This epic cover the effort to implement the ML2/OVN minimum bandwidth QoS support.

During the testing of [1], it was found that Neutron ML2/OVN QoS extension is using two OVN QoS APIs:

• The OVN QoS registers. These are used for DSCP marking and bandwidth policing (not shaping). It was enough when the minimum bandwidth rule was not supported.
• The LSP.options rate values [2], that allow to define maximum and minimum bandwidth.

In order to define a minimum bandwidth rule, it is also needed to define a maximum rule in the LSP.options dictionary. The previously implemented maximum bandwidth feature is no longer valid and needs to be refactored.

This issue is affecting to all existing versions:

• master U/S, that will be the future OSP18 [3]
• OSP18 (this epic)
• OSP17 (won't be supported, still under decision)

DoD:

• Implementation of the code in U/S and backported to OSP18.
• Testing, done by QA team.
• Documentation.

NOTE: there is a missing feature in core OVN that is tracked in [4]. It is needed to set the HTB max rate for the parent class ID of the TC qdisc created in the egress interface. In case of not having a value, the default rate will be 10Gbps. That usually happens in the virtualized environments: the virtual NICs don't provide a speed link value. This is why https://issues.redhat.com/browse/OSPRH-11046 provides info about how to set this value during testing.

[1]https://bugzilla.redhat.com/show_bug.cgi?id=2077681

[2]https://www.ovn.org/support/dist-docs/ovn-nb.5.html

[3]https://bugs.launchpad.net/neutron/+bug/2015376

[4]https://issues.redhat.com/browse/FDP-951