List of top Computer Networks Questions on Data Link Layer

Consider a network using the pure ALOHA medium access control protocol. Each frame is of length 1000 bits and the channel rate is 1 Mbps. The aggregate transmission attempt rate is 1000 frames per second. The throughput of the network (rounded to the nearest integer) is \(\underline{\hspace{2cm}}\).
Consider the cyclic redundancy check (CRC) based error detecting scheme having the generator polynomial $X^3 + X + 1$. Suppose the message $m_4 m_3 m_2 m_1 m_0 = 11000$ is to be transmitted. Check bits $c_2 c_1 c_0$ are appended at the end of the message by the transmitter using the above CRC scheme. The transmitted bit string is denoted by $m_4 m_3 m_2 m_1 m_0 c_2 c_1 c_0$. The value of the checkbit sequence $c_2 c_1 c_0$ is

Consider the sliding window flow-control protocol operating between a sender and a receiver over a full-duplex error-free link. Assume the following:

  • The time taken for processing the data frame by the receiver is negligible.
  • The time taken for processing the acknowledgement frame by the sender is negligible.
  • The sender has infinite number of frames available for transmission.
  • The size of the data frame is 2,000 bits and the size of the acknowledgement frame is 10 bits.
  • The link data rate in each direction is 1 Mbps (= 106 bits per second).
  • One way propagation delay of the link is 100 milliseconds.

The minimum value of the sender’s window size in terms of the number of frames (rounded to the nearest integer) needed to achieve a link utilization of 50% is  .