[ovs-discuss] Controllability of OpenFlow Controllers

[Justin Pettit]

On Jul 3, 2011, at 7:28 PM, Wei-Chih Chen wrote:

> > I am using XCP (Xen Cloud Platform), which includes Open vSwitch.
> > I would like to create virtual bridges of Open vSwitch and attach them to
> > VMs on XCP.
> > However, from the XCP community, they suggest to use OpenFlow controllers to
> > control Open vSwitch instead of using ovs- commands directly because ovs-
> > commands may confuse XAPI.
> What is the difference between managing Open vSwitch by ovs- commands and OpenFlow controllers?
> Can controlling through OpenFlow reach the same functions/purposes/results as through ovs- commands?

The ovs-ofctl commands are mostly just making OpenFlow calls through a command line utility, so no there is really no difference.  The ovs-vsctl and ovs-dpctl commands configure the OVS configuration database and kernel modules, respectively.

The XCP community was likely saying that some elements of configuration should be done through XAPI and others over OpenFlow.  There is some overlap, so doing things like adding ports to a bridge should be done through XAPI instead of directly with ovs-vsctl, so that XAPI doesn't get confused.  Internally, XAPI is making those same ovs-vsctl commands.  Things that have no overlap (because XAPI has no concept of them), such as flow configuration must be done through done through ovs-ofctl or an OpenFlow controller.

Products such as Citrix's DVS (Distributed Virtual Switch) make both XAPI and OpenFlow calls depending on what is being configured.

--Justin