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CS 1652 Midterm

By Walter Greene,2014-06-18 00:16
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CS 1652 Midterm ...

    CS 1652 Final Exam

    Fall 2001

Name _______________________________________

Instructions:

1. The exam is closed booked, closed notes.

    2. You may not use a calculator.

    3. All questions refer to the Kurose and Ross textbook. For example,

    for the purposes of this test, assume Kurose and Ross explanation

    of the TCP congestion control heuristics for any question dealing

    with congestion control.

    4. Answer on the exam sheet in the space provided.

    5. The test is probably long, don’t dawdle.

    6. Get to the point quickly in your answers.

1. (2 points) Within the context of cyclic redundancy checks (CRC) how

    does the receiver detect bit errors?

2. (4 points) In CDMA host A wants to send host B the message 1

    using code 1, 1, 1, 1, -1 and host C wants to send the message 1

    to host D using the code 1, 1, -1, -1, -1. Show what A and C

    transmit, what C and D receive, and what B and D view as the

    decoded message.

3. (4 points) Assume that you have a 100 Mbps Ethernet segment where

    the speed of the medium is 300,000,000 meters per second. How long

    can the Ethernet segment be so that a node will be sure that it will

    detect a collision? Recall the minimum sized frame is 576 bits. Show

    your work.

4. (6 points) Assume you have a 100 Mbps physical medium on which

    1000 users are trying to share. We consider two situations. In the

    lightest situation, only 1 user is trying to use the medium. In the

     2

heaviest situation, all 1000 users are trying to use the medium. For

    each of the following MAC protocols, give the effective throughput

    that you would expect for each of the lightest and heaviest situations.

    Throughput is the number of bits per second that arrive at a receiver

    that the bits were intended for.

    a. TDMA

    b. Slotted Aloha. You may assume that the broadcast probability

    is picked optimally in each situation.

5. (6 points) Assume that the host with IP address 222.222.222.221

    sends a datagram packet to the host with IP address 111.111.111.112,

    and then the host 222.222.222.222 sends a datagram to host

     3

    111.111.111.112. Give a linear list of the steps that are involved at the

    network and link layer. Assume that the ARP tables are initially

    empty.