EC2 latency, and latency in general

Question

Webkit is telling me that a page's load time, the page being served via EC2, is 651ms. 502ms of that was "latency", and 149 was "download". What could the 502ms of latency be? Is that the time it takes to render the page on EC2 and send it back to the client?

Answer 1

Typically time required for a web request consist of

  1. DNS lookup 
  2. TCP handshake time + request(two round trip for fresh connection)
  3. Time to generate the page (Server side time).
  4. Download time.

1+2+3 is latency. 

Since ping time in your case has very high variance it can be due to network either on your side or ec2 side or in-between. Can you ping other ec2 boxes/ or other boxes from your home/office and try to isolate the issue is its on which side.

Just add those pings to the question let me see if I can help.