[ovs-discuss] flow addition and controller applications

Nicholas Bastin nick.bastin at gmail.com
Sat Jul 30 22:17:14 UTC 2011


On Sat, Jul 30, 2011 at 11:38, Aanova syndhai <asyndhai at gmail.com> wrote:
> I was thinking that since open Vswitch uses 'flow_mode' struct, the
> controller applications should also play around with this struct. The
> controller applications sholuld put some values in "flow_mod *fm" and send
> it back to the switch. The switch then receive this struct as argument of
> add_flow() and add the flow in his flow table.
> Now problem is that most of the controller applications, which I have seen,
> play around with struct "struct ofp_flow_mod *ofm" instead of "struct
> flow_mod".

What exactly do you perceive the benefit to be of sending the
vswitch-specific struct through some out-of-band channel rather than
using the standard openflow messages on the openflow control channel?

One point (among many) of a standard protocol is that controllers
don't have to care about the internal data structures of the switch
implementation - controllers use the standard messages and thus can
talk to a variety of switch implementations.  To the extent that
switches support more than openflow defines, they are free to define
extensions (which has been done in the case of OVS for some things).

--
Nick



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