Chapter 7: Wireless
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* 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 telephones.
* 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 authentication.
– 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 access.
* 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 devices.
– Finally, the router function provides a gateway for connecting to other network infrastructures.