Re: questions on -B, performance, mbufs, and

["Sanjay Sundaresan" <sunda1 () usc edu>]

What is the meaning of dropped by interface ?
Dropped by kernel means packets dropped due to lack of memory at the kernel
in the same way what does interface drop signifies ?

-----Original Message-----
From: tcpdump-workers-owner () lists tcpdump org
[mailto:tcpdump-workers-owner () lists tcpdump org] On Behalf Of Rick Jones
Sent: Wednesday, September 28, 2011 9:42 AM
To: tcpdump-workers () lists tcpdump org
Subject: Re: [tcpdump-workers] questions on -B, performance, mbufs, and

On 09/27/2011 07:32 PM, Jon Schipp wrote:
> Hello Guy,
>
> I'm now doing testing with tcpdump on an Ubuntu machine.
>
> One difference I noticed was that in addition to "dropped by kernel", 
> tcpdump on Ubuntu also reports "dropped by interface".
>
> Is this specific to Linux, because I haven't experienced this on 
> FreeBSD? Is this Ubuntu distro addendum or has this been added by the
tcpdump team.
> Where do the numbers come from for the "dropped by interface", you've 
> already explained the "dropped by kernel"
> I was just wondering how this differs. Would this be the number 
> reported by ifconfig?

If, as the name suggests, those are drops reported by the NIC, presumably
the value you see being emitted by tcpdump would track rather closely with
the stats reported for the interface via ethtool -S <interface>

rick jones
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