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2 Netmod B. Lengyel
3 Internet-Draft Ericsson
4 Intended status: Standards Track B. Claise
5 Expires: October 10, 2020 Cisco Systems, Inc.
6 April 8, 2020
8 YANG Instance Data File Format
9 draft-ietf-netmod-yang-instance-file-format-11
11 Abstract
13 There is a need to document data defined in YANG models when a live
14 server is unavailable. Data is often needed at design or
15 implementation time or needed when a live running server is
16 unavailable. This document specifies a standard file format for YANG
17 instance data, which follows the syntax and semantics of existing
18 YANG models, and annotates it with metadata.
20 Status of This Memo
22 This Internet-Draft is submitted in full conformance with the
23 provisions of BCP 78 and BCP 79.
25 Internet-Drafts are working documents of the Internet Engineering
26 Task Force (IETF). Note that other groups may also distribute
27 working documents as Internet-Drafts. The list of current Internet-
28 Drafts is at https://datatracker.ietf.org/drafts/current/.
30 Internet-Drafts are draft documents valid for a maximum of six months
31 and may be updated, replaced, or obsoleted by other documents at any
32 time. It is inappropriate to use Internet-Drafts as reference
33 material or to cite them other than as "work in progress."
35 This Internet-Draft will expire on October 10, 2020.
37 Copyright Notice
39 Copyright (c) 2020 IETF Trust and the persons identified as the
40 document authors. All rights reserved.
42 This document is subject to BCP 78 and the IETF Trust's Legal
43 Provisions Relating to IETF Documents
44 (https://trustee.ietf.org/license-info) in effect on the date of
45 publication of this document. Please review these documents
46 carefully, as they describe your rights and restrictions with respect
47 to this document. Code Components extracted from this document must
48 include Simplified BSD License text as described in Section 4.e of
49 the Trust Legal Provisions and are provided without warranty as
50 described in the Simplified BSD License.
52 Table of Contents
54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
55 1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
56 1.2. Principles . . . . . . . . . . . . . . . . . . . . . . . 4
57 1.3. Delivery of Instance Data . . . . . . . . . . . . . . . . 4
58 1.4. Data Life cycle . . . . . . . . . . . . . . . . . . . . . 5
59 2. Instance Data File Format . . . . . . . . . . . . . . . . . . 5
60 2.1. Specifying the Content Schema . . . . . . . . . . . . . . 7
61 2.1.1. Inline Method . . . . . . . . . . . . . . . . . . . . 7
62 2.1.2. Simplified-Inline Method . . . . . . . . . . . . . . 8
63 2.1.3. URI Method . . . . . . . . . . . . . . . . . . . . . 8
64 2.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 8
65 2.2.1. UC1, Documenting Server Capabilities . . . . . . . . 8
66 2.2.2. UC2, Preloading Default Configuration . . . . . . . . 10
67 2.2.3. UC5, Storing diagnostics data . . . . . . . . . . . . 11
68 3. YANG Instance Data Model . . . . . . . . . . . . . . . . . . 12
69 3.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 12
70 3.2. YANG Model . . . . . . . . . . . . . . . . . . . . . . . 13
71 4. Security Considerations . . . . . . . . . . . . . . . . . . . 19
72 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
73 5.1. URI Registration . . . . . . . . . . . . . . . . . . . . 20
74 5.2. YANG Module Name Registration . . . . . . . . . . . . . . 20
75 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20
76 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
77 7.1. Normative References . . . . . . . . . . . . . . . . . . 20
78 7.2. Informative References . . . . . . . . . . . . . . . . . 21
79 Appendix A. Changes between revisions . . . . . . . . . . . . . 22
80 Appendix B. Backwards Compatibility . . . . . . . . . . . . . . 25
81 Appendix C. Detailed Use Cases . . . . . . . . . . . . . . . . . 25
82 C.1. Use Case 1: Early Documentation of Server Capabilities . 25
83 C.2. Use Case 2: Preloading Data . . . . . . . . . . . . . . . 26
84 C.3. Use Case 3: Documenting Factory Default Settings . . . . 27
85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27
87 1. Introduction
89 There is a need to document data defined in YANG models when a live
90 server is unavailable. Data is often needed at design or
91 implementation time or needed when a live running server is
92 unavailable. To facilitate this offline delivery of data, this
93 document specifies a standard format for YANG instance data sets and
94 YANG instance data files. The format of the instance data set is
95 defined by the "ietf-yang-instance-data" YANG module, see Section 3.
97 The YANG data model in this document conforms to the Network
98 Management Datastore Architecture (NMDA) defined in [RFC8342]
100 The following is a list of already implemented and potential use
101 cases.
103 UC1 Documentation of server capabilities
105 UC2 Preloading default configuration data
107 UC3 Documenting Factory Default Settings
109 UC4 Storing the configuration of a device, e.g., for backup, archive
110 or audit purposes
112 UC5 Storing diagnostics data
114 UC6 Allowing YANG instance data to potentially be carried within
115 other IPC message formats
117 UC7 Default instance data used as part of a templating solution
119 UC8 Providing data examples in RFCs or internet drafts
121 In Appendix C describes the first three use cases in detail.
123 There are many and varied use cases where YANG instance data could be
124 used. This document does not limit future uses of instance data
125 sets, so specifying how and when to use YANG instance data is out of
126 scope for this document. It is anticipated that other documents will
127 define specific use cases. Use cases are listed only as examples.
129 1.1. Terminology
131 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
132 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
133 "OPTIONAL" in this document are to be interpreted as described in BCP
134 14 [RFC2119] [RFC8174] when, and only when, they appear in all
135 capitals, as shown here.
137 Instance Data: A collection of instantiated data nodes.
139 Instance Data Set: A named set of data items annotated with metadata
140 that can be used as instance data in a YANG data tree.
142 Instance Data File: A file containing an instance data set formatted
143 according to the rules described in this document.
145 Content-schema: A set of YANG modules with their revision, supported
146 features, and deviations for which the instance data set contains
147 instance data.
149 Content defining YANG module: an individual YANG module that is part
150 of the content-schema.
152 The term "server" is used as defined in [RFC8342].
154 1.2. Principles
156 The following is a list of the basic principles of the instance data
157 format:
159 P1 Two standard formats shall be defined based on the XML and JSON
160 encodings.
162 P2 Instance data shall reuse existing encoding rules for YANG
163 defined data.
165 P3 Metadata about the instance data set (Section 2, Paragraph 9)
166 shall be defined.
168 P4 A YANG instance data set shall be allowed to contain data for
169 multiple YANG modules.
171 P5 Instance data shall be allowed to contain configuration data,
172 state data, or a mix of the two.
174 P6 Partial data sets shall be allowed.
176 P7 The YANG instance data format shall be usable for any data for
177 which YANG module(s) are defined and available to the reader,
178 independent of whether the module is implemented by a server.
180 P8 It shall be possible to report the identity of the datastore with
181 which the instance data set is associated.
183 1.3. Delivery of Instance Data
185 Instance data sets that are produced as a result of some sort of
186 specification or design effort may be available without the need for
187 a live server e.g., via download from the vendor's website, or in any
188 other way that product documentation is distributed.
190 Other instance data sets may be read from or produced by the YANG
191 server itself e.g., UC5 documenting diagnostic data.
193 1.4. Data Life cycle
195 A YANG instance data set is created at a specific point of time. If
196 the data changes afterwards, this is not represented in the instance
197 data set anymore. The current values may be retrieved at run-time
198 via NETCONF/RESTCONF or received e.g., in YANG-Push notifications.
200 Whether the instance data changes and if so, when and how, should be
201 described either in the instance data set's description statement or
202 in some other implementation specific manner.
204 2. Instance Data File Format
206 A YANG instance data file MUST contain a single instance data set and
207 no additional data.
209 The format of the instance data set is defined by the "ietf-yang-
210 instance-data" YANG module. It is made up of a header part and
211 content-data. The header part carries metadata for the instance data
212 set. The content-data, defined as an anydata data node, carries the
213 instance data that the user wants to document/provide. The syntax
214 and semantics of content-data is defined by the content-schema.
216 Two formats are specified based on the XML and JSON YANG encodings.
217 Later as other YANG encodings (e.g., CBOR) are defined, further
218 instance data formats may be specified.
220 The content-data part MUST conform to the content-schema, while
221 allowing for the exceptions listed below. The content-data part
222 SHALL follow the encoding rules defined in [RFC7950] for XML and
223 [RFC7951] for JSON and MUST use UTF-8 character encoding. Content-
224 data MAY include:
226 o metadata as defined by [RFC7952].
228 o a default attribute as defined in [RFC6243] section 6. and in
229 [RFC8040] section 4.8.9.
231 o origin metadata as specified in [RFC8526] and [RFC8527]
233 o implementation specific metadata relevant to individual data
234 nodes. Unknown metadata MUST be ignored by users of instance
235 data, allowing it to be used later for other purposes.
237 An instance data set MAY contain data for any number of YANG modules;
238 if needed it MAY carry the complete configuration and state data for
239 a server. Default values SHOULD NOT be included.
241 Configuration ("config true") and operational state data ("config
242 false") MAY be mixed in the instance data file.
244 Instance data files MAY contain partial data sets. This means
245 "mandatory", "min-elements", "require-instance true", "must" and
246 "when" constrains MAY be violated.
248 The name of the instance data file SHOULD take one of the following
249 two forms:
251 If "revision" information is present inside the data set:
253 instance-data-set-name ['@' revision-date] '.filetype'
255 E.g., acme-router-modules@2018-01-25.xml
257 If the leaf "name" is present in the instance data header, its
258 value SHOULD be used for the "instance-data-set-name". If the
259 "revision-date" is present in both the filename and in the
260 instance data header, the revision date in the file name MUST be
261 set to the latest revision date inside the instance data set.
263 If timestamp information inside the data set is present
265 instance-data-set-name ['@' timestamp] '.filetype'
267 E.g., acme-router-modules@2018-01-25T15_06_34_3+01_00.json
269 If the leaf "name" is present in the instance data header, its
270 value SHOULD be used for the "instance-data-set-name". If the
271 "timestamp" is present both in the filename and in the instance
272 data header, the timestamp in the file name SHOULD be set to the
273 timestamp inside the instance data set; the semicolons and the
274 decimal point, if present, shall be replaced by underscores.
276 The revision date or timestamp is optional. ".filetype" SHOULD be
277 ".json" or ".xml" according to the format used.
279 Metadata, information about the data set itself SHOULD be included in
280 the instance data set. Some metadata items are defined in the YANG
281 module "ietf-yang-instance-data", but other items MAY be used.
283 Metadata MUST include:
285 o Version of the YANG Instance Data format
287 Metadata SHOULD include:
289 o Name of the data set
291 o Content schema specification (i.e., the "content-schema" node)
293 o Description of the instance data set. The description SHOULD
294 contain information whether and how the data can change during the
295 lifetime of the server.
297 2.1. Specifying the Content Schema
299 To properly understand and use an instance data set, the user needs
300 to know the content-schema. One of the following methods SHOULD be
301 used:
303 Inline method: Include the needed information as part of the
304 instance data set.
306 Simplified-Inline method: Include the needed information as part
307 of the instance data set; short specification.
309 URI method: Include a URI that references another YANG instance
310 data file. This instance data file will use the same content-
311 schema as the referenced YANG instance data file. (if you don't
312 want to repeat the info again and again)
314 External Method: Do not include the "content-schema" node; the
315 user needs to obtain the information through external documents.
317 Additional methods e.g., a YANG-package based solution may be added
318 later.
320 Note, the specified content-schema only indicates the set of modules
321 that were used to define this YANG instance data set. Sometimes
322 instance data may be used for a server supporting a different YANG
323 module set. (e.g., for "UC2 Preloading Data" the instance data set
324 may not be updated every time the YANG modules on the server are
325 updated) Whether an instance data set originally defined using a
326 specific content-schema is usable with a different other schema
327 depends on many factors including the amount of differences and the
328 compatibility between the original and the other schema, considering
329 modules, revisions, features, deviations, the scope of the instance
330 data, etc.
332 2.1.1. Inline Method
334 One or more inline-module elements define YANG module(s) used to
335 specify the content defining YANG modules.
337 E.g., ietf-yang-library@2016-06-21
339 The anydata inline-schema carries instance data (conforming to the
340 inline-modules) that actually specifies the content defining YANG
341 modules including revision, supported features, deviations and any
342 relevant additional data (e.g., revision labels which can be used as
343 alternative to the revision
344 date[I-D.verdt-netmod-yang-module-versioning]). See Section 2.2.
346 2.1.2. Simplified-Inline Method
348 The instance data set contains a list of content defining YANG
349 modules including the revision date for each. Usage of this method
350 implies that the modules are used without any deviations and with all
351 features supported.
353 2.1.3. URI Method
355 The "same-schema-as-file" leaf SHALL contain a URI that references
356 another YANG instance data file. The current instance data file will
357 use the same content schema as the referenced file.
359 The referenced instance data file MAY have no content-data if it is
360 used solely for specifying the content-schema.
362 If a referenced instance data file is unavailable, content-schema is
363 unknown.
365 The URI method is advantageous when the user wants to avoid the
366 overhead of specifying the content-schema in each instance data file:
367 E.g., In UC6, when the system creates a diagnostic file every minute
368 to document the state of the server.
370 2.2. Examples
372 2.2.1. UC1, Documenting Server Capabilities
374 The example illustrates UC1 Section 1. It provides a list of
375 supported YANG modules and NETCONF capabilities for a server. It
376 uses the "inline" method to specify the content-schema.
378 The example uses artwork folding[I-D.ietf-netmod-artwork-folding].
380 ========== NOTE: '\' line wrapping per BCP XXX (RFC XXXX) ===========
382
383
386 acme-router-modules
387
388 ietf-yang-library@2016-06-21
389
390
392
393 ietf-yang-library
394 2016-06-21
395
396
397 ietf-netconf-monitoring
398 2010-10-04
399
400
401
402
403
404 1956-10-23
405 Initial version
406
407 Defines the minimal set of modules that any \
408 acme-router will contain.
409 info@acme.com
410
411
413
414 ietf-yang-library
415 2016-06-21
416 \
417 urn:ietf:params:xml:ns:yang:ietf-yang-library\
418
419 implement
420
421
422 ietf-system
423 2014-08-06
424 urn:ietf:params:xml:ns:yang:ietf-system
425 sys:authentication
426 sys:local-users
427
428 acme-system-ext
429 2018-08-06
430
431 implement
432
433
434 ietf-netconf-monitoring
435 2010-10-04
436 \
437 urn:ietf:params:xml:ns:yang:ietf-netconf-monitoring\
438
439 implement
440
441
442 ietf-yang-types
443 2013-07-15
444 urn:ietf:params:xml:ns:yang:ietf-yang-types\
445
446 import
447
448
449 acme-system-ext
450 2018-08-06
451 urn:rdns:acme.com:oammodel:acme-system-ext\
452
453 implement
454
455
456
458
459 \
460 urn:ietf:params:netconf:capability:validate:1.1\
461
462
463
464
465
467 Figure 1: Documenting server capabilities
469 2.2.2. UC2, Preloading Default Configuration
471 The example illustrates UC2 Section 1. It provides a default rule
472 set for a read-only operator role. It uses the "simplified-inline"
473 method for specifying the content-schema.
475
476
478 read-only-acm-rules
479
480 ietf-netconf-acm@2018-02-14
481
482
483 1776-07-04
484 Initial version
485
486 Access control rules for a read-only role.
487
488
489 true
490 deny
491 deny
492
493 read-only-role
494 read-only-group
495
496 read-all
497 *
498 read
499 permit
500
501
502
503
504
506 Figure 2: Preloading access control data
508 2.2.3. UC5, Storing diagnostics data
510 The example illustrates UC5 Section 1. An instance data set is
511 produced by the server every 15 minutes that contains statistics
512 about the NETCONF server. As a new set is produced periodically many
513 times a day a revision-date would be useless; instead a timestamp is
514 included.
516 {
517 "ietf-yang-instance-data:instance-data-set": {
518 "name": "acme-router-netconf-diagnostics",
519 "content-schema": {
520 "same-schema-as-file": "file:///acme-diagnostics-schema.json"
521 },
522 "timestamp": "2018-01-25T17:00:38Z",
523 "description": ["NETCONF statistics"],
524 "content-data": {
525 "ietf-netconf-monitoring:netconf-state": {
526 "statistics": {
527 "netconf-start-time ": "2018-12-05T17:45:00Z",
528 "in-bad-hellos ": "32",
529 "in-sessions ": "397",
530 "dropped-sessions ": "87",
531 "in-rpcs ": "8711",
532 "in-bad-rpcs ": "408",
533 "out-rpc-errors ": "408",
534 "out-notifications": "39007"
535 }
536 }
537 }
538 }
539 }
541 Figure 3: Storing diagnostics data
543 3. YANG Instance Data Model
545 3.1. Tree Diagram
547 The following tree diagram [RFC8340] provides an overview of the data
548 model.
550 module: ietf-yang-instance-data
551 structure instance-data-set:
552 +-- name? string
553 +-- format-version? string
554 +-- content-schema
555 | +-- (content-schema-spec)?
556 | +--:(simplified-inline)
557 | | +-- module* string
558 | +--:(inline) {inline-content-schema}?
559 | | +-- inline-module* string
560 | | +-- inline-schema
561 | +--:(uri)
562 | +-- same-schema-as-file? inet:uri
563 +-- description* string
564 +-- contact? string
565 +-- organization? string
566 +-- datastore? ds:datastore-ref
567 +-- revision* [date]
568 | +-- date string
569 | +-- description? string
570 +-- timestamp? yang:date-and-time
571 +-- content-data?
573 3.2. YANG Model
575 This YANG module imports typedefs from [RFC6991], identities from
576 [RFC8342] and the "structure" extension from
577 [I-D.ietf-netmod-yang-data-ext].
579 file "ietf-yang-instance-data@2020-04-02.yang"
580 module ietf-yang-instance-data {
581 yang-version 1.1;
582 namespace "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data";
583 prefix yid;
585 import ietf-yang-structure-ext {
586 prefix sx;
587 reference
588 "YANG Data Structure Extensions:
589 draft-ietf-netmod-yang-data-ext-05";
590 }
591 import ietf-datastores {
592 prefix ds;
593 reference
594 "RFC 8342: Network Management Datastore Architecture (NMDA)";
595 }
596 import ietf-inet-types {
597 prefix inet;
598 reference
599 "RFC 6991: Common YANG Data Types";
600 }
601 import ietf-yang-types {
602 prefix yang;
603 reference
604 "RFC 6991: Common YANG Data Types";
605 }
607 organization
608 "IETF NETMOD Working Group";
609 contact
610 "WG Web:
611 WG List:
613 Author: Balazs Lengyel
614 ";
615 description
616 "The module defines the structure and content of YANG
617 instance data sets.
619 The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL',
620 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED',
621 'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document
622 are to be interpreted as described in BCP 14 (RFC 2119)
623 (RFC 8174) when, and only when, they appear in all
624 capitals, as shown here.
626 Copyright (c) 2020 IETF Trust and the persons identified as
627 authors of the code. All rights reserved.
629 Redistribution and use in source and binary forms, with or
630 without modification, is permitted pursuant to, and subject
631 to the license terms contained in, the Simplified BSD License
632 set forth in Section 4.c of the IETF Trust's Legal Provisions
633 Relating to IETF Documents
634 (http://trustee.ietf.org/license-info).
636 This version of this YANG module is part of RFC XXXX; see
637 the RFC itself for full legal notices.";
639 revision 2020-04-02 {
640 description
641 "Initial revision.";
642 reference
643 "RFC XXXX: YANG Instance Data Format";
644 }
645 feature inline-content-schema {
646 description
647 "This feature indicates that inline content-schema
648 option is supported.";
649 }
651 typedef module-with-revision-date {
652 type string {
653 pattern '[a-zA-Z_][a-zA-Z0-9\-_.]*' +
654 '(@\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1]))?';
655 pattern '.|..|[^xX].*|.[^mM].*|..[^lL].*';
656 }
657 description
658 "A type definining a module name and an optional revision
659 date, e.g. ietf-yang-library@2016-06-21";
660 }
662 sx:structure "instance-data-set" {
663 description
664 "A data structure to define a format for
665 YANG instance data sets. Consists of meta-data about
666 the instance data set and the real content-data.";
667 leaf name {
668 type string;
669 description
670 "An arbitrary name for the YANG instance data set. This
671 value is primarily used for descriptive purposes. However,
672 when the instance data set is saved to a file, then the
673 filename MUST encode the name's value, per Section 3
674 of RFC XXXX.";
675 }
676 leaf format-version {
677 type string {
678 pattern '\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1])';
679 }
680 default "2020-04-02";
681 description
682 "The 'revision' of the 'ietf-yang-instance-data' module
683 used to encode this 'instance-data-set'.";
684 }
685 container content-schema {
686 description
687 "The content schema used to create the instance data set.
688 If not present the user needs to obtain the information
689 through external documents.";
690 choice content-schema-spec {
691 description
692 "Specification of the content-schema.";
694 case simplified-inline {
695 leaf-list module {
696 type module-with-revision-date;
697 description
698 "The list of content defining YANG modules.
700 The value SHALL start with the module name.
701 If the module contains a revision statement the
702 revision date SHALL be included in the leaf-list
703 entry. If other methods (e.g., revision-label) are
704 defined to identify individual module revisions
705 those MAY be used instead of using a revision date.
707 E.g., ietf-yang-library@2016-06-21
709 Usage of this leaf-list implies the modules are
710 used without any deviations and with all features
711 supported. Multiple revisions of the same module
712 MUST NOT be specified.";
713 }
714 }
715 case inline {
716 if-feature "inline-content-schema";
717 leaf-list inline-module {
718 type module-with-revision-date;
719 min-elements 1;
720 description
721 "Indicates that content defining YANG modules
722 are specified inline.
724 The value SHALL start with the module name.
725 If the module contains a revision statement the
726 revision date SHALL be included in the leaf-list
727 entry. If other methods (e.g., revision-label) are
728 defined to identify individual module revisions
729 those MAY be used instead of using a revision date.
731 E.g., ietf-yang-library@2016-06-21
733 The first item is either ietf-yang-library or some
734 other YANG module that contains a list of YANG modules
735 with their name, revision-date, supported-features,
736 and deviations. The usage of revision '2019-01-04'
737 of the 'ietf-yang-library' module MUST be supported.
738 Using other modules, module versions MAY also be
739 supported.
741 Some versions of ietf-yang-library MAY contain
742 different module-sets for different datastores. In
743 this case the instance data set MUST contain the
744 'datastore' leaf and instance data for the
745 ietf-yang-library MUST also contain information
746 specifying the module-set for the relevant datastore.
748 Subsequent items MAY specify YANG modules augmenting
749 the first module with useful data
750 (e.g., revision label).";
751 reference
752 "RFC 8525";
753 }
754 anydata inline-schema {
755 mandatory true;
756 description
757 "Instance data corresponding to the YANG modules
758 specified in the inline-module nodes defining the set
759 of content defining YANG modules for this
760 instance-data-set.";
761 }
762 }
763 case uri {
764 leaf same-schema-as-file {
765 type inet:uri;
766 description
767 "A reference to another YANG instance data file.
768 This instance data file uses the same
769 content schema as the referenced file.";
770 }
771 }
772 }
773 }
774 leaf-list description {
775 type string;
776 description
777 "Description of the instance data set.";
778 }
779 leaf contact {
780 type string;
781 description
782 "Contact information for the person or
783 organization to whom queries concerning this
784 instance data set should be sent.";
785 }
786 leaf organization {
787 type string;
788 description
789 "Organization responsible for the instance
790 data set.";
791 }
792 leaf datastore {
793 type ds:datastore-ref;
794 description
795 "The identity of the datastore with which the
796 instance data set is associated, e.g., the datastore from
797 where the data was read or the datastore into which the data
798 may be loaded or the datastore which is being documented.
799 If a single specific datastore cannot be specified, the
800 leaf MUST be absent.
802 If this leaf is absent, then the datastore to which the
803 instance data belongs is undefined.";
804 }
805 list revision {
806 key "date";
807 description
808 "Instance data sets that are produced as
809 a result of some sort of specification or design effort
810 SHOULD have at least one revision entry. For every
811 published editorial change, a new one SHOULD be added
812 in front of the revisions sequence so that all
813 revisions are in reverse chronological order.
815 Instance data sets that are read from
816 or produced by a server or otherwise
817 subject to frequent updates or changes: revision
818 SHOULD NOT be present";
819 leaf date {
820 type string {
821 pattern '\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1])';
822 }
823 description
824 "Specifies the date the instance data set
825 was last modified. Formatted as YYYY-MM-DD";
826 }
827 leaf description {
828 type string;
829 description
830 "Description of this revision of the instance data set.";
831 }
832 }
833 leaf timestamp {
834 type yang:date-and-time;
835 description
836 "The date and time when the instance data set
837 was last modified.
839 Instance data sets that are read from or produced
840 by a server or otherwise subject to frequent
841 updates or changes: timestamp SHOULD be present";
842 }
843 anydata content-data {
844 description
845 "Contains the real instance data.
846 The data MUST conform to the relevant YANG modules specified
847 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, so it does not follow the
859 security considerations template for YANG models. The instance data
860 is designed to be accessed as a stored file or over any file access
861 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.
870 The security sensitivity of the instance data in the content part is
871 completely dependent on the content schema. Depending on the nature
872 of the instance data, instance data files MAY need to be handled in a
873 secure way. The same kind of handling should be applied, that would
874 be needed for the result of a read operation returning the same data.
876 Instance data files should be protected against modification or
877 unauthorized access using normal file handling mechanisms. Care
878 should be taken, when copying the original files or providing file
879 access for additional users, not to reveal information
880 unintentionally.
882 5. IANA Considerations
884 This document registers one URI and one YANG module.
886 5.1. URI Registration
888 This document registers one URI in the IETF XML registry [RFC3688].
889 Following the format in RFC 3688, the following registration is
890 requested to be made:
892 URI: urn:ietf:params:xml:ns:yang:ietf-yang-instance-data
893 Registrant Contact: The IESG.
894 XML: N/A, the requested URI is an XML namespace.
896 5.2. YANG Module Name Registration
898 This document registers one YANG module in the YANG Module Names
899 registry [RFC6020].
901 name: ietf-yang-instance-data
902 namespace: urn:ietf:params:xml:ns:yang:ietf-yang-instance-data
903 prefix: yid
904 reference: RFC XXXX
906 6. Acknowledgments
908 For their valuable comments, discussions, and feedback, we wish to
909 acknowledge Andy Bierman, Juergen Schoenwaelder, Rob Wilton, Joe
910 Clarke, Kent Watsen Martin Bjorklund, Ladislav Lhotka, Qin Wu and
911 other members of the Netmod WG.
913 7. References
915 7.1. Normative References
917 [I-D.ietf-netmod-yang-data-ext]
918 Bierman, A., Bjorklund, M., and K. Watsen, "YANG Data
919 Structure Extensions", draft-ietf-netmod-yang-data-ext-05
920 (work in progress), December 2019.
922 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
923 Requirement Levels", BCP 14, RFC 2119,
924 DOI 10.17487/RFC2119, March 1997,
925 .
927 [RFC6243] Bierman, A. and B. Lengyel, "With-defaults Capability for
928 NETCONF", RFC 6243, DOI 10.17487/RFC6243, June 2011,
929 .
931 [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types",
932 RFC 6991, DOI 10.17487/RFC6991, July 2013,
933 .
935 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
936 RFC 7950, DOI 10.17487/RFC7950, August 2016,
937 .
939 [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG",
940 RFC 7951, DOI 10.17487/RFC7951, August 2016,
941 .
943 [RFC7952] Lhotka, L., "Defining and Using Metadata with YANG",
944 RFC 7952, DOI 10.17487/RFC7952, August 2016,
945 .
947 [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
948 Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
949 .
951 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
952 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
953 May 2017, .
955 [RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
956 and R. Wilton, "Network Management Datastore Architecture
957 (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018,
958 .
960 [RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K.,
961 and R. Wilton, "YANG Library", RFC 8525,
962 DOI 10.17487/RFC8525, March 2019,
963 .
965 [RFC8526] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
966 and R. Wilton, "NETCONF Extensions to Support the Network
967 Management Datastore Architecture", RFC 8526,
968 DOI 10.17487/RFC8526, March 2019,
969 .
971 [RFC8527] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K.,
972 and R. Wilton, "RESTCONF Extensions to Support the Network
973 Management Datastore Architecture", RFC 8527,
974 DOI 10.17487/RFC8527, March 2019,
975 .
977 7.2. Informative References
979 [I-D.ietf-netmod-artwork-folding]
980 Watsen, K., Auerswald, E., Farrel, A., and Q. WU,
981 "Handling Long Lines in Inclusions in Internet-Drafts and
982 RFCs", draft-ietf-netmod-artwork-folding-12 (work in
983 progress), January 2020.
985 [I-D.ietf-netmod-factory-default]
986 WU, Q., Lengyel, B., and Y. Niu, "A YANG Data Model for
987 Factory Default Settings", draft-ietf-netmod-factory-
988 default-14 (work in progress), February 2020.
990 [I-D.verdt-netmod-yang-module-versioning]
991 Claise, B., Clarke, J., Rahman, R., Wilton, R., Lengyel,
992 B., Sterne, J., and K. D'Souza, "Updated YANG Module
993 Revision Handling", draft-verdt-netmod-yang-module-
994 versioning-01 (work in progress), October 2019.
996 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
997 DOI 10.17487/RFC3688, January 2004,
998 .
1000 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
1001 the Network Configuration Protocol (NETCONF)", RFC 6020,
1002 DOI 10.17487/RFC6020, October 2010,
1003 .
1005 [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams",
1006 BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018,
1007 .
1009 [RFC8632] Vallin, S. and M. Bjorklund, "A YANG Data Model for Alarm
1010 Management", RFC 8632, DOI 10.17487/RFC8632, September
1011 2019, .
1013 [RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications
1014 for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641,
1015 September 2019, .
1017 Appendix A. Changes between revisions
1019 Note to RFC Editor (To be removed by RFC Editor)
1021 v09 - v10
1023 o Editorial updates
1025 v08 - v09
1026 o Removed reference to similar to get reply
1028 o Introduced artwork folding in the examples
1030 v07 - v08
1032 o Moved compatibility into appendix
1034 o Renamed yid-version to format-version. Changed format to date of
1035 the YANG module
1037 o Made support of ietf-yang-library mandatory if inline-content-
1038 schema is supported
1040 o Many small changes based on WGLC
1042 v06 - v07
1044 o Updated terminology, use-cases
1046 o Many small changes based on WGLC
1048 v05 - v06
1050 o Modified module name format, removed .yin or .yang extension
1052 o Removed pattern for module and inline-module. The usage of
1053 revision-label should also be allowed.
1055 v04 - v05
1057 o Updated according to YANG-Doctor review
1059 o Updated security considerations
1061 o Added a wrapping container for the schema, and renamed the data
1062 nodes in the inline and uri cases.
1064 o Allowed .yin for simplified-inline schema naming. Made date
1065 optional if it is unavailable in the YANG module.
1067 o Added a mandatory yid-version to the header metadata to allow
1068 later updates of the module.
1070 v03 - v04
1072 o removed entity-tag and last-modified timestamp
1073 o Added simplified-inline method of content-schema specification
1075 v02 - v03
1077 o target renamed to "content-schema" and "content defining YANG
1078 module(s)"
1080 o Made name of instance data set optional
1082 o Updated according to draft-ietf-netmod-yang-data-ext-03
1084 o Clarified that entity-tag and last-modified timestamp are encoded
1085 as metadata. While they contain useful data, the HTTP-header
1086 based encoding from Restconf is not suitable.
1088 v01 - v02
1090 o Removed design time from terminology
1092 o Defined the format of the content-data part by referencing various
1093 RFCs and drafts instead of the result of the get-data and get
1094 operations.
1096 o Changed target-ptr to a choice
1098 o Inline target-ptr may include augmenting modules and alternatives
1099 to ietf-yang-library
1101 o Moved list of target modules into a separate
1102 element.
1104 o Added backwards compatibility considerations
1106 v00 - v01
1108 o Added the target-ptr metadata with 3 methods
1110 o Added timestamp metadata
1112 o Removed usage of dedicated .yid file extension
1114 o Added list of use cases
1116 o Added list of principles
1118 o Updated examples
1120 o Moved detailed use case descriptions to appendix
1122 Appendix B. Backwards Compatibility
1124 The concept of backwards compatibility and what changes are backwards
1125 compatible are not defined for instance data sets as it is highly
1126 dependent on the specific use case and the content-schema.
1128 For instance data that is the result of a design or specification
1129 activity, some changes that may be good to avoid are listed below.
1131 YANG uses the concept of managed entities identified by key values;
1132 if the connection between the represented entity and the key value is
1133 not preserved during an update, this may lead to the following
1134 problems.
1136 o If the key value of a list entry that represents the same managed
1137 entity as before is changed, the user may mistakenly identify the
1138 list entry as new.
1140 o If the meaning of a list entry is changed, but the key values are
1141 not (e.g., redefining an alarm-type but not changing its alarm-
1142 type-id) the change may not be noticed.
1144 o If the key value of a previously removed list entry is reused for
1145 a different entity, the change may be misinterpreted as
1146 reintroducing the previous entity.
1148 Appendix C. Detailed Use Cases
1150 This section is non-normative.
1152 C.1. Use Case 1: Early Documentation of Server Capabilities
1154 A server has a number of server-capabilities that are defined in YANG
1155 modules and can be retrieved from the server using protocols like
1156 NETCONF or RESTCONF. Server capabilities include:
1158 o data defined in "ietf-yang-library": YANG modules, submodules,
1159 features, deviations, schema-mounts, and datastores supported
1160 ([RFC8525])
1162 o alarms supported ([RFC8632])
1164 o data nodes and subtrees that support or do not support on-change
1165 notifications ([RFC8641])
1167 o netconf-capabilities in ietf-netconf-monitoring
1168 While it is good practice to allow a client to query these
1169 capabilities from the live server, that is often not possible.
1171 Often when a network node is released, an associated NMS (network
1172 management system) is also released with it. The NMS depends on the
1173 capabilities of the server. During NMS implementation, information
1174 about server capabilities is needed. If the information is
1175 unavailable early in some offline document, but only as instance data
1176 from the live network node, the NMS implementation will be delayed,
1177 because it has to wait until the network node is ready. Also
1178 assuming that all NMS implementors will have a correctly configured
1179 network nodes from which data can be retrieved, is a very expensive
1180 proposition. (An NMS may handle dozens of node types.)
1182 Network operators often build their own home-grown NMS systems that
1183 need to be integrated with a vendor's network node. The operator
1184 needs to know the network node's server capabilities in order to do
1185 this. Moreover, the network operator's decision to buy a vendor's
1186 product may even be influenced by the network node's OAM feature set
1187 documented as the server's capabilities.
1189 Beside NMS implementors, system integrators and many others also need
1190 the same information early. Examples could be model driven testing,
1191 generating documentation, etc.
1193 Most server-capabilities are relatively stable and change only during
1194 upgrade or due to licensing or the addition or removal of hardware.
1195 They are usually defined by a vendor at design time, before the
1196 product is released. It is feasible and advantageous to define/
1197 document them early e.g., in a YANG instance data File.
1199 It is anticipated that a separate IETF document will define in detail
1200 how and which set of server capabilities should be documented.
1202 C.2. Use Case 2: Preloading Data
1204 There are parts of the configuration that must be fully configurable
1205 by the operator. However, often a simple default configuration will
1206 be sufficient.
1208 One example is access control groups/roles and related rules. While
1209 a sophisticated operator may define dozens of different groups, often
1210 a basic (read-only operator, read-write system administrator,
1211 security-administrator) triplet will be enough. Vendors will often
1212 provide such default configuration data to make device configuration
1213 easier for an operator.
1215 Defining access control data is a complex task. To help, the device
1216 vendor predefines a set of default groups (/nacm:nacm/groups) and
1217 rules for these groups to access specific parts of common models
1218 (/nacm:nacm/rule-list/rule).
1220 YANG instance data files are used to document and/or preload the
1221 default configuration.
1223 C.3. Use Case 3: Documenting Factory Default Settings
1225 Nearly every server has a factory default configuration. If the
1226 system is really badly misconfigured or if the current configuration
1227 is to be abandoned, the system can be reset the default factory
1228 configuration.
1230 In NETCONF, the operation can already be used to
1231 reset the startup datastore. There are ongoing efforts to introduce
1232 a new, more generic factory-reset operation for the same purpose
1233 [I-D.ietf-netmod-factory-default]
1235 The operator currently has no way to know what the default
1236 configuration actually contains. YANG instance data can also be used
1237 to document the factory default configuration.
1239 Authors' Addresses
1241 Balazs Lengyel
1242 Ericsson
1243 Magyar Tudosok korutja 11
1244 1117 Budapest
1245 Hungary
1247 Phone: +36-70-330-7909
1248 Email: balazs.lengyel@ericsson.com
1250 Benoit Claise
1251 Cisco Systems, Inc.
1252 De Kleetlaan 6a b1
1253 1831 Diegem
1254 Belgium
1256 Phone: +32 2 704 5622
1257 Email: bclaise@cisco.com