Devtools network performance timing

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 received.

Blocked	Time spent in a queue waiting for a network connection.
DNS resolution	Time taken to resolve a host name.
Connecting	Time taken to create a TCP connection.
Sending	Time taken to send the HTTP request to the server.
Waiting	Waiting for a response from the server.
Receiving	Time taken to read the entire response from the server (or cache).