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Found 'MAY NOT' in this paragraph: Note that receivers MAY NOT be already up and running when the configuration of the subscription takes effect on the monitored device. The first message MUST be a separate subscription-started notification to indicate the Receiver that the stream has started flowing. Then, the notifications can be sent immediately without delay. All the subscription state notifications, as defined in [RFC8639], MUST be encapsulated in separate notification messages. -- The document date (2 November 2020) is 1242 days in the past. Is this intentional? 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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 NETCONF G. Zheng 3 Internet-Draft T. Zhou 4 Intended status: Standards Track Huawei 5 Expires: 6 May 2021 T. Graf 6 Swisscom 7 P. Francois 8 INSA-Lyon 9 P. Lucente 10 NTT 11 2 November 2020 13 UDP-based Transport for Configured Subscriptions 14 draft-ietf-netconf-udp-notif-01 16 Abstract 18 This document describes an UDP-based notification mechanism to 19 collect data from networking devices. A shim header is proposed to 20 facilitate the streaming of data directly from line cards to a 21 collector. The objective is to rely on a lightweight approach to 22 allow for higher frequency and better transit performance compared to 23 already established notification mechanisms. 25 Requirements Language 27 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 28 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 29 document are to be interpreted as described in RFC 2119 [RFC2119]. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at https://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on 6 May 2021. 48 Copyright Notice 50 Copyright (c) 2020 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 55 license-info) in effect on the date of publication of this document. 56 Please review these documents carefully, as they describe your rights 57 and restrictions with respect to this document. Code Components 58 extracted from this document must include Simplified BSD License text 59 as described in Section 4.e of the Trust Legal Provisions and are 60 provided without warranty as described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 65 2. Configured Subscription to UDP-Notif . . . . . . . . . . . . 4 66 3. UDP-Based Transport . . . . . . . . . . . . . . . . . . . . . 4 67 3.1. Design Overview . . . . . . . . . . . . . . . . . . . . . 4 68 3.2. Format of the UDP-Notif Message Header . . . . . . . . . 5 69 3.3. Options . . . . . . . . . . . . . . . . . . . . . . . . . 6 70 3.3.1. Segmentation Option . . . . . . . . . . . . . . . . . 7 71 3.4. Data Encoding . . . . . . . . . . . . . . . . . . . . . . 8 72 4. Applicability . . . . . . . . . . . . . . . . . . . . . . . . 8 73 4.1. Congestion Control . . . . . . . . . . . . . . . . . . . 8 74 4.2. Message Size . . . . . . . . . . . . . . . . . . . . . . 9 75 4.3. Reliability . . . . . . . . . . . . . . . . . . . . . . . 9 76 5. A YANG Data Model for Management of UDP-Notif . . . . . . . . 9 77 6. YANG Module . . . . . . . . . . . . . . . . . . . . . . . . . 10 78 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 79 8. Security Considerations . . . . . . . . . . . . . . . . . . . 13 80 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13 81 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 82 10.1. Normative References . . . . . . . . . . . . . . . . . . 13 83 10.2. Informative References . . . . . . . . . . . . . . . . . 15 84 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 15 86 1. Introduction 88 Sub-Notif [RFC8639] defines a mechanism that lets a collector 89 subscribe to the publication of YANG-defined data maintained in a 90 YANG [RFC7950] datastore. The mechanism separates the management and 91 control of subscriptions from the transport used to deliver the data. 92 Three transport mechanisms, namely NETCONF transport [RFC8640], 93 RESTCONF transport [RFC8650], and HTTPS transport 94 [I-D.ietf-netconf-https-notif] have been defined so far for such 95 notification messages. 97 While powerful in their features and general in their architecture, 98 the currently available transport mechanisms need to be complemented 99 to support data publications at high velocity from devices that 100 feature a distributed architecture. The currently available 101 transports are based on TCP and lack the efficiency needed to 102 continuously send notifications at high velocity. 104 This document specifies a transport option for Sub-Notif that 105 leverages UDP. Specifically, it facilitates the distributed data 106 collection mechanism described in 107 [I-D.ietf-netconf-distributed-notif]. In the case of data 108 originating from multiple line cards, centralized designs require 109 data to be internally forwarded from those line cards to the push 110 server, presumably on a route processor, which then combines the 111 individual data items into a single consolidated stream. The 112 centralized data collection mechanism can result in a performance 113 bottleneck, especially when large amounts of data are involved. 115 What is needed is the support for a mechanism that allows for 116 directly pushing multiple substreams, e.g. one from each line card, 117 without passing them through an additional processing stage for 118 internal consolidation. The proposed UDP-based transport allows for 119 such a distributed data collection approach. 121 * Firstly, a UDP approach reduces the burden of maintaining a large 122 amount of active TCP connections at the collector, notably in 123 cases where it collects data from the line cards of a large amount 124 of networking devices. 126 * Secondly, as no connection state needs to be maintained, UDP 127 encapsulation can be easily implemented by the hardware of the 128 publication streamer, which will further improve performance. 130 * Ultimately, such advantages allow for a larger data analysis 131 feature set, as more voluminous, finer grained data sets can be 132 streamed to the collector. 134 The transport described in this document can be used for transmitting 135 notification messages over both IPv4 and IPv6. 137 This document describes the notification mechanism. It is intended 138 to be used in conjunction with [RFC8639], extended by 139 [I-D.ietf-netconf-distributed-notif]. 141 Section 2 describes the control of the proposed transport mechanism. 142 Section 3 details the notification mechanism and message format. 143 Section 4.1 discusses congestion control. Section 4 covers the 144 applicability of the proposed mechanism. 146 2. Configured Subscription to UDP-Notif 148 This section describes how the proposed mechanism can be controlled 149 using subscription channels based on NETCONF or RESTCONF. 151 Following the usual approach of Sub-Notif, configured subscriptions 152 contain the location information of all the receivers, including the 153 IP address and the port number, so that the publisher can actively 154 send UDP-Notif messages to the corresponding receivers. 156 Note that receivers MAY NOT be already up and running when the 157 configuration of the subscription takes effect on the monitored 158 device. The first message MUST be a separate subscription-started 159 notification to indicate the Receiver that the stream has started 160 flowing. Then, the notifications can be sent immediately without 161 delay. All the subscription state notifications, as defined in 162 [RFC8639], MUST be encapsulated in separate notification messages. 164 3. UDP-Based Transport 166 In this section, we specify the UDP-Notif Transport behaviour. 167 Section 3.1 describes the general design of the solution. 168 Section 3.2 specifies the UDP-Notif message format. Section 3.3 169 describes a generic optional sub TLV format. Section 3.3.1 uses such 170 options to provide a segmentation solution for large UDP-Notif 171 message payloads. Section 3.4 describes the encoding of the message 172 payload. 174 3.1. Design Overview 176 As specified in Sub-Notif, the telemetry data is encapsulated in the 177 NETCONF/RESTCONF notification message, which is then encapsulated and 178 carried using transport protocols such as TLS or HTTP2. Figure 1 179 illustrates the the structure of an UDP-Notif message. 181 * The Message Header contains information that facilitate the 182 message transmission before deserializing the notification 183 message. 185 * Notification Message is the encoded content that the publication 186 stream transports. The common encoding methods include, CBOR 187 [RFC7049], JSON, and XML. 188 [I-D.ietf-netconf-notification-messages] describes the structure 189 of the Notification Message for single notifications and bundled 190 notifications. 192 +-------+ +--------------+ +--------------+ 193 | UDP | | Message | | Notification | 194 | | | Header | | Message | 195 +-------+ +--------------+ +--------------+ 197 Figure 1: UDP-Notif Message Overview 199 3.2. Format of the UDP-Notif Message Header 201 The UDP-Notif Message Header contains information that facilitate the 202 message transmission before deserializing the notification message. 203 The data format is shown in Figure 2. 205 0 1 2 3 206 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 207 +-----+-+-------+---------------+-------------------------------+ 208 | Ver |S| ET | Header Len | Message Length | 209 +-----+-+-------+---------------+-------------------------------+ 210 | Observation-Domain-ID | 211 +---------------------------------------------------------------+ 212 | Message-ID | 213 +---------------------------------------------------------------+ 214 ~ Options ~ 215 +---------------------------------------------------------------+ 217 Figure 2: UDP-Notif Message Header Format 219 The Message Header contains the following field: 221 * Ver represents the PDU (Protocol Data Unit) encoding version. The 222 initial version value is 0. 224 * S represents the space of encoding type specified in the ET field. 225 When S is unset, ET represents the standard encoding types as 226 defined in this document. When S is set, ET represents a private 227 space to be freely used for non standard encodings. 229 * ET is a 4 bit identifier to indicate the encoding type used for 230 the Notification Message. 16 types of encoding can be expressed. 231 When the S bit is unset, the following values apply: 233 - 0: CBOR; 235 - 1: JSON; 237 - 2: XML; 238 - others are reserved. 240 * Header Len is the length of the message header in octets, 241 including both the fixed header and the options. 243 * Message Length is the total length of the message within one UDP 244 datagram, measured in octets, including the message header. 246 * Observation-Domain-ID is a 32-bit identifier of the Observation 247 Domain that led to the production of the notification message, as 248 defined in [I-D.ietf-netconf-notification-messages]. This allows 249 disambiguation of an information source, such as the 250 identification of different line cards sending the notification 251 messages. The source IP address of the UDP datagrams SHOULD NOT 252 be interpreted as the identifier for the host that originated the 253 UDP-Notif message. Indeed, the streamer sending the UDP-Notif 254 message could be a relay for the actual source of data carried 255 within UDP-Notif messages. 257 * The Message ID is generated continuously by the sender of UDP- 258 Notif messages. Different subscribers share the same Message ID 259 sequence. 261 * Options is a variable-length field in the TLV format. When the 262 Header Length is larger than 12 octets, which is the length of the 263 fixed header, Options TLVs follow directly after the fixed message 264 header (i.e., Message ID). The details of the options are 265 described in the following section. 267 3.3. Options 269 All the options are defined with the following format, illustrated in 270 Figure 3. 272 0 1 2 3 273 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 274 +---------------+---------------+-------------------------------- 275 | Type | Length | Variable-length data 276 +---------------+---------------+-------------------------------- 278 Figure 3: Generic Option Format 280 * Type: 1 octet describing the option type; 282 * Length: 1 octet representing the total number of octets in the 283 TLV, including the Type and Length fields; 285 * Variable-length data: 0 or more octets of TLV Value. 287 3.3.1. Segmentation Option 289 The UDP payload length is limited to 65535. Application level 290 headers will make the actual payload shorter. Even though binary 291 encodings such as CBOR may not require more space than what is left, 292 more voluminous encodings such as JSON and XML may suffer from this 293 size limitation. Although IPv4 and IPv6 senders can fragment 294 outgoing packets exceeding their Maximum Transmission Unit(MTU), 295 fragmented IP packets may not be desired for operational and 296 performance reasons. 298 Consequently, implementations of the mechanism SHOULD provide a 299 configurable max-segment-size option to control the maximum size of a 300 payload. 302 0 1 2 3 303 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 304 +---------------+---------------+-----------------------------+-+ 305 | Type | Length | Segment Number |L| 306 +---------------+---------------+-----------------------------+-+ 308 Figure 4: Segmentation Option Format 310 The Segmentation Option is to be included when the message content is 311 segmented into multiple pieces. Different segments of one message 312 share the same Message ID. An illustration is provided in Figure 4. 313 The fields of this TLV are: 315 * Type: Generic option field which indicates a Segmentation Option. 316 The Type value is to be asigned. 318 * Length: Generic option field which indicates the length of this 319 option. It is a fixed value of 4 octets for the Segmentation 320 Option. 322 * Segment Number: 15-bit value indicating the sequence number of the 323 current segment. The first segment of a segmented message has a 324 Segment Number value of 0. 326 * L: is a flag to indicate whether the current segment is the last 327 one of the message. When 0 is set, the current segment is not the 328 last one. When 1 is set, the current segment is the last one, 329 meaning that the total number of segments used to transport this 330 message is the value of the current Segment Number + 1. 332 An implementation of this specification MUST NOT rely on IP 333 fragmentation by default to carry large messages. An implementation 334 of this specification MUST either restrict the size of individual 335 messages carried over this protocol, or support the segmentation 336 option. 338 3.4. Data Encoding 340 UDP-Notif message data can be encoded in CBOR, XML or JSON format. 341 It is conceivable that additional encodings may be supported in the 342 future. This can be accomplished by augmenting the subscription data 343 model with additional identity statements used to refer to requested 344 encodings. 346 Implementation MAY support multiple encoding methods per 347 subscription. When bundled notifications are supported between the 348 publisher and the receiver, only subscribed notifications with the 349 same encoding can be bundled in a given message. 351 4. Applicability 353 In this section, we provide an applicability statement for the 354 proposed mechanism, following the recommendations of [RFC8085]. 356 The proposed mechanism falls in the category of UDP applications 357 "designed for use within the network of a single network operator or 358 on networks of an adjacent set of cooperating network operators, to 359 be deployed in controlled environments". Implementations of the 360 proposed mechanism should thus follow the recommendations in place 361 for such specific applications. In the following, we discuss 362 recommendations on congestion control, message size guildelines, 363 reliability considerations. 365 4.1. Congestion Control 367 The proposed application falls into the category of applications 368 performing transfer of large amounts of data. It is expected that 369 the operator using the solution configures QoS on its related flows. 370 As per [RFC8085], such applications MAY choose not to implement any 371 form of congestion control, but follow the following principles. 373 It is NOT RECOMMENDED to use the proposed mechanism over congestion- 374 sensitive network paths. The only environments where UDP-Notif is 375 expected to be used are managed networks. The deployments require 376 that the network path has been explicitly provisioned to handle the 377 traffic through traffic engineering mechanisms, such as rate limiting 378 or capacity reservations. 380 Implementation of the proposal SHOULD NOT push unlimited amounts of 381 traffic by default, and SHOULD require the users to explicitely 382 configure such a mode of operation. 384 Burst mitigation through packet pacing is RECOMMENDED. Disabling 385 burst mitigation SHOULD require the users to explicitely configure 386 such a mode of operation. 388 Applications SHOULD monitor packet losses and provide means to the 389 user for retrieving information on such losses. The UDP-Notif 390 Message ID can be used to deduce congestion based on packet loss 391 detection. Hence the collector can notify the device to use a lower 392 streaming rate. The interaction to control the streaming rate on the 393 device is out of the scope of this document. 395 4.2. Message Size 397 [RFC8085] recommends not to rely on IP fragmentation for messages 398 whose size result in IP packets exceeding the MTU along the path. 399 The segmentation option of the current specification permits to 400 perform segmentation of the UDP Notif message content so as to not 401 have to rely on IP fragmentation. Implementation of the current 402 specification SHOULD allow for the configuration of the MTU. 404 4.3. Reliability 406 The target application for UDP-Notif is the collection of data-plane 407 information. The lack of reliability of the data streaming mechanism 408 is thus considered acceptable as the mechanism is to be used in 409 controlled environments, mitigating the risk of information loss, 410 while allowing for publication of very large amounts of data. 411 Moreover, in this context, sporadic events when incomplete data 412 collection is provided is not critical for the proper management of 413 the network, as information collected for the devices through the 414 means of the proposed mechanism is to be often refreshed. 416 A collector implementation for this protocol SHOULD deal with 417 potential loss of packets carrying a part of segmented payload, by 418 discarding packets that were actually received, but cannot be re- 419 assembled as a complete message within a given amount of time. This 420 time SHOULD be configurable. 422 5. A YANG Data Model for Management of UDP-Notif 424 The YANG model defined in Section 9 has two leafs augmented into one 425 place of Sub-Notif [RFC8639], plus one identity. 427 module: ietf-udp-subscribed-notifications 428 augment /sn:subscriptions/sn:subscription/sn:receivers/sn:receiver: 429 +--rw address inet:ip-address 430 +--rw port inet:port-number 431 +--rw enable-fragment? boolean 432 +--rw max-fragment-size? uint32 434 6. YANG Module 436 file "ietf-udp-notif@2020-04-27.yang" 437 module ietf-udp-notif { 438 yang-version 1.1; 439 namespace 440 "urn:ietf:params:xml:ns:yang:ietf-udp-notif"; 441 prefix un; 442 import ietf-subscribed-notifications { 443 prefix sn; 444 reference 445 "RFC 8639: Subscription to YANG Notifications"; 446 } 447 import ietf-inet-types { 448 prefix inet; 449 reference 450 "RFC 6991: Common YANG Data Types"; 451 } 453 organization "IETF NETCONF (Network Configuration) Working Group"; 454 contact 455 "WG Web: 456 WG List: 458 Authors: Guangying Zheng 459 460 Tianran Zhou 461 462 Thomas Graf 463 464 Pierre Francois 465 466 Paolo Lucente 467 "; 469 description 470 "Defines UDP-Notif as a supported transport for subscribed 471 event notifications. 473 Copyright (c) 2018 IETF Trust and the persons identified as authors 474 of the code. All rights reserved. 476 Redistribution and use in source and binary forms, with or without 477 modification, is permitted pursuant to, and subject to the license 478 terms contained in, the Simplified BSD License set forth in Section 479 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents 480 (https://trustee.ietf.org/license-info). 482 This version of this YANG module is part of RFC XXXX; see the RFC 484 itself for full legal notices."; 486 revision 2020-04-27 { 487 description 488 "Initial version"; 489 reference 490 "RFC XXXX: UDP-based Notifications for Streaming Telemetry"; 491 } 493 identity udp-notif { 494 base sn:transport; 495 description 496 "UDP-Notif is used as transport for notification messages 497 and state change notifications."; 498 } 500 identity encode-cbor { 501 base sn:encoding; 502 description 503 "Encode data using CBOR as described in RFC 7049."; 504 reference 505 "RFC 7049: Concise Binary Object Representation"; 506 } 508 grouping target-receiver { 509 description 510 "Provides a reusable description of a UDP-Notif target receiver."; 511 leaf address { 512 type inet:ip-address; 513 mandatory true; 514 description 515 "IP address of target UDP-Notif receiver, which can be an 516 IPv4 address or an IPV6 address."; 517 } 518 leaf port { 519 type inet:port-number; 520 mandatory true; 521 description 522 "Port number of target UDP-Notif receiver, if not specified, 523 the system should use default port number."; 524 } 526 leaf enable-fragment { 527 type boolean; 528 default false; 529 description 530 "The switch for the fragment feature. When disabled, the 531 publisher will not allow fragment for a very large data"; 532 } 534 leaf max-fragment-size { 535 when "../enable-fragment = true"; 536 type uint32; 537 description "UDP-Notif provides a configurable max-fragment-size 538 to control the size of each message."; 539 } 540 } 542 augment "/sn:subscriptions/sn:subscription/sn:receivers/sn:receiver" { 543 description 544 "This augmentation allows UDP-Notif specific parameters to be 545 exposed for a subscription."; 546 uses target-receiver; 547 } 548 } 549 551 7. IANA Considerations 553 This RFC requests that IANA assigns one UDP port number in the 554 "Registered Port Numbers" range with the service name "udp-notif". 555 This port will be the default port for the UDP-based notification 556 Streaming Telemetry (UDP-Notif) for NETCONF and RESTCONF. Below is 557 the registration template following the rules of [RFC6335]. 559 Service Name: udp-notif 561 Transport Protocol(s): UDP 563 Assignee: IESG 565 Contact: IETF Chair 567 Description: UDP-based Publication Streaming Telemetry 569 Reference: RFC XXXX 570 Port Number: PORT-X 572 IANA is requested to assign a new URI from the IETF XML Registry 573 [RFC3688]. The following URI is suggested: 575 URI: urn:ietf:params:xml:ns:yang:ietf-udp-notif 576 Registrant Contact: The IESG. 577 XML: N/A; the requested URI is an XML namespace. 579 This document also requests a new YANG module name in the YANG Module 580 Names registry [RFC7950] with the following suggestion: 582 name: ietf-udp-notif 583 namespace: urn:ietf:params:xml:ns:yang:ietf-udp-notif 584 prefix: un 585 reference: RFC XXXX 587 8. Security Considerations 589 TBD 591 9. Acknowledgements 593 The authors of this documents would like to thank Alexander Clemm, 594 Eric Voit, Huiyang Yang, Kent Watsen, Mahesh Jethanandani, Stephane 595 Frenot, Timothy Carey, Tim Jenkins, and Yunan Gu for their 596 constructive suggestions for improving this document. 598 10. References 600 10.1. Normative References 602 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 603 Requirement Levels", BCP 14, RFC 2119, 604 DOI 10.17487/RFC2119, March 1997, 605 . 607 [RFC2914] Floyd, S., "Congestion Control Principles", BCP 41, 608 RFC 2914, DOI 10.17487/RFC2914, September 2000, 609 . 611 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, 612 DOI 10.17487/RFC3688, January 2004, 613 . 615 [RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 616 Security", RFC 4347, DOI 10.17487/RFC4347, April 2006, 617 . 619 [RFC5234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax 620 Specifications: ABNF", STD 68, RFC 5234, 621 DOI 10.17487/RFC5234, January 2008, 622 . 624 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 625 (TLS) Protocol Version 1.2", RFC 5246, 626 DOI 10.17487/RFC5246, August 2008, 627 . 629 [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., 630 and A. Bierman, Ed., "Network Configuration Protocol 631 (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, 632 . 634 [RFC6335] Cotton, M., Eggert, L., Touch, J., Westerlund, M., and S. 635 Cheshire, "Internet Assigned Numbers Authority (IANA) 636 Procedures for the Management of the Service Name and 637 Transport Protocol Port Number Registry", BCP 165, 638 RFC 6335, DOI 10.17487/RFC6335, August 2011, 639 . 641 [RFC6347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer 642 Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347, 643 January 2012, . 645 [RFC7049] Bormann, C. and P. Hoffman, "Concise Binary Object 646 Representation (CBOR)", RFC 7049, DOI 10.17487/RFC7049, 647 October 2013, . 649 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", 650 RFC 7950, DOI 10.17487/RFC7950, August 2016, 651 . 653 [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF 654 Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, 655 . 657 [RFC8085] Eggert, L., Fairhurst, G., and G. Shepherd, "UDP Usage 658 Guidelines", BCP 145, RFC 8085, DOI 10.17487/RFC8085, 659 March 2017, . 661 [RFC8639] Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard, 662 E., and A. Tripathy, "Subscription to YANG Notifications", 663 RFC 8639, DOI 10.17487/RFC8639, September 2019, 664 . 666 [RFC8640] Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard, 667 E., and A. Tripathy, "Dynamic Subscription to YANG Events 668 and Datastores over NETCONF", RFC 8640, 669 DOI 10.17487/RFC8640, September 2019, 670 . 672 [RFC8650] Voit, E., Rahman, R., Nilsen-Nygaard, E., Clemm, A., and 673 A. Bierman, "Dynamic Subscription to YANG Events and 674 Datastores over RESTCONF", RFC 8650, DOI 10.17487/RFC8650, 675 November 2019, . 677 10.2. Informative References 679 [I-D.ietf-netconf-distributed-notif] 680 Zhou, T., Zheng, G., Voit, E., Graf, T., and P. Francois, 681 "Subscription to Distributed Notifications", Work in 682 Progress, Internet-Draft, draft-ietf-netconf-distributed- 683 notif-01, June 2020, . 686 [I-D.ietf-netconf-https-notif] 687 Jethanandani, M. and K. Watsen, "An HTTPS-based Transport 688 for Configured Subscriptions", Work in Progress, Internet- 689 Draft, draft-ietf-netconf-https-notif-04, 27 July 2020, 690 . 693 [I-D.ietf-netconf-notification-messages] 694 Voit, E., Jenkins, T., Birkholz, H., Bierman, A., and A. 695 Clemm, "Notification Message Headers and Bundles", Work in 696 Progress, Internet-Draft, draft-ietf-netconf-notification- 697 messages-08, 17 November 2019, . 701 Authors' Addresses 702 Guangying Zheng 703 Huawei 704 101 Yu-Hua-Tai Software Road 705 Nanjing 706 Jiangsu, 707 China 709 Email: zhengguangying@huawei.com 711 Tianran Zhou 712 Huawei 713 156 Beiqing Rd., Haidian District 714 Beijing 715 China 717 Email: zhoutianran@huawei.com 719 Thomas Graf 720 Swisscom 721 Binzring 17 722 CH- Zuerich 8045 723 Switzerland 725 Email: thomas.graf@swisscom.com 727 Pierre Francois 728 INSA-Lyon 729 Lyon 730 France 732 Email: pierre.francois@insa-lyon.fr 734 Paolo Lucente 735 NTT 736 Siriusdreef 70-72 737 Hoofddorp, WT 2132 738 Netherlands 740 Email: paolo@ntt.net