TCP/IP stands for Transmission Control Protocol/Internet Protocol. It
tells computers that are hooked up to the Internet how to package up
messages into packets and how to read packets these packets from other
computers. Ping uses TCP/IP to make its packets.
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"Ping" is a command that sends a feeler out from your computer to another
computer to see if it is turned on and hooked to the same network you are
on. On the Internet there are some ten million computers that you can ping.
Ping is a command you can give, for example, from the Unix, Windows 95 and
Windows NT operating systems. It is part of the Internet Control Message
Protocol (ICMP), which is used to troubleshoot TCP/IP networks. What it does
is tell a remote computer to echo back a ping . So if you get your ping
back, you know that computer is alive. Furthermore, some forms of the ping
command will also tell you how long it takes for a message to go out to that
computer and come back again.
But how does your computer know that the ping it just sent out actually
echoed back from the targeted computer? The datagram is the answer. The ping
sent out is a packet, and like any packet it is wrapped around a datagram.
If the returning ping holds this same datagram, you know it was your ping
that just echoed back.
The basic format of this command is simply:
ping hostname
where "hostname" is the Internet address of the computer you want to check out.
When I give this command from Sun Release 4.1 Unix, I get the answer
"hostname is alive."
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TECHNICAL TIP: Because of the destructive powers of ping, many Internet
Service Providers hide the ping program in their shell accounts where
clueless newbies can't get their hands on it. If your shell account says
"command not found" when you enter the ping command, try:
/usr/etc/ping hostname
The flood ping is a simple example. If your operating system will let you
get away with giving the command:
-> ping -f hostname
it sends out a veritable flood of pings, as fast as your ISP's host
machine can make them. This keeps the host you've targeted so busy echoing
back your pings that it can do little else. It also puts a heavy load on
the network.
Hackers with primitive skill levels will sometimes get together and use
several of their computers at once to simultaneously ping some victim's
Internet host computer. This will generally keep the victim's computer too
busy to do anything else. It may even crash. However, the down side (from
the attackers' viewpoint) is that it keeps the attackers' computers tied
up, too.
NETIQUETTE NOTE: Flood pinging a computer is extremely rude. Get caught
doing this and you will be lucky if the worst that happens is your on-line
service provider closes your account. Do this to a serious hacker and you
may need an identity transplant.
If you should start a flood ping kind of by accident, you can shut it off by
holding down the control key and pressing "c" (control-c).
