Chapter 7: Wireless

Chapter 7: Wireless
Chapter 7: Wireless
* What is 802.11a?
- Speed? Frequency band? Distance (range)?
- What is the advantage and disadvantage of 802.11a?
There are some important disadvantages to using the 5 GHz band.
– The first is that higher frequency radio waves are more easily absorbed by
obstacles such as walls, making 802.11a susceptible to poor performance
due to obstructions.
– The second is that this higher frequency band has slightly poorer range than
either 802.11b or g.
* What is 802.11b?
- Speed? Frequency band? Distance (range)?
- What is the advantage and disadvantage of 802.11b?
* What is 802.11g?
- Speed? Frequency band? Distance (range)?
- What is the advantage and disadvantage of 802.11g?
Advantages of using the 2.4 GHz band.
• Devices in the 2.4 GHz band will have better range than those in the
5GHz band.
• Transmissions in this band are not as easily obstructed as 802.11a.
Disadvantage to using the 2.4 GHz band.
• Many consumer devices also use the 2.4 GHz band and the devices to be
prone to interference.
– microwave ovens, Bluetooth devices, baby monitors and cordless
* What is 802.11n?
- Speed? Frequency band? Distance (range)?
- What is the advantage and disadvantage of 802.11n?
The IEEE 802.11n draft standard is intended to improve WLAN data rates and
range without requiring additional power or RF band allocation.
802.11n uses multiple radios and antennae at endpoints, each broadcasting on
the same frequency to establish multiple streams.
* Before an 802.11 client can send data over a WLAN network, it goes through the
following three-stage process:
– Stage 1 - 802.11 probing
– Stage 2 - 802.11 authentication
– Stage 3 - 802.11 association
* What are some basic ways to control access to wireless LAN?
– SSID cloaking - Disable SSID broadcasts from access points
– MAC address filtering - Tables are manually constructed on the access point to
allow or disallow clients based on their physical hardware address
– WLAN security implementation - WPA or WPA2
* Wireless security?
 2 types of authentication with the original 802.11: open and shared WEP key
– While open authentication is really "no authentication," (a client requests
authentication and the AP grants it),
– WEP authentication was supposed to provide privacy to a link. The flaws
with WEP shared key encryption were.
 Today, the standard in most enterprise networks is the 802.11i standard.
– This is similar to the Wi-Fi Alliance WPA2 standard.
– For enterprises, WPA2 includes a connection to a Remote Authentication
Dial In User Service (RADIUS) database.
* What is “man-in-the-middle” attack? How do you prevent it?
 Defeating an attack like a MITM attack, depends on the sophistication of your
WLAN infrastructure and your vigilance in monitoring activity on the network.
– The process begins with identifying legitimate devices on your WLAN.
– To do this, you must authenticate users on your WLAN.
– When all users are known, you then monitor the network for devices and
traffic that is not supposed to be there.
* What is BSS? What is ESS?
* What is CSMA/CA? What problem is CSMA/CA method is designed to solve?
* What is “rogue access point”?
• A rogue access point is an access point placed on a WLAN that is used to
interfere with normal network operation.
• A rogue access point also could be configured to provide unauthorized user’s
* What is “site-survey”? * What is purpose of “site-survey”?
 A site evaluation involves inspecting the area with the goal of identifying potential
issues that could impact the network.
* When configure a wireless router, you need to know all the basic terminology?
- Network mode?
- Network name (SSID)?
- Radio band?
- Wide channel?
- Standard channel?
- SSID Broadcast?
* What are the known wireless security faults about the SSID?
- What is the problem with the default SSID name?
- Will disable the broadcast SSID completely prevent it from been discovered?
* What are the issues of channel overlapping?
 Interference can occur when there is overlap of channels.
 It is worse if the channels overlap close to the center frequencies,
* The Linksys WRT300N used is three devices in one box.
– First, there is the wireless access point, which performs the typical functions of
an access point.
– In essence, an access point converts the TCP/IP data packets from their
802.11 frame encapsulation format in the air to the 802.3 Ethernet frame
format on the wired Ethernet network.
– A built-in four-port, full-duplex, 10/100 switch provides connectivity to wired
– Finally, the router function provides a gateway for connecting to other network
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