strider wants to know....

Got this from Wikipedia:

In this sense, ping is conflated with lag – one may "lag out" due to unacceptably high ping. Servers will often disconnect a client if the connection is too bad and it poses a detriment to others' gameplay; or, clients will often mandate disconnection if their ping is too high and they can infer their user is not going to have an enjoyable experience because of network complications. However, this doesn't mean that a high ping causes lag. The high ping is the result of the lag. In theory, there can be more reasons of having a high ping (for example, you are transmitting data over a very, very long distance), but most servers of commercial games are a**ociating a high ping with network lag directly.

The method used by the game programmers to determine ping times will often not use the traditional ICMP echo request and reply packets, but instead piggyback the functionality onto existing game data packets (often using UDP).

Some factors that might affect one's ping include: network protocol engineering, internet connection speed, quality of the internet service provider and the configuration of firewalls. Ping is also affected by geographical locations. For instance if someone is in China playing a server from America, the distance between the two are farther and it takes a longer time for the data to be sent to China. The amount of packet-switching and network hardware in between the two hosts is often more significant. For instance, wireless network interface cards must modulate digital signals into radio signals, which is often more costly than the time it takes an electrical signal to traverse a reasonable span of cable.