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2 Netmod B. Lengyel
3 Internet-Draft Ericsson
4 Intended status: Standards Track B. Claise
5 Expires: 20 March 2022 Huawei
6 16 September 2021
8 YANG Instance Data File Format
9 draft-ietf-netmod-yang-instance-file-format-19
11 Abstract
13 There is a need to document data defined in YANG models at design
14 time, implementation time or when a live server is unavailable. This
15 document specifies a standard file format for YANG instance data,
16 which follows the syntax and semantics of existing YANG models, and
17 annotates it with metadata.
19 Status of This Memo
21 This Internet-Draft is submitted in full conformance with the
22 provisions of BCP 78 and BCP 79.
24 Internet-Drafts are working documents of the Internet Engineering
25 Task Force (IETF). Note that other groups may also distribute
26 working documents as Internet-Drafts. The list of current Internet-
27 Drafts is at https://datatracker.ietf.org/drafts/current/.
29 Internet-Drafts are draft documents valid for a maximum of six months
30 and may be updated, replaced, or obsoleted by other documents at any
31 time. It is inappropriate to use Internet-Drafts as reference
32 material or to cite them other than as "work in progress."
34 This Internet-Draft will expire on 20 March 2022.
36 Copyright Notice
38 Copyright (c) 2021 IETF Trust and the persons identified as the
39 document authors. All rights reserved.
41 This document is subject to BCP 78 and the IETF Trust's Legal
42 Provisions Relating to IETF Documents (https://trustee.ietf.org/
43 license-info) in effect on the date of publication of this document.
44 Please review these documents carefully, as they describe your rights
45 and restrictions with respect to this document. Code Components
46 extracted from this document must include Simplified BSD License text
47 as described in Section 4.e of the Trust Legal Provisions and are
48 provided without warranty as described in the Simplified BSD License.
50 Table of Contents
52 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
53 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
54 1.2. Principles . . . . . . . . . . . . . . . . . . . . . . . 4
55 1.3. Delivery of Instance Data . . . . . . . . . . . . . . . . 4
56 1.4. Data Life cycle . . . . . . . . . . . . . . . . . . . . . 5
57 2. Instance Data File Format . . . . . . . . . . . . . . . . . . 5
58 2.1. Specifying the Content Schema . . . . . . . . . . . . . . 7
59 2.1.1. Inline Method . . . . . . . . . . . . . . . . . . . . 7
60 2.1.2. Simplified-Inline Method . . . . . . . . . . . . . . 8
61 2.1.3. URI Method . . . . . . . . . . . . . . . . . . . . . 8
62 2.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 8
63 2.2.1. Documentation of server capabilities . . . . . . . . 8
64 2.2.2. Preloading default configuration data . . . . . . . . 10
65 2.2.3. Storing diagnostics data . . . . . . . . . . . . . . 11
66 3. YANG Instance Data Model . . . . . . . . . . . . . . . . . . 12
67 3.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 12
68 3.2. YANG Model . . . . . . . . . . . . . . . . . . . . . . . 13
69 4. Security Considerations . . . . . . . . . . . . . . . . . . . 19
70 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
71 5.1. URI Registration . . . . . . . . . . . . . . . . . . . . 20
72 5.2. YANG Module Name Registration . . . . . . . . . . . . . . 20
73 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
74 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
75 7.1. Normative References . . . . . . . . . . . . . . . . . . 20
76 7.2. Informative References . . . . . . . . . . . . . . . . . 22
77 Appendix A. Changes between revisions . . . . . . . . . . . . . 23
78 Appendix B. Backwards Compatibility . . . . . . . . . . . . . . 26
79 Appendix C. Detailed Use Cases . . . . . . . . . . . . . . . . . 26
80 C.1. Use Case 1: Early Documentation of Server Capabilities . 26
81 C.2. Use Case 2: Preloading Data . . . . . . . . . . . . . . . 27
82 C.3. Use Case 3: Documenting Factory Default Settings . . . . 28
83 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
85 1. Introduction
87 There is a need to document data defined in YANG models when a live
88 server is unavailable. Data is often needed at design,
89 implementation time or when a live running server is unavailable. To
90 facilitate this offline delivery of data, this document specifies a
91 standard format for YANG instance data sets and YANG instance data
92 files. The format of the instance data set is defined by the "ietf-
93 yang-instance-data" YANG module, see Section 3. The YANG data model
94 in this document conforms to the Network Management Datastore
95 Architecture (NMDA) defined in [RFC8342]
96 The following is a list of already implemented and potential use
97 cases.
99 UC1 Documentation of server capabilities
101 UC2 Preloading default configuration data
103 UC3 Documenting Factory Default Settings
105 UC4 Storing the configuration of a device, e.g., for backup, archive
106 or audit purposes
108 UC5 Storing diagnostics data
110 UC6 Allowing YANG instance data to potentially be carried within
111 other IPC message formats
113 UC7 Default instance data used as part of a templating solution
115 UC8 Providing data examples in RFCs or internet drafts
117 In Appendix C describes the first three use cases in detail.
119 There are many and varied use cases where YANG instance data could be
120 used. This document does not limit future uses of instance data
121 sets, so specifying how and when to use YANG instance data is out of
122 scope for this document. It is anticipated that other documents will
123 define specific use cases. Use cases are listed only as examples.
125 1.1. Terminology
127 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
128 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
129 "OPTIONAL" in this document are to be interpreted as described in BCP
130 14 [RFC2119] [RFC8174] when, and only when, they appear in all
131 capitals, as shown here.
133 Instance Data: A collection of instantiated data nodes.
135 Instance Data Set: A named set of data items annotated with metadata
136 that can be used as instance data in a YANG data tree.
138 Instance Data File: A file containing an instance data set formatted
139 according to the rules described in this document.
141 Content-schema: A set of YANG modules with their revision, supported
142 features, and deviations for which the instance data set contains
143 instance data.
145 Content defining YANG module: an individual YANG module that is part
146 of the content-schema.
148 The term "server" is used as defined in [RFC8342].
150 1.2. Principles
152 The following is a list of the basic principles of the instance data
153 format:
155 P1 Two standard formats shall be defined based on the XML and JSON
156 encodings.
158 P2 Instance data shall reuse existing encoding rules for YANG
159 defined data.
161 P3 Metadata about the instance data set (Section 2, Paragraph 12)
162 shall be defined.
164 P4 A YANG instance data set shall be allowed to contain data for
165 multiple YANG modules.
167 P5 Instance data shall be allowed to contain configuration data,
168 state data, or a mix of the two.
170 P6 Partial data sets shall be allowed.
172 P7 The YANG instance data format shall be usable for any data for
173 which YANG module(s) are defined and available to the reader,
174 independent of whether the module is implemented by a server.
176 P8 It shall be possible to report the identity of the datastore with
177 which the instance data set is associated.
179 1.3. Delivery of Instance Data
181 Instance data sets that are produced as a result of some sort of
182 specification or design effort may be available without the need for
183 a live server e.g., via download from the vendor's website, or in any
184 other way that product documentation is distributed.
186 Other instance data sets may be read from or produced by the YANG
187 server itself e.g., UC5 documenting diagnostic data.
189 1.4. Data Life cycle
191 A YANG instance data set is created at a specific point of time. If
192 the data changes afterwards, this is not represented in the instance
193 data set anymore. The current values may be retrieved at run-time
194 via NETCONF/RESTCONF or received e.g., in YANG-Push notifications.
196 Whether the instance data changes and if so, when and how, should be
197 described either in the instance data set's description statement or
198 in some other implementation specific manner.
200 2. Instance Data File Format
202 A YANG instance data file MUST contain a single instance data set and
203 no additional data.
205 The format of the instance data set is defined by the "ietf-yang-
206 instance-data" YANG module. It is made up of a header part and
207 content-data. The header part carries metadata for the instance data
208 set. The content-data, defined as an anydata data node, carries the
209 instance data that the user wants to document/provide. The syntax
210 and semantics of content-data is defined by the content-schema.
212 Two formats are specified based on the XML and JSON YANG encodings.
213 Later, as other YANG encodings (e.g., CBOR) are defined, further
214 instance data formats may be specified.
216 The content-data part MUST conform to the content-schema, while
217 allowing for the exceptions listed below. The content-data part
218 SHALL follow the encoding rules defined in [RFC7950] for XML and
219 [RFC7951] for JSON and MUST use UTF-8 character encoding. Content-
220 data MAY include:
222 * metadata, as defined by [RFC7952].
224 * origin metadata, as specified in [RFC8526] and [RFC8527]
226 * implementation specific metadata relevant to individual data
227 nodes. Unknown metadata MUST be ignored by users of instance
228 data, allowing it to be used later for other purposes.
230 An instance data set MAY contain data for any number of YANG modules;
231 if needed it MAY carry the complete configuration and state data for
232 a server. Default values should be excluded where they do not
233 provide additional useful data.
235 Configuration ("config true") and operational state data ("config
236 false") MAY be mixed in the instance data file.
238 Instance data files MAY contain partial data sets. This means
239 "mandatory", "min-elements", "require-instance true", "must" and
240 "when" constrains MAY be violated.
242 The name of the instance data file SHOULD be of the form:
244 instance-data-set-name ['@' ( revision-date / timestamp ) ]
245 ( '.xml' / '.json' )
247 E.g., acme-router-modules.xml
248 E.g., acme-router-modules@2018-01-25.xml
249 E.g., acme-router-modules@2018-01-25T15_06_34_3+01_00.json
251 If the leaf "name" is present in the instance data header, its value
252 SHOULD be used for the "instance-data-set-name". If the "revision-
253 date" is present in the filename it MUST conform to the format of the
254 revision-date leaf in the YANG model. If the "revision-date" is
255 present in both the filename and in the instance data header, the
256 revision date in the file name MUST be set to the latest revision
257 date inside the instance data set. If the "timestamp" is present in
258 the filename it MUST conform to the format of the timestamp leaf in
259 the YANG model except for replacing colons as described below. If
260 the "timestamp" is present both in the filename and in the instance
261 data header, the timestamp in the file name SHOULD be set to the
262 timestamp inside the instance data set; any colons, if present, shall
263 be replaced by underscores.
265 Metadata, information about the data set itself SHOULD be included in
266 the instance data set. Some metadata items are defined in the YANG
267 module "ietf-yang-instance-data", but other items MAY be used.
269 Metadata MUST include:
271 - Version of the YANG Instance Data format
273 Metadata SHOULD include:
275 - Name of the data set
277 - Content schema specification (i.e., the "content-schema" node)
279 - Description of the instance data set. The description SHOULD
280 contain information whether and how the data can change during
281 the lifetime of the server
283 - An indication whether default values are included. The default
284 handling uses the concepts defined in [RFC6243], however as
285 only concepts are re-used, users of instance data sets, do not
286 need to support RFC 6243.
288 2.1. Specifying the Content Schema
290 To properly understand and use an instance data set, the user needs
291 to know the content-schema. One of the following methods SHOULD be
292 used:
294 Simplified-Inline method: Include the needed information as part
295 of the instance data set; short specification.
297 Inline method: Include the needed information as part of the
298 instance data set.
300 URI method: Include a URI that references another YANG instance
301 data file. This instance data file will use the same content-
302 schema as the referenced YANG instance data file. (if you don't
303 want to repeat the info again and again)
305 External Method: Do not include the "content-schema" node; the
306 user needs to obtain the information through external documents.
308 Additional methods e.g., a YANG-package based solution may be added
309 later.
311 Note, the specified content-schema only indicates the set of modules
312 that were used to define this YANG instance data set. Sometimes
313 instance data may be used for a server supporting a different YANG
314 module set (e.g., for the "Preloading default configuration data"
315 use-case, UC2 in Section 1, the instance data set may not be updated
316 every time the YANG modules on the server are updated). Whether an
317 instance data set originally defined using a specific content-schema
318 is usable with a different other schema depends on many factors
319 including the amount of differences and the compatibility between the
320 original and the other schema, considering modules, revisions,
321 features, deviations, the scope of the instance data, etc.
323 2.1.1. Inline Method
325 The inline-yang-library anydata data node carries instance data
326 (conforming to ietf-yang-library@2019-01-04) that specifies the
327 content defining YANG modules including revision, supported features,
328 deviations and any relevant additional data. An example of the
329 "inline" method is provided in Figure 1.
331 2.1.2. Simplified-Inline Method
333 The instance data set contains a list of content defining YANG
334 modules including the revision date for each. Usage of this method
335 implies that the modules are used without any deviations and with all
336 features supported. YANG modules that are only required to satisfy
337 import-only dependencies MAY be excluded from the leaf-list. If they
338 are excluded then the consumer of the instance data set has to apply
339 the YANG language rules to resolve the imports. An example of the
340 "simplified-inline" method is provided in Figure 2.
342 2.1.3. URI Method
344 The "same-schema-as-file" leaf SHALL contain a URI that references
345 another YANG instance data file. The current instance data file will
346 use the same content schema as the referenced file.
348 The referenced instance data file MAY have no content-data if it is
349 used solely for specifying the content-schema.
351 If a referenced instance data file is unavailable, content-schema is
352 unknown.
354 The URI method is advantageous when the user wants to avoid the
355 overhead of specifying the content-schema in each instance data file:
356 E.g., In UC6, when the system creates a diagnostic file every minute
357 to document the state of the server.
359 An example of the "URI" method is provided in Figure 3.
361 2.2. Examples
363 2.2.1. Documentation of server capabilities
365 The example file acme-router-modules@2021-09-16.xml reflects UC1 in
366 Section 1. It provides a list of supported YANG modules and NETCONF
367 capabilities for a server. It uses the "inline" method to specify
368 the content-schema.
370 The example uses artwork folding [RFC8792].
372 ========== NOTE: '\' line wrapping per RFC 8792 ===========
374
375
377 acme-router-modules
378
379
380
382
383 ietf-yang-library
384 2019-01-04
385
386
387 ietf-netconf-monitoring
388 2010-10-04
389
390
391
392
393
394 1956-10-23
395 Initial version
396
397 Defines the minimal set of modules that any \
398 acme-router will contain.
399 info@acme.com
400
401
403
404 ietf-yang-library
405 2019-01-04
406 \
407 urn:ietf:params:xml:ns:yang:ietf-yang-library\
408
409 implement
410
411
412 ietf-system
413 2014-08-06
414 urn:ietf:params:xml:ns:yang:ietf-system
415 sys:authentication
416 sys:local-users
417
418 acme-system-ext
419 2018-08-06
420
421 implement
422
423
424 ietf-netconf-monitoring
425 2010-10-04
426 \
427 urn:ietf:params:xml:ns:yang:ietf-netconf-monitoring\
428
429 implement
430
431
432 ietf-yang-types
433 2013-07-15
434 urn:ietf:params:xml:ns:yang:ietf-yang-types\
435
436 import
437
438
439 acme-system-ext
440 2018-08-06
441 urn:rdns:acme.com:oammodel:acme-system-ext\
442
443 implement
444
445
446
448
449 \
450 urn:ietf:params:netconf:capability:validate:1.1\
451
452
453
454
455
457 Figure 1
459 2.2.2. Preloading default configuration data
461 The example file read-only-acm-rules@2021-09-16.xml reflects UC2 in
462 Section 1. It provides a default rule set for a read-only operator
463 role. It uses the "simplified-inline" method for specifying the
464 content-schema.
466
467
469 read-only-acm-rules
470
471 ietf-netconf-acm@2018-02-14
472
473
474 1776-07-04
475 Initial version
476
477 Access control rules for a read-only role.
478
479
480 true
481 deny
482 deny
483
484 read-only-role
485 read-only-group
486
487 read-all
488 *
489 read
490 permit
491
492
493
494
495
497 Figure 2
499 2.2.3. Storing diagnostics data
501 The example file acme-router-netconf-
502 diagnostics@2018-01-25T17_00_38Z.json reflects UC5 in Section 1. An
503 instance data set is produced by the server every 15 minutes that
504 contains statistics about the NETCONF server. As a new set is
505 produced periodically many times a day a revision-date would be
506 useless; instead a timestamp is included.
508 {
509 "ietf-yang-instance-data:instance-data-set": {
510 "name": "acme-router-netconf-diagnostics",
511 "content-schema": {
512 "same-schema-as-file": "file:///acme-diagnostics-schema.json"
513 },
514 "timestamp": "2018-01-25T17:00:38Z",
515 "description": ["NETCONF statistics"],
516 "content-data": {
517 "ietf-netconf-monitoring:netconf-state": {
518 "statistics": {
519 "netconf-start-time ": "2018-12-05T17:45:00Z",
520 "in-bad-hellos ": "32",
521 "in-sessions ": "397",
522 "dropped-sessions ": "87",
523 "in-rpcs ": "8711",
524 "in-bad-rpcs ": "408",
525 "out-rpc-errors ": "408",
526 "out-notifications": "39007"
527 }
528 }
529 }
530 }
531 }
533 Figure 3
535 3. YANG Instance Data Model
537 3.1. Tree Diagram
539 The following tree diagram [RFC8340] provides an overview of the data
540 model.
542 module: ietf-yang-instance-data
544 structure instance-data-set:
545 +-- name? string
546 +-- format-version? string
547 +-- includes-defaults? enumeration
548 +-- content-schema
549 | +-- (content-schema-spec)?
550 | +--:(simplified-inline)
551 | | +-- module* module-with-revision-date
552 | +--:(inline)
553 | | +-- inline-yang-library
554 | +--:(uri)
555 | +-- same-schema-as-file? inet:uri
556 +-- description* string
557 +-- contact? string
558 +-- organization? string
559 +-- datastore? ds:datastore-ref
560 +-- revision* [date]
561 | +-- date string
562 | +-- description? string
563 +-- timestamp? yang:date-and-time
564 +-- content-data?
566 3.2. YANG Model
568 This YANG module imports typedefs from [RFC6991], [RFC6243],
569 identities from [RFC8342] and the "structure" extension from
570 [RFC8791]. It also references [RFC8525].
572 file "ietf-yang-instance-data@2021-09-16.yang"
573 // RFC Ed.: replace the date above if the module gets changed in
574 //anyway during reviews or RFC editor process and remove this note
575 module ietf-yang-instance-data {
576 yang-version 1.1;
577 namespace "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data";
578 prefix yid;
580 import ietf-yang-structure-ext {
581 prefix sx;
582 reference
583 "YANG Data Structure Extensions:
584 draft-ietf-netmod-yang-data-ext-05";
585 }
586 import ietf-datastores {
587 prefix ds;
588 reference
589 "RFC 8342: Network Management Datastore Architecture (NMDA)";
591 }
592 import ietf-inet-types {
593 prefix inet;
594 reference
595 "RFC 6991: Common YANG Data Types";
596 }
597 import ietf-yang-types {
598 prefix yang;
599 reference
600 "RFC 6991: Common YANG Data Types";
601 }
603 import ietf-netconf-with-defaults {
604 prefix ncwd;
605 reference
606 "RFC 6243: With-defaults Capability for NETCONF";
607 }
609 organization
610 "IETF NETMOD Working Group";
611 contact
612 "WG Web:
613 WG List:
615 Author: Balazs Lengyel
616
618 Author: Benoit Claise
619 ";
620 description
621 "The module defines the structure and content of YANG
622 instance data sets.
624 The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
625 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
626 'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
627 are to be interpreted as described in BCP 14 (RFC 2119)
628 (RFC 8174) when, and only when, they appear in all
629 capitals, as shown here.
631 Copyright (c) 2021 IETF Trust and the persons identified as
632 authors of the code. All rights reserved.
634 Redistribution and use in source and binary forms, with or
635 without modification, is permitted pursuant to, and subject
636 to the license terms contained in, the Simplified BSD License
637 set forth in Section 4.c of the IETF Trust's Legal Provisions
638 Relating to IETF Documents
639 (http://trustee.ietf.org/license-info).
641 This version of this YANG module is part of RFC XXXX; see
642 the RFC itself for full legal notices.";
643 // RFC Ed.: replace XXXX with RFC number and remove this note
645 revision 2021-09-16 {
646 // RFC Ed.: replace the date above if the module gets changed in
647 // anyway during reviews or RFC editor process and remove
648 //this note
649 description
650 "Initial revision.";
651 reference
652 "RFC XXXX: YANG Instance Data Format";
653 // RFC Ed.: replace XXXX with RFC number and remove this note
654 }
656 typedef module-with-revision-date {
657 type string {
658 pattern '[a-zA-Z_][a-zA-Z0-9\-_.]*'
659 + '(@\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1]))?';
660 pattern '.|..|[^xX].*|.[^mM].*|..[^lL].*';
661 }
662 description
663 "A type defining a module name and an optional revision
664 date, e.g. ietf-yang-library@2019-01-04";
665 }
667 sx:structure "instance-data-set" {
668 description
669 "A data structure to define a format for YANG instance
670 data. The majority of the YANG nodes provide meta-data
671 about the instance data; the instance data itself is
672 is contained only in the 'content-data' node.";
673 leaf name {
674 type string;
675 description
676 "An arbitrary name for the YANG instance data set. This
677 value is primarily used for descriptive purposes. However,
678 when the instance data set is saved to a file, then the
679 filename MUST encode the name's value, per Section 3
680 of RFC XXXX.";
681 // RFC Ed.: replace XXXX with RFC number and remove this note
682 }
683 leaf format-version {
684 type string {
685 pattern '\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1])';
686 }
687 default "2021-09-16";
688 // RFC Ed.: replace the date above if the module gets changed
689 // in anyway during reviews or RFC editor process and remove
690 // this note
691 description
692 "The 'revision' of the 'ietf-yang-instance-data' module
693 used to encode this 'instance-data-set'.";
694 }
695 leaf includes-defaults {
696 type ncwd:with-defaults-mode;
697 default report-all;
698 description "
699 Indicates how data nodes with default values are
700 represented for all data nodes contained in the
701 instance-data-set.
703 It uses the same definitions as per section 3 of RFC 6243,
704 but applied in the context of an instance data file rather
705 than a NETCONF request using the
706 parameter.
708 For JSON files, the encoding of the 'report-all-tagged'
709 option is as defined in section 4.8.9 of RFC 8040.";
710 reference "With-defaults Capability for NETCONF, RFC 6243.";
711 }
712 container content-schema {
713 description
714 "The content schema (i.e., YANG modules) used to create
715 the instance data set.
716 If not present the user needs to obtain the information
717 through external documents.";
718 choice content-schema-spec {
719 description
720 "Specification of the content-schema.";
721 case simplified-inline {
722 leaf-list module {
723 type module-with-revision-date;
724 min-elements 1;
725 description
726 "The list of content defining YANG modules.
728 The value SHALL start with the module name.
729 If the module contains a revision statement the
730 revision date SHALL be included in the leaf-list
731 entry.
733 E.g., ietf-yang-library@2019-01-04
734 Usage of this leaf-list implies the modules are
735 used without any deviations and with all features
736 supported. Multiple revisions of the same module
737 MUST NOT be specified.";
738 }
739 }
740 case inline {
741 anydata inline-yang-library {
742 mandatory true;
743 description
744 "Instance data corresponding to the
745 ietf-yang-library@2019-01-04 defining
746 the set of content defining YANG modules for
747 this instance-data-set.";
748 }
749 }
750 case uri {
751 leaf same-schema-as-file {
752 type inet:uri;
753 description
754 "A reference to another YANG instance data file.
755 This instance data file uses the same
756 content schema as the referenced file.
758 Referenced files using the 'inline' or the
759 'simplified-inline' methods MUST be supported.
760 Referenced files using the 'URI Method' MAY be
761 supported.
763 The URL schemes 'file://' and 'https://' MUST
764 be supported, other schemes MAY also be
765 supported.";
766 }
767 }
768 }
769 }
770 leaf-list description {
771 type string;
772 description
773 "Description of the instance data set.";
774 }
775 leaf contact {
776 type string;
777 description
778 "Contact information for the person or
779 organization to whom queries concerning this
780 instance data set should be sent.";
781 }
782 leaf organization {
783 type string;
784 description
785 "Organization responsible for the instance
786 data set.";
787 }
788 leaf datastore {
789 type ds:datastore-ref;
790 description
791 "The identity of the datastore with which the
792 instance data set is associated, e.g., the datastore from
793 where the data was read or the datastore into which the data
794 may be loaded or the datastore which is being documented.
795 If a single specific datastore cannot be specified, the
796 leaf MUST be absent.
798 If this leaf is absent, then the datastore to which the
799 instance data belongs is unspecified.";
800 }
801 list revision {
802 key "date";
803 description
804 "Instance data sets that are produced as
805 a result of some sort of specification or design effort
806 SHOULD have at least one revision entry. For every
807 published editorial change, a new unique revision SHOULD
808 be added in front of the revisions sequence so that all
809 revisions are in reverse chronological order.
811 In case of instance data sets that are read from
812 or produced by a server or otherwise subject to
813 frequent updates or changes, revision
814 SHOULD NOT be present";
815 leaf date {
816 type string {
817 pattern '\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1])';
818 }
819 description
820 "Specifies the date the instance data set
821 was last modified. Formatted as YYYY-MM-DD";
822 }
823 leaf description {
824 type string;
825 description
826 "Description of this revision of the instance data set.";
827 }
828 }
829 leaf timestamp {
830 type yang:date-and-time;
831 description
832 "The date and time when the instance data set
833 was last modified.
835 In case of instance data sets that are read from or
836 produced by a server or otherwise subject to frequent
837 updates or changes, timestamp SHOULD be present.
839 If both a revision list entry and timestamp are present
840 the timestamp SHOULD contain the same date as the
841 latest revision statement.";
842 }
843 anydata content-data {
844 description
845 "Contains the real instance data.
846 The data MUST conform to the relevant YANG modules
847 specified either in the content-schema or in some other
848 implementation specific manner.";
849 }
850 }
851 }
852
854 4. Security Considerations
856 The YANG module defined in this document only defines a wrapper
857 structure specifying a format and a metadata header for YANG instance
858 data defined by the content-schema. Because of this the security
859 considerations template for YANG models in section 3.7.1 in [RFC8407]
860 is not followed. The instance data is designed to be accessed as a
861 stored file or over any file access method or protocol.
863 The document does not specify any method to influence the behavior of
864 a server.
866 Instance data files may contain sensitive data.
868 The header part is not security sensitive with one possible
869 exception. If the URI method is used for specification of the
870 content schema and the URI includes a username and/or a password, the
871 instance data file needs to be handled in a secure way as mentioned
872 below.
874 The security sensitivity of the instance data in the content part is
875 completely dependent on the content schema. Depending on the nature
876 of the instance data, instance data files MAY need to be handled
877 securely. The same kind of handling should be applied, that would be
878 needed for the result of a read operation returning the same data.
880 Instance data files should be protected against modification or
881 unauthorized access using normal file handling mechanisms. Care
882 should be taken, when copying the original files or providing file
883 access for additional users, not to reveal information
884 unintentionally.
886 5. IANA Considerations
888 This document registers one URI and one YANG module.
890 5.1. URI Registration
892 This document registers one URI in the IETF XML registry [RFC3688].
893 Following the format in RFC 3688, the following registration is
894 requested to be made:
896 URI: urn:ietf:params:xml:ns:yang:ietf-yang-instance-data
897 Registrant Contact: The IESG.
898 XML: N/A, the requested URI is an XML namespace.
900 5.2. YANG Module Name Registration
902 This document registers one YANG module in the YANG Module Names
903 registry [RFC6020]. Following the format in [RFC6020], the following
904 registrations are requested:
906 name: ietf-yang-instance-data
907 namespace: urn:ietf:params:xml:ns:yang:ietf-yang-instance-data
908 prefix: yid
909 reference: RFC XXXX
910 // RFC Ed.: replace XXXX with RFC number and remove this note
912 6. Acknowledgments
914 For their valuable comments, discussions, and feedback, we wish to
915 acknowledge Andy Bierman, Juergen Schoenwaelder, Rob Wilton, Joe
916 Clarke, Kent Watsen Martin Bjorklund, Ladislav Lhotka, Qin Wu and
917 other members of the Netmod WG.
919 7. References
921 7.1. Normative References
923 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
924 Requirement Levels", BCP 14, RFC 2119,
925 DOI 10.17487/RFC2119, March 1997,
926 .
928 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
929 the Network Configuration Protocol (NETCONF)", RFC 6020,
930 DOI 10.17487/RFC6020, October 2010,
931 .
933 [RFC6243] Bierman, A. and B. Lengyel, "With-defaults Capability for
934 NETCONF", RFC 6243, DOI 10.17487/RFC6243, June 2011,
935 .
937 [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
938 RFC 6991, DOI 10.17487/RFC6991, July 2013,
939 .
941 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
942 RFC 7950, DOI 10.17487/RFC7950, August 2016,
943 .
945 [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
946 RFC 7951, DOI 10.17487/RFC7951, August 2016,
947 .
949 [RFC7952] Lhotka, L., "Defining and Using Metadata with YANG",
950 RFC 7952, DOI 10.17487/RFC7952, August 2016,
951 .
953 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
954 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
955 May 2017, .
957 [RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
958 and R. Wilton, "Network Management Datastore Architecture
959 (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
960 .
962 [RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
963 and R. Wilton, "YANG Library", RFC 8525,
964 DOI 10.17487/RFC8525, March 2019,
965 .
967 [RFC8526] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
968 and R. Wilton, "NETCONF Extensions to Support the Network
969 Management Datastore Architecture", RFC 8526,
970 DOI 10.17487/RFC8526, March 2019,
971 .
973 [RFC8527] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
974 and R. Wilton, "RESTCONF Extensions to Support the Network
975 Management Datastore Architecture", RFC 8527,
976 DOI 10.17487/RFC8527, March 2019,
977 .
979 [RFC8791] Bierman, A., Björklund, M., and K. Watsen, "YANG Data
980 Structure Extensions", RFC 8791, DOI 10.17487/RFC8791,
981 June 2020, .
983 7.2. Informative References
985 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
986 DOI 10.17487/RFC3688, January 2004,
987 .
989 [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
990 BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
991 .
993 [RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of
994 Documents Containing YANG Data Models", BCP 216, RFC 8407,
995 DOI 10.17487/RFC8407, October 2018,
996 .
998 [RFC8632] Vallin, S. and M. Bjorklund, "A YANG Data Model for Alarm
999 Management", RFC 8632, DOI 10.17487/RFC8632, September
1000 2019, .
1002 [RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications
1003 for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
1004 September 2019, .
1006 [RFC8792] Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
1007 "Handling Long Lines in Content of Internet-Drafts and
1008 RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
1009 .
1011 [RFC8808] Wu, Q., Lengyel, B., and Y. Niu, "A YANG Data Model for
1012 Factory Default Settings", RFC 8808, DOI 10.17487/RFC8808,
1013 August 2020, .
1015 Appendix A. Changes between revisions
1017 RFC Ed.: Remove section "Changes between revisions"
1019 v18 - v19
1021 * Updated leaf includes-defaults
1023 v17 - v18
1025 * Added the report-all-tagged mode to the leaf includes-defaults
1027 v16 - v17
1029 * Removed default statement from includes-default
1031 v15 - v16
1033 * Editorial changes
1035 v14 - v15
1037 * Removed reference to revision-label
1039 * For the inline method made the usage of ietf-yang-
1040 library@2019-01-04 mandatory. Simplified the case "inline" in the
1041 YANG module.
1043 * Removed the "inline-module" leaf as it does not carry useful
1044 information anymore.
1046 * Removed YANG feature
1048 v13 - v14
1050 * Added leaf includes-defaults
1052 * Many small changes based on AD review
1054 v09 - v13
1056 * Editorial updates
1058 v08 - v09
1060 * Removed reference to similar to get reply
1062 * Introduced artwork folding in the examples
1063 v07 - v08
1065 * Moved compatibility into appendix
1067 * Renamed yid-version to format-version. Changed format to date of
1068 the YANG module
1070 * Made support of ietf-yang-library mandatory if inline-content-
1071 schema is supported
1073 * Many small changes based on WGLC
1075 v06 - v07
1077 * Updated terminology, use-cases
1079 * Many small changes based on WGLC
1081 v05 - v06
1083 * Modified module name format, removed .yin or .yang extension
1085 * Removed pattern for module and inline-module. The usage of
1086 revision-label should also be allowed.
1088 v04 - v05
1090 * Updated according to YANG-Doctor review
1092 * Updated security considerations
1094 * Added a wrapping container for the schema, and renamed the data
1095 nodes in the inline and uri cases.
1097 * Allowed .yin for simplified-inline schema naming. Made date
1098 optional if it is unavailable in the YANG module.
1100 * Added a mandatory yid-version to the header metadata to allow
1101 later updates of the module.
1103 v03 - v04
1105 * removed entity-tag and last-modified timestamp
1107 * Added simplified-inline method of content-schema specification
1109 v02 - v03
1110 * target renamed to "content-schema" and "content defining YANG
1111 module(s)"
1113 * Made name of instance data set optional
1115 * Updated according to draft-ietf-netmod-yang-data-ext-03
1117 * Clarified that entity-tag and last-modified timestamp are encoded
1118 as metadata. While they contain useful data, the HTTP-header
1119 based encoding from Restconf is not suitable.
1121 v01 - v02
1123 * Removed design time from terminology
1125 * Defined the format of the content-data part by referencing various
1126 RFCs and drafts instead of the result of the get-data and get
1127 operations.
1129 * Changed target-ptr to a choice
1131 * Inline target-ptr may include augmenting modules and alternatives
1132 to ietf-yang-library
1134 * Moved list of target modules into a separate
1135 element.
1137 * Added backwards compatibility considerations
1139 v00 - v01
1141 * Added the target-ptr metadata with 3 methods
1143 * Added timestamp metadata
1145 * Removed usage of dedicated .yid file extension
1147 * Added list of use cases
1149 * Added list of principles
1151 * Updated examples
1153 * Moved detailed use case descriptions to appendix
1155 Appendix B. Backwards Compatibility
1157 The concept of backwards compatibility and what changes are backwards
1158 compatible are not defined for "instance data sets" as it is highly
1159 dependent on the specific use case and the content-schema.
1161 In case of "instance data sets" that are the result of design or
1162 specification activity, some changes that may be good to avoid are
1163 listed below.
1165 YANG uses the concept of managed entities identified by key values;
1166 if the connection between the represented entity and the key value is
1167 not preserved during an update, this may lead to the following
1168 problems.
1170 * If the key value of a list entry that represents the same managed
1171 entity as before is changed, the user may mistakenly identify the
1172 list entry as new.
1174 * If the meaning of a list entry is changed, but the key values are
1175 not (e.g., redefining an alarm-type but not changing its alarm-
1176 type-id) the change may not be noticed.
1178 * If the key value of a previously removed list entry is reused for
1179 a different entity, the change may be misinterpreted as
1180 reintroducing the previous entity.
1182 Appendix C. Detailed Use Cases
1184 This section is non-normative.
1186 C.1. Use Case 1: Early Documentation of Server Capabilities
1188 A server has a number of server-capabilities that are defined in YANG
1189 modules and can be retrieved from the server using protocols like
1190 NETCONF or RESTCONF. Server capabilities include:
1192 * data defined in "ietf-yang-library": YANG modules, submodules,
1193 features, deviations, schema-mounts, and datastores supported
1194 ([RFC8525])
1196 * alarms supported ([RFC8632])
1198 * data nodes and subtrees that support or do not support on-change
1199 notifications ([RFC8641])
1201 * netconf-capabilities in ietf-netconf-monitoring.
1203 While it is good practice to allow a client to query these
1204 capabilities from the live server, that is often not possible.
1206 Often when a network node is released, an associated NMS (network
1207 management system) is also released with it. The NMS depends on the
1208 capabilities of the server. During NMS implementation, information
1209 about server capabilities is needed. If the information is
1210 unavailable early in some offline document, but only as instance data
1211 from the live network node, the NMS implementation will be delayed,
1212 because it has to wait until the network node is ready. Also
1213 assuming that all NMS implementors will have a correctly configured
1214 network nodes from which data can be retrieved, is a very expensive
1215 proposition. (An NMS may handle dozens of node types.)
1217 Network operators often build their own home-grown NMS systems that
1218 need to be integrated with a vendor's network node. The operator
1219 needs to know the network node's server capabilities in order to do
1220 this. Moreover, the network operator's decision to buy a vendor's
1221 product may even be influenced by the network node's OAM feature set
1222 documented as the server's capabilities.
1224 Beside NMS implementors, system integrators and many others also need
1225 the same information early. Examples could be model driven testing,
1226 generating documentation, etc.
1228 Most server-capabilities are relatively stable and change only during
1229 upgrade or due to licensing or the addition or removal of hardware.
1230 They are usually defined by a vendor at design time, before the
1231 product is released. It is feasible and advantageous to define/
1232 document them early e.g., in a YANG instance data File.
1234 It is anticipated that a separate IETF document will define in detail
1235 how and which set of server capabilities should be documented.
1237 C.2. Use Case 2: Preloading Data
1239 There are parts of the configuration that must be fully configurable
1240 by the operator. However, often a simple default configuration will
1241 be sufficient.
1243 One example is access control groups/roles and related rules. While
1244 a sophisticated operator may define dozens of different groups, often
1245 a basic (read-only operator, read-write system administrator,
1246 security-administrator) triplet will be enough. Vendors will often
1247 provide such default configuration data to make device configuration
1248 easier for an operator.
1250 Defining access control data is a complex task. To help, the device
1251 vendor predefines a set of default groups (/nacm:nacm/groups) and
1252 rules for these groups to access specific parts of common models
1253 (/nacm:nacm/rule-list/rule).
1255 YANG instance data files are used to document and/or preload the
1256 default configuration.
1258 C.3. Use Case 3: Documenting Factory Default Settings
1260 Nearly every server has a factory default configuration. If the
1261 system is really badly misconfigured or if the current configuration
1262 is to be abandoned, the system can be reset the default factory
1263 configuration.
1265 The operator currently needs to know what the default configuration
1266 actually contains. YANG instance data can be used to document the
1267 factory default configuration. See [RFC8808].
1269 Authors' Addresses
1271 Balazs Lengyel
1272 Ericsson
1274 Email: balazs.lengyel@ericsson.com
1276 Benoit Claise
1277 Huawei
1279 Email: benoit.claise@huawei.com