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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) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Clemm 3 Internet-Draft Y. Qu 4 Intended status: Standards Track Futurewei 5 Expires: January 14, 2021 J. Tantsura 6 Apstra 7 A. Bierman 8 YumaWorks 9 July 13, 2020 11 Comparison of NMDA datastores 12 draft-ietf-netmod-nmda-diff-04 14 Abstract 16 This document defines an RPC operation to compare management 17 datastores that comply with the NMDA architecture. 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 14, 2021. 36 Copyright Notice 38 Copyright (c) 2020 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 2. Key Words . . . . . . . . . . . . . . . . . . . . . . . . . . 3 55 3. Definitions and Acronyms . . . . . . . . . . . . . . . . . . 3 56 4. Data Model Overview . . . . . . . . . . . . . . . . . . . . . 4 57 5. YANG Data Model . . . . . . . . . . . . . . . . . . . . . . . 6 58 6. Example . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 59 7. Performance Considerations . . . . . . . . . . . . . . . . . 13 60 8. Possible Future Extensions . . . . . . . . . . . . . . . . . 14 61 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 62 9.1. Updates to the IETF XML Registry . . . . . . . . . . . . 14 63 9.2. Updates to the YANG Module Names Registry . . . . . . . . 15 64 10. Security Considerations . . . . . . . . . . . . . . . . . . . 15 65 11. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16 66 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 16 67 12.1. Normative References . . . . . . . . . . . . . . . . . . 16 68 12.2. Informative References . . . . . . . . . . . . . . . . . 17 69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 71 1. Introduction 73 The revised Network Management Datastore Architecture (NMDA) 74 [RFC8342] introduces a set of new datastores that each hold YANG- 75 defined data [RFC7950] and represent a different "viewpoint" on the 76 data that is maintained by a server. New YANG datastores that are 77 introduced include , which contains validated configuration 78 data that a client application intends to be in effect, and 79 , which contains at least conceptually operational state 80 data (such as statistics) as well as configuration data that is 81 actually in effect. 83 NMDA introduces in effect a concept of "lifecycle" for management 84 data, allowing to clearly distinguish between data that is part of a 85 configuration that was supplied by a user, configuration data that 86 has actually been successfully applied and that is part of the 87 operational state, and overall operational state that includes both 88 applied configuration data as well as status and statistics. 90 As a result, data from the same management model can be reflected in 91 multiple datastores. Clients need to specify the target datastore to 92 be specific about which viewpoint of the data they want to access. 93 This way, an application can differentiate whether they are (for 94 example) interested in the configuration that has been applied and is 95 actually in effect, or in the configuration that was supplied by a 96 client and that is supposed to be in effect. 98 Due to the fact that data can propagate from one datastore to 99 another, it is possibly for differences between datastores to occur. 100 Some of this is entirely expected, as there may be a time lag between 101 when a configuration is given to the device and reflected in 102 , until when it actually takes effect and is reflected in 103 . However, there may be cases when a configuration item 104 that was to be applied may not actually take effect at all or needs 105 an unusually long time to do so. This can be the case due to certain 106 conditions not being met, resource dependencies not being resolved, 107 or even implementation errors in corner conditions. 109 When configuration that is in effect is different from configuration 110 that was applied, many issues can result. It becomes more difficult 111 to operate the network properly due to limited visibility of actual 112 status which makes it more difficult to analyze and understand what 113 is going on in the network. Services may be negatively affected (for 114 example, breaking a service instance resulting in service is not 115 properly delivered to a customer) and network resources be 116 misallocated. 118 Applications can potentially analyze any differences between two 119 datastores by retrieving the contents from both datastores and 120 comparing them. However, in many cases this will be at the same time 121 costly and extremely wasteful. 123 This document introduces a YANG data model which defines RPCs, 124 intended to be used in conjunction with NETCONF [RFC6241] or RESTCONF 125 [RFC8040], that allow a client to request a server to compare two 126 NMDA datastores and report any differences. 128 2. Key Words 130 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 131 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 132 "OPTIONAL" in this document are to be interpreted as described in BCP 133 14 [RFC2119] [RFC8174] when, and only when, they appear in all 134 capitals, as shown here. 136 3. Definitions and Acronyms 138 NMDA: Network Management Datastore Architecture 140 RPC: Remote Procedure Call 142 4. Data Model Overview 144 At the core of the solution is a new management operation, , 145 that allows to compare two datastores for the same data. The 146 operation checks whether there are any differences in values or in 147 data nodes that are contained in either datastore, and returns any 148 differences as output. The output is returned in the format 149 specified in YANG-Patch [RFC8072]. 151 The YANG data model defines the operation as a new RPC. 152 The operation takes the following input parameters: 154 o source: The source identifies the datastore that will serve as 155 reference for the comparison, for example . 157 o target: The target identifies the datastore to compare against the 158 source. 160 o filter-spec: This is a choice between different filter constructs 161 to identify the portions of the datastore to be retrieved. It 162 acts as a node selector that specifies which data nodes are within 163 the scope of the comparison and which nodes are outside the scope. 164 This allows a comparison operation to be applied only to a 165 specific portion of the datastore that is of interest, such as a 166 particular subtree. (The filter dow not contain expressions that 167 would match values data nodes, as this is not required by most use 168 cases and would complicate the scheme, from implementation to 169 dealing with race conditions.) 171 o all: When set, this parameter indicates that all differences 172 should be included, including differences pertaining to schema 173 nodes that exist in only one of the datastores. When this 174 parameter is not included, a prefiltering step is automatically 175 applied to exclude data from the comparison that does not pertain 176 to both datastores: if the same schema node is not present in both 177 datastores, then all instances of that schema node and all its 178 descendants are excluded from the comparison. This allows client 179 applications to focus on the differences that constitute true 180 mismatches of instance data without needing to specify more 181 complex filter constructs. 183 o exclude-origin: When set, this parameter indicates that origin 184 metadata should not not be included as part of RPC output. When 185 this parameter is omitted, origin metadata in comparisons that 186 involve is by default included. 188 The operation provides the following output parameter: 190 o differences: This parameter contains the list of differences. 191 Those differences are encoded per YANG-Patch data model defined in 192 RFC8072. The YANG-Patch data model is augmented to indicate the 193 value of source datastore nodes in addition to the patch itself 194 that would need to be applied to the source to produce the target. 195 When the target datastore is , "origin" metadata is 196 included as part of the patch. Including origin metadata can help 197 in some cases explain the cause of a difference, for example when 198 a data node is part of but the origin of the same data 199 node in is reported as "system". 201 The data model is defined in the ietf-nmda-compare YANG module. Its 202 structure is shown in the following figure. The notation syntax 203 follows [RFC8340]. 205 module: ietf-nmda-compare 206 rpcs: 207 +---x compare 208 +---w input 209 | +---w source identityref 210 | +---w target identityref 211 | +---w all? empty 212 | +---w exclude-origin? empty 213 | +---w (filter-spec)? 214 | +--:(subtree-filter) 215 | | +---w subtree-filter? 216 | +--:(xpath-filter) 217 | +---w xpath-filter? yang:xpath1.0 {nc:xpath}? 218 +--ro output 219 +--ro (compare-response)? 220 +--:(no-matches) 221 | +--ro no-matches? empty 222 +--:(differences) 223 +--ro differences 224 +--ro yang-patch 225 +--ro patch-id string 226 +--ro comment? string 227 +--ro edit* [edit-id] 228 +--ro edit-id string 229 +--ro operation enumeration 230 +--ro target target-resource-offset 231 +--ro point? target-resource-offset 232 +--ro where? enumeration 233 +--ro value? 234 +--ro source-value? 236 Structure of ietf-nmda-compare 238 5. YANG Data Model 240 file "ietf-nmda-compare@2019-11-04.yang" 241 module ietf-nmda-compare { 243 yang-version 1.1; 244 namespace "urn:ietf:params:xml:ns:yang:ietf-nmda-compare"; 246 prefix cp; 248 import ietf-yang-types { 249 prefix yang; 250 } 251 import ietf-datastores { 252 prefix ds; 253 } 254 import ietf-yang-patch { 255 prefix ypatch; 256 } 257 import ietf-netconf { 258 prefix nc; 259 } 261 organization "IETF"; 262 contact 263 "WG Web: 264 WG List: 266 Author: Alexander Clemm 267 269 Author: Yingzhen Qu 270 272 Author: Jeff Tantsura 273 275 Author: Andy Bierman 276 "; 278 description 279 "The YANG data model defines a new operation, , that 280 can be used to compare NMDA datastores. 282 The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL 283 NOT', 'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'NOT RECOMMENDED', 284 'MAY', and 'OPTIONAL' in this document are to be interpreted as 285 described in BCP 14 (RFC 2119) (RFC 8174) when, and only when, 286 they appear in all capitals, as shown here. 288 Copyright (c) 2019 IETF Trust and the persons identified as 289 authors of the code. All rights reserved. 291 Redistribution and use in source and binary forms, with or 292 without modification, is permitted pursuant to, and subject to 293 the license terms contained in, the Simplified BSD License set 294 forth in Section 4.c of the IETF Trust's Legal Provisions 295 Relating to IETF Documents 296 (https://trustee.ietf.org/license-info). 298 This version of this YANG module is part of RFC XXXX; see the 299 RFC itself for full legal notices."; 301 revision 2019-11-04 { 302 description 303 "Initial revision"; 304 reference 305 "RFC XXXX: Comparison of NMDA datastores"; 306 } 308 /* RPC */ 309 rpc compare { 310 description 311 "NMDA compare operation."; 312 input { 313 leaf source { 314 type identityref { 315 base ds:datastore; 316 } 317 mandatory true; 318 description 319 "The source datastore to be compared."; 320 } 321 leaf target { 322 type identityref { 323 base ds:datastore; 324 } 325 mandatory true; 326 description 327 "The target datastore to be compared."; 328 } 329 leaf all { 330 type empty; 331 description 332 "When this leaf is provided, all data nodes are compared, 333 whether their schema node pertains to both datastores or 334 not. When this leaf is omitted, a prefiltering step is 335 automatically applied that excludes data nodes from the 336 comparison that can occur in only one datastore but not 337 the other. Specifically, if one of the datastores 338 (source or target) contains only configuration data and 339 the other datastore is , data nodes for 340 which config is false are excluded from the comparison."; 341 } 342 leaf exclude-origin { 343 type empty; 344 description 345 "When this leaf is provided, origin metadata is not 346 included as part of RPC output. When this leaf is 347 omitted, origin metadata in comparisons that involve 348 is by default included."; 349 } 350 choice filter-spec { 351 description 352 "Identifies the portions of the datastores to be 353 compared."; 354 anydata subtree-filter { 355 description 356 "This parameter identifies the portions of the 357 target datastore to retrieve."; 358 reference "RFC 6241, Section 6."; 359 } 360 leaf xpath-filter { 361 if-feature nc:xpath; 362 type yang:xpath1.0; 363 description 364 "This parameter contains an XPath expression 365 identifying the portions of the target 366 datastore to retrieve."; 367 } 368 } 369 } 370 output { 371 choice compare-response { 372 description 373 "Comparison results."; 374 leaf no-matches { 375 type empty; 376 description 377 "This leaf indicates that the filter did not match 378 anything and nothing was compared."; 379 } 380 container differences { 381 description 382 "The list of differences, encoded per RFC8072 with an 383 augmentation to include source values where 384 applicable."; 385 uses ypatch:yang-patch { 386 augment "yang-patch/edit" { 387 description 388 "Provide the value of the source of the patch, 389 respectively of the comparison, in addition to 390 the target value, where applicable."; 391 anydata source-value { 392 when "../operation = 'delete'" 393 + "or ../operation = 'merge'" 394 + "or ../operation = 'move'" 395 + "or ../operation = 'replace'" 396 + "or ../operation = 'remove'"; 397 description 398 "The anydata 'value' is only used for 'delete', 399 'move', 'merge', 'replace', and 'remove' 400 operations."; 401 } 402 } 403 } 404 } 405 } 406 } 407 } 408 } 409 411 6. Example 413 The following example compares the difference between 414 and for a subtree under "interfaces". The subtree 415 contains objects that are defined in a YANG data model for the 416 management of interfaces defined in [RFC8343]. The excerpt of the 417 data model whose instantiation is basis of the comparison is as 418 follows: 420 container interfaces { 421 description 422 "Interface parameters."; 423 list interface { 424 key "name"; 425 leaf name { 426 type string; 427 description 428 "The name of the interface". 429 } 430 leaf description { 431 type string; 432 description 433 "A textual description of the interface."; 434 } 435 leaf enabled { 436 type boolean; 437 default "true"; 438 description 439 "This leaf contains the configured, desired state of the 440 interface.";" 441 } 442 } 443 } 445 The contents of and datastores: 447 449 450 eth0 451 false 452 ip interface 453 454 457 458 eth0 459 true 460 461 463 contains one object that was not contained in 464 , "preference". Another object, "explicit-router-id", has 465 differences in values. A third object, "enable", is the same in both 466 cases. 468 RPC request to compare (target of the comparison): 471 473 475 ds:operational 476 ds:intended 477 \ 479 /if:interfaces\ 480 481 482 484 RPC reply, when a difference is detected: 486 489 492 493 interface status 494 diff between operational and intended 495 496 1 497 replace 498 /ietf-interfaces:interface=eth0/enabled 499 500 true 502 503 504 false 506 507 2 508 create 509 /ietf-interfaces:interface=eth0/description 510 511 ip interface 513 514 515 516 517 519 The same request in RESTCONF (using JSON format): 521 POST /restconf/operations/ietf-nmda-compare:compare HTTP/1.1 522 Host: example.com 523 Content-Type: application/yang-data+json 524 Accept: application/yang-d 525 { "ietf-nmda-compare:input" { 526 "source" : "ietf-datastores:operational", 527 "target" : "ietf-datastores:intended". 528 "xpath-filter" : \ 529 "/ietf-interfaces:interfaces" 530 } 531 } 533 The same response in RESTCONF (using JSON format): 535 HTTP/1.1 200 OK 536 Date: Thu, 26 Jan 2019 20:56:30 GMT 537 Server: example-server 538 Content-Type: application/yang-d 539 { "ietf-nmda-compare:output" : { 540 "differences" : { 541 "ietf-yang-patch:yang-patch" : { 542 "patch-id" : "interface status", 543 "comment" : "diff between operational and intended", 544 "edit" : [ 545 { 546 "edit-id" : "1", 547 "operation" : "replace", 548 "target" : "/ietf-interfaces:interface=eth0/enabled", 549 "value" : { 550 "ietf-interfaces:interface/enabled" : "true" 551 "@ietf-interfaces:interface/enabled" : { 552 "ietf-origin:origin" : "ietf-origin:system" 553 } 554 "source-value" : { 555 "ietf-interfaces:interface/enabled" : "false" 556 "@ietf-interfaces:interface/enabled" : { 557 "ietf-origin:origin" : "ietf-origin:intended" 558 } 559 "edit-id" : "2", 560 "operation" : "create", 561 "target" : "/ietf-interfaces:interface=eth0/description", 562 "value" : { 563 "ietf-interface:interface/description" : "ip interface" 564 "@ietf-interface:interfaces/description" : { 565 "ietf-origin:origin" : "ietf-origin:intended" 566 } 567 } 568 ] 569 } 570 } 571 } 572 } 574 7. Performance Considerations 576 The compare operation can be computationally expensive. While 577 responsible client applications are expected to use the operation 578 responsibly and sparingly only when warranted, implementations need 579 to be aware of the fact that excessive invocation of this operation 580 will burden system resources and need to ensure that system 581 performance will not be adversely impacted. One possibility for an 582 implementation to mitigate against such a possibility is to limit the 583 number of requests that is served to a client in any one time 584 interval, rejecting requests made at a higher frequency than the 585 implementation can reasonably sustain. 587 8. Possible Future Extensions 589 It is conceivable to extend the compare operation with a number of 590 possible additional features in the future. 592 Specifically, it is possible to define an extension with an optional 593 feature for dampening. This will allow clients to specify a minimum 594 time period for which a difference must persist for it to be 595 reported. This will enable clients to distinguish between 596 differences that are only fleeting from ones that are not and that 597 may represent a real operational issue and inconsistency within the 598 device. 600 For this purpose, an additional input parameter can be added to 601 specify the dampening period. Only differences that pertain for at 602 least the dampening time are reported. A value of 0 or omission of 603 the parameter indicates no dampening. Reporting of differences MAY 604 correspondingly be delayed by the dampening period from the time the 605 request is received. 607 To implement this feature, a server implementation might run a 608 comparison when the RPC is first invoked and temporarily store the 609 result. Subsequently, it could wait until after the end of the 610 dampening period to check whether the same differences are still 611 observed. The differences that still persist are then returned. 613 9. IANA Considerations 615 9.1. Updates to the IETF XML Registry 617 This document registers one URI in the IETF XML registry [RFC3688]. 618 Following the format in [RFC3688], the following registration is 619 requested: 621 URI: urn:ietf:params:xml:ns:yang:ietf-nmda-compare 623 Registrant Contact: The IESG. 625 XML: N/A, the requested URI is an XML namespace. 627 9.2. Updates to the YANG Module Names Registry 629 This document registers a YANG module in the YANG Module Names 630 registry [RFC7950]. Following the format in [RFC7950], the following 631 registration is requested: 633 name: ietf-nmda-compare 635 namespace: urn:ietf:params:xml:ns:yang:ietf-nmda-compare 637 prefix: cp 639 reference: RFC XXXX 641 10. Security Considerations 643 The YANG module specified in this document defines a schema for data 644 that is designed to be accessed via network management protocols such 645 as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer 646 is the secure transport layer, and the mandatory-to-implement secure 647 transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer 648 is HTTPS, and the mandatory-to-implement secure transport is TLS 649 [RFC8446]. 651 The NETCONF access control model [RFC8341] provides the means to 652 restrict access for particular NETCONF or RESTCONF users to a 653 preconfigured subset of all available NETCONF or RESTCONF protocol 654 operations and content. 656 The RPC operation defined in this YANG module, "compare", may be 657 considered sensitive or vulnerable in some network environments. It 658 is thus important to control access to this operation. This is the 659 sensitivity/vulnerability of RPC operation "compare": 661 Comparing datastores for differences requires a certain amount of 662 processing resources at the server. An attacker could attempt to 663 attack a server by making a high volume of comparison requests. 664 Server implementations can guard against such scenarios in several 665 ways. For one, they can implement the NETCONF access control model 666 in order to require proper authorization for requests to be made. 667 Second, server implementations can limit the number of requests that 668 they serve to a client in any one time interval, rejecting requests 669 made at a higher frequency than the implementation can reasonably 670 sustain. 672 11. Acknowledgments 674 We thank Rob Wilton, Martin Bjorklund, Mahesh Jethanandani, Lou 675 Berger, Kent Watsen, Phil Shafer, Ladislav Lhotka, and Tim Carey for 676 valuable feedback and suggestions. 678 12. References 680 12.1. Normative References 682 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 683 Requirement Levels", BCP 14, RFC 2119, 684 DOI 10.17487/RFC2119, March 1997, 685 . 687 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, 688 DOI 10.17487/RFC3688, January 2004, 689 . 691 [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., 692 and A. Bierman, Ed., "Network Configuration Protocol 693 (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, 694 . 696 [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure 697 Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, 698 . 700 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", 701 RFC 7950, DOI 10.17487/RFC7950, August 2016, 702 . 704 [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF 705 Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, 706 . 708 [RFC8072] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Patch 709 Media Type", RFC 8072, DOI 10.17487/RFC8072, February 710 2017, . 712 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 713 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 714 May 2017, . 716 [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", 717 BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, 718 . 720 [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration 721 Access Control Model", STD 91, RFC 8341, 722 DOI 10.17487/RFC8341, March 2018, 723 . 725 [RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., 726 and R. Wilton, "Network Management Datastore Architecture 727 (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018, 728 . 730 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 731 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 732 . 734 12.2. Informative References 736 [RFC8343] Bjorklund, M., "A YANG Data Model for Interface 737 Management", RFC 8343, DOI 10.17487/RFC8343, March 2018, 738 . 740 Authors' Addresses 742 Alexander Clemm 743 Futurewei 744 2330 Central Expressway 745 Santa Clara, CA 95050 746 USA 748 Email: ludwig@clemm.org 750 Yingzhen Qu 751 Futurewei 752 2330 Central Expressway 753 Santa Clara, CA 95050 754 USA 756 Email: yqu@futurewei.com 758 Jeff Tantsura 759 Apstra 761 Email: jefftant.ietf@gmail.com 762 Andy Bierman 763 YumaWorks 765 Email: andy@yumaworks.com