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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-15) exists of draft-ietf-netmod-factory-default-14 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Netmod B. Lengyel 3 Internet-Draft Ericsson 4 Intended status: Standards Track B. Claise 5 Expires: September 21, 2020 Cisco Systems, Inc. 6 March 20, 2020 8 YANG Instance Data File Format 9 draft-ietf-netmod-yang-instance-file-format-10 11 Abstract 13 There is a need to document data defined in YANG models when a live 14 server is not available. Data is often needed already at design or 15 implementation time or needed by groups that do not have a live 16 running server available. This document specifies a standard file 17 format for YANG instance data, which follows the syntax and semantics 18 of existing 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 September 21, 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. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 55 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 56 2.1. Principles . . . . . . . . . . . . . . . . . . . . . . . 4 57 2.2. Delivery of Instance Data . . . . . . . . . . . . . . . . 4 58 2.3. Data Life cycle . . . . . . . . . . . . . . . . . . . . . 5 59 3. Instance Data File Format . . . . . . . . . . . . . . . . . . 5 60 3.1. Specifying the Content Schema . . . . . . . . . . . . . . 7 61 3.1.1. Inline Method . . . . . . . . . . . . . . . . . . . . 7 62 3.1.2. Simplified-Inline Method . . . . . . . . . . . . . . 8 63 3.1.3. URI Method . . . . . . . . . . . . . . . . . . . . . 8 64 3.2. Examples . . . . . . . . . . . . . . . . . . . . . . . . 8 65 4. YANG Instance Data Model . . . . . . . . . . . . . . . . . . 12 66 4.1. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 12 67 4.2. YANG Model . . . . . . . . . . . . . . . . . . . . . . . 13 68 5. Security Considerations . . . . . . . . . . . . . . . . . . . 19 69 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 70 6.1. URI Registration . . . . . . . . . . . . . . . . . . . . 19 71 6.2. YANG Module Name Registration . . . . . . . . . . . . . . 20 72 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 20 73 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 20 74 8.1. Normative References . . . . . . . . . . . . . . . . . . 20 75 8.2. Informative References . . . . . . . . . . . . . . . . . 21 76 Appendix A. Changes between revisions . . . . . . . . . . . . . 22 77 Appendix B. Backwards Compatibility . . . . . . . . . . . . . . 24 78 Appendix C. Detailed Use Cases - Non-Normative . . . . . . . . . 25 79 C.1. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . 25 80 C.1.1. Use Case 1: Early Documentation of Server 81 Capabilities . . . . . . . . . . . . . . . . . . . . 25 82 C.1.2. Use Case 2: Preloading Data . . . . . . . . . . . . . 26 83 C.1.3. Use Case 3: Documenting Factory Default Settings . . 27 84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 86 1. Terminology 88 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 89 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 90 "OPTIONAL" in this document are to be interpreted as described in BCP 91 14 [RFC2119] [RFC8174] when, and only when, they appear in all 92 capitals, as shown here. 94 Instance Data: A collection of instantiated data nodes. 96 Instance Data Set: A named set of data items annotated with metadata 97 that can be used as instance data in a YANG data tree. 99 Instance Data File: A file containing an instance data set formatted 100 according to the rules described in this document. 102 Content-schema: A set of YANG modules with their revision, supported 103 features, and deviations for which the instance data set contains 104 instance data. 106 Content defining YANG module: an individual YANG module that is part 107 of the content-schema. 109 The term Server is used as defined in [RFC8342]. 111 2. Introduction 113 There is a need to document data defined in YANG models when a live 114 server is not available. Data is often needed already at design or 115 implementation time or needed by groups that do not have a live 116 running server available. To facilitate this offline delivery of 117 data, this document specifies a standard format for YANG instance 118 data sets and YANG instance data files. The format of the instance 119 data set is defined by the ietf-yang- instance-data YANG module, see 120 Section 4. The YANG data model in this document conforms to the 121 Network Management Datastore Architecture (NMDA) defined in [RFC8342] 123 The following is a list of already implemented and potential use 124 cases. 126 UC1 Documentation of server capabilities 128 UC2 Preloading default configuration data 130 UC3 Documenting Factory Default Settings 132 UC4 Storing the configuration of a device, e.g., for backup, archive 133 or audit purposes 135 UC5 Storing diagnostics data 137 UC6 Allowing YANG instance data to potentially be carried within 138 other IPC message formats 140 UC7 Default instance data used as part of a templating solution 142 UC8 Providing data examples in RFCs or internet drafts 143 In Appendix C we describe the first three use cases in detail. 145 There are many and varied use cases where YANG instance data could be 146 used. We do not want to limit future uses of instance data sets, so 147 specifying how and when to use YANG instance data is out of scope for 148 this document. It is anticipated that other documents will define 149 specific use cases. Use cases are listed here only to indicate the 150 need for this work. 152 2.1. 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 3, 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 actually implemented by a 177 server. 179 P8 It shall be possible to report the identity of the datastore with 180 which the instance data set is associated. 182 2.2. Delivery of Instance Data 184 Instance data sets that are produced as a result of some sort of 185 specification or design effort may be available without the need for 186 a live server e.g., via download from the vendor's website, or in any 187 other way that product documentation is distributed. 189 Other instance data sets may be read from or produced by the YANG 190 server itself e.g., UC5 documenting diagnostic data. 192 2.3. Data Life cycle 194 A YANG instance data set is created at a specific point of time. If 195 the data changes afterwards, this is not represented in the instance 196 data set anymore. The current values may be retrieved at run-time 197 via NETCONF/RESTCONF or received e.g., in YANG-Push notifications. 199 Whether the instance data changes and if so, when and how, should be 200 described either in the instance data set's description statement or 201 in some other implementation specific manner. 203 3. Instance Data File Format 205 A YANG instance data file MUST contain a single instance data set and 206 no additional data. 208 The format of the instance data set is defined by the ietf-yang- 209 instance-data YANG module. It is made up of a header part and 210 content-data. The header part carries metadata for the instance data 211 set. The content-data, defined as an anydata data node, carries the 212 instance data that we want to document/provide. The syntax and 213 semantics of content-data is defined by the content-schema. 215 Two formats are specified based on the XML and JSON YANG encodings. 216 Later as other YANG encodings (e.g., CBOR) are defined, further 217 instance data formats may be specified. 219 The content-data part MUST conform to the content-schema, while 220 allowing for the exceptions listed below. The content-data part 221 SHALL follow the encoding rules defined in [RFC7950] for XML and 222 [RFC7951] for JSON and MUST use UTF-8 character encoding. Content- 223 data MAY include: 225 metadata as defined by [RFC7952]. 227 a default attribute as defined in [RFC6243] section 6. and in 228 [RFC8040] section 4.8.9. 230 origin metadata as specified in [RFC8526] and [RFC8527] 232 implementation specific metadata relevant to individual data 233 nodes. Unknown metadata MUST be ignored by users of instance 234 data, allowing it to be used later for other purposes. 236 An instance data set MAY contain data for any number of YANG modules; 237 if needed it MAY carry the complete configuration and state data set 238 for a server. Default values SHOULD NOT be included. 240 Config=true and config=false data MAY be mixed in the instance data 241 file. 243 Instance data files MAY contain partial data sets. This means 244 mandatory, min-elements, require-instance=true, must and when 245 constrains MAY be violated. 247 The name of the instance data file SHOULD take one of the following 248 two forms: 250 If revision information inside the data set is present 252 * instance-data-set-name ['@' revision-date] '.filetype' 254 * E.g., acme-router-modules@2018-01-25.xml 256 If the leaf "name" is present in the instance data header, this 257 MUST be used. If the "revision-date" is present in both the 258 filename and in the instance data header, the revision date in the 259 file name MUST be set to the latest revision date inside the 260 instance data set. 262 If timestamp information inside the data set is present 264 * instance-data-set-name ['@' timestamp] '.filetype' 266 * E.g., acme-router-modules@2018-01-25T15_06_34_3+01_00.json 268 If the leaf "name" is present in the instance data header, this 269 MUST be used. If the "timestamp" is present both in the filename 270 and in the instance data header, the timestamp in the file name 271 MUST be set to the timestamp inside the instance data set; the 272 semicolons and the decimal point, if present, shall be replaced by 273 underscores. 275 The revision date or timestamp is optional. ".filetype" SHALL be 276 ".json" or ".xml" according to the format used. 278 Metadata, information about the data set itself SHOULD be included in 279 the instance data set. Some metadata items are defined in the YANG 280 module ietf-yang-instance-data, but other items MAY also be used. 281 Metadata MUST include: 283 Version of the YANG Instance Data format 285 Metadata SHOULD include: 287 o Name of the data set 288 o Content schema specification 290 o Description of the instance data set. The description SHOULD 291 contain information whether and how the data can change during the 292 lifetime of the server. 294 3.1. Specifying the Content Schema 296 To properly understand and use an instance data set, the user needs 297 to know the content-schema. One of the following methods SHOULD be 298 used: 300 Inline method: Include the needed information as part of the 301 instance data set. 303 Simplified-Inline method: Include the needed information as part 304 of the instance data set; short specification. 306 URI method: Include a URI that references another YANG instance 307 data file. This instance data file will use the same content- 308 schema as the referenced YANG instance data file. (if you don't 309 want to repeat the info again and again) 311 External Method: Do not include the content-schema, the user needs 312 to obtain the information through external documents. 314 Additional methods e.g., a YANG-package based solution may be added 315 later. 317 Note, the specified content-schema only indicates the set of modules 318 that were used to define this YANG instance data set. Sometimes 319 instance data may be used for a server supporting a different YANG 320 module set. (e.g., for "UC2 Preloading Data" the instance data set 321 may not be updated every time the YANG modules on the server are 322 updated) Whether an instance data set originally defined using a 323 specific content-schema is usable with a different other schema 324 depends on many factors including the amount of differences and the 325 compatibility between the original and the other schema, considering 326 modules, revisions, features, deviations, the scope of the instance 327 data, etc. 329 3.1.1. Inline Method 331 One or more inline-module elements define YANG module(s) used to 332 specify the content defining YANG modules. 334 E.g., ietf-yang-library@2016-06-21 336 The anydata inline-schema carries instance data (conforming to the 337 inline-modules) that actually specifies the content defining YANG 338 modules including revision, supported features, deviations and any 339 relevant additional data (e.g., revision labels 340 [I-D.verdt-netmod-yang-module-versioning]). See Section 3.2. 342 3.1.2. Simplified-Inline Method 344 The instance data set contains a list of content defining YANG 345 modules including the revision date for each. Usage of this method 346 implies that the modules are used without any deviations and with all 347 features supported. 349 3.1.3. URI Method 351 The same-schema-as-file leaf SHALL contain a URI that references 352 another YANG instance data file. The current instance data file will 353 use the same content schema as the referenced file. 355 The referenced instance data file MAY have no content-data if it is 356 used solely for specifying the content-schema. 358 If a referenced instance data file is not available, content-schema 359 is unknown. 361 The URI method is advantageous when the user wants to avoid the 362 overhead of specifying the content-schema in each instance data file: 363 E.g., In Use Case 6, when the system creates a diagnostic file every 364 minute to document the state of the server. 366 3.2. Examples 368 The following examples use artwork folding 369 [I-D.ietf-netmod-artwork-folding] for better formatting. 371 The following example is based on "UC1, Documenting Server 372 Capabilities". It provides (a shortened) list of supported YANG 373 modules and NETCONF capabilities for a server. It uses the inline 374 method to specify the content-schema. 376 ========== NOTE: '\' line wrapping per BCP XXX (RFC XXXX) =========== 378 379 381 acme-router-modules 382 383 ietf-yang-library@2016-06-21 384 385 387 388 ietf-yang-library 389 2016-06-21 390 391 392 ietf-netconf-monitoring 393 2010-10-04 394 395 396 397 398 399 1956-10-23 400 Initial version 401 402 Defines the minimal set of modules that any \ 403 acme-router will contain. 404 info@acme.com 405 406 409 411 412 ietf-yang-library 413 2016-06-21 414 \ 415 urn:ietf:params:xml:ns:yang:ietf-yang-library\ 416 417 implement 418 419 420 ietf-system 421 2014-08-06 422 urn:ietf:params:xml:ns:yang:ietf-system 423 sys:authentication 424 sys:local-users 425 426 acme-system-ext 427 2018-08-06 428 429 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: XML Instance Data Set - Use case 1, Documenting server 458 capabilities 460 The following example is based on "UC2, Preloading Default 461 Configuration". It provides a (shortened) default rule set for a 462 read-only operator role. It uses the inline method for specifying 463 the content-schema. 465 466 468 read-only-acm-rules 469 470 ietf-netconf-acm@2018-02-14 471 472 473 1776-07-04 474 Initial version 475 476 Access control rules for a read-only role. 477 478 479 true 480 deny 481 deny 482 483 read-only-role 484 read-only-group 485 486 read-all 487 * 488 read 489 permit 490 491 492 493 494 496 Figure 2: XML Instance Data Set - Use case 2, Preloading access 497 control data 499 The following example is based on UC5 Storing diagnostics data. An 500 instance data set is produced by the server every 15 minutes that 501 contains statistics about NETCONF. As a new set is produced 502 periodically many times a day a revision-date would be useless; 503 instead a timestamp is included. 505 { 506 "ietf-yang-instance-data:instance-data-set": { 507 "name": "acme-router-netconf-diagnostics", 508 "content-schema": { 509 "same-schema-as-file": "file:///acme-diagnostics-schema.json" 510 }, 511 "timestamp": "2018-01-25T17:00:38Z", 512 "description": ["NETCONF statistics"], 513 "content-data": { 514 "ietf-netconf-monitoring:netconf-state": { 515 "statistics": { 516 "netconf-start-time ": "2018-12-05T17:45:00Z", 517 "in-bad-hellos ": "32", 518 "in-sessions ": "397", 519 "dropped-sessions ": "87", 520 "in-rpcs ": "8711", 521 "in-bad-rpcs ": "408", 522 "out-rpc-errors ": "408", 523 "out-notifications": "39007" 524 } 525 } 526 } 527 } 528 } 530 Figure 3: JSON Instance Data File example - UC5 Storing diagnostics 531 data 533 4. YANG Instance Data Model 535 4.1. Tree Diagram 537 The following tree diagram [RFC8340] provides an overview of the data 538 model. 540 module: ietf-yang-instance-data 541 structure instance-data-set: 542 +-- name? string 543 +-- format-version? string 544 +-- content-schema 545 | +-- (content-schema-spec)? 546 | +--:(simplified-inline) 547 | | +-- module* string 548 | +--:(inline) {inline-content-schema}? 549 | | +-- inline-module* string 550 | | +-- inline-schema 551 | +--:(uri) 552 | +-- same-schema-as-file? inet:uri 553 +-- description* string 554 +-- contact? string 555 +-- organization? string 556 +-- datastore? ds:datastore-ref 557 +-- revision* [date] 558 | +-- date string 559 | +-- description? string 560 +-- timestamp? yang:date-and-time 561 +-- content-data? 563 4.2. YANG Model 565 This YANG module imports typedefs from [RFC6991], identities from 566 [RFC8342] and the "structure" extension from 567 [I-D.ietf-netmod-yang-data-ext]. 569 file "ietf-yang-instance-data@2020-03-19.yang" 570 module ietf-yang-instance-data { 571 yang-version 1.1; 572 namespace "urn:ietf:params:xml:ns:yang:ietf-yang-instance-data"; 573 prefix yid; 575 import ietf-yang-structure-ext { 576 prefix sx; 577 reference 578 "YANG Data Structure Extensions: 579 draft-ietf-netmod-yang-data-ext-05"; 580 } 581 import ietf-datastores { 582 prefix ds; 583 reference 584 "RFC 8342: Network Management Datastore Architecture (NMDA)"; 585 } 586 import ietf-inet-types { 587 prefix inet; 588 reference 589 "RFC 6991: Common YANG Data Types"; 590 } 591 import ietf-yang-types { 592 prefix yang; 593 reference 594 "RFC 6991: Common YANG Data Types"; 595 } 597 organization 598 "IETF NETMOD Working Group"; 599 contact 600 "WG Web: 601 WG List: 603 Author: Balazs Lengyel 604 "; 605 description 606 "The module defines the structure and content of YANG 607 instance data sets. 609 The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 610 'SHALL NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 611 'NOT RECOMMENDED', 'MAY', and 'OPTIONAL' in this document 612 are to be interpreted as described in BCP 14 (RFC 2119) 613 (RFC 8174) when, and only when, they appear in all 614 capitals, as shown here. 616 Copyright (c) 2020 IETF Trust and the persons identified as 617 authors of the code. All rights reserved. 619 Redistribution and use in source and binary forms, with or 620 without modification, is permitted pursuant to, and subject 621 to the license terms contained in, the Simplified BSD License 622 set forth in Section 4.c of the IETF Trust's Legal Provisions 623 Relating to IETF Documents 624 (http://trustee.ietf.org/license-info). 626 This version of this YANG module is part of RFC XXXX; see 627 the RFC itself for full legal notices."; 629 revision 2020-03-19 { 630 description 631 "Initial revision."; 632 reference 633 "RFC XXXX: YANG Instance Data Format"; 634 } 635 feature inline-content-schema { 636 description 637 "This feature indicates that inline content-schema 638 option is supported."; 639 } 641 sx:structure "instance-data-set" { 642 description 643 "A data structure to define a format for 644 YANG instance data sets. Consists of meta-data about 645 the instance data set and the real content-data."; 646 leaf name { 647 type string; 648 description 649 "An arbitrary name for the YANG instance data set. This 650 value is primarily used for descriptive purposes. However, 651 when the instance data set is saved to a file, then the 652 filename MUST encode the name's value, per Section 3 653 of RFC XXXX."; 654 } 655 leaf format-version { 656 type string { 657 pattern '\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1])'; 658 } 659 default "2020-03-19"; 660 description 661 "Version of the 'YANG Instance Data format'. 663 It SHALL contain the revision date of the 664 ietf-yang-instance-data module used when creating the 665 instance data set in a YYYY-MM-DD format"; 666 } 667 container content-schema { 668 description 669 "The content schema used to create the instance data set. 670 If not present the user needs to obtain the information 671 through external documents."; 672 choice content-schema-spec { 673 description 674 "Specification of the content-schema."; 675 case simplified-inline { 676 leaf-list module { 677 type string; 678 description 679 "The list of content defining YANG modules. 681 The value SHALL start with the module name. 682 If the module contains a revision statement the 683 revision date SHALL be included in the leaf-list 684 entry. If other methods (e.g., revision-label) are 685 defined to identify individual module revisions 686 those MAY be used instead of using a revision date. 688 E.g., ietf-yang-library@2016-06-21 690 Usage of this leaf-list implies the modules are 691 used without any deviations and with all features 692 supported. Multiple revisions of the same module 693 MUST NOT be specified."; 694 } 695 } 696 case inline { 697 if-feature "inline-content-schema"; 698 leaf-list inline-module { 699 type string; 700 min-elements 1; 701 ordered-by user; 702 description 703 "Indicates that content defining YANG modules 704 are specified inline. 706 The value SHALL start with the module name. 707 If the module contains a revision statement the 708 revision date SHALL be included in the leaf-list 709 entry. If other methods (e.g., revision-label) are 710 defined to identify individual module revisions 711 those MAY be used instead of using a revision date. 713 E.g., ietf-yang-library@2016-06-21 715 The first item is either ietf-yang-library or some 716 other YANG module that contains a list of YANG modules 717 with their name, revision-date, supported-features, 718 and deviations. The usage of 719 ietf-yang-library@2019-01-04 MUST be supported. 720 Using other modules, module versions MAY also be 721 supported. 723 As some versions of ietf-yang-library MAY contain 724 different module-sets for different datastores, if 725 multiple module-sets are included, the instance data 726 set's meta-data MUST contain the datastore information 727 and instance data for the ietf-yang-library MUST also 728 contain information specifying the module-set for the 729 relevant datastore. 731 Subsequent items MAY specify YANG modules augmenting 732 the first module with useful data 733 (e.g., revision label)."; 734 } 735 anydata inline-schema { 736 mandatory true; 737 description 738 "Instance data corresponding to the YANG modules 739 specified in the inline-module nodes defining the set 740 of content defining YANG modules for this 741 instance-data-set."; 742 } 743 } 744 case uri { 745 leaf same-schema-as-file { 746 type inet:uri; 747 description 748 "A reference to another YANG instance data file. 749 This instance data file uses the same 750 content schema as the referenced file."; 751 } 752 } 753 } 754 } 755 leaf-list description { 756 type string; 757 description 758 "Description of the instance data set."; 759 } 760 leaf contact { 761 type string; 762 description 763 "Contact information for the person or 764 organization to whom queries concerning this 765 instance data set should be sent."; 766 } 767 leaf organization { 768 type string; 769 description 770 "Organization responsible for the instance 771 data set."; 772 } 773 leaf datastore { 774 type ds:datastore-ref; 775 description 776 "The identity of the datastore with which the 777 instance data set is associated, e.g., the datastore from 778 where the data was read or the datastore into which the data 779 may be loaded or the datastore which is being documented. 780 If a single specific datastore cannot be specified, the 781 leaf MUST be absent. 783 If this leaf is absent, then the datastore to which the 784 instance data belongs is undefined."; 785 } 786 list revision { 787 key "date"; 788 description 789 "Instance data sets that are produced as 790 a result of some sort of specification or design effort 791 SHOULD have at least one revision entry. For every 792 published editorial change, a new one SHOULD be added 793 in front of the revisions sequence so that all 794 revisions are in reverse chronological order. 796 For instance data sets that are read from 797 or produced by a server or otherwise 798 subject to frequent updates or changes, revision 799 SHOULD NOT be present"; 800 leaf date { 801 type string { 802 pattern '\d{4}-(1[0-2]|0[1-9])-(0[1-9]|[1|2][0-9]|3[0-1])'; 803 } 804 description 805 "Specifies the date the instance data set 806 was last modified. Formatted as YYYY-MM-DD"; 807 } 808 leaf description { 809 type string; 810 description 811 "Description of this revision of the instance data set."; 812 } 813 } 814 leaf timestamp { 815 type yang:date-and-time; 816 description 817 "The date and time when the instance data set 818 was last modified. 820 For instance data sets that are read from or produced 821 by a server or otherwise subject to frequent 822 updates or changes, timestamp SHOULD be present"; 823 } 824 anydata content-data { 825 description 826 "Contains the real instance data. 828 The data MUST conform to the relevant YANG Modules specified 829 either in the content-schema-spec or in some other 830 implementation specific manner."; 831 } 832 } 833 } 834 836 5. Security Considerations 838 The YANG module defined in this document is designed as a wrapper 839 specifying a format and a metadata header for YANG instance data 840 defined by the content-schema. The data is designed to be accessed 841 as a stored file or over any file access method or protocol. 843 The document does not specify any method to influence the behavior of 844 a server. 846 Instance data files may contain sensitive data. 848 The header part is not security sensitive. 850 The security sensitivity of the instance data in the content part is 851 completely dependent on the content schema. Depending on the nature 852 of the instance data, instance data files MAY need to be handled in a 853 secure way. The same kind of handling should be applied, that would 854 be needed for the result of a read operation returning the same data. 856 Instance data files should be protected against modification or 857 unauthorized access using normal file handling mechanisms. Care 858 should be taken, when copying the original files or providing file 859 access for additional users, not to reveal information 860 unintentionally. 862 6. IANA Considerations 864 This document registers one URI and one YANG module. 866 6.1. URI Registration 868 This document registers one URI in the IETF XML registry [RFC3688]. 869 Following the format in RFC 3688, the following registration is 870 requested to be made: 872 URI: urn:ietf:params:xml:ns:yang:ietf-yang-instance-data 874 Registrant Contact: The IESG. 876 XML: N/A, the requested URI is an XML namespace. 878 6.2. YANG Module Name Registration 880 This document registers one YANG module in the YANG Module Names 881 registry [RFC6020]. 883 name: ietf-yang-instance-data 884 namespace: urn:ietf:params:xml:ns:yang:ietf-yang-instance-data 885 prefix: yid 886 reference: RFC XXXX 888 7. Acknowledgments 890 For their valuable comments, discussions, and feedback, we wish to 891 acknowledge Andy Bierman, Juergen Schoenwaelder, Rob Wilton, Joe 892 Clarke, Kent Watsen Martin Bjorklund, Ladislav Lhotka, Qin Wu and 893 other members of the Netmod WG. 895 8. References 897 8.1. Normative References 899 [I-D.ietf-netmod-yang-data-ext] 900 Bierman, A., Bjorklund, M., and K. Watsen, "YANG Data 901 Structure Extensions", draft-ietf-netmod-yang-data-ext-05 902 (work in progress), December 2019. 904 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 905 Requirement Levels", BCP 14, RFC 2119, 906 DOI 10.17487/RFC2119, March 1997, 907 . 909 [RFC6243] Bierman, A. and B. Lengyel, "With-defaults Capability for 910 NETCONF", RFC 6243, DOI 10.17487/RFC6243, June 2011, 911 . 913 [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", 914 RFC 6991, DOI 10.17487/RFC6991, July 2013, 915 . 917 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", 918 RFC 7950, DOI 10.17487/RFC7950, August 2016, 919 . 921 [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", 922 RFC 7951, DOI 10.17487/RFC7951, August 2016, 923 . 925 [RFC7952] Lhotka, L., "Defining and Using Metadata with YANG", 926 RFC 7952, DOI 10.17487/RFC7952, August 2016, 927 . 929 [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF 930 Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, 931 . 933 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 934 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 935 May 2017, . 937 [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", 938 BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, 939 . 941 [RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., 942 and R. Wilton, "Network Management Datastore Architecture 943 (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018, 944 . 946 [RFC8525] Bierman, A., Bjorklund, M., Schoenwaelder, J., Watsen, K., 947 and R. Wilton, "YANG Library", RFC 8525, 948 DOI 10.17487/RFC8525, March 2019, 949 . 951 [RFC8526] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., 952 and R. Wilton, "NETCONF Extensions to Support the Network 953 Management Datastore Architecture", RFC 8526, 954 DOI 10.17487/RFC8526, March 2019, 955 . 957 [RFC8527] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., 958 and R. Wilton, "RESTCONF Extensions to Support the Network 959 Management Datastore Architecture", RFC 8527, 960 DOI 10.17487/RFC8527, March 2019, 961 . 963 8.2. Informative References 965 [I-D.ietf-netmod-artwork-folding] 966 Watsen, K., Auerswald, E., Farrel, A., and Q. WU, 967 "Handling Long Lines in Inclusions in Internet-Drafts and 968 RFCs", draft-ietf-netmod-artwork-folding-12 (work in 969 progress), January 2020. 971 [I-D.ietf-netmod-factory-default] 972 WU, Q., Lengyel, B., and Y. Niu, "A YANG Data Model for 973 Factory Default Settings", draft-ietf-netmod-factory- 974 default-14 (work in progress), February 2020. 976 [I-D.verdt-netmod-yang-module-versioning] 977 Claise, B., Clarke, J., Rahman, R., Wilton, R., Lengyel, 978 B., Sterne, J., and K. D'Souza, "Updated YANG Module 979 Revision Handling", draft-verdt-netmod-yang-module- 980 versioning-01 (work in progress), October 2019. 982 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, 983 DOI 10.17487/RFC3688, January 2004, 984 . 986 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for 987 the Network Configuration Protocol (NETCONF)", RFC 6020, 988 DOI 10.17487/RFC6020, October 2010, 989 . 991 [RFC8632] Vallin, S. and M. Bjorklund, "A YANG Data Model for Alarm 992 Management", RFC 8632, DOI 10.17487/RFC8632, September 993 2019, . 995 [RFC8641] Clemm, A. and E. Voit, "Subscription to YANG Notifications 996 for Datastore Updates", RFC 8641, DOI 10.17487/RFC8641, 997 September 2019, . 999 Appendix A. Changes between revisions 1001 Note to RFC Editor (To be removed by RFC Editor) 1003 v09 - v10 1005 o Editorial updates 1007 v08 - v09 1009 o Removed reference to similar to get reply 1011 o Introduced artwork folding in the examples 1013 v07 - v08 1015 o Moved compatibility into appendix 1017 o Renamed yid-version to format-version. Changed format to date of 1018 the YANG module 1020 o Made support of ietf-yang-library mandatory if inline-content- 1021 schema is supported 1023 o Many small changes based on WGLC 1025 v06 - v07 1027 o Updated terminology, use-cases 1029 o Many small changes based on WGLC 1031 v05 - v06 1033 o Modified module name format, removed .yin or .yang extension 1035 o Removed pattern for module and inline-module. We want to allow 1036 the usage of revision-label later 1038 v04 - v05 1040 o Updated according to YANG-Doctor review 1042 o Updated security considerations 1044 o Added a wrapping container for the schema, and renamed the data 1045 nodes in the inline and uri cases. 1047 o Allowed .yin for simplified-inline schema naming. Made date 1048 optional if it is not available in the YANG module. 1050 o Added a mandatory yid-version to the header metadata to allow 1051 later updates of the module. 1053 v03 - v04 1055 o removed entity-tag and last-modified timestamp 1057 o Added simplified-inline method of content-schema specification 1059 v02 - v03 1061 o target renamed to "content-schema" and "content defining YANG 1062 module(s)" 1064 o Made name of instance data set optional 1066 o Updated according to draft-ietf-netmod-yang-data-ext-03 1067 o Clarified that entity-tag and last-modified timestamp are encoded 1068 as metadata. While they contain useful data, the HTTP-header 1069 based encoding from Restconf is not suitable. 1071 v01 - v02 1073 o Removed design time from terminology 1075 o Defined the format of the content-data part by referencing various 1076 RFCs and drafts instead of the result of the get-data and get 1077 operations. 1079 o Changed target-ptr to a choice 1081 o Inline target-ptr may include augmenting modules and alternatives 1082 to ietf-yang-library 1084 o Moved list of target modules into a separate 1085 element. 1087 o Added backwards compatibility considerations 1089 v00 - v01 1091 o Added the target-ptr metadata with 3 methods 1093 o Added timestamp metadata 1095 o Removed usage of dedicated .yid file extension 1097 o Added list of use cases 1099 o Added list of principles 1101 o Updated examples 1103 o Moved detailed use case descriptions to appendix 1105 Appendix B. Backwards Compatibility 1107 The concept of backwards compatibility and what changes are backwards 1108 compatible are not defined for instance data sets as it is highly 1109 dependent on the specific use case and the content-schema. 1111 For instance data that is the result of a design or specification 1112 activity, some changes that may be good to avoid are listed. YANG 1113 uses the concept of managed entities identified by key values; if the 1114 connection between the represented entity and the key value is not 1115 preserved during an update, this may lead to problems. 1117 o If the key value of a list entry that represents the same managed 1118 entity as before is changed, the user may mistakenly identify the 1119 list entry as new. 1121 o If the meaning of a list entry is changed, but the key values are 1122 not (e.g., redefining an alarm-type but not changing its alarm- 1123 type-id) the change may not be noticed. 1125 o If the key value of a previously removed list entry is reused for 1126 a different entity, the change may be misinterpreted as 1127 reintroducing the previous entity. 1129 Appendix C. Detailed Use Cases - Non-Normative 1131 C.1. Use Cases 1133 We present a number of use cases were YANG instance data is needed. 1135 C.1.1. Use Case 1: Early Documentation of Server Capabilities 1137 A server has a number of server-capabilities that are defined in YANG 1138 modules and can be retrieved from the server using protocols like 1139 NETCONF or RESTCONF. Server capabilities include: 1141 o data defined in ietf-yang-library: YANG modules, submodules, 1142 features, deviations, schema-mounts, and datastores supported 1143 ([RFC8525]) 1145 o alarms supported ([RFC8632]) 1147 o data nodes and subtrees that support or do not support on-change 1148 notifications ([RFC8641]) 1150 o netconf-capabilities in ietf-netconf-monitoring 1152 While it is good practice to allow a client to query these 1153 capabilities from the live server, that is often not possible. 1155 Often when a network node is released, an associated NMS (network 1156 management system) is also released with it. The NMS depends on the 1157 capabilities of the server. During NMS implementation, information 1158 about server capabilities is needed. If the information is not 1159 available early in some offline document, but only as instance data 1160 from the live network node, the NMS implementation will be delayed, 1161 because it has to wait until the network node is ready. Also 1162 assuming that all NMS implementors will have a correctly configured 1163 network nodes from which data can be retrieved, is a very expensive 1164 proposition. (An NMS may handle dozens of node types.) 1166 Network operators often build their own home-grown NMS systems that 1167 need to be integrated with a vendor's network node. The operator 1168 needs to know the network node's server capabilities in order to do 1169 this. Moreover, the network operator's decision to buy a vendor's 1170 product may even be influenced by the network node's OAM feature set 1171 documented as the server's capabilities. 1173 Beside NMS implementors, system integrators and many others also need 1174 the same information early. Examples could be model driven testing, 1175 generating documentation, etc. 1177 Most server-capabilities are relatively stable and change only during 1178 upgrade or due to licensing or the addition or removal of hardware. 1179 They are usually defined by a vendor at design time, before the 1180 product is released. It is feasible and advantageous to define/ 1181 document them early e.g., in a YANG instance data File. 1183 It is anticipated that a separate IETF document will define in detail 1184 how and which set of server capabilities should be documented. 1186 C.1.2. Use Case 2: Preloading Data 1188 There are parts of the configuration that must be fully configurable 1189 by the operator. However, often a simple default configuration will 1190 be sufficient. 1192 One example is access control groups/roles and related rules. While 1193 a sophisticated operator may define dozens of different groups, often 1194 a basic (read-only operator, read-write system administrator, 1195 security-administrator) triplet will be enough. Vendors will often 1196 provide such default configuration data to make device configuration 1197 easier for an operator. 1199 Defining access control data is a complex task. To help, the device 1200 vendor predefines a set of default groups (/nacm:nacm/groups) and 1201 rules for these groups to access specific parts of common models 1202 (/nacm:nacm/rule-list/rule). 1204 YANG instance data files are used to document and/or preload the 1205 default configuration. 1207 C.1.3. Use Case 3: Documenting Factory Default Settings 1209 Nearly every server has a factory default configuration. If the 1210 system is really badly misconfigured or if the current configuration 1211 is to be abandoned, the system can be reset the default factory 1212 configuration. 1214 In NETCONF, the operation can already be used to 1215 reset the startup datastore. There are ongoing efforts to introduce 1216 a new, more generic factory-reset operation for the same purpose 1217 [I-D.ietf-netmod-factory-default] 1219 The operator currently has no way to know what the default 1220 configuration actually contains. YANG instance data can also be used 1221 to document the factory default configuration. 1223 Authors' Addresses 1225 Balazs Lengyel 1226 Ericsson 1227 Magyar Tudosok korutja 11 1228 1117 Budapest 1229 Hungary 1231 Phone: +36-70-330-7909 1232 Email: balazs.lengyel@ericsson.com 1234 Benoit Claise 1235 Cisco Systems, Inc. 1236 De Kleetlaan 6a b1 1237 1831 Diegem 1238 Belgium 1240 Phone: +32 2 704 5622 1241 Email: bclaise@cisco.com