Network Working Group A. Bierman Internet-Draft YumaWorks Intended status: Standards Track M. Bjorklund Expires: September6, 2018 Tail-f Systems9, 2019 Cisco K. WatsenJuniperWatsen Networks March5, 20188, 2019 YANG Data Structure Extensionsdraft-ietf-netmod-yang-data-ext-01draft-ietf-netmod-yang-data-ext-02 Abstract This document describes YANG mechanisms for defining abstract data structures with YANG. It is intended to replace and extend the "yang-data" extension statement defined in RFC 8040. 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 September6, 2018.9, 2019. Copyright Notice Copyright (c)20182019 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 (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 1.1.1. NMDA . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1.2. YANG . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 42.1. Restrictions on Conceptual3. YANG Data Structure Extensions Module . . . . . . . . . . . . 42.2. YANG Data Extensions Module4. IANA Considerations . . . . . . . . . . . . . . . . .4 3. IANA Considerations. . . . 9 4.1. YANG Module Registry . . . . . . . . . . . . . . . . . . 93.1. YANG Module Registry5. Security Considerations . . . . . . . . . . . . . . . . . . . 94. Security Considerations6. References . . . . . . . . . . . . . . . . . . . . . . . . . 95.6.1. Normative References . . . . . . . . . . . . . . . . . . 9 6.2. Informative References . . .9. . . . . . . . . . . . . . 10 Appendix A. Examples . . . . . . . . . . . . . . . . . . . . . . 10 A.1.yang-data"structure" Example . . . . . . . . . . . . . . . . . . ..10 A.2.augment-yang-data"augment-structure" Example . . . . . . . . . . . . . . . 11 A.3. XML Encoding Example . . . . . . . . . . . . . . . .10. . 12 A.4. JSON Encoding Example . . . . . . . . . . . . . . . . . . 12 Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . .1113 B.1. v01 to v02 . . . . . . . . . . . . . . . . . . . . . . . 13 B.2. v00 to v01 . . . . . . . . . . . . . . . . . . . . . . .1113 Appendix C. Open Issues . . . . . . . . . . . . . . . . . . . .1113 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . .1113 1. Introduction There is a need for standard mechanisms to allow the definition of abstract data that is not intended to be implemented as configuration or operational state. The "yang-data" extension statement from RFC 8040 [RFC8040]iswas defined for thispurpose, howeverpurpose but it is limited in its functionality. The intended use of the "yang-data" extensioniswas to model all or part of a protocol message, such as the "errors" definition inietf- restconf.yangthe YANG module "ietf-restconf" [RFC8040], or the contents of a file. However, protocols are often layered such that the header or payload portions of the message can be extended by external documents. The YANG statements that model a protocol need to support this extensibility that is already found in that protocol. The "yang-data" extension from [RFC8040] has been copied here, renamed to "structure", and updated to be more flexible. There is no assumption that a YANG data structure can only be used as a top-level abstraction, instead of nested within some other data structure. This document also defines a new YANG extension statement called"augment-yang-data","augment-structure", which allows abstract data structures to be augmented from external modules, similar to the existing YANG "augment" statement. Note that "augment" cannot be used to augment ayangYANG data structure since a YANG compiler or other tool is not required to understand the"yang-data""structure" extension.The "yang-data" extension from [RFC8040] has been copied here and updated to be more flexible. There is no longer a requirement for the "yang-data" statement to result in exactly one container object. There is no longer an assumption that a yang data structure can only be used as a top-level abstraction, instead of nested within some other data structure.1.1. Terminology 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[RFC2119].BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all capitals, as shown here. The following terms are used within this document: oyangYANG data structure: A data structure defined with the"yang-data""structure" statement. 1.1.1. NMDA The following terms are defined in the Network Management Datastore Architecture (NMDA)[I-D.ietf-netmod-revised-datastores].[RFC8342]. and are not redefined here: o configuration o operational state 1.1.2. YANG The following terms are defined in [RFC7950]: o absolute-schema-nodeid o container o data definition statement o data node o leaf o leaf-list o list 2. Definitions2.1. Restrictions on ConceptualA YANG DataThis document places restrictions onStructure is defined with the"yang-data" external statements that can be used with"structure" extension statement, defined in the"yang-data" and "augment-yang-data" extensions.YANG module "ietf-yang-structure-ext". Theconceptualargument to the "structure" extension statement is the name of the datadefinitionsstructure. The data structures are considered to be in the same identifier namespace as defined in section 6.2.1 of [RFC7950]. In particular, bullet 7: All leafs, leaf-lists, lists, containers, choices, rpcs, actions, notifications, anydatas, and anyxmls defined (directly or through a "uses" statement) within a parent node or at the top level of the module or its submodules share the same identifier namespace. This means thatconceptualdata structures defined with the"yang-data" or "augment-yang-data" statements"structure" statement cannot have the samelocal-namename as sibling nodes from regular YANG data definition statements or other"yang-data" or "augment-yang-data" statements."structure" statements in the same YANG module. This does not mean ayangYANG data structure has to be used as a top- level protocol message or other top-level data structure.A yang data structure does not have to result in a single container. 2.2.3. YANG Data Structure Extensions ModuleThe "ietf-yang-data-ext" module defines the "augment-yang-data" extension to augment conceptual data already defined with the "yang-data" extension. The RESTCONF "yang-data" extension has been moved to this document and updated.RFC Ed.: update the date below with the date of RFC publication and remove this note. <CODE BEGINS> file"ietf-yang-data-ext@2018-03-05.yang""ietf-yang-structure-ext@2019-03-07.yang" moduleietf-yang-data-extietf-yang-structure-ext { yang-version 1.1; namespace"urn:ietf:params:xml:ns:yang:ietf-yang-data-ext";"urn:ietf:params:xml:ns:yang:ietf-yang-structure-ext"; prefix"yd";sx; organization "IETF NETMOD (NETCONF Data Modeling Language) Working Group"; contact "WG Web: <http://tools.ietf.org/wg/netmod/> WG List: <mailto:netmod@ietf.org> Author: Andy Bierman <mailto:andy@yumaworks.com> Author: Martin Bjorklund <mailto:mbj@tail-f.com> Author: Kent Watsen<mailto:kwatsen@juniper.net>";<mailto:kent+ietf@watsen.net>"; description "This module contains conceptual YANG specifications for defining abstract'yang-data'data structures. 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)2017 - 20182019 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)."; // RFC Ed.: update the date below with the date of RFC publication // and remove this note. revision2018-03-052019-03-07 { description "Initial revision.";reference// RFC Ed.: replace XXXX with RFC number and remove this note reference "RFC XXXX: YANGDataStructure Extensions."; } extensionyang-datastructure { argument name { yin-element true; } description "This extension is used to specify a YANG datatemplate whichstructure that represents conceptual data defined in YANG. It is intended to describe hierarchical data independent of protocol context or specific message encoding format. Data definition statements within ayang-data'structure' extension statement specify the generic syntax for the specific YANG datatemplate,structure, whose name is the argument of theyang-data'structure' extension statement. Note that this extension does not define a media-type. A specification using this extension MUST specify the message encoding rules, including the content mediatype.type, if applicable. The mandatory 'name' parameter value identifies the YANG datatemplatestructure that is being defined.It contains the template name. This parameter is only used for readability purposes. There are no mechanisms to reuse yang-data by its template name value.This extension isignored unless it appearsonly valid as a top-levelstatement. It MUST contain data definition statements that result instatement, i.e., given as asetsub-statement to 'module' or 'submodule'. The sub-statements ofdata definition statements. Ifthis extension MUST follow theyang data template is intended to be used as a top-level structure, thenABNF rules below, where theyangrules are defined in RFC 7950: *must-stmt [status-stmt] [description-stmt] [reference-stmt] *(typedef-stmt / grouping-stmt) *data-def-stmt A YANG datatemplate needs to resultstructure defined with this extension statement is encoded ina single container, sothe same way as aninstance'anydata' statement. This means that the name of theYANG data template can thus be translated into an XML instance document, whose top-level element corresponds tostructure is encoded as a 'container', with thetop-level container.instantiated child statements encoded as child nodes to this node. The module name and namespace value for the YANG module using the extension statement is assigned to each of the data definition statements resulting from theyang data template. The name of each data definition statement resulting from a yang data template is assigned to a top-level identifier name in the data node identifier namespace, according to RFC 7950, section 6.2.1. The sub-statements of this extension MUST follow the 'data-def-stmt' rule in theYANGABNF.data structure. The XPath documentrootelement is the extension statement itself, such that the child nodes of the documentrootelement are represented by the data-def-stmt sub-statements within this extension. This conceptual document is the context for the following YANG statements: - must-stmt - when-stmt - path-stmt - min-elements-stmt - max-elements-stmt - mandatory-stmt - unique-stmt - ordered-by - instance-identifier data type The following data-def-stmt sub-statements are constrained when used within ayang-data-resource'structure' extension statement. - The list-stmt is not required to have a key-stmt defined. - Theif-feature-stmt is ignored if present. - Theconfig-stmt is ignored if present.- The available identity values for any 'identityref' leaf or leaf-list nodes is limited to the module containing this extension statement, and the modules imported into that module."; } extensionaugment-yang-dataaugment-structure { argument path { yin-element true; } description "This extension is used to specify an augmentation toconceptualYANG data structure defined with the'yang-data''structure' statement. It is intended to describe hierarchical data independent of protocol context or specific message encoding format. This statement has almost the same structure as the 'augment-stmt'. Data definition statements within this statement specify the semantics and generic syntax for the additional data to be added to the specific YANG datatemplate,structure, identified by the 'path' argument. The mandatory 'path' parameter value identifies the YANGconceptual data node that is being augmented, represented as an absolute-schema-nodeid string.conceptual data node that is being augmented, represented as an absolute-schema-nodeid string, where the first node in the absolute-schema-nodeid string identifies the YANG data structure to augment, and the rest of the nodes in the string identifies the node within the YANG structure to augment. This extension isignored unless it appearsonly valid as a top-levelstatement.statement, i.e., given as a sub-statement to 'module' or 'submodule'. The sub-statements of this extension MUST follow the'data-def-stmt' rule inABNF rules below, where theYANG ABNF.rules are defined in RFC 7950: [status-stmt] [description-stmt] [reference-stmt] 1*(data-def-stmt / case-stmt) The module name and namespace value for the YANG module using the extension statement is assigned to instance document data conforming to the data definition statements within this extension. The XPath documentrootelement is the augmented extension statement itself, such that the child nodes of the documentrootelement are represented by the data-def-stmt sub-statements within the augmentedyang-data'structure' statement. The context node of theaugment-yang-data'augment-structure' statement is derived in the same way as the 'augment' statement, as defined in section 6.4.1 of [RFC7950]. This conceptual node is considered the context node for the following YANG statements: - must-stmt - when-stmt - path-stmt - min-elements-stmt - max-elements-stmt - mandatory-stmt - unique-stmt - ordered-by - instance-identifier data type The following data-def-stmt sub-statements are constrained when used withina augment-yang-dataan 'augment-structure' extension statement. - The list-stmt is not required to have a key-stmt defined. - Theif-feature-stmt is ignored if present. - Theconfig-stmt is ignored if present.- The available identity values for any 'identityref' leaf or leaf-list nodes is limited to the module containing this extension statement, and the modules imported into that module.Example:foo.yangmodule foo { importyang-data-extietf-yang-structure-ext { prefixyd;sx; }yd:yang-datasx:structure foo-data { container foo-con { } } }bar.yangmodule bar { importyang-data-extietf-yang-structure-ext { prefixyd;sx; } import foo { prefix foo; }yd:augment-yang-data /foo:foo-consx:augment-structure /foo:foo-data/foo:foo-con { leaf add-leaf1 { type int32; } leaf add-leaf2 { type string; } } } "; } } <CODE ENDS>3.4. IANA Considerations3.1.4.1. YANG Module Registry This document registers one URI as a namespace in the "IETF XML Registry" [RFC3688]: URI:urn:ietf:params:xml:ns:yang:ietf-yang-data-exturn:ietf:params:xml:ns:yang:ietf-yang-structure-ext Registrant Contact: The IESG. XML: N/A; the requested URI is an XML namespace. This document registers one YANG module in the "YANG Module Names" registry [RFC6020]: name:ietf-yang-data-extietf-yang-structure-ext namespace:urn:ietf:params:xml:ns:yang:ietf-yang-data-exturn:ietf:params:xml:ns:yang:ietf-yang-structure-ext prefix:ydsx // RFC Ed.: replace XXXX with RFC number and remove this note reference: RFC XXXX4.5. Security Considerations This document defines YANG extensions that are used to define conceptual YANGdata.data structures. It does not introduce any new vulnerabilities beyond those specified in YANG 1.1 [RFC7950].5.6. 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, March1997. [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, January 2004. [RFC6020] Bjorklund, M., "YANG - A Data Modeling Language for the Network Configuration Protocol (NETCONF)", RFC 6020, October 2010.1997, <https://www.rfc-editor.org/info/ rfc2119>. [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", RFC 7950, DOI 10.17487/RFC7950, August 2016,<http://www.rfc-editor.org/info/rfc7950>.<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,<http://www.rfc-editor.org/info/rfc8040>.<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>. [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>. 6.2. Informative References [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>. Appendix A. Examples A.1.yang-data"structure" Example This example shows a simple address book that could be stored as an artifact.yd:yang-data example-address-bookmodule example-module {containeryang-version 1.1; namespace "urn:example:example-module"; prefix exm; import ietf-yang-structure-ext { prefix sx; } sx:structure address-book { list address { key "last first"; leaf last { type string; description "Last name"; } leaf first { type string; description "First name"; } leaf street { type string; description "Street name"; } leaf city { type string; description "City name"; } leaf state { type string; description "State name"; } } } } A.2.augment-yang-data"augment-structure" Example This example adds "county" and "zipcode" leafs to the address book:yd:augment-yang-data /address-book/addressmodule example-module-aug { yang-version 1.1; namespace "urn:example:example-module-aug"; prefix exma; import ietf-yang-structure-ext { prefix sx; } import example-module { prefix exm; } sx:augment-structure "/exm:address-book/exm:address" { leaf county { type string; description "County name"; } leaf zipcode { type string; description "Postal zipcode"; } } } A.3. XML Encoding Example This example shows how an address book can be encoded in XML: <address-book xmlns="urn:example:example-module"> <address> <last>Flintstone</last> <first>Fred</first> <street>301 Cobblestone Way</street> <city>Bedrock</city> <zipcode xmlns="urn:example:example-module-aug">70777</zipcode> </address> </address-book> A.4. JSON Encoding Example This example shows how an address book can be encoded in JSON: "example-module:address-book": { "address": [ { "city": "Bedrock", "example-module-aug:zipcode": "70777", "first": "Fred", "last": "Flintstone", "street": "301 Cobblestone Way" } ] } Appendix B. Change Log RFC Ed.: remove this section before publication. B.1. v01 to v02 o terminology fixes (use the term "structure" instead of "template") o renamed the statement to "structure" from "yang-data" o removed limitations on if-feature and identities in YANG structures B.2. v00 to v01 o moved open issues to github o added examples section o filled in IANA considerations Appendix C. Open Issues RFC Ed.: remove this section before publication. The YANG Data Structure Extensions issues are tracked on github.com: https://github.com/netmod-wg/yang-data-ext/issues Authors' Addresses Andy Bierman YumaWorks Email: andy@yumaworks.com Martin BjorklundTail-f SystemsCisco Email: mbj@tail-f.com Kent WatsenJuniperWatsen Networks Email:kwatsen@juniper.netkent+ietf@watsen.net