Timeline

timeline 展示了各种时间指标。

Stalled/Blocking

是浏览器得到要发出这个请求的指令，到请求可以发出的等待时间，一般是代理协商、以及等待可复用的TCP连接释放的时间，不包括DNS查询、建立TCP连接等时间等
Time the request spent waiting before it could be sent. This time is
inclusive of any time spent in proxy negotiation. Additionally, this
time will include when the browser is waiting for an already
established connection to become available for re-use, obeying
Chrome’s maximum six TCP connection per origin rule.

Proxy Negotiation

Time spent negotiating with a proxy server connection.

DNS Lookup

Time spent performing the DNS lookup. Every new domain on a page
requires a full roundtrip to do the DNS lookup.

Initial Connection / Connecting

Time it took to establish a connection, including TCP
handshakes/retries and negotiating a SSL.

SSL

Time spent completing a SSL handshake.

Request Sent / Sending

请求第一个字节发出前到最后一个字节发出后的时间，也就是上传时间
Time spent issuing the network request. Typically a fraction of a
millisecond.

Waiting (TTFB)

请求发出后，到收到响应的第一个字节所花费的时间(Time To First Byte)
Time spent waiting for the initial response, also known as the Time To
First Byte. This time captures the latency of a round trip to the
server in addition to the time spent waiting for the server to deliver
the response.

Content Download / Downloading

收到响应的第一个字节，到接受完最后一个字节的时间，就是下载时间
Time spent receiving the response data.