[ovs-dev] [PATCH RFC ovn] Add VXLAN support for non-VTEP datapath bindings

Numan Siddique numans at ovn.org
Tue Mar 24 08:07:32 UTC 2020


On Tue, Mar 24, 2020 at 5:17 AM Ben Pfaff <blp at ovn.org> wrote:
>
> On Mon, Mar 23, 2020 at 06:39:14PM -0400, Ihar Hrachyshka wrote:
> > First, some questions as to implementation (or feasibility) of several
> > todo items in my list for the patch.
> >
> > 1) I initially thought that, because VXLAN would have limited space
> > for both networks and ports in its VNI, the encap type would not be
> > able to support as many of both as Geneve / STT, and so we would need
> > to enforce the limit programmatically somehow. But in OVN context, is
> > it even doable? North DB resources may be created before any chassis
> > are registered; once a chassis that is VXLAN only joins, it's too late
> > to forbid the spilling resources from existence (though it may be a
> > good time to detect this condition and perhaps fail to register the
> > chassis / configure flow tables). How do we want to handle this case?
> > Do we fail to start VXLAN configured ovn-controller when too many
> > networks / ports per network created? Do we forbid creating too many
> > resources when a chassis is registered that is VXLAN only? Both? Or do
> > we leave it up to the deployment / CMS to control the chassis / north
> > DB configuration?
> >
> > 2) Similar to the issue above, I originally planned to forbid using
> > ACLs relying on ingress port when a VXLAN chassis is involved (because
> > the VNI won't carry the information). I believe the approach should be
> > similar to how we choose to handle the issue with the maximum number
> > of resources, described above.
> >
> > I am new to OVN so maybe there are existing examples for such
> > situations already that I could get inspiration from. Let me know what
> > you think.
>
> I don't have good solutions for the above resource limit problems.  We
> designed OVN so that this kind of resource limit wouldn't be a problem
> in practice, so we didn't think through what would happen if the limits
> suddenly became more stringent.
>
> I think that it falls upon the CMS by default.

I agree. I think It should be handled by CMS.

Thanks
Numan

>
> > > > Assuming we pick a term to use to describe these out-of-cluster
> > > > switches, we should consider the impact of the rename. Renaming
> > > > internal symbols / functions is trivial. But "vtep" is used in OVN
> > > > schema (for example, for port binding 'type' attribute). Do we want to
> > > > rename those too? If so, what considerations should we apply when
> > > > doing it? Any guidance as to maintaining backwards compatibility?
> > > >
> > > > Also, is such a rename something that should happen at the same moment
> > > > when we add support for VXLAN for in-cluster communication? Or should
> > > > it be a separate work item? (If so, do we expect it to land before or
> > > > after the core VXLAN implementation lands?)
> > >
> > > We can't (or at any rate should not) change the terms in the schema, but
> > > we can change other places and point out to people in a few places that
> > > a "ramp switch" is sometimes, confusingly, called a "vtep".
> >
> > Gotcha. Any preferences as to whether to consider it a preparatory
> > work item; a follow-up; or a part of the VXLAN implementation? (I lean
> > towards handling the ramp term introduction as an independent
> > preparatory step.)
>
> I sent out a patch for people to look at.
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