浏览器如何知道站点是否支持HTTP/2? [英] How does a browser know if a site supports HTTP/2?

问题描述

如果我键入 https://http2.golang.org/，Chrome浏览器将自动发送HTTP/2请求.怎么做?

If I type out https://http2.golang.org/ the chrome browser will automatically send the HTTP/2 request. How is this done?

推荐答案

以stackoverflow为例，当浏览器向stackoverflow.com发送请求时，它必须执行以下步骤:

Take stackoverflow for example, when the browser sends a request to stackoverflow.com, it has to do the following steps:

1. DNS查找.找到stackoverflow的IP地址.
2. TCP/IP握手
3. TLS握手.
4. HTTP请求/响应(应用协议).
5. ....

TLS握手

关于step3 TLS握手，有一个很好的解释.

为了检查TCP/IP数据包的详细信息，可能需要使用一些工具来捕获数据包.例如 Wireshark .

In order to inspect the detail of TCP/IP packet, You may need use some tools to capture packets. e.g. Wireshark.

• 支持的密码套件.您喜欢哪些密码套件?
• 支持的TLS版本.
• 一个随机数.
• 受支持的应用程序协议.例如HTTP/2，HTTP 1.1/Spdy/..
• ...

• supported cipher suite. which cipher suites do you like?
• supported TLS version.
• a random number.
• the supported Application Protocols. e.g. HTTP/2, HTTP 1.1/ Spdy/..
• ...

• 选择密码套件.
• 选择TLS版本.
• 随机生成的数字
• 然后，在 TLS应用层协议协商(ALPN)中选择的应用协议. HTTP/2

• chosen cipher suite.
• chosen TLS version.
• a random generated number
• And, chosen application protocols in TLS application-layer protocol negotiation (ALPN), e.g. HTTP/2

HTTP2请求/响应发生在步骤4中.在此之前，浏览器已经知道服务器是否通过TLS握手支持HTTP/2.

HTTP2 request/response happens in step4. Before that, browser has already know whether sever support HTTP/2 through TLS handshake.

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