chrome reques 分析

2017051009:39

chrome

Queued at 0

Started at 11.91ms

瀏覽器得到要發出這個請求的指令，到請求可以發出的等待時間，
一般是代理協商、以及等待可複用的TCP連接釋放的時間
不包括DNS查詢、建立TCP連接等時間等

Queueing 11.19ms

Stalled 5.27ms

DNS Lookup 132.47ms
域名解析花費的時間 (132.47ms 太高了，大致觀察大部分略有的網站多在 20ms以下) **文後查詢工具

Initaial connection 61.54ms

SSL 37.00ms

Request sent 0.22ms
瀏覽器發送本次請求的第一個bit，到最後一個bit。

Waiting (TTFB) 161.05ms
發出請求後(request 發出結束)，到收到回應第一個 byte 所花費的時間 (Time To First Byte)

Content Download 6.79ms
下載完整網頁(或圖片) 的時間

https://developers.google.com/web/tools/chrome-devtools/network-performance/reference#timing

Timing breakdown phases explained

Here's more information about each of the phases you may see in the Timing tab:

Queueing. The browser queues requests when:
- There are higher priority requests.
- There are already six TCP connections open for this origin, which is the limit. Applies to HTTP/1.0 and HTTP/1.1 only.
- The browser is briefly allocating space in the disk cache
Stalled. The request could be stalled for any of the reasons described in Queueing.
DNS Lookup. The browser is resolving the request's IP address.
Proxy negotiation. The browser is negotiating the request with a proxy server.
Request sent. The request is being sent.
ServiceWorker Preparation. The browser is starting up the service worker.
Request to ServiceWorker. The request is being sent to the service worker.
Waiting (TTFB). The browser is waiting for the first byte of a response. TTFB stands for Time To First Byte. This timing includes 1 round trip of latency and the time the server took to prepare the response.
Content Download. The browser is receiving the response.
Receiving Push. The browser is receiving data for this response via HTTP/2 Server Push.
Reading Push. The browser is reading the local data previously receieved.

firefox 54

被阻擋 (Blocking)：
每個瀏覽器有並發連接數量的上限（例如 Firefox 對每個 host 限制6個連接）
如果當前建立的連接數已經超過上限，那麼其餘該請求會被阻塞，等待新的可以用的連接。

-->這裡有個問題，即使只有一個 Request (只瀏覽一張圖片) 有時也會有【Blocking 時間】 why ??

DNS解析 (DNS Lookup)：
不解釋了

連接 (Connecting)：
三次握手建立TCP鏈接的時間。如果是HTTPS的話，再加上SSL鏈接的時間

傳送 (Sending)：
瀏覽器發送本次請求的第一個bit，到最後一個bit。

等待 (Waiting / TTFB)：
從發送結束起，到收到server傳回的第一個bit。

接收 (Receiving)：
從收到server 返回的第一個bit，收到到最後一個bit 的時間。