202fa1f4a2
Add documentation for Routed Provider Networks. Co-Authored-By: Lucas Alvares Gomes <lucasagomes@gmail.com> Closes-Bug: #1865889 Change-Id: Ie9b7ba52b5b9e93480f22d6863038bea23a19123
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3.4 KiB
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83 lines
3.4 KiB
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.. _ovn_gaps:
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Gaps from ML2/OVS
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=================
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This is a list of some of the currently known gaps between ML2/OVS and OVN.
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It is not a complete list, but is enough to be used as a starting point for
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implementors working on closing these gaps. A TODO list for OVN is located
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at [1]_.
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* QoS DSCP support
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Currently ML2/OVS supports QoS DSCP tagging and egress bandwidth limiting.
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Those are basic QoS features that while integrated in the OVS/OVN C core
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are not integrated (or fully tested) in the neutron OVN mechanism driver.
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* QoS for Layer 3 IPs
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Currently the Neutron L3-agent supports floating IP and gateway IP bandwidth
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limiting based on Linux TC. Networking-ovn L3 had a prototype
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implementation [2]_ based on the meter of openvswitch [3]_ utility that
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has been abandoned. This is supported in user space datapath only, or
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kernel versions 4.15+ [4]_.
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* QoS Minimum Bandwidth support
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Currently ML2/OVS supports QoS Minimum Bandwidth limiting, but it is
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not supported in OVN.
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* BGP support
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Currently ML2/OVS supports making a tenant subnet routable via BGP, and
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can announce host routes for both floating and fixed IP addresses.
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* Baremetal provisioning with iPXE
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The core OVN DHCP server implementation does not have support for
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sending different boot options based on the ``gpxe`` DHCP Option
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(no. 175). Also, Ironic uses dnsmasq syntax when configuring the DHCP
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options for Neutron [5]_ which is not understood by the OVN driver.
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* Availability Zones
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Availability zones are used to make network resources highly available
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by grouping nodes in separate zones which resources will be scheduled
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to. Neutron supports two types of availability zones: Network (DHCP
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agent) and router (L3 agent). The OVN team needs to assess each case
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to see how they would fit in the OVN model. For example, in the router
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availability zone case, the OVN driver should schedule the router
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ports on a Chassis (a "node" in OVN terms) where the availability
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zones match with the router availability zones [6]_.
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* QoS minimum bandwidth allocation in Placement API
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ML2/OVN integration with the Nova placement API to provide guaranteed
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minimum bandwidth for ports [7]_.
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* IPv6 Prefix Delegation
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Currently ML2/OVN doesn't implement IPv6 prefix delegation. OVN logical
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routers have this capability implemented in [8]_ and we have an open RFE to
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fill this gap [9]_.
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* East/West Fragmentation
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The core OVN implementation does not support east/west fragmentation. There is
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no known production use-case for this feature hence we don't even have an RFE
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open for it and it's not on the roadmap to be implemented.
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References
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----------
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.. [1] https://github.com/ovn-org/ovn/blob/master/TODO.rst
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.. [2] https://review.opendev.org/#/c/539826/
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.. [3] https://github.com/openvswitch/ovs/commit/66d89287269ca7e2f7593af0920e910d7f9bcc38
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.. [4] https://github.com/torvalds/linux/blob/master/net/openvswitch/meter.h
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.. [5] https://github.com/openstack/ironic/blob/123cb22c731f93d0c608d791b41e05884fe18c04/ironic/common/pxe_utils.py#L447-L462>
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.. [6] https://docs.openstack.org/neutron/latest/admin/config-az.html
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.. [7] https://specs.openstack.org/openstack/neutron-specs/specs/rocky/minimum-bandwidth-allocation-placement-api.html
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.. [8] https://patchwork.ozlabs.org/project/openvswitch/patch/6aec0fb280f610a2083fbb6c61e251b1d237b21f.1576840560.git.lorenzo.bianconi@redhat.com/
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.. [9] https://bugs.launchpad.net/neutron/+bug/1895972
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