CS 228 Test #2

General Hospital Version
 
 
  1. (Yes/No) General Hospital Chief Surgeon Blake Steele says that the Aloha protocol is as efficient as slotted Aloha at using bandwidth and avoiding collisions.  Is he right?
  2. (Yes/No) General Hospital has a heart monitor that must occasionally send small, self contained messages to a central computer across a network.  These messages must get there or people will die.  Would sending a datagram per message be appropriate?
  3. General Hospital is a small yet scandal filled hospital, with only 150 or so computers.  General Hospital wants an address type that offers reasonable tradeoffs between bandwidth and latency.  General Hospital uses mostly IBM mainframes, but they do have a few UNIX workstations and a couple of Macs.  Doctors at General Hospital drive both Porches and BMWs.  What type of network address should they use?
    1. Class A
    2. Class B
    3. Class C
    4. Class D
    5. None or all of the above.
  4. Why doesn't everyone use a class A address?
    1. Class A addresses only allow 255 hosts per network; many institiutions have more hosts than that.
    2. Class A addresses are multicast addresses and not used for normal hosts.
    3. Class A addresses offer better bandwidth but increased latency.  This is a bad tradeoff for many institutions.
    4. All or none of the above.
  5. (Yes/No) Can Slotted Aloha offer guaranteed delivery?
  6. Suppose General Hospital chief computer gal Bubbles Blonde sets up a domain name system (DNS) server .  Why would she do this?
    1. To translate internet  addresses to ethernet addresses.
    2. To translate ethernet addresses to internet addresses.
    3. To cache WWW web pages for faster access.
    4. None or all of the above.
  7. Next,  General Hospital assistant  computer guy Buck Naked sets up an ARP server.  Why would he do this?
    1. To translate internet  addresses to ethernet addresses.
    2. To translate ethernet addresses to internet addresses.
    3. To cache WWW web pages for faster access.
    4. None or all of the above.
  8. Suppose a web browser at General Hospital trys to access the server www.hostpital.supply.corp.com.  How many name servers might that computer need to contact to translate this address into an internet address (IP number).   Suppose that  there is no useful information in any of the relevant caches.
    1. 0
    2. 1
    3. 2
    4. More than two
    5. All or none of the above.
  9. Suppose that www.general.hospital.com does exist, but that ftp.general.hospital.com does not.  Which would take more effort (more packets) to look up?
    1. WWW takes more effort
    2. FTP takes more effort
    3. The same
    4. Depends on the phase of the moon.
  10. General Hospital has a very heavily loaded local area network.  Which network technology would work best?
    1. Ethernet
    2. Token Ring
    3. Aloha
    4. None or all of the above.
  11. (Source/Not Source) General Hospital is going to be attached to the Internet.  Do computers attached to the internet generally choose the whole route when the packet is sent (source routing) or just choose the link to send the packet out on, trusting that the next computer in line can send it closer still to the destination.
  12. (Yes/No) In Ethernet, are all delays due to collisions of the same length?
  13. Suppose Stan Slimy gains access to the insides of his computer.  This computer is connected to an Ethernet, and he disables the exponential back off feature.  Now his computer retransmits as soon as it can after every collision.  Stan Slimy does this only to one computer (the one on his desk).  What effect will this have?
    1. Stan will crash the whole network.
    2. Stan will prevent his computer from talking to others.
    3. Stan will get better network throughput for his computer.
    4. Stan will get worse network throughput for his computer.
    5. None or all of the above.
  14. What is the main purpose of the token in Token Ring?
    1. Tells hosts when to listen.
    2. Tells hosts when the Token Master is down.
    3. Tells hosts when they can transmit.
    4. None or all of the above.
  15. General Hospital is going to attach devices to the hospital network.  For cost reasons these devices must use the minimum possible RAM, and use only simple algorithms (reduces programming costs).  What transmission protocol should they use.
    1. Alternating Bit
    2. Selective Repeat
    3. Go Back N
  16. (Yes/No) Will selective repeat receive data from the network yet delay handing that same data to an application?  (Be careful here, this question requires thought).
  17. In an environment with very low error rates, will the data throughput of Go Back N approximate that of selective repeat.
  18. In an enviornment with very high latency, what is the best criticism of the Alternating Bit protocol?
    1. Alternating bit is a complex algorithm with high overhead.
    2. Alternating bit will not keep the line busy transmitting useful data.  There will be too many idle periods.
    3. Alternating bit actually works well in an enviornment with high latency.
    4. All or none of the above.
  19. What layer in the OSI model handles retransmission of lost packets? _________________________________________
  20. Dr. Dijkstra works at General Hospital.  What does the unweighted version of his algorithm compute?
    1. The path with the shortest number of hops.
    2. The path with the smallest latency.
    3. The  path with the highest bandwidth.
    4. None or all of the above.
  21. What does the bind() system call do?
    1. Gives an otherwise anonymous socket an address.
    2. Tells the operating system how large the backlog of requests can be.
    3. Changes the socket to send datagrams instead of streams.
    4. Creates a file descriptor and connects that descriptor to a socket.
    5. All or none of the above.
  22. What does the accept() system call do?
    1. Gives an otherwise anonymous socket an address.
    2. Tells the operating system how large the backlog of requests can be.
    3. Changes the socket to send datagrams instead of streams.
    4. Creates a file descriptor and connects that descriptor to a socket.
    5. All or none of the above.
  23. Suppose General Hospital wants to network with its suppliers, which are scattered the city of Chicago and its suburbs.  Which network technology would make the best sense?
    1. Ethernet
    2. Token Ring
    3. Aloha
  24. (Client/Server) Which typically forks off multiple processes, clients or servers?
  25. (Throughput/Latency) Suppose you have a routing algorithm that can either optimize for throughput or for latency.  Which would be best for a typcial telnet/rlogin session?
  26. (Yes/No)  Debbie Diamond, General Hospital's network guru, says that the performance of a heavily loaded ethernet can be improved by requiring every station to begin its transmission at specific intervals, just like Slotted Aloha.  Would "Slotted Ethernet" see the same sort of performance increase over normal ethernet that Slotted Aloha sees over normal Aloha (This is a tricky question.  Be careful here.)
  27. Speaking Question: In ethernet, what is the relationship between minimum packet size and the maximum length of the network cable.
  28. Speaking Question:  I've said in class that there can be either guaranteed reliability or guaranteed throughput and latency.  Why can there be no guarantee for both at the same time?