The ping program sends out an echo message to a specific address. If the system at that address can be reached and is functioning, it should echo the message back to the sending system. Most ping programs will display information showing how long it took for the message to make the round trip to the destination and back. Ping programs usually allow parameters to be set to vary the program operation. These can include the number of messages to be sent, the number of seconds between packets, the size of the packets, and the pattern of the data transmitted.
Trace route uses the same type of echo message as ping, but it uses the message in a different way.
This parameter tells how many gateways the message can pass through before it is discarded. Each gateway that forwards the message decrements the TTL counter. When the counter reaches Zero the message is discarded. Then a message is sent back to the notify the sender that the TTL on that message was exceeded. The main purpose of TTL is to force a packet to die if it becomes stuck in some sort of circular path, rather than allowing it to cycle endlessly around the Internet.