Computer networks miscellaneous

Computer networks miscellaneous

Easy Questions

Computer Networks

Computer networks miscellaneous
  1. A computer network uses polynomials over GF(2) for error checking with 8 bits as information bits and uses x 3 + x + 1 as the generator polynomial to generate the check bits. In this network, the message 01011011 is transmitted as








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    The given generator polynomial (LRC)
    G(X) = X3 + X + 1
    ⇒ 1.X3 + 0.X2 + 1.X1 + 1.X0
    G(X) ⇒ 1 0 1 1
    Given message m(X) = 0 1 0 1 1 0 1 1.
    Then

    So, the message 01011011 is transmitted as 01011011101. So, option (c) is correct.

    Correct Option: C

    The given generator polynomial (LRC)
    G(X) = X3 + X + 1
    ⇒ 1.X3 + 0.X2 + 1.X1 + 1.X0
    G(X) ⇒ 1 0 1 1
    Given message m(X) = 0 1 0 1 1 0 1 1.
    Then

    So, the message 01011011 is transmitted as 01011011101. So, option (c) is correct.

  1. Consider the different activities related to email :
    m1 : Send an email from a mail client to a mail server.
    m2 : Download an email from mailbox server to a mail client.
    m3 : Checking email in a web browser.
    Which is the application level protocol used in each activity?








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    Sending an email will be done through user agent and message transfer agent by SMTP, downloading an email from mail box is done through POP, checking email in a web browser is done through HTTP.

    Correct Option: C

    Sending an email will be done through user agent and message transfer agent by SMTP, downloading an email from mail box is done through POP, checking email in a web browser is done through HTTP.

  1. The Protocol Data Unit (PDU) for the application layer in the Internet stack is








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    The Protocol Data Unit (PDU) are as follows :
    For application layer – Message
    For application layer – Segment
    For network layer – Data gram
    For data link layer – Frame

    Correct Option: C

    The Protocol Data Unit (PDU) are as follows :
    For application layer – Message
    For application layer – Segment
    For network layer – Data gram
    For data link layer – Frame

  1. Which one of the following statements is NOT correct about HTTP cookies?








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    Cookies are not Piece of code they are just strings typically in the form of key value pairs.

    Correct Option: A


    Cookies are not Piece of code they are just strings typically in the form of key value pairs.

  1. Consider a 128 × 103 bits/second satellite communication link with one way propagation delay of 150 milliseconds. Selective retransmission (repeat) protocol is used on this link to send data with a frame size of 1 kilobyte. Neglect the transmission time of acknowledgement. The minimum number of bits required for the sequence number field to achieve 100% utilization is ________ .








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    To achieve 100% efficiency, the number of frames that we should send = 1 + 2 × Tp / Tt where, Tp is propagation delay, and Tt is transmission delay. So, Number of frames sent = 1 + 4.687 = 5.687 (approx 6). As the protocol used is Selective repeat, Receiver window size should be equal to Sender window size. Then, Number of distinct sequence numbers required = 6 + 6 = 12 Number of bits required to represent 12 distinct numbers = 4

    Correct Option: C

    To achieve 100% efficiency, the number of frames that we should send = 1 + 2 × Tp / Tt where, Tp is propagation delay, and Tt is transmission delay. So, Number of frames sent = 1 + 4.687 = 5.687 (approx 6). As the protocol used is Selective repeat, Receiver window size should be equal to Sender window size. Then, Number of distinct sequence numbers required = 6 + 6 = 12 Number of bits required to represent 12 distinct numbers = 4