Merge "Strict minimum bandwidth support for tunnelled networks"
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specs/2023.1/strict-minimum-bandwidth-tunnelled-networks.rst
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specs/2023.1/strict-minimum-bandwidth-tunnelled-networks.rst
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This work is licensed under a Creative Commons Attribution 3.0 Unported
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License.
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http://creativecommons.org/licenses/by/3.0/legalcode
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=======================================================
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Strict minimum bandwidth support for tunnelled networks
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=======================================================
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Launchpad bug: https://bugs.launchpad.net/neutron/+bug/1991965
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The aim of the RFE is to improve the previous implemented RFE Strict minimum
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bandwidth support [1]_.
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Problem Description
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===================
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Since [1]_, Neutron has the ability to model the available bandwidth of the
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physical interfaces (ingress and egress) connected to the physical networks
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(flat and VLAN networks). This information is collected by Placement and
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used to spawn virtual machines with network ports on compute nodes with
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enough bandwidth. That guarantees a minimum port throughput.
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This feature is currently implemented in three backends: ML2/SR-IOV, ML2/OVS
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and ML2/OVN. The full list of related patches can be reviewed at [2]_.
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However, most of the current deployments do not use physical backed networks
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(flat or VLAN) but overlay networs (VXLAN and Geneve). Of course those
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deployments use ML2/OVS and ML2/OVN; ML2/SR-IOV does not support tunnelled
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networks. That leads to an existing gap in the currently implemented feature:
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there is no way to model tunnelled networks.
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Proposed Change
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===============
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This RFE proposes a way to model the available bandwidth for tunnelled
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networks in compute nodes. This implementation will be limited to ML2/OVS
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and ML2/OVN backends.
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The referred backends handle the overlay traffic sending and receiving this
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traffic from a host interface, that acts as a VTEP [3]_. This host interface
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is identified by an IP address, known as "local_ip" in the ML2 plugin
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configuration file [4]_.
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This RFE proposes to use the same configuration options provided in [1]_,
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adding a static string constant to define a resource provider in Placement
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that could be configurable by the administrator. This string will be the
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suffix of the resource provider name, same as Neutron uses the physical
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bridge names to build their resource provider names. For example
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"u20ovn:OVN Controller agent:rp_tunnelled", being "rp_tunnelled" the provided
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string. The default value will be "rp_tunnelled". This configuration variable
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will be stored in the ``[ml2]`` section and will be accesible from the Neutron
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server and the OVS agent::
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[ml2]
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tunnelled_network_rp_name = custom_rp_name # "rp_tunnelled" by default.
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Example of ML2/OVS configuration section::
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[ovs]
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resource_provider_bandwidths = br0:EGRESS:INGRESS,rp_tunnelled:EGRESS:INGRESS
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Example of ML2/OVN configuration, stored in the local database of the OVS
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service::
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root@u20ovn:~# ovs-vsctl list open_vswitch .
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...
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external_ids : {hostname=u20ovn,
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ovn-bridge=br-int,
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ovn-bridge-mappings="public:br-ex",
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ovn-cms-options="enable-chassis-as-gw,
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resource_provider_bandwidths=br-ex:4001:5001;rp_tunnelled:4001:5001,
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resource_provider_inventory_defaults=allocation_ratio:1.0;min_unit:5,
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resource_provider_hypervisors=br-ex:u20ovn;rp_tunnelled:u20ovn",
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ovn-encap-ip="192.168.10.40",
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ovn-encap-type=geneve,
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ovn-remote="tcp:192.168.10.40:6642",
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system-id="a55c8d85-2071-4452-92cb-95d15c29bde7"}
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Note that in ML2/OVN, it is mandatory to define the tunnelled resource provider assignation to
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the host in the "resource_provider_hypervisors" list.
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This new string constant cannot be used as a physical bridge name. To avoid
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any possible clash, there will be a new check when parsing the physical
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network bridge mappings.
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A host with ML2/OVN backend with a physical network (mapped to the physical
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bridge "br-ex") and a tunnelled network will report the following resource
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provider tree::
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$ openstack resource provider list
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+--------------------------------------+------------------------------------------+------------+--------------------------------------+--------------------------------------+
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| uuid | name | generation | root_provider_uuid | parent_provider_uuid |
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+--------------------------------------+------------------------------------------+------------+--------------------------------------+--------------------------------------+
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| 8f0e060d-bf63-42a1-85e6-710c8b2fccc8 | u20ovn | 10 | 8f0e060d-bf63-42a1-85e6-710c8b2fccc8 | None |
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| cb101b60-527b-5264-8e7f-213c7b88e9e1 | u20ovn:OVN Controller agent | 1 | 8f0e060d-bf63-42a1-85e6-710c8b2fccc8 | 8f0e060d-bf63-42a1-85e6-710c8b2fccc8 |
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| 521f53a6-c8c0-583c-98da-7a47f39ff887 | u20ovn:OVN Controller agent:br-ex | 20 | 8f0e060d-bf63-42a1-85e6-710c8b2fccc8 | cb101b60-527b-5264-8e7f-213c7b88e9e1 |
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| dfdbf43f-f60b-577c-bae8-3dcea448c735 | u20ovn:OVN Controller agent:rp_tunnelled | 6 | 8f0e060d-bf63-42a1-85e6-710c8b2fccc8 | cb101b60-527b-5264-8e7f-213c7b88e9e1 |
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+--------------------------------------+------------------------------------------+------------+--------------------------------------+--------------------------------------+
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A new static trait will be added to represent this resource provider:
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"CUSTOM_NETWORK_TUNNEL_PROVIDER". This is what identify that this resource
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provider is for tunnelled networks. E.g.::
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$ openstack resource provider trait list $rp_tun
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+----------------------------------+
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| name |
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+----------------------------------+
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| CUSTOM_VNIC_TYPE_NORMAL |
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| CUSTOM_VNIC_TYPE_DIRECT |
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| CUSTOM_VNIC_TYPE_DIRECT_PHYSICAL |
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| CUSTOM_VNIC_TYPE_MACVTAP |
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| CUSTOM_VNIC_TYPE_VDPA |
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| CUSTOM_VNIC_TYPE_REMOTE_MANAGED |
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| CUSTOM_VNIC_TYPE_BAREMETAL |
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| CUSTOM_NETWORK_TUNNEL_PROVIDER |
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+----------------------------------+
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This is an example of a port resource request, sent to Nova when creating a
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virtual machine. The port has a minimum bandwidth rule of 500 kbps, egress
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direction::
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port['resource_request'] = {
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'request_groups': [
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{'id': 'c51c6f07-8e01-548c-9756-d5e54a780bb6',
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'required': ['CUSTOM_NETWORK_TUNNEL_PROVIDER', 'CUSTOM_VNIC_TYPE_NORMAL'],
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'resources': {'NET_BW_EGR_KILOBIT_PER_SEC': 500}
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}
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],
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'same_subtree': ['c51c6f07-8e01-548c-9756-d5e54a780bb6']
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}
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.. note::
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This spec is not considering the case of shared resource providers. For
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example when the same interface is shared between a VLAN/flat network and
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and overlay network. What this spec is proposing is to provide the
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scheduling functionality to ports in overlay networks. In case of having
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shared resources, the administrator will need to split bandwidth assignation
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between resource providers. Currently Placement API nor Neutron cannot
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provide a way to model a shared resource.
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REST API Impact
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---------------
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This RFE does not introduce any API change.
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Data Model Impact
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-----------------
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This RFE does not introduce any model change.
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Security Impact
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---------------
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None.
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Performance Impact
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------------------
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None.
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Other Impact
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------------
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Currently there is no support for minimum bandwidth QoS rules for tunnelled
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networks, neither in Placement nor in the ML2 backend (OVS, OVN). However,
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it is possible to have ports with those type of QoS rules (maybe inherited
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from the network QoS policy). With this feature, the minimum bandwidth QoS
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rules won't be discarded, like now, when the port resource request is built
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(that is the Placement blob to request a specific bandwidth in a specific
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network).
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A new check will be added to inform about those ports located on
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tunnelled networks with minimum bandwidth QoS rules. The output of this check
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will be a log with the list of ports, their networks and QoS policies. This
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spec is considering the current Neutron implementation:
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* ML2/OVS rejects the assignation of a QoS policy with minimum bandwidth rules
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and prevents from binding a port with them.
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* The ML2/OVN mechanism driver implemented the minimum bandwidth rule support
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recently and does not prevent this scenario. However this functionality was
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implemented in Zed release; it is unlikely that many deployments are in this
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state (with ports located in overlay networks with QoS policies and minimum
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bandwidth rules).
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This spec does not consider the rebuild of the current allocations. Any port
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already present in a host that creates a new resource provider for tunnelled
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networks, won't be allocated. Once there is standard a procedure to perform
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this action, a new spec/bug will be created to track this improvement, but
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this is out of scope in this spec.
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Part of this RFE will be to document the alternatives the user has to, in
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case of having a port with minimum bandwidth rules before enabling this
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feature, create the needed allocations:
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* Live migrate the VM with the port. That will trigger the Placement
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scheduling and the allocation creation.
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* Detach and attach again the port to the VM. That will have the same
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effect. This functionality was added to Nova in Wallaby.
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Implementation
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==============
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Assignee(s)
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-----------
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Primary assignees:
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Rodolfo Alonso Hernandez <ralonsoh@redhat.com> (IRC: ralonsoh)
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Work Items
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----------
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* ML2 plugin update.
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* Migration script to log those existing ports with minimum bandwidth rules
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in tunnelled networks.
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* Documentation, including the methods to re-created the allocations for pre-
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created ports.
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* Tests and CI related changes.
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Testing
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=======
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* Unit/functional tests.
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* Fullstack tests: increase the current fullstack tests coverage to check
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this new feature.
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* Tempest tests: create a VM with a minimum bandwidth port, update the
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QoS policy and minimum bandwidth rule limits, unset the QoS policy,
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migrate the VM.
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Documentation Impact
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====================
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User Documentation
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------------------
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Ammend the "Strict minimum bandwidth support" [1]_ documentation, adding this
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new improvement.
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References
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==========
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.. [1] [RFE] Strict minimum bandwidth support (egress)
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https://bugs.launchpad.net/neutron/+bug/1578989
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.. [2] https://review.opendev.org/q/%25231578989
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.. [3] https://networklessons.com/cisco/ccnp-encor-350-401/introduction-to-virtual-extensible-lan-vxlan
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.. [4] https://github.com/openstack/neutron/blob/599c81767ea7aa3bde7a64ff57b20f34fb314548/neutron/conf/plugins/ml2/drivers/ovs_conf.py#L44-L50
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