[ovs-discuss] Multiple OVSs or multiple datapaths with one OVS

Aishwarya aishu85 at gmail.com
Fri Apr 12 22:16:17 UTC 2013


I guess I am a little confused about the concept of datapath. Do you have
any documentation that explains this?

I guess what I really need to know is that whether having 2 bridges with a
single vswitchd daemon will behave the same as having 2 separate bridges
associated with separate vswitchd processes. Is there any difference
between the 2 at all in final behavior. The first one will also simulate
complete independence between the bridges right?


On Fri, Apr 12, 2013 at 3:09 PM, Ben Pfaff <blp at nicira.com> wrote:

> You can use multiple bridges with 1.10 or later, including master, but
> those bridges use a single kernel datapath.
>
> Why do you care whether you use multiple kernel datapaths?
>
> On Fri, Apr 12, 2013 at 02:55:30PM -0700, Aishwarya wrote:
> > I am using the master branch which is OVS 1.10 or higher. So does that
> mean
> > I will not be able to test multiple datapaths with a single ovs-vswitchd
> > daemon with 1.10 and higher? You answered yes to #2 above? Is this true
> > with 1.10 too?
> >
> > Thanks.
> >
> >
> > On Fri, Apr 12, 2013 at 2:43 PM, Ben Pfaff <blp at nicira.com> wrote:
> >
> > > On Fri, Apr 12, 2013 at 02:27:09PM -0700, Aishwarya wrote:
> > > > 1) Running 2 OVS user space daemons on the same machine, and
> creating a
> > > > bridge per OVS process.
> > > >
> > > > 2) Running a single OVS and creating 2 different bridges with the
> same
> > > OVS
> > > > process.
> > > >
> > > > Couple of questions:
> > > > 1. Is (1) even supported?
> > >
> > > It won't work, out of the box, if you use the OVS kernel module.  You
> > > might be able to get it to work with some effort, especially if you
> > > use the userspace datapath only.
> > >
> > > > 2. My use case is that I basically want to be able to test with
> multiple
> > > > datapaths on the same machine. With my experimentation, I feel (2)
> should
> > > > satisfy this. Is that true?
> > >
> > > Yes.
> > >
> > > > 3. Does a single bridge correspond to a single datapath? If not,
> what is
> > > > the real difference between the concept of a bridge and datapath?
> > >
> > > A bridge is an Ethernet or OpenFlow concept.  A datapath is an
> > > implementation detail.  Before OVS 1.10 there was a one-to-one
> > > relationship between bridges and datapaths; in OVS 1.10 and later
> > > there is only one datapath even if there are many bridges.
> > >
>
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