Latency test
Run this once on your normal connection and once through a proxy. The difference between the two is what the proxy costs you — a far more useful number than either reading on its own.
This measures latency, not bandwidth. A throughput test has to push megabytes, which costs you data and us egress, to produce a number that mostly describes the path to our server. Latency and jitter are what you actually feel.
12 requests, first discarded as a warm-up.