Re: ICMP As A Diagnostic Tool?


Mike Muuss (mike@BRL.ARPA)
Tue, 7 Apr 87 3:24:27 EDT


BRL uses the "ping" program, which transmits ICMP Echo Request packets
with the data field set to a process ID, a sequence number, and
a struct timeval (time in seconds and microseconds), plus patterns
to pad out any extra length (a command-line parameter).

[The BRL ping program is now provided as /etc/ping in 4.3 BSD UNIX].

We use this tool for network troubleshooting *extensively*.
Many Lab managers even know how to run PING, so that they can
get more information about why connections to far-away hosts
may be working poorly.

We also have a tool (PINGPOLL) that we use (within the campus net only)
to monitor round-trip-times and packet loss, as well as a very simple
ICMP-based routing daemon (ROUTER).

ICMP is invaluable -- it provides a level of visibility of activity
at the link level that is very helpful.

Oh yes, another good use to to watch the effects of varying packet
size. Good for finding IP reassembly bugs (in days gone by), and
various interesting performance problems (back-to-back etherpackets, etc).

The "ping -f" (aka FLOODPING) option is very good for stress-testing
a particular network, gateway, host, whatever. As the name suggests,
it releases ICMP echo request packets as fast as it can.

Another version of PING that we have uses the IP option "record route",
which is useful to see where the packets are traveling.

Very useful, and amusing to watch.

        Best,
         -Mike



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