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.
- 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.
- Explain in a few sentences how routers and DNS servers are
different. Use the the scenario of typing
www.realestate.com into a web browser to get to the web
page hosted by www.realestate.com in briefly explaining the key
differences between the two.
- 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?
- 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.
- Explain one or two substantive
similarities and differences between Wikipedia and prediction markets.
- 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.
- 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
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?
- In a few sentences what are the primary differences between how
you view the internet and how you think your parents view it.
- 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.
- 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.
- Hint: A good way to approach problems like this is to try a smaller example first where you can easily check your logic. So, a possible case here might be one where each address has 8 bits but the first 4 bits are fixed (or you could try it with an even smaller number of bits). Solving that is easier since you can actually write down the numbers involved. Once you understand that version, you can double-check your logic for the larger version of the problem (i.e. this midterm question).
- Bonus Question/Extra Credit (coming later)