path: root/doc/rfc/rfc9647.txt

Internet Engineering Task Force (IETF)                   M. Jethanandani
Request for Comments: 9647                                Kloud Services
Category: Standards Track                                       B. Stark
ISSN: 2070-1721                                                     AT&T
                                                            October 2024


                      A YANG Data Model for Babel

Abstract

   This document defines a data model for the Babel routing protocol.
   The data model is defined using the YANG data modeling language.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9647.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Revised BSD License text as described in Section 4.e of the
   Trust Legal Provisions and are provided without warranty as described
   in the Revised BSD License.

Table of Contents

   1.  Introduction
     1.1.  Requirements Language
     1.2.  Tree Diagram Annotations
   2.  Babel Module
     2.1.  Information Model
     2.2.  Tree Diagram
     2.3.  YANG Module
   3.  IANA Considerations
     3.1.  URI Registration
     3.2.  YANG Module Name Registration
   4.  Security Considerations
   5.  References
     5.1.  Normative References
     5.2.  Informative References
   Appendix A.  Tree Diagram and Example Configurations
     A.1.  Complete Tree Diagram
     A.2.  Statistics Gathering Enabled
     A.3.  Automatic Detection of Properties
     A.4.  Override Default Properties
     A.5.  Configuring Other Properties
   Acknowledgements
   Authors' Addresses

1.  Introduction

   This document defines a data model for the Babel routing protocol
   [RFC8966].  The data model is defined using YANG 1.1 [RFC7950] and is
   compatible with Network Management Datastore Architecture (NMDA)
   [RFC8342].  It is based on the Babel information model [RFC9046].
   The data model only includes data nodes that are useful for managing
   Babel over IPv6.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

1.2.  Tree Diagram Annotations

   For a reference to the annotations used in tree diagrams included in
   this document, please see "YANG Tree Diagrams" [RFC8340].

2.  Babel Module

   This document defines a YANG 1.1 [RFC7950] data model for the
   configuration and management of Babel.  The YANG module is based on
   the Babel information model [RFC9046].

2.1.  Information Model

   It's worth noting a few differences between the Babel information
   model and this data module.  The information model mandates the
   definition of some of the attributes, e.g., "babel-implementation-
   version" or the "babel-self-router-id".  These attributes are marked
   as read-only objects in the information module as well as in this
   data module.  However, there is no way in the data module to mandate
   that a read-only attribute be present.  It is up to the
   implementation of this data module to make sure that the attributes
   that are marked "read only" and are mandatory are indeed present.

2.2.  Tree Diagram

   The following diagram illustrates a top-level hierarchy of the model.
   In addition to the version implemented by this device, the model
   contains subtrees on "constants", "interfaces", "mac-key-set",
   "dtls", and "routes".

   module: ietf-babel

     augment /rt:routing/rt:control-plane-protocols
               /rt:control-plane-protocol:
       +--rw babel!
          +--ro version?              string
          +--rw enable                boolean
          +--ro router-id?            binary
          +--ro seqno?                uint16
          +--rw statistics-enabled?   boolean
          +--rw constants
          |     ...
          +--rw interfaces* [reference]
          |     ...
          +--rw mac-key-set* [name]
          |     ...
          +--rw dtls* [name]
          |     ...
          +--ro routes* [prefix]
                ...

   The "interfaces" subtree describes attributes such as the "interface"
   object that is being referenced; the type of link, e.g., wired,
   wireless, or tunnel, as enumerated by "metric-algorithm" and "split-
   horizon"; and whether the interface is enabled or not.

   The "constants" subtree describes the UDP port used for sending and
   receiving Babel messages and the multicast group used to send and
   receive announcements on IPv6.

   The "routes" subtree describes objects such as the prefix for which
   the route is advertised, a reference to the neighboring route, and
   the "next-hop" address.

   Finally, for security, two subtrees are defined to contain Message
   Authentication Code (MAC) keys and DTLS certificates.  The "mac-key-
   set" subtree contains keys used with the MAC security mechanism.  The
   boolean flag "default-apply" indicates whether the set of MAC keys is
   automatically applied to new interfaces.  The "dtls" subtree contains
   certificates used with the DTLS security mechanism.  Similar to the
   MAC mechanism, the boolean flag "default-apply" indicates whether the
   set of DTLS certificates is automatically applied to new interfaces.

2.3.  YANG Module

   This YANG module augments the YANG routing management module
   [RFC8349] to provide a common framework for all routing subsystems.
   By augmenting the module, it provides a common building block for
   routes and Routing Information Bases (RIBs).  It also has a reference
   to an interface defined by "A YANG Data Model for Interface
   Management" [RFC8343].

   A router running the Babel routing protocol can sometimes determine
   the parameters it needs to use for an interface based on the
   interface name.  For example, it can detect that eth0 is a wired
   interface and that wlan0 is a wireless interface.  This is not true
   for a tunnel interface, where the link parameters need to be
   configured explicitly.

   For a wired interface, it will assume "two-out-of-three" is set for
   "metric-algorithm" and "split-horizon" is set to true.  On the other
   hand, for a wireless interface, it will assume "etx" is set for
   "metric-algorithm" and "split-horizon" is set to false.  However, if
   the wired link is connected to a wireless radio, the values can be
   overridden by setting "metric-algorithm" to "etx" and "split-horizon"
   to false.  Similarly, an interface that is a metered 3G link and is
   used for fallback connectivity needs much higher default time
   constants, e.g., "mcast-hello-interval" and "update-interval", in
   order to avoid carrying control traffic as much as possible.

   In addition to the modules used above, this module imports
   definitions from "Common YANG Data Types" [RFC6991] and references
   "HMAC: Keyed-Hashing for Message Authentication" [RFC2104], "Using
   HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512 with IPsec" [RFC4868],
   "Textual Encodings of PKIX, PKCS, and CMS Structures" [RFC7468], "The
   BLAKE2 Cryptographic Hash and Message Authentication Code (MAC)"
   [RFC7693], "Network Configuration Access Control Model" [RFC8341],
   "The Babel Routing Protocol" [RFC8966], "MAC Authentication for the
   Babel Routing Protocol" [RFC8967], "Babel Information Model"
   [RFC9046], "The Datagram Transport Layer Security (DTLS) Protocol
   Version 1.3" [RFC9147], and "YANG Data Types and Groupings for
   Cryptography" [RFC9640].

   <CODE BEGINS> file "ietf-babel@2024-10-10.yang"
   module ietf-babel {
     yang-version 1.1;
     namespace "urn:ietf:params:xml:ns:yang:ietf-babel";
     prefix babel;

     import ietf-yang-types {
       prefix yang;
       reference
         "RFC 6991: Common YANG Data Types";
     }
     import ietf-inet-types {
       prefix inet;
       reference
         "RFC 6991: Common YANG Data Types";
     }
     import ietf-interfaces {
       prefix if;
       reference
         "RFC 8343: A YANG Data Model for Interface Management";
     }
     import ietf-routing {
       prefix rt;
       reference
         "RFC 8349: A YANG Data Model for Routing Management (NMDA
          Version)";
     }
     import ietf-crypto-types {
       prefix ct;
       reference
         "RFC 9640: YANG Data Types and Groupings
          for Cryptography";
     }
     import ietf-netconf-acm {
       prefix nacm;
       reference
         "RFC 8341: Network Configuration Access Control Model";
     }

     organization
       "IETF Babel routing protocol Working Group";

     contact
       "WG Web:  https://datatracker.ietf.org/wg/babel/
        WG List: babel@ietf.org

        Editor: Mahesh Jethanandani
                mjethanandani@gmail.com
        Editor: Barbara Stark
                bs7652@att.com";

     description
       "This YANG module defines a model for the Babel routing
        protocol.

        The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL
        NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED',
        'MAY', and 'OPTIONAL' in this document are to be interpreted as
        described in BCP 14 (RFC 2119) (RFC 8174) when, and only when,
        they appear in all capitals, as shown here.

        Copyright (c) 2024 IETF Trust and the persons identified as
        authors of the code.  All rights reserved.

        Redistribution and use in source and binary forms, with or
        without modification, is permitted pursuant to, and subject to
        the license terms contained in, the Revised BSD License set
        forth in Section 4.c of the IETF Trust's Legal Provisions
        Relating to IETF Documents
        (https://trustee.ietf.org/license-info).

        This version of this YANG module is part of RFC 9647
        (https://www.rfc-editor.org/info/rfc9647); see the RFC itself
        for full legal notices.";

     revision 2024-10-10 {
       description
         "Initial version.";
       reference
         "RFC 9647: A YANG Data Model for Babel";
     }

     /*
      * Features
      */

     feature two-out-of-three-supported {
       description
         "This implementation supports the '2-out-of-3'
          computation algorithm.";
     }

     feature etx-supported {
       description
         "This implementation supports the Expected Transmission Count
          (ETX) metric computation algorithm.";
     }

     feature mac-supported {
       description
         "This implementation supports MAC-based security.";
       reference
         "RFC 8967: MAC Authentication for the Babel Routing
          Protocol";
     }

     feature dtls-supported {
       description
         "This implementation supports DTLS-based security.";
       reference
         "RFC 8968: Babel Routing Protocol over Datagram
          Transport Layer Security";
     }

     feature hmac-sha256-supported {
       description
         "This implementation supports the HMAC-SHA256 MAC algorithm.";
       reference
         "RFC 8967: MAC Authentication for the Babel Routing
          Protocol";
     }

     feature blake2s-supported {
       description
         "This implementation supports BLAKE2s MAC algorithms.";
       reference
         "RFC 8967: MAC Authentication for the Babel Routing
          Protocol";
     }

     feature x-509-supported {
       description
         "This implementation supports the X.509 certificate type.";
       reference
         "RFC 8968: Babel Routing Protocol over Datagram
          Transport Layer Security";
     }

     feature raw-public-key-supported {
       description
         "This implementation supports the raw public key certificate
          type.";
       reference
         "RFC 8968: Babel Routing Protocol over Datagram
          Transport Layer Security";
     }

     /*
      * Identities
      */

     identity metric-comp-algorithms {
       description
         "Base identity from which all Babel metric computation
          algorithms MUST be derived.";
     }

     identity two-out-of-three {
       if-feature "two-out-of-three-supported";
       base metric-comp-algorithms;
       description
         "2-out-of-3 algorithm.";
       reference
         "RFC 8966: The Babel Routing Protocol, Section A.2.1";
     }

     identity etx {
       if-feature "etx-supported";
       base metric-comp-algorithms;
       description
         "Expected Transmission Count (ETX) metric computation
          algorithm.";
       reference
         "RFC 8966: The Babel Routing Protocol, Section A.2.2";
     }

     /*
      * Babel MAC algorithms identities.
      */

     identity mac-algorithms {
       description
         "Base identity for all Babel MAC algorithms.";
     }

     identity hmac-sha256 {
       if-feature "mac-supported";
       if-feature "hmac-sha256-supported";
       base mac-algorithms;
       description
         "HMAC-SHA256 algorithm supported.";
       reference
         "RFC 4868: Using HMAC-SHA-256, HMAC-SHA-384, and HMAC-SHA-512
          with IPsec";
     }

     identity blake2s {
       if-feature "mac-supported";
       if-feature "blake2s-supported";
       base mac-algorithms;
       description
         "BLAKE2s algorithms supported. Specifically, BLAKE2-128 is
          supported.";
       reference
         "RFC 7693: The BLAKE2 Cryptographic Hash and Message
          Authentication Code (MAC)";
     }

     /*
      * Babel Cert Types
      */

     identity dtls-cert-types {
       description
         "Base identity for Babel DTLS certificate types.";
     }

     identity x-509 {
       if-feature "dtls-supported";
       if-feature "x-509-supported";
       base dtls-cert-types;
       description
         "X.509 certificate type.";
     }

     identity raw-public-key {
       if-feature "dtls-supported";
       if-feature "raw-public-key-supported";
       base dtls-cert-types;
       description
         "Raw public key certificate type.";
     }

     /*
      * Babel routing protocol identity.
      */

     identity babel {
       base rt:routing-protocol;
       description
         "Babel routing protocol";
     }

     /*
      * Groupings
      */

     grouping routes {
       list routes {
         key "prefix";
         config false;

         leaf prefix {
           type inet:ip-prefix;
           description
             "Prefix (expressed in ip-address/prefix-length format) for
              which this route is advertised.";
           reference
             "RFC 9046: Babel Information Model, Section 3.6";
         }

         leaf router-id {
           type binary {
             length "8";
           }
           description
             "router-id of the source router for which this route is
              advertised.";
           reference
             "RFC 9046: Babel Information Model, Section 3.6";
         }

         leaf neighbor {
           type leafref {
             path "/rt:routing/rt:control-plane-protocols/"
                + "rt:control-plane-protocol/babel/interfaces/"
                + "neighbor-objects/neighbor-address";
           }
           description
             "Reference to the neighbor-objects entry for the neighbor
              that advertised this route.";
           reference
             "RFC 9046: Babel Information Model, Section 3.6";
         }

         leaf received-metric {
           type union {
             type enumeration {
               enum null {
                 description
                   "Route was not received from a neighbor.";
               }
             }
             type uint16;
           }
           description
             "The metric with which this route was advertised by the
              neighbor, or maximum value (infinity) to indicate the
              route was recently retracted and is temporarily
              unreachable. This metric will be NULL if the
              route was not received from a neighbor but instead was
              injected through means external to the Babel routing
              protocol. At least one of calculated-metric or
              received-metric MUST be non-NULL.";
           reference
             "RFC 9046: Babel Information Model, Section 3.6
              RFC 8966: The Babel Routing Protocol, Section 2.1";
         }

         leaf calculated-metric {
           type union {
             type enumeration {
               enum null {
                 description
                   "Route has not been calculated.";
               }
             }
             type uint16;
           }
           description
             "A calculated metric for this route. How the metric is
              calculated is implementation specific. Maximum value
              (infinity) indicates the route was recently retracted
              and is temporarily unreachable. At least one of
              calculated-metric or received-metric MUST be non-NULL.";
           reference
             "RFC 9046: Babel Information Model, Section 3.6
              RFC 8966: The Babel Routing Protocol, Section 2.1";
         }

         leaf seqno {
           type uint16;
           description
             "The sequence number with which this route was
              advertised.";
           reference
             "RFC 9046: Babel Information Model, Section 3.6";
         }

         leaf next-hop {
           type union {
             type enumeration {
               enum null {
                 description
                   "Route has no next-hop address.";
               }
             }
             type inet:ip-address;
           }
           description
             "The next-hop address of this route. This will be NULL
              if this route has no next-hop address.";
           reference
             "RFC 9046: Babel Information Model, Section 3.6";
         }

         leaf feasible {
           type boolean;
           description
             "A boolean flag indicating whether this route is
              feasible.";
           reference
             "RFC 9046: Babel Information Model, Section 3.6
              RFC 8966, The Babel Routing Protocol, Section 3.5.1";
         }

         leaf selected {
           type boolean;
           description
             "A boolean flag indicating whether this route is selected,
              i.e., whether it is currently being used for forwarding
              and is being advertised.";
           reference
             "RFC 9046: Babel Information Model, Section 3.6";
         }
         description
           "A set of babel-route-obj objects. Contains routes known to
            this node.";
         reference
           "RFC 9046: Babel Information Model, Section 3.6";
       }
       description
         "Common grouping for routing used in RIB.";
     }

     /*
      * Data model
      */

     augment "/rt:routing/rt:control-plane-protocols/"
           + "rt:control-plane-protocol" {
       when "derived-from-or-self(rt:type, 'babel')" {
         description
           "Augmentation is valid only when the instance of the routing
            type is of type 'babel'.";
       }
       description
         "Augments the routing module to support a common structure
          between routing protocols.";
       reference
         "RFC 8349: A YANG Data Model for Routing Management (NMDA
          Version)";

       container babel {
         presence "A Babel container.";
         description
           "Babel information objects.";
         reference
           "RFC 9046: Babel Information Model, Section 3";

         leaf version {
           type string;
           config false;
           description
             "The name and version of this implementation of the Babel
              protocol.";
           reference
             "RFC 9046: Babel Information Model, Section 3.1";
         }

         leaf enable {
           type boolean;
           mandatory true;
           description
             "When written, it configures whether the protocol should be
              enabled. A read from the <running> or <intended> datastore
              therefore indicates the configured administrative value of
              whether the protocol is enabled or not.

              A read from the <operational> datastore indicates whether
              the protocol is actually running or not, i.e., it
              indicates the operational state of the protocol.";
           reference
             "RFC 9046: Babel Information Model, Section 3.1";
         }

         leaf router-id {
           type binary;
           must '../enable = "true"';
           config false;
           description
             "Every Babel speaker is assigned a router-id, which is an
              arbitrary string of 8 octets that is assumed to be unique
              across the routing domain.

              The router-id is valid only if the protocol is enabled,
              at which time a non-zero value is assigned.";
           reference
             "RFC 9046: Babel Information Model, Section 3.1
              RFC 8966: The Babel Routing Protocol, Section 3";
         }

         leaf seqno {
           type uint16;
           config false;
           description
             "Sequence number included in route updates for routes
              originated by this node.";
           reference
             "RFC 9046: Babel Information Model, Section 3.1";
         }

         leaf statistics-enabled {
           type boolean;
           description
             "Indicates whether statistics collection is enabled
              ('true') or disabled ('false') on all interfaces.
              On transition to enabled, existing statistics
              values are not cleared and will be incremented as
              new packets are counted.";
         }

         container constants {
           description
             "Babel constants object.";
           reference
             "RFC 9046: Babel Information Model, Section 3.1";

           leaf udp-port {
             type inet:port-number;
             default "6696";
             description
               "UDP port for sending and receiving Babel messages. The
                default port is 6696.";
             reference
               "RFC 9046: Babel Information Model, Section 3.2";
           }

           leaf mcast-group {
             type inet:ip-address;
             default "ff02::1:6";
             description
               "Multicast group for sending and receiving multicast
                announcements on IPv6.";
             reference
               "RFC 9046: Babel Information Model, Section 3.2";
           }
         }

         list interfaces {
           key "reference";

           description
             "A set of Babel interface objects.";
           reference
             "RFC 9046: Babel Information Model, Section 3.3";

           leaf reference {
             type if:interface-ref;
             description
               "References the name of the interface over which Babel
                packets are sent and received.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3";
           }

           leaf enable {
             type boolean;
             default "true";
             description
               "If 'true', Babel sends and receives messages on this
                interface. If 'false', Babel messages received on
                this interface are ignored and none are sent.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3";
           }

           leaf metric-algorithm {
             type identityref {
               base metric-comp-algorithms;
             }
             mandatory true;
             description
               "Indicates the metric computation algorithm used on this
                interface. The value MUST be one of those identities
                based on 'metric-comp-algorithms'.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3";
           }

           leaf split-horizon {
             type boolean;
             description
               "Indicates whether or not the split-horizon optimization
                is used when calculating metrics on this interface.
                A value of 'true' indicates the split-horizon
                optimization is used.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3";
           }

           leaf mcast-hello-seqno {
             type uint16;
             config false;
             description
               "The current sequence number in use for multicast Hellos
                sent on this interface.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3";
           }

           leaf mcast-hello-interval {
             type uint16;
             units "centiseconds";
             description
               "The current multicast Hello interval in use for Hellos
                sent on this interface.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3";
           }

           leaf update-interval {
             type uint16;
             units "centiseconds";
             description
               "The current update interval in use for this interface.
                Units are centiseconds.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3";
           }

           leaf mac-enable {
             type boolean;
             description
               "Indicates whether the MAC security mechanism is enabled
                ('true') or disabled ('false').";
             reference
               "RFC 9046: Babel Information Model, Section 3.3";
           }

           leaf-list mac-key-sets {
             type leafref {
               path "../../mac-key-set/name";
             }
             description
               "List of references to the MAC entries that apply
                to this interface. When an interface instance is
                created, all MAC instances with default-apply 'true'
                will be included in this list.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3";
           }

           leaf mac-verify {
             type boolean;
             description
               "A boolean flag indicating whether MACs in
                incoming Babel packets are required to be present and
                are verified.  If this parameter is 'true', incoming
                packets are required to have a valid MAC.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3";
           }

           leaf dtls-enable {
             type boolean;
             description
               "Indicates whether the DTLS security mechanism is enabled
                ('true') or disabled ('false').";
             reference
               "RFC 9046: Babel Information Model, Section 3.3";
           }

           leaf-list dtls-certs {
             type leafref {
               path "../../dtls/name";
             }
             description
               "List of references to the dtls entries that apply to
                this interface.  When an interface instance
                is created, all dtls instances with default-apply
                'true' will be included in this list.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3";
           }

           leaf dtls-cached-info {
             type boolean;
             description
               "Indicates whether the cached_info extension is enabled.
                The extension is enabled for inclusion in ClientHello
                and ServerHello messages if the value is 'true'.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3
                RFC 8968: Babel Routing Protocol over
                Datagram Transport Layer Security, Appendix A";
           }

           leaf-list dtls-cert-prefer {
             type leafref {
               path "../../dtls/certs/type";
             }
             ordered-by user;
             description
               "List of supported certificate types, in order of
                preference. The values MUST be the 'type' attribute
                in the list 'certs' of the list 'dtls'
                (../../dtls/certs/type). This list is used to populate
                the server_certificate_type extension in a ClientHello.
                Values that are present in at least one instance in the
                certs object under dtls of a referenced dtls instance
                and that have a non-empty private key will be used to
                populate the client_certificate_type extension in a
                ClientHello.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3
                RFC 8968: Babel Routing Protocol over
                Datagram Transport Layer Security, Appendix A";
           }

           leaf packet-log-enable {
             type boolean;
             description
               "If 'true', logging of babel packets received on this
                interface is enabled; if 'false', babel packets are
                not logged.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3";
           }

           leaf packet-log {
             type inet:uri;
             config false;
             description
               "A reference or url link to a file that contains a
                timestamped log of packets received and sent on
                udp-port on this interface. The [libpcap] file
                format with .pcap file extension SHOULD be supported for
                packet log files. Logging is enabled / disabled by
                packet-log-enable.";
             reference
               "RFC 9046: Babel Information Model, Section 3.3
                libpcap: Libpcap File Format, Wireshark Foundation";
           }

           container statistics {
             config false;
             description
               "Statistics collection object for this interface.";
             reference
               "RFC 9046: Babel Information Model, Section 3.4";

             leaf discontinuity-time {
               type yang:date-and-time;
               mandatory true;
               description
                 "The time on the most recent occasion at which any one
                  or more of counters suffered a discontinuity. If no
                  such discontinuities have occurred since the last
                  re-initialization of the local management subsystem,
                  then this node contains the time the local management
                  subsystem re-initialized itself.";
             }

             leaf sent-mcast-hello {
               type yang:counter32;
               description
                 "A count of the number of multicast Hello packets sent
                  on this interface.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.4";
             }

             leaf sent-mcast-update {
               type yang:counter32;
               description
                 "A count of the number of multicast update packets sent
                  on this interface.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.4";
             }

             leaf sent-ucast-hello {
               type yang:counter32;
               description
                 "A count of the number of unicast Hello packets sent
                  on this interface.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.4";
             }

             leaf sent-ucast-update {
               type yang:counter32;
               description
                 "A count of the number of unicast update packets sent
                  on this interface.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.4";
             }

             leaf sent-ihu {
               type yang:counter32;
               description
                 "A count of the number of 'I Heard You' (IHU) packets
                  sent on this interface.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.4";
             }

             leaf received-packets {
               type yang:counter32;
               description
                 "A count of the number of Babel packets received on
                  this interface.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.4";
             }

             action reset {
               description
                 "The information model (RFC 9046) defines reset
                  action as a system-wide reset of Babel statistics.
                  In YANG, the reset action is associated with the
                  container where the action is defined. In this case,
                  the action is associated with the statistics container
                  inside an interface. The action will therefore
                  reset statistics at an interface level.

                  Implementations that want to support a system-wide
                  reset of Babel statistics need to call this action
                  for every instance of the interface.";
               reference
                 "RFC 9046: Babel Information Model";

               input {
                 leaf reset-at {
                   type yang:date-and-time;
                   description
                     "The time when the reset was issued.";
                 }
               }

               output {
                 leaf reset-finished-at {
                   type yang:date-and-time;
                   description
                     "The time when the reset finished.";
                 }
               }
             }
           }

           list neighbor-objects {
             key "neighbor-address";
             config false;
             description
               "A set of babel neighbor objects.";
             reference
               "RFC 9046: Babel Information Model, Section 3.5";

             leaf neighbor-address {
               type inet:ip-address;
               description
                 "The IPv4 or IPv6 address from which the neighbor sends
                  packets.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.5";
             }

             leaf hello-mcast-history {
               type string;
               description
                 "The multicast Hello history of whether or not the
                  multicast Hello packets prior to exp-mcast-
                  hello-seqno were received, with a '1' for the most
                  recent Hello placed in the most significant bit and
                  prior Hellos shifted right (with '0' bits placed
                  between prior Hellos and the most recent Hello for any
                  Hellos not received); represented as a string of
                  hex digits encoded in utf-8. A bit that is set
                  indicates that the corresponding Hello was received,
                  and a bit that is cleared indicates that the
                  corresponding Hello was not received.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.5";
             }

             leaf hello-ucast-history {
               type string;
               description
                 "The unicast Hello history of whether or not the
                  unicast Hello packets prior to exp-ucast-hello-seqno
                  were received, with a '1' for the most
                  recent Hello placed in the most significant bit and
                  prior Hellos shifted right (with '0' bits placed
                  between prior Hellos and the most recent Hello for any
                  Hellos not received); represented as a string using
                  hex digits encoded in utf-8 where a '1' bit = Hello
                  received and a '0' bit = Hello not received.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.5";
             }

             leaf txcost {
               type int32;
               default "0";
               description
                 "Transmission cost value from the last IHU packet
                  received from this neighbor, or maximum value
                  (infinity) to indicate the IHU hold timer for this
                  neighbor has an expired description.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.5";
             }

             leaf exp-mcast-hello-seqno {
               type union {
                 type enumeration {
                   enum null {
                     description
                       "Multicast Hello packets are not expected, or
                        processing of multicast packets is not
                        enabled.";
                   }
                 }
                 type uint16;
               }
               description
                 "Expected multicast Hello sequence number of next Hello
                  to be received from this neighbor; if multicast Hello
                  packets are not expected, or processing of multicast
                  packets is not enabled, this MUST be NULL.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.5";
             }

             leaf exp-ucast-hello-seqno {
               type union {
                 type enumeration {
                   enum null {
                     description
                       "Unicast Hello packets are not expected, or
                        processing of unicast packets is not enabled.";
                   }
                 }
                 type uint16;
               }
               default "null";
               description
                 "Expected unicast Hello sequence number of next Hello
                  to be received from this neighbor; if unicast Hello
                  packets are not expected, or processing of unicast
                  packets is not enabled, this MUST be NULL.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.5";
             }

             leaf ucast-hello-seqno {
               type union {
                 type enumeration {
                   enum null {
                     description
                       "Unicast Hello packets are not being sent.";
                   }
                 }
                 type uint16;
               }
               default "null";
               description
                 "The current sequence number in use for unicast Hellos
                  sent to this neighbor. If unicast Hellos are not being
                  sent, this MUST be NULL.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.5";
             }

             leaf ucast-hello-interval {
               type uint16;
               units "centiseconds";
               description
                 "The current interval in use for unicast Hellos sent to
                  this neighbor. Units are centiseconds.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.5";
             }

             leaf rxcost {
               type uint16;
               description
                 "Reception cost calculated for this neighbor. This
                  value is usually derived from the Hello history, which
                  may be combined with other data, such as statistics
                  maintained by the link layer. The rxcost is sent to a
                  neighbor in each IHU.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.5";
             }

             leaf cost {
               type int32;
               description
                 "Link cost is computed from the values maintained in
                  the neighbor table. The statistics are kept in the
                  neighbor table about the reception of Hellos, and the
                  txcost is computed from received IHU packets.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.5";
             }
           }
         }

         list mac-key-set {
           key "name";

           description
             "A MAC key set object. If this object is implemented, it
              provides access to parameters related to the MAC security
              mechanism.";
           reference
             "RFC 9046: Babel Information Model, Section 3.7";

           leaf name {
             type string;
             description
               "A string that uniquely identifies the MAC object.";
           }

           leaf default-apply {
             type boolean;
             description
               "A boolean flag indicating whether this object
                instance is applied to all new interfaces, by default.
                If 'true', this instance is applied to new babel-
                interfaces instances at the time they are created
                by including it in the mac-key-sets list under
                the interface. If 'false', this instance is not applied
                to new interface instances when they are created.";
             reference
               "RFC 9046: Babel Information Model, Section 3.7";
           }

           list keys {
             key "name";
             min-elements 1;
             description
               "A set of keys objects.";
             reference
               "RFC 9046: Babel Information Model, Section 3.8";

             leaf name {
               type string;
               description
                 "A unique name for this MAC key that can be used to
                  identify the key in this object instance since the
                  key value is not allowed to be read. This value can
                  only be provided when this instance is created and is
                  not subsequently writable.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.8";
             }

             leaf use-send {
               type boolean;
               mandatory true;
               description
                 "Indicates whether this key value is used to compute a
                  MAC and include that MAC in the sent Babel packet. A
                  MAC for sent packets is computed using this key if the
                  value is 'true'. If the value is 'false', this key is
                  not used to compute a MAC to include in sent Babel
                  packets.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.8";
             }

             leaf use-verify {
               type boolean;
               mandatory true;
               description
                 "Indicates whether this key value is used to verify
                  incoming Babel packets. This key is used to verify
                  incoming packets if the value is 'true'. If the value
                  is 'false', no MAC is computed from this key for
                  comparing an incoming packet.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.8";
             }

             leaf value {
               nacm:default-deny-all;
               type binary;
               mandatory true;
               description
                 "The value of the MAC key.

                  This value is of a length suitable for the associated
                  babel-mac-key-algorithm.  If the algorithm is based on
                  the Hashed Message Authentication Code (HMAC)
                  construction (RFC 2104), the length MUST be between 0
                  and an upper limit that is at least the size of the
                  output length (where the 'HMAC-SHA256' output length
                  is 32 octets as described in RFC 4868). Longer lengths
                  MAY be supported but are not necessary if the
                  management system has the ability to generate a
                  suitably random value (e.g., by randomly generating a
                  value or by using a key derivation technique as
                  recommended in the security considerations of RFC
                  8967. If the algorithm is 'BLAKE2s-128', the length
                  MUST be between 0 and 32 bytes inclusive as specified
                  by RFC 7693.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.8
                  RFC 2104: HMAC: Keyed-Hashing for Message
                            Authentication
                  RFC 4868: Using HMAC-SHA-256, HMAC-SHA-384, and
                            HMAC-SHA-512 with IPsec
                  RFC 7693: The BLAKE2 Cryptographic Hash and Message
                            Authentication Code (MAC)
                  RFC 8967:  MAC Authentication for Babel";
             }

             leaf algorithm {
               type identityref {
                 base mac-algorithms;
               }
               mandatory true;
               description
                 "The MAC algorithm used with this key. The
                  value MUST be one of the identities
                  listed with the base of 'mac-algorithms'.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.8";
             }

             action test {
               description
                 "An operation that allows the MAC key and MAC
                  algorithm to be tested to see if they produce an
                  expected outcome. Input to this operation is a
                  binary string and a calculated MAC (also in the
                  format of a binary string) for the binary string.
                  The implementation is expected to create a MAC over
                  the binary string using the value and algorithm.
                  The output of this operation is a binary indication
                  that the calculated MAC matched the input MAC
                  ('true') or the MACs did not match ('false').";
               reference
                 "RFC 9046: Babel Information Model, Section 3.8";

               input {
                 leaf test-string {
                   type binary;
                   mandatory true;
                   description
                     "Input to this operation is a binary string.
                      The implementation is expected to create
                      a MAC over this string using the value and
                      the algorithm defined as part of the
                      mac-key-set.";
                   reference
                     "RFC 9046: Babel Information Model, Section 3.8";
                 }

                 leaf mac {
                   type binary;
                   mandatory true;
                   description
                     "Input to this operation includes a MAC.
                      The implementation is expected to calculate a MAC
                      over the string using the value and algorithm of
                      this key object and compare its calculated MAC to
                      this input MAC.";
                   reference
                     "RFC 9046: Babel Information Model, Section 3.8";
                 }
               }

               output {
                 leaf indication {
                   type boolean;
                   mandatory true;
                   description
                     "The output of this operation is a binary
                      indication that the calculated MAC matched the
                      input MAC ('true') or the MACs did not match
                      ('false').";
                   reference
                     "RFC 9046: Babel Information Model, Section 3.8";
                 }
               }
             }
           }
         }

         list dtls {
           key "name";

           description
             "A dtls object. If this object is implemented,
              it provides access to parameters related to the DTLS
              security mechanism.";
           reference
             "RFC 9046: Babel Information Model, Section 3.9";

           leaf name {
             type string;
             description
               "A string that uniquely identifies a dtls object.";
           }

           leaf default-apply {
             type boolean;
             mandatory true;
             description
               "A boolean flag indicating whether this object
                instance is applied to all new interfaces, by default.
                If 'true', this instance is applied to new interface
                instances at the time they are created by including it
                in the dtls-certs list under the interface. If 'false',
                this instance is not applied to new interface
                instances when they are created.";
             reference
               "RFC 9046: Babel Information Model, Section 3.9";
           }

           list certs {
             key "name";

             min-elements 1;
             description
               "A set of cert objects. This contains
                both certificates for this implementation to present
                for authentication and to accept from others.
                Certificates with a non-empty private key
                can be presented by this implementation for
                authentication.";
             reference
               "RFC 9046: Babel Information Model, Section 3.10";

             leaf name {
               type string;
               description
                 "A unique name for this certificate that can be
                  used to identify the certificate in this object
                  instance, since the value is too long to be useful
                  for identification. This value MUST NOT be empty
                  and can only be provided when this instance is created
                  (i.e., it is not subsequently writable).";
               reference
                 "RFC 9046: Babel Information Model, Section 3.10";
             }

             leaf value {
               nacm:default-deny-write;
               type string;
               mandatory true;
               description
                 "The certificate in Privacy-Enhanced Mail (PEM) format
                  (RFC 7468). This value can only be provided when this
                  instance is created and is not subsequently
                  writable.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.10
                  RFC 7468: Textual Encodings of PKIX, PKCS, and CMS
                            Structures";
             }

             leaf type {
               nacm:default-deny-write;
               type identityref {
                 base dtls-cert-types;
               }
               mandatory true;
               description
                 "The certificate type of this object instance.
                  The value MUST be the same as one of the
                  identities listed with the base 'dtls-cert-types'.
                  This value can only be provided when this
                  instance is created and is not subsequently
                  writable.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.10";
             }

             leaf private-key {
               nacm:default-deny-all;
               type binary;
               mandatory true;
               description
                 "The value of the private key. If this is non-empty,
                  this certificate can be used by this implementation to
                  provide a certificate during DTLS handshaking.";
               reference
                 "RFC 9046: Babel Information Model, Section 3.10";
             }

             leaf algorithm {
               nacm:default-deny-write;
               type identityref {
                 base ct:private-key-format;
               }
               mandatory true;
               description
                 "Identifies the algorithm identity with which the
                  private key has been encoded. This value can only be
                  provided when this instance is created and is not
                  subsequently writable.";
             }
           }
         }
         uses routes;
       }
     }
   }
   <CODE ENDS>

3.  IANA Considerations

3.1.  URI Registration

   IANA has registered the following URI in the "ns" registry of the
   "IETF XML Registry" [RFC3688].

   URI:  urn:ietf:params:xml:ns:yang:ietf-babel
   Registrant Contact:  The IESG
   XML:  N/A; the requested URI is an XML namespace.

3.2.  YANG Module Name Registration

   IANA has registered the following in the "YANG Module Names" registry
   [RFC6020].

   Name:  ietf-babel
   Namespace:  urn:ietf:params:xml:ns:yang:ietf-babel
   Prefix:  babel
   Reference:  RFC 9647

4.  Security Considerations

   This section is modeled after the template defined in Section 3.7.1
   of [RFC8407].

   The "ietf-babel" YANG module defines a data model that is designed to
   be accessed via YANG-based management protocols, such as NETCONF
   [RFC6241] and RESTCONF [RFC8040].  These protocols have mandatory-to-
   implement secure transport layers (e.g., Secure Shell (SSH)
   [RFC4252], TLS [RFC8446], and QUIC [RFC9000]) and mandatory-to-
   implement mutual authentication.

   The Network Configuration Access Control Model (NACM) [RFC8341]
   provides the means to restrict access for particular NETCONF users to
   a preconfigured subset of all available NETCONF protocol operations
   and content.

   The security considerations outlined here are specific to the YANG
   data model and do not cover security considerations of the Babel
   protocol or its security mechanisms in "The Babel Routing Protocol"
   [RFC8966], "MAC Authentication for the Babel Routing Protocol"
   [RFC8967], and "Babel Routing Protocol over Datagram Transport Layer
   Security" [RFC8968].  Each of these has its own Security
   Considerations section for considerations that are specific to it.

   There are a number of data nodes defined in the YANG module that are
   writable/created/deleted (i.e., config true, which is the default).
   These data nodes may be considered sensitive or vulnerable in some
   network environments.  Write operations (e.g., <edit-config>) to
   these data nodes without proper protection can have a negative effect
   on network operations.  These are the subtrees and data nodes and
   their sensitivity/vulnerability from a config true perspective:

   'babel':  This container includes an 'enable' parameter that can be
      used to enable or disable use of Babel on a router.

   'babel/constants':  This container includes configuration parameters
      that can prevent reachability if misconfigured.

   'babel/interfaces':  This leaf-list has configuration parameters that
      can enable/disable security mechanisms and change performance
      characteristics of the Babel protocol.  For example, enabling
      logging of packets and giving unintended access to the log files
      gives an attacker detailed knowledge of the network and allows it
      to launch an attack on the traffic traversing the network device.

   'babel/hmac' and 'babel/dtls':  These contain security credentials
      that influence whether incoming packets are trusted and whether
      outgoing packets are produced in such a way that the receiver will
      treat them as trusted.

   Some of the readable data or config false nodes in this YANG module
   may be considered sensitive or vulnerable in some network
   environments.  It is thus important to control read access (e.g., via
   get, get-config, or notification) to these data nodes.  These are the
   subtrees and data nodes and their sensitivity/vulnerability from a
   config false perspective:

   'babel':  Access to the information in the various nodes can disclose
      the network topology.  Additionally, the routes used by a network
      device may be used to mount a subsequent attack on traffic
      traversing the network device.

   'babel/hmac' and 'babel/dtls':  These contain security credentials,
      including private credentials of the router; however, it is
      required that these values not be readable.

   Some of the RPC operations in this YANG module may be considered
   sensitive or vulnerable in some network environments.  It is thus
   important to control access to these operations.  These are the
   operations and their sensitivity/vulnerability from an RPC operation
   perspective:

   This model defines two actions.  Resetting the statistics within an
   interface container would be visible to any monitoring processes,
   which should be designed to account for the possibility of such a
   reset.  The "test" action allows for validation that a MAC key and
   MAC algorithm have been properly configured.  The MAC key is a
   sensitive piece of information, and it is important to prevent an
   attacker that does not know the MAC key from being able to determine
   the MAC value by trying different input parameters.  The "test"
   action has been designed to not reveal such information directly.
   Such information might also be revealed indirectly due to side
   channels such as the time it takes to produce a response to the
   action.  Implementations SHOULD use a constant-time comparison
   between the input MAC and the locally generated MAC value for
   comparison in order to avoid such side channel leakage.

5.  References

5.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC4252]  Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
              Authentication Protocol", RFC 4252, DOI 10.17487/RFC4252,
              January 2006, <https://www.rfc-editor.org/info/rfc4252>.

   [RFC4868]  Kelly, S. and S. Frankel, "Using HMAC-SHA-256, HMAC-SHA-
              384, and HMAC-SHA-512 with IPsec", RFC 4868,
              DOI 10.17487/RFC4868, May 2007,
              <https://www.rfc-editor.org/info/rfc4868>.

   [RFC6241]  Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
              and A. Bierman, Ed., "Network Configuration Protocol
              (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
              <https://www.rfc-editor.org/info/rfc6241>.

   [RFC6991]  Schoenwaelder, J., Ed., "Common YANG Data Types",
              RFC 6991, DOI 10.17487/RFC6991, July 2013,
              <https://www.rfc-editor.org/info/rfc6991>.

   [RFC7693]  Saarinen, M., Ed. and J. Aumasson, "The BLAKE2
              Cryptographic Hash and Message Authentication Code (MAC)",
              RFC 7693, DOI 10.17487/RFC7693, November 2015,
              <https://www.rfc-editor.org/info/rfc7693>.

   [RFC7950]  Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
              RFC 7950, DOI 10.17487/RFC7950, August 2016,
              <https://www.rfc-editor.org/info/rfc7950>.

   [RFC8040]  Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
              Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
              <https://www.rfc-editor.org/info/rfc8040>.

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8341]  Bierman, A. and M. Bjorklund, "Network Configuration
              Access Control Model", STD 91, RFC 8341,
              DOI 10.17487/RFC8341, March 2018,
              <https://www.rfc-editor.org/info/rfc8341>.

   [RFC8343]  Bjorklund, M., "A YANG Data Model for Interface
              Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
              <https://www.rfc-editor.org/info/rfc8343>.

   [RFC8349]  Lhotka, L., Lindem, A., and Y. Qu, "A YANG Data Model for
              Routing Management (NMDA Version)", RFC 8349,
              DOI 10.17487/RFC8349, March 2018,
              <https://www.rfc-editor.org/info/rfc8349>.

   [RFC8446]  Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018,
              <https://www.rfc-editor.org/info/rfc8446>.

   [RFC8966]  Chroboczek, J. and D. Schinazi, "The Babel Routing
              Protocol", RFC 8966, DOI 10.17487/RFC8966, January 2021,
              <https://www.rfc-editor.org/info/rfc8966>.

   [RFC8967]  Dô, C., Kolodziejak, W., and J. Chroboczek, "MAC
              Authentication for the Babel Routing Protocol", RFC 8967,
              DOI 10.17487/RFC8967, January 2021,
              <https://www.rfc-editor.org/info/rfc8967>.

   [RFC8968]  Décimo, A., Schinazi, D., and J. Chroboczek, "Babel
              Routing Protocol over Datagram Transport Layer Security",
              RFC 8968, DOI 10.17487/RFC8968, January 2021,
              <https://www.rfc-editor.org/info/rfc8968>.

   [RFC9000]  Iyengar, J., Ed. and M. Thomson, Ed., "QUIC: A UDP-Based
              Multiplexed and Secure Transport", RFC 9000,
              DOI 10.17487/RFC9000, May 2021,
              <https://www.rfc-editor.org/info/rfc9000>.

   [RFC9046]  Stark, B. and M. Jethanandani, "Babel Information Model",
              RFC 9046, DOI 10.17487/RFC9046, June 2021,
              <https://www.rfc-editor.org/info/rfc9046>.

   [RFC9147]  Rescorla, E., Tschofenig, H., and N. Modadugu, "The
              Datagram Transport Layer Security (DTLS) Protocol Version
              1.3", RFC 9147, DOI 10.17487/RFC9147, April 2022,
              <https://www.rfc-editor.org/info/rfc9147>.

   [RFC9640]  Watsen, K., "YANG Data Types and Groupings for
              Cryptography", RFC 9640, DOI 10.17487/RFC9640, October
              2024, <https://www.rfc-editor.org/info/rfc9640>.

5.2.  Informative References

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104,
              DOI 10.17487/RFC2104, February 1997,
              <https://www.rfc-editor.org/info/rfc2104>.

   [RFC3688]  Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
              DOI 10.17487/RFC3688, January 2004,
              <https://www.rfc-editor.org/info/rfc3688>.

   [RFC6020]  Bjorklund, M., Ed., "YANG - A Data Modeling Language for
              the Network Configuration Protocol (NETCONF)", RFC 6020,
              DOI 10.17487/RFC6020, October 2010,
              <https://www.rfc-editor.org/info/rfc6020>.

   [RFC7468]  Josefsson, S. and S. Leonard, "Textual Encodings of PKIX,
              PKCS, and CMS Structures", RFC 7468, DOI 10.17487/RFC7468,
              April 2015, <https://www.rfc-editor.org/info/rfc7468>.

   [RFC8340]  Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
              BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
              <https://www.rfc-editor.org/info/rfc8340>.

   [RFC8342]  Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
              and R. Wilton, "Network Management Datastore Architecture
              (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
              <https://www.rfc-editor.org/info/rfc8342>.

   [RFC8407]  Bierman, A., "Guidelines for Authors and Reviewers of
              Documents Containing YANG Data Models", BCP 216, RFC 8407,
              DOI 10.17487/RFC8407, October 2018,
              <https://www.rfc-editor.org/info/rfc8407>.

   [W3C.REC-xml-20081126]
              Bray, T., Paoli, J., Sperberg-McQueen, C. M., Maler, E.,
              and F. Yergeau, "Extensible Markup Language (XML) 1.0
              (Fifth Edition)", W3C Recommendation REC-xml-20081126,
              November 2008, <https://www.w3.org/TR/xml/>.

Appendix A.  Tree Diagram and Example Configurations

   This section is devoted to including a complete tree diagram and
   examples that demonstrate how Babel can be configured.

   Note that various examples are encoded using Extensible Markup
   Language (XML) [W3C.REC-xml-20081126].

A.1.  Complete Tree Diagram

   This section includes the complete tree diagram for the Babel YANG
   module.

   module: ietf-babel

     augment /rt:routing/rt:control-plane-protocols
               /rt:control-plane-protocol:
       +--rw babel!
          +--ro version?              string
          +--rw enable                boolean
          +--ro router-id?            binary
          +--ro seqno?                uint16
          +--rw statistics-enabled?   boolean
          +--rw constants
          |  +--rw udp-port?      inet:port-number
          |  +--rw mcast-group?   inet:ip-address
          +--rw interfaces* [reference]
          |  +--rw reference               if:interface-ref
          |  +--rw enable?                 boolean
          |  +--rw metric-algorithm        identityref
          |  +--rw split-horizon?          boolean
          |  +--ro mcast-hello-seqno?      uint16
          |  +--rw mcast-hello-interval?   uint16
          |  +--rw update-interval?        uint16
          |  +--rw mac-enable?             boolean
          |  +--rw mac-key-sets*           -> ../../mac-key-set/name
          |  +--rw mac-verify?             boolean
          |  +--rw dtls-enable?            boolean
          |  +--rw dtls-certs*             -> ../../dtls/name
          |  +--rw dtls-cached-info?       boolean
          |  +--rw dtls-cert-prefer*       -> ../../dtls/certs/type
          |  +--rw packet-log-enable?      boolean
          |  +--ro packet-log?             inet:uri
          |  +--ro statistics
          |  |  +--ro discontinuity-time    yang:date-and-time
          |  |  +--ro sent-mcast-hello?     yang:counter32
          |  |  +--ro sent-mcast-update?    yang:counter32
          |  |  +--ro sent-ucast-hello?     yang:counter32
          |  |  +--ro sent-ucast-update?    yang:counter32
          |  |  +--ro sent-ihu?             yang:counter32
          |  |  +--ro received-packets?     yang:counter32
          |  |  +---x reset
          |  |     +---w input
          |  |     |  +---w reset-at?   yang:date-and-time
          |  |     +--ro output
          |  |        +--ro reset-finished-at?   yang:date-and-time
          |  +--ro neighbor-objects* [neighbor-address]
          |     +--ro neighbor-address         inet:ip-address
          |     +--ro hello-mcast-history?     string
          |     +--ro hello-ucast-history?     string
          |     +--ro txcost?                  int32
          |     +--ro exp-mcast-hello-seqno?   union
          |     +--ro exp-ucast-hello-seqno?   union
          |     +--ro ucast-hello-seqno?       union
          |     +--ro ucast-hello-interval?    uint16
          |     +--ro rxcost?                  uint16
          |     +--ro cost?                    int32
          +--rw mac-key-set* [name]
          |  +--rw name             string
          |  +--rw default-apply?   boolean
          |  +--rw keys* [name]
          |     +--rw name          string
          |     +--rw use-send      boolean
          |     +--rw use-verify    boolean
          |     +--rw value         binary
          |     +--rw algorithm     identityref
          |     +---x test
          |        +---w input
          |        |  +---w test-string    binary
          |        |  +---w mac            binary
          |        +--ro output
          |           +--ro indication    boolean
          +--rw dtls* [name]
          |  +--rw name             string
          |  +--rw default-apply    boolean
          |  +--rw certs* [name]
          |     +--rw name           string
          |     +--rw value          string
          |     +--rw type           identityref
          |     +--rw private-key    binary
          |     +--rw algorithm      identityref
          +--ro routes* [prefix]
             +--ro prefix               inet:ip-prefix
             +--ro router-id?           binary
             +--ro neighbor?            leafref
             +--ro received-metric?     union
             +--ro calculated-metric?   union
             +--ro seqno?               uint16
             +--ro next-hop?            union
             +--ro feasible?            boolean
             +--ro selected?            boolean

A.2.  Statistics Gathering Enabled

   In this example, interface eth0 is being configured for routing
   protocol Babel, and statistics gathering is enabled.  For security,
   HMAC-SHA256 is supported.  Every sent Babel packet is signed with the
   key value provided, and every received Babel packet is verified with
   the same key value.

   <?xml version="1.0" encoding="UTF-8"?>
   <interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
               xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">
     <interface>
       <name>eth0</name>
       <type>ianaift:ethernetCsmacd</type>
       <enabled>true</enabled>
     </interface>
   </interfaces>
   <routing
       xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
     <control-plane-protocols>
       <control-plane-protocol>
         <type
             xmlns:babel=
             "urn:ietf:params:xml:ns:yang:ietf-babel">babel:babel</type>
         <name>name:babel</name>
         <babel
             xmlns="urn:ietf:params:xml:ns:yang:ietf-babel">
           <enable>true</enable>
           <statistics-enabled>true</statistics-enabled>
           <interfaces>
             <reference>eth0</reference>
             <metric-algorithm>two-out-of-three</metric-algorithm>
             <split-horizon>true</split-horizon>
           </interfaces>
           <mac-key-set>
             <name>hmac-sha256</name>
             <keys>
               <name>hmac-sha256-keys</name>
               <use-send>true</use-send>
               <use-verify>true</use-verify>
               <value>base64encodedvalue==</value>
               <algorithm>hmac-sha256</algorithm>
             </keys>
           </mac-key-set>
         </babel>
       </control-plane-protocol>
     </control-plane-protocols>
   </routing>

A.3.  Automatic Detection of Properties

   In this example, babeld is configured on two interfaces:

      interface eth0
      interface wlan0

   This says to run Babel on interfaces eth0 and wlan0.  Babeld will
   automatically detect that eth0 is wired and wlan0 is wireless and
   will configure the right parameters automatically.

   <?xml version="1.0" encoding="UTF-8"?>
   <interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
               xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">
     <interface>
       <name>eth0</name>
       <type>ianaift:ethernetCsmacd</type>
       <enabled>true</enabled>
     </interface>
     <interface>
       <name>wlan0</name>
       <type>ianaift:ieee80211</type>
       <enabled>true</enabled>
     </interface>
   </interfaces>
   <routing
       xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
     <control-plane-protocols>
       <control-plane-protocol>
         <type
             xmlns:babel=
             "urn:ietf:params:xml:ns:yang:ietf-babel">babel:babel</type>
         <name>name:babel</name>
         <babel
             xmlns="urn:ietf:params:xml:ns:yang:ietf-babel">
           <enable>true</enable>
           <interfaces>
             <reference>eth0</reference>
             <enable>true</enable>
             <metric-algorithm>two-out-of-three</metric-algorithm>
             <split-horizon>true</split-horizon>
           </interfaces>
           <interfaces>
             <reference>wlan0</reference>
             <enable>true</enable>
             <metric-algorithm>etx</metric-algorithm>
             <split-horizon>false</split-horizon>
           </interfaces>
         </babel>
       </control-plane-protocol>
     </control-plane-protocols>
   </routing>

A.4.  Override Default Properties

   In this example, babeld is configured on three interfaces:

      interface eth0
      interface eth1 type wireless
      interface tun0 type tunnel

   Here, interface eth1 is an Ethernet bridged to a wireless radio, so
   babeld's autodetection fails, and the interface type needs to be
   configured manually.  Tunnels are not detected automatically, so this
   needs to be specified.

   This is equivalent to the following:

      interface eth0 metric-algorithm 2-out-of-3 split-horizon true
      interface eth1 metric-algorithm etx split-horizon false
      interface tun0 metric-algorithm 2-out-of-3 split-horizon true

   <?xml version="1.0" encoding="UTF-8"?>
   <interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
               xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">
     <interface>
       <name>eth0</name>
       <type>ianaift:ethernetCsmacd</type>
       <enabled>true</enabled>
     </interface>
     <interface>
       <name>eth1</name>
       <type>ianaift:ethernetCsmacd</type>
       <enabled>true</enabled>
     </interface>
     <interface>
       <name>tun0</name>
       <type>ianaift:tunnel</type>
       <enabled>true</enabled>
     </interface>
   </interfaces>
   <routing
       xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
     <control-plane-protocols>
       <control-plane-protocol>
         <type
             xmlns:babel=
             "urn:ietf:params:xml:ns:yang:ietf-babel">babel:babel</type>
         <name>name:babel</name>
         <babel
             xmlns="urn:ietf:params:xml:ns:yang:ietf-babel">
           <enable>true</enable>
           <interfaces>
             <reference>eth0</reference>
             <enable>true</enable>
             <metric-algorithm>two-out-of-three</metric-algorithm>
             <split-horizon>true</split-horizon>
           </interfaces>
           <interfaces>
             <reference>eth1</reference>
             <enable>true</enable>
             <metric-algorithm>etx</metric-algorithm>
             <split-horizon>false</split-horizon>
           </interfaces>
           <interfaces>
             <reference>tun0</reference>
             <enable>true</enable>
             <metric-algorithm>two-out-of-three</metric-algorithm>
             <split-horizon>true</split-horizon>
           </interfaces>
         </babel>
       </control-plane-protocol>
     </control-plane-protocols>
   </routing>

A.5.  Configuring Other Properties

   In this example, two interfaces are configured for babeld:

      interface eth0
      interface ppp0 hello-interval 30 update-interval 120

   Here, ppp0 is a metered 3G link used for fallback connectivity.  It
   runs with much higher than default time constants in order to avoid
   control traffic as much as possible.

   <?xml version="1.0" encoding="UTF-8"?>
   <interfaces xmlns="urn:ietf:params:xml:ns:yang:ietf-interfaces"
               xmlns:ianaift="urn:ietf:params:xml:ns:yang:iana-if-type">
     <interface>
       <name>eth0</name>
       <type>ianaift:ethernetCsmacd</type>
       <enabled>true</enabled>
     </interface>
     <interface>
       <name>ppp0</name>
       <type>ianaift:ppp</type>
       <enabled>true</enabled>
     </interface>
   </interfaces>
   <routing
       xmlns="urn:ietf:params:xml:ns:yang:ietf-routing">
     <control-plane-protocols>
       <control-plane-protocol>
         <type
             xmlns:babel=
             "urn:ietf:params:xml:ns:yang:ietf-babel">babel:babel</type>
         <name>name:babel</name>
         <babel
             xmlns="urn:ietf:params:xml:ns:yang:ietf-babel">
           <enable>true</enable>
           <interfaces>
             <reference>eth0</reference>
             <enable>true</enable>
             <metric-algorithm>two-out-of-three</metric-algorithm>
             <split-horizon>true</split-horizon>
           </interfaces>
           <interfaces>
             <reference>ppp0</reference>
             <enable>true</enable>
             <mcast-hello-interval>30</mcast-hello-interval>
             <update-interval>120</update-interval>
             <metric-algorithm>two-out-of-three</metric-algorithm>
           </interfaces>
         </babel>
       </control-plane-protocol>
     </control-plane-protocols>
   </routing>

Acknowledgements

   Juliusz Chroboczek provided most of the example configurations for
   babel that are shown in Appendix A.

Authors' Addresses

   Mahesh Jethanandani
   Kloud Services
   California
   United States of America
   Email: mjethanandani@gmail.com


   Barbara Stark
   AT&T
   Atlanta, GA
   United States of America
   Email: barbara.stark@att.com