Data Communication and Computer Networks - Data Communication

63. In stop-and-wait ARQ, if data 1 has an error, then receiver sends which frame ?

  • Option : D
  • Explanation : Stop-and-wait ARQ (Automatic Repeat Request) is similar to stop - and - wait flow control protocol, but it includes retransmission of data in case of lost or damaged frames.
    Both data and ACK frames are numbered alternately 0 and 1. But NAK frames are not numbered. If any error occurs the Receiver sends a NAK frame, it tells the sender to retransmit the frame last sent. Sender maintains a copy of frame until the Acknowledgement is back.
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64. In which communication, poll/select method used to determine control of the line ?

  • Option : D
  • Explanation : Poll / select method is used in primary - to - secondary communication. ENQ/ACK is used in peer-to-peer communication method.
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65. The secondary device in a multipoint configuration sends data in response to which of the following event ?

  • Option : C
  • Explanation : Poll/select is a line discipline method. The primary device always initiates communication with either a poll or select (SEL) frame. In this point the secondary device sends data in response to a poll frame event.
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