CS 417 Exam 2

Fall 2006

    Part I - 28 Points

  1. 5 points
    State an advantage of sequential (Unix) file access semantics over session semantics in a distributed file system.
  2. 5 points
    What happens when an exclusive oplock on a client is broken under CIFS?
  3. 5 points
    Why does AFS usually impose less traffic on a server than NFS?
  4. 5 points
    Why might a file open operation be more expensive under Coda than under AFS?
  5. 8 points
    The clock in the clock tower in the town of Chronos broke. It was repaired but now the clock needs to be set. A train leaves for the nearest town, Temporis, 100 miles away. It returns 4½ hours later with a report that the time, according to the clock tower in Temporis, is 4:05.
    (a) To what value should the time be set on the clock tower?
    (b) The maximum speed that the train can travel is 50 mph. What is the error of the clock?

    Part II - 72 Points

    For each statement, select the most appropriate answer.
  6. Multiprocessor systems are characterized by:
    (a) shared memory.
    (b) a high-speed processor-to-processor interconnect.
    (c) a crossbar switch.
    (d) All of the above.
  7. Which file systems implement a remote access model?
    (a) NFS only.
    (b) NFS and SMB.
    (c) NFS , Coda, and SMB.
    (d) NFS , Coda, and AFS.
  8. The Chandy-Misra-Haas deadlock probing algorithm:
    (a) sends a message to see if it comes back to the originator.
    (b) sends queries to systems to see if they are deadlocked.
    (c) allows a server to identify which process generated the deadlock.
    (d) forces a timestamp ordering of resource allocation that prevents deadlocks.
  9. False deadlock can be fixed by:
    (a) reliable message transmission.
    (b) proper message ordering.
    (c) atomic multicasts.
    (d) avoiding the use of a central server.
  10. An AFS callback for a file causes:
    (a) clients to invalidate that file in their cache.
    (b) clients to write any outstanding modifications out to the server.
    (c) the server to propagate updates of the file to clients.
    (d) clients to release any locks on the file.
  11. Event a has a Lamport timestamp of 4. Event b has a Lamport timestamp of 8. What can we tell about events a and b?
    (a) Events a and b are causally related.
    (b) Events a and b are concurrent.
    (c) Event a happened before event b.
    (d) If events a and b are causally related, then event a happened before event b.
  12. Which event is concurrent with the vector timestamp (2, 4, 6)?
    (a) (3, 5, 7)
    (b) (1, 3, 5)
    (c) (1, 4, 6)
    (d) (1, 4, 7)
  13. A client has a time of 5:05 and a server has a time of 5:25. Using the Berkeley algorithm, the client's clock will be set to:
    (a) 5:15
    (b) 5:20
    (c) 5:25
    (d) 5:30
  14. Which offers the most fault-tolerant message delivery?
    (a) Atomic multicast.
    (b) Totally ordered reliable multicast.
    (c) Causally-ordered reliable multicast.
    (d) Hardware multicast.
  15. When we had to send an IP packet over an ethernet network, we found the corresponding ethernet address via the Address Resolution Protocol (ARP). How do we find the ethernet address that corresponds to a particular IP multicast address??
    (a) All IP multicast packets use the same reserved ethernet address.
    (b) ARP is also responsible for handling multicast addresses.
    (c) By mapping some of the bits of an IP multicast address onto an ethernet address.
    (d) By mapping all of the bits of an IP multicast address onto an ethernet address.
  16. How does IP multicast achieve reliable packet delivery?
    (a) It doesn't.
    (b) Via best-effort multicast.
    (c) Via atomic multicast.
    (d) Via IGMP (Internet Group Management Protocol).
  17. A copyset is used:
    (a) in a DSM system that employs page caching.
    (b) in a DSM system as an alternative to page caching.
    (c) to implement lazy release consistency.
    (d) to implement entry consistency.
  18. An ethernet card may support all of the following mechanisms for multicasting except:
    (a) filtering packets based on a hash of the multicast address.
    (b) searching through a small table for a matching ethernet addresses.
    (c) searching through a larger table of ethernet addresses in main memory.
    (d) accepting all multicast packets via multicast promiscuous mode.
  19. If a frequency analysis of ciphertext reveals a statistical equivalence to the corresponding frequencies of plain English text, we can guess that the cipher is:
    (a) a monoalphabetic substitution cipher.
    (b) a polyalphabetic substitution cipher.
    (c) a transposition cipher.
    (d) a rotor machine.
  20. A rotor machine implements:
    (a) a monoalphabetic substitution cipher.
    (b) a polyalphabetic substitution cipher.
    (c) a transposition cipher.
    (d) a one-time pad.
  21. False sharing in a DSM system refers to:
    (a) an unwanted page being cached on another system.
    (b) unrelated data being resident on the same page.
    (c) invalid data in the directory, leading the system to falsely believe the page is shared.
    (d) two versions of the same page being present on one system.
  22. A bully election algorithm:
    (a) picks the first process to respond to an election request.
    (b) relies on majority vote to pick the winning process.
    (c) assigns the role of coordinator to the process holding the token at the time of election.
    (d) picks the process with the largest ID.
  23. Which mutual exclusion algorithm works when the membership of the group is unknown?
    (a) Centralized.
    (b) Ricart-Agrawala.
    (c) Lamport.
    (d) Token Ring.
  24. Weak consistency models offer an advantage over sequential consistency because:
    (a) memory synchronization does not have to occur with each memory operation.
    (b) caching may be used.
    (c) only the needed data needs to be shared, not the entire memory system.
    (d) they ensure that each write operation invalidates or updates all cached copies before the next instruction is executed.