Wireless Networking

1
Wireless Networking

• Chapter 9

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Contents

• Explain wireless networking hardware and software
  requirements and configure wireless networking
  hardware
• Define wireless networking IEEE standards and FCC
  operation frequencies
• Define wireless network operation modes, limits,
  and methods
• Configure wireless networking security
• Describe troubleshooting techniques for wireless
  networks

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Introduction
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Wireless Networking

• Wireless networking uses radio waves instead of
  wires to connect devices
• Wireless networking is dominated by two
  technologies
• IEEE 802.11 wireless Ethernet standard
• Wireless Fidelity (Wi-Fi)
• Home Radio Frequency (HomeRF)
• Bluetooth

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Wireless Networking Basics
6
Hardware

• Wireless Ethernet NICs and Bluetooth adapters
  serve the same purpose as hardware in wired
  networks
• Many wireless PCI NICs are simply wireless PC
  Card NICs housed on a PCI card

7
USB Wireless NICs

• Have the benefit of being placeable able to
  move them around to get the best signal
• Like moving the rabbit ears on an old TV set

8
Adapters

• Used by not just PCs but also printers, handheld
  computers, and PDAs

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Access Points

• If youre connecting a small group of PCs
  together in a decentralized workgroup, then the
  wireless NICs are all you need
• If you wish to expand your network or to connect
  it to a wired network, youll need a wireless
  access point

10
Wireless Bridges

• Wireless bridges connect two different wireless
  segments or a wireless segment to a wired network
• Point-to-Point bridges can only communicate with
  a single other bridge
• Point-to-Multipoint bridges can talk to more than
  one bridge at a time

11
Bluetooth Hardware

• Wireless Bluetooth hardware is included as
  built-in equipment in many PCs, laptops, PDAs,
  and cell phones
• Most Bluetooth add-on devices are USB

External USB Bluetooth adapter
12
Software

• Wireless adapters come with a driver and a
  configuration utility
• Windows XP comes with drivers and configuration
  utilities for wireless
• The utility that came with the card is better to
  use
• Browser-based utilities are common

13
Ad-hoc Mode

• Ad-hoc mode
• Also called peer-to-peer mode
• Each node directly contacts other nodes
• Used for small networks
• Two or more wireless nodes talking in ad-hoc mode
  form an Independent Basic Service Set (IBSS)

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Infrastructure Mode

• Infrastructure mode
• Use one or more wireless access points to connect
  the nodes centrally
• Provides centralized control
• Used for larger networks
• A single wireless access point servicing a
  give area is called a Basic Service
  Set (BSS)
• Add more access points to form an Extended
  Basic Service Set (EBSS)

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Security

• Wireless networking devices provide no security
  out of the box
• Hackers may easily grab packets right out of the
  air and read them
• To provide better security, wireless networks use
  one of these methods
• Service Set Identification (SSID) or network
  names
• Media Access Control address filtering
• Data encryption

16
Service Set Identification

• The Service Set Identification (SSID) is a 32-bit
  string in the header of each packet
• Only wireless clients whose SSID matches can gain
  access to the network
• Wireless access points come with a generic SSID
  that is widely publicized by the vendor
• Linksys uses linksys
• 3Com uses 101
• Netgear uses wireless or netgear

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MAC Filtering

• MAC address filtering limits access based on the
  physical, hard-wired address of the wireless
  network adapter
• Any data packet whose MAC address is not listed
  in the wireless access points table is rejected
• Specified MAC addresses may be denied
• MAC addresses may be spoofed by hackers
• Each MAC address needs to be manually entered
  initially and kept up to date

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Encryption

• Encrypted data packets are electronically
  scrambled (locked) with a private encryption key
  before being transmitted
• The receiving device must possess the encryption
  key in order to unscramble (unlock) the packet
• Encryption is enabled through Wireless
  Equivalency Privacy (WEP) or Wi-Fi Protected
  Access (WPA) or WPA2

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Wireless Equivalency Privacy

• WEP uses a 64-bit encryption algorithm
• Works only on layers 1 and 2 (Physical and Data
  Link)
• Encryption key is static (same from session to
  session) and shared by all network nodes
• No user authentication

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Wi-Fi Protected Access

• WPA offers
• Dynamic encryption key generation issued on a
  per-user, per-session basis
• Encryption key integrity-checking feature
• User authentication through Extensible
  Authentication Protocol (EAP)
• Not available on all wireless devices

21
Speed

• Ranges from 2 Mbps to 54 Mbps
• Speed decreases as distance increases
• Speed is affected by interference from other
  networking devices and solid objects
• Dead spots may be created by things like
  refrigerators, air conditioners, metal plumbing

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Range

• Environmental factors greatly affect range
• Theoretical maximum ranges are usually listed,
  while the effective range may be about half as
  far
• To extend range
• Add more wireless access points
• Install a signal booster to increase the WAPs
  signal

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Broadcasting Frequencies

• The Federal Communications Commission (FCC) set
  aside the Industrial, Scientific, and Medical
  (ISM) frequencies for wireless networking
• 83.5 MHz of bandwidth in the 2.4 GHz frequency
  band
• 125 MHz of bandwidth in the 5.8 GHz band
• 300 MHz of bandwidth (Unlicensed National
  Information Infrastructure (U-NII)) split into
• 5.15 to 5.25 GHz frequency band
• 5.25 to 5.35 GHz frequency band
• 5.725 to 5.825 GHz frequency band

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Media Access Methods

• Multiple devices may share a medium by first
  listening in on the network media to see if it is
  busy
• Devices need to wait if it is busy for the length
  of a frame plus the Interframe Space (IFS)
• If two devices transmit at the same time a
  collision occurs and data is corrupted
• How are collisions dealt with?

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CSMA/CD

• Carrier Sense Multiple Access /Collision
  Detection
• When a collision occurs (is detected), the device
  will wait a random amount of time and then
  attempt to resend the data

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CSMA/CA

• Carrier Sense Multiple Access / Collision
  Avoidance
• Instead of reacting to collisions, steps are
  taken to avoid collisions using Distributed
  Coordination Function (DCF)
• Point Coordination Function (PCF) is defined but
  not implemented yet
• DCF requires receiving nodes to send an
  Acknowledgement (ACK) for every packet that tells
  other nodes to wait a certain amount of time
  before trying to access the media

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RTS/CTS

• Request To Send/Clear To Send (RTS/CTS)
• Transmitting nodes send an RTS frame to the
  receiving node before transmitting any data
• The receiving node responds with a CTS
• Another form of collision avoidance

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Wireless Networking Standards
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802.11 Standard

• IEEE 802.11 wireless Ethernet standard defines
  methods to communicate using spread-spectrum
  radio waves
• Broadcast data in small discrete chunks within a
  frequency range
• All 802.11 wireless technologies use the 2.4 GHz
  frequency
• Except for 802.11a that uses the 5 GHz frequency

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Broadcasting Methods

• Direct-sequence spread-spectrum (DSSS)
• Sends data out on difference frequencies at the
  same time
• Uses 22 MHz bandwidth
• Greater throughput
• More prone to interference
• Used by most 802.11-based wireless networking
  standards

• Frequency-hopping spread-spectrum (FHSS)
• Sends data on one frequency at a time
• Constantly shifts or hops frequencies
• Uses 1 MHz bandwidth
• Used by HomeRF wireless networks

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Wi-Fi Standards

• Most widely adapted wireless networking
  technology today
• Devices that conform to the extended versions of
  the 802.11 standard (802.11a, 802.11b, and
  802.11g) are Wi-Fi certified
• By the Wi-Fi Alliance (formerly the Wireless
  Ethernet Compatibility Alliance WECA)
• Wireless devices must use the same standard to
  communicate
• 802.11g is backwards compatible with 802.11b

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802.11

• The original standard
• Slow speed at 2 Mbps
• Limited range at about 150 feet
• Uses the 2.4 GHz broadcast range
• Security provided by WEP and WPA encryption
• Rare today

33
802.11a

• Operates in the 5 GHz frequency range with 8
  available channels
• Less crowded frequency range which reduces the
  chances of interference
• Speeds up to 54 Mbps
• Maximum range is around 150 feet
• Developed after 802.11b
• Not widely adopted

34
802.11b

• Throughput up to 11 Mbps
• Range up to 300 feet
• Security through WEP and WPA encryption
• Uses the 2.4 GHz frequency range with 14
  available channels (11 in the U.S.)
• Most widely used today which makes it more likely
  to suffer from interference

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802.11g

• Throughput up to 54 Mbps
• Range up to 300 feet
• Backwardly compatible with 802.11b
• Newest version
• Operates in 2.4 GHz range with 14 available
  channels (11 in the U.S.)

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802.11 Standards
Standard 802.11 802.11a 802.11b 802.11g
Maximum Throughput 2 Mbps 54 Mbps 11 Mbps 54 Mbps
Maximum Range 150 feet 150 feet 300 feet 300 feet
Frequency 2.4 GHz 5 GHz 2.4 GHz 2.4 GHz
Compatibility 802.11 802.11a 802.11b 802.11b, 802.11g
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802.11 Standards
Standard 802.11N
Maximum Throughput 300 Mbps
Maximum Range 150 feet
Frequency 2.4 GHz, 5GHZ
Compatibility 802.11a, 802.11bg, 802.3a/b, 802.3a/f, 802.3u and 802.3 standards.
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802.11 Standards

• Security methods used by all
• SSID
• MAC filtering
• Industry standards WEP, WPA
• Spread-spectrum method used by all
• DSSS
• Communication modes supported by all
• Ad-hoc
• Infrastructure

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HomeRF

• Intended for home usage
• Maximum range of 150 feet
• Maximum speed of 2 Mbps
• Version 2 maximum speed of 10 Mbps
• Uses FHSS spread-spectrum broadcasting method
  making it less susceptible to interference
• Uses a Network ID (NWID)
• 56-bit encryption algorithm
• 7 channels in the 2.4 GHz range (6 for voice, 1
  for data)

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Bluetooth

• Bluetooth creates small wireless networks called
  Personal Area Networks (PANs) between PCs and
  peripheral devices
• PDAs, printers, keyboards, mice, cell phones,
  home stereos, televisions, home security systems
• Basis for upcoming IEEE 802.15 standard
• Throughput from 723 Kbps to 1 Mbps
• Maximum range of 10 meters (33 feet)

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Bluetooth Operation Modes

• Operates in an automatic master/slave
  relationship
• One master controls up to seven slave devices
• A Bluetooth PAN is called a piconet (meaning very
  small)
• Up to 255 devices may participate but only seven
  may be active at a time
• An inactive slave device is called a parked device

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Bluetooth Communication Stages

• Device discovery
• Broadcasts its MAC address an a code identifying
  the type of device
• May set device to non-discovery mode to skip this
  stage
• Name discovery
• Device identifies itself by a friendly name
• Such as iPAQ Pocket PC
• Association
• Device officially joins the network
• Some devices require a PIN code for security
• Also called bonding, pairing, or joining
• Service profile
• Defines the kind of service it provides

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My Bluetooth Places
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Data Transfer

• Synchronous Connection-Oriented (SCO)
• Guarantees all data transmitted is received
• Good for file transfers
• Master nodes support up to 3 SCO connections at a
  time with up to 3 slave units

• Asynchronous Connectionless (ACL)
• No guarantee of delivery
• Faster
• Good for streaming media
• Point-to-point (master to slave) or broadcast
  (master to all slaves) links

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Bluetooth Services

• Services supported by Bluetooth are called
  profiles
• Generic Access Profile defines how units discover
  and establish connections
• Service Discovery Profile enables discovery of
  services other devices provide
• Cordless Telephony Profile defines wireless phone
  functionality
• Intercom Profile defines wireless intercom
  functionality
• Serial Port Profile enables a device to emulate
  serial port communication
• Headset Profile defines wireless telephone and PC
  headset functionality

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Bluetooth Services

• Dial-up Networking Profile defines capability to
  act as or interact with a modem
• Fax Profile defines capability to act as or
  interact with a fax device
• LAN Access Profile defines how a device accesses
  a LAN or the Internet
• Generic Object Exchange Profile defines how to
  exchange data with other devices
• Object Push Profile is used to exchange small
  data objects
• File Transfer Profile is used to exchange large
  data objects like files
• Synchronization Traffic is used to synchronize
  data between PDAs and PCs

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Bluetooth Services
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Bluetooth Security

• 128-bit encryption and per-user passwords
• Point-to-Point Tunneling Protocol (PPTP) and
  Secure Sockets Layer (SSL) for browser-based
  remote access
• MAC filtering
• Non-discovery mode to hide them from other devices

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Configuring Wireless Networking
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Wi-Fi and HomeRF

• Install a wireless network adapter the same way
  as a wired adapter
• Check Windows Device Manager after installation

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Configuring Ad-Hoc Mode

• Each wireless node must use the same network name
  (SSID)
• No two nodes can have the same IP address
• Ensure that File and Printer Sharing is running
  on all nodes

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Ad-Hoc Mode
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Configuring Infrastructure Mode

• Configure the same SSIC on all nodes and the
  access point
• You may also configure DHCP options, filtering,
  client channels, and more

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Access Point Configuration

• Uses a browser-based setup utility
• Point web browser to 192.168.1.1 and use the
  administrative password given in the
  documentation
• Various configuration options will be available
  such as SSID and whether to broadcast it

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Access Point Configuration
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Configuring MAC Filtering
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Configuring Encryption
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Encryption on Wireless NIC
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Bluetooth Hardware

• Comes integrated with many devices today
• To add Bluetooth capabilities you usually need to
  install an adapter
• Follow the instructions which usually require you
  to install your driver and configuration utility
  first
• Bluetooth devices seek each other out and
  establish master/slave relationships automatically

60
Connecting to PAN
iPAQ Bluetooth Manager software connected to
Bluetooth access point
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Bluetooth Access Point
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Troubleshooting Wireless Networks
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Scope of Problem

• Who is affected by the problem?
• Try to isolate whether the problem relates to a
  few client machines or to an access point
• What is the nature of their network problem?
• Can some network services to accessed while
  others cannot? Then the problem is most likely
  not related to their client equipment
• When did the problem start?
• What changed?

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Wi-FI and HomeRF

• Hardware
• Check Device Manager for resource conflicts
• Try reinstalling the device driver
• Software
• USB devices usually require that you first
  install the software before the hardware
• Update the devices firmware version to the latest

65
Connectivity

• Check the link light
• Check the configuration utility for link state
  and signal strength
• There could be interference or a weak signal

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Configuration

• Check your SSID and WEP configuration for typos
• Watch for blank spaces at the end of a SSID
• Make sure the MAC address of the client is on the
  list of accepted users
• Make sure the encryption strength matches

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Bluetooth

• Hardware
• Check for detection, driver or resource errors
• Make sure the device is seated properly
• Some newer Bluetooth devices only work with USB
  2.0
• Check Device Manager
• Software
• Always check the documentation before installing
  Bluetooth devices sometimes steps may not be
  performed out of order
• Only Windows XP (with service pack 1) and Apple
  OSX offer native support for Bluetooth

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Connectivity Configuration

• Check the configuration utility
• Remember Bluetooth range is limited to 30 feet
• Shut down other Bluetooth devices in the same
  area to see if there is interference
• Make sure all device use the same profile
• Check to see if non-discovery mode has been
  enabled
• Check the password or PIN
• Check the power-saving settings