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[Slawek Kaplonski <1708460@xxxxxxxxxxxxxxxxxx>]

** Changed in: neutron
       Status: Confirmed => Opinion

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https://bugs.launchpad.net/bugs/1708460

Title:
   [RFE] Reaction to network congestion for qos

Status in neutron:
  Opinion

Bug description:
  Problem description:
  ********************
  In a multi-tenant environment, some VMs could consume the available bandwidth and cause network congestion for those that share the same network resources. To improve the quality of service, openstack implements a service to limit the bandwidth of VM ports and classify the traffic using DSCP field. However, there is still a lack of a mechanism policing specific VMs that consume a lot of resources and generate network congestion.

  
  API effects:
  ************
  By adding a new rule in the QoS extension [1] of neutron we could detect and react dynamically to the congestion. This rule will police VMs causing congestion by limiting the allowed bandwidth in their ports.

  
  Proposal:
  *********
  Our proposal is to use Explicit Congestion Notification (ECN) [2] bits as marking mechanism. So, the network near congestion will mark packets as Congestion Experienced (CE). Neutron will detect these packets and starts monitoring the behavior of the VM causing the congestion. When the congestion exceeding a threshold, neutron will react by policing this VM using the bandwidth limitation rule of QoS extension. Neutron will keep track of the congestion rate and will free the policed VMs when the congestion is over.

  References:
  ***********
  [1] QoS https://docs.openstack.org/ocata/networking-guide/config-qos.html
  [2] ECN in IP https://tools.ietf.org/html/rfc3168

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