網路與通訊概論HW#3

Due: 5/

  1. [6-14] Give an example of a situation in which a virtual LAN might be a useful tool in a business environment. What about in an educational environment?
  1. [6-16] A transparent switch is inserted between two local area networks ABC and XYZ. Network ABC has workstations 1, 2 and 3, and network XYZ has workstations 4, 5, and 6. Show the contents of the two routing tables in the bridge as the following packets aretransmitted. Both routing tables start off empty.

•Workstation 2 sends a packet to workstation 3.

•Workstation 2 sends a packet to workstation 5.

•Workstation 1 sends a packet to workstation 2.

•Workstation 2 sends a packet to workstation 3.

•Workstation 2 sends a packet to workstation 6.

•Workstation 6 sends a packet to workstation 3.

•Workstation 5 sends a packet to workstation 4.

•Workstation 2 sends a packet to workstation 1.

•Workstation 1 sends a packet to workstation 3.

•Workstation 1 sends a packet to workstation 5.

•Workstation 5 sends a packet to workstation 4.

•Workstation 4 sends a packet to workstation 5.

  1. [6-17] Given the following network (see the following figure), show how the Spanning Tree Protocol will eliminate the cyclic path.
  1. [7-16] Your wireless LAN device has just sent a request to send (RTS). What happens next?
  1. [7-19] If it is important not to lose any of your data, which RAID technique would you suggest using?

6. [8-3] Suppose you want to send 1000 characters of data. How many total bits will you transmit using asynchronous transmission? How many total bits will you transmit using synchronous transmission? Assume that all 1000 characters will fit within one synchronous transmission frame.

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假設1 character = 8 bits

asynchronous transmission 使用1 start bit, 1 stop bit, 1 parity bit

synchronous trnasmission 的 1 個 frame 使用Start flag (8 bits) + Address (8 bits) + Control (8 bits) + CRC (16 bits) + End flag (8 bits)

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7. [8-13] Terminals A, B, and C are connected to a mainframe computer. Only terminal C has data to transmit. Show the sequence of messages sent between the mainframe and the three terminals using roll call polling.

8. [9-10] Mobile user A is using code division multiplexing and has been assigned a binary code of 00001111. Mobile user B, also using code division multiplexing, has been assigned a binary code of 01010101. Mobile user A transmits a 1, while Mobile user B transmits a 0. Show the sum of products that results and your calculations.

9. [9-12] The cell phone company in town uses code division multiplexing to transmit signals between its cell phones and the cell towers. You are using your cell phone while standing next to someone using her cell phone. How does the system distinguish the two signals?

10. [9-15] Ten computer workstations are connected to a synchronous time division multiplexor. Each workstation transmits a 128 kbps. At any point in time, 40 percent of the workstations are not transmitting. What is the minimum necessary speed of the line leaving the multiplexor? Will the answer be different if we use a statistical multiplexor instead? Explain your reasoning.