SSID)
• SSID is a code to set the wireless components
connect to the appropriate WLAN.
• SSID is a case-sensitive, alpha-numeric string that
is up to 32-characters.
All wireless devices in
a WLAN must be
configured with the
same SSID in order to
SSID is the public
name of a wireless
19. Basic form of WLAN installations
• There are two basic forms of WLAN
20. Ad-Hoc / IBSS
• Covered area known as Independent Basic
Service Set (IBSS)
• Simplest form of a wireless network is
created by connecting two or more wireless
clients together in a peer-to-peer network.
• Does not include an Access Point.
• All clients within an ad-hoc network are
21. Infrastructure Mode / BSS
• Covered area known as Basic Service Set
• Require a single device that controls
communications in the wireless cell.
• Individual STAs can not communicate
directly with each other.
• To communicate, each device must obtain
permission from the AP.
22. Extended Service Set (ESS)
• (BSS) area of coverage of a single AP is limited.
• To expand the coverage area, connect multiple BSSs
through a Distribution System (DS). ESS uses multiple
APs. Each AP is in a separate BSS. BSSs must overlap by
23. Wireless Channel
• Wireless clients are communicating within an
IBSS, BSS or ESS.
• Channels are created by dividing up the
available RF spectrum.
• Each channel is capable of carrying a
24. Wireless Channel (cont…)
• Carrier Sense Multiple Access with Collision
– CSMA/CA creates a reservation on the channel
for use by a specific conversation.
from H1 to
Steps to sending message/data thru channel
• H1 must ask permission from the AP. Known as a
Request to Send (RTS)
• AP replied known as Clear to Send (CTS). If no one
use the channel.
• H1 sending Data to H2.
• When conversation is complete, H1 requested the
channel sends another message to the AP. Known
as Acknowledgement (ACK). ACK is to release the
channel, so someone else can use the channel.
27. WLAN Attacks
WLAN attacks avoid by:
1. Limited access to a WLAN – filter MAC
2. Authentication on a WLAN – username
3. Encryption on a WLAN – data transfer
4. Traffic filtering on a WLAN – filter MAC
address, IP address, application etc.
28. Limited Access to WLAN
• One way to limit access to your wireless network is
to filtering the MAC Address.
29. Authentication to WLAN
• Authentication is the process of permitting entry to a
network based on a set of credentials.
• There are three types of wireless authentication
– Open authentication
– Pre-Shared Key (PSK)
– Extensible Authentication Protocol (EAP)
30. Authentication to WLAN (cont…)
Open authentication should only be used on
public wireless networks
31. Authentication to WLAN (cont…)
Pre-Shared Key (PSK)
PSK both the AP and client must be configured
with the same key or secret word.
32. Authentication to WLAN (cont…)
Extensible Authentication Protocol (EAP)
EAP provides two-way, authentication as well as
EAP software is installed on the client, the client communicates with a backend authentication server:
Remote Authentication Dial-in User Service (RADIUS)
33. Encryption on a WLAN
• Authentication and MAC filtering ONLY stop an
attacker from connecting to a wireless network.
• Encryption is the process of transforming data so
that even if it is intercepted it is unusable.
34. Encryption on a WLAN (cont…)
• Types of Encryption:
1. Wired Equivalency Protocol (WEP)
2. Wi-Fi Protected Access (WPA)
** WPA also have another version called WPA2
35. Wired Equivalency Protocol (WEP)
• Wired Equivalency Protocol (WEP) is an advanced
security feature that encrypts network traffic through
• WEP uses pre-configured keys to encrypt and
decrypt data. A WEP key is entered as a string of
numbers and letters and is generally 64 bits or 128
• Every wireless device must have the same WEP key
entered. Without this key, devices will not be able to
understand the wireless transmissions.
37. Wi-Fi Protected Access (WPA)
• WPA uses encryption keys from 64 bits up to
• Generates new, dynamic keys each time a
client establishes a connection with the AP.
• More secure than WEP because it is
significantly more difficult to crack
38. Traffic Filtering on a WLAN
• Traffic filtering is control the types of traffic
transmitted across a WLAN.
• Traffic filtering blocks undesirable traffic from
entering or leaving the wireless network.
• Filtering is done by the AP as traffic passes. We can
remove the traffic by filter a specific MAC or IP
• It can also block certain applications by port