Gaps from ML2/OVS

This is a list of some of the currently known gaps between ML2/OVS and OVN. It is not a complete list, but is enough to be used as a starting point for implementors working on closing these gaps. A TODO list for OVN is located at 1.

  • Security Groups logging API

    Currently ML2/OVS, with the OpenvSwitch firewall, supports a log file where security groups events are logged to be consumed by a security entity. This allows users to have a way to check if an instance is trying to execute restricted operations, or access restricted ports in remote servers.

    This is a relatively new extension, support would need to be added to OVN.

  • QoS DSCP support

    Currently ML2/OVS supports QoS DSCP tagging and egress bandwidth limiting. Those are basic QoS features that while integrated in the OVS/OVN C core are not integrated (or fully tested) in the neutron OVN mechanism driver.

  • QoS for Layer 3 IPs

    Currently the Neutron L3-agent supports floating IP and gateway IP bandwidth limiting based on Linux TC. Networking-ovn L3 had a prototype implementation 2 based on the meter of openvswitch 3 utility that has been abandoned. This is supported in user space datapath only, or kernel versions 4.15+ 4.

  • QoS Minimum Bandwidth support

    Currently ML2/OVS supports QoS Minimum Bandwidth limiting, but it is not supported in OVN.

  • BGP support

    Currently ML2/OVS supports making a tenant subnet routable via BGP, and can announce host routes for both floating and fixed IP addresses.

  • Baremetal provisioning with iPXE

    The core OVN DHCP server implementation does not have support for sending different boot options based on the gpxe DHCP Option (no. 175). Also, Ironic uses dnsmasq syntax when configuring the DHCP options for Neutron 5 which is not understood by the OVN driver.

  • Availability Zones

    Availability zones are used to make network resources highly available by grouping nodes in separate zones which resources will be scheduled to. Neutron supports two types of availability zones: Network (DHCP agent) and router (L3 agent). The OVN team needs to assess each case to see how they would fit in the OVN model. For example, in the router availability zone case, the OVN driver should schedule the router ports on a Chassis (a “node” in OVN terms) where the availability zones match with the router availability zones 6.

  • Routed provider networks

    Routed provider networks allow for a single provider network to represent multiple L2 domains (segments). The OVN driver does not understand this feature yet and will need to account for multiple physical networks associated with a single OVN Logical Switch (a network in Neutron terms) 7.

  • QoS minimum bandwidth allocation in Placement API

    ML2/OVN integration with the Nova placement API to provide guaranteed minimum bandwidth for ports 8.

  • IPv6 Prefix Delegation

    Currently ML2/OVN doesn’t implement IPv6 prefix delegation. OVN logical routers have this capability implemented in 9 and we have an open RFE to fill this gap 10.