RPC messages in OVN

ML2/OVN driver uses the OVN NB tables Port_Group and ACL to implement security groups. Security groups and security group rules are directly sent to OVN NB via the OVSDB protocol. Neutron doesn’t send any RPC messages related to these topics when using the ML2/OVN mechanism driver.

However, other RPC topics are kept in case other drivers are being used, for example ML2/SRIOV, DHCP agents (for baremetal ports), etc.