Wireless Technologies
Networking for Home and Small Businesses – Chapter 7
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Objectives

Describe wireless technologies.

Describe the various components and structure of a
WLAN

Describe wireless LAN security issues and mitigation
strategies

Configure an integrated wireless access point and a
wireless client .
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 All use waves in Electromagnetic spectrum to transfer
information from device to device.
 Electromagnetic spectrum includes bands used for radio, TV,
and visible light.
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How Big?
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Overview of Waves
Rick Graziani graziani@cabrillo.edu
 Wave is a “disturbance or variation” that travels through a medium.
 The medium through which the wave travels may experience some local
oscillations as the wave passes, but the particles in the medium do not
travel with the wave.
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Just like none of the individual people in the stadium are carried
around when they do the wave, they all remain at their seats.
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Waves
www.ewart.org.uk
 Waves are one way in which energy can move from one place to another.
 The waves that you see at the beach are the result of the kinetic energy of
water particles passing through the water.
 Other types of energy (such as light, heat, and radio waves) can travel in this
way as well.
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Waves
www.ewart.org.uk
 The distance between 2 peaks (or 2 troughs) is called a
wavelength
 The deepest part of a trough or the highest part of a peak is
called the amplitude
 The frequency is the number of wavelengths that pass by
in 1 second
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Longitudinal
Waves
www.ewart.org.uk
 Longitudinal sound waves in the air behave in much the same way.
 As the sound wave passes through, the particles in the air oscillate back and forth from
their equilibrium positions but it is the disturbance that travels, not the individual
particles in the medium.
 Rick talks in a loud voice.
 When he talks he causes the air near his mouth to compress.
 A compression wave then passes through the air to the ears of the people around him.
 A longitudinal sound wave has to travel through something - it cannot pass through a
vacuum because there aren't any particles to compress together.
 It has a wavelength; a frequency and an amplitude.
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Transverse Waves
 Transverse waves on a string are another example.
 The string is displaced up and down, as the wave travels from left to right, but the string
itself does not experience any net motion.
 A light wave is a transverse wave.
 If you look at the waves on the sea they seem to move in one direction .... towards you.
 However, the particles that make up the wave only move up and down.
 Look at the animation, on the right, although the wave seems to be moving from left to
right the blue particle is only moving up and down.
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Sine waves
 The sine wave is unique in that it represents energy entirely
concentrated at a single frequency.
 An ideal wireless signal has a sine waveform
 With a frequency usually measured in cycles per second or Hertz
(Hz).
 A million cycles per second is represented by megahertz (MHz).
 A billion cycles per second represented by gigahertz
(GHz).
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Sine waves
 Amplitude – The distance from zero to the maximum value of each alternation
is called the amplitude.
The amplitude of the positive alternation and the amplitude of the negative
alternation are the same.
 Period – The time it takes for a sine wave to complete one cycle is defined as
the period of the waveform.
The distance traveled by the sine wave during this period is referred to as its
wavelength.
 Wavelength – Indicated by the Greek lambda symbol λ.
It is the distance between one value to the same value on the next cycle.
 Frequency – The number of repetitions or cycles per unit time is the frequency,
typically expressed in cycles per second, or Hertz (Hz).
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Relationship between time and frequency
 The inverse relationship between time (t), the period in seconds, and frequency (f), in Hz, is indicated
by the following formulas:
t = 1/f (time = 1 / frequency)
f = 1/t (frequency = 1 / time)
Examples:
1 second
 t = 1/f 1 second = 1 / 1 Hz (1 cycle per second)
 f = 1/t
1 Hz = 1 / 1 second
½ second
 t = 1/f ½ second = 1 / 2 Hz (2 cycles per second)
 f = 1/t 2 Hz = 1 / ½ second
1/10,000,000th of a second
 t = 1/f 1/10,000,000th of a second = 1 / 10,000,000 Hz (cycles/sec) = 1 / 10 MHz
 f = 1/t 10 MHz = 1 / 1/10,000,000th of sec
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Sine waves
Amplitude,
Frequency, and
Phase
180° Phase Shift
 One full period or cycle of a sine wave is said to cover 360 degrees
(360°).
 It is possible for one sine wave to lead or lag another sine wave by any
number of degrees, except zero or 360.
 When two sine waves differ by exactly zero° or 360°, the two waves
are said to be in phase.
 Two sine waves that differ in phase by any other value are out of
Rick Graziani graziani@cabrillo.edu
phase, with respect to each other.
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Analog to digital conversion
1. Analog wave amplitudes are sampled at specific instances in time.
2. Each sample is assigned a discrete value.
3. Each discrete value is converted to a stream of bits.
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Bandwidth
 There are two common ways of looking at bandwidth:
Analog bandwidth
Digital bandwidth
 Analog bandwidth
Analog bandwidth can refer to the range of frequencies .
Analog bandwidth is described in units of frequency, or cycles per second,
which is measured in Hz.
There is a direct correlation between the analog bandwidth of any medium
and the data rate in bits per second that the medium can support.
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Bandwidth
 Digital bandwidth
Digital bandwidth is a measure of how much information can flow from
one place to another, in a given amount of time.
Digital bandwidth is measured in bits per second.
When dealing with data communications, the term bandwidth most
often signifies digital bandwidth.
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Unlicensed Radio bands in Hz
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Wireless Technologies
 Infrared Band (IR)
Low energy and unable to penetrate walls (line of sight)
Could this be a benefit?
Used for PDAs, PCs, wireless mice, keyboards and remote controls
IrDA (Infrared Direct Access) port used for 1 to 1 connections
 Radio Frequency (RF)
Goes through walls and other obstructions, better range
Different frequencies assigned to different types of unlicensed devices (900MHz,
2.4GHz, 5GHz)
Cordless Phones
Problem with 900MHz?
Used for military and civilian emergency bands outside US
Wireless LANs
Computer Peripherals
Bluetooth uses 2.4 GHz band for low-speed, short-range, many devices at
once
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Wireless Technologies
Pros
 Provide anytime,
anywhere connectivity
 Hotspots implemented
globally
 Easy and inexpensive to
install
Cons
 Unlicensed regions of the
RF spectrum – congestion
and interference common
 Security. Wireless
provides ease of access –
through broadcasts
 Enables networks to be
easily expanded, i.e., ease
of adding additional
devices
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Interference
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Wireless Technologies
 Pros
 Cons
Anytime, anywhere connectivity
with hotspots
Unlicensed RF which is
crowded with other devices
Easy and cheap installation
Bluetooth
Device prices dropping
Microwaves
Data rate capabilities increasing
Cordless phones
Easy expansion
Security is difficult because
there is no way to limit who can
intercept the wireless signal
Encryption helps, but can
be defeated
Fluctuations in temperature and
humidity can really affect
transmission range.
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Station Connectivity
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 Wireless networks are difficult to categorize because boundaries cannot be
precisely defined.
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Wireless Network Technologies
 Technologies used for the different network types:
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 Many different standards have been adopted for wireless
networks
Wi-Fi Alliance tests devices from various manufacturers to make sure they
operate together. The device is interoperable with other devices of the
same standard.
Protocol Release
Date
RF
Freq.
Through
put
Data
Rate
(Max)
Max
Range
Notes & Comments
802.11
1997
2.4 GHz 0.9 Mbps 2 Mbps
Undefined Legacy
802.11a
1999
5 GHz
50m
Not compatible with b, g, n
Expensive
802.11b
1999
2.4 GHz 4.3 Mbps 11 Mbps
100m
First 2.4 GHz Technology
802.11g
2003
2.4 GHz 19 Mbps 54 Mbps
100m
Backward compatible with b
Shares range with b
802.11n
2009*
2.4 & 5
GHz
802.11y
2008*
3.7 GHz 23 Mbps 54 Mbps
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23 Mbps 54 Mbps
74 Mbps 248 Mbps 250m
5000m
Newest Standard
Newest Standard
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Wireless Technologies
 Wireless networks and their boundaries
They are unlike Bluetooth technology in that they transmit at a
much higher power level, which gives them a greater range.
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Components and Structure of a WLAN
 Identify and describe wireless LAN standards
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 Wireless Components
Wireless Clients or
STAs (Wireless
STAtion)
APs (Access Points)
Wireless Bridges
 Types of Antennas
Omni send all directions
Used in APs
Directional send in one
direction
Used for longer links
to bridge distances
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 The Service Set Identifier
(SSID) used by components to
connect to a particular WLAN.
32-byte Alphanumeric String
Used in Frame Headers
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 Two forms of WLAN Installations
Ad-hoc - IBSS
Equal Peer-to-peer
No AP
Infrastructure - BSS
STAs communicate through APs
BSS is an area with a single AP
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Components and Structure of a WLAN
 Describe how wireless channels are used
 CSMA/CA: Describe how wireless channels avoid collisions
7.2.4.3
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Wireless Channels
 Channels are created by giving each a part of the RF spectrum
Each one can carry on a separate conversation (Think of a TV)
Can be set manually or automatically
 Channels will often overlap frequencies, but conversations cannot
overlap
 Newer technologies combine channels into a wider one for better
bandwidth
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802.11b/g channel use
•HR/DSSS uses 22 MHz channels in the 2.4 to 2.483 GHz range.
•This allows for three non-overlapping channels (three channels that
can coexist or overlap without causing interference), channels 1, 6 and
11
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802.11 a channel use
www.networkcomputing.com/1201/1201ws1.html
 Offers 8 lower and mid-band non-interfering channels
As opposed to 3 with 802.11b/g
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 A WLAN technology designed to make
collisions impossible
 Carrier Sense Multiple Access with Collision
Avoidance (CSMA/CA).
Reserves a channel for use by a conversation
No other devices can transmit on that channel
 CSMA/CA Reservation Process
For a Device to use a channel, it asks the AP by
using a Request To Send (RTS) message.
If channel is not in use, AP will send Clear To
Send (CTS) message to all devices in the BSS
so they know the channel is being used.
Data is sent from STA
After conversation is done, an
Acknowledgement (ACK) is transmitted.
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 Integrated wireless access
point
Network Mode
802.11b, g, or a different
technology
SSID
Name of your wireless network
Standard Channel
Default is AUTO, but this
decides which channel will be
used
SSID Broadcast
Sends out the SSID to the
world
Default is ENABLE
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The router supports 802.11b,
802.11g, and 802.11n devices
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Components and Structure of a WLAN
 Configure an integrated wireless access point
7.2.5.3
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 Client software allows hardware to
connect to the WLAN.
Wireless Client Configuration
 For connection to occur, the SSID,
security settings, and channel must
match the AP.
 Wireless Utility Software usually comes
with the NIC
 Some features
Link Information: strength and quality of
signal
Profiles: specify configuration options
Site Survey: checks for all WLANs in the
area
To use the vendor software, Windows XP
wireless software must be disabled.
 For most purposes, XPs built-in
wireless drivers can be used.
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Components and Structure of a WLAN
 Configure a wireless client
7.2.6.4
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 One large benefit to Wireless networks is also biggest vulnerability:
transmission of information through the air.
 Attacks don’t need physical access to equipment, just be in range.
War Driving or Walking to discover insecure networks
 If they gain access, an attacker can:
Use your Internet for free
Hack your computers or files
 Special security protocols have been developed to protect
networks, but there are simple steps as well.
Disable the SSID broadcast so that your network isn’t public.
Change your default settings
IP Address
Router Name
Admin Password
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 Controls exactly which
devices have access to
the LAN
 Uses MAC addresses to
ID clients authorized to
access WLAN.
 Limitations:
MAC addresses for
authorized clients must be
input manually.
This makes adding new
clients difficult
MAC Address cloning or
spoofing can allow an
unauthorized user to get into
the WLAN.
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 This process requires a client to
present credentials in order to use the
network.
 Most common is a username and
password, but for a wireless network,
this is handled differently.
 Because the transaction is wireless
and can be “heard” by anyone, the
authentication is done before
connecting.
7.3.4.3
 Three Types of Authentication:
Open
Used for Public Networks
Networks where another method of
authentication is used.
PSK
EAP
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Wireless LAN Security - Authentication
 PSK (Pre-Shared Key)
Both client and AP are configured with a shared key
Password is encrypted by client using shared key, then sent to
AP, where it is decrypted using the same key.
Doesn’t authenticate AP or User, only one way
 EAP (Extensible Authentication Protocol)
Authentication is 2-way
Client communicates through AP to (usually) a RADIUS server
which has list of authorized users and clients.
Both user and client must authenticate.
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 Use of Wireless Authentication
Authentication can prevent unauthorized users from accessing WLAN,
but data is still transmitted to anyone with a receiver.
Encryptions methods were developed to encrypt wireless
communications to prevent snooping by outsiders.
 Two main encryption methods:
WEP (Wired Equivalency Protocol)
Uses pre-configured 32, 64, 128, or 256 bit keys to encrypt data
before transmission.
WEP keys are just a string of letters or numbers and can also be
automatically generated using a passphrase.
WEP is not a secure protocol and can easily be cracked by a
knowledgeable wireless hacker.
WPA (Wi-FI Protected Access)
Also uses a 64 to 256 encryption key.
WPA doesn’t always use the same key, but generates new,
dynamic keys each time a client connects.
WPA is considered the current standard of encryption for wireless
networks.
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Wireless LAN Security Issues and Mitigation
Strategies
 Describe traffic filtering and its purpose
7.3.5.2
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Planning the WLAN
 Plan for a wireless LAN implementation
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 Security should be
planned and configured
before installing into
network or ISP
 Basic measures:
Change Defaults for SSID,
usernames, and PWs
Disable SSID broadcast
MAC Address Filtering
 Advanced Measures
WPA or WEP Encryption
Authentication
Traffic Filtering
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Configure an Integrated Wireless Access Point
and Wireless Client
 Describe options for backing-up and restoring AP
configurations
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 Configuration files for APs are stored in
their non-volatile memory
 Any stored memory can be corrupted,
so it’s important to backup the
configuration in case of problems.
 Backup
Save the configuration file to a secure
location
 Restore
Use the restore button to upload the file
to the AP
 Setting to Factory Default
Menu option
Hold RESET button for up to 30 seconds.
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 Firmware is a basic OS for the AP or Router stored in flash
memory
 Can be updated using the GUI on the AP/Router
Download from manufacturer’s website
Make sure to check version currently being used
 NEVER interrupt an update while it is being uploaded, it may
make the AP/Router unusable.
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Configure an Integrated Wireless Access Point
and Wireless Client
 Identify current version of firmware and describe how to
update firmware
7.4.4.1
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Challenge Lab 7-4: Planning the Home or
Small Business WLAN
 Objectives
Evaluate user needs
Use a WLAN implementation checklist
Conduct a mini-site survey
Plan WLAN implementation
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Summary
 Wireless technologies use electromagnetic radiation in
the form of radio signals to carry information between
devices.
 Ease and convenience of connecting devices wirelessly
creates security concerns that need to be addressed.
 Before installing wireless devices, an installation plan
should be created which includes strategies for layout
and security.
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