[ovs-discuss] Questions about OVS flow table

Justin Pettit jpettit at nicira.com
Sun Apr 28 23:33:29 UTC 2013

On Apr 28, 2013, at 3:42 AM, david zhang <ccie20781 at gmail.com> wrote:

> Recently, we have built a script to monitor the size of OVS flow table. We found the number of flow entries in flow table jumps up and down between 1500 and 7000 in one OVS. So we want to understand more about the flow table.
> Below is my first 2 questions. Could you please help? Thank you very much!
> (1) How the flow table is built initially if we have not manually add any entry in OVSflow table entry;
> (According to my understanding, the new flow entry will be added/created when the first packet of the flow is coming in; is it correct?)

I assume your question is about the kernel flow table, as you'd see in "ovs-dpctl dump-flows".  If so, you are correct.

> (2) What the flow table entry update and timeout mechanism is? How I know individual flow entry's timeout?

ovs-vswitchd determines how long the flow should stay in the kernel flow table.  By default, it expires a flow after five seconds of inactivity.  It can be more aggressive if the flow table becomes large.


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