PfR: Operational Phases and the Phase Wheel

The PfR Phase Wheel helps illustrate the operation of the various phases PfR uses to calculate best path.  PfR consists of five unique phases each of which is iterated in a specific order and repeated in a cycle, like a ‘Phase Wheel’ so to speak.  This wheel runs constantly going through all the phases in order:

  • Profile Phase – Referred to as the learning phase, the PfR router learns the flows that have high latency and throughput.  The specific traffic that is being ‘profiled or learned’ is referred to as a ‘traffic class’.  the list of all monitored traffic classes (MTC) is referred to as the MTC list.
  • Measure Phase – Collects and computes the performance metrics for the specific MTC traffic identified by objects in the MTC list.
  • Apply Policy Phase – Low and High thresholds are configured and defined in policy and out of policy performance categories.
  • Control Phase – Manipulates the traffic flow by injecting Policy-based routing (PBR)
  • Verify Phase – After controls are introduced, OER will verify OOP event performance and make adjustments as needed to being the policy back into normal performance criteria.

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