[ovs-discuss] Overlapping rules with identical actions

Bithika Khargharia bithika at gmail.com
Wed Sep 5 20:15:25 UTC 2012


Its clear now. Thanks Ben!

On Wed, Sep 5, 2012 at 12:55 PM, Ben Pfaff <blp at nicira.com> wrote:

> On Wed, Sep 05, 2012 at 12:37:27PM -0400, Bithika Khargharia wrote:
> > On Wed, Sep 5, 2012 at 12:17 PM, Ben Pfaff <blp at nicira.com> wrote:
> >
> > > On Wed, Sep 05, 2012 at 12:16:59PM -0400, Bithika Khargharia wrote:
> > > > Thank you Ben.
> > > >
> > > > I am trying to figure out what happens in the following scenario.
> > > >
> > > > OVERLAP flag is not set. Rule 1 has been installed that has an idle
> > > timeout
> > > > value. Before Rule 1 has expired, an overlapping Rule 2 (same
> priority,
> > > > same idle timeout) came in.
> > >
> > > Overlapping or identical?
> >
> >
> > Sorry looks like I was not clear on the definitions. I thought
> overlapping
> > and identical are the same.
>
> No.
>
> Here is an example of overlapping rules:
>
>         - Rule 1, with priority 1234, matches all IP packets.
>
>         - Rule 2, with priority 1234, matches all TCP packets.
>
> because all TCP packets are also IP packets.
>
> > Consider this example. These are identical then?
>
> Your rules are identical.
>
> > So, if Controller sent RULE 2 before RULE 1 expired, RULE 2 will
> > replace RULE 1?
>
> Yes.
>
> > *RULE 1:* ADD
> >
> priority=0,in_port=21,vlan_tci=0x0000,dl_src=00:24:e8:cc:f9:ca,dl_dst=00:14:d1:1b:94:21
> > cookie:0x20000000000000 idle:5 flags:0x1 actions=output:23
> >
> >
> >  *RULE 2:* ADD
> >
> priority=0,in_port=21,vlan_tci=0x0000,dl_src=00:24:e8:cc:f9:ca,dl_dst=00:14:d1:1b:94:21
> > cookie:0x20000000000000 idle:5 flags:0x1 actions=output:23
> >
> >
> > > If they are identical, rule 2 replaces rule
> > > 1.  If they merely overlap, both will be present, but which one
> > > actually processes matching packets is unpredictable.
> > >
>
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