networking - 计算机网络：第 70 段是在哪一轮传输中发送的？

Question

在练习一些练习时，我遇到了以下一些我无法理解的练习。查看解决方案，我不明白他们是如何得出在第 6 轮传输中发送数据包 32 到 63 的结论的。63 是如何计算的？

第 70 段是在哪一轮传输中发送的？

解决方案：

During the 1st transmission round, packet 1 is sent; 
packet 2-3 are sent in the 2nd transmission round; 
packets 4-7 are sent in the 3rd transmission round; 
packets 8-15 are sent in the 4th transmission round;
packets 16 to 31 are sent in the 5th transmission round; 
packets 32 to 63 are sent in the 6th transmission round; 
packets 64 to 96 are sent in the 7th transmission round. 
Thus packet 70 is sent in the 7th transmission round.

标签： networkingtcpprotocols

Answer 1

通过提供的练习链接，我们可以看到 TCP 传输在练习 1 的第 6 轮传输中从慢启动移动到拥塞避免（我们可以看到图形变化梯度，下一段说明原因）。

根据RFC 2001 Article .1 & .2( link )，我们可以看到，当我们进入 TCP 拥塞避免拥塞窗口大小 (cwnd) 时，每个传输轮的段大小仅增加 1。

再次查看练习（以及上面的注释），我们看到正在传输以下段大小（重要的是要注意数据包是包含在内的，因此传输第 6 轮包含 32 个数据包，第 7 轮包含 33 个数据包）：

During the 1st transmission round, packet 1 is sent;      | Current Window Size of (1)
packet 2-3 are sent in the 2nd transmission round;        | Increase window by 1 segment (2)
packets 4-7 are sent in the 3rd transmission round;       | Increase window by 2 segments (4)
packets 8-15 are sent in the 4th transmission round;      | Increase window by 4 segments (8)
packets 16 to 31 are sent in the 5th transmission round;  | Increase window by 8 segments (16)
packets 32 to 63 are sent in the 6th transmission round;  | Increase window by 16 segments (32)
*** Here we switch to Congestion Avoidance
packets 64 to 96 are sent in the 7th transmission round.  | Increase windows by 1 segment (33)

由于数据包是包含在内的，因此练习是正确的，说明数据包 32 一直到并包括数据包 63（所以让我们假设数据包 63 的结尾基本上是数据包 64 的开头）构成了第 6 轮传输。