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With ML2 plugin and l2-pop mechanism driver, it's possible to locally answer to the ARP request of the VM and avoid ARP broadcasting emulation on overlay which is costly. When this functionality is enabled, the OVS flows logic evolves to [1]. This functionality was introduce in 2.1 OVS branch [2]. A README is added to describe l2-pop mechanism driver and the agents particularities. [1] https://wiki.openstack.org/wiki/Ovs-flow-logic#OVS_flows_logic_with_local_ARP_responder [2] http://git.openvswitch.org/cgi-bin/gitweb.cgi?p=openvswitch;a=commitdiff;h=f6c8a6b163af343c66aea54953553d84863835f7 DocImpact: New OVS agent flag 'arp_responder' set to false by default Closes-Bug: #1237427 Change-Id: Ic28610faf2df6566d8d876fcd7aed333647970e2
41 lines
1.9 KiB
Plaintext
41 lines
1.9 KiB
Plaintext
Neutron ML2 l2 population Mechanism Drivers
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l2 population (l2pop) mechanism drivers implements the ML2 driver to improve
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open source plugins overlay implementations (VXLAN with Linux bridge and
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GRE/VXLAN with OVS). This mechanism driver is implemented in ML2 to propagate
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the forwarding information among agents using a common RPC API.
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More informations could be found on the wiki page [1].
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VXLAN Linux kernel:
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-------------------
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The VXLAN Linux kernel module provide all necessary functionalities to populate
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the forwarding table and local ARP responder tables. This module appears on
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release 3.7 of the vanilla Linux kernel in experimental:
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- 3.8: first stable release, no edge replication (multicast necessary),
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- 3.9: edge replication only for the broadcasted packets,
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- 3.11: edge replication for broadcast, multicast and unknown packets.
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Note: Some distributions (like RHEL) have backported this module on precedent
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kernel version.
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OpenvSwitch:
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------------
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The OVS OpenFlow tables provide all of the necessary functionality to populate
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the forwarding table and local ARP responder tables.
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A wiki page describe how the flow tables did evolve on OVS agents:
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- [2] without local ARP responder
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- [3] with local ARP responder. /!\ This functionality is only available since
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the development branch 2.1. It's possible
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to disable (enable by default) it through
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the flag 'arp_responder'. /!\
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Note: A difference persists between the LB and OVS agents when they are used
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with the l2-pop mechanism driver (and local ARP responder available). The
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LB agent will drop unknown unicast (VXLAN bridge mode), whereas the OVS
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agent will flood it.
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[1] https://wiki.openstack.org/wiki/L2population_blueprint
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[2] https://wiki.openstack.org/wiki/Ovs-flow-logic#OVS_flows_logic
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[3] https://wiki.openstack.org/wiki/Ovs-flow-logic#OVS_flows_logic_with_local_ARP_responder |