module openconfig-bfd {

    yang-version 1;

    namespace
      "http://openconfig.net/yang/bfd";

    prefix oc-bfd;

    import openconfig-extensions {
      prefix ocext;
    }
    import openconfig-types {
      prefix oc-types;
    }
    import openconfig-interfaces {
      prefix oc-if;
    }
    import openconfig-inet-types {
      prefix oc-inet;
    }
    import openconfig-if-types {
      prefix oc-ift;
    }
    import openconfig-network-instance {
      prefix oc-ni;
    }
    import openconfig-policy-types {
      prefix oc-pol-types;
    }

    organization "OpenConfig working group";

    contact
      "OpenConfig working group
    www.openconfig.net";

    description
      "An OpenConfig model of Bi-Directional Forwarding Detection (BFD)
    configuration and operational state.";

    revision "2017-11-17" {
      description
        "Update version number for initial sharing.";
      reference
        "0.1.0";

    }

    revision "2017-10-19" {
      description
        "Adopt OpenConfig types models, type corrections";
      reference
        "0.0.2";

    }

    revision "2016-06-24" {
      description "Initial revision";
      reference
        "0.0.1";

    }

    ocext:openconfig-version "0.1.0";

    typedef bfd-session-state {
      type enumeration {
        enum "UP" {
          value 0;
          description
            "The BFD session is perceived to be up by the system.";
        }
        enum "DOWN" {
          value 1;
          description
            "The BFD session is perceived to be down by the system.";
        }
        enum "ADMIN_DOWN" {
          value 2;
          description
            "The BFD session is administratively disabled.";
        }
        enum "INIT" {
          value 3;
          description
            "The BFD session is perceived to be initialising by the
          system.";
        }
      }
      description
        "The state of the BFD session according to the system referred
      to by the context of the leaf.";
      reference
        "RFC5880 - Bidirectional Forwarding Detection, Section
        4.1";

    }

    typedef bfd-diagnostic-code {
      type enumeration {
        enum "NO_DIAGNOSTIC" {
          value 0;
          description
            "No diagnostic code was specified, or the session has not
          changed state.";
        }
        enum "DETECTION_TIMEOUT" {
          value 1;
          description
            "The control detection time expired: no BFD packet was
          received within the required period.";
        }
        enum "ECHO_FAILED" {
          value 2;
          description
            "The BFD echo function failed - echo packets have not been
          received for the required period of time.";
        }
        enum "FORWARDING_RESET" {
          value 3;
          description
            "The forwarding plane in the local system was reset - such
          that the remote system cannot rely on the forwarding state of
          the device specifying this error code.";
        }
        enum "PATH_DOWN" {
          value 4;
          description
            "Signalling outside of BFD specified that the path underlying
          this session has failed.";
        }
        enum "CONCATENATED_PATH_DOWN" {
          value 5;
          description
            "When a BFD session runs over a series of path segments, this
          error code indicates that a subsequent path segment (i.e.,
          one in the transmit path between the source and destination
          of the session) has failed.";
        }
        enum "ADMIN_DOWN" {
          value 6;
          description
            "The BFD session has been administratively disabled by the
          peer.";
        }
        enum
          "REVERSE_CONCATENATED_PATH_DOWN" {
          value 7;
          description
            "In the case that a BFD session is running over a series of
          path segments, this error code indicates that a path segment
          on the reverse path (i.e., in the transmit direction from the
          destination to the source of the session) has failed.";
        }
      }
      description
        "Diagnostic codes defined by BFD. These typically indicate the
      reason for a change of session state.";
      reference
        "RFC5880 - Bidirectional Forwarding Detection, Section
        4.1";

    }
  }  // module openconfig-bfd