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<H3><A NAME="s2">2. The <I>Ping</I> tab</A></H3>

<P>
<H3><A NAME="ss2.1">2.1 What is it?</A>
</H3>

<P>The <CODE>
<A HREF="man:ping">ping(8)</A></CODE> command sends ICMP <CODE>ECHO_REQUEST</CODE> packets to network hosts to check for network reachability.
A response from a host (or anything that have an IP address) says that this
host is running at least a TCP/IP network stack and indicates that the network
route to go to this host is opened. The <I>ping</I> tab allows the execution
of the <CODE>ping(8)</CODE> command.
<P>
<IMG SRC="knu-ping.gif">
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<H3><A NAME="ss2.2">2.2 Description</A>
</H3>

<P>Ping uses the ICMP protocol's mandatory <CODE>ECHO_REQUEST</CODE> datagram to
elicit an ICMP <CODE>ECHO_RESPONSE</CODE> from a host or gateway. <CODE>ECHO_REQUEST</CODE> datagrams (``<I>pings</I>'') have an IP and ICMP header, followed by a
<CODE>struct timeval</CODE> and then an arbitrary number of <I>pad</I> bytes used
to fill out the packet.
<P>
<H3><A NAME="ss2.3">2.3 Options</A>
</H3>

<P>
<DL>
<DT><B>Make host name resolution</B><DD><P>Print addresses numerically rather than
symbolically and numerically (this saves a nameserver address-to-name lookup).
</DL>

When using ping for fault isolation, it should first be run on the local host,
to verify that the local network interface is up and running.  Then, hosts and
gateways further and further away should be ``<I>pinged</I>''. Round-trip
times and packet loss statistics are computed.  If duplicate packets are
received, they are not included in the packet loss calculation, although the
round trip time of these packets is used in calculating the
minimum/average/maximum round-trip time numbers.  When the program is
terminated, a brief summary is displayed.
<P><B>This program is intended for use in network testing, measurement and
management.  Because of the load it can impose on the network, it is unwise to
use ping during normal operations or for too long.</B>
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