RFC 9647 | YANG Data Model for Babel | October 2024
Jethanandani & Stark | Standards Track | [Page]

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

# RFC 9647

# 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.¶

## 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