User Datagram Protocol (
UDP) also known as
Universal Datagram Protocol.
Players in the United Kingdom aren't going to notice a difference because the server host that Graal uses is in the United Kingdom.
Although, if you live in the United States, you're going to notice a major difference if you have it checked or unchecked.
Making this message in short term understanding.
Basically having it
unchecked you're going to have a better connection with the server. If the server was to ever lag out, you would notice some people are frozen and others aren't. The ones that aren't frozen, have UDP
unchecked.
This means you're relaying on the server to be your connection for everyone else. If the server lags out, you're lagged out along with it.
I recommend, if you can, have UDP
unchecked; it really makes Graal a lot better and you notice more players will be smoother.
If you have Dial-up, you should be able to enable it, regardless.
Broadband or Cable connections: You may have to port forward or enable 'DMZ' through your router settings.