Computer networks miscellaneous

Computer networks miscellaneous

Easy Questions

Computer Networks

Computer networks miscellaneous
  1. A layer-4 firewall (a device that can look at all protocol headers up to the transport layer) cannot








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    Since, it is a layer 4 firewall, it cannot block application layer protocol like HTTP.

    Correct Option: A

    Since, it is a layer 4 firewall, it cannot block application layer protocol like HTTP.

  1. Consider that B wants to send a message m that is digitally signed to A. Let the pair of private and public keys for A and B be denoted by Kx- and Kx+ for x = A, B, respectively. Let Kx (m) represent the operation of encrypting m with a key Kx and H(m) represent the message digest. Which one of the following indicates the CORRECT way of sending the message m along with the digital signature to A?








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    Correct Option: B

  1. The message 11001001 is to be transmitted using the CRC polynomial x3 + 1 to protect it from errors. The message that should be transmitted is








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    The message P(x) = 11001001
    Divisor, D(x) = 1001
    CRC Remainder = 011
    Therefore, the transmitted message comes out to be – 11001001011

    Correct Option: B

    The message P(x) = 11001001
    Divisor, D(x) = 1001
    CRC Remainder = 011
    Therefore, the transmitted message comes out to be – 11001001011

  1. In Ethernet when Manchester encoding is used, the bit rate is








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    Manchester coding is the process by which digital information in a binary bit stream is converted into electrical signals for transmission. It uses a two-state transition of line voltage to represent one bit of information. In other words, two baud (voltage changes) are used for one bit (piece of information).

    Manchester coding has the advantage of enabling data to be transmitted without the need for an extra clocking signal.

    Correct Option: A

    Manchester coding is the process by which digital information in a binary bit stream is converted into electrical signals for transmission. It uses a two-state transition of line voltage to represent one bit of information. In other words, two baud (voltage changes) are used for one bit (piece of information).

    Manchester coding has the advantage of enabling data to be transmitted without the need for an extra clocking signal.

  1. Let G(x) be the generator polynomial used for CRC checking. What is the condition that should be satisfied by G(x) to detect odd number of bits in error?








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    The solution is just based on the very basic concepts regarding CRC checking. There are two ways by which the solution can be out by using the basic concepts.
    Solution 1 –
    There are odd numbers of bit in the error. Due to which, the error function will have a factor of (1 + x2 + x4 + ....). Now this can never be divided by the generator having Now this can never be divided by the generator having (1 + x) as a factor.
    Solution 2 –
    In a polynomial code method, the sender and receiver mutually agrees on a generator polynomial G(x). Here, both of the high order bit and the low order bit and the low order bit of the generator must be 1. Hence, 1 + x is a factor of G(x).

    Correct Option: C

    The solution is just based on the very basic concepts regarding CRC checking. There are two ways by which the solution can be out by using the basic concepts.
    Solution 1 –
    There are odd numbers of bit in the error. Due to which, the error function will have a factor of (1 + x2 + x4 + ....). Now this can never be divided by the generator having Now this can never be divided by the generator having (1 + x) as a factor.
    Solution 2 –
    In a polynomial code method, the sender and receiver mutually agrees on a generator polynomial G(x). Here, both of the high order bit and the low order bit and the low order bit of the generator must be 1. Hence, 1 + x is a factor of G(x).