Date: Fri, 09 Feb 1996 09:57:06 +0530 From: A JOSEPH KOSHY <koshy@india.hp.com> To: hackers@freebsd.org Subject: tcpdump / kernel dropping packets Message-ID: <199602090427.AA168780028@fakir.india.hp.com>
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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
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