11. Calculation of Flexible Algorithm Paths

This section preserves the RFC text for IGP Flex-Algorithm reverse affinity constraints, including FAERAG, FAD, IS-IS and OSPF Sub-TLVs, reverse Administrative Groups, IANA registrations, and path pruning rules.

Original RFC Text

11.  Calculation of Flexible Algorithm Paths

   The following procedures augment the rules defined in Section 13 of
   [RFC9350] by introducing additional constraints based on
   Administrative Groups (AGs) associated with the reverse direction of
   a link.

   *  Check if any exclude reverse Admin Group rule is part of the Flex-
      Algorithm definition.  If such exclude rule exists, check if any
      Admin Group that is part of the exclude rule is also set on the
      link in the reverse direction.  If such Admin Group is set on the
      link in the reverse direction, the link MUST be pruned from the
      computation.

   *  Check if any include-any reverse Admin Group rule is part of the
      Flex-Algorithm definition.  If such include-any rule exists, check
      if any Admin Group that is part of the include-any rule is also
      set on the link in the reverse direction.  If no such Admin Group
      is set on the link in the reverse direction, the link MUST be
      pruned from the computation.

   *  Check if any include-all reverse Admin Group rule is part of the
      Flex-Algorithm definition.  If such include-all rule exists, check
      if all Admin Groups that are part of the include-all rule are also
      set on the link in the reverse direction.  If all such Admin
      Groups are not set on the link in the reverse direction, the link
      MUST be pruned from the computation.

   Please see rules 8, 9, and 10 in Section 12.3 for these added rules.