[ovs-discuss] QoS in OVS compared to tc

[Ben Pfaff]

On Tue, Aug 16, 2011 at 05:09:54PM -0700, Syed Akbar Mehdi wrote:
> The description of the QoS tables in the Open vSwitch configuration database
> (http://openvswitch.org/ovs-vswitchd.conf.db.5.pdf manual on page 21-22)
> refers to the documentation of the Linux hierarchy token bucket classifier
> at http://luxik.cdi.cz/~devik/qos/htb/manual/userg.htm.
> 
> However if I configure the Linux-htb classifier using tc, I get the option
> to configure qdiscs and classes in a "hierarchy" which allows fine-grained
> tuning of QoS policies e.g. excess-bandwidth sharing (or not sharing)
> between different classes. The OVS documentation gives the impression that
> this hierarchical configuration is not possible when configuring queues
> using OVS (e.g. using ovs-vsctl). It appears that I can only configure
> queues in a "flat" configuration where all queues are at the same level. Is
> this true? In case it is then what is the policy for excess bandwidth
> sharing between different queues.

It's true that OVS does not provide access to the full power of the
HTB qdisc.  We chose to make a subset of the functionality available.
I don't remember the details of the excess bandwidth sharing
policy--you can of course view it by using "tc" to dump the setup--but
it is, in general, enabled.