module bbf-ancp {

    yang-version 1.1;

    namespace "urn:bbf:yang:bbf-ancp";

    prefix bbf-ancp;

    import bbf-yang-types {
      prefix bbf-yang;
    }
    import ietf-inet-types {
      prefix inet;
    }
    import ietf-yang-types {
      prefix yang;
    }

    organization
      "Broadband Forum <https://www.broadband-forum.org>
     Common YANG Work Area";

    contact
      "Comments or questions about this Broadband Forum YANG module
     should be directed to <mailto:help@broadband-forum.org>.

     Editor:      Nick Hancock, ADTRAN

     Editor:      Ludwig Pauwels, Nokia

     PS Leader:   Joey Boyd, ADTRAN

     WA Director: Joey Boyd, ADTRAN

     WA Director: Sven Ooghe, Nokia";

    description
      "This module contains a collection of YANG definitions for
     supporting the Broadband Forum requirements on the Access Node
     Control Protocol (ANCP) as defined in RFC 6320. As such, this
     module is specific to access network equipment (e.g.,
     BBF-specified Access Nodes and FTTdp DPUs).

     This data model is designed for the Network Management Datastore
     Architecture defined in RFC 8342.

     Copyright (c) 2017-2022, Broadband Forum

     Redistribution and use in source and binary forms, with or
     without modification, are permitted provided that the following
     conditions are met:

     1. Redistributions of source code must retain the above copyright
        notice, this list of conditions and the following disclaimer.

     2. Redistributions in binary form must reproduce the above
        copyright notice, this list of conditions and the following
        disclaimer in the documentation and/or other materials
        provided with the distribution.

     3. Neither the name of the copyright holder nor the names of its
        contributors may be used to endorse or promote products
        derived from this software without specific prior written
        permission.

     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
     CONTRIBUTORS \"AS IS\" AND ANY EXPRESS OR IMPLIED WARRANTIES,
     INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
     MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
     CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
     SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
     NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
     CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT,
     STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
     ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

     The above license is used as a license under copyright only.
     Please reference the Forum IPR Policy for patent licensing terms
     <https://www.broadband-forum.org/ipr-policy>.

     Any moral rights which are necessary to exercise under the above
     license grant are also deemed granted under this license.

     This version of this YANG module is part of TR-383a5; see
     the TR itself for full legal notices.";

    reference
      "RFC 6320";


    revision "2022-03-01" {
      description
        "Amendment 5.
       * Approval Date:    2022-03-01.
       * Publication Date: 2022-03-01.";
      reference
        "TR-383a5: Common YANG Modules
        	  <https://www.broadband-forum.org/technical/download/
        		   TR-383_Amendment-5.pdf>";

    }

    revision "2020-10-13" {
      description
        "Amendment 3.
       * Approval Date:    2020-10-13.
       * Publication Date: 2020-10-13.";
      reference
        "TR-383a3: Common YANG Modules
        	  <https://www.broadband-forum.org/technical/download/
        		   TR-383_Amendment-3.pdf>";

    }


    feature protocol-version {
      description
        "Indicates support for the configuration of the protocol
       version of ANCP sessions.";
    }

    feature partition-id-negotiation {
      description
        "Indicates that the device supports negotiation of the
       Partition ID to be used to be used by ANCP sessions to
       associate ANCP messages with the partition of the Access Node
       (AN) managed by a session.";
    }

    feature session-statistics {
      description
        "Indicates support for statistics for ANCP sessions.";
    }

    feature tcp-port {
      description
        "Indicates support for the configuration of the TCP port for
       ANCP.";
    }

    feature port-message-dampening {
      description
        "Indicates support for the configuration of the dampening
       mechanism to limit the rate at which Port Up and Port Down
       messages are sent to the Network Access Server (NAS).";
    }

    feature session-administrative-state {
      description
        "Indicates support for administratively enabling or disabling
       an ANCP session.";
    }

    feature session-reset {
      description
        "Indicates support for resetting a session.";
    }

    feature nas-connection-state {
      description
        "Indicates support for the state of the connection to the
       Network Access Server (NAS).";
    }

    identity capabilities {
      description
        "Base identity for defining ANCP capabilities.";
    }

    identity topology-discovery {
      base capabilities;
      description
        "The Access Topology Discovery function is intended to
       allow the NAS to gain knowledge about the topology of the
       access network, the various lines being used, and their
       respective rates without having to rely on an integration
       with an OSS system.";
      reference
        "RFC 6320 section 6";

    }

    identity access-line-technology {
      description
        "Base identity for defining the technology of access lines
       managed by a partition.";
      reference
        "RFC 6320 section 6.5";

    }

    identity access-line-attribute {
      description
        "Base identity for defining access line attributes defined in
       the ANCP.

       This is an abstract identity and MUST NOT be used for access
       line attributes.";
      reference
        "RFC 6320 section 6.5";

    }

    identity technology-independent-access-line-attribute {
      base access-line-attribute;
      description
        "Base identity for defining technology-independent access line
       attributes defined in the ANCP.

       This is an abstract identity and MUST NOT be used for access
       line attributes.";
      reference
        "RFC 6320 section 6.5";

    }

    identity access-loop-encapsulation {
      base technology-independent-access-line-attribute;
      description
        "The data link protocol and, optionally, the encapsulation
       overhead on the access loop.";
      reference
        "RFC 6320 section 6.5.18";

    }

    identity adjacency-malfunction-cause {
      description
        "Base identity for defining causes that resulted in the
       malfunction of the Adjacency Protocol.

       This identity is abstract and SHOULD NOT generally be used for
       malfunction causes. If used to define a cause that was not
       known at design time, it MUST be qualified with an associated
       message string. This practice, however, should be generally
       avoided to ensure all possible causes are known at design
       time.";
    }

    identity message-type-not-supported {
      base adjacency-malfunction-cause;
      description
        "The ANCP agent has received the result code value 0x51 in a
       response message which indicates that message type of the
       original request was not supported";
    }

    identity capability-negotiation-failed {
      base adjacency-malfunction-cause;
      description
        "The ANCP session was unable to successfully negotiate a common
       set of capabilities with its Network Access Server (NAS).";
    }

    typedef protocol-version {
      type enumeration {
        enum "rfc6320" {
          value 0;
          description
            "RFC 6320 defines ANCP Version 1 which is identified by
           version = 50 in protocol messages as defined the joint
           GSMP / ANCP Version Registry. ";
          reference
            "RFC 6320 section 10.8";

        }
      }
      description
        "Defines the supported protocol versions.";
    }

    typedef partition-id {
      type uint8 {
        range "1..255";
      }
      description
        "Defines the Partition ID.";
      reference
        "RFC 6320 section 3.5.1";

    }

    typedef entity-name {
      type union {
        type enumeration {
          enum "unknown" {
            value 0;
            description
              "The name of the sending/receiving entity is unknown.";
          }
        }
        type yang:hex-string {
          length "17";
        }
      }
      description
        "An entity name used to identify the sender/receiver of an
       ANCP message.";
      reference
        "RFC 6320 section 3.5.1";

    }

    typedef link-instance {
      type union {
        type uint32 {
          range "1..16777216";
        }
        type enumeration {
          enum "undefined" {
            value 0;
            description
              "The instance number is undefined.";
          }
        }
      }
      description
        "The instance number used to identify the link within the
       AN or NAS.";
      reference
        "RFC 6320 section 3.5.1";

    }

    grouping peer-operational-parameters {
      description
        "Defines the operational state only parameters applicable to
       the adjacency protocol.";
      leaf name {
        type entity-name;
        config false;
        mandatory true;
        description
          "The Name used by the entity (AN or NAS) as advertised in
         the adjacency message.

         This leaf has value 'unknown', if adjacency state is not
         ESTAB (established).";
      }

      leaf instance {
        type link-instance;
        config false;
        mandatory true;
        description
          "The value for Instance used by the entity (AN or NAS) to
         identify the link to the peer.

         This leaf has value 'undefined', if adjacency state is not
         ESTAB (established).";
      }
    }  // grouping peer-operational-parameters

    grouping ancp-schema {
      description
        "Defines the schema tree for ANCP.";
      container partitions {
        must
          "(bbf-ancp:partition/bbf-ancp:partition-id='global' "
            + "and "
            + "count(bbf-ancp:partition)=1)"
            + " or "
            + "not(bbf-ancp:partition/bbf-ancp:partition-id='global')" {
          error-message
            "The device may only be configured for a single global "
              + "partition or fixed partitions, but not both.";
          description
            "Prevent both the global partition and fixed partitions
           from being configured at the same time.";
        }
        description
          "Management of ANCP partitions on the device.";
        list partition {
          key "partition-id";
          description "A partition.";
          leaf partition-id {
            type union {
              type enumeration {
                enum "global" {
                  value 0;
                  description
                    "The partition represents a device that is
                   configured to operate without fixed partitions.";
                }
              }
              type partition-id;
            }
            description
              "Uniquely identifies the partition.

             If the device is to use fixed partitions, this leaf must
             be set to a value between 1 and 255; this value will be
             used to associate ANCP messages with this specific
             partition.

             If the device is not to use fixed partitions, i.e., is
             not partitioned, this leaf must be set to 'global', in
             which case no other partition may be configured.

             If the single partition with 'partition-id' set to
             'global' is configured, the PType and Partition ID in
             the Adjacency Message must be being set to 0 (no
             partition) and 0 respectively.";
            reference
              "RFC 6320 section 3.5.2.4.2";

          }

          leaf technology {
            type identityref {
              base access-line-technology;
            }
            mandatory true;
            description
              "The access line technology supported by the partition.";
          }

          container sessions {
            description
              "Management of ANCP sessions.";
            list session {
              key "name";
              description "An ANCP session.";
              leaf name {
                type string;
                description
                  "An arbitrary name for the session.";
              }

              leaf enable {
                if-feature session-administrative-state;
                type boolean;
                default "true";
                description
                  "The desired administrative state of the session.";
              }

              leaf protocol-version {
                if-feature bbf-ancp:protocol-version;
                type protocol-version;
                default "rfc6320";
                description
                  "The ANCP protocol version to be used by the
                 session.";
                reference
                  "RFC 6320 section 3.5.1";

              }

              leaf-list capability {
                type identityref {
                  base capabilities;
                }
                min-elements 1;
                description
                  "The common set of ANCP capabilities supported by this
                 session. At least one capability must be configured.

                 The final negotiated value may be different to the
                 intended value and is to be found by operational
                 data.";
                reference
                  "RFC 6320 section 3.5.1 (Capability Fields).";

              }

              leaf oper-state {
                type enumeration {
                  enum "down" {
                    value 0;
                    description
                      "The operational state of the session is down and
                     it is non-operational.";
                  }
                  enum "up" {
                    value 1;
                    description
                      "The operational state of the session is up and
                     it is operational.";
                  }
                }
                config false;
                mandatory true;
                description
                  "The operational state of the session. A session is
                 deemed to be 'up', only when adjacency is
                 established ('adjacency-state' is set to 'estab').";
              }

              container access-node {
                description
                  "Configuration relevant to the AN side of the ANCP
                 session.";
                container name-source {
                  presence
                    "Enables selection of the source of the name to use
                   to generate the Sender Name to be used for this
                   ANCP session.

                   If this container is not present, the system will
                   use the a system MAC address to generate the
                   Sender Name.";
                  description
                    "Configuration of the source to use to generate the
                   Sender Name to be used for this ANCP session.";
                  choice which-name-source {
                    mandatory true;
                    description
                      "Configures which source to use to generate the
                     Sender Name to use to identify the session at
                     the AN to the NAS.";
                    reference
                      "RFC 6320 section 3.5.1 (Sender Name).";

                    case use-mac-address {
                      description
                        "Configures the session to use a system MAC
                       address to generate the Sender Name to be
                       inserted into ANCP messages to identify the
                       AN.";
                      leaf use-mac-address {
                        type empty;
                        description
                          "Configures the session to use a system MAC
                         address to generate the Sender Name to be
                         inserted into ANCP messages to identify the
                         AN.";
                      }
                    }  // case use-mac-address
                  }  // choice which-name-source
                }  // container name-source

                uses peer-operational-parameters;

                leaf address {
                  type inet:ip-address;
                  config false;
                  mandatory true;
                  description
                    "The IP address of the AN.";
                }

                leaf port {
                  type inet:port-number;
                  config false;
                  mandatory true;
                  description
                    "The IP port of the AN.";
                }
              }  // container access-node

              container network-access-server {
                description
                  "Configuration relevant to the Network Access Server
                 (NAS) side of the ANCP session.";
                uses peer-operational-parameters;

                choice transport {
                  mandatory true;
                  description
                    "Selects the transport for ANCP.";
                  case tcp {
                    description
                      "Configures TCP as the transport for ANCP.";
                    reference
                      "RFC 6320 section 3.2";

                    container tcp {
                      description
                        "Contains TCP-specific configuration for ANCP.";
                      leaf address {
                        type inet:host;
                        mandatory true;
                        description
                          "The IP address or the DNS domain name of the
                         NAS.";
                      }

                      leaf port {
                        if-feature tcp-port;
                        type inet:port-number;
                        default "6068";
                        description
                          "The IP port of the NAS.";
                        reference
                          "RFC 6320 section 3.2";

                      }
                    }  // container tcp
                  }  // case tcp
                }  // choice transport

                leaf connection-state {
                  if-feature nas-connection-state;
                  type enumeration {
                    enum "opening" {
                      value 0;
                      description
                        "The session is attempting to establish a
                       connection to the NAS.";
                    }
                    enum "established" {
                      value 1;
                      description
                        "A connection to the NAS is established.";
                    }
                    enum "closed" {
                      value 2;
                      description
                        "The session to the NAS has been closed by the
                       ANCP Agent on the AN, for example, due to a
                       malfunction with the Adjacency Protocol.";
                    }
                    enum "malfunction" {
                      value 3;
                      description
                        "A connection to the configured NAS could not
                       be established.

                       A corresponding alarm will be raised, if
                       supported.

                       A device may continue to periodically attempt
                       to establish the transport connection, but
                       this is implementation-specific. If the
                       transport connection can be established the
                       alarm will be cleared by the instrumentation.

                       To re-attempt to connect to a configured NAS
                       manually either
                        - modify the configuration
                        - reset the session using the action 'reset',
                          if supported
                        - administratively disable and then enable
                          the session.";
                    }
                    enum "disabled" {
                      value 4;
                      description
                        "The session has been administratively
                       disabled.";
                    }
                  }
                  config false;
                  mandatory true;
                  description
                    "The operational state of the transport connection
                   to the Network Access Server (NAS).";
                }
              }  // container network-access-server

              container adjacency-protocol {
                description
                  "Configuration to manage the adjacency protocol.";
                leaf liveness-timer {
                  type uint8;
                  units "100 milliseconds";
                  default "250";
                  description
                    "The nominal time between periodic adjacency
                   protocol messages.

                   The final negotiated value, which will be constant
                   for the duration of the ANCP session, may be
                   different to the intended value and is to be found
                   by querying state data.";
                  reference
                    "RFC 6320 section 3.5.1 (Timer).";

                }

                leaf adjacency-state {
                  type enumeration {
                    enum "malfunction" {
                      value 0;
                      description
                        "Adjacency could not be established, because of
                       a malfunctioning of the adjacency protocol.

                       This will result in the connection to the NAS
                       being dropped and a corresponding alarm raised,
                       if supported.

                       Further details of the cause of the malfunction
                       will be reported through the data nodes in the
                       container 'malfunction'.

                       To re-attempt to setup adjacency
                       either
                        - modify the configuration
                        - reset the session using the action 'reset',
                          if supported
                        - administratively disable and then enable
                          the session.";
                      reference
                        "RFC 5851 section 4.6.4 R-48.";

                    }
                    enum
                      "synchronization-lost" {
                      value 1;
                      description
                        "Indicates that the AN and NAS are no longer
                       synchronized. This may occur, if
                       - no valid ANCP messages are received in any
                         period of time in excess of three times the
                         value of the negotiated liveness timer;
                       or
                       - a mismatch in adjacency state is detected.

                       A corresponding alarm will be raised, if
                       supported.";
                      reference
                        "RFC 6320 section 3.5.2.7";

                    }
                    enum "estab" {
                      value 2;
                      description
                        "The state ESTAB (established) indicates that
                       the AN has established a session.";
                      reference
                        "RFC 6320 section 3.5.2.2.7";

                    }
                    enum "synrcvd" {
                      value 3;
                      description
                        "The state SYNRCVD (synchronization received)
                       indicates that the AN has received a connection
                       request and sent an acknowledgment.";
                      reference
                        "RFC 6320 section 3.5.2.2.1";

                    }
                    enum "synsent" {
                      value 4;
                      description
                        "The state SYNSENT (synchronization sent)
                       indicates that the AN is waiting for an
                       acknowledgment from the NAS after having sent
                       a connection request.";
                      reference
                        "RFC 6320 section 3.5.2.2.1";

                    }
                    enum "pending" {
                      value 5;
                      description
                        "The setup of an adjacency is pending the
                       establishment of the transport layer.";
                    }
                    enum "disabled" {
                      value 6;
                      description
                        "The session and thus the execution of the
                       Adjacency Protocol has been administratively
                       disabled.";
                    }
                  }
                  config false;
                  mandatory true;
                  description
                    "The operational state of the adjacency protocol.";
                  reference
                    "RFC 6320 section 3.5.2.2";

                }

                leaf partition-id {
                  when
                    "count(/bbf-ancp:ancp/bbf-ancp:partitions"
                      + "/bbf-ancp:partition)>0"
                      + " and "
                      + "not(boolean(/bbf-ancp:ancp"
                      + "/bbf-ancp:partitions"
                      + "/bbf-ancp:partition"
                      + "[bbf-ancp:partition-id='global']))" {
                    description
                      "The use of a Partition ID is only applicable, if
                     the AN has been partitioned.";
                  }
                  if-feature bbf-ancp:partition-id-negotiation;
                  type partition-id;
                  config false;
                  mandatory true;
                  description
                    "The Partition ID used by this session to associate
                   ANCP messages with the partition of the AN managed
                   by this session.

                   The final negotiated value, which will be constant
                   for the duration of the ANCP session, may be
                   different to the Partition ID configured for the
                   partition.";
                  reference
                    "RFC 6320 section 3.5.2.4.2";

                }

                container malfunction {
                  when
                    "../adjacency-state='malfunction'" {
                    description
                      "Only applicable when there is a malfunction in
                     the Adjacency Protocol.";
                  }
                  config false;
                  description
                    "Provides additional information regarding a
                   malfunction encountered with the Adjacency
                   Protocol.";
                  leaf cause {
                    type identityref {
                      base adjacency-malfunction-cause;
                    }
                    mandatory true;
                    description
                      "The cause of the malfunction of the Adjacency
                     Protocol.";
                  }

                  leaf message {
                    type string;
                    description
                      "A string suitable for human display that
                     describes the condition causing the
                     malfunction.";
                  }
                }  // container malfunction
              }  // container adjacency-protocol

              container access-line-identification {
                description
                  "Configure Access Line Identification for ANCP.";
                leaf-list access-line-identification {
                  type enumeration {
                    enum
                      "access-loop-circuit-id" {
                      value 0;
                      description
                        "Add the Access Loop Circuit ID TLV in the ANCP
                       message, i.e., the TLV with type value 0x0001.

                       The value inserted in the TLV is the value
                       defined by the data node '/bbf-subprof:
                       subscriber-profiles/bbf-subprof:subscriber-
                       profile/bbf-subprof:circuit-id' that is
                       associated with the interface, if present. If
                       not present, the value inserted will be
                       generated according to the syntax defined in
                       the leaf 'access-loop-circuit-id'. If this
                       leaf is not present or empty, then an empty
                       TLV will be inserted, i.e., a TLV with
                       Length = 0.";
                      reference
                        "RFC 6320 section 5.1.2.1,
                        TR-101i2 Section 3.9.3.";

                    }
                    enum
                      "access-loop-remote-id" {
                      value 1;
                      description
                        "Add the Access Loop Remote ID TLV in the ANCP
                       message, i.e., the TLV with type value 0x0002.

                       The value inserted in the TLV is the value
                       defined by the data node '/bbf-subprof:
                       subscriber-profiles/bbf-subprof:subscriber-
                       profile/bbf-subprof:remote-id' that is
                       associated with the interface, if present. If
                       not present, then an empty TLV will be
                       inserted, i.e., a TLV with Length = 0.";
                      reference
                        "RFC 6320 section 5.1.2.2,
                        TR-101i2 Section 3.9.3.";

                    }
                    enum
                      "access-aggregation-circuit-id-binary" {
                      value 2;
                      description
                        "Add the Access Aggregation Circuit ID Binary
                       TLV in the ANCP message, i.e., the TLV with
                       type value 0x0006.

                       This TLV identifies or partially identifies a
                       specific access line by means of its logical
                       circuit identifier on the NAS side of the AN.
                       It is defined to contain VLAN ID(s).

                       The value of the TLV contains the VLAN IDs of
                       the VLAN tags to be used in data frames sent
                       on a network interface. However, this is not
                       necessarily the same for all data frames
                       coming from a single access line. The
                       selection of which values to use for the
                       VLAN IDs is defined by the value configured
                       via the interface.";
                      reference
                        "RFC 6320 section 5.1.2.3,
                        TR-101i2 Section 3.9.3.";

                    }
                    enum
                      "access-aggregation-circuit-id-ascii" {
                      value 3;
                      description
                        "Add the Access Aggregation Circuit ID ASCII
                       TLV in the ANCP message, i.e., the TLV with
                       type value 0x0003.

                       The value is identified in the same way as the
                       value for the Access Aggregation Circuit ID
                       Binary TLV.

                       The difference for the TLV value is the
                       produced format, i.e., for the Access
                       Aggregation Circuit Id ASCII TLV the format is
                       in ASCII and based on a syntax configured in
                       the leaf 'access-aggregation-circuit-id-ascii'.
                       If this leaf is empty, then an empty TLV will
                       be inserted, i.e., a TLV with Length = 0.";
                      reference
                        "RFC 6320 section 5.1.2.4,
                        TR-101i2 Section 3.9.3.";

                    }
                  }
                  min-elements 1;
                  description
                    "Identifies how to generate / interpret the Access
                   Line Identification TLVs used in ANCP messages.";
                }

                leaf access-loop-circuit-id {
                  type bbf-yang:string-ascii63-or-empty;
                  default "";
                  description
                    "ASCII string identifying the access loop logical
                   port on the user side of the AN. It may contain
                   any characters and variables, e.g.,
                   'Access_Node_ID eth slot/port'.";
                  reference
                    "RFC 6320 section 5.1.2.1 and
                    TR-101 Section 3.9.3.";

                }

                leaf access-aggregation-circuit-id-ascii {
                  type bbf-yang:string-ascii63-or-empty;
                  default "";
                  description
                    "ASCII string identifying or partially identifying
                   a specific access line by means of its logical
                   circuit identifier on the NAS side of the Access
                   Node. As per RFC 6320 it shall contain VLAN IDs
                   similar as the Access Aggregation Circuit ID
                   Binary TLV, but in a format as specified by
                   TR-101.

                   It may contain any characters and variables, e.g.,
                   'S-VID:C-VID'.";
                  reference
                    "RFC 6320 section 5.1.2.4";

                }

                leaf start-numbering-from-zero {
                  type boolean;
                  default "false";
                  description
                    "In case the leaf 'access-loop-circuit-id' or
                   'access-aggregation-circuit-id-ascii' indicates the
                   TLV shall contain a slot, a port or another
                   variable for which the numbering is defined by the
                   AN, then this leaf determines if the numbering
                   MUST start from 0 or 1.";
                  reference
                    "TR-178 - R118";

                }

                leaf use-leading-zeroes {
                  type boolean;
                  default "false";
                  description
                    "In case the leaf 'access-loop-circuit-id' or the
                   'access-aggregation-circuit-id-ascii' contain
                   variables for which the value can be multiple
                   digits, then this leaf determines if the
                   slot/port/VLAN ID numbering MUST use leading 0's
                   or not, i.e., generate a fixed-length string or a
                   string with only meaningful digits.

                   Note that the number of digits used to form the
                   fixed-length string is device specific.
                   A device may use the number of digits as specified
                   in TR-101 Table 2 / TR-156 Table 1 or a device may
                   determine the number of digits by the maximum
                   value for the Slot or a Port identification
                   applicable to the device, i.e., if the maximum
                   value is less than or equal to 9, one digit may
                   be used; if the maximum value is less than or
                   equal to 99, two digits may be used, etc.";
                  reference
                    "TR-178 - R119 and TR-101i2 - R153;
                    TR-101i2 - Table 2 Circuit ID Syntax;
                    TR-156 - Table 1 Port Identification String
                    Elements.";

                }
              }  // container access-line-identification

              container topology-discovery {
                when
                  "../capability='bbf-ancp:topology-discovery'" {
                  description
                    "Only applicable, if the topology discovery
                   capability has been selected.";
                }
                description
                  "Configuration to manage line state reporting for
                 topology discovery.";
                container port-up {
                  description
                    "Configuration to manage line state reporting for
                   the Port Up message.";
                }  // container port-up

                container port-down {
                  description
                    "Configuration to manage line state reporting for
                   the Port Down message.";
                }  // container port-down
              }  // container topology-discovery

              container statistics {
                if-feature bbf-ancp:session-statistics;
                config false;
                description
                  "ANCP statistics for this session.";
                leaf last-established-timestamp {
                  type yang:date-and-time;
                  mandatory true;
                  description
                    "The date and time the session last entered the
                   established state.";
                }

                leaf last-discontinuity-timestamp {
                  type yang:date-and-time;
                  mandatory true;
                  description
                    "The date and time the session last suffered a
                   discontinuity.";
                }

                leaf in-valid-messages {
                  type yang:zero-based-counter32;
                  mandatory true;
                  description
                    "The number of messages that have been received and
                   processed in this session by the AN.

                   All ANCP messages pertaining to this session shall
                   be counted, also including adjacency protocol
                   messages and failure response messages.";
                }

                leaf in-discarded-messages {
                  type yang:zero-based-counter32;
                  mandatory true;
                  description
                    "The number of messages that in this session have
                   been received and discarded for whatever reason by
                   the AN.

                   All ANCP messages pertaining to this session shall
                   be counted, also including adjacency protocol
                   messages and failure response messages.";
                }

                leaf out-messages {
                  type yang:zero-based-counter32;
                  mandatory true;
                  description
                    "The number of messages that have been sent in this
                   session by the AN.

                   All ANCP messages pertaining to this session shall
                   be counted, also including adjacency protocol
                   messages and failure response messages.";
                }

                leaf in-syn {
                  type yang:zero-based-counter32;
                  mandatory true;
                  description
                    "The number of adjacency SYN messages that in this
                   session have been received by the Access Node.";
                }

                leaf in-synack {
                  type yang:zero-based-counter32;
                  mandatory true;
                  description
                    "The number of adjacency SYNACK messages that in
                   this session have been received by the access
                   node.";
                }

                leaf in-ack {
                  type yang:zero-based-counter32;
                  mandatory true;
                  description
                    "The number of adjacency ACK messages that in this
                   session have been received by the Access Node.";
                }

                leaf in-rstack {
                  type yang:zero-based-counter32;
                  mandatory true;
                  description
                    "The number of adjacency RSTACK messages that in
                   this session have been received by the access
                   node.";
                }

                leaf out-syn {
                  type yang:zero-based-counter32;
                  mandatory true;
                  description
                    "The number of adjacency SYN messages that in this
                   session have been transmitted by the Access Node.";
                }

                leaf out-synack {
                  type yang:zero-based-counter32;
                  mandatory true;
                  description
                    "The number of adjacency SYNACK messages that in
                   this session have been transmitted by the access
                   node.";
                }

                leaf out-rstack {
                  type yang:zero-based-counter32;
                  mandatory true;
                  description
                    "The number of adjacency RSTACK messages that in
                   this session have been transmitted by the access
                   node.";
                }

                leaf out-ack {
                  type yang:zero-based-counter32;
                  mandatory true;
                  description
                    "The number of adjacency ACK messages that in this
                   session have been transmitted by the Access Node.";
                }
              }  // container statistics

              container reset {
                when
                  "not(boolean(../enable))"
                    + " or "
                    + "(../enable='true')" {
                  description
                    "If the administrative state of a session is
                   supported, the session must be currently
                   administratively enabled to reset the session.";
                }
                if-feature session-reset;
                description
                  "Provides containment for the action 'reset'.";
                action reset {
                  description
                    "Reset the session.

                   Resetting the session will close the connection to
                   the NAS, if established, and clear any alarms. The
                   session will then restart and attempt to setup
                   adjacency to the NAS.";
                }  // rpc reset
              }  // container reset
            }  // list session
          }  // container sessions

          container port-message-control {
            description
              "Configuration to control the generation of Port Up and
             Port Down messages.";
            choice which-dampening-mechanism {
              if-feature bbf-ancp:port-message-dampening;
              default
                "port-up-port-down-withholding-interval";
              description
                "Selects the dampening mechanism for the sending of
               Port Up and Port Down event messages.";
              case port-up-port-down-withholding-interval {
                description
                  "Configures withholding interval for Port Up and Port
                 Down messages.";
                leaf port-up-port-down-withholding-interval {
                  type union {
                    type enumeration {
                      enum "disabled" {
                        value 0;
                        description
                          "The withholding interval is disabled and
                         all line state changes will be reported
                         to the NAS.";
                      }
                    }
                    type uint16 {
                      range "1..max";
                    }
                  }
                  units "100 milliseconds";
                  default "disabled";
                  description
                    "Configures the dampening mechanism controlling the
                   rate at which Port Up and Port Down messages are
                   sent to the NAS, applying individually to each
                   access line. Specifically, it defines an interval
                   following the sending of a Port Up or Port Down
                   message for a given access line, during which no
                   further Port Up or Port Down message is to be sent
                   to the NAS for that given access line. If, at the
                   end of the withholding interval, there has been a
                   change in line state of the given line to that
                   when the last Port Up or Port Down message was
                   sent for that line, the new line state of that
                   line is reported to the NAS (with the withholding
                   interval for that line applying again).";
                  reference
                    "RFC 6320 section 6.4.1";

                }
              }  // case port-up-port-down-withholding-interval
            }  // choice which-dampening-mechanism
          }  // container port-message-control
        }  // list partition
      }  // container partitions
    }  // grouping ancp-schema

    container ancp {
      description
        "Management of the Access Node Control Protocol (ANCP).";
      uses ancp-schema;
    }  // container ancp
  }  // module bbf-ancp