Ethernet, Wi-Fi and a phone hotspot: it is jitter that hurts, not speed

[Shadow Trader]

A speed test result is nearly irrelevant for trading. An order is a few hundred bytes. Whether the line can pull down 300 Mbps or 30 Mbps makes no difference to something that small.

What matters is how consistent the delay is. Jitter is the variation from one packet to the next. A connection that takes 15 ms every single time is far better for execution than one that averages 10 ms but sometimes takes 80 and sometimes 8.

Wi-Fi tends to be the jittery one. It shares airtime with neighbours, microwaves, and every other device in the house, and it retransmits lost packets, which looks like random spikes. A wired Ethernet cable removes most of that variation, which is why it is the usual recommendation.

A mobile hotspot adds another layer. Signal strength changes, the carrier may route traffic through different gateways, and some networks put many users behind shared address translation. Average speed may look great while the delay swings unpredictably. It works fine as a backup, but a poor primary link for tight entries.

A simple way to see the difference is to run a continuous ping to the broker or a stable server for a few minutes on each connection and look at the spread of times, not just the average.

Has anyone measured jitter on their own connections, and how much did Wi-Fi really differ from a cable in practice?