From 1ba9f7fd752b28ed9429d5d844d586ce23a9ea2f Mon Sep 17 00:00:00 2001 From: Rodolfo Alonso Hernandez Date: Mon, 14 Jul 2025 10:28:41 +0000 Subject: [PATCH] [doc] Document the L3 QoS support in Neutron The L3 QoS support documentation, in particular the ML2/OVN one, was outdated. This patch documents: * The ML2/OVN L3 QoS support for DSCP marking. * The ML2/OVN rule enforcement and precedence. Closes-Bug: #2116317 Signed-off-by: Rodolfo Alonso Hernandez Change-Id: I52219523cf958e787fae4d3104fb2638698a28d8 --- doc/source/admin/config-qos.rst | 73 +++++++++++++++++++++++++++++---- 1 file changed, 66 insertions(+), 7 deletions(-) diff --git a/doc/source/admin/config-qos.rst b/doc/source/admin/config-qos.rst index a1bca144b5c..e7fcab15e84 100644 --- a/doc/source/admin/config-qos.rst +++ b/doc/source/admin/config-qos.rst @@ -137,11 +137,20 @@ Valid DSCP mark values are even numbers between 0 and 56, except 2-6, 42, and L3 QoS support ~~~~~~~~~~~~~~ -The Neutron L3 services have implemented their own QoS extensions. Currently -only bandwidth limit QoS is provided. This is the L3 QoS extension list: +The Neutron L3 services have implemented their own QoS extensions. It is +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 - address independently. +The rule support depends on the ML2 backend used. + + +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 port (or in the SNAT namespace in case of DVR edge router). The rate @@ -149,7 +158,42 @@ 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. -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 `_. + + +L3 services that provide QoS extensions +--------------------------------------- * L3 router: implements the rate limit using `Linux TC `_. @@ -161,16 +205,31 @@ L3 services that provide QoS extensions: The following table shows the L3 service, the QoS supported extension, and 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 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 ~~~~~~~~~~~~~