Latency is the time it takes for data to get from your computer to the game server. This is usually measured in milliseconds (ms), there are 1000 milliseconds in one second. The response time is the time it takes for data and the corresponding event to get to the game server and then back to your computer. The response time is generally about 2x the latency. This means that if you are improving your latency by 250ms, you are improving your game response time by about half a second. If you improve your latency by 500ms, you are improving your game response time by a full second. This is an estimate based on real game situations where you interacting and responding to other players (who also have their own latency).
This makes a huge difference, especially in "fast twitch" situations where you need to interrupt a spell, deliver a killing blow, get off a heal, attack someone before they hide around a pillar, etc, etc, etc. You can see your game latency real-time by hovering your mouse over the little computer icon while you play WOW.
WTFast will reduce your latency, reduce disconnections, reduce lag spikes, and improve performance in situations with lots of players like big raids.
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