通过电路交换网络将 640,000 位的文件从主机 A 发送到主机 B 需要多长时间？
只是复习一道考试题，无法找出正确的解决方法。问题如下：
How long does it take to send a file of
640,000 bits from host A to host B over a
circuit-switched network?
- All links are 1.536 Mb/s
- Each link uses TDM with 24 slots/sec (TDM = Time Division Multiplexing)
- 500 msec to establish end-to-end circuit
在我看来，答案是
x = (1.536 * 10^6) / 24
y = 640,000 / x.
Answer : y + 500 * 10^-3
我有一种感觉，但这是灾难性的错误。有人可以帮我吗？ :)
Just going over an exam question and can't figure out the correct method to solve it. The question is as follows :
How long does it take to send a file of
640,000 bits from host A to host B over a
circuit-switched network?
- All links are 1.536 Mb/s
- Each link uses TDM with 24 slots/sec (TDM = Time Division Multiplexing)
- 500 msec to establish end-to-end circuit
To my mind, then, the answer would be
x = (1.536 * 10^6) / 24
y = 640,000 / x.
Answer : y + 500 * 10^-3
I have a feeling this is catastrophically wrong though. Can anyone help me out please ? :)
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该链路的速率为 1,536 Mbps，但采用时分复用。
一条电路使用一个时隙，这意味着它获得链路带宽的 1/24。因此，一条电路的带宽为 64 Kbps (=1.536/24)。
因此，通过该电路传输 640.000 位 (=640 Kb) 的实际传输时间为 10 秒 (=640/64)。
添加 500 毫秒的连接设置时间，总共为 10.500 毫秒或 10.5 秒。
The link is 1,536 Mbps, but is time divisioned multiplexed.
One circuit uses one timeslot, which means it gets 1/24th of the link bandwidth. So, one circuit has a bandwidth of 64 Kbps (=1.536/24).
So the actual transfer time to move 640.000 bits (=640 Kb) over that circuit is 10 seconds (=640/64).
Add the connection setup time of 500 msec and you get a total of 10.500 msec or 10,5 seconds.
每个电路的传输速率为 (1.536 Mbps)/24 = 64 kbps。
传输文件需要（640,000 位）/（64 kbps）= 10 秒。
在这 10 秒中添加电路建立时间，得到 10.5
发送文件的秒数。
请注意，传输时间与链接数量无关：
如果端到端电路传输时间为 10 秒
通过一个链接或一百个链接
Each circuit has a transmission rate of (1.536 Mbps)/24 = 64 kbps.
It takes (640,000 bits)/(64 kbps) = 10 seconds to transmit the file.
To this 10 seconds we add the circuit establishment time, giving 10.5
seconds to send the file.
Note that the transmission time is independent of the number of links:
The transmission time would be 10 seconds if the end-to-end circuit
passed through one link or a hundred links
一条电路在 TDM 中使用一个时隙，因此，在这种情况下，它是链路带宽的 1/24。 1.536 Mbps = 1536 Kbps。 1536/24=每个时隙可传输64 Kb。文件为640000位=80 Kb。 80/64= 1.25 秒传输文件。添加连接建立时间1.25秒+500毫秒。
One circuit uses one time slot in TDM, therefore, in this case its 1/24th of the link bandwidth. 1.536 Mbps = 1536 Kbps. 1536/24=64 Kb can be transmitted in each time slot.The file is 640000 bits = 80 Kb. 80/64= 1.25 sec to transmit the file. Add the connection setup time 1.25sec+500msec.