[ovs-dev] OVN architecture

Ben Pfaff blp at nicira.com
Mon Jan 19 17:19:33 UTC 2015


On Mon, Jan 19, 2015 at 02:04:42PM +0100, Thomas Graf wrote:
> On 01/16/15 at 04:28pm, Ben Pfaff wrote:
> > We have not yet contemplated that, but it could be possible.
> > 
> > In my opinion, OVS is not releasing often enough in any case.  I think
> > that 3 or 4 releases a year is about right (but that's off the cuff, not
> > some kind of official policy or anything).
> 
> Agreed. I would expect that OVN might lead to more frequent releases
> of OVS with a more "stable at all times attitude" as OVN will depend on
> specific OVS features. Or we provide feature negotiation aside of versioning.
> I guess this will come naturally either way though.

I really prefer feature negotiation in any case, because it means that
OVN can work with OVS that has custom version numbers or backports of
individual features.

The one feature that I'm most interested in using from OVN, though, is
one that will only be in OVS 2.4: conjunctive match.  If you look at the
matching language that I want to implement in OVN, it can be naturally
expressed with conjunctive match and it's much more difficult to
implement efficiently and in full generality without it.  That probably
means that for older versions we'd have to compute full cross-products,
which is OK for simpler kinds of conjunctive match.  I think that means
that, if OVN is used with OVS<2.4, then OVN users would have to restrict
the ACLs they add to ones that can be efficiently implemented with
cross-products.  Maybe that's OK; I haven't thought it through fully.



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