1. Wireless Networking
Chapter 15

2. Objectives Explain wireless networking standards
Describe the process for implementing Wi-Fi networks
Describe troubleshooting techniques for wireless networks

3. Historical/Conceptual

4. Introduction to Wireless Networking
Wireless network uses radio frequency (RF) waves to communicate between devices
Enables flexibility and mobility
Uses the same OSI layers as wired networks
Except first two OSI layers
Differs from wired networking in type of media and protocols for transmitting and accessing data
The dominant wireless implementation is Wi-Fi
IEEE wireless Ethernet standard
Note (p. 429): Because the networking signal is freed from wires, you’ll sometimes hear the term unbounded media to describe wireless networking.
Note (p. 429): The CompTIA Network+ objectives draw a clear distinction between wireless technologies that enable devices to access the Internet, such as WiMAX and LTE, and wireless technologies that you use to create a network. You read about the former in Chapter 14; now you’re going to learn about the latter: Wi-Fi.

5. Test Specific
Wi-Fi Standards

6. Wi-Fi Standards
Wi-Fi is by far the most widely adopted wireless networking type today
Wi-Fi technologies have been around since the late 1990s
Supported and standardized under the umbrella IEEE standard
Examples of amendments: g and ac
Note (p. 429): Wi-Fi originally stood for wireless fidelity, to make it cutely equated with high fidelity (Hi-Fi), but it doesn’t really stand for anything anymore.

7. 802.11 Standards define how wireless devices communicate
Also address communication security
established the baseline features common to all Wi-Fi standards
Wireless network cards, configuration software, capability to run in multiple network styles
How transmissions work

8. Hardware Wireless Ethernet NICs
Same function as wired, except transmission uses radio waves
Networking capabilities are built into many modern devices
Can add an expansion card to desktop computers
USB NICs are placeable

9. Figure 15.1 Wireless PCIe NIC

10. Figure 15.2 External USB wireless NIC

11. Wireless Access Point (WAP)
Interconnects wireless network nodes with wired networks
A basic WAP operates like a hub at Layer 1
Often multiple devices combined in one box
Built-in switch and/or router
Cross Check: Using Routers (p. 430)
You’ve seen wired routers before, and wireless routers function similarly, so cross-check your memory. Turn to Chapter 2, and see if you can answer these questions. If you’re checking your memory, you’re not turning to Chapter 2  What can a router do for your network? Can you use a router to connect to the Internet? At what layer of the OSI seven-layer model do routers function? How do routers handle addressing?
Note (p. 430): Many manufacturers drop the word “wireless” from wireless access points and simply call them access points. Furthermore, many sources abbreviate both forms, so you’ll see the former written as WAP and the latter as AP.

12. Figure 15.3 Linksys device that acts as wireless access point, switch, and DSL router

13. Software Wireless device drivers
Consult your vendor’s instructions
Wireless configuration utility settings
Link state
Signal strength
Wireless network modes
Security encryption
Power-saving options

14. Figure 15.4 Wireless client configuration utility

15. Wireless Network Modes
Ad hoc mode
Also called peer-to-peer mode
Uses a mesh topology
Works well for small groups of computers or temporary networks
Independent Basic Service Set (IBBS)
Two or more wireless nodes communicating in ad hoc form

16. Figure 15.5 Wireless ad hoc mode network

17. Wireless Network Modes (cont’d.)
Infrastructure mode
Uses one or more WAPs to connect the wireless network nodes centrally
Similar to a wired star topology
Basic service set (BSS)
Serviced by a single WAP
Extended service set (ESS)
Serviced by two or more WAPs
Cross Check: Topologies (p. 432)
The physical topology of a network represents the connectivity between nodes. This seems as good a time as any to cross-check your knowledge of topologies, so recall Chapter 3 and answer these questions. What are the four standard topologies? What are the hybrid topologies? If you connect a wireless network in infrastructure mode to a wired Ethernet network, what topology would that combined network have?
Tech Tip: EBSS vs. ESS (p. 433)
Many techs have dropped the word “basic” from the Extended Basic Service Set, the early name for an infrastructure-mode wireless network with more than one WAP. Accordingly, you’ll see the initials for the Extended Basic Service Set as ESS. Using either EBSS or ESS is correct.

18. Figure 15.6 Wireless infrastructure mode network

19. Range Wireless networking range is hard to define
Greatly affected by environmental factors
Qualifiers such as around 150 feet and about 300 feet
Actual range is about half of manufacturer’s listed maximum range

20. Basic Service Set Identifier (BSSID)
The most basic infrastructure mode network
A BSS of one WAP and one or more wireless clients
The BSSID is the same as the MAC address of the WAP
IBSS nodes (ad hoc mode) generate a 48-bit string as the BSSID
BSSID is added in every frame

21. Service Set Identifier (SSID)
Another level of naming
Standard name applied to the BSS or IBSS
Sometimes called a network name
32-bit identification string
In the header of each frame processed by a WAP
Every Wi-Fi device must share the same SSID to communicate in a network

22. Extended Service Set Identifier (ESSID)
A Wi-Fi network with multiple WAPs (ESS)
Each WAP is connected to a central switch or switches to become part of a single broadcast domain
Clients connect to whichever WAP has the strongest signal
Roaming: process of changing WAP connections
Most Wi-Fi devices use the term SSID
Exam Tip (p. 434): The CompTIA Network+ certification exam uses the two terms—SSID and ESSID—interchangeably. Concentrate on these two terms for the exam

23. Broadcasting Frequency
Potential for interference from other wireless devices
Wireless devices must operate in specific broadcasting frequencies
A tech must know frequencies of other wireless devices in troubleshooting interference issues
Original standards use 2.4-GHz or 5.0-GHz frequencies

24. Broadcasting Methods
Original IEEE standard used spread-spectrum radio waves
Broadcasts data in small, discrete chunks
Uses different frequencies within a range

25. Spread-Spectrum Broadcasting Methods
Direct-sequence spread-spectrum (DSSS)
Frequency-hopping spread-spectrum (FHSS)
Orthogonal frequency-division multiplexing (OFDM).

26. Direct-Sequence Spread-Spectrum (DSSS)
Sends simultaneously on different frequencies
Used by early standards
Uses about 22 MHz of bandwidth
Capable of greater data throughput than OFDM
More prone to interference than FHSS

27. Frequency-Hopping Spread-Spectrum (FHSS)
Constantly shifts (hops) from frequency to frequency
Sends on one frequency at a time
Uses less bandwidth than DSSS (~1MHz)

28. Orthogonal Frequency-Division Multiplexing (OFDM)
Latest method
Combines multiple frequencies of DSSS with FHSS’s hopping capability
Used on all but the earliest networks
Note: The n and ac devices use a special version of OFDM called Quadruple-amplitude modulated (QAM).

29. Channels A channel is a portion of the spectrum
standard defined 14 channels of 20MHz each
Different countries may limit channels
In the U.S., WAP may use channels 1 through 11
Do not use adjacent channels on nearby WAPs
Most WAPs use channels 1, 6, or 11

30. Channels (cont’d.)
The 5.0-GHz band offers many more channels than the 2.4-GHz band
There are 40 different channels in the spectrum
versions that use the 5.0-GHz band use automatic channel switching

31. Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA)
Wireless devices cannot detect collisions
Cannot listen and send at the same time
If two clients were to collide, there is no simple-to-detect electrical peak
Two collision avoidance methods
Distributed Coordination Function (DCF)
Point Coordination Function (PCF)
Exam Tip (p. 435): Wired Ethernet networks use CSMA/CD. Wi-Fi networks use CSMA/CA. Cellular networks, as you’ll recall from Chapter 14, “Remote Connectivity,” use CDMA/CD. All three are close, letter-wise, so pay attention on the exam.

32. DCF and PCF Only DCF is implemented
DCF specifies rules for sending data onto the network media
Defines a backoff period in addition to the normal interframe gap (IFG) wait period
Requires an ACK from receiving nodes
Exam Tip (p. 436): Current CSMA/CA devices use the Distributed Coordination Function (DCF) method for collision avoidance.

33. 802.11b Data throughput up to 11 Mbps Range up to 300 feet Popular
Uses the crowded 2.4-GHz frequency
More likely to have interference from other wireless devices
Signal interference can increase latency
Exam Tip (P. 436): As you read about the many speeds listed for , you need to appreciate that wireless networking has a tremendous amount of overhead and latency. WAPs send out almost continuous streams of packets that do nothing more than advertise their existence or maintain connections. Wireless devices may sometimes stall due to processing or timeouts.
The end result is that only a percentage of the total throughput speed is actually achieved in real data bits getting to the applications that need them. The actual number of useful bits per second is called the goodput of the wireless network.
Note (p. 436): Despite the a designation for this extension to the standard, a was available on the market after b.

34. 802.11a Devices on market after 802.11b
Different from all other standards
5-GHz frequency range
Speeds up to 54 Mbps
Short range: about 150 feet
Never as popular as b
Incompatible with b

36. 802.11g Up to 54 Mbps Range of 802.11b: about 300 feet
Backward compatible with b
WAP can service both b and g
All g network runs in native mode
Runs in mixed mode if b devices added
Communications drop to 11 Mbps max
Exam Tip (p. 438): If an g device shows a connection type of g-ht, this means it is connecting to an n WAP running in mixed mode.

37. 802.11n Faster and newer antenna technology
Most devices must use multiple antennas
Multiple in/multiple out (MIMO)
Up to 600 Mbps theoretically
Many WAPs employ transmit beamforming
Dual-band WAPs run at 2.4- and 5.0 GHz
WAPs support b/g/n devices
Note (p. 438): For a broadcasting method, the n and ac devices use a special version of OFDM called quadruple-amplitude modulated (QAM).

38. 802.11ac Expansion of the 802.11n standard
Incorporates additional streams
Wider bandwidth
Better speed
Only operates in the 5.0 GHz band
Multiuser Mimo (MU-MIMO)
Can broadcast to multiple users simultaneously

40. Wi-Fi Protected Setup (WPS)
A special standard created by the wireless industry to makes configuration easier
Works in two modes
Push button
PIN method
Easy to use
Susceptible to various WPS attacks

41. Wi-Fi Security Problem Three wireless security methods
Easy-to-install devices have no default security
Network data frames are in radio waves
Three wireless security methods
MAC address filtering
Authentication
Data encryption
Note (p. 439): All the methods used in wireless network security— authentication, encryption, MAC address filtering—can be considered network hardening techniques.

42. MAC Address Filtering Limits access to specific NICs
Lists MAC addresses for accepted users
The list is stored in a table in the WAP
Rejects frames with other MAC addresses
Alternatively create an exclusion list
Not scalable on a modern network
Problem: hackers can spoof MAC addresses
Exam Tip (p. 439): WAPs use an access control list (ACL) to enable or deny specific MAC addresses. Note that a WAP’s ACL has nothing to do with ACL in NTFS; it’s just the same term used for two different things.
Exam Tip (p. 439): MAC filtering with a whitelist means you allow only specific computers to join the network. When you deny specific computers, you create a blacklist. Whitelisting and blacklisting are labor-intensive processes, with whitelisting requiring far more work.

43. Wireless Authentication
Users with proper credentials get access
Can use a centralized security database
Requires extra steps for wireless users
802.1X standard
RADIUS server
Extensible Authentication Protocol (EAP) password encryption

44. Wireless Authentication (cont’d.)
RADIUS server
Provides authentication for network access
Enables access to user’s rights on the network
Client wireless computer is called a supplicant
WAP is the Network Access Server (NAS)
NAS contacts the RADIUS server
RADIUS server checks the security database
User is given access if credentials are correct
Note (p. 440): RADIUS stands for Remote Authentication Dial In User Service. Say that five times.

45. Figure 15.7 Authenticating using RADIUS

46. Wireless Authentication Problem Areas
Connection between devices must be secure
PPP between supplicant and WAP/NAS
IPsec between NAS and RADIUS server
RADIUS server uses an authentication protocol (EAP)
WAP and wireless NICs must use the same authentication scheme
Note (p. 441): EAP and RADIUS servers for authentication paint half the picture on 802.1X security implementation. The other half is WPA2, discussed in “Data Encryption Using WPA2.”

47. Figure 15.8 Authentication using RADIUS with protocols in place

48. Figure 15.9 Setting EAP authentication scheme

49. Data Encryption Encryption electronically scrambles data packets
The receiving network device requires the encryption key to unscramble the packet
WPA2 provides a good level of security to data packets in transit

50. Data Encryption Using WEP
Wired Equivalent Privacy (WEP)
64- or 128-bit encryption algorithm called RC4
Uses an initialization vector (IV) of 24 bits
Issues with WEP
IV length uses 24 of the 64 (or 128) bits
Encryption key is static and shared
No user authentication
Outdated and easily cracked
Note (p. 442): RC4 officially stands for Rivest Cipher 4, named after its creator, Ron Rivest. Unofficially, but possibly more likely, the RC stands for Ron’s Code.

51. Wi-Fi Protected Access (WPA)
Dynamic encryption key generation
Issued per user and per session
Temporal Key Integrity Protocol (TKIP)
128-bit encryption key
Problem: key can be broken

52. Wi-Fi Protected Access 2 (WPA2)
Uses Advanced Encryption Standard (AES)
128-bit block cipher
Not completely hack proof
Difficult enough to deter casual hackers
Adding a RADIUS server for authentication enables WPA2-Enterprise
Exam Tip (p. 443): The CompTIA Network+ exam objectives refer to WPA-PSK and WPA2-PSK as hardening options, but call them WPA-Personal and WPA2- Personal. Be prepared for any of these terms.

53. Enterprise Wireless Enterprise devices differ from SOHO devices
Robust construction
Centralized management
VLAN pooling
Power over Ethernet
Bringing personal wireless devices into the enterprise environment

54. Robust Device Construction
Enterprise WAP is made of better materials
More configurable
Can swap out antennas and radios making it possible to upgrade to the latest technologies

55. Figure 15.10 Cisco Enterprise WAP

56. Enterprise Wireless Administration
Large number of WAPs
Offload configuration job to a wireless controller
Switch designed to handle multiple WAPs
Thick client: configurable via its own interface
Thin clients: configurable by a wireless controller
Standard protocol: Lightweight Access Point Protocol (LWAPP)
Note (p. 444): Wireless controllers have a number of names. Wireless Switch, Wireless LAN switch, wireless controller, etc.

57. Figure 15.11 Configuring WAPs

58. Figure 15.12 Wireless Controller

59. VLAN Pooling
A large number of clients may be on a single SSID at a given moment
Traditional solution
Divide the WLAN into multiple broadcast domains
Use routers to interconnect the domains
VLAN pooling
Create a pool of VLANs for a single SSID
Randomly assign wireless clients to one VLAN

60. Power over Ethernet (PoE)
Power and Ethernet signals via Ethernet cables
Good for WAPs far from power outlets
The WAP and the switches must support PoE
2003: original PoE standard 802.3af
Supported a maximum 15.4 watts of DC power
Revised in 2009 to support 25.5 watts
New amendment called 802.3at or PoE+

61. Bring Your Own Device
Integrating personal mobile devices into a corporate network
Network administrators can allow or deny mobile devices access to network resources
On- and off-boarding mobile devices
Mobile device management solutions
Provide robust security without compromising connectivity

62. WLAN vs. PAN Wireless LAN (WLAN) Personal Area Networks (PAN)
Always an based network and able to serve multiple clients
Personal Area Networks (PAN)
Point-to-point over short distances
Examples: Bluetooth, infrared, and NFC

63. Implementing Wi-Fi

64. Steps for Installing a Wireless Network
Perform a site survey
Install one or more access points
Configure the access point(s) and wireless clients
Test the network to verify that it works as intended

65. Performing a Site Survey
Reveals obstacles and determine best locations for access points
Main components for crating a site survey
Floor plan of the area
Wireless survey tools

66. Performing a Site Survey
What wireless is already there?
Discover wireless networks in the same area
Today’s challenge is the preexistence of high device density environments
Tools are available to assist with the survey
Interference sources
Create a sketch of potential interference sources
Plan the network to eliminate dead zones

67. Figure 15.13 AirMagnet Survey Pro

68. Figure Acrylic Wi-Fi

69. Figure 15.15 Site survey with heat map

70. Figure 15.16 Site survey with interference sources noted

71. Installing the Client Install Wi-Fi hardware and software PCIe NIC
Install the NIC onto a free slot on the motherboard
May need to attach the antenna
USB NIC
Install drivers and software before you connect the NIC to the computer

72. Figure 15.17 Wi-Fi NIC installed

73. Setting Up an Ad Hoc Network
Set NICs for ad hoc mode
SSID
Each wireless node must use the same network name
IP addresses
No two nodes can use the same IP address
Ensure the File and Printer Sharing service is running on all nodes
Try This! Ad Hoc-ing (p. 450)
If you have access to a Wi-Fi-enabled device and a friend or classmate has one as well, try this! Set up your Wi-Fi for ad hoc using the configuration utility, and then try to connect with your partner. Use default settings. Once you connect with the defaults, you can start playing with your ad hoc network! If you’re in Windows 7, select Home for your network and set up a HomeGroup. Copy the sample images from one machine to another. Throw a big file into a Public folder and try copying that one, too. Then do it again, but with variations of distance and channels. How far can you separate your devices and still communicate? What happens if you change channels in the configuration utility, such as moving both devices from channel 6 to channel 4?

74. Figure 15.18 Selecting ad hoc mode in a wireless configuration utility

75. Setting Up an Infrastructure Network
Determine the optimal location for the WAP
Configure the WAP
Configure any clients to access the WAP

76. Placing the Access Points/Antennas
Omnidirectional antenna
Radiates outward from the WAP in all directions
Antenna is place the in the center of the area
Standard straight-wire dipole antennas are used
Omnidirectional and centered does not work for every network
The gain from a typical WAP is 2 dB
Increase gain with one or more bigger antennas

77. Figure 15.19 WRT54G showing two antennas

78. Figure 15.20 Room layout with WAP in the center

79. Figure 15.23 Dipole radiation pattern

80. Figure 15.24 Replacement antenna on a WAP

81. Placing the Access Points/Antennas (cont’d.)
A unidirectional antenna focuses a radio wave into a beam
Various types: parabolic, dish, and Yagi
Patch antennas work well for a strong signal within a room
Optimal placement depends on space needs and security concerns

82. Configuring the Access Point
Log in to the browser-based setup utility
Configure the SSID (ESSID) and beacon
Configure MAC address filtering
Configure encryption
Configure channel and frequency
Configure the client

83. Figure 15.27 Security login for Linksys WAP

84. Figure 15.28 Linksys WAP setup screen

85. Figure 15.29 Setting the beacon interval

86. Figure 15.30 MAC address filtering configuration screen for a Linksys WAP

87. Figure 15.31 Encryption key configuration screen on Linksys WAP

88. Figure 15.32 Encryption screen on client wireless network adapter configuration utility

89. Figure 15.33 Encryption screen with RADIUS option

90. Figure 15.34 Changing the channel

91. Figure 15.35 Selecting frequency

92. Figure 15.36 Typing in an SSID manually

93. Extending the Network Add a WAP to create an Extended Service Set
Install a wireless bridge
Connect two wireless networks; or join a wireless and a wired network together
Types of wireless bridges: point-to-point and point-to-multipoint
Note (p. 459): Some manufacturers market special Wi-Fi extenders or repeaters that pick up the Wi-Fi signal wirelessly and repeat it into a wider space.

94. Figure 15.37 Linksys wireless bridge device

95. Verify the Installation
Move traffic between computers using the wireless connection
Always verify installation before leaving

96. Troubleshooting Wi-Fi

97. Logical Troubleshooting Steps
Three types of symptoms
Cannot get on the wireless network
Wireless connections are way too slow
Wireless connection is doing weird things
Exam Tip (p. 460): Be prepared for scenario questions that quiz you about the limits of the wireless standards, or what CompTIA calls wireless standard related issues. This includes throughput speeds (11-, 54-, 100+-Gbps), frequencies, distances, and channel usage. See the above standards discussions for the limitations of each standard.
Exam Tip (p. 460): You can use wireless scanning tools to check for wireless channel utilization. These are software tools that give you metrics and reports about nearby devices and which one is connected to which WAP. These tools enable you to discover overworked WAPs, saturated areas, and so on, so you can deploy WAPs to optimize your network.

98. No Connection Channel problems Wrong encryption Overlapping channels
Mismatched channels
Wrong encryption
Entered the wrong encryption key
Symptoms: not on network, continual prompting for password, APIPA address
Solution: enter the correct password
Note (p. 461): Interference can also cause signal loss but I choose to treat this as a separate issue later in this section. For now we are talking about simple signal loss due to insufficient power.

99. No Connection (cont’d.)
Signal/power issues
Symptoms: signal loss, not able to connect
Solutions:
Move closer to the WAP and avoid dead spots
Turn up the power
Replace the omnidirectional antenna with a unidirectional antenna
Upgrade to newer n or ac

100. Figure 15.38 Increasing power on a Cisco WAP

101. Slow Wireless Connections
Clear connection to an SSID
Good IP address
Potential causes of slowness
Too many devices overworking WAPs
Too much RF interference on the network
Insufficient RAM
Malware
Other non-wireless specific issues
Note (p. 462): There are plenty of reasons for a device to run slowly that have nothing to do with wireless. Don’t forget issues such as insufficient RAM, malware, and so forth.

102. Overworked WAPs Device saturation Bandwidth saturation Bounce
Too many devices attaching to a single SSID over time
Bandwidth saturation
Bounce
Solutions: add extra WAPs, upgrade hardware to ac

103. Interference Sources of radio frequency interference (RFI)
Non-Wi-Fi sources including lighting, Bluetooth, wireless phones, and microwaves
Wi-Fi networks
Solution: abandon the 2.4-GHz channel
Scan for RF sources using some type of RF scanner/analyzer
Note: Don’t forget that any form of interference can change as well as being intermittent. Scanning for RF interference is an ongoing process.

104. Figure 15.39 SNR on AirMagnet

105. Weird Connection Open (non-encrypted) 802.11 networks Wrong SSID
Untested updates/incompatibilities
Rogue access point (rogue AP): an unauthorized access point