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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force M. Veillette, Ed. 3 Internet-Draft Trilliant Networks Inc. 4 Intended status: Standards Track A. Pelov, Ed. 5 Expires: August 11, 2018 Acklio 6 A. Somaraju 7 Tridonic GmbH & Co KG 8 R. Turner 9 Landis+Gyr 10 A. Minaburo 11 Acklio 12 February 07, 2018 14 CBOR Encoding of Data Modeled with YANG 15 draft-ietf-core-yang-cbor-06 17 Abstract 19 This document defines encoding rules for serializing configuration 20 data, state data, RPC input and RPC output, Action input, Action 21 output and notifications defined within YANG modules using the 22 Concise Binary Object Representation (CBOR) [RFC7049]. 24 Status of This Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF). Note that other groups may also distribute 31 working documents as Internet-Drafts. The list of current Internet- 32 Drafts is at https://datatracker.ietf.org/drafts/current/. 34 Internet-Drafts are draft documents valid for a maximum of six months 35 and may be updated, replaced, or obsoleted by other documents at any 36 time. It is inappropriate to use Internet-Drafts as reference 37 material or to cite them other than as "work in progress." 39 This Internet-Draft will expire on August 11, 2018. 41 Copyright Notice 43 Copyright (c) 2018 IETF Trust and the persons identified as the 44 document authors. All rights reserved. 46 This document is subject to BCP 78 and the IETF Trust's Legal 47 Provisions Relating to IETF Documents 48 (https://trustee.ietf.org/license-info) in effect on the date of 49 publication of this document. Please review these documents 50 carefully, as they describe your rights and restrictions with respect 51 to this document. Code Components extracted from this document must 52 include Simplified BSD License text as described in Section 4.e of 53 the Trust Legal Provisions and are provided without warranty as 54 described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 59 2. Terminology and Notation . . . . . . . . . . . . . . . . . . 3 60 2.1. YANG Schema Item iDentifier (SID) . . . . . . . . . . . . 5 61 2.2. CBOR diagnostic notation . . . . . . . . . . . . . . . . 5 62 3. Properties of the CBOR Encoding . . . . . . . . . . . . . . . 6 63 4. Encoding of YANG Data Node Instances . . . . . . . . . . . . 7 64 4.1. The 'leaf' Data Node . . . . . . . . . . . . . . . . . . 7 65 4.2. The 'container' Data Node . . . . . . . . . . . . . . . . 7 66 4.2.1. SIDs as keys . . . . . . . . . . . . . . . . . . . . 8 67 4.2.2. Member names as keys . . . . . . . . . . . . . . . . 10 68 4.3. The 'leaf-list' Data Node . . . . . . . . . . . . . . . . 10 69 4.4. The 'list' Data Node . . . . . . . . . . . . . . . . . . 11 70 4.4.1. SIDs as keys . . . . . . . . . . . . . . . . . . . . 11 71 4.4.2. Member names as keys . . . . . . . . . . . . . . . . 14 72 4.5. The 'anydata' Data Node . . . . . . . . . . . . . . . . . 15 73 4.6. The 'anyxml' Data Node . . . . . . . . . . . . . . . . . 17 74 5. Encoding of YANG data templates . . . . . . . . . . . . . . . 17 75 5.1. SIDs as keys . . . . . . . . . . . . . . . . . . . . . . 18 76 5.2. Member names as keys . . . . . . . . . . . . . . . . . . 19 77 6. Representing YANG Data Types in CBOR . . . . . . . . . . . . 20 78 6.1. The unsigned integer Types . . . . . . . . . . . . . . . 20 79 6.2. The integer Types . . . . . . . . . . . . . . . . . . . . 21 80 6.3. The 'decimal64' Type . . . . . . . . . . . . . . . . . . 21 81 6.4. The 'string' Type . . . . . . . . . . . . . . . . . . . . 22 82 6.5. The 'boolean' Type . . . . . . . . . . . . . . . . . . . 22 83 6.6. The 'enumeration' Type . . . . . . . . . . . . . . . . . 22 84 6.7. The 'bits' Type . . . . . . . . . . . . . . . . . . . . . 23 85 6.8. The 'binary' Type . . . . . . . . . . . . . . . . . . . . 24 86 6.9. The 'leafref' Type . . . . . . . . . . . . . . . . . . . 24 87 6.10. The 'identityref' Type . . . . . . . . . . . . . . . . . 25 88 6.10.1. SIDs as identityref . . . . . . . . . . . . . . . . 25 89 6.10.2. Name as identityref . . . . . . . . . . . . . . . . 26 90 6.11. The 'empty' Type . . . . . . . . . . . . . . . . . . . . 26 91 6.12. The 'union' Type . . . . . . . . . . . . . . . . . . . . 27 92 6.13. The 'instance-identifier' Type . . . . . . . . . . . . . 28 93 6.13.1. SIDs as instance-identifier . . . . . . . . . . . . 28 94 6.13.2. Names as instance-identifier . . . . . . . . . . . . 31 95 7. Security Considerations . . . . . . . . . . . . . . . . . . . 32 96 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 32 97 8.1. Tags Registry . . . . . . . . . . . . . . . . . . . . . . 32 98 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 32 99 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 33 100 10.1. Normative References . . . . . . . . . . . . . . . . . . 33 101 10.2. Informative References . . . . . . . . . . . . . . . . . 33 102 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 34 104 1. Introduction 106 The specification of the YANG 1.1 data modelling language [RFC7950] 107 defines an XML encoding for data instances, i.e. contents of 108 configuration datastores, state data, RPC inputs and outputs, action 109 inputs and outputs, and event notifications. 111 A new set of encoding rules has been defined to allow the use of the 112 same data models in environments based on the JavaScript Object 113 Notation (JSON) Data Interchange Format [RFC7159]. This is 114 accomplished in the JSON Encoding of Data Modeled with YANG 115 specification [RFC7951]. 117 The aim of this document is to define a set of encoding rules for the 118 Concise Binary Object Representation (CBOR) [RFC7049]. The resulting 119 encoding is more compact compared to XML and JSON and more suitable 120 for Constrained Nodes and/or Constrained Networks as defined by 121 [RFC7228]. 123 2. Terminology and Notation 125 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 126 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 127 document are to be interpreted as described in [RFC2119]. 129 The following terms are defined in [RFC7950]: 131 o action 133 o anydata 135 o anyxml 137 o data node 139 o data tree 141 o datastore 143 o feature 144 o identity 146 o module 148 o notification 150 o RPC 152 o schema node 154 o schema tree 156 o submodule 158 The following terms are defined in [RFC7951]: 160 o member name 162 o name of an identity 164 o namespace-qualified 166 The following terms are defined in [RFC8040]: 168 o yang-data (YANG extension) 170 o YANG data template 172 This specification also makes use of the following terminology: 174 o child: A schema node defined within a collection such as a 175 container, a list, a case, a notification, an RPC input, an RPC 176 output, an action input, an action output. 178 o delta: Difference between the current SID and a reference SID. A 179 reference SID is defined for each context for which deltas are 180 used. 182 o item: A schema node, an identity, a module, a submodule or a 183 feature defined using the YANG modeling language. 185 o parent: The collection in which a schema node is defined. 187 o YANG Schema Item iDentifier (SID): Unsigned integer used to 188 identify different YANG items. 190 2.1. YANG Schema Item iDentifier (SID) 192 Some of the items defined in YANG [RFC7950] require the use of a 193 unique identifier. In both NETCONF [RFC6241] and RESTCONF [RFC8040], 194 these identifiers are implemented using names. To allow the 195 implementation of data models defined in YANG in constrained devices 196 and constrained networks, a more compact method to identify YANG 197 items is required. This compact identifier, called YANG Schema Item 198 iDentifier (SID), is encoded using an unsigned integer. The 199 following items are identified using SIDs: 201 o identities 203 o data nodes 205 o RPCs and associated input(s) and output(s) 207 o actions and associated input(s) and output(s) 209 o notifications and associated information 211 o YANG modules, submodules and features 213 To minimize its size, in certain positions, SIDs are represented 214 using a (signed) delta from a reference SID and the current SID. 215 Conversion from SIDs to deltas and back to SIDs are stateless 216 processes solely based on the data serialized or deserialized. 218 Mechanisms and processes used to assign SIDs to YANG items and to 219 guarantee their uniqueness is outside the scope of the present 220 specification. If SIDs are to be used, the present specification is 221 used in conjunction with a specification defining this management. 222 One example for such a specification is under development as 223 [I-D.ietf-core-sid]. 225 2.2. CBOR diagnostic notation 227 Within this document, CBOR binary contents are represented using an 228 equivalent textual form called CBOR diagnostic notation as defined in 229 [RFC7049] section 6. This notation is used strictly for 230 documentation purposes and is never used in the data serialization. 231 Table 1 below provides a summary of this notation. 233 +----------+------+--------------------------+-----------+----------+ 234 | CBOR | CBOR | Diagnostic notation | Example | CBOR | 235 | content | type | | | encoding | 236 +----------+------+--------------------------+-----------+----------+ 237 | Unsigned | 0 | Decimal digits | 123 | 18 7b | 238 | integer | | | | | 239 | Negative | 1 | Decimal digits prefixed | -123 | 38 7a | 240 | integer | | by a minus sign | | | 241 | Byte | 2 | Hexadecimal value | h'f15c' | 42 f15c | 242 | string | | enclosed between single | | | 243 | | | quotes and prefixed by | | | 244 | | | an 'h' | | | 245 | Text | 3 | String of Unicode | "txt" | 63 | 246 | string | | characters enclosed | | 747874 | 247 | | | between double quotes | | | 248 | Array | 4 | Comma-separated list of | [ 1, 2 ] | 82 01 02 | 249 | | | values within square | | | 250 | | | brackets | | | 251 | Map | 5 | Comma-separated list of | { 1: 123, | a2 | 252 | | | key : value pairs within | 2: 456 } | 01187b | 253 | | | curly braces | | 021901c8 | 254 | Boolean | 7/20 | false | false | f4 | 255 | | 7/21 | true | true | f5 | 256 | Null | 7/22 | null | null | f6 | 257 | Not | 7/23 | undefined | undefined | f7 | 258 | assigned | | | | | 259 +----------+------+--------------------------+-----------+----------+ 261 Table 1: CBOR diagnostic notation summary 263 The following extensions to the CBOR diagnostic notation are 264 supported: 266 o Any text within and including a pair of slashes is considered a 267 comment. 269 o Deltas are visualized as numbers preceded by a '+' or '-' sign. 270 The use of the '+' sign for positive deltas represents an 271 extension to the CBOR diagnostic notation as defined by [RFC7049] 272 section 6. 274 3. Properties of the CBOR Encoding 276 This document defines CBOR encoding rules for YANG schema trees and 277 their subtrees. 279 Basic schema nodes such as leaf, leaf-list, list, anydata and anyxml 280 can be encoded standalone. In this case, only the value of this 281 schema node is encoded in CBOR. Identification of this value needs 282 to be provided by some external means when required. 284 A collection such as container, list instance, notification, RPC 285 input, RPC output, action input and action output is serialized using 286 a CBOR map in which each child schema node is encoded using a key and 287 a value. This specification supports two type of CBOR keys; YANG 288 Schema Item iDentifier (SID) as defined in Section 2.1 and member 289 names as defined in [RFC7951]. Each of these key types is encoded 290 using a specific CBOR type which allows their interpretation during 291 the deserialization process. The end user of this mapping 292 specification (e.g. RESTCONF [RFC8040], CoMI [I-D.ietf-core-comi]) 293 can mandate the use of a specific key type. 295 In order to minimize the size of the encoded data, the proposed 296 mapping avoids any unnecessary meta-information beyond those natively 297 supported by CBOR. For instance, CBOR tags are used solely in the 298 case of anyxml data nodes and the union datatype to distinguish 299 explicitly the use of different YANG datatypes encoded using the same 300 CBOR major type. 302 4. Encoding of YANG Data Node Instances 304 Schema node instances defined using the YANG modeling language are 305 encoded using CBOR [RFC7049] based on the rules defined in this 306 section. We assume that the reader is already familiar with both 307 YANG [RFC7950] and CBOR [RFC7049]. 309 4.1. The 'leaf' Data Node 311 Leafs MUST be encoded based on the encoding rules specified in 312 Section 6. 314 4.2. The 'container' Data Node 316 Collections such as containers, list instances, notifications, RPC 317 inputs, RPC outputs, action inputs and action outputs MUST be encoded 318 using a CBOR map data item (major type 5). A map is comprised of 319 pairs of data items, with each data item consisting of a key and a 320 value. Each key within the CBOR map is set to a data node 321 identifier, each value is set to the value of this data node instance 322 according to the instance datatype. 324 This specification supports two type of CBOR keys; SID as defined in 325 Section 2.1 encoded as deltas and member names as defined in 326 [RFC7951] encoded using CBOR text strings. The use of CBOR byte 327 strings for keys is reserved for future extensions. 329 4.2.1. SIDs as keys 331 Keys implemented using SIDs MUST be encoded using a CBOR unsigned 332 integer (major type 0) or CBOR negative integer (major type 1), 333 depending on the actual value. Keys are represented as the delta of 334 the associated SID, delta values are computed as follows: 336 o The delta value is equal to the SID of the current schema node 337 minus the SID of the parent schema node. When no parent exists in 338 the context of use of this container, the delta is set to the SID 339 of the current schema node (i.e., a parent with SID equal to zero 340 is assumed). 342 o Delta values may result in a negative number, clients and servers 343 MUST support both unsigned and negative deltas. 345 The following example shows the encoding of a 'system-state' 346 container instance with a single child, a clock container. The clock 347 container container has two children, a 'current-datetime' leaf and a 348 'boot-datetime' leaf. 350 Definition example from [RFC7317]: 352 typedef date-and-time { 353 type string { 354 pattern '\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(\.\d+)?(Z|[\+\-] 355 \d{2}:\d{2})'; 356 } 357 } 359 container system-state { 361 container clock { 362 leaf current-datetime { 363 type date-and-time; 364 } 366 leaf boot-datetime { 367 type date-and-time; 368 } 369 } 370 } 372 For this first representation, we assume that the SID of the parent 373 container (i.e. 'system-state') is not available to the serializer. 374 In this case, root data nodes are encoded using absolute SIDs. 376 CBOR diagnostic notation: 378 { 379 1717 : { / clock (SID 1717) / 380 +2 : "2015-10-02T14:47:24Z-05:00", / current-datetime (SID 1719)/ 381 +1 : "2015-09-15T09:12:58Z-05:00" / boot-datetime (SID 1718) / 382 } 383 } 385 CBOR encoding: 387 a1 # map(1) 388 19 06b5 # unsigned(1717) 389 a2 # map(2) 390 02 # unsigned(2) 391 78 1a # text(26) 392 323031352d31302d30325431343a34373a32345a2d30353a3030 393 01 # unsigned(1) 394 78 1a # text(26) 395 323031352d30392d31355430393a31323a35385a2d30353a3030 397 On the other hand, if the serializer is aware of the parent SID, 1716 398 in the case 'system-state' container, root data nodes are encoded 399 using deltas. 401 CBOR diagnostic notation: 403 { 404 +1 : { / clock (SID 1717) / 405 +2 : "2015-10-02T14:47:24Z-05:00", / current-datetime (SID 1719)/ 406 +1 : "2015-09-15T09:12:58Z-05:00" / boot-datetime (SID 1718) / 407 } 408 } 410 CBOR encoding: 412 a1 # map(1) 413 01 # unsigned(1) 414 a2 # map(2) 415 02 # unsigned(2) 416 78 1a # text(26) 417 323031352d31302d30325431343a34373a32345a2d30353a3030 418 01 # unsigned(1) 419 78 1a # text(26) 420 323031352d30392d31355430393a31323a35385a2d30353a3030 422 4.2.2. Member names as keys 424 Keys implemented using member names MUST be encoded using a CBOR text 425 string data item (major type 3). A namespace-qualified member name 426 MUST be used for all members of a top-level collection, and then also 427 whenever the namespaces of the schema node and its parent are 428 different. In all other cases, the simple form of the member name 429 MUST be used. Names and namespaces are defined in [RFC7951] section 430 4. 432 The following example shows the encoding of a 'system' container 433 instance using names. This example is described in Section 4.2.1. 435 CBOR diagnostic notation: 437 { 438 "ietf-system:clock" : { 439 "current-datetime" : "2015-10-02T14:47:24Z-05:00", 440 "boot-datetime" : "2015-09-15T09:12:58Z-05:00" 441 } 442 } 444 CBOR encoding: 446 a1 # map(1) 447 71 # text(17) 448 696574662d73797374656d3a636c6f636b # "ietf-system:clock" 449 a2 # map(2) 450 70 # text(16) 451 63757272656e742d6461746574696d65 # "current-datetime" 452 78 1a # text(26) 453 323031352d31302d30325431343a34373a32345a2d30353a3030 454 6d # text(13) 455 626f6f742d6461746574696d65 # "boot-datetime" 456 78 1a # text(26) 457 323031352d30392d31355430393a31323a35385a2d30353a3030 459 4.3. The 'leaf-list' Data Node 461 A leaf-list MUST be encoded using a CBOR array data item (major type 462 4). Each entry of this array MUST be encoded using the rules defined 463 by the YANG type specified. 465 The following example shows the encoding a 'search' leaf-list 466 instance containing the two entries, "ietf.org" and "ieee.org". 468 Definition example [RFC7317]: 470 typedef domain-name { 471 type string { 472 length "1..253"; 473 pattern '((([a-zA-Z0-9_]([a-zA-Z0-9\-_]){0,61})?[a-zA-Z0-9].) 474 *([a-zA-Z0-9_]([a-zA-Z0-9\-_]){0,61})?[a-zA-Z0-9]\.? 475 )|\.'; 476 } 477 } 479 leaf-list search { 480 type domain-name; 481 ordered-by user; 482 } 484 CBOR diagnostic notation: [ "ietf.org", "ieee.org" ] 486 CBOR encoding: 82 68 696574662e6f7267 68 696565652e6f7267 488 4.4. The 'list' Data Node 490 A list MUST be encoded using a CBOR array data item (major type 4). 491 Each list instance within this CBOR array is encoded using a CBOR map 492 data item (major type 5) based on the same rules as a YANG container 493 as defined in Section 4.2. 495 4.4.1. SIDs as keys 497 The following example show the encoding of a 'server' list instance 498 using SIDs. It is important to note that the protocol or method 499 using this mapping may carry a parent SID or may have the knowledge 500 of this parent SID based on its context. In these cases, delta 501 encoding can be performed based on this parent SID which minimizes 502 the size of the encoded data. 504 Definition example from [RFC7317]: 506 list server { 507 key name; 509 leaf name { 510 type string; 511 } 512 choice transport { 513 case udp { 514 container udp { 515 leaf address { 516 type host; 517 mandatory true; 518 } 519 leaf port { 520 type port-number; 521 } 522 } 523 } 524 } 525 leaf association-type { 526 type enumeration { 527 enum server; 528 enum peer; 529 enum pool; 530 } 531 default server; 532 } 533 leaf iburst { 534 type boolean; 535 default false; 536 } 537 leaf prefer { 538 type boolean; 539 default false; 540 } 541 } 543 CBOR diagnostic notation: 545 [ 546 { 547 1755 : "NRC TIC server", / name (SID 1755) / 548 1757 : { / udp (SID 1757) / 549 +1 : "tic.nrc.ca", / address (SID 1758) / 550 +2 : 123 / port (SID 1759) / 551 }, 552 1753 : 0, / association-type (SID 1753) / 553 1754 : false, / iburst (SID 1754) / 554 1756 : true / prefer (SID 1756) / 555 }, 556 { 557 1755 : "NRC TAC server", / name (SID 1755) / 558 1757 : { / udp (SID 1757) / 559 +1 : "tac.nrc.ca" / address (SID 1758) / 560 } 561 } 562 ] 564 CBOR encoding: 566 82 # array(2) 567 a5 # map(5) 568 19 06db # unsigned(1755) 569 6e # text(14) 570 4e52432054494320736572766572 # "NRC TIC server" 571 19 06dd # unsigned(1757) 572 a2 # map(2) 573 01 # unsigned(1) 574 6a # text(10) 575 7469632e6e72632e6361 # "tic.nrc.ca" 576 02 # unsigned(2) 577 18 7b # unsigned(123) 578 19 06d9 # unsigned(1753) 579 00 # unsigned(0) 580 19 06da # unsigned(1754) 581 f4 # primitive(20) 582 19 06dc # unsigned(1756) 583 f5 # primitive(21) 584 a2 # map(2) 585 19 06db # unsigned(1755) 586 6e # text(14) 587 4e52432054414320736572766572 # "NRC TAC server" 588 19 06dd # unsigned(1757) 589 a1 # map(1) 590 01 # unsigned(1) 591 6a # text(10) 592 7461632e6e72632e6361 # "tac.nrc.ca" 594 4.4.2. Member names as keys 596 The following example shows the encoding of a 'server' list instance 597 using names. This example is described in Section 4.4.1. 599 CBOR diagnostic notation: 601 [ 602 { 603 "ietf-system:name" : "NRC TIC server", 604 "ietf-system:udp" : { 605 "address" : "tic.nrc.ca", 606 "port" : 123 607 }, 608 "ietf-system:association-type" : 0, 609 "ietf-system:iburst" : false, 610 "ietf-system:prefer" : true 611 }, 612 { 613 "ietf-system:name" : "NRC TAC server", 614 "ietf-system:udp" : { 615 "address" : "tac.nrc.ca" 616 } 617 } 618 ] 620 CBOR encoding: 622 82 # array(2) 623 a5 # map(5) 624 70 # text(16) 625 696574662d73797374656d3a6e616d65 # "ietf-system:name" 626 6e # text(14) 627 4e52432054494320736572766572 # "NRC TIC server" 628 6f # text(15) 629 696574662d73797374656d3a756470 # "ietf-system:udp" 630 a2 # map(2) 631 67 # text(7) 632 61646472657373 # "address" 633 6a # text(10) 634 7469632e6e72632e6361 # "tic.nrc.ca" 635 64 # text(4) 636 706f7274 # "port" 637 18 7b # unsigned(123) 638 78 1c # text(28) 639 696574662d73797374656d3a6173736f63696174696f6e2d74797065 640 00 # unsigned(0) 641 72 # text(18) 642 696574662d73797374656d3a696275727374 # "ietf-system:iburst" 643 f4 # primitive(20) 644 72 # text(18) 645 696574662d73797374656d3a707265666572 # "ietf-system:prefer" 646 f5 # primitive(21) 647 a2 # map(2) 648 70 # text(16) 649 696574662d73797374656d3a6e616d65 # "ietf-system:name" 650 6e # text(14) 651 4e52432054414320736572766572 # "NRC TAC server" 652 6f # text(15) 653 696574662d73797374656d3a756470 # "ietf-system:udp" 654 a1 # map(1) 655 67 # text(7) 656 61646472657373 # "address" 657 6a # text(10) 658 7461632e6e72632e6361 # "tac.nrc.ca" 660 4.5. The 'anydata' Data Node 662 An anydata serves as a container for an arbitrary set of schema nodes 663 that otherwise appear as normal YANG-modeled data. An anydata 664 instance is encoded using the same rules as a container, i.e., CBOR 665 map. The requirement that anydata content can be modeled by YANG 666 implies the following: 668 o Keys of any inner data nodes MUST be set to valid deltas or member 669 names. 671 o The CBOR array MUST contain either unique scalar values (as a 672 leaf-list, see Section 4.3), or maps (as a list, see Section 4.4). 674 o Values MUST follow the encoding rules of one of the datatypes 675 listed in Section 6. 677 The following example shows a possible use of anydata. In this 678 example, an anydata is used to define a data node containing a 679 notification event, this data node can be part of a YANG list to 680 create an event logger. 682 Definition example: 684 anydata event; 686 This example also assumes the assistance of the following 687 notification. 689 module example-port { 690 ... 692 notification example-port-fault { # SID 2600 693 leaf port-name { # SID 2601 694 type string; 695 } 696 leaf port-fault { # SID 2601 697 type string; 698 } 699 } 700 } 702 CBOR diagnostic notation: 704 { 705 2601 : "0/4/21", / port-name / 706 2602 : "Open pin 2" / port-fault / 707 } 709 CBOR encoding: 711 a2 # map(2) 712 19 0a29 # unsigned(2601) 713 66 # text(6) 714 302f342f3231 # "0/4/21" 715 19 0a2a # unsigned(2602) 716 6a # text(10) 717 4f70656e2070696e2032 # "Open pin 2" 719 4.6. The 'anyxml' Data Node 721 An anyxml schema node is used to serialize an arbitrary CBOR content, 722 i.e., its value can be any CBOR binary object. anyxml value may 723 contain CBOR data items tagged with one of the tag listed in 724 Section 8.1, these tags shall be supported. 726 The following example shows a valid CBOR encoded instance. 728 Definition example from [RFC7951]: 730 anyxml bar; 732 CBOR diagnostic notation: [true, null, true] 734 CBOR encoding: 83 f5 f6 f5 736 5. Encoding of YANG data templates 738 YANG data templates are data structures defined in YANG but not 739 intended to be implemented as part of a datastore. YANG data 740 templates are defined using the 'yang-data' extension as described by 741 RFC 8040. 743 The encoding rules defined for YANG containers in section 4.2 may be 744 used to serialize YANG data templates. 746 Definition example from [I-D.ietf-core-comi]: 748 import ietf-restconf { 749 prefix rc; 750 } 752 rc:yang-data yang-errors { 753 container error { 754 leaf error-tag { 755 type identityref { 756 base error-tag; 757 } 758 } 759 leaf error-app-tag { 760 type identityref { 761 base error-app-tag; 762 } 763 } 764 leaf error-data-node { 765 type instance-identifier; 766 } 767 leaf error-message { 768 type string; 769 } 770 } 771 } 773 Just like YANG containers, YANG data templates can be encoded using 774 either SIDs or names. 776 5.1. SIDs as keys 778 This example shows a serialization example of the yang-errors 779 template using SIDs as CBOR map key. 781 CBOR diagnostic notation: 783 { 784 1024 : { / error (SID 1024) / 785 +4 : 1011, / error-tag (SID 1028) / 786 / = invalid-value (SID 1011) / 787 +1 : 1018, / error-app-tag (SID 1025) / 788 / = not-in-range (SID 1018) / 789 +2 : 1740, / error-data-node (SID 1026) / 790 / = timezone-utc-offset (SID 1740) / 791 +3 : "max value exceeded" / error-message (SID 1027) / 792 } 793 } 795 CBOR encoding: 797 A1 # map(1) 798 19 0400 # unsigned(1024) 799 A4 # map(4) 800 04 # unsigned(4) 801 19 03F3 # unsigned(1011) 802 01 # unsigned(1) 803 19 03FA # unsigned(1018) 804 02 # unsigned(2) 805 19 06CC # unsigned(1740) 806 03 # unsigned(3) 807 76 # text(22) 808 6D6178696D756D2076616C7565206578636565646564 810 5.2. Member names as keys 812 This example shows a serialization example of the yang-errors 813 template using member names as CBOR map key. 815 CBOR diagnostic notation: 817 { 818 "ietf-comi:error" : { 819 "error-tag" : "invalid-value", 820 "error-app-tag" : "not-in-range", 821 "error-data-node" : "timezone-utc-offset", 822 "error-message" : "max value exceeded" 823 } 824 } 826 CBOR encoding: 828 A1 # map(1) 829 6F # text(15) 830 696574662D636F6D693A6572726F72 831 A4 # map(4) 832 69 # text(9) 833 6572726F722D746167 # "error-tag" 834 6D # text(13) 835 696E76616C69642D76616C7565 836 6D # text(13) 837 6572726F722D6170702D746167 838 6C # text(12) 839 6E6F742D696E2D72616E6765 840 6F # text(15) 841 6572726F722D646174612D6E6F6465 842 73 # text(19) 843 74696D657A6F6E652D7574632D6F6666736574 844 6D # text(13) 845 6572726F722D6D657373616765 846 72 # text(18) 847 6D61782076616C7565206578636565646564 849 6. Representing YANG Data Types in CBOR 851 The CBOR encoding of an instance of a leaf or leaf-list data node 852 depends on the built-in type of that data node. The following sub- 853 section defined the CBOR encoding of each built-in type supported by 854 YANG as listed in [RFC7950] section 4.2.4. Each subsection shows an 855 example value assigned to a data node instance of the discussed 856 built-in type. 858 6.1. The unsigned integer Types 860 Leafs of type uint8, uint16, uint32 and uint64 MUST be encoded using 861 a CBOR unsigned integer data item (major type 0). 863 The following example shows the encoding of a 'mtu' leaf instance set 864 to 1280 bytes. 866 Definition example from [RFC7277]: 868 leaf mtu { 869 type uint16 { 870 range "68..max"; 871 } 872 } 874 CBOR diagnostic notation: 1280 875 CBOR encoding: 19 0500 877 6.2. The integer Types 879 Leafs of type int8, int16, int32 and int64 MUST be encoded using 880 either CBOR unsigned integer (major type 0) or CBOR negative integer 881 (major type 1), depending on the actual value. 883 The following example shows the encoding of a 'timezone-utc-offset' 884 leaf instance set to -300 minutes. 886 Definition example from [RFC7317]: 888 leaf timezone-utc-offset { 889 type int16 { 890 range "-1500 .. 1500"; 891 } 892 } 894 CBOR diagnostic notation: -300 896 CBOR encoding: 39 012b 898 6.3. The 'decimal64' Type 900 Leafs of type decimal64 MUST be encoded using a decimal fraction as 901 defined in [RFC7049] section 2.4.3. 903 The following example shows the encoding of a 'my-decimal' leaf 904 instance set to 2.57. 906 Definition example from [RFC7317]: 908 leaf my-decimal { 909 type decimal64 { 910 fraction-digits 2; 911 range "1 .. 3.14 | 10 | 20..max"; 912 } 913 } 915 CBOR diagnostic notation: 4([-2, 257]) 917 CBOR encoding: c4 82 21 19 0101 919 6.4. The 'string' Type 921 Leafs of type string MUST be encoded using a CBOR text string data 922 item (major type 3). 924 The following example shows the encoding of a 'name' leaf instance 925 set to "eth0". 927 Definition example from [RFC7223]: 929 leaf name { 930 type string; 931 } 933 CBOR diagnostic notation: "eth0" 935 CBOR encoding: 64 65746830 937 6.5. The 'boolean' Type 939 Leafs of type boolean MUST be encoded using a CBOR true (major type 940 7, additional information 21) or false data item (major type 7, 941 additional information 20). 943 The following example shows the encoding of an 'enabled' leaf 944 instance set to 'true'. 946 Definition example from [RFC7317]: 948 leaf enabled { 949 type boolean; 950 } 952 CBOR diagnostic notation: true 954 CBOR encoding: f5 956 6.6. The 'enumeration' Type 958 Leafs of type enumeration MUST be encoded using a CBOR unsigned 959 integer (major type 0) or CBOR negative integer (major type 1), 960 depending on the actual value. Enumeration values are either 961 explicitly assigned using the YANG statement 'value' or automatically 962 assigned based on the algorithm defined in [RFC7950] section 9.6.4.2. 964 The following example shows the encoding of an 'oper-status' leaf 965 instance set to 'testing'. 967 Definition example from [RFC7317]: 969 leaf oper-status { 970 type enumeration { 971 enum up { value 1; } 972 enum down { value 2; } 973 enum testing { value 3; } 974 enum unknown { value 4; } 975 enum dormant { value 5; } 976 enum not-present { value 6; } 977 enum lower-layer-down { value 7; } 978 } 979 } 981 CBOR diagnostic notation: 3 983 CBOR encoding: 03 985 6.7. The 'bits' Type 987 Leafs of type bits MUST be encoded using a CBOR byte string data item 988 (major type 2). Bits position are either explicitly assigned using 989 the YANG statement 'position' or automatically assigned based on the 990 algorithm defined in [RFC7950] section 9.7.4.2. 992 Bits position 0 to 7 are assigned to the first byte within the byte 993 string, bits 8 to 15 to the second byte, and subsequent bytes are 994 assigned similarly. Within each byte, bits are assigned from least 995 to most significant. 997 The following example shows the encoding of a 'mybits' leaf instance 998 with the 'disable-nagle' and '10-Mb-only' flags set. 1000 Definition example from [RFC7950]: 1002 leaf mybits { 1003 type bits { 1004 bit disable-nagle { 1005 position 0; 1006 } 1007 bit auto-sense-speed { 1008 position 1; 1009 } 1010 bit 10-Mb-only { 1011 position 2; 1012 } 1013 } 1014 } 1015 CBOR diagnostic notation: h'05' 1017 CBOR encoding: 41 05 1019 6.8. The 'binary' Type 1021 Leafs of type binary MUST be encoded using a CBOR byte string data 1022 item (major type 2). 1024 The following example shows the encoding of an 'aes128-key' leaf 1025 instance set to 0x1f1ce6a3f42660d888d92a4d8030476e. 1027 Definition example: 1029 leaf aes128-key { 1030 type binary { 1031 length 16; 1032 } 1033 } 1035 CBOR diagnostic notation: h'1f1ce6a3f42660d888d92a4d8030476e' 1037 CBOR encoding: 50 1f1ce6a3f42660d888d92a4d8030476e 1039 6.9. The 'leafref' Type 1041 Leafs of type leafref MUST be encoded using the rules of the schema 1042 node referenced by the 'path' YANG statement. 1044 The following example shows the encoding of an 'interface-state-ref' 1045 leaf instance set to "eth1". 1047 Definition example from [RFC7223]: 1049 typedef interface-state-ref { 1050 type leafref { 1051 path "/interfaces-state/interface/name"; 1052 } 1053 } 1055 container interfaces-state { 1056 list interface { 1057 key "name"; 1058 leaf name { 1059 type string; 1060 } 1061 leaf-list higher-layer-if { 1062 type interface-state-ref; 1063 } 1064 } 1065 } 1067 CBOR diagnostic notation: "eth1" 1069 CBOR encoding: 64 65746831 1071 6.10. The 'identityref' Type 1073 This specification supports two approaches for encoding identityref, 1074 a YANG Schema Item iDentifier (SID) as defined in Section 2.1 or a 1075 name as defined in [RFC7951] section 6.8. 1077 6.10.1. SIDs as identityref 1079 When schema nodes of type identityref are implemented using SIDs, 1080 they MUST be encoded using a CBOR unsigned integer data item (major 1081 type 0). (Note that no delta mechanism is employed for SIDs as 1082 identityref.) 1084 The following example shows the encoding of a 'type' leaf instance 1085 set to the value 'iana-if-type:ethernetCsmacd' (SID 1180). 1087 Definition example from [RFC7317]: 1089 identity interface-type { 1090 } 1092 identity iana-interface-type { 1093 base interface-type; 1094 } 1096 identity ethernetCsmacd { 1097 base iana-interface-type; 1098 } 1100 leaf type { 1101 type identityref { 1102 base interface-type; 1103 } 1104 } 1106 CBOR diagnostic notation: 1180 1108 CBOR encoding: 19 049c 1110 6.10.2. Name as identityref 1112 Alternatively, an identityref may be encoded using a name as defined 1113 in [RFC7951] section 6.8. When names are used, identityref MUST be 1114 encoded using a CBOR text string data item (major type 3). If the 1115 identity is defined in another module than the leaf node containing 1116 the identityref value, the namespace-qualified form MUST be used. 1117 Otherwise, both the simple and namespace-qualified forms are 1118 permitted. Names and namespaces are defined in [RFC7951] section 4. 1120 The following example shows the encoding of the identity 'iana-if- 1121 type:ethernetCsmacd' using its name. This example is described in 1122 Section 6.10.1. 1124 CBOR diagnostic notation: "iana-if-type:ethernetCsmacd" 1126 CBOR encoding: 78 1b 1127 69616e612d69662d747970653a65746865726e657443736d616364 1129 6.11. The 'empty' Type 1131 Leafs of type empty MUST be encoded using the CBOR null value (major 1132 type 7, additional information 22). 1134 The following example shows the encoding of a 'is-router' leaf 1135 instance when present. 1137 Definition example from [RFC7277]: 1139 leaf is-router { 1140 type empty; 1141 } 1143 CBOR diagnostic notation: null 1145 CBOR encoding: f6 1147 6.12. The 'union' Type 1149 Leafs of type union MUST be encoded using the rules associated with 1150 one of the types listed. When used in a union, the following YANG 1151 datatypes are prefixed by CBOR tag to avoid confusion between 1152 different YANG datatypes encoded using the same CBOR major type. 1154 o bits 1156 o enumeration 1158 o identityref 1160 o instance-identifier 1162 See Section 8.1 for more information about these CBOR tags. 1164 The following example shows the encoding of an 'ip-address' leaf 1165 instance when set to "2001:db8:a0b:12f0::1". 1167 Definition example from [RFC7317]: 1169 typedef ipv4-address { 1170 type string { 1171 pattern '(([0-9]|[1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])\.){3} 1172 ([0-9][1-9][0-9]|1[0-9][0-9]|2[0-4][0-9]|25[0-5])(%[\p{N} 1173 \p{L}]+)?'; 1174 } 1175 } 1177 typedef ipv6-address { 1178 type string { 1179 pattern '((:|[0-9a-fA-F]{0,4}):)([0-9a-fA-F]{0,4}:){0,5}((([0-9a 1180 -fA-F]{0,4}:)?(:|[0-9a-fA-F]{0,4}))|(((25[0-5]|2[0-4][0 1181 -9]|[01]?[0-9]?[0-9])\.){3}(25[0-5]|2[0-4][0-9]|[01]?[0 1182 -9]?[0-9])))(%[\p{N}\p{L}]+)?'; 1183 pattern '(([^:]+:){6}(([^:]+:[^:]+)|(.*\..*)))|((([^:]+:)*[^:]+) 1184 ?::(([^:]+:)*[^:]+)?)(%.+)?'; 1185 } 1186 } 1188 typedef ip-address { 1189 type union { 1190 type ipv4-address; 1191 type ipv6-address; 1192 } 1193 } 1195 leaf address { 1196 type inet:ip-address; 1197 } 1199 CBOR diagnostic notation: "2001:db8:a0b:12f0::1" 1201 CBOR encoding: 74 323030313a6462383a6130623a313266303a3a31 1203 6.13. The 'instance-identifier' Type 1205 This specification supports two approaches for encoding an instance- 1206 identifier, one based on YANG Schema Item iDentifier (SID) as defined 1207 in Section 2.1 and one based on names as defined in [RFC7951] section 1208 6.11. 1210 6.13.1. SIDs as instance-identifier 1212 SIDs uniquely identify a data node. In the case of a single instance 1213 data node, a data node defined at the root of a YANG module or 1214 submodule or data nodes defined within a container, the SID is 1215 sufficient to identify this instance. 1217 In the case of a data node member of a YANG list, a SID is combined 1218 with the list key(s) to identify each instance within the YANG 1219 list(s). 1221 Single instance data nodes MUST be encoded using a CBOR unsigned 1222 integer data item (major type 0) and set to the targeted data node 1223 SID. 1225 Data nodes member of a YANG list MUST be encoded using a CBOR array 1226 data item (major type 4) containing the following entries: 1228 o The first entry MUST be encoded as a CBOR unsigned integer data 1229 item (major type 0) and set to the targeted data node SID. 1231 o The following entries MUST contain the value of each key required 1232 to identify the instance of the targeted data node. These keys 1233 MUST be ordered as defined in the 'key' YANG statement, starting 1234 from top level list, and follow by each of the subordinate 1235 list(s). 1237 *First example:* 1239 The following example shows the encoding of a leaf instance of type 1240 instance-identifier which identifies the data node "/system/contact" 1241 (SID 1737). 1243 Definition example from [RFC7317]: 1245 container system { 1247 leaf contact { 1248 type string; 1249 } 1251 leaf hostname { 1252 type inet:domain-name; 1253 } 1254 } 1256 CBOR diagnostic notation: 1737 1258 CBOR encoding: 19 06c9 1260 *Second example:* 1262 The following example shows the encoding of a leaf instance of type 1263 instance-identifier which identify the data node instance 1264 "/system/authentication/user/authorized-key/key-data" (SID 1730) for 1265 user name "bob" and authorized-key "admin". 1267 Definition example from [RFC7317]: 1269 list user { 1270 key name; 1272 leaf name { 1273 type string; 1274 } 1275 leaf password { 1276 type ianach:crypt-hash; 1277 } 1279 list authorized-key { 1280 key name; 1282 leaf name { 1283 type string; 1284 } 1285 leaf algorithm { 1286 type string; 1287 } 1288 leaf key-data { 1289 type binary; 1290 } 1291 } 1293 CBOR diagnostic notation: [1730, "bob", "admin"] 1295 CBOR encoding: 1297 83 # array(3) 1298 19 06c2 # unsigned(1730) 1299 63 # text(3) 1300 626f62 # "bob" 1301 65 # text(5) 1302 61646d696e # "admin" 1304 *Third example:* 1306 The following example shows the encoding of a leaf instance of type 1307 instance-identifier which identify the list instance 1308 "/system/authentication/user" (SID 1726) corresponding to the user 1309 name "jack". 1311 CBOR diagnostic notation: [1726, "jack"] 1312 CBOR encoding: 1314 82 # array(2) 1315 19 06be # unsigned(1726) 1316 64 # text(4) 1317 6a61636b # "jack" 1319 6.13.2. Names as instance-identifier 1321 The use of names as instance-identifier is defined in [RFC7951] 1322 section 6.11. The resulting xpath MUST be encoded using a CBOR text 1323 string data item (major type 3). 1325 *First example:* 1327 This example is described in Section 6.13.1. 1329 CBOR diagnostic notation: "/ietf-system:system/contact" 1331 CBOR encoding: 1333 78 1c 2f20696574662d73797374656d3a73797374656d2f636f6e74616374 1335 *Second example:* 1337 This example is described in Section 6.13.1. 1339 CBOR diagnostic notation: 1341 "/ietf-system:system/authentication/user[name='bob']/authorized-key 1342 [name='admin']/key-data" 1344 CBOR encoding: 1346 78 59 1347 2f696574662d73797374656d3a73797374656d2f61757468656e74696361 1348 74696f6e2f757365725b6e616d653d27626f62275d2f617574686f72697a 1349 65642d6b65795b6e616d653d2761646d696e275d2f6b65792d64617461 1351 *Third example:* 1353 This example is described in Section 6.13.1. 1355 CBOR diagnostic notation: 1357 "/ietf-system:system/authentication/user[name='bob']" 1359 CBOR encoding: 1361 78 33 1362 2f696574662d73797374656d3a73797374656d2f61757468656e74696361 1363 74696f6e2f757365725b6e616d653d27626f62275d 1365 7. Security Considerations 1367 The security considerations of [RFC7049] and [RFC7950] apply. 1369 This document defines an alternative encoding for data modeled in the 1370 YANG data modeling language. As such, this encoding does not 1371 contribute any new security issues in addition of those identified 1372 for the specific protocol or context for which it is used. 1374 To minimize security risks, software on the receiving side SHOULD 1375 reject all messages that do not comply to the rules of this document 1376 and reply with an appropriate error message to the sender. 1378 8. IANA Considerations 1380 8.1. Tags Registry 1382 This specification requires the assignment of CBOR tags for the 1383 following YANG datatypes. These tags are added to the Tags Registry 1384 as defined in section 7.2 of [RFC7049]. 1386 +-----+---------------------+---------------------------+-----------+ 1387 | Tag | Data Item | Semantics | Reference | 1388 +-----+---------------------+---------------------------+-----------+ 1389 | 40 | bits | YANG bits datatype | RFC XXXX | 1390 | 41 | enumeration | YANG enumeration datatype | RFC XXXX | 1391 | 42 | identityref | YANG identityref datatype | RFC XXXX | 1392 | 43 | instance-identifier | YANG instance-identifier | RFC XXXX | 1393 | | | datatype | | 1394 +-----+---------------------+---------------------------+-----------+ 1396 // RFC Ed.: update Tag values using allocated tags if needed and 1397 remove this note // RFC Ed.: replace XXXX with RFC number and remove 1398 this note 1400 9. Acknowledgments 1402 This document has been largely inspired by the extensive works done 1403 by Andy Bierman and Peter van der Stok on [I-D.ietf-core-comi]. 1404 [RFC7951] has also been a critical input to this work. The authors 1405 would like to thank the authors and contributors to these two drafts. 1407 The authors would also like to acknowledge the review, feedback, and 1408 comments from Ladislav Lhotka and Juergen Schoenwaelder. 1410 10. References 1412 10.1. Normative References 1414 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 1415 Requirement Levels", BCP 14, RFC 2119, 1416 DOI 10.17487/RFC2119, March 1997, 1417 . 1419 [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., 1420 and A. Bierman, Ed., "Network Configuration Protocol 1421 (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, 1422 . 1424 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object 1425 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, 1426 October 2013, . 1428 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", 1429 RFC 7950, DOI 10.17487/RFC7950, August 2016, 1430 . 1432 10.2. Informative References 1434 [I-D.ietf-core-comi] 1435 Veillette, M., Stok, P., Pelov, A., and A. Bierman, "CoAP 1436 Management Interface", draft-ietf-core-comi-02 (work in 1437 progress), December 2017. 1439 [I-D.ietf-core-sid] 1440 Veillette, M. and A. Pelov, "YANG Schema Item iDentifier 1441 (SID)", draft-ietf-core-sid-03 (work in progress), 1442 December 2017. 1444 [RFC7159] Bray, T., Ed., "The JavaScript Object Notation (JSON) Data 1445 Interchange Format", RFC 7159, DOI 10.17487/RFC7159, March 1446 2014, . 1448 [RFC7223] Bjorklund, M., "A YANG Data Model for Interface 1449 Management", RFC 7223, DOI 10.17487/RFC7223, May 2014, 1450 . 1452 [RFC7228] Bormann, C., Ersue, M., and A. Keranen, "Terminology for 1453 Constrained-Node Networks", RFC 7228, 1454 DOI 10.17487/RFC7228, May 2014, 1455 . 1457 [RFC7277] Bjorklund, M., "A YANG Data Model for IP Management", 1458 RFC 7277, DOI 10.17487/RFC7277, June 2014, 1459 . 1461 [RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for 1462 System Management", RFC 7317, DOI 10.17487/RFC7317, August 1463 2014, . 1465 [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", 1466 RFC 7951, DOI 10.17487/RFC7951, August 2016, 1467 . 1469 [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF 1470 Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, 1471 . 1473 Authors' Addresses 1475 Michel Veillette (editor) 1476 Trilliant Networks Inc. 1477 610 Rue du Luxembourg 1478 Granby, Quebec J2J 2V2 1479 Canada 1481 Phone: +14503750556 1482 Email: michel.veillette@trilliantinc.com 1484 Alexander Pelov (editor) 1485 Acklio 1486 2bis rue de la Chataigneraie 1487 Cesson-Sevigne, Bretagne 35510 1488 France 1490 Email: a@ackl.io 1492 Abhinav Somaraju 1493 Tridonic GmbH & Co KG 1494 Farbergasse 15 1495 Dornbirn, Vorarlberg 6850 1496 Austria 1498 Phone: +43664808926169 1499 Email: abhinav.somaraju@tridonic.com 1500 Randy Turner 1501 Landis+Gyr 1502 30000 Mill Creek Ave 1503 Suite 100 1504 Alpharetta, GA 30022 1505 US 1507 Phone: ++16782581292 1508 Email: randy.turner@landisgyr.com 1509 URI: http://www.landisgyr.com/ 1511 Ana Minaburo 1512 Acklio 1513 2bis rue de la chataigneraie 1514 Cesson-Sevigne, Bretagne 35510 1515 France 1517 Email: ana@ackl.io