SR-IOV guide for OVN

The purpose of this page is to describe how SR-IOV works with OVN. Prior to reading this document, it is recommended to first read the basic guide for SR-IOV.

External ports

The SR-IOV feature is leverage by OVN external ports. For more information about external ports, its scheduling and troubleshoot, please check the External Ports guide.

Environment setup for OVN SR-IOV

There are a very few differences between setting up an environment for SR-IOV for the OVS and OVN Neutron drivers. As mentioned at the beginning of this document, the instructions from the the basic guide for SR-IOV are required for getting SR-IOV working with the OVN driver.

The only differences required for an OVN deployment are:

  • When configuring the mechanism_drivers in the ml2_conf.ini file we should specify ovn driver instead of the openvswitch driver

  • Disabling the Neutron DHCP agent

  • Deploying the OVN Metadata agent on the gateway nodes (controller or networker nodes)

North/South routing

A network with an external port (SR-IOV, baremetal), will create a HA_Chassis_Group register to schedule these external ports in gateway chassis. The routers also use HA_Chassis_Group registers to execute the scheduling of the gateway port. Since the implementation of [1], when a network is connected as an internal network, the Neutron API will sync the network HA_Chassis_Group with the gateway port HA_Chassis_Group. That will make both scheduling methods to be in sync and will collocate the gateway router port and the external port in the same OVN gateway chassis; that allows OVN to route the traffic from the external port through the gateway port.

When the network HA_Chassis_Group is updated, it could be possible that the currently assigned gateway chassis changes. However, before connecting the network to the router, this port is used only for DHCP and metadata; the external port binding change won’t interrupt the traffic.

References