Babel Working Group M. Jethanandani Internet-Draft Kloud Services Intended status: Standards Track B. Stark Expires: 26 March 2022 AT&T 22 September 2021 YANG Data Model for Babel draft-ietf-babel-yang-model-13 Abstract This document defines a data model for the Babel routing protocol. The data model is defined using the YANG data modeling language. 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. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at https://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on 26 March 2022. Copyright Notice Copyright (c) 2021 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. Jethanandani & Stark Expires 26 March 2022 [Page 1] Internet-Draft Babel YANG model September 2021 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 Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Note to RFC Editor . . . . . . . . . . . . . . . . . . . 2 1.2. Tree Diagram Annotations . . . . . . . . . . . . . . . . 3 2. Babel Module . . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Information Model . . . . . . . . . . . . . . . . . . . . 3 2.2. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 3 2.3. YANG Module . . . . . . . . . . . . . . . . . . . . . . . 5 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 3.1. URI Registrations . . . . . . . . . . . . . . . . . . . . 32 3.2. YANG Module Name Registration . . . . . . . . . . . . . . 32 4. Security Considerations . . . . . . . . . . . . . . . . . . . 32 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 34 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 34 6.1. Normative References . . . . . . . . . . . . . . . . . . 34 6.2. Informative References . . . . . . . . . . . . . . . . . 35 Appendix A. Tree Diagram and Example Configurations . . . . . . 36 A.1. Complete Tree Diagram . . . . . . . . . . . . . . . . . . 36 A.2. Statistics Gathering Enabled . . . . . . . . . . . . . . 38 A.3. Automatic Detection of Properties . . . . . . . . . . . . 39 A.4. Override Default Properties . . . . . . . . . . . . . . . 41 A.5. Configuring other Properties . . . . . . . . . . . . . . 42 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 43 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 Network Management Datastore Architecture (NDMA) [RFC8342] compatible. 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. Note to RFC Editor Artwork in this document contains shorthand references to drafts in progress. Please apply the following replacements and remove this note before publication. * "XXXX" --> the assigned RFC value for this draft both in this draft and in the YANG models under the revision statement. Jethanandani & Stark Expires 26 March 2022 [Page 2] Internet-Draft Babel YANG model September 2021 * Revision date in model, in the format 2021-09-20 needs to get updated with the date the draft gets approved. The date also needs to get reflected on the line with . 1.2. Tree Diagram Annotations For a reference to the annotations used in tree diagrams included in this draft, 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 There are a few things that should be noted 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'. Jethanandani & Stark Expires 26 March 2022 [Page 3] Internet-Draft Babel YANG model September 2021 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 'next-hop' address. Finally, for security two subtrees are defined to contain 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 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. Jethanandani & Stark Expires 26 March 2022 [Page 4] Internet-Draft Babel YANG model September 2021 2.3. YANG Module This YANG module augments the YANG Routing Management [RFC8349] module 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 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' for 'metric- algorithm', and 'split-horizon' set to true. On the other hand, for a wireless interface it will assume 'etx' for 'metric-algorithm', and 'split-horizon' set to false. However, if the wired link is connected to a wireless radio, the values can be overriden by setting 'metric-algorithm' to 'etx', and 'split-horizon' to false. Similarly, an interface that is a metered 3G link, and 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], The Datagram Transport Layer Security (DTLS) Version 1.3 [I-D.ietf-tls-dtls13], The Blake2 Cryptographic Hash and Message Authentication Code (MAC) [RFC7693], Babel Information Model [RFC9046], The Babel Routing Protocol [RFC8966], YANG Data Types and Groupings for Cryptography [I-D.ietf-netconf-crypto-types], Network Configuration Access Control Model [RFC8341] and MAC Authentication for Babel [RFC8967]. file "ietf-babel@2021-09-20.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 Jethanandani & Stark Expires 26 March 2022 [Page 5] Internet-Draft Babel YANG model September 2021 "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: YANG Routing Management"; } import ietf-crypto-types { prefix ct; reference "I-D.ietf-netconf-crypto-types: YANG Data Types and Groupings for Cryptographay."; } import ietf-netconf-acm { prefix nacm; reference "RFC 8341: Network Configuration Access Control Model"; } organization "IETF Babel routing protocol Working Group"; contact "WG Web: http://tools.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 Jethanandani & Stark Expires 26 March 2022 [Page 6] Internet-Draft Babel YANG model September 2021 described in BCP 14 (RFC 2119) (RFC 8174) when, and only when, they appear in all capitals, as shown here. Copyright (c) 2021 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 Simplified 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 XXXX (https://www.rfc-editor.org/info/rfcXXXX); see the RFC itself for full legal notices."; revision 2021-09-20 { description "Initial version."; reference "RFC XXXX: Babel YANG Data Model."; } /* * 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 Babel Routing Protocol."; } Jethanandani & Stark Expires 26 March 2022 [Page 7] Internet-Draft Babel YANG model September 2021 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 Babel Routing Protocol."; } feature blake2s-supported { description "This implementation supports BLAKE2s MAC algorithms."; reference "RFC 8967: MAC authentication for 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 Jethanandani & Stark Expires 26 March 2022 [Page 8] Internet-Draft Babel YANG model September 2021 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 Jethanandani & Stark Expires 26 March 2022 [Page 9] Internet-Draft Babel YANG model September 2021 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"; Jethanandani & Stark Expires 26 March 2022 [Page 10] Internet-Draft Babel YANG model September 2021 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 Jethanandani & Stark Expires 26 March 2022 [Page 11] Internet-Draft Babel YANG model September 2021 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."; } Jethanandani & Stark Expires 26 March 2022 [Page 12] Internet-Draft Babel YANG model September 2021 } 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 3.1."; } 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 routing type Jethanandani & Stark Expires 26 March 2022 [Page 13] Internet-Draft Babel YANG model September 2021 is of type 'babel'."; } description "Augment the routing module to support a common structure between routing protocols."; reference "YANG Routing Management, RFC 8349, Lhotka & Lindem, March 2018."; 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 or datastore therefore indicates the configured administrative value of whether the protocol is enabled or not. A read from the 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 Jethanandani & Stark Expires 26 March 2022 [Page 14] Internet-Draft Babel YANG model September 2021 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; Jethanandani & Stark Expires 26 March 2022 [Page 15] Internet-Draft Babel YANG model September 2021 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."; Jethanandani & Stark Expires 26 March 2022 [Page 16] Internet-Draft Babel YANG model September 2021 } 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)."; Jethanandani & Stark Expires 26 March 2022 [Page 17] Internet-Draft Babel YANG model September 2021 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."; Jethanandani & Stark Expires 26 March 2022 [Page 18] Internet-Draft Babel YANG model September 2021 } 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; Jethanandani & Stark Expires 26 March 2022 [Page 19] Internet-Draft Babel YANG model September 2021 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."; } container statistics { config false; description "Statistics collection object for this interface."; reference "RFC 9046: Babel Information Model, Section 3.3."; 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."; } Jethanandani & Stark Expires 26 March 2022 [Page 20] Internet-Draft Babel YANG model September 2021 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 3.6."; } 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 3.6."; } leaf sent-ihu { type yang:counter32; description "A count of the number of IHU packets sent on this interface."; reference "RFC 9046: Babel Information Model, Section 3.6."; } 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 Jethanandani & Stark Expires 26 March 2022 [Page 21] Internet-Draft Babel YANG model September 2021 for every instance of the interface."; 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 Object."; reference "RFC 9046: Babel Information Model, Section 3.5."; leaf neighbor-address { type inet:ip-address; description "IPv4 or v6 address the neighbor sends packets from."; 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 most recent Hello for any not-received Hellos); represented as a string of utf-8 encoded hex digits. A bit that is set indicates that the corresponding Hello was received, and a bit Jethanandani & Stark Expires 26 March 2022 [Page 22] Internet-Draft Babel YANG model September 2021 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 most recent Hello for any not-received Hellos); represented as a string using utf-8 encoded hex digits 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 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 Jethanandani & Stark Expires 26 March 2022 [Page 23] Internet-Draft Babel YANG model September 2021 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 { Jethanandani & Stark Expires 26 March 2022 [Page 24] Internet-Draft Babel YANG model September 2021 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 kept in the neighbor table about the reception of Hellos, and the txcost 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."; Jethanandani & Stark Expires 26 March 2022 [Page 25] Internet-Draft Babel YANG model September 2021 } 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."; Jethanandani & Stark Expires 26 March 2022 [Page 26] Internet-Draft Babel YANG model September 2021 } 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 HMAC construction [RFC2104], the length MUST be between 0 and an upper limit that is at least the size of the output length (where 'HMAC-SHA256' output length is 32 octets as described in [RFC4868]). 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 [RFC8967] Security Considerations). If the algorithm is 'BLAKE2s-128', the length MUST be between 0 and 32 bytes inclusive as specified by [RFC7693]."; 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 { Jethanandani & Stark Expires 26 March 2022 [Page 27] Internet-Draft Babel YANG model September 2021 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 are 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 Jethanandani & Stark Expires 26 March 2022 [Page 28] Internet-Draft Babel YANG model September 2021 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 interfaces instances at the time they are created, by including it Jethanandani & Stark Expires 26 March 2022 [Page 29] Internet-Draft Babel YANG model September 2021 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 PEM format [RFC7468]. 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 type { nacm:default-deny-write; Jethanandani & Stark Expires 26 March 2022 [Page 30] Internet-Draft Babel YANG model September 2021 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; } } } Jethanandani & Stark Expires 26 March 2022 [Page 31] Internet-Draft Babel YANG model September 2021 3. IANA Considerations This document registers a URI and a YANG module. 3.1. URI Registrations URI: urn:ietf:params:xml:ns:yang:ietf-babel 3.2. YANG Module Name Registration This document registers a YANG module in the YANG Module Names registry YANG [RFC6020]. Name:ietf-babel Namespace: urn:ietf:params:xml:ns:yang:ietf-babel prefix: babel reference: RFC XXXX 4. Security Considerations The YANG module specified in this document defines a schema for data that is designed to be accessed via network management protocol such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer and the mandatory-to-implement secure transport is SSH [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC8446]. The NETCONF Access Control Model (NACM [RFC8341]) provides the means to restrict access for particular NETCONF users to a pre-configured 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 Data 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 which 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., ) 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: Jethanandani & Stark Expires 26 March 2022 [Page 32] Internet-Draft Babel YANG model September 2021 '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 a way such 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 perpective: '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 a 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" Jethanandani & Stark Expires 26 March 2022 [Page 33] Internet-Draft Babel YANG model September 2021 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. Acknowledgements Juliusz Chroboczek provided most of the example configurations for babel that are shown in the Appendix. 6. References 6.1. Normative References [I-D.ietf-netconf-crypto-types] Watsen, K., "YANG Data Types and Groupings for Cryptography", Work in Progress, Internet-Draft, draft- ietf-netconf-crypto-types-21, 14 September 2021, . [I-D.ietf-tls-dtls13] Rescorla, E., Tschofenig, H., and N. Modadugu, "The Datagram Transport Layer Security (DTLS) Protocol Version 1.3", Work in Progress, Internet-Draft, draft-ietf-tls- dtls13-43, 30 April 2021, . [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [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, . [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013, . [RFC7693] Saarinen, M-J., Ed. and J-P. Aumasson, "The BLAKE2 Cryptographic Hash and Message Authentication Code (MAC)", RFC 7693, DOI 10.17487/RFC7693, November 2015, . Jethanandani & Stark Expires 26 March 2022 [Page 34] Internet-Draft Babel YANG model September 2021 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration Access Control Model", STD 91, RFC 8341, DOI 10.17487/RFC8341, March 2018, . [RFC8343] Bjorklund, M., "A YANG Data Model for Interface Management", RFC 8343, DOI 10.17487/RFC8343, March 2018, . [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, . [RFC8966] Chroboczek, J. and D. Schinazi, "The Babel Routing Protocol", RFC 8966, DOI 10.17487/RFC8966, January 2021, . [RFC8967] Do, C., Kolodziejak, W., and J. Chroboczek, "MAC Authentication for the Babel Routing Protocol", RFC 8967, DOI 10.17487/RFC8967, January 2021, . [RFC8968] Decimo, A., Schinazi, D., and J. Chroboczek, "Babel Routing Protocol over Datagram Transport Layer Security", RFC 8968, DOI 10.17487/RFC8968, January 2021, . [RFC9046] Stark, B. and M. Jethanandani, "Babel Information Model", RFC 9046, DOI 10.17487/RFC9046, June 2021, . 6.2. Informative References [RFC2104] Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed- Hashing for Message Authentication", RFC 2104, DOI 10.17487/RFC2104, February 1997, . Jethanandani & Stark Expires 26 March 2022 [Page 35] Internet-Draft Babel YANG model September 2021 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, DOI 10.17487/RFC6020, October 2010, . [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, . [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, . [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, . [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, . 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. 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 Jethanandani & Stark Expires 26 March 2022 [Page 36] Internet-Draft Babel YANG model September 2021 +--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] Jethanandani & Stark Expires 26 March 2022 [Page 37] Internet-Draft Babel YANG model September 2021 | +--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 packets is signed with the key value provided, and every received Babel packet is verified with the same key value. Jethanandani & Stark Expires 26 March 2022 [Page 38] Internet-Draft Babel YANG model September 2021 eth0 ianaift:ethernetCsmacd true babel:babel name:babel true true eth0 two-out-of-three true hmac-sha256 hmac-sha256-keys true true base64encodedvalue== hmac-sha256 A.3. Automatic Detection of Properties Jethanandani & Stark Expires 26 March 2022 [Page 39] Internet-Draft Babel YANG model September 2021 eth0 ianaift:ethernetCsmacd true wlan0 ianaift:ieee80211 true babel:babel name:babel true eth0 true two-out-of-three true wlan0 true etx false Jethanandani & Stark Expires 26 March 2022 [Page 40] Internet-Draft Babel YANG model September 2021 A.4. Override Default Properties eth0 ianaift:ethernetCsmacd true eth1 ianaift:ethernetCsmacd true tun0 ianaift:tunnel true babel:babel name:babel true eth0 true two-out-of-three true eth1 true etx false tun0 true two-out-of-three true A.5. Configuring other Properties eth0 ianaift:ethernetCsmacd true Jethanandani & Stark Expires 26 March 2022 [Page 42] Internet-Draft Babel YANG model September 2021 ppp0 ianaift:ppp true babel:babel name:babel true eth0 true two-out-of-three true ppp0 true 30 120 two-out-of-three Authors' Addresses Mahesh Jethanandani Kloud Services California United States of America Email: mjethanandani@gmail.com Jethanandani & Stark Expires 26 March 2022 [Page 43] Internet-Draft Babel YANG model September 2021 Barbara Stark AT&T Atlanta, GA United States of America Email: barbara.stark@att.com Jethanandani & Stark Expires 26 March 2022 [Page 44]