[mrtg] Packet Loss & latency

Asimina Dimitriadou mina at ccf.auth.gr
Fri Dec 15 13:56:16 MET 2000

Having in mind Jeff Liebermann suggestion for packet loss statistics,
I would like to ask if there is a way to have statistics for packet loss
and latency per interface on a  Cisco Router (7513).

Does anybody know if there is a (shareware) software packet to provide
such services+visualization?

thanks in advance,

Message: 19
   Date: Mon, 4 Dec 2000 18:19:24 -0800
   From: Jeff Liebermann <jeffl at comix.santa-cruz.ca.us>
Subject: Re: Packet Loss from Ping

On Thu, Nov 16, 2000 at 07:04:28PM -0500, cpt2 at daimlerchrysler.com
> Has anyone implemented a graph of this from a Windoze box?  I'd like
to get
> a graph of percent packet loss (as the ping command reports) on my NT
> server and was wondering if there is an existing script for this.

Can I talk you out of this idea?  Accurate packet loss is a
function of how many packets you ping with.  For example, if
you just ping with 3 packets, your choices are 0, 33%, 67%,
and 100%.  If you want 1% resolution, you'll need to ping
with 100 packets every 5 minutes.  If traffic gets high, many
routers simply drop or delay ICMP ping packets to insure the
important stuff gets through.  Using the ping packet loss is
not what I would consider practical or useful.

May I suggest you monitor TCP retransmissions at:
and TCP traffic at:  (in)  (out)
The Retrans are the number of TCP "segments" that have to get
resent usually because of packet loss.  While this does nothing
for ICMP and UDP traffic, it does serve as a good indication
that something is amis in the link.  I use the percentage of
TCP retrans to measure wireless link reliability which can
easily have a packet loss of 50% or more.

For NT ping times, I use the following mess.  Note that this
requires the Windoze 95/98 version of ping.exe which I
renamed to ping95.exe.

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