# 旋转比特位

在QUIC工作组的设计讨论中，最长的主题之一就是旋转比特位，人们花费了数百封邮件和数百个小时来讨论它。

旋转比特位的支持者认为，两个QUIC端点之间路径上的运营商和人员需要有办法来测量延迟。

反对者则反感此功能潜在的信息泄露。

## 旋转一个比特

QUIC连接的客户端、服务器这两个端点各为每一个QUIC连接维护一个旋转的值——0或1，在传送时候它们在报文中设置该值。

然后，在每一次往返时，连接双方都翻转这一比特的值。效果是观察者可以检测该比特字段的0与1脉冲。

这一观测只在发送方未被应用层或流量控制限制的情况下有效，并且网络上经过重新排序的数据包也会给数据带来噪声。


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