What is Latency?
Latency is the amount of time it takes for a computer or application to respond to your request. The less time it takes the better. This is a test where you want to score low and there's a theoretical limit to how low you can go. Zero. Meaning the response was instant. Absolute zero is impossible on this test.
What is TCP?
Transmission Control Protocol or TCP is how you're able to see this page right now. The vast majority of your internet communication traverses this reliable, ordered and error-checked delivery of a stream of bytes.
TestMy.net TCP Ping Tool
a.k.a. TestMy Latency is not the average ICMP ping you get from your command line. TestMy Latency runs on the Transmission Control Protocol (TCP) (layer 4 - transport) where as normal ping runs on ICMP (layer 3 - network). ICMP is not used to exchange data between systems and has no way of interacting or detecting issues with the layers above it (layers 4 through 7). Your average command line ping simply can't give a full picture of what's happening on layer 4. TestMy Latency is different and tests at the transport layer.
“TCP Segment drops manifest as large increases in delay”
Read this latency test case study posted at stanford.edu on the difference between ICMP ping and TCP ping.
TL;DR TCP has more speed bumps
TestMy Latency is more sensitive than your typical ICMP ping for real connection issues. But both are complimentary to each other. ICMP will show you the best case, TestMy Latency (using TCP) isn't as forgiving. Even running this latency test on great computers with great networks shows that TCP isn't perfect. Don't expect a perfect score. But better computers on better networks always fair much better. Exactly what we like to test here. You can ping the servers from your command line at the same time you're testing to get a comparison. Because there is less to go wrong at the layer ping runs on you can expect a lower result from your command line. Think of it this way, TestMy Latency tests beyond normal ping so there are more variables that can affect the result. Equals higher result.
Test using TestMy Latency on your own network. Host any http server, put this file under the folder /b/img/ then call TestMy Latency with the following URL: https://testmy.net/latency?internal=1&addr=[server-address] (e.g. https://testmy.net/latency?internal=1&addr=192.168.1.199) . This tool was first developed running on LAN to eliminate variables. It may be just as useful and helpful validation for your own testing to try a LAN test yourself.
Try different domains. A large majority of popular domains already work with TestMy Latency. Use this syntax https://testmy.net/latency?addr=[domain.name] (e.g. https://testmy.net/latency?addr=youtube.com or https://testmy.net/latency?addr=twitch.com, some addresses will need manual webmaster input contact.)
The Future of the Internet is low latency
Lower latency is ultra important, not just your transfer speed. This tool will provide you with a way to test and compare your latency.
* Note: Read into the newer 4 Layer Internet Model which puts ICMP on layer 2 and TCP on layer 3.
* Also see Don’t use ping [ICMP] for accurate delay measurements by Olivier Bonaventure author of Computer Networking : Principles, Protocols and Practice