TRY: Measuring website latency
The speed of light is 300,000,000 meters per second. Every millisecond, light travels 300,000 meters = 300km = 186 miles. Two computers connected over the internet experience this latency, accumulating 1 millisecond for every 186 miles in packet travel. This is a limitation of physics. It is immutable.
Latency should be accounted for when choosing an internet asset's location. VPN servers are fastest when the server is nearest your location. Web servers also have this advantage, although a web page's content can benefit from CMS distribution specifically for this reason. Cms lowers travel latency caused by the 186 mile rule by storing, or caching, web content on a caching server nearest its users.
Critical sites, such as a business retail website, should consider travel latency in both operating and backup situations. For example, a frontend server operating in Miami expecting a failover server in Seattle experiences 18 milliseconds of travel latency. This means that a TCP connection - a TCP connection requires a three way handshake - alone would add 54ms delay.