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Wireless Technologies. Networking for Home and Small Businesses – Chapter 7 Spring 2009 - Mr. Specter. Objectives:. Describe wireless technologies. Describe the various components and structure of a WLAN Describe wireless LAN security issues and mitigation strategies

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wireless technologies

Wireless Technologies

Networking for Home and Small Businesses – Chapter 7

Spring 2009 - Mr. Specter

  • 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 .
electromagnetic frequencies
Electromagnetic Frequencies
  • All use waves in the Electromagnetic spectrum to transfer information from device to device.
  • Electromagnetic spectrum includes bands used for radio, TV, and visible light.
wireless technologies1
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
wireless technologies2

Anytime, anywhere connectivity with hotspots

Easy and cheap installation

Device prices dropping

Data rate capabilities increasing

Easy expansion


Unlicensed RF which is crowded with other devices



Cordless phones

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.

Wireless Technologies
wireless network categories
Wireless Network Categories
  • Wireless networks are difficult to categorize because boundaries cannot be precisely defined.
wireless network technologies
Wireless Network Technologies
  • Technologies used for the different network types:
wlan standards
WLAN Standards
  • Many different standards have been adopted for wireless networks
    • IEEE 802.11n is latest standard adopted (except for 802.11y)
    • Wi-Fi Alliance tests devices from various manufacturers to make sure they operate together.
structure of a wlan
Structure of a WLAN
  • 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
wlan types
The Service Set Identifier (SSID) used by components to connect to a particular WLAN.

32-byte Alphanumeric String

Used in Frame Headers

Two forms of WLAN Installations

Ad-hoc - IBSS

Equal Peer-to-peer


Infrastructure - BSS

STAs communicate through APs

BSS is an area with a single AP

WLAN Types
wireless channels
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
csma ca
  • 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.
wireless access point configuration
Wireless Access Point Configuration
  • 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
wireless client configuration
Client software allows hardware to connect to the WLAN.

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.

Wireless Client Configuration
wireless lan security issues mitigation strategies
Wireless LAN Security Issues & Mitigation Strategies
  • 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
wireless lan security mac address filtering
Controls exactly which devices have access to the LAN

Uses MAC addresses to ID clients authorized to access WLAN.


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.

Wireless LAN Security - MAC Address Filtering
wireless lan security authentication
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.

Three Types of Authentication:


Used for Public Networks

Networks where another method of authentication is used.



Wireless LAN Security - Authentication
wireless lan security authentication1
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.
wireless lan security data encryption
Wireless LAN Security – Data Encryption
  • 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 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.
wireless lan security traffic filtering
Wireless LAN Security – Traffic Filtering
  • Allows control of traffic types sent across WLAN
  • Blocks undesirable traffic from entering or leaving network
  • Filtered using
    • MAC Addresses
    • IP Addresses
    • Port Numbers
planning the wlan
Planning a WLAN is important so that the administrator can determine

Wireless standard

Most Efficient Layout

Installation and Security

Backups for Devices

Standard Used is Affected by:

Number of users

Size of Area Covered

Current Network


Number of users

WLAN Bandwidth is shared between all users, so number of clients and APs matters.

Size of Area Covered

Different technology has different areas of coverage:

E.g. 2.4 GHz band used in 802.11 b/g/n has a great radius than the 5Ghz used in the 802.11a tech.

Larger BSS


Cost is always a factor

TCO (Total Cost of Ownership) must be considered for any installation

Size needed, existing equipment, interference of signal, etc. must all be considered during planning phase.

Planning the WLAN
wlan security measures
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


Traffic Filtering

WLAN Security Measures
backup and restoring ap configurations
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.


Save the configuration file to a secure location


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.

Backup and Restoring AP Configurations
updating firmware
Updating Firmware
  • 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.
  • 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.