Add missing description of Linuxbridge egress bw limit

Add to QoS devref document missing description about how
egress bandwidth limit rules are implemented by Linuxbridge
agent driver.

Change-Id: I1ce44aba14d54179e64f8d0516e0a60605b2add1
This commit is contained in:
Sławek Kapłoński 2017-06-23 20:02:24 +00:00 committed by Akihiro Motoki
parent 2ce4f19afd
commit ad49bbd0f2

@ -356,6 +356,16 @@ For egress bandwidth limit rule:
* update_filters_bw_limit
* delete_filters_bw_limit
The egress bandwidth limit is configured on the tap port by setting traffic
policing on tc ingress queueing discipline (qdisc). Details about ingress
qdisc can be found on `lartc how-to <http://lartc.org/howto/lartc.adv-qdisc.ingress.html>`__.
The reason why ingress qdisc is used to configure egress bandwidth limit is that
tc is working on traffic which is visible from "inside bridge" perspective. So
traffic incoming to bridge via tap interface is in fact outgoing from Neutron's
port.
This implementation is the same as what Open vSwitch is doing when
ingress_policing_rate and ingress_policing_burst are set for port.
For ingress bandwidth limit rule:
* set_tbf_bw_limit