idnits 2.17.1 draft-ietf-ccamp-l1csm-yang-11.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (March 9, 2020) is 1508 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Missing Reference: 'RFC XXXX' is mentioned on line 276, but not defined -- Possible downref: Non-RFC (?) normative reference: ref. 'MEF63' == Outdated reference: A later version (-18) exists of draft-ietf-ccamp-layer1-types-04 Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 CCAMP Working Group Y. Lee 3 Internet-Draft Samsung 4 Intended status: Standards Track K. Lee 5 Expires: September 10, 2020 Korea Telecom 6 H. Zheng 7 D. Dhody 8 Huawei Technologies 9 O. Gonzalez de Dios 10 Telefonica 11 D. Ceccarelli 12 Ericsson 13 March 9, 2020 15 A YANG Data Model for L1 Connectivity Service Model (L1CSM) 16 draft-ietf-ccamp-l1csm-yang-11 18 Abstract 20 This document provides a YANG data model for Layer 1 Connectivity 21 Service Model (L1CSM). The intent of this document is to provide a 22 Layer 1 service model exploiting YANG data model, which can be 23 utilized by a customer network controller to initiate a service 24 request connectivity as well as retrieving service states toward a 25 Layer 1 network controller communicating with its customer network 26 controller. This YANG model is NMDA-compliant. 28 Status of This Memo 30 This Internet-Draft is submitted in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF). Note that other groups may also distribute 35 working documents as Internet-Drafts. The list of current Internet- 36 Drafts is at https://datatracker.ietf.org/drafts/current/. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 This Internet-Draft will expire on September 10, 2020. 45 Copyright Notice 47 Copyright (c) 2020 IETF Trust and the persons identified as the 48 document authors. All rights reserved. 50 This document is subject to BCP 78 and the IETF Trust's Legal 51 Provisions Relating to IETF Documents 52 (https://trustee.ietf.org/license-info) in effect on the date of 53 publication of this document. Please review these documents 54 carefully, as they describe your rights and restrictions with respect 55 to this document. Code Components extracted from this document must 56 include Simplified BSD License text as described in Section 4.e of 57 the Trust Legal Provisions and are provided without warranty as 58 described in the Simplified BSD License. 60 Table of Contents 62 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 63 1.1. Deployment Scenarios . . . . . . . . . . . . . . . . . . 3 64 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 65 1.3. Tree Diagram . . . . . . . . . . . . . . . . . . . . . . 6 66 1.4. Prefixes in Data Node Names . . . . . . . . . . . . . . . 6 67 2. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 7 68 3. L1CSM YANG Model (Tree Structure) . . . . . . . . . . . . . . 7 69 4. L1CSM YANG Code . . . . . . . . . . . . . . . . . . . . . . . 8 70 5. JSON Example . . . . . . . . . . . . . . . . . . . . . . . . 12 71 6. Security Considerations . . . . . . . . . . . . . . . . . . . 14 72 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14 73 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15 74 9. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 15 75 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 15 76 10.1. Normative References . . . . . . . . . . . . . . . . . . 15 77 10.2. Informative References . . . . . . . . . . . . . . . . . 16 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17 80 1. Introduction 82 This document provides a YANG data model for L1VPN Connectivity 83 Service Model (L1CSM) which can be classified as Network Service YANG 84 module per [RFC8199]. The intent of this document is to provide a 85 transport service model exploiting YANG data model, which can be 86 utilized by a client network controller to initiate a service request 87 connectivity request as well as retrieving service states toward a 88 transport network controller communicating with the client controller 89 via a NETCONF [RFC8341] or a RESTCONF [RFC8040] interface. 91 [RFC4847] provides a framework and service level requirements for 92 Layer 1 Virtual Private Networks (L1VPNs). It classifies service 93 models as management-based service model, signaling-based service 94 model (Basic Mode) and signaling and routing service model (Enhanced 95 Mode). 97 In the management-based service model, customer management systems 98 and provider management systems communicate with each other. 99 Customer management systems access provider management systems to 100 request layer 1 connection setup/deletion between a pair of CEs. 101 Customer management systems may obtain additional information, such 102 as resource availability information and monitoring information, from 103 provider management systems. There is no control message exchange 104 between a CE and PE. 106 In the signaling-based service model (Basic Model), the CE-PE 107 interface's functional repertoire is limited to path setup signaling 108 only. In the Signaling and routing service model (Enhanced Mode), 109 the CE-PE interface provides the signaling capabilities as in the 110 Basic Mode, plus permits limited exchange of information between the 111 control planes of the provider and the customer to help such 112 functions as discovery of customer network routing information (i.e., 113 reachability or TE information in remote customer sites), or 114 parameters of the part of the provider's network dedicated to the 115 customer. 117 The primary focus of this document is to describe L1CS YANG model 118 required for the instantiation of point-to-point L1VPN service. A 119 L1VPN is a service offered by a core layer 1 network to provide layer 120 1 connectivity between two or more customer sites where the customer 121 has some control over the establishment and type of the connectivity. 123 The data model presented in Section 3 is in consistent with [MEF63]. 124 The data model includes configuration and state data according to the 125 new Network Management Datastore Architecture [RFC8342]. 127 1.1. Deployment Scenarios 129 Figure 1 depicts a deployment scenario of the L1VPN SDN control-based 130 service model for an external customer instantiating L1 point-to- 131 point connectivity to the provider. 133 +------------+ 134 | Customer | 135 | Service | 136 |Orchestrator| 137 +------------+ 138 | 139 .. .. .. .. ..|.. .. .. .. .. .. 140 : | : 141 : +--------------------+ : 142 : | | : 143 : | +----------+ | : 144 : | | Network | | : 145 : | | SDN | | : 146 : | |Controller| | : 147 : | |/NMS/EMS | | : 148 : | +----------+ | : 149 : | | : 150 : | | : 151 +----+ : +----+ +----+ +----+ : +----+ 152 | CE |----:---| PE |----| P |----| PE |---:---| CE | 153 +----+ : +----+ +----+ +----+ : +----+ 154 : | | : 155 : | | : 156 : +--------------------+ : 157 : | | : 158 : |<-Provider network->| : 160 Customer Customer 161 Interface Interface 163 Figure 1: L1VPN SDN Controller/EMS/NMS-Based Service Model: External 164 Customer 166 With this scenario, the customer service orchestrator interfaces with 167 the network SDN controller of the provider using Customer Service 168 Model as defined in [RFC8309]. 170 Figure 2 depicts another deployment scenario for internal customer 171 (e.g., higher-layer service management department(s)) interfacing the 172 layer 1 transport network department. With this scenario, a multi- 173 service backbone is characterized such that each service department 174 of a provider (e.g., L2/3 services) that receives the same provider's 175 L1VPN service provides a different kind of higher-layer service. The 176 customer receiving the L1VPN service (i.e., each service department) 177 can offer its own services, whose payloads can be any layer (e.g., 178 ATM, IP, TDM). The layer 1 transport network and each service 179 network belong to the same organization, but may be managed 180 separately. The Service SDN Controller is the control/management 181 entity owned by higher-layer service department (e.g., L2/3 VPN) 182 whereas the Network SDN Controller is the control/management entity 183 responsible for Layer 1 connectivity service. The CEs in Figure 2 184 are L2/3 devices that interface with L1 PE devices. 186 +----------+ 187 | Service | 188 | SDN | 189 |Controller| 190 |/EMS/NMS | 191 | for L2/3 | 192 +----------+ 193 | 194 | 195 | 196 +--------------------+ 197 | | 198 | +----------+ | 199 | | Network | | 200 | | SDN | | 201 | |Controller| | 202 | |/EMS/NMS | | 203 | | for L1VPN| | 204 | +----------+ | 205 | | 206 | | 207 +----+ +----+ +----+ +----+ +----+ 208 | CE |--------| PE |----| P |----| PE |------| CE | 209 +----+ +----+ +----+ +----+ +----+ 210 | | | | 211 | | | | 212 | +--------------------+ | 213 | | | | 214 | |<------------------>| | 215 | Provider Network | 216 | For Layer 1 | 217 |<------------------------------------------>| 218 Provider Network for L2/3 220 Figure 2: L1VPN SDN Controller/EMS/NMS-Based Service Model: Internal 221 Customer 223 The benefit is that the same layer 1 transport network resources are 224 shared by multiple services. A large capacity backbone network (data 225 plane) can be built economically by having the resources shared by 226 multiple services usually with flexibility to modify topologies, 227 while separating the control functions for each service department. 228 Thus, each customer can select a specific set of features that are 229 needed to provide their own service [RFC4847]. 231 1.2. Terminology 233 Refer to [RFC4847] and [RFC5253] for the key terms used in this 234 document. 236 The following terms are defined in [RFC7950] and are not redefined 237 here: 239 o client 241 o server 243 o augment 245 o data model 247 o data node 249 The following terms are defined in [RFC6241] and are not redefined 250 here: 252 o configuration data 254 o state data 256 The terminology for describing YANG data models is found in 257 [RFC7950]. 259 1.3. Tree Diagram 261 A simplified graphical representation of the data model is used in 262 Section 3 of this this document. The meaning of the symbols in these 263 diagrams is defined in [RFC8340]. 265 1.4. Prefixes in Data Node Names 267 In this document, names of data nodes and other data model objects 268 are prefixed using the standard prefix associated with the 269 corresponding YANG imported modules. The module ietf-layer1-types 270 specified in [I-D.ietf-ccamp-layer1-types] and ietf-yang-types 271 specified in [RFC6991] are imported in this module. 273 +-------------+-------------------+------------------------------+ 274 | Prefix | YANG module | Reference | 275 +-------------+-------------------+------------------------------+ 276 | l1csm | ietf-l1csm | [RFC XXXX] | 277 | l1-types | ietf-layer1-types |[I-D.ietf-ccamp-layer1-types] | 278 | yang | ietf-yang-types | [RFC6991] | 279 +-------------+-------------------+------------------------------+ 281 Note: The RFC Editor will replace XXXX with the number assigned to 282 the RFC once this document becomes an RFC. 284 2. Definitions 286 L1VC Layer 1 Virtual Connection 288 SLS Service Level Specification 290 UNI User Network Interface 292 PE Provider Edge 294 CE Customer Edge 296 EP End Point 298 P Protocol 300 C Coding 302 O Optical Interface 304 3. L1CSM YANG Model (Tree Structure) 305 module: ietf-l1csm 306 +--rw l1-connectivity 307 +--rw access 308 | +--rw unis 309 | +--rw uni* [id] 310 | +--rw id string 311 | +--rw protocol? identityref 312 | +--rw coding? identityref 313 | +--rw optical-interface? identityref 314 +--rw services 315 +--rw service* [service-id] 316 +--rw service-id string 317 +--rw endpoint-1 318 | +--rw id string 319 | +--rw uni 320 | -> /l1-connectivity/access/unis/uni/id 321 +--rw endpoint-2 322 | +--rw id string 323 | +--rw uni 324 | -> /l1-connectivity/access/unis/uni/id 325 +--rw start-time? yang:date-and-time 326 +--rw time-interval? int32 327 +--rw performance-metric* identityref 329 4. L1CSM YANG Code 331 file "ietf-l1csms@2020-03-09.yang" 332 module ietf-l1csm { 333 yang-version 1.1; 334 namespace "urn:ietf:params:xml:ns:yang:ietf-l1csm"; 335 prefix "l1csm"; 337 import ietf-yang-types { 338 prefix "yang"; 339 } 341 import ietf-layer1-types { 342 prefix "l1-types"; 343 } 345 organization 346 "Internet Engineering Task Force (IETF) CCAMP WG"; 348 contact 349 "Editor: Y. Lee (younglee.tx@gmail.com) 350 Editor: K. Lee (kwangkoog.lee@kt.com) 351 Editor: H. Zheng (zhenghaomian@huawei.com) 352 Editor: D. Dhody (dhruv.ietf@gmail.com) 353 Editor: O. G. de-Dios (oscar.gonzalezdedios@telefonica.com) 354 Editor: D. Ceccarelli (daniele.ceccarelli@ericsson.com)"; 356 description 357 "This module describes L1 connectivity service based on MEF 63: 358 Subscriber Layer 1 Service Attribute Technical Specification. 359 Refer to MEF 63 for all terms and the original references 360 used in the module. 362 Copyright (c) 2020 IETF Trust and the persons identified as 363 authors of the code. All rights reserved. 364 Redistribution and use in source and binary forms, with or 365 without modification, is permitted pursuant to, and subject 366 to the license terms contained in, the Simplified BSD 367 License set forth in Section 4.c of the IETF Trust's Legal 368 Provisions Relating to IETF Documents 369 (http://trustee.ietf.org/license-info). 371 This version of this YANG module is part of RFC XXXX; see 372 the RFC itself for full legal notices."; 374 revision "2020-03-09" { 375 description "Initial revision."; 376 reference "RFC XXXX: A Yang Data Model for L1 Connectivity 377 Service Model (L1CSM)"; 378 // Note: The RFC Editor will replace XXXX with the number 379 // assigned to the RFC once this document becomes an RFC. 380 } 382 grouping protocol-coding-optical-interface { 383 description 384 "describes where p:protocol type; c:coding 385 function; o:optical interface function"; 386 reference "MEF 63"; 387 leaf protocol { 388 type identityref { 389 base "l1-types:client-signal"; 390 } 391 description 392 "List of physical layer L1VC client protocol"; 394 } 395 leaf coding { 396 type identityref { 397 base "l1-types:coding-func"; 398 } 399 description "coding function"; 400 } 402 leaf optical-interface { 403 type identityref { 404 base "l1-types:optical-interface-func"; 405 } 406 description "optical-interface-function"; 407 } 409 } 411 grouping subscriber-l1vc-sls-service-attribute { 412 description 413 "The value of the Subscriber L1VC SLS (Service Level 414 Specification) Service Attribute"; 415 reference "MEF 63"; 417 leaf start-time { 418 type yang:date-and-time; 419 description "a time that represent the date and time 420 for the start of the SLS"; 421 } 423 leaf time-interval { 424 type int32; 425 units seconds; 426 description 427 "a time interval (e.g., 2,419,200 seconds which is 28 days) 428 that is used in conjunction wuth time-start to specify a 429 contiguous sequence of time intervals T for determining 430 when performance objectives are met."; 431 } 433 leaf-list performance-metric { 434 type identityref { 435 base "l1-types:service-performance-metric"; 436 } 437 description "list of service performance metric."; 438 } 440 } 442 grouping subscriber-l1vc-endpoint-attributes { 443 description 444 "subscriber layer 1 connection endpoint attributes"; 445 reference "MEF 63"; 447 container endpoint-1 { 448 description "One end of UNI id's - string and id"; 449 leaf id { 450 type string; 451 mandatory true; 452 description "subscriber end point ID of one end"; 453 } 455 leaf uni { 456 type leafref { 457 path "/l1-connectivity/access/unis/uni/id"; 458 } 459 mandatory true; 460 description "this is one end of subscriber L1VC end point 461 ID value = UNI-1"; 462 } 463 } 464 container endpoint-2 { 465 description "One end of UNI id's - string and id"; 466 leaf id { 467 type string; 468 mandatory true; 469 description "subscriber end point ID of the other end"; 470 } 472 leaf uni { 473 type leafref { 474 path "/l1-connectivity/access/unis/uni/id"; 475 } 476 mandatory true; 477 description 478 "this is one other end of subscriber L1VC end point 479 ID value = UNI-2"; 480 } 481 } 482 } 484 container l1-connectivity { 485 description 486 "serves as a top-level container for a list of layer 1 487 connection services (l1cs)"; 489 container access { 490 description "UNI configurations for access networks"; 492 container unis { 493 description "the list of UNI's to be configured"; 495 list uni { 496 key "id"; 497 description "UNI identifier"; 498 leaf id { 499 type string; 500 description "the UNI id of UNI Service Attributes"; 501 } 503 uses protocol-coding-optical-interface; 504 } 505 } 506 } 508 container services { 509 description "L1VC services"; 510 list service { 511 key "service-id"; 512 description 513 "an unique identifier of a subscriber L1VC service"; 515 leaf service-id { 516 type string; 517 mandatory true; 518 description "a unique service identifier for 519 subscriber L1VC."; 520 } 522 uses subscriber-l1vc-endpoint-attributes; 523 uses subscriber-l1vc-sls-service-attribute; 525 }//end of service list 526 } //end of service container 527 }//service top container 528 } 530 532 5. JSON Example 534 This section provides a JSON example of the YANG module described in 535 Section 4. This example configures one L1VC service with two UNIs 536 that describe the UNI endpoints. The service is configured with the 537 starting time to be 06:06:09 on 2018-09-13 for the service life time 538 of 2419200 seconds (which is corresponds to 28 days). In addition, 539 the service is configured to collect one performance metric, One-way- 540 Delay. 542 { 543 "l1-connectivity": { 544 "access": { 545 "unis": { 546 "uni": [ 547 { 548 "id": "MTL-HQ-Node3-Slot2-Port1", 549 "protocol": "ETH-10GigE_LAN ", 550 "coding": "ETH-10GR-PCS-49 ", 551 "optical_interface": "LR-PMD-clause-52 " 552 }, 553 { 554 "id": "MTL-STL-Node5-Slot4-Port3", 555 "protocol": "ETH-10GigE_LAN ", 556 "coding": "ETH-10GR-PCS-49 ", 557 "optical_interface": "ER-PMD-clause-52 " 558 } 559 ] 560 }, 561 }, 562 "services": { 563 "service": [ 564 { 565 "service-id": "Sub-L1VC-1867-LT-MEGAMART", 566 "endpoint-1": 567 { 568 "id": "MTL-HQ_1867-MEGAMART", 569 "uni": "MTL-HQ-Node3-Slot2-Port1" 570 }, 571 "endpoint-2": 572 { 573 "id": "MTL-STL_1867-MEGAMART", 574 "uni": "MTL-STL-Node5-Slot4-Port3" 575 }, 576 "start-time": "2018-09-13T06:06:09Z", 577 "time-interval": 2419200, 578 "performance-metric": "One-way-Delay " 579 } 580 ] 581 }, 582 } 584 6. Security Considerations 586 The YANG module specified in this document defines a schema for data 587 that is designed to be accessed via network management protocols such 588 as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF layer 589 is the secure transport layer, and the mandatory-to-implement secure 590 transport is Secure Shell (SSH) [RFC6242]. The lowest RESTCONF layer 591 is HTTPS, and the mandatory-to-implement secure transport is TLS 592 [RFC8446]. 594 The NETCONF access control model [RFC8341] provides the means to 595 restrict access for particular NETCONF or RESTCONF users to a 596 preconfigured subset of all available NETCONF or RESTCONF protocol 597 operations and content. 599 A number of configuration data nodes defined in this document are 600 writable/deletable (i.e., "config true") These data nodes may be 601 considered sensitive or vulnerable in some network environments. 603 These are the subtrees and data nodes and their sensitivity/ 604 vulnerability: 606 unis: 608 - id 610 Service: 612 - service-id 614 - endpoint-1 616 - endpoint-2 618 - start-time 620 - time-interval 622 - performance-metric 624 The security considerations spelled out in the YANG 1.1 specification 625 [RFC7950] apply for this document as well. 627 7. IANA Considerations 629 It is proposed that IANA should assign new URIs from the "IETF XML 630 Registry" [RFC3688] as follows: 632 URI: urn:ietf:params:xml:ns:yang:ietf-l1csm 633 Registrant Contact: The IESG 634 XML: N/A; the requested URI is an XML namespace. 636 This document registers following YANG modules in the YANG Module 637 Names registry [RFC7950]. 639 name: ietf-l1csm 640 namespace: urn:ietf:params:xml:ns:yang:ietf-l1csm 641 prefix: l1csm 642 reference: RFC XXXX 644 8. Acknowledgements 646 The authors would like to thank Tom Petch for his helpful comments 647 and valuable contributions and Robert Wilton for his review that 648 improved the model significantly. 650 9. Contributors 652 Italo Busi 653 Huawei Technologies 654 Email: Italo.Busi@huawei.com 656 Giuseppe Fioccola 657 Huawei Technologies 658 Email: giuseppe.fioccola@huawei.com 660 10. References 662 10.1. Normative References 664 [MEF63] Metro Ethernet Forum, "Subscriber Layer1 Service 665 Attributes Technical Specification", MEF 63, August 2018. 667 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, 668 DOI 10.17487/RFC3688, January 2004, 669 . 671 [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., 672 and A. Bierman, Ed., "Network Configuration Protocol 673 (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, 674 . 676 [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure 677 Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, 678 . 680 [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", 681 RFC 6991, DOI 10.17487/RFC6991, July 2013, 682 . 684 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", 685 RFC 7950, DOI 10.17487/RFC7950, August 2016, 686 . 688 [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF 689 Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, 690 . 692 [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", 693 BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, 694 . 696 [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration 697 Access Control Model", STD 91, RFC 8341, 698 DOI 10.17487/RFC8341, March 2018, 699 . 701 [RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., 702 and R. Wilton, "Network Management Datastore Architecture 703 (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018, 704 . 706 [RFC8446] Rescorla, E., "The Transport Layer Security (TLS) Protocol 707 Version 1.3", RFC 8446, DOI 10.17487/RFC8446, August 2018, 708 . 710 10.2. Informative References 712 [I-D.ietf-ccamp-layer1-types] 713 Zheng, H. and I. Busi, "A YANG Data Model for Layer 1 714 Types", draft-ietf-ccamp-layer1-types-04 (work in 715 progress), December 2019. 717 [RFC4847] Takeda, T., Ed., "Framework and Requirements for Layer 1 718 Virtual Private Networks", RFC 4847, DOI 10.17487/RFC4847, 719 April 2007, . 721 [RFC5253] Takeda, T., Ed., "Applicability Statement for Layer 1 722 Virtual Private Network (L1VPN) Basic Mode", RFC 5253, 723 DOI 10.17487/RFC5253, July 2008, 724 . 726 [RFC8199] Bogdanovic, D., Claise, B., and C. Moberg, "YANG Module 727 Classification", RFC 8199, DOI 10.17487/RFC8199, July 728 2017, . 730 [RFC8309] Wu, Q., Liu, W., and A. Farrel, "Service Models 731 Explained", RFC 8309, DOI 10.17487/RFC8309, January 2018, 732 . 734 Authors' Addresses 736 Young Lee 737 Samsung 738 Samsung 739 Seoul 740 South Korea 742 Email: younglee.tx@gmail.com 744 KwangKoog Lee 745 Korea Telecom 746 South Korea 748 Email: kwangkoog.lee@kt.com 750 Haomian Zheng 751 Huawei Technologies 752 H1-1-A043S Huawei Industrial Base, Songshanhu 753 Dongguan, Guangdong 523808 754 China 756 Email: zhenghaomian@huawei.com 758 Dhruv Dhody 759 Huawei Technologies 760 India 762 Email: dhruv.ietf@gmail.com 763 Oscar Gonzalez de Dios 764 Telefonica 766 Email: oscar.gonzalezdedios@telefonica.com 768 Daniele Ceccarelli 769 Ericsson 771 Email: daniele.ceccarelli@ericsson.com