Computer  Science 881
                        Quiz 9  -         Name ________________________

1. For each of the following system calls used in a client / server
   application answer S, C, or B based upon whether the call would
   normally be used by the Server, the Client or Both

   ____ a. socket()

   ____ b. connect()

   ____ c. listen()

   ____ d. accept()

3. Answer the following B or NB depending on whether the system call
   is  Blocking or NonBlocking (a Blocking system call is one in which
   an arbitrarily long delay can occur between making the call and
   the return form the call).

   ____ a. bind()

   ____ b. listen()

   ____ c. accept()

4. The system call that causes a server to block until a client
   makes a connection request is:

   a. bind                     b. listen

   c. accept                   d. connect


5. Suppose I am building a server and I know a malicious hacker
   resides at address 130.127.48.24. How do I avoid interacting
   with this hacker while at the same time permitting every other
   IP address in the world to request my service.






6. Which of the following best describes the connection model used
   in the multi-threaded (multi-process) server we described in class.

   a. Each server process was       b. Each server process used the
      connected through a unique       same port and socket.
      port.

   c. Each server process used the  d. Each server process was connected
      same port but used a unique      through a unique port but they
      socket.                          all used the same socket.


7. For the following examples, answer (Yes) or (No) depending upone
   whether it represents the reprehensible practice of "shrinking
   the window"


   ___ (1)     <--- ack=4096,wnd=2048
                    seq=4096,size=1024 -->
               <--- ack=5120,wnd=1024

   ___ (2)     <--- ack=4096,wnd=2048
                    seq=4096,size=1024 -->
               <--- ack=5120,wnd=768

8. Consider a multihop channel with the following bit rates:

       8Kb         4Kb        2Kb         8Kb
   A -------- B -------- C --------- D -------- E

   Suppose packets are 1 Kbit in size and that host A injects
   packets at a rate of 8 packets per second.

   a. At what rate in packets / second will packets accumulate
      (or have to be discarded) at router B.


   b. At what rate in packets / second will packets accumulate
      (or have to be discarded) at router C.



   c. At what rate in packets / second will packets be delivered
      to host E.



9. Suppose the round trip transit time is 50 msec and the output
   bit rate is 4,000,000 bits / second.  How large must the offered
   window be in BYTES for a sender to be able to send continuously
   without having to stop and wait for ACKS.







10. Dynamically increasing the window size in response to congestion

   a. Is a good idea and necessary  b. Is a very bad idea and may
      to maintain throughput.          cause a "congestion collapse"

   c. May temporarily increase
      congestion but will not cause
      any type of major "collapse".

11. TCP's timeout and retransmission procedure

    a. Adds 1 second to the timeout      b. Doubles the timeout delay
       delay each time the same packet      up to a maximum of 64 secs.
       times out up to a limit of 6 sec.

    c. Adds 1 second but with no upper   d. Doubles the interval with
       bound.                               no upper bound.