From owner-freebsd-hackers  Thu Feb  8 20:30:49 1996
Return-Path: owner-hackers
Received: (from root@localhost)
          by freefall.freebsd.org (8.7.3/8.7.3) id UAA27368
          for hackers-outgoing; Thu, 8 Feb 1996 20:30:49 -0800 (PST)
Received: from hp.com (hp.com [15.255.152.4])
          by freefall.freebsd.org (8.7.3/8.7.3) with ESMTP id UAA27361
          for <hackers@freebsd.org>; Thu, 8 Feb 1996 20:30:45 -0800 (PST)
Received: from fakir.india.hp.com by hp.com with ESMTP
	(1.37.109.16/15.5+ECS 3.3) id AA202740220; Thu, 8 Feb 1996 20:30:35 -0800
Received: from localhost by fakir.india.hp.com with SMTP
	(1.37.109.16/15.5+ECS 3.3) id AA168780028; Fri, 9 Feb 1996 09:57:08 +0530
Message-Id: <199602090427.AA168780028@fakir.india.hp.com>
To: hackers@freebsd.org
Subject: tcpdump / kernel dropping packets
Date: Fri, 09 Feb 1996 09:57:06 +0530
From: A JOSEPH KOSHY <koshy@india.hp.com>
Sender: owner-hackers@freebsd.org
Precedence: bulk


Hi,

I was testing my network driver and found that `tcpdump' was experiencing
a very high packet drop rate.  

If I run "tcpdump" without the "-n" option, I find (a) the output on
screen is `bursty' with long periods of silence (b) at the end of the run 
tcpdump reports typically 90% of the packets "dropped by kernel".

If I run "tcpdump" with the "-n" option (no resolving of IP addresses)
it runs with a much smaller loss percentage (but still != 0).

I'd like to know if this behaviour is normal or whether there is something
wrong with my network setup (read: my driver :)).

If normal, what can I do reduce packet loss (eg if FreeBSD is to be the basis
for a network analyser tool?).

I'm running FreeBSD 2.1.0-R on an 8MB P90 IDE system.  The network card is
an HPPCLan+ with "if_ed.c" hacked up to support it.  The driver is otherwise
stable and has been working well for a month now.  I'm trying to tune/improve
performance at the moment.

On this topic, I'd appreciate any pointers on how to measure the effectiveness
of ethernet drivers (short of requiring special purpose hardware to be used).
I'd like to know if I'm dropping packets, sending out too many packets, 
munging the network etc.

Koshy