Chapter 11Review questions1. What are wireless networks? Why are they useful?
2. Some cities took up projects to setup wireless LANs all over the city. Read about the project taken up by one such city. Was the project a success? Why, or why not?
3. What are some of the concerns with using wireless networks?4. What are ISM frequency bands? Why are they useful?
5. What are some differences between wired and wireless LANs? How do they impact the design of the wireless LAN header?
6. What is a basic service set? A basic service area?
7. What is an access point? What are some reasons why you would prefer access points to wireless routers to create a wireless network in your organization?
8. What is a distribution system in wireless LANs?
9. What is an extended service set?
10. What is a portal in a wireless LAN?
11. What are some differences between the physical layers in wireless and wired LANs?
12. What are the common wireless LAN categories? What are the important differences between them?
13. What is 802.11 n? What are some likely advantages of 802.11 n over the traditional wireless LANs? How does 802.11 n obtain these advantages?
14. What are personal area networks? How are they different from LANs?
15. What are some important characteristics of Bluetooth?
16. What is a piconet? What are some differences between a piconet and a basic service set?
17. What are master and slave devices in a piconet?
18. What is a scatternet?
19. What are some advantages of having distinct physical channels in Bluetooth?
20. Why is device discovery useful in Bluetooth? How is device discovery accomplished? Why is device discovery not needed in wireless LANs?
21. Describe the mechanisms that have been defined for WLANs and WPANs to coexist at the same frequency bands without interfering with each other.
22. What are the different categories of Bluetooth? What are they used for?
23. What are wireless MANs? What are their primary uses?
24. What data rates and ranges are likely to be available on wireless MANs?
25. What are the differences between wireless LANs and wireless MANs?
Hands-on exercise
1. Look at the first frame. What is the role of a Beacon frame in IEEE 802.11? Why is this frame not necessary in IEEE 802.3 Ethernet?
2. Which device on the wireless LAN sends out the beacon frame? Based on this information, what is the MAC address of the wireless router
3. Based on the above question and the information in the beacon frame header fields, what information serves as the basic service set (BSS) identifier?
4. The second packet in the capture is a probe request. What is the role of a probe-request frame in IEEE 802.11? Why is this frame not necessary in IEEE 802.3 Ethernet?
5. Which device(s) send(s) out probe requests?
6. What is the BSS ID of the destination in the probe request? What does this number signify?
7. How are frames identified as beacon frames or probe-request frames or data frames? (Hint: look at the type/ subtype field.)
8. Examine the MAC address fields in a few frames. What are the three MAC addresses included in all frames?
9. Recalling the Wireshark captures in Chapter 6, there were only two MAC addresses in the Ethernet header — source and destination. Why is it necessary to include a third MAC address, the BSS ID, in 802.11 frames?
Questions from the radio-header capture:
1. Select any frame in the capture and expand all the sub-headers of the radiotap header (e.g., present flags and flags). What is the channel frequency at which the frame was transmitted?
2. Briefly describe the channels used by 802.11 b/g.
3. Why is channel 6 one of the recommended channels for transmitting 802.11 wireless LAN data?
4. Was the frame transmitted using FHSS (Frequency Hopping Spread Spectrum) or OFDM (Orthogonal Frequency Division Multiplexing)?
Network design exercise
1. What wireless technology would you recommend to create the wireless LAN — IEEE802.11 a, IEEE802.11 b, IEEE803.11g, or IEEE802.11 n? Justify your choice.
2. Assume that both floors of the building have the same dimensions. Making typical assumptions about the needed work space for each employee, what is the total area in the building that needs wireless coverage?
3. Given your technology choice and the area calculated above, how many access points would you need to provide satisfactory coverage everywhere on both floors?
Update your network diagram from Chapter 10 to include the portal for the wireless subnet at Amsterdam.
Case questions
1. What are the different kinds of wireless data communication technologies used in the case?
2. What is a retain in the context of supply chains?
3. What is a runout in the context of supply chains?
4. What is a mesh network in the context of wireless sensor networks? What are its advantages and disadvantages? (Wikipedia is a good resource)
5. Why do companies with a nationwide footprint use satellite-based data networks for data transmission instead of wired networks such as DSL?
6. A leading provider of satellite-based data-communication services is DirecPC. Visit the company’s website and write a short (one-paragraph) report on the services offered by the company based on information provided at the website. Include information such as data rates, plan prices, and other information relevant to new subscribers.
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