The CTCP ping command and reply has the following command format and functions.
/ctcp TheNick ping
will return client ping (network delay and latency) information about TheNick.
SYSTEM TheNick CTCP: PING reply 2secs SYSTEM AnotherNick CTCP: PING reply 15secs
and other variations, depending on the client.
If TheNick is using a Mibbit Client, the response is always sent.
It needs to be said, that some clients allow this information to be added to, modified in such a way to lie about the ping, or even block it from responding at all.