[Docs] Update note about default burst value in QoS bw limit

This patch combines two separate notes about burst value in
QoS bandwidth limit rules into one to make it more clear for
readers.

Change-Id: I48fa93969416db0b0049af533b6aa4021fa22616
Related-Bug: #1777866
This commit is contained in:
Slawek Kaplonski 2018-08-14 13:05:20 +02:00
parent db7e19d2ba
commit 52f0096d13
1 changed files with 13 additions and 16 deletions

View File

@ -296,8 +296,19 @@ First, create a QoS policy and its bandwidth limit rule:
.. note::
The QoS implementation requires a burst value to ensure proper behavior of
bandwidth limit rules in the Open vSwitch and Linux bridge agents. If you
do not provide a value, it defaults to 80% of the bandwidth limit which
bandwidth limit rules in the Open vSwitch and Linux bridge agents.
Configuring the proper burst value is very important. If the burst value is
set too low, bandwidth usage will be throttled even with a proper bandwidth
limit setting. This issue is discussed in various documentation sources, for
example in `Juniper's documentation
<http://www.juniper.net/documentation/en_US/junos12.3/topics/concept/policer-mx-m120-m320-burstsize-determining.html>`_.
For TCP traffic it is recommended to set burst value as 80% of desired bandwidth
limit value. For example, if the bandwidth limit is set to 1000kbps then enough
burst value will be 800kbit. If the configured burst value is too low,
achieved bandwidth limit will be lower than expected. If the configured burst
value is too high, too few packets could be limited and achieved bandwidth
limit would be higher than expected.
If you do not provide a value, it defaults to 80% of the bandwidth limit which
works for typical TCP traffic.
Second, associate the created policy with an existing neutron port.
@ -384,20 +395,6 @@ network, or initially create the network attached to the policy.
$ openstack network set --qos-policy bw-limiter private
.. note::
Configuring the proper burst value is very important. If the burst value is
set too low, bandwidth usage will be throttled even with a proper bandwidth
limit setting. This issue is discussed in various documentation sources, for
example in `Juniper's documentation
<http://www.juniper.net/documentation/en_US/junos12.3/topics/concept/policer-mx-m120-m320-burstsize-determining.html>`_.
Burst value for TCP traffic can be set as 80% of desired bandwidth limit
value. For example, if the bandwidth limit is set to 1000kbps then enough
burst value will be 800kbit. If the configured burst value is too low,
achieved bandwidth limit will be lower than expected. If the configured burst
value is too high, too few packets could be limited and achieved bandwidth
limit would be higher than expected.
The created policy can be associated with an existing floating IP.
In order to do this, user extracts the floating IP id to be associated to
the already created policy. In the next example, we will assign the