All measured indices are relative to the user's point of view, and not for the site owner.
The client downloads the library along with the rest of the website.
Boomerang records performance-related data on the client's side and sends it back to the server.
Here are some key features of "Boomerang":
· Measure a user's bandwidth along with page load time
· Measure perceived performance of content loaded dynamically
· Measure HTTP latency
· Measure DNS latency
· Measure a random sample of users instead of all users
· Collect browser WebTiming information