Network Working Group A. Bierman Internet-Draft YumaWorks Obsoletes: rfc7895 (if approved) M. Bjorklund Intended status: Standards Track Tail-f Systems Expires: July 21, 2018 J. Schoenwaelder Jacobs University K. Watsen Juniper Networks R. Wilton Cisco Systems January 17, 2018 YANG Library draft-ietf-netconf-rfc7895bis-03 Abstract This document describes a YANG library that provides information about all the YANG modules and datastores used by a network management server (e.g., a Network Configuration Protocol (NETCONF) server). Simple caching mechanisms are provided to allow clients to minimize retrieval of this information. 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 http://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 July 21, 2018. Copyright Notice Copyright (c) 2018 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 Bierman, et al. Expires July 21, 2018 [Page 1] Internet-Draft YANG Library January 2018 (http://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 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 1.2. Tree Diagrams . . . . . . . . . . . . . . . . . . . . . . 4 1.3. Motivation for rfc7895bis . . . . . . . . . . . . . . . . 4 1.4. Summary of Changes from RFC 7895 . . . . . . . . . . . . 6 2. YANG Library . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1. yang-library . . . . . . . . . . . . . . . . . . . . . . 7 2.1.1. yang-library/checksum . . . . . . . . . . . . . . . . 7 2.1.2. yang-library/datastore . . . . . . . . . . . . . . . 8 2.1.3. yang-library/schema . . . . . . . . . . . . . . . . . 8 2.1.4. yang-library/module-set . . . . . . . . . . . . . . . 8 2.1.5. yang-library/module-set/module . . . . . . . . . . . 9 2.1.6. yang-library/module-set/import-only-module . . . . . 9 2.2. YANG Library Module . . . . . . . . . . . . . . . . . . . 9 3. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 3.1. YANG Module Registry . . . . . . . . . . . . . . . . . . 21 4. Security Considerations . . . . . . . . . . . . . . . . . . . 22 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 22 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 23 6.1. Normative References . . . . . . . . . . . . . . . . . . 23 6.2. Informative References . . . . . . . . . . . . . . . . . 24 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 24 1. Introduction There is a need for standard mechanisms to provide the operational state of a network management server. This includes, for instance, identifying the YANG modules and datastores that are in use by a server and how they relate to each other. This document defines a YANG module that can be used to provide this informaton, in a way that is compatible with the NMDA [I-D.ietf-netmod-revised-datastores], but that is also backwards compatible with the "YANG Module Library" YANG module defined in [RFC7895]. If a large number of YANG modules are utilized by the server, then the YANG library contents needed can be relatively large. This Bierman, et al. Expires July 21, 2018 [Page 2] Internet-Draft YANG Library January 2018 information changes very infrequently, so it is important that clients be able to cache the YANG library contents and easily identify whether their cache is out of date. YANG library information can be different on every server and can change at runtime or across a server reboot. If the server implements multiple protocols to access the YANG- defined data, each such protocol has its own conceptual instantiation of the YANG library. The following information is needed by a client application (for each YANG module in the library) to fully utilize the YANG data modeling language: o identifier: a unique identifier for the module that includes the module's name, revision, submodules, features, and deviations. o name: The name of the YANG module. o revision: Each YANG module and submodule within the library SHOULD have a revision. This is derived from the most recent revision statement within the module or submodule. o submodule list: The name, and if defined, revision of each submodule used by the module MUST be identified. o feature list: The name of each YANG feature supported by the server, in a given datastore schema, MUST be identified. o deviation list: The name of each YANG module used for deviation statements, in a given datastore schema, MUST be identified. The following information is needed by a client application (for each datastore supported by the server) to fully access all the YANG- modelled data available on the server: o identity: the YANG identity for the datastore. o modules: modules supported by the datastore, including any features and deviations. 1.1. Terminology The keywords "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]. Bierman, et al. Expires July 21, 2018 [Page 3] Internet-Draft YANG Library January 2018 The following terms are defined in [RFC7950]: o module o submodule The following terms are defined in [I-D.ietf-netmod-revised-datastores]: o conventional configuration datastore o operational state datastore o operational state o datastore schema o client o server 1.2. Tree Diagrams Tree diagrams used in this document follow the notation defined in [I-D.ietf-netmod-yang-tree-diagrams]. 1.3. Motivation for rfc7895bis RFC Ed.: delete this section, including this note, at time of publication. All NETCONF servers supporting YANG 1.1 [RFC7950] are required to support YANG Library (see Section 5.6.4 of RFC 7950). Similarly, all RESTCONF servers are required to support YANG Library (see Section 10 of RFC 8040). These requirements are independent of if the server supports NMDA or not. RFC 7895 has a mandatory to implement "modules-state" tree that a server uses to advertise all the modules it supports. However, this module was designed assuming the all modules would be in all datastores, and with the same number of features and deviations. However, this is not the case with NMDA-compatible servers that may have some modules that only appear in (e.g., ietf- network-topo) or only also appear in a dynamic datastore (e.g., i2rs- ephemeral-rib). It is also possible that a server only implements a module in , as it hasn't yet coded support for returning the module's opstate yet. Presumably, an NMDA-supporting server would Bierman, et al. Expires July 21, 2018 [Page 4] Internet-Draft YANG Library January 2018 return all modules implemented in every datastore, but this would be misleading to existing clients and unhelpful to NMDA-aware clients. In the end, it appears that the "modules-state" node should be for non-NMDA aware clients. For backwards compatability, an NMDA- supporting server SHOULD populate "modules-state" in a backwards- compatible manner. The new "yang-library" node would be ignored by legacy clients, while providing all the data needed for NMDA-aware clients, which would themselves ignore the "modules-state" tree. Design objectives: 1. As efficient as possible for a client to consume. Since the size of the yang library can be quite large, it should be possible for clients to cache the yang library information. 2. A dynamic configuration datastore must be able to implement a module or feature that is not implemented in the conventional datastores. 3. It must be possible to NOT implement a module or feature in , even if it is implemented in some other datastore. This is required for transition purposes; a server that wants to implement should not have to implement all modules at once. 4. A given module can only be implemented in one revision in all datastores. If a module is implemented in more than one datastores, the same revision is implemented in all these datastores. 5. Multiple revisions can be used for import, if import-by revision is used. 6. Nice to have: make it possible to be used by schema mount The solution presented in this document is further motivated by the following desires: o leverage Section 5.6.4 of RFC 7950 and Section 10 of RFC 8040. o indicate which modules are supported by each datastore o enable the features and deviations to vary by datastore o structure extensible to support schema-mount o provide a top-level container for all server metadata Bierman, et al. Expires July 21, 2018 [Page 5] Internet-Draft YANG Library January 2018 1.4. Summary of Changes from RFC 7895 This document updates [RFC7895] in the following ways: o Renames document title from "YANG Module Library" to "YANG Library". o Adds a new top-level "yang-library" container to hold many types of server metadata: modules supported, datastores supported, relationships between datastores and modules, etc. o Adds a set of new groupings as replacements for the deprecated "module-list" grouping. o Adds a "yang-library-update" notification as a replacement for the deprecated "yang-library-change" notification. o Deprecates the "modules-state" tree. o Deprecates the "module-list" grouping. o Deprecates the "yang-library-change" notification. 2. YANG Library The "ietf-yang-library" module provides information about the modules and datastores supported by a server. This module is defined using YANG version 1.1, but it supports the description of YANG modules written in any revision of YANG. All data nodes in "ietf-yang-library" are "config false", and thus accessible in the operational state datastore. Following is the YANG Tree Diagram for the "ietf-yang-library" module, excluding the deprecated "modules-state" tree: Bierman, et al. Expires July 21, 2018 [Page 6] Internet-Draft YANG Library January 2018 module: ietf-yang-library +--ro yang-library +--ro module-set* [name] | +--ro name string | +--ro checksum string | +--ro module* [name] | | +--ro name yang:yang-identifier | | +--ro revision? revision-identifier | | +--ro namespace inet:uri | | +--ro location* inet:uri | | +--ro submodule* [name] | | | +--ro name yang:yang-identifier | | | +--ro revision? revision-identifier | | | +--ro location* inet:uri | | +--ro feature* [name] | | | +--ro name yang:yang-identifier | | +--ro deviation* [module] | | +--ro module -> ../../name | +--ro import-only-module* [name revision] | +--ro name yang:yang-identifier | +--ro revision union | +--ro namespace inet:uri | +--ro location* inet:uri | +--ro submodule* [name] | +--ro name yang:yang-identifier | +--ro revision? revision-identifier | +--ro location* inet:uri +--ro schema* [name] | +--ro name string | +--ro checksum string | +--ro module-set* -> ../../module-set/name +--ro datastore* [name] | +--ro name identityref | +--ro schema -> ../../schema/name +--ro checksum string notifications: +---n yang-library-update 2.1. yang-library This container holds all of the server's metadata. 2.1.1. yang-library/checksum This mandatory leaf contains a unique implementation-specific identifier representing the current information in the YANG library on a specific server. The value of this leaf MUST change whenever Bierman, et al. Expires July 21, 2018 [Page 7] Internet-Draft YANG Library January 2018 the the information in the YANG library changes. There is no requirement that the same information always results in the same "checksum" value. This leaf allows a client to fetch all schema information once, cache it, and only refetch it if the value of this leaf has been changed. If the value of this leaf changes, the server also generates a "yang-library-update" notification. Note that for a NETCONF server that implements YANG 1.1 [RFC7950], a change of the "checksum" value results in a new value for the :yang- library capability defined in [RFC7950]. Thus, if such a server implements NETCONF notifications [RFC5277], and the notification "netconf-capability-change" [RFC6470], a "netconf-capability-change" notification is generated whenever the "checksum" changes. 2.1.2. yang-library/datastore This list contains one entry for each datastore supported by the server, and identifies the datastore schema associated with a datastore via a reference to an entry in the "schema" list. Each supported conventional configuration datastore has a separate entry. 2.1.3. yang-library/schema An entry in the "schema" list represents the datastore schema that is used by one or more datastores. This list contains one entry for each schema in use by the server (e.g., presented by a datastore). All conventional configuration datastores and the operational state datastore use the same "schema" entry. A dynamic configuration datastore may use a different datastore schema from the conventional configuration datastores, and hence may require a separate "schema" entry. A schema has a leaf-list with references to entries in the "module-set" list. The schema consists of the sum of all modules in all referenced module sets. 2.1.4. yang-library/module-set Bierman, et al. Expires July 21, 2018 [Page 8] Internet-Draft YANG Library January 2018 2.1.5. yang-library/module-set/module 2.1.6. yang-library/module-set/import-only-module 2.2. YANG Library Module The "ietf-yang-library" module defines monitoring information for the YANG modules used by a server. The modules "ietf-yang-types" and "ietf-inet-types" from [RFC6991] and the module "ietf-datastores" from [I-D.ietf-netmod-revised-datastores] are used by this module for some type definitions. RFC Ed.: update the date below with the date of RFC publication and remove this note. file "ietf-yang-library@2018-01-17.yang" module ietf-yang-library { yang-version 1.1; namespace "urn:ietf:params:xml:ns:yang:ietf-yang-library"; prefix "yanglib"; 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-datastores { prefix ds; reference "I-D.ietf-revised-datastores: Network Management Datastore Architecture."; } organization "IETF NETCONF (Network Configuration) Working Group"; contact "WG Web: WG List: Author: Andy Bierman Bierman, et al. Expires July 21, 2018 [Page 9] Internet-Draft YANG Library January 2018 Author: Martin Bjorklund Author: Juergen Schoenwaelder Author: Kent Watsen Author: Rob Wilton "; description "This module contains information about the YANG server instance, including the modules and datastores the server supports, and which modules are present in which datastores. Copyright (c) 2018 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 (http://trustee.ietf.org/license-info). This version of this YANG module is part of RFC XXXX; see the RFC itself for full legal notices."; // RFC Ed.: update the date below with the date of RFC publication // and remove this note. // RFC Ed.: replace XXXX with actual RFC number and remove this // note. revision 2018-01-17 { description "Added support for multiple datastores."; reference "RFC XXXX: YANG Library."; } revision 2016-04-09 { description "Initial revision."; reference "RFC 7895: YANG Module Library."; } /* Bierman, et al. Expires July 21, 2018 [Page 10] Internet-Draft YANG Library January 2018 * Typedefs */ typedef revision-identifier { type string { pattern '\d{4}-\d{2}-\d{2}'; } description "Represents a specific date in YYYY-MM-DD format."; } /* * Groupings */ grouping module-identification-leafs { description "Parameters for identifying YANG modules and submodules."; leaf name { type yang:yang-identifier; mandatory true; description "The YANG module or submodule name."; } leaf revision { type revision-identifier; description "The YANG module or submodule revision date. If no revision statement is present in the YANG module or submodule, this leaf is not instantiated."; } } grouping location-leaf-list { description "Common location leaf list parameter for modules and submodules."; leaf-list location { type inet:uri; description "Contains a URL that represents the YANG schema resource for this module or submodule. This leaf will only be present if there is a URL available for retrieval of the schema for this entry."; } Bierman, et al. Expires July 21, 2018 [Page 11] Internet-Draft YANG Library January 2018 } grouping implementation-parameters { description "Parameters for describing the implementation of a module."; list feature { key "name"; description "List of YANG feature names from this module that are supported by the server, regardless whether they are defined in the module or any included submodule."; leaf name { type yang:yang-identifier; description "A feature supported by the server."; } } list deviation { key "module"; description "List of YANG deviation modules used by this server to modify the conformance of the module associated with this entry. Note that the same module can be used for deviations for multiple modules, so the same entry MAY appear within multiple 'module' entries."; leaf module { type leafref { path "../../name"; } description "A module that deviates the module associated with this entry."; } } } grouping module-set-parameters { description "A set of parameters that describe a module set."; leaf name { type string; description "An arbitrary name of the module set."; } leaf checksum { Bierman, et al. Expires July 21, 2018 [Page 12] Internet-Draft YANG Library January 2018 type string; config false; mandatory true; description "A server-generated checksum of the contents of the module set. The server MUST change the value of this leaf if the information represented by the module set, except 'checksum', has changed."; } list module { key "name"; description "An entry in this list represents a module implemented by the server with a particular set of supported features and deviations. The server implements one or more protocol-accessible objects defined in the YANG module identified in this entry. This includes deviation statements defined in the module."; uses module-identification-leafs; leaf namespace { type inet:uri; mandatory true; description "The XML namespace identifier for this module."; } uses location-leaf-list; list submodule { key "name"; description "Each entry represents one submodule within the parent module."; uses module-identification-leafs; uses location-leaf-list; } uses implementation-parameters; } list import-only-module { key "name revision"; description "An entry in this list indicates that the server imports reusable definitions from the specified revision of the module, but does not implement any protocol accessible Bierman, et al. Expires July 21, 2018 [Page 13] Internet-Draft YANG Library January 2018 objects from this revision. Multiple entries for the same module name MAY exist. This can occur if multiple modules import the same module, but specify different revision-dates in the import statements."; leaf name { type yang:yang-identifier; description "The YANG module name."; } leaf revision { type union { type revision-identifier; type string { length 0; } } description "The YANG module or revision date. A zero-length string is used if no revision statement is present in the YANG module."; } leaf namespace { type inet:uri; mandatory true; description "The XML namespace identifier for this module."; } uses location-leaf-list; list submodule { key "name"; description "Each entry represents one submodule within the parent module."; uses module-identification-leafs; uses location-leaf-list; } } } grouping yang-library-parameters { description "The YANG library data structure is represented as a grouping so it can be reused in configuration or another monitoring Bierman, et al. Expires July 21, 2018 [Page 14] Internet-Draft YANG Library January 2018 data structure."; list module-set { key name; description "A set of modules that may be used by one or more schemas."; uses module-set-parameters; } list schema { key "name"; description "A datastore schema that may be used by one or more datastores."; leaf name { type string; description "An arbitrary name of the schema."; } leaf checksum { type string; config false; mandatory true; description "A server-generated checksum of the contents of the schema. The server MUST change the value of this leaf if the information represented by the schema, except 'checksum', has changed."; } leaf-list module-set { type leafref { path "../../module-set/name"; } description "A set of module-sets that are included in this schema."; } } list datastore { key "name"; description "A datastore supported by this server. Each datastore indicates which schema it supports. The server MUST instantiate one entry in this list per Bierman, et al. Expires July 21, 2018 [Page 15] Internet-Draft YANG Library January 2018 specific datastore it supports. Each datstore entry with the same datastore schema SHOULD reference the same schema."; leaf name { type identityref { base ds:datastore; } description "The identity of the datastore."; } leaf schema { type leafref { path "../../schema/name"; } mandatory true; description "A reference to the schema supported by this datastore."; } } } /* * Top-level container */ container yang-library { config false; description "Container providing all the YANG meta information the server possesses."; uses yang-library-parameters; leaf checksum { type string; mandatory true; description "A server-generated checksum of the contents of the 'yang-library' tree. The server MUST change the value of this leaf if the information represented by the 'yang-library' tree, except 'yang-library/checksum', has changed."; } } Bierman, et al. Expires July 21, 2018 [Page 16] Internet-Draft YANG Library January 2018 /* * Notifications */ notification yang-library-update { description "Generated when any YANG library information on the server has changed."; } /* * Legacy groupings */ grouping module-list { status deprecated; description "The module data structure is represented as a grouping so it can be reused in configuration or another monitoring data structure."; grouping common-leafs { status deprecated; description "Common parameters for YANG modules and submodules."; leaf name { type yang:yang-identifier; status deprecated; description "The YANG module or submodule name."; } leaf revision { type union { type revision-identifier; type string { length 0; } } status deprecated; description "The YANG module or submodule revision date. A zero-length string is used if no revision statement is present in the YANG module or submodule."; } } grouping schema-leaf { status deprecated; Bierman, et al. Expires July 21, 2018 [Page 17] Internet-Draft YANG Library January 2018 description "Common schema leaf parameter for modules and submodules."; leaf schema { type inet:uri; description "Contains a URL that represents the YANG schema resource for this module or submodule. This leaf will only be present if there is a URL available for retrieval of the schema for this entry."; } } list module { key "name revision"; status deprecated; description "Each entry represents one revision of one module currently supported by the server."; uses common-leafs { status deprecated; } uses schema-leaf { status deprecated; } leaf namespace { type inet:uri; mandatory true; status deprecated; description "The XML namespace identifier for this module."; } leaf-list feature { type yang:yang-identifier; status deprecated; description "List of YANG feature names from this module that are supported by the server, regardless whether they are defined in the module or any included submodule."; } list deviation { key "name revision"; status deprecated; description "List of YANG deviation module names and revisions used by this server to modify the conformance of Bierman, et al. Expires July 21, 2018 [Page 18] Internet-Draft YANG Library January 2018 the module associated with this entry. Note that the same module can be used for deviations for multiple modules, so the same entry MAY appear within multiple 'module' entries. The deviation module MUST be present in the 'module' list, with the same name and revision values. The 'conformance-type' value will be 'implement' for the deviation module."; uses common-leafs { status deprecated; } } leaf conformance-type { type enumeration { enum implement { description "Indicates that the server implements one or more protocol-accessible objects defined in the YANG module identified in this entry. This includes deviation statements defined in the module. For YANG version 1.1 modules, there is at most one module entry with conformance type 'implement' for a particular module name, since YANG 1.1 requires that at most one revision of a module is implemented. For YANG version 1 modules, there SHOULD NOT be more than one module entry for a particular module name."; } enum import { description "Indicates that the server imports reusable definitions from the specified revision of the module, but does not implement any protocol accessible objects from this revision. Multiple module entries for the same module name MAY exist. This can occur if multiple modules import the same module, but specify different revision-dates in the import statements."; } } mandatory true; status deprecated; description "Indicates the type of conformance the server is claiming for the YANG module identified by this entry."; Bierman, et al. Expires July 21, 2018 [Page 19] Internet-Draft YANG Library January 2018 } list submodule { key "name revision"; status deprecated; description "Each entry represents one submodule within the parent module."; uses common-leafs { status deprecated; } uses schema-leaf { status deprecated; } } } } /* * Legacy operational state data nodes */ container modules-state { config false; status deprecated; description "Contains YANG module monitoring information."; leaf module-set-id { type string; mandatory true; status deprecated; description "Contains a server-specific identifier representing the current set of modules and submodules. The server MUST change the value of this leaf if the information represented by the 'module' list instances has changed."; } uses module-list { status deprecated; } } /* * Legacy notifications */ Bierman, et al. Expires July 21, 2018 [Page 20] Internet-Draft YANG Library January 2018 notification yang-library-change { status deprecated; description "Generated when the set of modules and submodules supported by the server has changed."; leaf module-set-id { type leafref { path "/yanglib:modules-state/yanglib:module-set-id"; } mandatory true; status deprecated; description "Contains the module-set-id value representing the set of modules and submodules supported at the server at the time the notification is generated."; } } } 3. IANA Considerations 3.1. YANG Module Registry RFC 7895 previously registered one URI in the IETF XML registry [RFC3688]. Following the format in RFC 3688, the following registration was made: URI: urn:ietf:params:xml:ns:yang:ietf-yang-library Registrant Contact: The NETCONF WG of the IETF. XML: N/A, the requested URI is an XML namespace. This document takes over this registration entry made by RFC 7895. RFC 7895 previously registered one YANG module in the "YANG Module Names" registry [RFC6020] as follows: name: ietf-yang-library namespace: urn:ietf:params:xml:ns:yang:ietf-yang-library prefix: yanglib reference: RFC 7895 This document takes over this registration entry made by RFC 7895. Bierman, et al. Expires July 21, 2018 [Page 21] Internet-Draft YANG Library January 2018 4. Security Considerations The YANG module defined in this document is designed to be accessed via network management protocols such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer is the secure transport layer, and the mandatory-to-implement secure transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer is HTTPS, and the mandatory-to-implement secure transport is TLS [RFC5246]. The NETCONF access control model [RFC6536] provides the means to restrict access for particular NETCONF or RESTCONF users to a preconfigured subset of all available NETCONF or RESTCONF protocol operations and content. Some of the readable data 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: o /yang-library/schema: The schema list used in a server implementation may help an attacker identify the server capabilities and server implementations with known bugs. Although some of this information may be available to all users via the NETCONF message (or similar messages in other management protocols), this YANG module potentially exposes additional details that could be of some assistance to an attacker. Server vulnerabilities may be specific to particular modules, module revisions, module features, or even module deviations. This information is included in each module entry. For example, if a particular operation on a particular data node is known to cause a server to crash or significantly degrade device performance, then the module list information will help an attacker identify server implementations with such a defect, in order to launch a denial- of-service attack on the device. 5. Acknowledgements Contributions to this material by Andy Bierman are based upon work supported by the The Space & Terrestrial Communications Directorate (S&TCD) under Contract No. W15P7T-13-C-A616. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of The Space & Terrestrial Communications Directorate (S&TCD). Bierman, et al. Expires July 21, 2018 [Page 22] Internet-Draft YANG Library January 2018 6. References 6.1. Normative References [I-D.ietf-netmod-revised-datastores] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., and R. Wilton, "Network Management Datastore Architecture", draft-ietf-netmod-revised-datastores-10 (work in progress), January 2018. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/ RFC2119, March 1997, . [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, DOI 10.17487/RFC3688, January 2004, . [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS) Protocol Version 1.2", RFC 5246, DOI 10.17487/ RFC5246, August 2008, . [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, . [RFC6536] Bierman, A. and M. Bjorklund, "Network Configuration Protocol (NETCONF) Access Control Model", RFC 6536, DOI 10.17487/RFC6536, March 2012, . [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", RFC 6991, DOI 10.17487/RFC6991, July 2013, . Bierman, et al. Expires July 21, 2018 [Page 23] Internet-Draft YANG Library January 2018 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016, . [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, . 6.2. Informative References [I-D.ietf-netmod-yang-tree-diagrams] Bjorklund, M. and L. Berger, "YANG Tree Diagrams", draft- ietf-netmod-yang-tree-diagrams-04 (work in progress), December 2017. [RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008, . [RFC6470] Bierman, A., "Network Configuration Protocol (NETCONF) Base Notifications", RFC 6470, DOI 10.17487/RFC6470, February 2012, . [RFC7895] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Module Library", RFC 7895, DOI 10.17487/RFC7895, June 2016, . Authors' Addresses Andy Bierman YumaWorks Email: andy@yumaworks.com Martin Bjorklund Tail-f Systems Email: mbj@tail-f.com Juergen Schoenwaelder Jacobs University Email: j.schoenwaelder@jacobs-university.de Bierman, et al. Expires July 21, 2018 [Page 24] Internet-Draft YANG Library January 2018 Kent Watsen Juniper Networks Email: kwatsen@juniper.net Robert Wilton Cisco Systems Email: rwilton@cisco.com Bierman, et al. Expires July 21, 2018 [Page 25]