Thanks for the reply.  My main concern here is the set of default flows 
that must already be running in each OF-only Switch in order for the 
Controller to reach them and program them.

It seems that those default flows have to allow for certain traffic 
to/from all next-hop devices... just as the existing OVS default flows do. 
 But as mentioned, the current OVS default flows seem to be intended for a 
hybrid Switch.  In a true OF-only Switch, it seems that we have to just 
send requests to port LOCAL.  The Switch will respond to requests such as 
ARP... so we get a ARP (response) packet from port LOCAL and we have to 
send it out.  Without any hybrid type intelligence (port/MAC 
associations?), we are left to flood that response out all ports.  That 
seems less than ideal, but perhaps is what has to be done... short of 
something that requires more direct configuration via a UI or some other 
less general set up option.

Thanks.



From:   Nicholas Bastin <[email protected]>
To:     [email protected]
Cc:     "[email protected]" <[email protected]>
Date:   10/30/2015 08:08 PM
Subject:        Re: [ovs-discuss] In-band comm with OF-only Switches



On Thu, Oct 29, 2015 at 8:39 AM, <[email protected]> wrote:
Has a general strategy been established for establishing initial in-band 
communication with OF-only Switches?

Do you mean OF-only OVS instances, or just OF-only switches in general?

For run-of-the-mill OF-only switches the strategy is a fairly simply 
fan-out from the switch(es) your controller is connected to, slowly 
working out to the edge of the network as you install rules in each switch 
along the way to bring control packets back to your controller.

In an environment with no drops or failures it's completely trivial.  If 
you encounter topology changes during the initial process it's a bit more 
complex, but nothing too problematic.  More complexity can come into play 
if you have OF-only devices that can't make a deep enough packet match to 
discriminate control traffic from other traffic you'd like to treat 
differently, but that's life.

--
Nick 
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