Hi, I attempted to send a file from host A to B and capture the packet loss using OpenvSwitch. I connected host A and B to an OpenvSwitch VM separately and connect the two OpenvSwitch VMs. The topology looks like this:
A -- OVS_A -- OVS_B -- B On each OpenvSwitch VM, I added two very simple flows using the commands below: ovs-ofctl add-flow br0 in_port=1,actions=output:2 ovs-ofctl add-flow br0 in_port=2,actions=output:1 Then I sent a 10GB file between A and B and compared the packet counts of the egress flow on the sending switch and the ingress flow on the receiving switch. I found that the packet count on the receiving switch is much larger than the count on the sending switch, indicating more packets are received than being sent! I tried to match more specific flows, e.g. a TCP flow from IP A.A.A.A to B.B.B.B on port C and got the same result. Is there anything wrong with my settings? Or this is a known bug in OpenvSwitch? Any ideas? BTW, is there any other way to passively capture packet loss rate? Meaning measuring the loss rate w/o introducing any intrusive test flows, but simply use statistics available on the sending/receiving ends or switches. Thanks, Fan
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