如何从延迟和带宽计算数据包时间 [英] How to calculate packet time from latency and bandwidth

问题描述

我有一个主机和交换机之间的链接.

I have a link between a host and a switch.

链接有一个带宽&延迟.如何计算2个数据包(大小为1KB)从Host A传输到Switch 1的时间?

The link has a bandwidth & a latency. How to calculate the time of 2 packets(with size 1KB) to be transferred from Host A to Switch 1?

这是示意图(我说的是第一个链接)

Here's the diagram(I am talking about the first link)

注意:我只是想手动计算这些值，我想知道计算这些问题的原理/规律.

Note: I just want to calculate it manually for these values, I want to know the principles/laws of calculating these problems.

推荐答案

Propagation time = (Frame Serialization Time) 
                  + (Link Media Delay) 
                  + (Queueing Delay) 
                  + (Node Processing Delay - if known)

公式:

• 帧序列化时间 = S/R
• 链接媒体延迟 = D/p
• 排队延迟 = Q/R
• 通常指定或测量节点处理延迟
• R:链接数据速率(比特/秒)
• S:数据包大小(位)
• D:链接距离(米)
• P 处理延迟(秒)
• p:中等传播速度(米/秒)
  • 铜线速度为 210*10**6
  • 光纤中的速度为 300*10**6

  适用于您的问题:

  我只会计算主机 A 和交换机 1 之间的链接的信息:

  Frame Serialization Time =  Packet_size_bits / Link_data_rate_bps
                           = 2*1024*8 / (2*10**6)
                           = 0.00819 [seconds]
  Link Media Delay         = 0.04 seconds [from diagram: 40ms]
  Queueing Delay           = 0.0 [assume no congestion]
  Node Processing Delay    = 0.0 [Host A had nothing specified for delay]
  -----------------------------------------------------------------------
                 Total     = 0.00819 + 0.04 + 0.0 + 0.0
                           = 0.04819 seconds
                           = 48.2 milliseconds for two 1KB packets to go from 
                                               Host A to Switch 1
  

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