[ovs-discuss] What is the role of ovsdb-server and vswitchd?

Ben Pfaff blp at nicira.com
Wed Sep 21 19:58:58 UTC 2011

On Wed, Sep 21, 2011 at 12:51:27PM -0700, Aishwarya wrote:
> I did not quite understand your reply to the first question. what does the
> expression "openvswitch_mod.ko does no flow expiration" mean then? Also, you
> mentioned "userspace deletes flows that fall idle" : you mean vswitchd
> deletes them from the database? 

The kernel doesn't do flow expiration.  ovs-vswitchd tells the kernel
when to delete idle flows.

Flows aren't kept in the database.

> For my use case, what I am doing is
> configuring all required flows when openvswitch starts up, and i require
> them to exist whenever necessary unless the vswitchd process actually dies.
> Is there a way to do this? (I need flows to always exist in vswitchd).


> If this is not possible, how do we know when to re-push the flow rules?

ovs-vswitchd does it.

If you need bridging to work without help from a userspace process,
then you can't use OVS.  Period.

> A side question: Is flow information actually stored in the database, or
> does the database hold only port/bridge information. I do not see any flow
> table in the database document description.

Flows aren't kept in the database.

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