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Merge "[doc] Document the L3 QoS support in Neutron"

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Zuul
2025-08-01 07:42:37 +00:00
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doc/source/admin/config-qos.rst
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@@ -138,11 +138,20 @@ Valid DSCP mark values are even numbers between 0 and 56, except 2-6, 42, and
L3 QoS support L3 QoS support
~~~~~~~~~~~~~~ ~~~~~~~~~~~~~~
The Neutron L3 services have implemented their own QoS extensions. Currently The Neutron L3 services have implemented their own QoS extensions. It is
only bandwidth limit QoS is provided. This is the L3 QoS extension list: possible to apply QoS policies to the floating IPs and to the routers; in the
last one (routers), the QoS policy will be applied on the gateway port.
* Floating IP bandwidth limit: the rate limit is applied per floating IP The rule support depends on the ML2 backend used.
address independently.
ML2/OVS
-------
The ML2/OVS L3 QoS supports only rate limit rules:
* Floating IP bandwidth limit: rate limit is applied per floating IP address
independently.
* Gateway IP bandwidth limit: the rate limit is applied in the router namespace * Gateway IP bandwidth limit: the rate limit is applied in the router namespace
gateway port (or in the SNAT namespace in case of DVR edge router). The rate gateway port (or in the SNAT namespace in case of DVR edge router). The rate
@@ -150,7 +159,42 @@ only bandwidth limit QoS is provided. This is the L3 QoS extension list:
will be limited. This rate limit does not apply to the floating IP traffic. will be limited. This rate limit does not apply to the floating IP traffic.
L3 services that provide QoS extensions: ML2/OVN
-------
The ML2/OVN L3 QoS supports both rate limit and DSCP rules. Both floating IP
and gateway port QoS policies are applied using the QoS metering rules.
* Floating IP: the traffic should match the gateway port and the floating IP
address. The port can be centralized or distributed.
* Gateway port: the traffic should match the gateway chassis port.
Because both floating IP and router can have QoS policies and both QoS policies
will match the same traffic, the floating IP policy has a higher priority and
will match this one only. In case of having port policies, that will apply to
the virtual machine private port, the private port rule will be applied first.
This is the QoS rules precedence and result:
* Rate limit rules: if both private port QoS and router/floating IP rules are
applied, because both will be executed, the minimum rate limit value will
apply.
* DSCP rules: if both private port QoS and router/floating IP rules are
applied, the router/floating IP DSCP mark will be applied on the egress
packet.
.. note::
In case of having both router and floating IP QoS policies, the floating IP
QoS policy has precedence always over the router QoS one. See `[OVN] Change
the OVN QoS rule priority for floating IPs <https://review.opendev.org/q/If01a8783ac998b2a1f1249ab6f555dd1a5148ea8>`_.
L3 services that provide QoS extensions
---------------------------------------
* L3 router: implements the rate limit using `Linux TC * L3 router: implements the rate limit using `Linux TC
<https://man7.org/linux/man-pages/man8/tc.8.html>`_. <https://man7.org/linux/man-pages/man8/tc.8.html>`_.
@@ -162,16 +206,31 @@ L3 services that provide QoS extensions:
The following table shows the L3 service, the QoS supported extension, and The following table shows the L3 service, the QoS supported extension, and
traffic directions (from the VM point of view) for **bandwidth limiting**. traffic directions (from the VM point of view) for **bandwidth limiting**.
.. table:: **L3 service, supported extension, and traffic direction** .. table:: **L3 service, supported extension and traffic direction for
bandwidth limiting**
==================== =================== =================== ==================== =================== ===================
Rule \\ L3 service L3 router OVN L3 L3 service L3 router OVN L3
==================== =================== =================== ==================== =================== ===================
Floating IP Egress \\ Ingress Egress \\ Ingress Floating IP Egress \\ Ingress Egress \\ Ingress
Gateway IP Egress \\ Ingress Egress \\ Ingress Gateway IP Egress \\ Ingress Egress \\ Ingress
==================== =================== =================== ==================== =================== ===================
The following table shows the L3 service, the QoS supported extension, and
traffic directions (from the VM point of view) for **DSCP marking**.
.. table:: **L3 service, supported extension and traffic direction for
DSCP marking**
==================== =========== ========
L3 service L3 router OVN L3
==================== =========== ========
Floating IP - Egress
Gateway IP - Egress
==================== =========== ========
Configuration Configuration
~~~~~~~~~~~~~ ~~~~~~~~~~~~~