If present, this value indicates the protocol-level extension (s) the client wishes to speak.

这个值代表客户端计划使用的协议级别扩展信息。

youdao

We didn't anticipate, at that time, what's happening now, which is, you're seeing value get stripped out of the client and into the server, which makes it even more important to be in the cloud, so to speak.

我们那个时候没有预计到现在的情况，也就是说，现在,客户端的价值向服务器转移，所以拥有云技术,就更加重要了。

斯坦福公开课 - 戴尔CEO-Michael.Dell谈创业和发展课程节选