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Final Exam
Operating Systems and Networking
CS330
Spring 2007
Answer three questions from Group A and two questions from Group B
Exam date: May 2, 2007 (3:00 to 5:00 PM at C106)
Policy: Open books, open notes
Group A (Answer at most three questions from this group)
1. One could speed up system performance considerably using well-designed caches.
Suggest how. Could cache be detrimental to system performance? Rationalize your
answer. How could one mitigate these problems?
2. Operating systems like UNIX are not usually geared for real-time applications
particularly for two reasons. One of them has to do with the way memory is used and the
other has to do with I/O functions. Elaborate.
3. For a virtual memory system, the page size is 8192 bytes. How many bits are required for
the offset in the address? Instead of using standard page-tables for resident processes,
could one consider hashing to aid logical to physical memory mapping? Under what
circumstances could it be a worthwhile proposition?
4. How does paged memory solve the problem of external fragmentation? Why does it not
solve the problem of internal fragmentation? If we make an attempt to reduce internal
fragmentation within a page what price need we pay, if any?
5. Many virtual memory systems prefer to use LRU page replacement scheme or its suitable
variations. Why is it the preferred choice? Under what circumstances might it be the
worst choice? Why is it avoided in its purest form?
Group B (Answer at most two questions from this group)
6. Assume that you want to send several small 1kb packets over a 10 Mb/s line to a station
5000 km away. However, your predicating protocol constrains you to release 1 packet at
a time until the last one is received and acknowledged. How well are you utilizing the
transmission system? Would this go up or climb down if you are allowed to transmit
10kb packets at a time? State your rationale.
7. What is the difference between a connectionless and a connection-oriented network
system? Give an example of each. Under what condition(s) one is preferred over the
other?
8. On a Token Ring Network, what happens when the token gets corrupted? Suggest a
strategy to recover from such a state.
9. What are the IP addresses used or spanned by the CIDR address 192. 168.10.0/20?
Bonus: (Max marks: 15 points)
The NY Times article on “Computer Science takes steps to bring women to the fold” that the
class was invited to read and review indicated a steady decline in interest in pursuing “Computer
Science” as a viable career option not just among women but among population at large in the
Western world. Assuming that the observation is primarily sound, what suggestions, in your
opinion, does it lead to so far as the future Operating Systems architecture is concerned? Do you
think the future OS and its application interface should change to mitigate this trend? If so, how?