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[Rodolfo Alonso <1777866@xxxxxxxxxxxxxxxxxx>]

** Changed in: neutron
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1777866

Title:
  QoS CLI – Warning in case when provided burst is lower than 80% BW

Status in neutron:
  Fix Released

Bug description:
  According QoS documentation
  https://docs.openstack.org/neutron/queens/admin/config-qos.html in
  order to get the desired BW limit, user must set Burst value which is
  bigger than 80% of provided by user BW.

  --- 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. 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. ---

  
  In addition to that (note in documentation) we can add this "80% validation" at least on CLI level (not relevant for Rest API) and to prompt some Warning message to the user, in case he’s trying to set burst lower than 80% BW, so he could understand that desired BW won’t be reached.

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