Hints for Exercises: Chapter 5

  1. Spread spectrum wireless has an interesting and surprising history. Read up on this.

    "Spread Spectrum: Hedy Lamarr and the mobile phone", by Rob Walters looks like an interesting book, but there are many links on the Web.

  2. 802.11b has rapidly been supplanted by 802.11g. At the time of writing 802.11g with WEP security is the strongest widespread wireless system, commercially speaking, with WPA starting to be supported. What is the current system of choice at the time of reading?

    Currently, 802.11g is still strong, but some vendors are producing "pre-11n" equipment in the hope that they will corner the next wave of wireless systems. WPA is appearing on new access points, with some support in operating systems on the hosts. The push to replace WEP by 802.11i is taking its time to get going.

  3. Take a walk around your neighbourhood with your wireless-enabled laptop. How many wireless networks can you find? How many are unprotected? Don't try to use them without permission.

    The answer to this can be quite depressing: despite the issues of protection being widely known there are still a large number of unprotected networks around. Take care to distinguish unencrypted networks from unprotected networks.

  4. Write a review of last-mile technologies. Which do you think is the most suitable for the lab/department/house you are in? Explain.

    Links. Another cost/benefit analysis. This one should change as technology develops.

  5. Look into the various ways cellular telephone operators are providing data access to your mobile phone. Make sure you compare data rates and costs.

    SMS, MMS, Web, video messaging, ringtones, wallpapers, and so on. And don't forget voice!

  6. Investigate the Ethernet addresses of the machines on your local network. Are there any security issues with ARP?

    You can use the arp command to see the current cache of ARP addresses. To find more, you can ping a host to get it into the cache.

    ARP is open to spoofing. Host A could send an gratuitous ARP reply for host B containing its own hardware address. The other machines on the local network would then start sending data destined for B towards A, thus allowing A to (a) read B's data (on a switched network A would not normally be able to see B's data), and (b) deny B any data. Fortunately, this can only redirect data within the local network.

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