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<div>Ryan,</div>
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<div>Agree with your description of the problem. The only thing I would add is that in the case of bi-directional chains the return flows need to go through the same VNF(Port-pair).</div>
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<div>Regards</div>
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<div>John</div>
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<span style="font-weight:bold">From: </span>Ryan Moats <<a href="mailto:rmoats@us.ibm.com">rmoats@us.ibm.com</a>><br>
<span style="font-weight:bold">Date: </span>Wednesday, May 25, 2016 at 9:29 PM<br>
<span style="font-weight:bold">To: </span>Ben Pfaff <<a href="mailto:blp@ovn.org">blp@ovn.org</a>><br>
<span style="font-weight:bold">Cc: </span>"<a href="mailto:discuss@openvswitch.org">discuss@openvswitch.org</a>" <<a href="mailto:discuss@openvswitch.org">discuss@openvswitch.org</a>>, John McDowall <<a href="mailto:jmcdowall@paloaltonetworks.com">jmcdowall@paloaltonetworks.com</a>>,
Justin Pettit <<a href="mailto:jpettit@ovn.org">jpettit@ovn.org</a>>, OpenStack Development Mailing List <<a href="mailto:openstack-dev@lists.openstack.org">openstack-dev@lists.openstack.org</a>>, Russell Bryant <<a href="mailto:russell@ovn.org">russell@ovn.org</a>><br>
<span style="font-weight:bold">Subject: </span>Re: [OVN] [networking-ovn] [networking-sfc] SFC and OVN<br>
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<p><tt>Ben Pfaff <<a href="mailto:blp@ovn.org">blp@ovn.org</a>> wrote on 05/25/2016 07:44:43 PM:<br>
<br>
> From: Ben Pfaff <<a href="mailto:blp@ovn.org">blp@ovn.org</a>></tt><br>
<tt>> To: Ryan Moats/Omaha/IBM@IBMUS</tt><br>
<tt>> Cc: John McDowall <<a href="mailto:jmcdowall@paloaltonetworks.com">jmcdowall@paloaltonetworks.com</a>>,
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> "<a href="mailto:discuss@openvswitch.org">discuss@openvswitch.org</a>" <<a href="mailto:discuss@openvswitch.org">discuss@openvswitch.org</a>>, OpenStack
<br>
> Development Mailing List <<a href="mailto:openstack-dev@lists.openstack.org">openstack-dev@lists.openstack.org</a>>, Justin<br>
> Pettit <<a href="mailto:jpettit@ovn.org">jpettit@ovn.org</a>>, Russell Bryant <<a href="mailto:russell@ovn.org">russell@ovn.org</a>></tt><br>
<tt>> Date: 05/25/2016 07:44 PM</tt><br>
<tt>> Subject: Re: [OVN] [networking-ovn] [networking-sfc] SFC and OVN</tt><br>
<tt>> <br>
> On Wed, May 25, 2016 at 09:27:31AM -0500, Ryan Moats wrote:<br>
> > As I understand it, Table 0 identifies the logical port and logical<br>
> > flow. I'm worried that this means we'll end up with separate bucket<br>
> > rules for each ingress port of the port pairs that make up a port<br>
> > group, leading to a cardinality product in the number of rules.<br>
> > I'm trying to think of a way where Table 0 could identify the packet<br>
> > as being part of a particular port group, and then I'd only need one<br>
> > set of bucket rules to figure out the egress side. However, the<br>
> > amount of free metadata space is limited and so before we go down<br>
> > this path, I'm going to pull Justin, Ben and Russell in to see if<br>
> > they buy into this idea or if they can think of an alternative.<br>
> <br>
> I've barely been following the discussion, so a recap of the question<br>
> here would help a lot.<br>
> <br>
</tt><br>
<tt>Sure (and John gets to correct me where I'm wrong) - the SFC proposal</tt><br>
<tt>is to carry a chain as a ordered set of port groups, where each group </tt><br>
<tt>consists of multiple port pairs. Each port pair consists of an ingress</tt><br>
<tt>port and an egress port, so that traffic is load balanced between</tt><br>
<tt>the ingress ports of a group. Traffic from the egress port of a group </tt><br>
<tt>is sent to the ingress port of the next group (ingress and egress here</tt><br>
<tt>are from the point of view of the thing getting the traffic).</tt><br>
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<tt>I was suggesting to John that from the view of the switch, this would</tt><br>
<tt>be reversed in the openvswitch rules - the proposed CHAINING stage</tt><br>
<tt>in the ingress pipeline would apply the classifier for traffic entering</tt><br>
<tt>a chain and identify traffic coming from an egress SFC port in the</tt><br>
<tt>midst of a chain. The egress pipeline would identify the next ingress SFC</tt><br>
<tt>port that gets the traffic or the final destination for traffic exiting</tt><br>
<tt>the chain.</tt><br>
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<tt>Further, I pointed him at the select group for how traffic could be</tt><br>
<tt>load balanced between the different ports that are contained in a port</tt><br>
<tt>group, but that I was worried that I'd need a cartesian product of rules</tt><br>
<tt>in the egress chain stage. Having thought about this some more, I'm</tt><br>
<tt>realizing that I'm confused and the number of rules should not be that</tt><br>
<tt>bad:</tt><br>
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<tt>- Table 0 will identify the logical port the traffic comes from</tt><br>
<tt>- The CHAINING stage of the ingress pipeline can map that logical</tt><br>
<tt> port information to the port group the port is part of.</tt><br>
<tt>- The CHAINING stage of the egress pipeline would use that port</tt><br>
<tt> group information to select the next logical port via a select group.</tt><br>
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<tt>I believe this requires a total number of rules in the CHAINING stages</tt><br>
<tt>of the order of the number of ports in the service chain.</tt><br>
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<tt>The above is predicated on carrying the port group information from</tt><br>
<tt>the ingress pipeline to the egress pipeline in metadata, so I would</tt><br>
<tt>be looking to you for ideas on where this data could be carried, since</tt><br>
<tt>I know that we don't have infinite space for said metadata...</tt><br>
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<tt>Ryan</tt><br>
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