On Tue, Dec 1, 2015 at 10:34 AM, Ben Pfaff <b...@ovn.org> wrote: > On Mon, Nov 30, 2015 at 11:02:29PM -0800, Han Zhou wrote: >> Hi Ben, >> >> On Tue, Nov 24, 2015 at 6:12 PM, Ben Pfaff <b...@ovn.org> wrote: >> > I'm having trouble figuring out which one we should do. The reason that >> > I'm torn between choices is because of layering. I like the way that, >> > currently, the switch and router datapaths are (almost) independent of >> > each other, in the sense that they don't have to know anything about >> > what they're attached to. However, we've already got one violation of >> > this principle: logical routers statically discover MAC-IP bindings on >> > their attached switches. For now, that's pretty much necessary, since >> > logical routers don't support ARP yet (I'm fixing that, don't worry), >> >> By "support ARP" do you mean logical routers broadcast ARP requests to >> lswitch ports and then process ARP replies (from the owner of the IP) >> to get IP-MAC bindings? >> In such case even if this kind of dynamic ARP is supported, it would >> still be valuable to continue supporting the static MAC-IP bindings, >> which is the major scenario of CMS such as openstack, where IP-MAC >> binding is known during VM provisioning (and similar use case for >> containers). I think dynamic ARP introduce higher costs, and requires >> periodical refreshing, so it is better to be triggered only when >> static binding is not available. >> >> Or do you mean any other kind of ARP support? > > I do mean what you thought. ARP is more or less necessary because > IP-MAC bindings aren't always statically available, especially when > physical infrastructure is brought into a logical network. > > I don't think we'd ever discontinue the static MAP-IP bindings. They > are a valuable optimization. If we decide that strict layering is > important, then they could be implemented by having logical routers send > out ARP requests and then having the logical switches send the ARP > replies. The ARP would never travel over a physical network in this > case.
This clarified my confusion. While this option implements strict layering, it still introduces unnecessary stages (ARP request/reply) for static MAC-IP bindings because in that case ARP should be considered as already resolved in the beginning. > > However, as we continue our discussion here, I'm leaning more and more > against worrying about layering issues, at least in the current context. > I have the same view at this point. Please let me know if I should continue the patch to remove the redundant MAC field. -- Best regards, Han _______________________________________________ dev mailing list dev@openvswitch.org http://openvswitch.org/mailman/listinfo/dev
