"discuss" <discuss-boun...@openvswitch.org> wrote on 06/17/2016 05:24:19 PM:
> From: Cathy Zhang <cathy.h.zh...@huawei.com> > To: Na Zhu <na...@cn.ibm.com> > Cc: Srilatha Tangirala/San Francisco/IBM@IBMUS, "OpenStack > Development Mailing List \(not for usage questions\)" <openstack- > d...@lists.openstack.org>, John McDowall > <jmcdow...@paloaltonetworks.com>, discuss <discuss@openvswitch.org> > Date: 06/17/2016 05:25 PM > Subject: Re: [ovs-discuss] [openstack-dev] [OVN] [networking-ovn] > [networking-sfc] SFC andOVN > Sent by: "discuss" <discuss-boun...@openvswitch.org> > > Hi Juno, > > Here is an example. > > Src SF DST > | | | | > 1 2 3 4 > OVS1==========OVS2==========OVS3 > > For bump-in-the-wire SF type, since what it does is just to pass the > packet from its ingress port to egress port, broadcast and multicast > packets will form a loop on port 2 and 3. > This problem is not specific to SFC though. A simple way to solve > this is to put a bump-in-the-wire SF’s port 2 and port 3 in > different subnets. For L3 SF, this is not an issue. The above is a good reason for following OVN's pipeline logic and not punting a packet to an output port in the ingress pipeline (as I first expressed concerns about in [1]). There is a loopback check in table 34 (between the ingress and egress pipelines) that we can look at using to break the loops - program it to drop broadcast/multicast traffic going between ports 2 and 3 and the loop is broken. Ryan [1] http://openvswitch.org/pipermail/discuss/2016-May/021419.html
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