[ovs-dev] another provider network idea (was: [RFC] ovn: physical network integraiton (WIP))

[Ben Pfaff]

I think that the various issues with trying to treat a provider network
as a logical network are going to difficult to resolve.  I think that
they reflect a conceptual difference between OVN logical networks and
provider networks.  OVN knows the hosts on a logical network and where
they reside, but it doesn't know that for a provider network, and can't
do anything related to specific hosts except in the pathological case
where they reside on the same hypervisor.  Broadcast may be a problem,
but so is a simple output to any port: it's impossible unless the source
and destination ports are on the same hypervisor.  So my thought is that
modeling a provider network as an OVN logical network is unlikely to be
fruitful (unless we change the OVN logical network model significantly).

Here's an a strawman alternative.  Instead of representing a provider
network as a single logical network, represent it as a collection of
logical networks, one for each connected port.  Each of these logical
networks has only two ports, the VM's port plus a physical port on the
hypervisor where the VM resides (or more likely a patch port to the
bridge that contains the physical port; the other end of the patch port
can be an access port if it's a VLAN provider network).  It seems to me
that this models the situation more naturally.

Thoughts?

Thanks,

Ben.