Transcript Chapter 7 2007

7: Wireless Technologies
Networking for Home & Small Business
Objectives
Understanding Wireless
• Electromagnetic Spectrum
– Radio, TV, Light, X-Rays, Gamma Rays
– Each has a specific wavelength
• Like the distance between waves
• Wireless uses Electromagnetic Waves
– Same as carrying radio signals
• We’ll discuss the most common
wavelengths
Infrared (IR)
• Low energy
• Can’t go through walls, short range (30’)
• One to one communication
– Wireless Mice & Keyboards, Remotes, PDA
– Infrared Direct Access (IrDA) port
IR & Your TV
• Your TV remote has an infrared LED inside
• Switches on & off to create 0’s and 1’s when you
push a button
– Push a button to send a 7 digit sequence of 0’s & 1’s
– Sony TV Channel Up is 0000011, channel down is
0010001
Radio Frequency (RF)
• Wireless LAN, cordless phone, Bluetooth
• LAN & Phone
– Signal travels through walls, longer range, higher power
– 900 MHz, 2.4 GHz and the 5 GHz frequency
• Bluetooth
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Low speed, short range, lower power
One to many devices
Uses 2.4GHz
Starting to use Bluetooth for wireless mice, etc.
Activity- Which is it?
Review
• Bluetooth or RF. Which has higher power
output?
– RF
• Two doctors are beaming their business
cards to each other through their PDAs.
Which signal is being used?
– IR
Wireless Benefits
Wireless Limitations
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Cordless Phones 2.4GHz Interference
Microwave Ovens Interference
Not as fast as wired
Security
– Ease of Access
• Size of Building
– Range
• Solid Walls
WPAN
• Wireless Personal Area Network
– Used to connect wireless mice, keyboards &
PDA’s to computer
– IR or Bluetooth
– Short Range
– Device to device
WLAN
• Wireless Local Area Network
– RF
– IEEE 802.11 standards
– Users connect to a wired network through an
Access Point (AP)
– Medium range
Access Point
• Between your wired equipment and your
wireless devices
WWAN
• Wireless Wide Area Network
– Cell phone network
– GSM, CDMA
– Long range
– Government regulated
Review
Wireless Standards
• Specifies data speed, range, RF spectrum
• IEEE standards, Wi-Fi
• 802.11a, 802.11b, 802.11g and 802.11n
• Wi-Fi Alliance tests devices from
manufacturer
• Will work with other devices w/ same logo
802.11b
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1999
2.4GHz
11Mbps
150ft range
indoors
• 300 ft range
outdoors
802.11a
• 1999
• 5GHz
– Unused at that time
– Less congestion
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54Mbps (faster than B)
NOT compatible with b/g/n
75ft-150ft range
Originally too expensive
Now hard to find
802.11g
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2003
2.4GHz
54Mbps
150ft range indoors
300 ft range outdoors
Compatible with 802.11b
802.11n
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In development
2.4Ghz
Up to 750ft range
Backwards compatible b/g
Wireless Components
• Access Point
– Connects wireless devices to wired network
• Client
– Any host device that connects to wireless
– Also known as STA (station)
• Bridge
• Antenna
Omni-Directional Antenna
• Equally in all directions
• Found on APs
Directional Antenna
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Concentrate signal in one direction
Better distance
Connects networks 25 miles or more apart
Bridge to Bridge- connects 2 networks
wirelessly
Want a bridge? Aironet 1400
• Find it on www.cdwg.com
Activity
7.2.3
• WLANs & the SSID
• 2 Forms of WLAN installations
SSID-Service Set Identifier
• Tells wireless devices which WLAN they belong
to & which other devices they can communicate
with
• Case-sensitive & up to 32 characters
• All of your devices MUST have same SSID
– Broadcast or Not?
Ad-hoc Mode- IBSS
• Wireless devices can talk to each other
without involving Access Point
• Peer-to-peer or small networks
• Less $$$, no AP
Infrastructure Mode- BSS
• Most used
• AP/Router controls communication
– Access to Internet
– Basic Service Set (BSS)
• Area covered by a single AP
Cover More Areas
• Connect many BSS’s to get expanded area
– You get an ESS, Extended Service Set
• Areas should overlap
– Think about this school & coverage
Question?
Question?
Question?
Question?
Lab Activity
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7.2.3.4
READ THE INSTRUCTIONS!!!
Click Topology, then the host
View browser, follow directions
Wireless Channels
• Used to control multiple conversations
– Like how all of your TV channels travel across a cable
– Divides up the 2.4GHz for each conversation
• Selection of channels is usually automatic
• Sometimes they use a single wide channel to get
more bandwidth
Going to a Concert
• General Admission compared to tickets for
a seat
– What’s the different experiences?
• Wireless has a method to avoid collisions
• A “ticketing” system
Wireless Detecting Collisions
• CSMA/CA
• Reserves a channel for conversation
– No one else may use that channel
• Request to Send (RTS) to the AP
• If available, a Clear to Send (CTS) is sent
– OK to send
– Broadcast is sent to all, notifying channel in
use
• ACK sent to AP to notify done
– All devices see ACK & know channel is open
CSMA/CA- (7.2.4.2)
Activity- Setting the Channel
• 7.2.4.3
Configuring an AP
Configuring the Client
• What is a wireless host known as?
– STA (station)
• It’s a device with wireless NIC & software
for it
• Settings MUST match AP
– SSID, security settings, and channel
Configuring the Client- Software
• As part of the OS
• OR supplied with Wireless NIC
– Contains link info, profiles, etc.
• Usually the OS one is okay
Now Test It…
• Look at signal strength
• Then test data transmission
– Use the ping test
– Ping another PC 1st
– If that doesn’t work, ping the AP
Lab 7.2.5.3 & 7.2.6.4
• Configure the AP and Wireless Client
Wireless Security
• Tradeoff:
– Ease & convenience of availability vs. putting
info to the airwaves
• What can they do?
– Use your Internet for FREE
– Access your computers
– Damage files
– Steal private info
• Solution…SET UP SECURITY!
Why is security important?
• It’s possible that an individual or a business
owner can be held responsible for what an
unauthorized user does with your network
• Computer Fraud Law
– Accessing a computer without authorization
Which Security Measures??
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Use all of the following to secure your
wireless network:
1.
2.
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4.
5.
Change the router password from the default
Change the SSID & disable the broadcast
Use MAC Address Filtering
Authentication (PSK)
Encryption (WPA)
Change the Password!
Change & Disable SSID
• SSID
– Must be known to connect
– Broadcast by default
• Solutions
– TURN SSID BROADCAST OFF!!
– Change the default settings
• SSID
• Passwords
• IP addresses
– These solutions help, but you can still be
hacked!
The SSID’s- Discovered!!!
Get your MAC Addresses
Set up MAC Address Filtering
MAC Address Filtering
• Use your device’s MAC address to limit
connectivity to you KNOWN devices
• You pre-configure the MACs in the AP
• The AP will check its list
• Only those in list will connect
MAC Address Filtering
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What could go wrong?
– Typo on the MAC address
– New devices can’t enter network without
adding Mac to the AP configuration
– MAC address cloning
1. Sniff network traffic (MAC address in packet)
2. Find MAC addresses on that network
3. Change your MAC address to match one on the
target network.
Sniffing to Clone
Authentication
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Permitting entry on WLAN based on credentials
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Used before connecting to the WLAN
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Checks authentication 1st
Then MAC address filtering
1. Open authentication (DEFAULT SETTING)
2. PSK (good)….THIS IS USED AT HOME.
3. EAP (better than PSK)…BUSINESSES.
Open Authentication
• Public networks
Pre-Shared Keys (PSK)
• Client & AP have secret word/keys
• One-way
– Client authenticates to the AP
– AP DOES NOT authenticate the user
Extensible Authentication
Protocol- EAP
• Two-way PLUS user authentication
• Uses a separate server (RADIUS)
– Built into some AP’s now
– More for medium to large businesses
• The user provides a username & password
Overview
Configuring Auth & Encrypt
• WEP
• WPA Personal, uses PSK
– TKIP (Temporal Key Integrity Protocol)
– AES (Advanced Encryption System)
• WPA2
– TKIP or AES
• WPA Enterprise, RADIUS
• RADIUS
• AES is only supported by newer devices that
contain a co-processor.
– To ensure compatibility with all devices, select TKIP.
Problems Still???
• Authentication & MAC filtering won’t stop the
hacker
– They can sniff the info from the air
• Encrypt the data
– WEP
– WPA
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WEP- Wired Equivalency
Protocol
String of letters & numbers
64 or 128 bits
Passphrase
All devices in WLAN must have same WEP
key
Can work in conjunction with PSK
– WEP-PSK
• WEAK!!!!!
– Static key
WPA- Wi-Fi Protected Access
• Better than WEP
• 64-256 bits
• New keys for each time it connects
Review
• WEP/WPA _______________ the data.
– Encrypt
• PSK/EAP are used to _____________ the
user to the WLAN.
– Authenticate
• WEP or WPA. Which is stronger?
– WPA
• What’s the difference between open
authentication & PSK?
– PSK has the secret key
Activity
• 7.3.4
• Configure
authentication
Traffic Filtering
• You can control the type of data
– Entering or leaving the AP
– Going to/from a specific MAC or IP
– Block by port #
Lab
• 7.3.5.2
• Configuring Wireless Security
Planning the WLAN
• Determining the type of wireless standard
to use
• Determining the most efficient layout of
devices
• An installation and security plan
• A strategy for backing up and updating the
firmware of the wireless devices.
Wireless Standard
• Bandwidth requirements, coverage areas,
existing implementations, and cost.
– This information is gathered by determining end-user
requirements.
• Ask the following…
– What throughput is actually required by the
applications running on the network?
– How many users will access the WLAN?
– What is the necessary coverage area?
– What is the existing network structure?
– What is the budget?
Planning the WLAN
• Which 802.11 standards support a larger
BSS?
– Means less equipment to buy
• Is there an existing standard in use?
• Total Cost of Ownership (TCO) which
includes the purchase of the equipment as
well as installation and support costs
Installation of Devices
• Site Survey
– Measurements
– Consider interference sources & locations
Install & Secure the AP
Back It Up!!! 7.4.3.2 Activity
• Home & Small Business
– Select Backup Configuration in Menu
– To restore, select it
– Factory Default Setting
Updating the Firmware
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The OS of the device is in firmware
– Update for new features, etc
1. Get the current version
2. Research issues & features that may
cause you to want the upgrade
3. Download it to a HD (directly connected
machine)
4. Select Firmware upgrade
• DO NOT INTERRUPT THE PROCESS!
7.4.4.2 Activity
• Upgrade the firmware
Review
7: Wireless Technologies
Networking for Home & Small Business