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Data Communication and Net-Centric Computing (COSC1111)
Answer questions (10 marks in total)
Q1 (5 marks)
Figure 1 shows the stop-and-wait flow control.
Figure 1 Stop-and-wait error control.
1. ACK0 is lost, explain in detail about what the sender and the receiver will do next. (1 mark)
2. When will the sender take action? Give your justification. (1 mark)
3. Packet switching is used for transmitting data. If the transmission time for one packet is 0.1 ms, it takes 20 ms for a packet being transmitted from sender to receiver. Does this mean that transmission delay of your data is shorter than propagation delay? Give your justification. (1 mark)
4. Explain in detail about how the router associates with the process in Figure 1? Your discussion should direct link to the time given in 3. (2 marks)
Q2 (5 marks)
Figure 2 shows a multiplexer in a synchronous Time Division Multiplexing (TDM) system. The bits arrive at the multiplexer is from channels A, B, then C. One frame will take 4 bits from each source. In channel A, each green block is the binary converted from your student ID based-on mod2 operation. B and C are the voice channels.
1. Give an example to show the details for adapting the voice signal of channels B and C into the multiplexer. (2 marks)
2. Based on above example, give the output stream of first two frames. (1 mark)
3. What kind of error may occur for the multiplexer collects input at Source C, and how this error affects the performance at receiver end? (1 mark)
4. Further to discuss how the above-mentioned error differs from the error at data link layer from system level. (1 mark)
Figure 2 Synchronised TDM Multiplexing.