Computer  Science 881
                        Quiz 9  -         Name ________________________

1. The system call that causes a TCP passive open is:

   a. bind                     b. listen

   c. accept                   d. connect

2. 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

3. 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.










4. 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.

Suppose a 3 way handshake is being used to establish a connection.
Let SYN1 represent a packet that carries SYN and no ack.
Let SYN2 represent a packet that carries both SYN and ACK that is
sent in response to a SYN1

5. A delayed duplicate SYN1 received in the CLOSED / LISTEN state is

   a. detected because of wrong  b. Detected because of wrong ACK
      SEQ number.                   number.

   c. Undetected and responded   d. Responded to with a SYN 1.
      to with a SYN2.

6. A delayed duplicate SYN1 received the SYN sent state is:
   detected because:

    a. Detected because the       b. Detected because SYN1 is
       SEQ number is wrong.          unexpected in the SYN sent state

    c. Detected because the       d. Undetected and responded to
       ACK number is wrong.          with an SYN2

7. A delayed duplicate SYN1 received in the ESTABLISHED state is:

    a. Responded to with RESET.   b. Responded to with a data packet
                                     specifying current ACK and SEQ.

    c. Responded to with SYN2     d. Always causes TCP to crash.

8. The sequence of states through which a client passes when a client
   initiates a close is:

    a. Close-wait, last-ack,      b. Fin-Wait-1, Closing, Time-Wait
       Closed                        Closed

    c. Fin-Wait-1, Fin-wait-2     d. Close-Wait, Last-Ack, Closed
       Time-wait, Closed

9. The sending of a packet with the "FIN" bit set indicates that

   a. No more data will be        b. No more data will be
      sent                           received

   c. both a. and b.

10. Why is it the case that servers should not pass through the
    time-wait state but it does not cause a problem for clients
    to do so?













11. Suppose that a segment is received by a TCP. An ACK will be generated

    a. As soon as there is traffic          b. As soon as the 200 ms timer
       to send in the other direction.         expires.

    c. As soon as either (a.) or (b.)       d. As soon as both (a.) and (b.)
       occurs                                  occur

12. Ack timing is done in TCP by

    a. Starting a new 200 ms timer each     b. Using a single global timer
       time a segment is received.             that ticks every 200 ms.

    c. Using a time stamp carried in
       each arriving segment.