Practice Final Exam CS4514

The questions are based on material presented in class and reading material from the text.

Give brief answers to the following questions:

  1. Given the below figure:

    Assume a 802.6 MAN. Which stations wants to transmit and who do they want to transmit to? Give a range of stations, if necessary.

  2. Ethernet frames must be at least 64 bytes long to ensure that the transmitter is still going in the event of a collision at the far end of the cable. Say we want Faster Ethernet to have the same minimum frame size, but can get the bits out 2 times faster. What do we have to change in the specification to do this?

  3. Consider a TCP connection between host A and host B. Suppose that the TCP segments traveling from host A to host B have source port number x and destination port number y. What are the source and destination port numbers for the segments traveling from host B to host A?

  4. Describe why an application developer may choose to run its application over UDP rather than TCP.

  5. Is it possible for application to enjoy reliable data transfer even when the application runs over UDP? If so, how?

  6. Suppose A sends two TCP segments back-to-back to B. The first segment has sequence number 90; the second has sequence number 110.

    1. How much data is the first segment?
    2. Suppose that the first segment is lost, but the second segment arrives at B. In the acknowledgement that B sends to A, what will be the acknowledgment number?

  7. True or False: Consider congestion control in TCP. When a timer expires at the sender, the threshold is set to one half of its previous value?

  8. Consider the following simple telnet example:


    Sequence and acknowledgment numbers for a simple Telnet application over TCP

    Assume we enable Nagle's algorithm and the user types "C" and then "A" and then "T". Re-work the above example with the proper sequence numbers.

  9. Compare and contrast link-state and distance-vector routing algorithms.

  10. Suppose an application generates 40 bytes of data every 20 msec, and each chunk gets encapsulated in a TCP segment and then an IP datagram. What percentage of each datagram will be overhead and what percentage will be application data?

  11. Consider the following topology:

    With the routing table for D:
    destination
    network
    next
    router
    distance
    1
    A
    2
    20
    B
    2
    30
    B
    7
    10
    --
    1
    ....
    ....
    ....

    Now, suppose that D receives from A the following advertisement:
    destination
    network
    next
    router
    distance
    30
    C
    10
    1
    --
    1
    10
    --
    1
    ....
    ....
    ....

    Will the table in A change? If so how?

  12. Why are different inter-AS and intra-AS protocols used in the Internet?

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