Compsci 82, Fall 2008, Midterm

In completing this midterm you may use books, notes, internet search engines and the web. You may not communicate with anyone about this test except for Prof. Astrachan or the TA, Sam Slee. In turning in the midterm you are affirming you adherence to the Duke Community Standard in completing this midterm.

In answering the questions be thorough, but brief. Do not dump facts hoping that they help convey the depth of your knowledge. Marshall arguments and facts to be brief in answering the questions.

Note: Any hints or clarifications for these questions will be posted on this page as well.

Be sure your name is on all pages you submit electronically.
  1. The IETF develops standards such as those for IPv4, for email, for BGP, and for secure DNS (there are thousands of Internet standards developed by the IETF). Briefly, provide reasons why it is unlikely that the IETF will develop standards for Internet voting.

  2. Explain in a few sentences how routers and DNS servers are different. Use the the scenario of typing into a web browser to get to the web page hosted by in briefly explaining the key differences between the two.

  3. Originally IETF specified that Internet addresses would be allocated in blocks, so companies or organizations wanting IP addresses received a block of addresses containing either 256 addresses, 65,536 addresses or 16,777,216 addresses. Changing IP address allocation so that blocks could be allocated in sizes that were any power of 2 rather than only 28, 216, or 224 was done in 1993. Why was this change a good idea and why are powers of 2 used?

  4. A group of techno-terrorists claims that they've set up 13 explosive devices to bring down the 13 root servers in the Domain Name System. Explain the likelihood of the group's success in bringing down the internet based on this plan if they succeed in detonating 13 highly powerful devices.

  5. Explain one or two substantive similarities and differences between Wikipedia and prediction markets.

  6. The acronym FUD stands for Fear, Uncertainty, and Doubt. It's typically used to describe a tactic in business, public relations, or politics of spreading false or misleading information. How can the web both fuel the spread of FUD and help combat it. Consider in your discussion the Pew Research pole that 12% of Americans think that Obama is Muslim.

  7. An mp3 file is music data stored as zeros and ones, in binary. An mp4 file is video data stored as zeros and ones. Suppose you rename the file song.mp3 to video.mp4. You don't change the zeros and ones stored in the file, just the name. Many browsers will still play the downloaded file as music/audio, not as video. How does this work?

  8. In a few sentences what are the primary differences between how you view the internet and how you think your parents view it.

  9. Skype is widely regarded as a secure system for communicating. Why might Skype users be more interested in security than cell phone users? Provide a plausible reason that Skype is free whereas an ecrypted cell phone costs more than $1,500 dollars.

  10. Suppose Duke University moves to IPv6 and decides that every machine supported at Duke will have a unique IP address and that every machine will have an IP address with the same, shared 100-bit prefix. How many devices with unique IP addresses can be supported if they all share the same 100-bit prefix using IPv6.
  11. Bonus Question/Extra Credit (coming later)