Two Different Numbers
People say a connection is fast, but speed has two parts. Bandwidth is how much data can flow per second, like the width of a pipe. Latency is how long one bit takes to travel from end to end, like the length of the pipe.
Why They Differ
A link can be wide yet still feel slow.
- Bandwidth caps bulk transfer such as a large download.
- Latency caps how quickly a small request gets a reply.
- A web page often waits on many small requests, so latency dominates the feel.
Adding more bandwidth speeds a movie download but barely helps a chatty page that sends tiny messages back and forth.
The Physical Floor
Latency has a hard floor set by distance and the speed of light in fiber, which is roughly two thirds of the speed in vacuum. A request across a continent cannot beat that floor no matter how wide the pipe.
Key idea
Bandwidth is data per second and latency is travel time per bit, and chatty workloads are limited by latency while bulk transfers are limited by bandwidth.