module openconfig-if-sdn-ext {

    yang-version 1;

    namespace
      "http://openconfig.net/interfaces/sdn-ext";

    prefix oc-if-sdn;

    import openconfig-extensions {
      prefix oc-ext;
    }
    import openconfig-interfaces {
      prefix oc-if;
    }

    organization "OpenConfig working group";

    contact "www.openconfig.net";

    description
      "This module provides extensions to the OpenConfig interfaces
    module for network elements that support external 'SDN' control
    of their interfaces.";

    revision "2024-02-21" {
      description "Initial revision.";
      reference
        "0.2.0";

    }

    revision "2021-03-30" {
      description "Initial revision.";
      reference
        "0.1.0";

    }

    oc-ext:catalog-organization "openconfig";
    oc-ext:origin "openconfig";
    oc-ext:openconfig-version "0.2.0";

    grouping sdn-interface-config {
      description
        "Configuration parameters applicable to interfaces on devices
      that support SDN control.";
      leaf forwarding-viable {
        type boolean;
        default 'true';
        description
          "This value indicates whether the interface may be used
        to route traffic or not.  If set to false, the
        interface is not used for forwarding traffic, but as long as
        it is up, the interface still maintains its layer-2
        adjacencies and runs its configured layer-2 functions
        (e.g., LLDP, etc.).
        This is used by an external programming entity to disable an interface
        (usually part of an aggregate) for the purposes of forwarding
        traffic. This allows a logical aggregate to continue to be
        used with partial capacity. Setting `forwarding-viable = false` is not
        equivalent to administratively disabling the interface.
        Some rules to follow when an interface or aggregate interface is set for
        Forwarding-viable=False:
          1. Aggregate interface '/interfaces/interface/aggregation/state/min-links'
           checks should be evaluated based on
          `/interfaces/interface/state/oper-status`.  'min-links' should not be
          affected by the use of forwarding viable.

          2. L2 protocols like LLDP and LACP must be processed normally on
          transmit and receive on such ports/bundles.  IS-IS PDUs should be
          handled as per the requirements for L3 packets below.

          3. L3 packets must not be transmitted on the interface.

          4. Received L3 packets must be processed normally.  Received data-plane
          traffic will continue to forwarded to its destination post FIB lookup.
          Received control-plane traffic must also be processed normally.

          5. It is possible that the dead-interval or hold-down timer of L3
          protocols like IS-IS/BGP on the peer router may expire taking down the
          adjacency or peering on that connection. However, the peer may still
          continue to transmit packets which are received by the local device.
          These received packet should continue to be processed normally as
          per rule #4 above.

          For example, if the peer's forwarding table is programmed using gRIBI
          by an external controller, the local device will continue to receive
          packets.

          6. An implementation should follow rule #3 even when the subject
          interface on the local device is the last resort of communication for a
          given destination.  For example, the only nexthop for a destination is
          an aggregate interface which has all member interfaces set to
          forwarding-viable = false.  In this scenario all L3 packets for that
          destination will be dropped.";
      }
    }  // grouping sdn-interface-config

    augment /oc-if:interfaces/oc-if:interface/oc-if:config {
      description
        "Add SDN extensions to interface intended configuration.";
      uses sdn-interface-config;
    }

    augment /oc-if:interfaces/oc-if:interface/oc-if:state {
      description
        "Add SDN extensions to interface applied configuration.";
      uses sdn-interface-config;
    }
  }  // module openconfig-if-sdn-ext