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.
Time spent negotiating with a proxy server connection.
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.
Time spent completing a SSL handshake.
Request Sent / Sending
Time spent issuing the network request. Typically a fraction of a millisecond.
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.