[ovs-dev] OVN: Floating IP Support - Proposal

Han Zhou zhouhan at gmail.com
Wed Feb 3 19:00:52 UTC 2016


On Mon, Feb 1, 2016 at 10:19 AM, Amitabha Biswas <abiswas at us.ibm.com> wrote:

> Packet Traversal
> ================
>
> Inbound Packet (from external) with Floating IP Processing
> ----------------------------------------------------------
>
> It is assumed that the ARP request for the Floating IP will be broadcast
> to
> all the hosts/hypervisors.
>


Hi Amitabha and Chandra,

Thanks for the proposal! Before going to the details, we need to make the
use case clear.

The assumption here doesn't seem to be realistic to me for most operators.
OVN overlay would most likely to be deployed on top of a IP backplane which
involves multiple L2 domains, which means it is not possible for an ARP to
be broadcast to *all* hypervisors. For relevant HVs to receive the ARP we
may schedule VMs under a given lrouter always to the HVs that are under
same L2 domain, but if we schedule VMs that way, we may lose the benefit of
overlay which is supposed to decouple the IP and location. Nevertheless,
with this limitation, this approach might still be useful if the customer
can sacrifice the IP mobility but want to utilize the metadata provided by
tunneling for east-west traffic.

So could you define the scope and address this concern first? Otherwise we
may wait for the L3 gateway design and propose floating ip support there.
Having a dedicated L2 domain for L3 gateways and making the L3 gateways
horizontally scalable might be a more practical solution, though the
dataplane performance will have to be compromised because of the extra hops.

--
Best regards,
Han



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