[Netem] duplicate packets

Stephen Hemminger shemminger at osdl.org
Tue Feb 21 13:21:59 PST 2006


On Tue, 21 Feb 2006 21:25:02 +0100
srg <srgqwerty at gmail.com> wrote:

> Hello:
> 
> Thanks for reading this.
> I am running linux2.6 kernel and have a bridge in interfaces eth1 and eth2.
> brctl add b
> brctl addif b eth1
> brctl addif b eth2
> ifconfig b up
> 
> At this point the bridge is ok and running.
> I need that the traffic going through the bridge is delayed, so:
> 
> # tc qdisc add dev eth1 root netem delay 100ms
> # tc qdisc add dev eth2 root netem delay 100ms
> 
> After that, tc qdisc show, outputs the following about eth1 and eth2 interfaces (tc qdisc show):
> qdisc netem 8001: dev eth1 limit 1000 delay 100.0ms duplicate 93.8788%
> qdisc netem 8002: dev eth2 limit 1000 delay 100.0ms duplicate 93.8788%
> 
> But, looking at the traffic with a sniffer, it seems that NO packet duplication occurs at all.
> What is the meaning of "duplicate 93.8788%" ?
> How can I configure this value to "0%" ?
> 
> Thanks and best regards

You may have a mismatch between the kernel and the iproute2 utilities.
The version of tc may not match the kernel.  Try downloading and rebuilding
iproute2. Also, make sure which tc command you are picking up in the
command path.
	# which tc
Redhat puts tc in /sbin and others use /usr/sbin.  If you do make install
in iproute2 it puts it in /usr/sbin.



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