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2 Netmod B. Lengyel
3 Internet-Draft Ericsson
4 Intended status: Standards Track B. Claise
5 Expires: January 10, 2022 Huawei
6 July 9, 2021
8 YANG Instance Data File Format
9 draft-ietf-netmod-yang-instance-file-format-15
11 Abstract
13 There is a need to document data defined in YANG models at design,
14 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 January 10, 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
43 (https://trustee.ietf.org/license-info) in effect on the date of
44 publication of this document. Please review these documents
45 carefully, as they describe your rights and restrictions with respect
46 to this document. Code Components extracted from this document must
47 include Simplified BSD License text as described in Section 4.e of
48 the Trust Legal Provisions and are provided without warranty as
49 described in the Simplified BSD License.
51 Table of Contents
53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
54 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
55 1.2. Principles . . . . . . . . . . . . . . . . . . . . . . . 4
56 1.3. Delivery of Instance Data . . . . . . . . . . . . . . . . 4
57 1.4. Data Life cycle . . . . . . . . . . . . . . . . . . . . . 5
58 2. Instance Data File Format . . . . . . . . . . . . . . . . . . 5
59 2.1. Specifying the Content Schema . . . . . . . . . . . . . . 7
60 2.1.1. Inline Method . . . . . . . . . . . . . . . . . . . . 8
61 2.1.2. Simplified-Inline Method . . . . . . . . . . . . . . 8
62 2.1.3. URI Method . . . . . . . . . . . . . . . . . . . . . 8
63 2.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 8
64 2.2.1. Documentation of server capabilities . . . . . . . . 8
65 2.2.2. Preloading default configuration data . . . . . . . . 10
66 2.2.3. Storing diagnostics data . . . . . . . . . . . . . . 11
67 3. YANG Instance Data Model . . . . . . . . . . . . . . . . . . 12
68 3.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 12
69 3.2. YANG Model . . . . . . . . . . . . . . . . . . . . . . . 13
70 4. Security Considerations . . . . . . . . . . . . . . . . . . . 19
71 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
72 5.1. URI Registration . . . . . . . . . . . . . . . . . . . . 20
73 5.2. YANG Module Name Registration . . . . . . . . . . . . . . 20
74 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 21
75 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
76 7.1. Normative References . . . . . . . . . . . . . . . . . . 21
77 7.2. Informative References . . . . . . . . . . . . . . . . . 22
78 Appendix A. Changes between revisions . . . . . . . . . . . . . 23
79 Appendix B. Backwards Compatibility . . . . . . . . . . . . . . 25
80 Appendix C. Detailed Use Cases . . . . . . . . . . . . . . . . . 26
81 C.1. Use Case 1: Early Documentation of Server Capabilities . 26
82 C.2. Use Case 2: Preloading Data . . . . . . . . . . . . . . . 27
83 C.3. Use Case 3: Documenting Factory Default Settings . . . . 28
84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
86 1. Introduction
88 There is a need to document data defined in YANG models when a live
89 server is unavailable. Data is often needed at design,
90 implementation time or when a live running server is unavailable. To
91 facilitate this offline delivery of data, this document specifies a
92 standard format for YANG instance data sets and YANG instance data
93 files. The format of the instance data set is defined by the "ietf-
94 yang-instance-data" YANG module, see Section 3. The YANG data model
95 in this document conforms to the Network Management Datastore
96 Architecture (NMDA) defined in [RFC8342]
98 The following is a list of already implemented and potential use
99 cases.
101 UC1 Documentation of server capabilities
103 UC2 Preloading default configuration data
105 UC3 Documenting Factory Default Settings
107 UC4 Storing the configuration of a device, e.g., for backup, archive
108 or audit purposes
110 UC5 Storing diagnostics data
112 UC6 Allowing YANG instance data to potentially be carried within
113 other IPC message formats
115 UC7 Default instance data used as part of a templating solution
117 UC8 Providing data examples in RFCs or internet drafts
119 In Appendix C describes the first three use cases in detail.
121 There are many and varied use cases where YANG instance data could be
122 used. This document does not limit future uses of instance data
123 sets, so specifying how and when to use YANG instance data is out of
124 scope for this document. It is anticipated that other documents will
125 define specific use cases. Use cases are listed only as examples.
127 1.1. Terminology
129 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
130 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
131 "OPTIONAL" in this document are to be interpreted as described in BCP
132 14 [RFC2119] [RFC8174] when, and only when, they appear in all
133 capitals, as shown here.
135 Instance Data: A collection of instantiated data nodes.
137 Instance Data Set: A named set of data items annotated with metadata
138 that can be used as instance data in a YANG data tree.
140 Instance Data File: A file containing an instance data set formatted
141 according to the rules described in this document.
143 Content-schema: A set of YANG modules with their revision, supported
144 features, and deviations for which the instance data set contains
145 instance data.
147 Content defining YANG module: an individual YANG module that is part
148 of the content-schema.
150 The term "server" is used as defined in [RFC8342].
152 1.2. Principles
154 The following is a list of the basic principles of the instance data
155 format:
157 P1 Two standard formats shall be defined based on the XML and JSON
158 encodings.
160 P2 Instance data shall reuse existing encoding rules for YANG
161 defined data.
163 P3 Metadata about the instance data set (Section 2, Paragraph 9)
164 shall be defined.
166 P4 A YANG instance data set shall be allowed to contain data for
167 multiple YANG modules.
169 P5 Instance data shall be allowed to contain configuration data,
170 state data, or a mix of the two.
172 P6 Partial data sets shall be allowed.
174 P7 The YANG instance data format shall be usable for any data for
175 which YANG module(s) are defined and available to the reader,
176 independent of whether the module is implemented by a server.
178 P8 It shall be possible to report the identity of the datastore with
179 which the instance data set is associated.
181 1.3. Delivery of Instance Data
183 Instance data sets that are produced as a result of some sort of
184 specification or design effort may be available without the need for
185 a live server e.g., via download from the vendor's website, or in any
186 other way that product documentation is distributed.
188 Other instance data sets may be read from or produced by the YANG
189 server itself e.g., UC5 documenting diagnostic data.
191 1.4. Data Life cycle
193 A YANG instance data set is created at a specific point of time. If
194 the data changes afterwards, this is not represented in the instance
195 data set anymore. The current values may be retrieved at run-time
196 via NETCONF/RESTCONF or received e.g., in YANG-Push notifications.
198 Whether the instance data changes and if so, when and how, should be
199 described either in the instance data set's description statement or
200 in some other implementation specific manner.
202 2. Instance Data File Format
204 A YANG instance data file MUST contain a single instance data set and
205 no additional data.
207 The format of the instance data set is defined by the "ietf-yang-
208 instance-data" YANG module. It is made up of a header part and
209 content-data. The header part carries metadata for the instance data
210 set. The content-data, defined as an anydata data node, carries the
211 instance data that the user wants to document/provide. The syntax
212 and semantics of content-data is defined by the content-schema.
214 Two formats are specified based on the XML and JSON YANG encodings.
215 Later, as other YANG encodings (e.g., CBOR) are defined, further
216 instance data formats may be specified.
218 The content-data part MUST conform to the content-schema, while
219 allowing for the exceptions listed below. The content-data part
220 SHALL follow the encoding rules defined in [RFC7950] for XML and
221 [RFC7951] for JSON and MUST use UTF-8 character encoding. Content-
222 data MAY include:
224 o metadata, as defined by [RFC7952].
226 o origin metadata, as specified in [RFC8526] and [RFC8527]
228 o implementation specific metadata relevant to individual data
229 nodes. Unknown metadata MUST be ignored by users of instance
230 data, allowing it to be used later for other purposes.
232 An instance data set MAY contain data for any number of YANG modules;
233 if needed it MAY carry the complete configuration and state data for
234 a server. Default values should be excluded where they do not
235 provide additional useful data.
237 Configuration ("config true") and operational state data ("config
238 false") MAY be mixed in the instance data file.
240 Instance data files MAY contain partial data sets. This means
241 "mandatory", "min-elements", "require-instance true", "must" and
242 "when" constrains MAY be violated.
244 The name of the instance data file SHOULD be of the form:
246 instance-data-set-name ['@' ( revision-date / timestamp ) ]
247 ( '.xml' / '.json' )
249 E.g., acme-router-modules.xml
250 E.g., acme-router-modules@2018-01-25.xml
251 E.g., acme-router-modules@2018-01-25T15_06_34_3+01_00.json
253 If the leaf "name" is present in the instance data header, its value
254 SHOULD be used for the "instance-data-set-name". If the "revision-
255 date" is present in the filename it MUST conform to the format of the
256 revision-date leaf in the YANG model. If the "revision-date" is
257 present in both the filename and in the instance data header, the
258 revision date in the file name MUST be set to the latest revision
259 date inside the instance data set. If the "timestamp" is present in
260 the filename it MUST conform to the format of the timestamp leaf in
261 the YANG model except for replacing colons as described below. If
262 the "timestamp" is present both in the filename and in the instance
263 data header, the timestamp in the file name SHOULD be set to the
264 timestamp inside the instance data set; any colons, if present, shall
265 be replaced by underscores.
267 Metadata, information about the data set itself SHOULD be included in
268 the instance data set. Some metadata items are defined in the YANG
269 module "ietf-yang-instance-data", but other items MAY be used.
271 Metadata MUST include:
273 * Version of the YANG Instance Data format
275 Metadata SHOULD include:
277 * Name of the data set
279 * Content schema specification (i.e., the "content-schema" node)
280 * Description of the instance data set. The description SHOULD
281 contain information whether and how the data can change during
282 the lifetime of the server
284 * An indication whether default values are included. The default
285 handling uses the concepts defined in [RFC6243], however as
286 only concepts are re-used, users of instance data sets, do not
287 need to support RFC 6243.
289 2.1. Specifying the Content Schema
291 To properly understand and use an instance data set, the user needs
292 to know the content-schema. One of the following methods SHOULD be
293 used:
295 Simplified-Inline method: Include the needed information as part
296 of the instance data set; short specification.
298 Inline method: Include the needed information as part of the
299 instance data set.
301 URI method: Include a URI that references another YANG instance
302 data file. This instance data file will use the same content-
303 schema as the referenced YANG instance data file. (if you don't
304 want to repeat the info again and again)
306 External Method: Do not include the "content-schema" node; the
307 user needs to obtain the information through external documents.
309 Additional methods e.g., a YANG-package based solution may be added
310 later.
312 Note, the specified content-schema only indicates the set of modules
313 that were used to define this YANG instance data set. Sometimes
314 instance data may be used for a server supporting a different YANG
315 module set (e.g., for the "Preloading default configuration data"
316 use-case, UC2 in Section 1, the instance data set may not be updated
317 every time the YANG modules on the server are updated). Whether an
318 instance data set originally defined using a specific content-schema
319 is usable with a different other schema depends on many factors
320 including the amount of differences and the compatibility between the
321 original and the other schema, considering modules, revisions,
322 features, deviations, the scope of the instance data, etc.
324 2.1.1. Inline Method
326 The inline-yang-library anydata data node carries instance data
327 (conforming to ietf-yang-library@2019-01-04) that specifies the
328 content defining YANG modules including revision, supported features,
329 deviations and any relevant additional data. An example of the
330 "inline" method is provided in Figure 2.
332 2.1.2. Simplified-Inline Method
334 The instance data set contains a list of content defining YANG
335 modules including the revision date for each. Usage of this method
336 implies that the modules are used without any deviations and with all
337 features supported. YANG modules that are only required to satisfy
338 import-only dependencies MAY be excluded from the leaf-list. If they
339 are excluded then the consumer of the instance data set can choose
340 any versions of the YANG modules that satisfy the import dependency.
341 An example of the "simplified-inline" method is provided in Figure 3.
343 2.1.3. URI Method
345 The "same-schema-as-file" leaf SHALL contain a URI that references
346 another YANG instance data file. The current instance data file will
347 use the same content schema as the referenced file. Referenced files
348 using the "inline" or the "simplified-inline" methods MUST be
349 supported. Referenced files using the "URI Method" MAY be supported.
351 The referenced instance data file MAY have no content-data if it is
352 used solely for specifying the content-schema.
354 If a referenced instance data file is unavailable, content-schema is
355 unknown.
357 The URI method is advantageous when the user wants to avoid the
358 overhead of specifying the content-schema in each instance data file:
359 E.g., In UC6, when the system creates a diagnostic file every minute
360 to document the state of the server.
362 An example of the "URI" method is provided in Figure 4.
364 2.2. Examples
366 2.2.1. Documentation of server capabilities
368 The example file acme-router-modules@2021-07-07.xml reflects UC1 in
369 Section 1. It provides a list of supported YANG modules and NETCONF
370 capabilities for a server. It uses the "inline" method to specify
371 the content-schema.
373 The example uses artwork folding [RFC8792].
375 ========== NOTE: '\' line wrapping per RFC 8792 ===========
377
378
380 acme-router-modules
381
382
383
385
386 ietf-yang-library
387 2019-01-04
388
389
390 ietf-netconf-monitoring
391 2010-10-04
392
393
394
395
396
397 1956-10-23
398 Initial version
399
400 Defines the minimal set of modules that any \
401 acme-router will contain.
402 info@acme.com
403
404
406
407 ietf-yang-library
408 2019-01-04
409 \
410 urn:ietf:params:xml:ns:yang:ietf-yang-library\
411
412 implement
413
414
415 ietf-system
416 2014-08-06
417 urn:ietf:params:xml:ns:yang:ietf-system
418 sys:authentication
419 sys:local-users
420
421 acme-system-ext
422 2018-08-06
423
424 implement
425
426
427 ietf-netconf-monitoring
428 2010-10-04
429 \
430 urn:ietf:params:xml:ns:yang:ietf-netconf-monitoring\
431
432 implement
433
434
435 ietf-yang-types
436 2013-07-15
437 urn:ietf:params:xml:ns:yang:ietf-yang-types\
438
439 import
440
441
442 acme-system-ext
443 2018-08-06
444 urn:rdns:acme.com:oammodel:acme-system-ext\
445
446 implement
447
448
449
451
452 \
453 urn:ietf:params:netconf:capability:validate:1.1\
454
455
456
457
458
460 Figure 2
462 2.2.2. Preloading default configuration data
464 The example file read-only-acm-rules@2021-07-07.xml reflects UC2 in
465 Section 1. It provides a default rule set for a read-only operator
466 role. It uses the "simplified-inline" method for specifying the
467 content-schema.
469
470
472 read-only-acm-rules
473
474 ietf-netconf-acm@2018-02-14
475
476
477 1776-07-04
478 Initial version
479
480 Access control rules for a read-only role.
481
482
483 true
484 deny
485 deny
486
487 read-only-role
488 read-only-group
489
490 read-all
491 *
492 read
493 permit
494
495
496
497
498
500 Figure 3
502 2.2.3. Storing diagnostics data
504 The example file acme-router-netconf-
505 diagnostics@2018-01-25T17_00_38Z.json reflects UC5 in Section 1. An
506 instance data set is produced by the server every 15 minutes that
507 contains statistics about the NETCONF server. As a new set is
508 produced periodically many times a day a revision-date would be
509 useless; instead a timestamp is included.
511 {
512 "ietf-yang-instance-data:instance-data-set": {
513 "name": "acme-router-netconf-diagnostics",
514 "content-schema": {
515 "same-schema-as-file": "file:///acme-diagnostics-schema.json"
516 },
517 "timestamp": "2018-01-25T17:00:38Z",
518 "description": ["NETCONF statistics"],
519 "content-data": {
520 "ietf-netconf-monitoring:netconf-state": {
521 "statistics": {
522 "netconf-start-time ": "2018-12-05T17:45:00Z",
523 "in-bad-hellos ": "32",
524 "in-sessions ": "397",
525 "dropped-sessions ": "87",
526 "in-rpcs ": "8711",
527 "in-bad-rpcs ": "408",
528 "out-rpc-errors ": "408",
529 "out-notifications": "39007"
530 }
531 }
532 }
533 }
534 }
536 Figure 4
538 3. YANG Instance Data Model
540 3.1. Tree Diagram
542 The following tree diagram [RFC8340] provides an overview of the data
543 model.
545 module: ietf-yang-instance-data
547 structure instance-data-set:
548 +-- name? string
549 +-- format-version? string
550 +-- includes-defaults? enumeration
551 +-- content-schema
552 | +-- (content-schema-spec)?
553 | +--:(simplified-inline)
554 | | +-- module* module-with-revision-date
555 | +--:(inline)
556 | | +-- inline-yang-library
557 | +--:(uri)
558 | +-- same-schema-as-file? inet:uri
559 +-- description* string
560 +-- contact? string
561 +-- organization? string
562 +-- datastore? ds:datastore-ref
563 +-- revision* [date]
564 | +-- date string
565 | +-- description? string
566 +-- timestamp? yang:date-and-time
567 +-- content-data?
569 3.2. YANG Model
571 This YANG module imports typedefs from [RFC6991], identities from
572 [RFC8342] and the "structure" extension from [RFC8791]. It also
573 references [RFC8525] and [RFC6243].
575 file "ietf-yang-instance-data@2021-07-07.yang"
576 // RFC Ed.: replace the date above if the module gets changed in
577 //anyway during reviews or RFC editor process and remove this note
578 module ietf-yang-instance-data {
579 yang-version 1.1;
580 namespace "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data";
581 prefix yid;
583 import ietf-yang-structure-ext {
584 prefix sx;
585 reference
586 "YANG Data Structure Extensions:
587 draft-ietf-netmod-yang-data-ext-05";
588 }
589 import ietf-datastores {
590 prefix ds;
591 reference
592 "RFC 8342: Network Management Datastore Architecture (NMDA)";
594 }
595 import ietf-inet-types {
596 prefix inet;
597 reference
598 "RFC 6991: Common YANG Data Types";
599 }
600 import ietf-yang-types {
601 prefix yang;
602 reference
603 "RFC 6991: Common YANG Data Types";
604 }
606 organization
607 "IETF NETMOD Working Group";
608 contact
609 "WG Web:
610 WG List:
612 Author: Balazs Lengyel
613
615 Author: Benoit Claise
616 ";
617 description
618 "The module defines the structure and content of YANG
619 instance data sets.
621 The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
622 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
623 'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
624 are to be interpreted as described in BCP 14 (RFC 2119)
625 (RFC 8174) when, and only when, they appear in all
626 capitals, as shown here.
628 Copyright (c) 2021 IETF Trust and the persons identified as
629 authors of the code. All rights reserved.
631 Redistribution and use in source and binary forms, with or
632 without modification, is permitted pursuant to, and subject
633 to the license terms contained in, the Simplified BSD License
634 set forth in Section 4.c of the IETF Trust's Legal Provisions
635 Relating to IETF Documents
636 (http://trustee.ietf.org/license-info).
638 This version of this YANG module is part of RFC XXXX; see
639 the RFC itself for full legal notices.";
640 // RFC Ed.: replace XXXX with RFC number and remove this note
642 revision 2021-07-07 {
643 // RFC Ed.: replace the date above if the module gets changed in
644 // anyway during reviews or RFC editor process and remove this note
645 description
646 "Initial revision.";
647 reference
648 "RFC XXXX: YANG Instance Data Format";
649 // RFC Ed.: replace XXXX with RFC number and remove this note
650 }
652 typedef module-with-revision-date {
653 type string {
654 pattern '[a-zA-Z_][a-zA-Z0-9\-_.]*' +
655 '(@\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1]))?';
656 pattern '.|..|[^xX].*|.[^mM].*|..[^lL].*';
657 }
658 description
659 "A type defining a module name and an optional revision
660 date, e.g. ietf-yang-library@2019-01-04";
661 }
663 sx:structure "instance-data-set" {
664 description
665 "A data structure to define a format for YANG instance
666 data. The majority of the YANG nodes provide meta-data
667 about the instance data; the instance data itself is
668 is contained only in the 'content-data' node.";
669 leaf name {
670 type string;
671 description
672 "An arbitrary name for the YANG instance data set. This
673 value is primarily used for descriptive purposes. However,
674 when the instance data set is saved to a file, then the
675 filename MUST encode the name's value, per Section 3
676 of RFC XXXX.";
677 // RFC Ed.: replace XXXX with RFC number and remove this note
678 }
679 leaf format-version {
680 type string {
681 pattern '\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1])';
682 }
683 default "2021-07-07";
684 // RFC Ed.: replace the date above if the module gets changed in
685 // anyway during reviews or RFC editor process and remove this
686 // note
687 description
688 "The 'revision' of the 'ietf-yang-instance-data' module
689 used to encode this 'instance-data-set'.";
691 }
692 leaf includes-defaults {
693 type enumeration {
694 enum report-all {
695 value 1;
696 description
697 "All data nodes SHOULD be included independent of
698 any default values.";
699 }
700 enum trim {
701 value 2;
702 description
703 "Data nodes that have a default defined and where
704 the actual value is the default value SHOULD
705 NOT be included.";
706 }
707 enum explicit {
708 value 3;
709 description
710 "Data nodes that have a default defined and where
711 the actual value is the default value SHOULD NOT be
712 included. However, if the actual value was set by
713 a NETCONF client or other management application
714 by the way of an explicit management operation the
715 data node SHOULD be included.";
716 }
717 }
718 default trim;
719 description
720 "As instance-data-sets MAY contain incomplete data sets,
721 thus any data node MAY be absent.
723 Providing the instance-data-set intends to contain a
724 full data set, this leaf specifies whether the data set
725 includes data nodes that have a default defined and
726 where the actual value is the same as the default value.
728 Data nodes that have no default values should always
729 be included.
730 Data nodes that have a default value, but the actual
731 value is not equal to the schema defined default
732 should always be included.";
733 reference
734 "RFC 6243: With-defaults Capability for NETCONF";
735 }
736 container content-schema {
737 description
738 "The content schema (i.e., YANG modules) used to create
739 the instance data set.
740 If not present the user needs to obtain the information
741 through external documents.";
742 choice content-schema-spec {
743 description
744 "Specification of the content-schema.";
745 case simplified-inline {
746 leaf-list module {
747 type module-with-revision-date;
748 min-elements 1;
749 description
750 "The list of content defining YANG modules.
752 The value SHALL start with the module name.
753 If the module contains a revision statement the
754 revision date SHALL be included in the leaf-list
755 entry.
757 E.g., ietf-yang-library@2019-01-04
759 Usage of this leaf-list implies the modules are
760 used without any deviations and with all features
761 supported. Multiple revisions of the same module
762 MUST NOT be specified.";
763 }
764 }
765 case inline {
766 anydata inline-yang-library {
767 mandatory true;
768 description
769 "Instance data corresponding to the
770 ietf-yang-library@2019-01-04 defining
771 the set of content defining YANG modules for
772 this instance-data-set.";
773 }
774 }
775 case uri {
776 leaf same-schema-as-file {
777 type inet:uri;
778 description
779 "A reference to another YANG instance data file.
780 This instance data file uses the same
781 content schema as the referenced file.
782 The URL schemes 'file://' and 'https://' MUST
783 be supported, other schemes MAY also be
784 supported.";
785 }
786 }
788 }
789 }
790 leaf-list description {
791 type string;
792 description
793 "Description of the instance data set.";
794 }
795 leaf contact {
796 type string;
797 description
798 "Contact information for the person or
799 organization to whom queries concerning this
800 instance data set should be sent.";
801 }
802 leaf organization {
803 type string;
804 description
805 "Organization responsible for the instance
806 data set.";
807 }
808 leaf datastore {
809 type ds:datastore-ref;
810 description
811 "The identity of the datastore with which the
812 instance data set is associated, e.g., the datastore from
813 where the data was read or the datastore into which the data
814 may be loaded or the datastore which is being documented.
815 If a single specific datastore cannot be specified, the
816 leaf MUST be absent.
818 If this leaf is absent, then the datastore to which the
819 instance data belongs is unspecified.";
820 }
821 list revision {
822 key "date";
823 description
824 "Instance data sets that are produced as
825 a result of some sort of specification or design effort
826 SHOULD have at least one revision entry. For every
827 published editorial change, a new unique revision SHOULD
828 be added in front of the revisions sequence so that all
829 revisions are in reverse chronological order.
831 In case of instance data sets that are read from
832 or produced by a server or otherwise subject to
833 frequent updates or changes, revision
834 SHOULD NOT be present";
835 leaf date {
836 type string {
837 pattern '\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1])';
838 }
839 description
840 "Specifies the date the instance data set
841 was last modified. Formatted as YYYY-MM-DD";
842 }
843 leaf description {
844 type string;
845 description
846 "Description of this revision of the instance data set.";
847 }
848 }
849 leaf timestamp {
850 type yang:date-and-time;
851 description
852 "The date and time when the instance data set
853 was last modified.
855 In case of instance data sets that are read from or
856 produced by a server or otherwise subject to frequent
857 updates or changes, timestamp SHOULD be present.
859 If both a revision list entry and timestamp are present
860 the timestamp SHOULD contain the same date as the
861 latest revision statement.";
862 }
863 anydata content-data {
864 description
865 "Contains the real instance data.
866 The data MUST conform to the relevant YANG modules
867 specified either in the content-schema or in some other
868 implementation specific manner.";
869 }
870 }
871 }
872
874 4. Security Considerations
876 The YANG module defined in this document only defines a wrapper
877 structure specifying a format and a metadata header for YANG instance
878 data defined by the content-schema. Because of this the security
879 considerations template for YANG models in section 3.7.1 in [RFC8407]
880 is not followed. The instance data is designed to be accessed as a
881 stored file or over any file access method or protocol.
883 The document does not specify any method to influence the behavior of
884 a server.
886 Instance data files may contain sensitive data.
888 The header part is not security sensitive with one possible
889 exception. If the URI method is used for specification of the
890 content schema and the URI includes a username and/or a password, the
891 instance data file needs to be handled in a secure way as mentioned
892 below.
894 The security sensitivity of the instance data in the content part is
895 completely dependent on the content schema. Depending on the nature
896 of the instance data, instance data files MAY need to be handled
897 securely. The same kind of handling should be applied, that would be
898 needed for the result of a read operation returning the same data.
900 Instance data files should be protected against modification or
901 unauthorized access using normal file handling mechanisms. Care
902 should be taken, when copying the original files or providing file
903 access for additional users, not to reveal information
904 unintentionally.
906 5. IANA Considerations
908 This document registers one URI and one YANG module.
910 5.1. URI Registration
912 This document registers one URI in the IETF XML registry [RFC3688].
913 Following the format in RFC 3688, the following registration is
914 requested to be made:
916 URI: urn:ietf:params:xml:ns:yang:ietf-yang-instance-data
917 Registrant Contact: The IESG.
918 XML: N/A, the requested URI is an XML namespace.
920 5.2. YANG Module Name Registration
922 This document registers one YANG module in the YANG Module Names
923 registry [RFC6020]. Following the format in [RFC6020], the following
924 registrations are requested:
926 name: ietf-yang-instance-data
927 namespace: urn:ietf:params:xml:ns:yang:ietf-yang-instance-data
928 prefix: yid
929 reference: RFC XXXX
930 // RFC Ed.: replace XXXX with RFC number and remove this note
932 6. Acknowledgments
934 For their valuable comments, discussions, and feedback, we wish to
935 acknowledge Andy Bierman, Juergen Schoenwaelder, Rob Wilton, Joe
936 Clarke, Kent Watsen Martin Bjorklund, Ladislav Lhotka, Qin Wu and
937 other members of the Netmod WG.
939 7. References
941 7.1. Normative References
943 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
944 Requirement Levels", BCP 14, RFC 2119,
945 DOI 10.17487/RFC2119, March 1997,
946 .
948 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
949 the Network Configuration Protocol (NETCONF)", RFC 6020,
950 DOI 10.17487/RFC6020, October 2010,
951 .
953 [RFC6243] Bierman, A. and B. Lengyel, "With-defaults Capability for
954 NETCONF", RFC 6243, DOI 10.17487/RFC6243, June 2011,
955 .
957 [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
958 RFC 6991, DOI 10.17487/RFC6991, July 2013,
959 .
961 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
962 RFC 7950, DOI 10.17487/RFC7950, August 2016,
963 .
965 [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
966 RFC 7951, DOI 10.17487/RFC7951, August 2016,
967 .
969 [RFC7952] Lhotka, L., "Defining and Using Metadata with YANG",
970 RFC 7952, DOI 10.17487/RFC7952, August 2016,
971 .
973 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
974 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
975 May 2017, .
977 [RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
978 and R. Wilton, "Network Management Datastore Architecture
979 (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
980 .
982 [RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
983 and R. Wilton, "YANG Library", RFC 8525,
984 DOI 10.17487/RFC8525, March 2019,
985 .
987 [RFC8526] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
988 and R. Wilton, "NETCONF Extensions to Support the Network
989 Management Datastore Architecture", RFC 8526,
990 DOI 10.17487/RFC8526, March 2019,
991 .
993 [RFC8527] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
994 and R. Wilton, "RESTCONF Extensions to Support the Network
995 Management Datastore Architecture", RFC 8527,
996 DOI 10.17487/RFC8527, March 2019,
997 .
999 [RFC8791] Bierman, A., Bjoerklund, M., and K. Watsen, "YANG Data
1000 Structure Extensions", RFC 8791, DOI 10.17487/RFC8791,
1001 June 2020, .
1003 7.2. Informative References
1005 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
1006 DOI 10.17487/RFC3688, January 2004,
1007 .
1009 [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
1010 BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
1011 .
1013 [RFC8407] Bierman, A., "Guidelines for Authors and Reviewers of
1014 Documents Containing YANG Data Models", BCP 216, RFC 8407,
1015 DOI 10.17487/RFC8407, October 2018,
1016 .
1018 [RFC8632] Vallin, S. and M. Bjorklund, "A YANG Data Model for Alarm
1019 Management", RFC 8632, DOI 10.17487/RFC8632, September
1020 2019, .
1022 [RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications
1023 for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
1024 September 2019, .
1026 [RFC8792] Watsen, K., Auerswald, E., Farrel, A., and Q. Wu,
1027 "Handling Long Lines in Content of Internet-Drafts and
1028 RFCs", RFC 8792, DOI 10.17487/RFC8792, June 2020,
1029 .
1031 [RFC8808] Wu, Q., Lengyel, B., and Y. Niu, "A YANG Data Model for
1032 Factory Default Settings", RFC 8808, DOI 10.17487/RFC8808,
1033 August 2020, .
1035 Appendix A. Changes between revisions
1037 RFC Ed.: Remove section "Changes between revisions"
1039 v14 - v15
1041 o Removed reference to revision-label
1043 o For the inline method made the usage of ietf-yang-
1044 library@2019-01-04 mandatory. Simplified the case "inline" in the
1045 YANG module.
1047 o Removed the "inline-module" leaf as it does not carry useful
1048 information anymore.
1050 o Removed YANG feature
1052 v13 - v14
1054 o Added leaf includes-defaults
1056 o Many small changes based on AD review
1058 v09 - v13
1060 o Editorial updates
1062 v08 - v09
1064 o Removed reference to similar to get reply
1066 o Introduced artwork folding in the examples
1068 v07 - v08
1070 o Moved compatibility into appendix
1072 o Renamed yid-version to format-version. Changed format to date of
1073 the YANG module
1075 o Made support of ietf-yang-library mandatory if inline-content-
1076 schema is supported
1078 o Many small changes based on WGLC
1080 v06 - v07
1082 o Updated terminology, use-cases
1084 o Many small changes based on WGLC
1086 v05 - v06
1088 o Modified module name format, removed .yin or .yang extension
1090 o Removed pattern for module and inline-module. The usage of
1091 revision-label should also be allowed.
1093 v04 - v05
1095 o Updated according to YANG-Doctor review
1097 o Updated security considerations
1099 o Added a wrapping container for the schema, and renamed the data
1100 nodes in the inline and uri cases.
1102 o Allowed .yin for simplified-inline schema naming. Made date
1103 optional if it is unavailable in the YANG module.
1105 o Added a mandatory yid-version to the header metadata to allow
1106 later updates of the module.
1108 v03 - v04
1110 o removed entity-tag and last-modified timestamp
1112 o Added simplified-inline method of content-schema specification
1114 v02 - v03
1116 o target renamed to "content-schema" and "content defining YANG
1117 module(s)"
1119 o Made name of instance data set optional
1121 o Updated according to draft-ietf-netmod-yang-data-ext-03
1122 o Clarified that entity-tag and last-modified timestamp are encoded
1123 as metadata. While they contain useful data, the HTTP-header
1124 based encoding from Restconf is not suitable.
1126 v01 - v02
1128 o Removed design time from terminology
1130 o Defined the format of the content-data part by referencing various
1131 RFCs and drafts instead of the result of the get-data and get
1132 operations.
1134 o Changed target-ptr to a choice
1136 o Inline target-ptr may include augmenting modules and alternatives
1137 to ietf-yang-library
1139 o Moved list of target modules into a separate
1140 element.
1142 o Added backwards compatibility considerations
1144 v00 - v01
1146 o Added the target-ptr metadata with 3 methods
1148 o Added timestamp metadata
1150 o Removed usage of dedicated .yid file extension
1152 o Added list of use cases
1154 o Added list of principles
1156 o Updated examples
1158 o Moved detailed use case descriptions to appendix
1160 Appendix B. Backwards Compatibility
1162 The concept of backwards compatibility and what changes are backwards
1163 compatible are not defined for "instance data sets" as it is highly
1164 dependent on the specific use case and the content-schema.
1166 In case of "instance data sets" that are the result of design or
1167 specification activity, some changes that may be good to avoid are
1168 listed below.
1170 YANG uses the concept of managed entities identified by key values;
1171 if the connection between the represented entity and the key value is
1172 not preserved during an update, this may lead to the following
1173 problems.
1175 o If the key value of a list entry that represents the same managed
1176 entity as before is changed, the user may mistakenly identify the
1177 list entry as new.
1179 o If the meaning of a list entry is changed, but the key values are
1180 not (e.g., redefining an alarm-type but not changing its alarm-
1181 type-id) the change may not be noticed.
1183 o If the key value of a previously removed list entry is reused for
1184 a different entity, the change may be misinterpreted as
1185 reintroducing the previous entity.
1187 Appendix C. Detailed Use Cases
1189 This section is non-normative.
1191 C.1. Use Case 1: Early Documentation of Server Capabilities
1193 A server has a number of server-capabilities that are defined in YANG
1194 modules and can be retrieved from the server using protocols like
1195 NETCONF or RESTCONF. Server capabilities include:
1197 o data defined in "ietf-yang-library": YANG modules, submodules,
1198 features, deviations, schema-mounts, and datastores supported
1199 ([RFC8525])
1201 o alarms supported ([RFC8632])
1203 o data nodes and subtrees that support or do not support on-change
1204 notifications ([RFC8641])
1206 o netconf-capabilities in ietf-netconf-monitoring.
1208 While it is good practice to allow a client to query these
1209 capabilities from the live server, that is often not possible.
1211 Often when a network node is released, an associated NMS (network
1212 management system) is also released with it. The NMS depends on the
1213 capabilities of the server. During NMS implementation, information
1214 about server capabilities is needed. If the information is
1215 unavailable early in some offline document, but only as instance data
1216 from the live network node, the NMS implementation will be delayed,
1217 because it has to wait until the network node is ready. Also
1218 assuming that all NMS implementors will have a correctly configured
1219 network nodes from which data can be retrieved, is a very expensive
1220 proposition. (An NMS may handle dozens of node types.)
1222 Network operators often build their own home-grown NMS systems that
1223 need to be integrated with a vendor's network node. The operator
1224 needs to know the network node's server capabilities in order to do
1225 this. Moreover, the network operator's decision to buy a vendor's
1226 product may even be influenced by the network node's OAM feature set
1227 documented as the server's capabilities.
1229 Beside NMS implementors, system integrators and many others also need
1230 the same information early. Examples could be model driven testing,
1231 generating documentation, etc.
1233 Most server-capabilities are relatively stable and change only during
1234 upgrade or due to licensing or the addition or removal of hardware.
1235 They are usually defined by a vendor at design time, before the
1236 product is released. It is feasible and advantageous to define/
1237 document them early e.g., in a YANG instance data File.
1239 It is anticipated that a separate IETF document will define in detail
1240 how and which set of server capabilities should be documented.
1242 C.2. Use Case 2: Preloading Data
1244 There are parts of the configuration that must be fully configurable
1245 by the operator. However, often a simple default configuration will
1246 be sufficient.
1248 One example is access control groups/roles and related rules. While
1249 a sophisticated operator may define dozens of different groups, often
1250 a basic (read-only operator, read-write system administrator,
1251 security-administrator) triplet will be enough. Vendors will often
1252 provide such default configuration data to make device configuration
1253 easier for an operator.
1255 Defining access control data is a complex task. To help, the device
1256 vendor predefines a set of default groups (/nacm:nacm/groups) and
1257 rules for these groups to access specific parts of common models
1258 (/nacm:nacm/rule-list/rule).
1260 YANG instance data files are used to document and/or preload the
1261 default configuration.
1263 C.3. Use Case 3: Documenting Factory Default Settings
1265 Nearly every server has a factory default configuration. If the
1266 system is really badly misconfigured or if the current configuration
1267 is to be abandoned, the system can be reset the default factory
1268 configuration.
1270 The operator currently needs to know what the default configuration
1271 actually contains. YANG instance data can be used to document the
1272 factory default configuration. See [RFC8808].
1274 Authors' Addresses
1276 Balazs Lengyel
1277 Ericsson
1279 Email: balazs.lengyel@ericsson.com
1281 Benoit Claise
1282 Huawei
1284 Email: benoit.claise@huawei.com