transition delay 和 propagation delay 定义

transition delay是传输延迟
就是你和主机的距离除以光速所得的值

propagation delay是传播延迟
你的网络都是有一定带宽的，比如每秒只能传输4MB/s的数据
而你要传播40MB的数据，那么它的传播延迟就是40/4=10s

晕，段成华的作业吧
Propagation delay, symbolized tpd, is the time required for a digital signal to travel from the input(s) of a logic gate to the output. It is measured in microseconds (µs), nanoseconds (ns), or picoseconds (ps), where 1 µs = 10-6 s, 1 ns = 10-9 s, and 1 ps = 10-12 s.
The propagation delay for an integrated circuit (IC) logic gate may differ for each of the inputs. If all other factors are held constant, the average propagation delay in a logic gate IC increases as the complexity of the internal circuitry increases. Some IC technologies have interently longer tpd values than others, and are considered \"slower.\" Propagation delay is important because it has a direct effect on the speed at which a digital device, such as a computer, can operate. This is true of memory chips as we