Optimising for High Latency Environments

Round-trip-time (RTT) is basically a measure of latency—how long did it take to get from one endpoint to another and back again? If you’ve ever pinged www.google.com over in-flight wifi, you’ve measured RTT.

Latency is a key limiting factor on the web: given that most assets fetched by webpages are relatively small (compared to, say, downloading a software update or streaming a movie), we find that most experiences are latency-bound rather than bandwidth-bound.The round trip also measures intermediate steps on that journey such as propagation delay, transmission delay, processing delay, etc. These intermediates fall outside of the scope of this article, but if you’ve ever run a traceroute, you’re on the right lines.

Source: Optimising for High Latency Environments – Harry Roberts – Web Performance Consultant