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'XPATH' == Outdated reference: A later version (-36) exists of draft-ietf-netconf-netconf-client-server-06 -- Obsolete informational reference (is this intentional?): RFC 7540 (Obsoleted by RFC 9113) Summary: 1 error (**), 0 flaws (~~), 8 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 NETCONF E. Voit 3 Internet-Draft Cisco Systems 4 Intended status: Standards Track A. Clemm 5 Expires: February 4, 2019 Huawei 6 A. Gonzalez Prieto 7 Microsoft 8 E. Nilsen-Nygaard 9 A. Tripathy 10 Cisco Systems 11 August 3, 2018 13 Customized Subscriptions to a Publisher's Event Streams 14 draft-ietf-netconf-subscribed-notifications-15 16 Abstract 18 This document defines a YANG data model and associated mechanisms 19 enabling subscriber-specific subscriptions to a publisher's event 20 streams. Applying these elements allows a subscriber to request for 21 and receive a continuous, custom feed of publisher generated 22 information. 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 February 4, 2019. 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 59 1.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 3 60 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 61 1.3. Solution Overview . . . . . . . . . . . . . . . . . . . . 5 62 1.4. Relationship to RFC-5277 . . . . . . . . . . . . . . . . 6 63 2. Solution . . . . . . . . . . . . . . . . . . . . . . . . . . 6 64 2.1. Event Streams . . . . . . . . . . . . . . . . . . . . . . 7 65 2.2. Event Stream Filters . . . . . . . . . . . . . . . . . . 7 66 2.3. QoS . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 67 2.4. Dynamic Subscriptions . . . . . . . . . . . . . . . . . . 9 68 2.5. Configured Subscriptions . . . . . . . . . . . . . . . . 16 69 2.6. Event Record Delivery . . . . . . . . . . . . . . . . . . 24 70 2.7. Subscription State Notifications . . . . . . . . . . . . 25 71 2.8. Subscription Monitoring . . . . . . . . . . . . . . . . . 30 72 2.9. Advertisement . . . . . . . . . . . . . . . . . . . . . . 31 73 3. YANG Data Model Trees . . . . . . . . . . . . . . . . . . . . 31 74 3.1. Event Streams Container . . . . . . . . . . . . . . . . . 31 75 3.2. Filters Container . . . . . . . . . . . . . . . . . . . . 32 76 3.3. Subscriptions Container . . . . . . . . . . . . . . . . . 32 77 4. Data Model . . . . . . . . . . . . . . . . . . . . . . . . . 34 78 5. Considerations . . . . . . . . . . . . . . . . . . . . . . . 61 79 5.1. IANA Considerations . . . . . . . . . . . . . . . . . . . 61 80 5.2. Implementation Considerations . . . . . . . . . . . . . . 62 81 5.3. Transport Requirements . . . . . . . . . . . . . . . . . 62 82 5.4. Security Considerations . . . . . . . . . . . . . . . . . 63 83 6. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 67 84 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 67 85 7.1. Normative References . . . . . . . . . . . . . . . . . . 67 86 7.2. Informative References . . . . . . . . . . . . . . . . . 69 87 Appendix A. Example Configured Transport Augmentation . . . . . 70 88 Appendix B. Changes between revisions . . . . . . . . . . . . . 72 89 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 76 91 1. Introduction 93 This document defines a YANG data model and associated mechanisms 94 enabling subscriber-specific subscriptions to a publisher's event 95 streams. Effectively this enables a 'subscribe then publish' 96 capability where the customized information needs and access 97 permissions of each target receiver are understood by the publisher 98 before subscribed event records are marshaled and pushed. The 99 receiver then gets a continuous, custom feed of publisher generated 100 information. 102 While the functionality defined in this document is transport- 103 agnostic, transports like NETCONF [RFC6241] or RESTCONF [RFC8040] can 104 be used to configure or dynamically signal subscriptions, and there 105 are bindings defined for subscribed event record delivery for NETCONF 106 within [I-D.draft-ietf-netconf-netconf-event-notifications], and for 107 HTTP2 or HTTP1.1 within [I-D.draft-ietf-netconf-restconf-notif]. 109 The YANG model in this document conforms to the Network Management 110 Datastore Architecture defined in [RFC8342]. 112 1.1. Motivation 114 Various limitations in [RFC5277] are discussed in [RFC7923]. 115 Resolving these issues is the primary motivation for this work. Key 116 capabilities supported by this document include: 118 o multiple subscriptions on a single transport session 120 o support for dynamic and configured subscriptions 122 o modification of an existing subscription in progress 124 o per-subscription operational counters 126 o negotiation of subscription parameters (through the use of hints 127 returned as part of declined subscription requests) 129 o subscription state change notifications (e.g., publisher driven 130 suspension, parameter modification) 132 o independence from transport 134 1.2. Terminology 136 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 137 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 138 "OPTIONAL" in this document are to be interpreted as described in BCP 139 14 [RFC2119] [RFC8174] when, and only when, they appear in all 140 capitals, as shown here. 142 Client: defined in [RFC8342]. 144 Configuration: defined in [RFC8342]. 146 Configuration datastore: defined in [RFC8342]. 148 Configured subscription: A subscription installed via configuration 149 into a configuration datastore. 151 Dynamic subscription: A subscription created dynamically by a 152 subscriber via a remote procedure call. 154 Event: An occurrence of something that may be of interest. Examples 155 include a configuration change, a fault, a change in status, crossing 156 a threshold, or an external input to the system. 158 Event occurrence time: a timestamp matching the time an originating 159 process identified as when an event happened. 161 Event record: A set of information detailing an event. 163 Event stream: A continuous, chronologically ordered set of events 164 aggregated under some context. 166 Event stream filter: Evaluation criteria which may be applied against 167 event records within an event stream. Event records pass the filter 168 when specified criteria are met. 170 Notification message: Information intended for a receiver indicating 171 that one or more event(s) have occurred. 173 Publisher: An entity responsible for streaming notification messages 174 per the terms of a subscription. 176 Receiver: A target to which a publisher pushes subscribed event 177 records. For dynamic subscriptions, the receiver and subscriber are 178 the same entity. 180 Subscriber: A client able to request and negotiate a contract for the 181 generation and push of event records from a publisher. For dynamic 182 subscriptions, the receiver and subscriber are the same entity. 184 Subscription: A contract with a publisher, stipulating which 185 information one or more receivers wish to have pushed from the 186 publisher without the need for further solicitation. 188 All YANG tree diagrams used in this document follow the notation 189 defined in [RFC8340]. 191 1.3. Solution Overview 193 This document describes a transport agnostic mechanism for 194 subscribing to and receiving content from an event stream within a 195 publisher. This mechanism is through the use of a subscription. 197 Two types of subscriptions are supported: 199 1. Dynamic subscriptions, where a subscriber initiates a 200 subscription negotiation with a publisher via an RPC. If the 201 publisher is able to serve this request, it accepts it, and then 202 starts pushing notification messages back to the subscriber. If 203 the publisher is not able to serve it as requested, then an error 204 response is returned. This response MAY include hints at 205 subscription parameters that, had they been present, would have 206 enabled the dynamic subscription request to be accepted. 208 2. Configured subscriptions, which allow the management of 209 subscriptions via a configuration so that a publisher can send 210 notification messages to a receiver of a configured subscription. 211 Support for configured subscriptions is optional, with its 212 availability advertised via a YANG feature. 214 Additional characteristics differentiating configured from dynamic 215 subscriptions include: 217 o The lifetime of a dynamic subscription is bound by the transport 218 session used to establish it. For connection-oriented stateful 219 transports like NETCONF, the loss of the transport session will 220 result in the immediate termination of any associated dynamic 221 subscriptions. For connectionless or stateless transports like 222 HTTP, a lack of receipt acknowledgment of a sequential set of 223 notification messages and/or keep-alives can be used to trigger a 224 termination of a dynamic subscription. Contrast this to the 225 lifetime of a configured subscription. This lifetime is driven by 226 relevant configuration being present within the publisher's 227 applied configuration. Being tied to configuration operations 228 implies configured subscriptions can be configured to persist 229 across reboots, and implies a configured subscription can persist 230 even when its publisher is fully disconnected from any network. 232 o Configured subscriptions can be modified by any configuration 233 client with write permission on the configuration of the 234 subscription. Dynamic subscriptions can only be modified via an 235 RPC request made by the original subscriber, or a change to 236 configuration data referenced by the subscription. 238 Note that there is no mixing-and-matching of dynamic and configured 239 operations on a single subscription. Specifically, a configured 240 subscription cannot be modified or deleted using RPCs defined in this 241 document. Similarly, a subscription established via RPC cannot be 242 modified through configuration operations. Also note that transport 243 specific transport drafts based on this specification MUST detail the 244 life cycles of both dynamic and configured subscriptions. 246 A publisher MAY terminate a dynamic subscription at any time. 247 Similarly, it MAY decide to temporarily suspend the sending of 248 notification messages for any dynamic subscription, or for one or 249 more receivers of a configured subscription. Such termination or 250 suspension is driven by internal considerations of the publisher. 252 1.4. Relationship to RFC-5277 254 This document is intended to provide a superset of the subscription 255 capabilities initially defined within [RFC5277]. Especially when 256 extending an existing [RFC5277] implementation, it is important to 257 understand what has been reused and what has been replaced. Key 258 relationships between these two documents include: 260 o this document defines a transport independent capability, 261 [RFC5277] is specific to NETCONF. 263 o the data model in this document is used instead of the data model 264 in Section 3.4 of [RFC5277] for the new operations. 266 o the RPC operations in this draft replaces the operation "create- 267 subscription" defined in [RFC5277], section 4. 269 o the message of [RFC5277], Section 4 is used. 271 o the included contents of the "NETCONF" event stream are identical 272 between this document and [RFC5277]. 274 o a publisher MAY implement both the Notification Management Schema 275 and RPCs defined in [RFC5277] and this new document concurrently. 277 o unlike [RFC5277], this document enables a single transport session 278 to intermix of notification messages and RPCs for different 279 subscriptions. 281 2. Solution 283 Per the overview provided in Section 1.3, this section details the 284 overall context, state machines, and subsystems which may be 285 assembled to allow the subscription of events from a publisher. 287 2.1. Event Streams 289 An event stream is a named entity on a publisher which exposes a 290 continuously updating set of event records. Each event stream is 291 available for subscription. It is out of the scope of this document 292 to identify a) how streams are defined (other than the NETCONF 293 stream), b) how event records are defined/generated, and c) how event 294 records are assigned to streams. 296 There is only one reserved event stream name within this document: 297 "NETCONF". The "NETCONF" event stream contains all NETCONF XML event 298 record information supported by the publisher, except for the 299 subscription state notifications described in Section 2.7. Among 300 these included NETCONF XML event records are individual YANG 1.1 301 notifications described in section 7.16 of [RFC7950]. Each of these 302 YANG 1.1 notifications will be treated as a distinct event record. 303 Beyond the "NETCONF" stream, implementations MAY define additional 304 event streams. 306 As event records are created by a system, they may be assigned to one 307 or more streams. The event record is distributed to a subscription's 308 receiver(s) where: (1) a subscription includes the identified stream, 309 and (2) subscription filtering does not exclude the event record from 310 that receiver. 312 Access control permissions may be used to silently exclude event 313 records from within an event stream for which the receiver has no 314 read access. As an example of how this might be accomplished, see 315 [RFC8341] section 3.4.6. Note that per Section 2.7 of this document, 316 subscription state change notifications are never filtered out. 318 If no access control permissions are in place for event records on an 319 event stream, then a receiver MUST be allowed access to all the event 320 records. If subscriber permissions change during the lifecycle of a 321 subscription and event stream access is no longer permitted, then the 322 subscription MUST be terminated. 324 Event records MUST NOT be delivered to a receiver in a different 325 order than they were placed onto an event stream. 327 2.2. Event Stream Filters 329 This document defines an extensible filtering mechanism. The filter 330 itself is a boolean test which is placed on the content of an event 331 record. A 'false' filtering result causes the event message to be 332 excluded from delivery to a receiver. A filter never results in 333 information being stripped from within an event record prior to that 334 event record being encapsulated within a notification message. The 335 two optional event stream filtering syntaxes supported are [XPATH] 336 and subtree [RFC6241]. 338 If no event stream filter is provided within a subscription, all 339 event records on an event stream are to be sent. 341 2.3. QoS 343 This document provide for several QoS parameters. These parameters 344 indicate the treatment of a subscription relative to other traffic 345 between publisher and receiver. Included are: 347 o A "dscp" marking to differentiate prioritization of notification 348 messages during network transit. 350 o A "weighting" so that bandwidth proportional to this weighting can 351 be allocated to this subscription relative to other subscriptions 352 destined for that receiver. 354 o a "dependency" upon another subscription. 356 If the publisher supports the "dscp" feature, then a subscription 357 with a "dscp" leaf MUST result in a corresponding [RFC2474] DSCP 358 marking being placed within the IP header of any resulting 359 notification messages and subscription state change notifications. 361 For the "weighting" parameter, when concurrently dequeuing 362 notification messages from multiple subscriptions to a receiver, the 363 publisher MUST allocate bandwidth to each subscription proportionally 364 to the weights assigned to those subscriptions. "Weighting" is an 365 optional capability of the publisher; support for it is identified 366 via the "qos" feature. 368 If a subscription has the "dependency" parameter set, then any 369 buffered notification messages containing event records selected by 370 the parent subscription MUST be dequeued prior to the notification 371 messages of the dependent subscription. If notification messages 372 have dependencies on each other, the notification message queued the 373 longest MUST go first. If a "dependency" included within an RPC 374 references a subscription which does not exist or is no longer 375 accessible to that subscriber, that "dependency" MUST be silently 376 removed. "Dependency" is an optional capability of the publisher; 377 support for it is identified via the "qos" feature. 379 2.4. Dynamic Subscriptions 381 Dynamic subscriptions are managed via protocol operations (in the 382 form of [RFC7950], Section 7.14 RPCs) made against targets located 383 within the publisher. These RPCs have been designed extensibly so 384 that they may be augmented for subscription targets beyond event 385 streams. For examples of such augmentations, see the RPC 386 augmentations within [I-D.ietf-netconf-yang-push]'s YANG model. 388 2.4.1. Dynamic Subscription State Model 390 Below is the publisher's state machine for a dynamic subscription. 391 Each state is shown in its own box. It is important to note that 392 such a subscription doesn't exist at the publisher until an 393 "establish-subscription" RPC is accepted. The mere request by a 394 subscriber to establish a subscription is insufficient for that 395 subscription to be externally visible. Start and end states are 396 depicted to reflect subscription creation and deletion events. 398 ......... 399 : start : 400 :.......: 401 | 402 establish-subscription 403 | 404 | .-------modify-subscription--------. 405 v v | 406 .-----------. .-----------. 407 .--------. | receiver |--insufficient CPU, b/w-->| receiver | 408 modify- '| active | | suspended | 409 subscription | |<----CPU, b/w sufficient--| | 410 ---------->'-----------' '-----------' 411 | | 412 delete/kill-subscription delete/kill- 413 | subscription 414 v | 415 ......... | 416 : end :<---------------------------------' 417 :.......: 419 Figure 1: Publisher's state for a dynamic subscription 421 Of interest in this state machine are the following: 423 o Successful "establish-subscription" or "modify-subscription" RPCs 424 put the subscription into the active state. 426 o Failed "modify-subscription" RPCs will leave the subscription in 427 its previous state, with no visible change to any streaming 428 updates. 430 o A delete or kill RPC will end the subscription, as will the 431 reaching of a "stop-time". 433 o A publisher may choose to suspend a subscription when there is 434 insufficient CPU or bandwidth available to service the 435 subscription. This is notified to a subscriber with a 436 "subscription-suspended" state change notification. 438 o A suspended subscription may be modified by the subscriber (for 439 example in an attempt to use fewer resources). Successful 440 modification returns the subscription to an active state. 442 o Even without a "modify-subscription" request, a publisher may 443 return a subscription to the active state should the resource 444 constraints become sufficient again. This is announced to the 445 subscriber via the "subscription-resumed" subscription state 446 change notification. 448 2.4.2. Establishing a Dynamic Subscription 450 The "establish-subscription" RPC allows a subscriber to request the 451 creation of a subscription. The transport selected by the subscriber 452 to reach the publisher MUST be able to support multiple "establish- 453 subscription" requests made within the same transport session. 455 The input parameters of the operation are: 457 o A "stream" name which identifies the targeted event stream against 458 which the subscription is applied. 460 o An event stream filter which may reduce the set of event records 461 pushed. 463 o Where the transport used by the RPC supports multiple encodings, 464 an optional "encoding" for the event records pushed. Note: If no 465 "encoding" is included, the encoding of the RPC MUST be used. 467 o An optional "stop-time" for the subscription. If no "stop-time" 468 is present, notification messages will continue to be sent until 469 the subscription is terminated. 471 o An optional "start-time" for the subscription. The "start-time" 472 MUST be in the past and indicates that the subscription is 473 requesting a replay of previously generated information from the 474 event stream. For more on replay, see Section 2.4.2.1. Where 475 there is no "start-time", the subscription starts immediately. 477 If the publisher can satisfy the "establish-subscription" request, it 478 replies with an identifier for the subscription, and then immediately 479 starts streaming notification messages. 481 Below is a tree diagram for "establish-subscription". All objects 482 contained in this tree are described within the included YANG model 483 within Section 4. 485 +---x establish-subscription 486 +---w input 487 | +---w (target) 488 | | +--:(stream) 489 | | +---w (stream-filter)? 490 | | | +--:(by-reference) 491 | | | | +---w stream-filter-ref 492 | | | | stream-filter-ref 493 | | | +--:(within-subscription) 494 | | | +---w (filter-spec)? 495 | | | +--:(stream-subtree-filter) 496 | | | | +---w stream-subtree-filter? 497 | | | | {subtree}? 498 | | | +--:(stream-xpath-filter) 499 | | | +---w stream-xpath-filter? 500 | | | yang:xpath1.0 {xpath}? 501 | | +---w stream stream-ref 502 | | +---w replay-start-time? yang:date-and-time 503 | | {replay}? 504 | +---w stop-time? yang:date-and-time 505 | +---w dscp? inet:dscp {dscp}? 506 | +---w weighting? uint8 {qos}? 507 | +---w dependency? subscription-id {qos}? 508 | +---w encoding? encoding 509 +--ro output 510 +--ro identifier subscription-id 511 +--ro replay-start-time-revision? yang:date-and-time 512 {replay}? 514 Figure 2: establish-subscription RPC tree diagram 516 A publisher MAY reject the "establish-subscription" RPC for many 517 reasons as described in Section 2.4.6. The contents of the resulting 518 RPC error response MAY include details on input parameters which if 519 considered in a subsequent "establish-subscription" RPC, may result 520 in a successful subscription establishment. Any such hints MUST be 521 transported within a yang-data "establish-subscription-stream-error- 522 info" container included within the RPC error response. 524 yang-data establish-subscription-stream-error-info 525 +--ro establish-subscription-stream-error-info 526 +--ro reason? identityref 527 +--ro filter-failure-hint? string 529 Figure 3: establish-subscription RPC yang-data tree diagram 531 2.4.2.1. Requesting a replay of event records 533 Replay provides the ability to establish a subscription which is also 534 capable of passing recently generated event records. In other words, 535 as the subscription initializes itself, it sends any previously 536 generated content from within the target event stream which meets the 537 filter and timeframe criteria. The end of these historical event 538 records is identified via a "replay-completed" state change 539 notification. Any event records generated since the subscription 540 establishment may then follow. For a particular subscription, all 541 event records will be delivered in the order they are placed into the 542 stream. 544 Replay is an optional feature which is dependent on an event stream 545 supporting some form of logging. This document puts no restrictions 546 on the size or form of the log, where it resides within the 547 publisher, or when event record entries in the log are purged. 549 The inclusion of a "replay-start-time" within an "establish- 550 subscription" RPC indicates a replay request. If the "replay-start- 551 time" contains a value that is earlier than what a publisher's 552 retained history supports, then if the subscription is accepted, the 553 actual publisher's revised start time MUST be set in the returned 554 "replay-start-time-revision" object. 556 A "stop-time" parameter may be included in a replay subscription. 557 For a replay subscription, the "stop-time" MAY be earlier than the 558 current time, but MUST be later than the "replay-start-time". 560 If the time the replay starts is later than the time marked within 561 any event records retained within the replay buffer, then the 562 publisher MUST send a "replay-completed" notification immediately 563 after a successful establish-subscription RPC response. 565 If an event stream supports replay, the "replay-support" leaf is 566 present in the "/streams/stream" list entry for the stream. An event 567 stream that does support replay is not expected to have an unlimited 568 supply of saved notifications available to accommodate any given 569 replay request. To assess the timeframe available for replay, 570 subscribers can read the leafs "replay-log-creation-time" and 571 "replay-log-aged-time". See Figure 18 for the YANG tree, and 572 Section 4 for the YANG model describing these elements. The actual 573 size of the replay log at any given time is a publisher specific 574 matter. Control parameters for the replay log are outside the scope 575 of this document. 577 2.4.3. Modifying a Dynamic Subscription 579 The "modify-subscription" operation permits changing the terms of an 580 existing dynamic subscription. Dynamic subscriptions can be modified 581 any number of times. If the publisher accepts the requested 582 modifications, it acknowledges success to the subscriber, then 583 immediately starts sending event records based on the new terms. 585 Subscriptions created by configuration cannot be modified via this 586 RPC. However configuration may be used to modify objects referenced 587 by the subscription (such as a referenced filter). 589 Below is a tree diagram for "modify-subscription". All objects 590 contained in this tree are described within the included YANG model 591 within Section 4. 593 +---x modify-subscription 594 +---w input 595 +---w identifier subscription-id 596 +---w (target) 597 | +--:(stream) 598 | +---w (stream-filter)? 599 | +--:(by-reference) 600 | | +---w stream-filter-ref 601 | | stream-filter-ref 602 | +--:(within-subscription) 603 | +---w (filter-spec)? 604 | +--:(stream-subtree-filter) 605 | | +---w stream-subtree-filter? 606 | | {subtree}? 607 | +--:(stream-xpath-filter) 608 | +---w stream-xpath-filter? 609 | yang:xpath1.0 {xpath}? 610 +---w stop-time? yang:date-and-time 612 Figure 4: modify-subscription RPC tree diagram 614 If the publisher accepts the requested modifications on a currently 615 suspended subscription, the subscription will immediately be resumed 616 (i.e., the modified subscription is returned to the active state.) 617 The publisher MAY immediately suspend this newly modified 618 subscription through the "subscription-suspended" notification before 619 any event records are sent. 621 If the publisher rejects the RPC request, the subscription remains as 622 prior to the request. That is, the request has no impact whatsoever. 623 Rejection of the RPC for any reason is indicated by via RPC error as 624 described in Section 2.4.6. The contents of such a rejected RPC MAY 625 include hints on inputs which (if considered) may result in a 626 successfully modified subscription. These hints MUST be transported 627 within a yang-data "modify-subscription-stream-error-info" container 628 inserted into the RPC error response. 630 Below is a tree diagram for "modify-subscription-RPC-yang-data". All 631 objects contained in this tree are described within the included YANG 632 model within Section 4. 634 yang-data modify-subscription-stream-error-info 635 +--ro modify-subscription-stream-error-info 636 +--ro reason? identityref 637 +--ro filter-failure-hint? string 639 Figure 5: modify-subscription RPC yang-data tree diagram 641 2.4.4. Deleting a Dynamic Subscription 643 The "delete-subscription" operation permits canceling an existing 644 subscription. If the publisher accepts the request, and the 645 publisher has indicated success, the publisher MUST NOT send any more 646 notification messages for this subscription. If the delete request 647 matches a known subscription established on the same transport 648 session, then it MUST be deleted; otherwise it MUST be rejected with 649 no changes to the publisher. 651 Below is a tree diagram for "delete-subscription". All objects 652 contained in this tree are described within the included YANG model 653 within Section 4. 655 +---x delete-subscription 656 +---w input 657 +---w identifier subscription-id 659 Figure 6: delete-subscription RPC tree diagram 661 Dynamic subscriptions can only be deleted via this RPC using the same 662 transport session previously used for subscription establishment. 663 Configured subscriptions cannot be deleted using RPCs. 665 2.4.5. Killing a Dynamic Subscription 667 The "kill-subscription" operation permits an operator to end a 668 dynamic subscription which is not associated with the transport 669 session used for the RPC. A publisher MUST terminate any dynamic 670 subscription identified by RPC request. 672 Configured subscriptions cannot be killed using this RPC. Instead, 673 configured subscriptions are deleted as part of regular configuration 674 operations. Publishers MUST reject any RPC attempt to kill a 675 configured subscription. 677 Below is a tree diagram for "kill-subscription". All objects 678 contained in this tree are described within the included YANG model 679 within Section 4. 681 +---x kill-subscription 682 +---w input 683 +---w identifier subscription-id 685 Figure 7: kill-subscription RPC tree diagram 687 2.4.6. RPC Failures 689 Whenever an RPC is unsuccessful, the publisher returns relevant 690 information as part of the RPC error response. Transport level error 691 processing MUST be done before RPC error processing described in this 692 section. In all cases, RPC error information returned will use 693 existing transport layer RPC structures, such as those seen with 694 NETCONF in [RFC6241] Appendix A, or with RESTCONF in [RFC8040] 695 Section 7.1. These structures MUST be able to encode subscription 696 specific errors identified below and defined within this document's 697 YANG model. 699 As a result of this mixture, how subscription errors are encoded 700 within an RPC error response is transport dependent. Following are 701 valid errors which can occur for each RPC: 703 establish-subscription modify-subscription 704 ---------------------- ------------------- 705 dscp-unavailable filter-unsupported 706 encoding-unsupported insufficient-resources 707 filter-unsupported no-such-subscription 708 history-unavailable 709 insufficient-resources 710 replay-unsupported 712 delete-subscription kill-subscription 713 ---------------------- ---------------------- 714 no-such-subscription no-such-subscription 716 To see a NETCONF based example of an error response from above, see 717 [I-D.draft-ietf-netconf-netconf-event-notifications], Figure 10. 719 There is one final set of transport independent RPC error elements 720 included in the YANG model. These are the following three yang-data 721 structures for failed event stream subscriptions: 723 1. "establish-subscription-stream-error-info": This MUST be returned 724 if an RPC error reason has not been placed elsewhere within the 725 transport portion of a failed "establish-subscription" RPC 726 response. This MUST be sent if hints on how to overcome the RPC 727 error are included. 729 2. "modify-subscription-stream-error-info": This MUST be returned if 730 an RPC error reason has not been placed elsewhere within the 731 transport portion of a failed "modify-subscription" RPC response. 732 This MUST be sent if hints on how to overcome the RPC error are 733 included. 735 3. "delete-subscription-error-info": This MUST be returned if an RPC 736 error reason has not been placed elsewhere within the transport 737 portion of a failed "delete-subscription" or "kill-subscription" 738 RPC response. 740 2.5. Configured Subscriptions 742 A configured subscription is a subscription installed via 743 configuration. Configured subscriptions may be modified by any 744 configuration client with the proper permissions. Subscriptions can 745 be modified or terminated via configuration at any point of their 746 lifetime. Multiple configured subscriptions MUST be supportable over 747 a single transport session. 749 Configured subscriptions have several characteristics distinguishing 750 them from dynamic subscriptions: 752 o persistence across publisher reboots, 754 o persistence even when transport is unavailable, and 756 o an ability to send notification messages to more than one receiver 757 (note that receivers are unaware of the existence of any other 758 receivers.) 760 On the publisher, supporting configured subscriptions is optional and 761 advertised using the "configured" feature. On a receiver of a 762 configured subscription, support for dynamic subscriptions is 763 optional except where replaying missed event records is required. 765 In addition to the subscription parameters available to dynamic 766 subscriptions described in Section 2.4.2, the following additional 767 parameters are also available to configured subscriptions: 769 o A "transport" which identifies the transport protocol to use to 770 connect with all subscription receivers. 772 o One or more receivers, each intended as the destination for event 773 records. Note that each individual receiver is identifiable by 774 its "name". Via this "name", publisher transport parameters must 775 be defined in order to establish and maintain a transport 776 connection with a receiver. This transport specific reference can 777 come in several forms, including the augmentation of leafrefs to 778 an actual transport instance. Such augmentations must be defined 779 in transport specific specifications building upon this document. 781 o Optional parameters to identify where traffic should egress a 782 publisher: 784 * A "source-interface" which identifies the egress interface to 785 use from the publisher. Publisher support for this is optional 786 and advertised using the "interface-designation" feature. 788 * A "source-address" address, which identifies the IP address to 789 stamp on notification messages destined for the receiver. 791 * A "source-vrf" which identifies the VRF on which to reach 792 receivers. This VRF is a network instance as defined within 793 [I-D.draft-ietf-rtgwg-ni-model]. Publisher support for VRFs is 794 optional and advertised using the "supports-vrf" feature. 796 If none of the above parameters are set, notification messages 797 MUST egress the publisher's default interface. 799 A tree diagram describing these parameters is shown in Figure 20 800 within Section 3.3. All parameters are described within the YANG 801 model in Section 4. 803 2.5.1. Configured Subscription State Model 805 Below is the state machine for a configured subscription on the 806 publisher. This state machine describes the three states (valid, 807 invalid, and concluded), as well as the transitions between these 808 states. Start and end states are depicted to reflect configured 809 subscription creation and deletion events. The creation or 810 modification of a configured subscription initiates an evaluation by 811 the publisher to determine if the subscription is in valid or invalid 812 states. The publisher uses its own criteria in making this 813 determination. If in the valid state, the subscription becomes 814 operational. See (1) in the diagram below. 816 ......... 817 : start :-. 818 :.......: | 819 create .---modify-----.----------------------------------. 820 | | | | 821 V V .-------. ....... .---------. 822 .----[evaluate]--no--->|invalid|-delete->: end :<-delete-|concluded| 823 | '-------' :.....: '---------' 824 |-[evaluate]--no-(2). ^ ^ ^ 825 | ^ | | | | 826 yes | '->unsupportable delete stop-time 827 | modify (subscription- (subscription- (subscription- 828 | | terminated*) terminated*) concluded*) 829 | | | | | 830 (1) | (3) (4) (5) 831 | .---------------------------------------------------------------. 832 '-->| valid | 833 '---------------------------------------------------------------' 835 Legend: 836 dotted boxes: subscription added or removed via configuration 837 dashed boxes: states for a subscription 838 [evaluate]: decision point on whether the subscription is supportable 839 (*): resulting subscription state change notification 841 Figure 8: Publisher state model for a configured subscription 843 A subscription in the valid state may move to the invalid state in 844 one of two ways. First, it may be modified in a way which fails a 845 re-evaluation. See (2) in the diagram. Second, the publisher might 846 determine that the subscription is no longer supportable. This could 847 be for reasons of an unexpected but sustained increase in an event 848 stream's event records, degraded CPU capacity, a more complex 849 referenced filter, or other higher priority subscriptions which have 850 usurped resources. See (3) in the diagram. No matter the case, a 851 "subscription-terminated" notification is sent to any receivers in an 852 active or suspended state. A subscription in the valid state may 853 also transition to the concluded state via (5) if a configured stop 854 time has been reached. In this case, a "subscription-concluded" 855 notification is sent to any receivers in active or suspended states. 856 Finally, a subscription may be deleted by configuration (4). 858 When a subscription is in the valid state, a publisher will attempt 859 to connect with all receivers of a configured subscription and 860 deliver notification messages. Below is the state machine for each 861 receiver of a configured subscription. This receiver state machine 862 is fully contained within the state machine of the configured 863 subscription, and is only relevant when the configured subscription 864 is in the valid state. 866 .-----------------------------------------------------------------. 867 | valid | 868 | .----------. .--------. | 869 | | receiver |---timeout---------------->|receiver| | 870 | |connecting|<----------------reset--(c)|timeout | | 871 | | |<-transport '--------' | 872 | '----------' loss,reset------------------------------. | 873 | (a) | | | 874 | subscription- (b) (b) | 875 | started* .--------. .---------. | 876 | '----->| |(d)-insufficient CPU,------->| | | 877 | |receiver| buffer overflow |receiver | | 878 | subscription-| active | |suspended| | 879 | modified* | |<----CPU, b/w sufficient,-(e)| | | 880 | '---->'--------' subscription-modified* '---------' | 881 '-----------------------------------------------------------------' 883 Legend: 884 dashed boxes which include the word 'receiver' show the possible 885 states for an individual receiver of a valid configured subscription. 886 * indicates a state change notification 888 Figure 9: Receiver state for a configured subscription on a Publisher 890 When a configured subscription first moves to the valid state, the 891 "state" leaf of each receiver is initialized to "connecting". If 892 transport connectivity is not available to any receiver and there are 893 any notification messages to deliver, a transport session is 894 established (e.g., through [RFC8071]). Individual receivers are 895 moved to the active state when a "subscription-started" state change 896 notification is successfully passed to that receiver (a). Event 897 records are only sent to active receivers. Receivers of a configured 898 subscription remain active if both transport connectivity can be 899 verified to the receiver, and event records are not being dropped due 900 to a publisher buffer overflow. The result is that a receiver will 901 remain active on the publisher as long as events aren't being lost, 902 or the receiver cannot be reached. In addition, a configured 903 subscription's receiver MUST be moved to connecting if transport 904 connectivity cannot be achieved, or if the receiver is reset via the 905 "reset" action (b), (c). For more on reset, see Section 2.5.5. 907 A configured subscription's receiver MUST be moved to the suspended 908 state if there is transport connectivity between the publisher and 909 receiver, but notification messages are failing to be delivered due 910 to publisher buffer overflow, or notification messages are not able 911 to be generated for that receiver due to insufficient CPU (d). This 912 is indicated to the receiver by the "subscription-suspended" state 913 change notification. 915 A configured subscription receiver MUST be returned to the active 916 state from the suspended state when notification messages are able to 917 be generated, bandwidth is sufficient to handle the notification 918 messages, and a receiver has successfully been sent a "subscription- 919 resumed" or "subscription-modified" state change notification (e). 920 The choice as to which of these two state change notifications is 921 sent is determined by whether the subscription was modified during 922 the period of suspension. 924 Modification of a configured subscription is possible at any time. A 925 "subscription-modified" state change notification will be sent to all 926 active receivers, immediately followed by notification messages 927 conforming to the new parameters. Suspended receivers will also be 928 informed of the modification. However this notification will await 929 the end of the suspension for that receiver (e). 931 The mechanisms described above are mirrored in the RPCs and 932 notifications within the document. It should be noted that these 933 RPCs and notifications have been designed to be extensible and allow 934 subscriptions into targets other than event streams. For instance, 935 the YANG module defined in Section 5 of [I-D.ietf-netconf-yang-push] 936 augments "/sn:modify-subscription/sn:input/sn:target". 938 2.5.2. Creating a Configured Subscription 940 Configured subscriptions are established using configuration 941 operations against the top-level "subscriptions" subtree. 943 Because there is no explicit association with an existing transport 944 session, configuration operations MUST include additional parameters 945 beyond those of dynamic subscriptions to indicate each receiver, how 946 to contact that receiver, and possibly whether the notification 947 messages need to come from a specific egress interface on the 948 publisher. Some of these parameters MUST be configured via transport 949 specific augmentations to this specification." 951 After a subscription is successfully established, the publisher 952 immediately sends a "subscription-started" state change notification 953 to each receiver. It is quite possible that upon configuration, 954 reboot, or even steady-state operations, a transport session may not 955 be currently available to the receiver. In this case, when there is 956 something to transport for an active subscription, transport specific 957 call-home operations will be used to establish the connection. When 958 transport connectivity is available, notification messages may then 959 be pushed. 961 With active configured subscriptions, it is allowable to buffer event 962 records even after a "subscription-started" has been sent. However 963 if events are lost (rather than just delayed) due to replay buffer 964 overflow, a new "subscription-started" must be sent. This new 965 "subscription-started" indicates an event record discontinuity. 967 To see an example of subscription creation using configuration 968 operations over NETCONF, see Appendix A of 969 [I-D.draft-ietf-netconf-netconf-event-notifications]. 971 Note that is possible to configure replay on a configured 972 subscription. This capability is to allow a configured subscription 973 to exist on a system so that event records generated during and 974 following boot can be buffered and pushed as soon as the transport 975 session is established. 977 2.5.3. Modifying a Configured Subscription 979 Configured subscriptions can be modified using configuration 980 operations against the top-level "subscriptions" subtree. 982 If the modification involves adding receivers, added receivers are 983 placed in the connecting state. If a receiver is removed, the state 984 change notification "subscription-terminated" is sent to that 985 receiver if that receiver is active or suspended. 987 If the modification involves changing the policies for the 988 subscription, the publisher sends to currently active receivers a 989 "subscription-modified" notification. For any suspended receivers, a 990 "subscription-modified" notification will be delayed until the 991 receiver is resumed. (Note: in this case, the "subscription- 992 modified" notification informs the receiver that the subscription has 993 been resumed, so no additional "subscription-resumed" need be sent. 994 Also note that if multiple modifications have occurred during the 995 suspension, only the latest one need be sent to the receiver.) 997 2.5.4. Deleting a Configured Subscription 999 Subscriptions can be deleted through configuration against the top- 1000 level "subscriptions" subtree. 1002 Immediately after a subscription is successfully deleted, the 1003 publisher sends to all receivers of that subscription a state change 1004 notification stating the subscription has ended (i.e., "subscription- 1005 terminated"). 1007 2.5.5. Resetting a Configured Subscription Receiver 1009 It is possible that a configured subscription to a receiver needs to 1010 be reset. This is accomplished via the "reset" action within the 1011 YANG model at "/subscriptions/subscription/receivers/receiver/reset". 1012 This re-initialization may be useful in cases where a publisher has 1013 timed out trying to reach a receiver. When such a reset occurs, a 1014 transport session will be initiated if necessary, and a new 1015 "subscription-started" notification will be sent. This action does 1016 not have any effect on transport connectivity if the needed 1017 connectivity already exists. 1019 2.5.6. Replay for a Configured Subscription 1021 It is possible to do replay on a configured subscription. This is 1022 supported via the configuration of the "configured-replay" object on 1023 the subscription. The setting of this object enables the streaming 1024 of the buffered events for the subscribed stream. All buffered event 1025 which have been retained since the last publisher restart will be 1026 sent. 1028 Replay of events records created since restart is useful. It allows 1029 event records generated before transport connectivity establishment 1030 to be passed to a receiver. Setting the restart time as the earliest 1031 configured replay time precludes possibility of resending of event 1032 records logged prior to publisher restart. It also ensures the same 1033 records will be sent to each configured receiver, regardless of the 1034 speed of transport connectivity establishment to each receiver. 1035 Finally, establishing restart as the earliest potential time for 1036 event records to be included within notification messages, a well- 1037 understood timeframe for replay is defined. 1039 As a result, when any configured subscription receivers become 1040 active, buffered event records will be sent immediately after the 1041 "subscription-started" notification. The leading event record sent 1042 will be the first event record subsequent to the latest of three 1043 different times: the "replay-log-creation-time", "replay-log-aged- 1044 time", or the most recent publisher boot time. The "replay-log- 1045 creation-time" and "replay-log-aged-time" are discussed in 1046 Section 2.4.2.1. The most recent publisher boot time ensures that 1047 duplicate event records are not replayed from a previous time the 1048 publisher was booted. 1050 It is quite possible that a receiver might want to retrieve event 1051 records from a stream prior to the latest boot. If such records 1052 exist where there is a configured replay, the publisher MUST send the 1053 time of the event record immediately preceding the "replay-start- 1054 time" within the "replay-previous-event-time" leaf. Through the 1055 existence of the "replay-previous-event-time", the receiver will know 1056 that earlier events prior to reboot exist. In addition, if the 1057 subscriber was previously receiving event records with the same 1058 subscription id, the receiver can determine if there was a timegap 1059 where records generated on the publisher were not successully 1060 received. And with this information, the receiver may choose to 1061 dynamically subscribe to retrieve any event records placed into the 1062 stream before the most recent boot time. 1064 All other replay functionality remains the same as with dynamic 1065 subscriptions as described in Section 2.4.2.1. 1067 2.5.7. Transport Connectivity for a Configured Subscription 1069 This specification is transport independent. However supporting a 1070 configured subscription will often require the establishment of 1071 transport connectivity. And the parameters used for this transport 1072 connectivity establishment happen to be transport specific. As a 1073 result, the YANG model defined within Section 4 is not able to 1074 directly define these transport parameters. 1076 It is necessary to support the connection establishment process. To 1077 support this function, the YANG model does include a node where 1078 transport specific parameters may be augmented into the model. This 1079 node is the choice "transport" located under 1080 "/subscriptions/subscription/receivers/receiver". By augmenting YANG 1081 case entries under this node, system developers are able to 1082 incorporate the YANG objects necessary to support the transport 1083 connectivity establishment process. 1085 Any implementation of this specification where the optional feature 1086 "configured" is supported MUST augment the YANG model with at least 1087 one transport specific YANG case under the choice "transport". For 1088 more information and an example on how this might be accomplished see 1089 Appendix A. 1091 2.6. Event Record Delivery 1093 Whether dynamic or configured, once a subscription has been set up, 1094 the publisher streams event records via notification messages per the 1095 terms of the subscription. For dynamic subscriptions, notification 1096 messages are sent over the session used to establish the 1097 subscription. For configured subscriptions, notification messages 1098 are sent over the connections specified by the transport and each 1099 receiver of a configured subscription. 1101 A notification message is sent to a receiver when an event record is 1102 not blocked by either the specified filter criteria or receiver 1103 permissions. This notification message MUST be encoded in a 1104 message as defined within [RFC5277], Section 4. And 1105 per [RFC5277]'s "eventTime" object definition, the "eventTime" is 1106 populated with the event occurrence time. 1108 The following example within [RFC7950] section 7.16.3 is an example 1109 of a compliant message: 1111 1113 2007-09-01T10:00:00Z 1114 1115 so-1/2/3.0 1116 up 1117 down 1118 1119 1121 Figure 10: subscribed notification message 1123 When a dynamic subscription has been started or modified, with 1124 "establish-subscription" or "modify-subscription" respectively, event 1125 records matching the newly applied filter criteria MUST NOT be sent 1126 until after the RPC reply has been sent. 1128 When a configured subscription has been started or modified, event 1129 records matching the newly applied filter criteria MUST NOT be sent 1130 until after the "subscription-started" or "subscription-modified" 1131 notifications has been sent, respectively. 1133 2.7. Subscription State Notifications 1135 In addition to sending event records to receivers, a publisher MUST 1136 also send subscription state notifications when events related to 1137 subscription management have occurred. 1139 Subscription state notifications are unlike other notifications in 1140 that they are never included in any stream. Instead, they are 1141 inserted (as defined in this section) within the sequence of 1142 notification messages sent to a particular receiver. Subscription 1143 state notifications cannot be filtered out, they cannot be stored in 1144 replay buffers, and they are delivered only to impacted receivers of 1145 a subscription. The identification of subscription state 1146 notifications is easy to separate from other notification messages 1147 through the use of the YANG extension "subscription-state-notif". 1148 This extension tags a notification as a subscription state 1149 notification. 1151 The complete set of subscription state notifications is described in 1152 the following subsections. 1154 2.7.1. subscription-started 1156 This notification indicates that a configured subscription has 1157 started, and event records may be sent. Included in this state 1158 change notification are all the parameters of the subscription, 1159 except for the receiver(s) transport connection information and 1160 origin information indicating where notification messages will egress 1161 the publisher. Note that if a referenced filter from the "filters" 1162 container has been used within the subscription, the notification 1163 still provides the contents of that referenced filter under the 1164 "within-subscription" subtree. 1166 Note that for dynamic subscriptions, no "subscription-started" 1167 notifications are ever sent. 1169 Below is a tree diagram for "subscription-started". All objects 1170 contained in this tree are described within the included YANG model 1171 within Section 4. 1173 +---n subscription-started {configured}? 1174 +--ro identifier 1175 | subscription-id 1176 +--ro (target) 1177 | +--:(stream) 1178 | +--ro (stream-filter)? 1179 | | +--:(by-reference) 1180 | | | +--ro stream-filter-ref 1181 | | | stream-filter-ref 1182 | | +--:(within-subscription) 1183 | | +--ro (filter-spec)? 1184 | | +--:(stream-subtree-filter) 1185 | | | +--ro stream-subtree-filter? 1186 | | | {subtree}? 1187 | | +--:(stream-xpath-filter) 1188 | | +--ro stream-xpath-filter? yang:xpath1.0 1189 | | {xpath}? 1190 | +--ro stream stream-ref 1191 | +--ro replay-start-time? 1192 | | yang:date-and-time {replay}? 1193 | +--ro replay-previous-event-time? 1194 | yang:date-and-time {replay}? 1195 +--ro stop-time? 1196 | yang:date-and-time 1197 +--ro dscp? inet:dscp 1198 | {dscp}? 1199 +--ro weighting? uint8 {qos}? 1200 +--ro dependency? 1201 | subscription-id {qos}? 1202 +--ro transport transport 1203 | {configured}? 1204 +--ro encoding? encoding 1205 +--ro purpose? string 1206 {configured}? 1208 Figure 11: subscription-started notification tree diagram 1210 2.7.2. subscription-modified 1212 This notification indicates that a subscription has been modified by 1213 configuration operations. It is delivered directly after the last 1214 event records processed using the previous subscription parameters, 1215 and before any event records processed after the modification. 1217 Below is a tree diagram for "subscription-modified". All objects 1218 contained in this tree are described within the included YANG model 1219 within Section 4. 1221 +---n subscription-modified 1222 +--ro identifier subscription-id 1223 +--ro (target) 1224 | +--:(stream) 1225 | +--ro (stream-filter)? 1226 | | +--:(by-reference) 1227 | | | +--ro stream-filter-ref stream-filter-ref 1228 | | +--:(within-subscription) 1229 | | +--ro (filter-spec)? 1230 | | +--:(stream-subtree-filter) 1231 | | | +--ro stream-subtree-filter? 1232 | | | {subtree}? 1233 | | +--:(stream-xpath-filter) 1234 | | +--ro stream-xpath-filter? yang:xpath1.0 1235 | | {xpath}? 1236 | +--ro stream stream-ref 1237 | +--ro replay-start-time? yang:date-and-time 1238 | {replay}? 1239 +--ro stop-time? yang:date-and-time 1240 +--ro dscp? inet:dscp {dscp}? 1241 +--ro weighting? uint8 {qos}? 1242 +--ro dependency? subscription-id {qos}? 1243 +--ro transport transport {configured}? 1244 +--ro encoding? encoding 1245 +--ro purpose? string {configured}? 1247 Figure 12: subscription-modified notification tree diagram 1249 A publisher most often sends this notification directly after the 1250 modification of any configuration parameters impacting a configured 1251 subscription. But it may also be sent at two other times: 1253 1. Where a configured subscription has been modified during the 1254 suspension of a receiver, the notification will be delayed until 1255 the receiver's suspension is lifted. In this situation, the 1256 notification indicates that the subscription has been both 1257 modified and resumed. 1259 2. While this state change will most commonly be used with 1260 configured subscriptions, with dynamic subscriptions, there is 1261 also one time this notification will be sent. A "subscription- 1262 modified" state change notification MUST be sent if the contents 1263 of the filter identified by the subscription's "stream-filter- 1264 ref" leaf has changed. 1266 2.7.3. subscription-terminated 1268 This notification indicates that no further event records for this 1269 subscription should be expected from the publisher. A publisher may 1270 terminate the sending event records to a receiver for the following 1271 reasons: 1273 1. Configuration which removes a configured subscription, or a 1274 "kill-subscription" RPC which ends a dynamic subscription. These 1275 are identified via the reason "no-such-subscription". 1277 2. A referenced filter is no longer accessible. This is identified 1278 by "filter-unavailable". 1280 3. The event stream referenced by a subscription is no longer 1281 accessible by the receiver. This is identified by "stream- 1282 unavailable". 1284 4. A suspended subscription has exceeded some timeout. This is 1285 identified by "suspension-timeout". 1287 Each of the reasons above correspond one-to-one with a "reason" 1288 identityref specified within the YANG model. 1290 Below is a tree diagram for "subscription-terminated". All objects 1291 contained in this tree are described within the included YANG model 1292 within Section 4. 1294 +---n subscription-terminated 1295 +--ro identifier subscription-id 1296 +--ro reason identityref 1298 Figure 13: subscription-terminated notification tree diagram 1300 Note: this state change notification MUST be sent to a dynamic 1301 subscription's receiver when the subscription ends unexpectedly. The 1302 cases when this might happen are when a "kill-subscription" RPC is 1303 successful, or when some other event not including the reaching the 1304 subscription's "stop-time" results in a publisher choosing to end the 1305 subscription. 1307 2.7.4. subscription-suspended 1309 This notification indicates that a publisher has suspended the 1310 sending of event records to a receiver, and also indicates the 1311 possible loss of events. Suspension happens when capacity 1312 constraints stop a publisher from serving a valid subscription. The 1313 two conditions where is this possible are: 1315 1. "insufficient-resources" when a publisher is unable to produce 1316 the requested event stream of notification messages, and 1318 2. "unsupportable-volume" when the bandwidth needed to get generated 1319 notification messages to a receiver exceeds a threshold. 1321 These conditions are encoded within the "reason" object. No further 1322 notification will be sent until the subscription resumes or is 1323 terminated. 1325 Below is a tree diagram for "subscription-suspended". All objects 1326 contained in this tree are described within the included YANG model 1327 within Section 4. 1329 +---n subscription-suspended 1330 +--ro identifier subscription-id 1331 +--ro reason identityref 1333 Figure 14: subscription-suspended notification tree diagram 1335 2.7.5. subscription-resumed 1337 This notification indicates that a previously suspended subscription 1338 has been resumed under the unmodified terms previously in place. 1339 Subscribed event records generated after the issuance of this state 1340 change notification may now be sent. 1342 Below is the tree diagram for "subscription-resumed". All objects 1343 contained in this tree are described within the included YANG model 1344 within Section 4. 1346 +---n subscription-resumed 1347 +--ro identifier subscription-id 1349 Figure 15: subscription-resumed notification tree diagram 1351 2.7.6. subscription-completed 1353 This notification indicates that a subscription that includes a 1354 "stop-time" has successfully finished passing event records upon the 1355 reaching of that time. 1357 Below is a tree diagram for "subscription-completed". All objects 1358 contained in this tree are described within the included YANG model 1359 within Section 4. 1361 +---n subscription-completed 1362 +--ro identifier subscription-id 1364 Figure 16: subscription-completed notification tree diagram 1366 2.7.7. replay-completed 1368 This notification indicates that all of the event records prior to 1369 the current time have been passed to a receiver. It is sent before 1370 any notification message containing an event record with a timestamp 1371 later than (1) the "stop-time" or (2) the subscription's start time. 1373 If a subscription contains no "stop-time", or has a "stop-time" that 1374 has not been reached, then after the "replay-completed" notification 1375 has been sent, additional event records will be sent in sequence as 1376 they arise naturally on the publisher. 1378 Below is a tree diagram for "replay-completed". All objects 1379 contained in this tree are described within the included YANG model 1380 within Section 4. 1382 +---n replay-completed 1383 +--ro identifier subscription-id 1385 Figure 17: replay-completed notification tree diagram 1387 2.8. Subscription Monitoring 1389 In the operational datastore, the container "subscriptions" maintains 1390 the state of all dynamic subscriptions, as well as all configured 1391 subscriptions. Using datastore retrieval operations, or subscribing 1392 to the "subscriptions" container [I-D.ietf-netconf-yang-push] allows 1393 the state of subscriptions and their connectivity to receivers to be 1394 monitored. 1396 Each subscription in the operational datastore is represented as a 1397 list element. Included in this list are event counters for each 1398 receiver, the state of each receiver, as well as the subscription 1399 parameters currently in effect. The appearance of the leaf 1400 "configured-subscription-state" indicates that a particular 1401 subscription came into being via configuration. This leaf also 1402 indicates if current state of that subscription is valid, invalid, 1403 and concluded. 1405 To understand the flow of event records within a subscription, there 1406 are two counters available for each configured and dynamic receiver. 1407 The first counter is "count-sent" which shows the quantity of events 1408 actually identified for sending to a receiver. The second counter is 1409 "count-excluded" which shows event records not sent to receiver. 1410 "count-excluded" shows the combined results of both access control 1411 and per-subscription filtering. For configured subscriptions, 1412 counters are reset whenever the subscription is evaluated to valid 1413 (see (1) in Figure 8). 1415 Dynamic subscriptions are removed from the operational datastore once 1416 they expire (reaching stop-time) or when they are terminated. While 1417 many subscription objects are shown as configurable, dynamic 1418 subscriptions are only included within the operational datastore and 1419 as a result are not configurable. 1421 2.9. Advertisement 1423 Publishers supporting this document MUST indicate support of the YANG 1424 model "ietf-subscribed-notifications" within the YANG library of the 1425 publisher. In addition support for optional features "encode-xml", 1426 "encode-json", "configured" "supports-vrf", "qos", "xpath", 1427 "subtree", "interface-designation", "dscp", and "replay" MUST be 1428 indicated if supported. 1430 3. YANG Data Model Trees 1432 This section contains tree diagrams for nodes defined in Section 4. 1433 For tree diagrams of state change notifications, see Section 2.7. Or 1434 for the tree diagrams for the RPCs, see Section 2.4. 1436 3.1. Event Streams Container 1438 A publisher maintains a list of available event streams as 1439 operational data. This list contains both standardized and vendor- 1440 specific event streams. This enables subscribers to discover what 1441 streams a publisher supports. 1443 +--ro streams 1444 +--ro stream* [name] 1445 +--ro name string 1446 +--ro description string 1447 +--ro replay-support? empty {replay}? 1448 +--ro replay-log-creation-time yang:date-and-time {replay}? 1449 +--ro replay-log-aged-time? yang:date-and-time {replay}? 1451 Figure 18: Stream Container tree diagram 1453 Above is a tree diagram for the streams container. All objects 1454 contained in this tree are described within the included YANG model 1455 within Section 4. 1457 3.2. Filters Container 1459 The "filters" container maintains a list of all subscription filters 1460 that persist outside the life-cycle of a single subscription. This 1461 enables pre-defined filters which may be referenced by more than one 1462 subscription. 1464 +--rw filters 1465 +--rw stream-filter* [identifier] 1466 +--rw identifier filter-id 1467 +--rw (filter-spec)? 1468 +--:(stream-subtree-filter) 1469 | +--rw stream-subtree-filter? {subtree}? 1470 +--:(stream-xpath-filter) 1471 +--rw stream-xpath-filter? yang:xpath1.0 {xpath}? 1473 Figure 19: Filter Container tree diagram 1475 Above is a tree diagram for the filters container. All objects 1476 contained in this tree are described within the included YANG model 1477 within Section 4. 1479 3.3. Subscriptions Container 1481 The "subscriptions" container maintains a list of all subscriptions 1482 on a publisher, both configured and dynamic. It can be used to 1483 retrieve information about the subscriptions which a publisher is 1484 serving. 1486 +--rw subscriptions 1487 +--rw subscription* [identifier] 1488 +--rw identifier 1489 | subscription-id 1490 +--rw (target) 1491 | +--:(stream) 1492 | +--rw (stream-filter)? 1493 | | +--:(by-reference) 1494 | | | +--rw stream-filter-ref 1495 | | | stream-filter-ref 1496 | | +--:(within-subscription) 1497 | | +--rw (filter-spec)? 1498 | | +--:(stream-subtree-filter) 1499 | | | +--rw stream-subtree-filter? 1500 | | | {subtree}? 1501 | | +--:(stream-xpath-filter) 1502 | | +--rw stream-xpath-filter? yang:xpath1.0 1503 | | {xpath}? 1504 | +--rw stream stream-ref 1505 | +--ro replay-start-time? 1506 | | yang:date-and-time {replay}? 1507 | +--rw configured-replay? empty 1508 | {configured,replay}? 1509 +--rw stop-time? 1510 | yang:date-and-time 1511 +--rw dscp? inet:dscp 1512 | {dscp}? 1513 +--rw weighting? uint8 {qos}? 1514 +--rw dependency? 1515 | subscription-id {qos}? 1516 +--rw transport transport 1517 | {configured}? 1518 +--rw encoding? encoding 1519 +--rw purpose? string 1520 | {configured}? 1521 +--rw (notification-message-origin)? {configured}? 1522 | +--:(interface-originated) 1523 | | +--rw source-interface? 1524 | | if:interface-ref {interface-designation}? 1525 | +--:(address-originated) 1526 | +--rw source-vrf? 1527 | | -> /ni:network-instances/network-instance/name 1528 | | {supports-vrf}? 1529 | +--rw source-address? 1530 | inet:ip-address-no-zone 1531 +--ro configured-subscription-state? enumeration 1532 | {configured}? 1533 +--rw receivers 1534 +--rw receiver* [name] 1535 +--rw name string 1536 +--ro count-sent? yang:zero-based-counter64 1537 +--ro count-excluded? yang:zero-based-counter64 1538 +--ro state enumeration 1539 +---x reset {configured}? 1540 | +--ro output 1541 | +--ro time yang:date-and-time 1542 +--rw (transport) {configured}? 1544 Figure 20: Subscriptions tree diagram 1546 Above is a tree diagram for the subscriptions container. All objects 1547 contained in this tree are described within the included YANG model 1548 within Section 4. 1550 4. Data Model 1552 This module imports typedefs from [RFC6991], [RFC8343], and 1553 [RFC8040], and it references [I-D.draft-ietf-rtgwg-ni-model], 1554 [XPATH], [RFC6241], [RFC7540], [RFC7951] and [RFC7950]. 1556 [ note to the RFC Editor - please replace XXXX within this YANG model 1557 with the number of this document, and XXXY with the number of 1558 [I-D.draft-ietf-rtgwg-ni-model] ] 1560 [ note to the RFC Editor - please replace the two dates within the 1561 YANG module with the date of publication ] 1563 file "ietf-subscribed-notifications@2018-08-03.yang" 1564 module ietf-subscribed-notifications { 1565 yang-version 1.1; 1566 namespace 1567 "urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications"; 1569 prefix sn; 1571 import ietf-inet-types { 1572 prefix inet; 1573 reference 1574 "RFC 6991: Common YANG Data Types"; 1575 } 1576 import ietf-interfaces { 1577 prefix if; 1578 reference 1579 "RFC 8343: A YANG Data Model for Interface Management"; 1580 } 1581 import ietf-network-instance { 1582 prefix ni; 1583 reference 1584 "draft-ietf-rtgwg-ni-model-12: YANG Model for Network Instances"; 1585 } 1586 import ietf-restconf { 1587 prefix rc; 1588 reference 1589 "RFC 8040: RESTCONF Protocol"; 1590 } 1591 import ietf-yang-types { 1592 prefix yang; 1593 reference 1594 "RFC 6991: Common YANG Data Types"; 1595 } 1597 organization "IETF NETCONF (Network Configuration) Working Group"; 1598 contact 1599 "WG Web: 1600 WG List: 1602 Author: Alexander Clemm 1603 1605 Author: Eric Voit 1606 1608 Author: Alberto Gonzalez Prieto 1609 1611 Author: Einar Nilsen-Nygaard 1612 1614 Author: Ambika Prasad Tripathy 1615 "; 1617 description 1618 "Contains a YANG specification for subscribing to event records 1619 and receiving matching content within notification messages. 1621 Copyright (c) 2018 IETF Trust and the persons identified as authors 1622 of the code. All rights reserved. 1624 Redistribution and use in source and binary forms, with or without 1625 modification, is permitted pursuant to, and subject to the license 1626 terms contained in, the Simplified BSD License set forth in Section 1627 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents 1628 (https://trustee.ietf.org/license-info). 1630 This version of this YANG module is part of RFC XXXX; see the RFC 1631 itself for full legal notices."; 1633 revision 2018-08-03 { 1634 description 1635 "Initial version"; 1636 reference 1637 "RFC XXXX: Customized Subscriptions to a Publisher's Event Streams"; 1638 } 1640 /* 1641 * FEATURES 1642 */ 1644 feature configured { 1645 description 1646 "This feature indicates that configuration of subscription is 1647 supported."; 1648 } 1650 feature dscp { 1651 description 1652 "This feature indicates a publisher supports the placement of 1653 suggested prioritization levels for network transport within 1654 notification messages."; 1655 } 1657 feature encode-json { 1658 description 1659 "This feature indicates that JSON encoding of notification 1660 messages is supported."; 1661 } 1663 feature encode-xml { 1664 description 1665 "This feature indicates that XML encoding of notification 1666 messages is supported."; 1667 } 1669 feature interface-designation { 1670 description 1671 "This feature indicates a publisher supports sourcing all receiver 1672 interactions for a configured subscription from a single 1673 designated egress interface."; 1674 } 1676 feature qos { 1677 description 1678 "This feature indicates a publisher supports absolute dependencies 1679 of one subscription's traffic over another, as well as weighted 1680 bandwidth sharing between subscriptions. Both of these are 1681 Quality of Service (QoS) features which allow differentiated 1682 treatment of notification messages between a publisher and a 1683 specific receiver."; 1684 } 1686 feature replay { 1687 description 1688 "This feature indicates that historical event record replay is 1689 supported. With replay, it is possible for past event records to 1690 be streamed in chronological order."; 1691 } 1693 feature subtree { 1694 description 1695 "This feature indicates support for YANG subtree filtering."; 1696 reference "RFC 6241, Section 6."; 1697 } 1699 feature supports-vrf { 1700 description 1701 "This feature indicates a publisher supports VRF configuration 1702 for configured subscriptions. VRF support for dynamic 1703 subscriptions does not require this feature."; 1704 reference "RFC XXXY, Section 6."; 1705 } 1707 feature xpath { 1708 description 1709 "This feature indicates support for xpath filtering."; 1710 reference "http://www.w3.org/TR/1999/REC-xpath-19991116"; 1711 } 1713 /* 1714 * EXTENSIONS 1715 */ 1717 extension subscription-state-notification { 1718 description 1719 "This statement applies only to notifications. It indicates that 1720 the notification is a subscription state notification. Therefore 1721 it does not participate in a regular event stream and does not 1722 need to be specifically subscribed to in order to be received. 1723 This statement can only occur as a substatement to the YANG 1724 'notification' statement. This statement is not for use outside 1725 of this YANG module."; 1726 } 1728 /* 1729 * IDENTITIES 1730 */ 1732 /* Identities for RPC and Notification errors */ 1734 identity delete-subscription-error { 1735 description 1736 "Problem found while attempting to fulfill either a 1737 'delete-subscription' RPC request or a 'kill-subscription' 1738 RPC request."; 1739 } 1741 identity establish-subscription-error { 1742 description 1743 "Problem found while attempting to fulfill an 1744 'establish-subscription' RPC request."; 1745 } 1747 identity modify-subscription-error { 1748 description 1749 "Problem found while attempting to fulfill a 1750 'modify-subscription' RPC request."; 1751 } 1753 identity subscription-suspended-reason { 1754 description 1755 "Problem condition communicated to a receiver as part of a 1756 'subscription-terminated' notification."; 1757 } 1759 identity subscription-terminated-reason { 1760 description 1761 "Problem condition communicated to a receiver as part of a 1762 'subscription-terminated' notification."; 1763 } 1765 identity dscp-unavailable { 1766 base establish-subscription-error; 1767 if-feature "dscp"; 1768 description 1769 "The publisher is unable mark notification messages with a 1770 prioritization information in a way which will be respected during 1771 network transit."; 1772 } 1774 identity encoding-unsupported { 1775 base establish-subscription-error; 1776 description 1777 "Unable to encode notification messages in the desired format."; 1778 } 1780 identity filter-unavailable { 1781 base subscription-terminated-reason; 1782 description 1783 "Referenced filter does not exist. This means a receiver is 1784 referencing a filter which doesn't exist, or to which they do not 1785 have access permissions."; 1787 } 1789 identity filter-unsupported { 1790 base establish-subscription-error; 1791 base modify-subscription-error; 1792 description 1793 "Cannot parse syntax within the filter. This failure can be from 1794 a syntax error, or a syntax too complex to be processed by the 1795 publisher."; 1796 } 1798 identity history-unavailable { 1799 base establish-subscription-error; 1800 if-feature "replay"; 1801 description 1802 "Replay request too far into the past. This means the publisher 1803 does store historic information for the requested stream, but 1804 not back to the requested timestamp."; 1805 } 1807 identity insufficient-resources { 1808 base establish-subscription-error; 1809 base modify-subscription-error; 1810 base subscription-suspended-reason; 1811 description 1812 "The publisher has insufficient resources to support the 1813 requested subscription. An example might be that allocated CPU 1814 is too limited to generate the desired set of notification 1815 messages."; 1816 } 1818 identity no-such-subscription { 1819 base modify-subscription-error; 1820 base delete-subscription-error; 1821 base subscription-terminated-reason; 1822 description 1823 "Referenced subscription doesn't exist. This may be as a result of 1824 a non-existent subscription ID, an ID which belongs to another 1825 subscriber, or an ID for configured subscription."; 1826 } 1828 identity replay-unsupported { 1829 base establish-subscription-error; 1830 if-feature "replay"; 1831 description 1832 "Replay cannot be performed for this subscription. This means the 1833 publisher will not provide the requested historic information from 1834 the event stream via replay to this receiver."; 1836 } 1838 identity stream-unavailable { 1839 base subscription-terminated-reason; 1840 description 1841 "Not a subscribable stream. This means the referenced event stream 1842 is not available for subscription by the receiver."; 1843 } 1845 identity suspension-timeout { 1846 base subscription-terminated-reason; 1847 description 1848 "Termination of previously suspended subscription. The publisher 1849 has eliminated the subscription as it exceeded a time limit for 1850 suspension."; 1851 } 1853 identity unsupportable-volume { 1854 base subscription-suspended-reason; 1855 description 1856 "The publisher does not have the network bandwidth needed to get 1857 the volume of generated information intended for a receiver."; 1858 } 1860 /* Identities for encodings */ 1862 identity configurable-encoding { 1863 description 1864 "If a transport identity derives from this identity, it means 1865 that it supports configurable encodings."; 1866 } 1868 identity encoding { 1869 description 1870 "Base identity to represent data encodings"; 1871 } 1873 identity encode-xml { 1874 base encoding; 1875 if-feature "encode-xml"; 1876 description 1877 "Encode data using XML as described in RFC 7950"; 1878 reference 1879 "RFC 7950 - The YANG 1.1 Data Modeling Language"; 1880 } 1882 identity encode-json { 1883 base encoding; 1884 if-feature "encode-json"; 1885 description 1886 "Encode data using JSON as described in RFC 7951"; 1887 reference 1888 "RFC 7951 - JSON Encoding of Data Modeled with YANG"; 1889 } 1891 /* Identities for transports */ 1892 identity transport { 1893 description 1894 "An identity that represents the underlying mechanism for 1895 passing notification messages."; 1896 } 1898 identity inline-address { 1899 description 1900 "A transport identity can derive from this identity in order to 1901 allow inline definition of the host address in the 1902 'receiver' list"; 1903 } 1905 /* 1906 * TYPEDEFs 1907 */ 1909 typedef encoding { 1910 type identityref { 1911 base encoding; 1912 } 1913 description 1914 "Specifies a data encoding, e.g. for a data subscription."; 1915 } 1917 typedef filter-id { 1918 type string; 1919 description 1920 "A type to identify filters which can be associated with a 1921 subscription."; 1922 } 1924 typedef stream-filter-ref { 1925 type leafref { 1926 path "/sn:filters/sn:stream-filter/sn:identifier"; 1927 } 1928 description 1929 "This type is used to reference an event stream filter."; 1930 } 1931 typedef stream-ref { 1932 type leafref { 1933 path "/sn:streams/sn:stream/sn:name"; 1934 } 1935 description 1936 "This type is used to reference a system-provided stream."; 1937 } 1939 typedef subscription-id { 1940 type uint32; 1941 description 1942 "A type for subscription identifiers."; 1943 } 1945 typedef transport { 1946 type identityref { 1947 base transport; 1948 } 1949 description 1950 "Specifies transport used to send notification messages to a 1951 receiver."; 1952 } 1954 /* 1955 * GROUPINGS 1956 */ 1958 grouping stream-filter-elements { 1959 description 1960 "This grouping defines the base for filters applied to event 1961 streams."; 1962 choice filter-spec { 1963 description 1964 "The content filter specification for this request."; 1965 anydata stream-subtree-filter { 1966 if-feature "subtree"; 1967 description 1968 "Event stream evaluation criteria encoded in the syntax of a 1969 subtree filter as defined in RFC 6241, Section 6. 1971 The subtree filter is applied to the representation of 1972 individual, delineated event records as contained within the 1973 event stream. For example, if the notification message 1974 contains an instance of a notification defined in YANG, then 1975 the top-level element is the name of the YANG notification. 1977 If the subtree filter returns a non-empty node set, the filter 1978 matches the event record, and the event record is included in 1979 the notification message sent to the receivers."; 1980 reference "RFC 6241, Section 6."; 1981 } 1982 leaf stream-xpath-filter { 1983 if-feature "xpath"; 1984 type yang:xpath1.0; 1985 description 1986 "Event stream evaluation criteria encoded in the syntax of 1987 an XPath 1.0 expression. 1989 The XPath expression is evaluated on the representation of 1990 individual, delineated event records as contained within 1991 the event stream. For example, if the notification message 1992 contains an instance of a notification defined in YANG, 1993 then the top-level element is the name of the YANG 1994 notification, and the root node has this top-level element 1995 as the only child. 1997 The result of the XPath expression is converted to a 1998 boolean value using the standard XPath 1.0 rules. If the 1999 boolean value is 'true', the filter matches the event record, 2000 and the event record is included in the notification message 2001 sent to the receivers. 2003 The expression is evaluated in the following XPath context: 2005 o The set of namespace declarations are those in scope on 2006 the 'stream-xpath-filter' leaf element. 2008 o The set of variable bindings is empty. 2010 o The function library is the core function library, and 2011 the XPath functions defined in section 10 in RFC 7950. 2013 o The context node is the root node."; 2014 reference 2015 "http://www.w3.org/TR/1999/REC-xpath-19991116 2016 RFC 7950, Section 10."; 2018 } 2019 } 2020 } 2022 grouping update-qos { 2023 description 2024 "This grouping describes Quality of Service information 2025 concerning a subscription. This information is passed to lower 2026 layers for transport prioritization and treatment"; 2028 leaf dscp { 2029 if-feature "dscp"; 2030 type inet:dscp; 2031 default "0"; 2032 description 2033 "The desired network transport priority level. This is the 2034 priority set on notification messages encapsulating the results 2035 of the subscription. This transport priority is shared for all 2036 receivers of a given subscription."; 2037 } 2038 leaf weighting { 2039 if-feature "qos"; 2040 type uint8 { 2041 range "0 .. 255"; 2042 } 2043 description 2044 "Relative weighting for a subscription. Allows an underlying 2045 transport layer perform informed load balance allocations 2046 between various subscriptions"; 2047 reference 2048 "RFC-7540, section 5.3.2"; 2049 } 2050 leaf dependency { 2051 if-feature "qos"; 2052 type subscription-id; 2053 description 2054 "Provides the 'subscription-id' of a parent subscription which 2055 has absolute precedence should that parent have push updates 2056 ready to egress the publisher. In other words, there should be 2057 no streaming of objects from the current subscription if 2058 the parent has something ready to push. 2060 If a dependency is asserted via configuration or via RPC, but 2061 the referenced 'subscription-id' does not exist, the dependency 2062 is silently discarded. If a referenced subscription is deleted 2063 this dependency is removed."; 2064 reference 2065 "RFC-7540, section 5.3.1"; 2066 } 2067 } 2069 grouping subscription-policy-modifiable { 2070 description 2071 "This grouping describes all objects which may be changed 2072 in a subscription."; 2073 choice target { 2074 mandatory true; 2075 description 2076 "Identifies the source of information against which a 2077 subscription is being applied, as well as specifics on the 2078 subset of information desired from that source."; 2079 case stream { 2080 choice stream-filter { 2081 description 2082 "An event stream filter can be applied to a subscription. 2083 That filter will come either referenced from a global list, 2084 or be provided within the subscription itself."; 2085 case by-reference { 2086 description 2087 "Apply a filter that has been configured separately."; 2088 leaf stream-filter-ref { 2089 type stream-filter-ref; 2090 mandatory true; 2091 description 2092 "References an existing stream filter which is to 2093 be applied to an event stream for the subscription."; 2094 } 2095 } 2096 case within-subscription { 2097 description 2098 "Local definition allows a filter to have the same 2099 lifecycle as the subscription."; 2100 uses stream-filter-elements; 2101 } 2102 } 2103 } 2104 } 2105 leaf stop-time { 2106 type yang:date-and-time; 2107 description 2108 "Identifies a time after which notification messages for a 2109 subscription should not be sent. If 'stop-time' is not present, 2110 the notification messages will continue until the subscription 2111 is terminated. If 'replay-start-time' exists, 'stop-time' must 2112 be for a subsequent time. If 'replay-start-time' doesn't exist, 2113 'stop-time' when established must be for a future time."; 2114 } 2115 } 2117 grouping subscription-policy-dynamic { 2118 description 2119 "This grouping describes the only information concerning a 2120 subscription which can be passed over the RPCs defined in this 2121 model."; 2122 uses subscription-policy-modifiable { 2123 augment target/stream { 2124 description 2125 "Adds additional objects which can be modified by RPC."; 2126 leaf stream { 2127 type stream-ref { 2128 require-instance false; 2129 } 2130 mandatory true; 2131 description 2132 "Indicates the event stream to be considered for 2133 this subscription."; 2134 } 2135 leaf replay-start-time { 2136 if-feature "replay"; 2137 type yang:date-and-time; 2138 config false; 2139 description 2140 "Used to trigger the replay feature for a dynamic 2141 subscription, with event records being selected needing to 2142 be at or after the start at the time specified. If 2143 'replay-start-time' is not present, this is not a replay 2144 subscription and event record push should start immediately. 2145 It is never valid to specify start times that are later than 2146 or equal to the current time."; 2147 } 2148 } 2149 } 2150 uses update-qos; 2151 } 2153 grouping subscription-policy { 2154 description 2155 "This grouping describes the full set of policy information 2156 concerning both dynamic and configured subscriptions, with the 2157 exclusion of both receivers and networking information specific to 2158 the publisher such as what interface should be used to transmit 2159 notification messages."; 2160 uses subscription-policy-dynamic; 2161 leaf transport { 2162 if-feature "configured"; 2163 type transport; 2164 mandatory true; 2165 description 2166 "This leaf specifies the transport used to deliver 2167 messages destined to all receivers of a subscription."; 2168 } 2169 leaf encoding { 2170 when 'not(../transport) or derived-from(../transport, 2171 "sn:configurable-encoding")'; 2172 type encoding; 2173 description 2174 "The type of encoding for notification messages. For a 2175 dynamic subscription, if not included as part of an establish- 2176 subscription RPC, the encoding will be populated with the 2177 encoding used by that RPC. For a configured subscription, if 2178 not explicitly configured the encoding with be the default 2179 encoding for an underlying transport."; 2180 } 2181 leaf purpose { 2182 if-feature "configured"; 2183 type string; 2184 description 2185 "Open text allowing a configuring entity to embed the 2186 originator or other specifics of this subscription."; 2187 } 2188 } 2190 /* 2191 * RPCs 2192 */ 2194 rpc establish-subscription { 2195 description 2196 "This RPC allows a subscriber to create (and possibly negotiate) 2197 a subscription on its own behalf. If successful, the 2198 subscription remains in effect for the duration of the 2199 subscriber's association with the publisher, or until the 2200 subscription is terminated. In case an error occurs, or the 2201 publisher cannot meet the terms of a subscription, an RPC error 2202 is returned, the subscription is not created. In that case, the 2203 RPC reply's 'error-info' MAY include suggested parameter settings 2204 that would have a higher likelihood of succeeding in a subsequent 2205 'establish-subscription' request."; 2206 input { 2207 uses subscription-policy-dynamic; 2208 leaf encoding { 2209 type encoding; 2210 description 2211 "The type of encoding for the subscribed data. If not 2212 included as part of the RPC, the encoding MUST be set by the 2213 publisher to be the encoding used by this RPC."; 2214 } 2215 } 2216 output { 2217 leaf identifier { 2218 type subscription-id; 2219 mandatory true; 2220 description 2221 "Identifier used for this subscription."; 2222 } 2223 leaf replay-start-time-revision { 2224 if-feature "replay"; 2225 type yang:date-and-time; 2226 description 2227 "If a replay has been requested, this represents the 2228 earliest time covered by the event buffer for the requested 2229 stream. The value of this object is the 2230 'replay-log-aged-time' if it exists. Otherwise it is the 2231 'replay-log-creation-time'. All buffered event records 2232 after this time will be replayed to a receiver. This 2233 object will only be sent if the starting time has been 2234 revised to be later than the time requested by the 2235 subscriber."; 2236 } 2237 } 2238 } 2240 rc:yang-data establish-subscription-stream-error-info { 2241 container establish-subscription-stream-error-info { 2242 description 2243 "If any 'establish-subscription' RPC parameters are 2244 unsupportable against the event stream, a subscription is not 2245 created and the RPC error response MUST indicate the reason 2246 why the subscription failed to be created. This yang-data MAY be 2247 inserted as structured data within a subscription's RPC error 2248 response to indicate the failure reason. This yang-data MUST be 2249 inserted if hints are to be provided back to the subscriber."; 2250 leaf reason { 2251 type identityref { 2252 base establish-subscription-error; 2253 } 2254 description 2255 "Indicates the reason why the subscription has failed to 2256 be created to a targeted stream."; 2257 } 2258 leaf filter-failure-hint { 2259 type string; 2260 description 2261 "Information describing where and/or why a provided filter 2262 was unsupportable for a subscription."; 2263 } 2264 } 2265 } 2267 rpc modify-subscription { 2268 description 2269 "This RPC allows a subscriber to modify a dynamic subscription's 2270 parameters. If successful, the changed subscription 2271 parameters remain in effect for the duration of the subscription, 2272 until the subscription is again modified, or until the 2273 subscription is terminated. In case of an error or an inability 2274 to meet the modified parameters, the subscription is not modified 2275 and the original subscription parameters remain in effect. 2276 In that case, the RPC error MAY include 'error-info' suggested 2277 parameter hints that would have a high likelihood of succeeding 2278 in a subsequent 'modify-subscription' request. A successful 2279 'modify-subscription' will return a suspended subscription to an 2280 'active' state."; 2281 input { 2282 leaf identifier { 2283 type subscription-id; 2284 mandatory true; 2285 description 2286 "Identifier to use for this subscription."; 2287 } 2288 uses subscription-policy-modifiable; 2289 } 2290 } 2292 rc:yang-data modify-subscription-stream-error-info { 2293 container modify-subscription-stream-error-info { 2294 description 2295 "This yang-data MAY be provided as part of a subscription's RPC 2296 error response when there is a failure of a 2297 'modify-subscription' RPC which has been made against a 2298 stream. This yang-data MUST be used if hints are to be 2299 provided back to the subscriber."; 2300 leaf reason { 2301 type identityref { 2302 base modify-subscription-error; 2303 } 2304 description 2305 "Information in a 'modify-subscription' RPC error response 2306 which indicates the reason why the subscription to an event 2307 stream has failed to be modified."; 2308 } 2309 leaf filter-failure-hint { 2310 type string; 2311 description 2312 "Information describing where and/or why a provided filter 2313 was unsupportable for a subscription."; 2314 } 2315 } 2317 } 2319 rpc delete-subscription { 2320 description 2321 "This RPC allows a subscriber to delete a subscription that 2322 was previously created from by that same subscriber using the 2323 'establish-subscription' RPC. 2325 If an error occurs, the server replies with an 'rpc-error' where 2326 the 'error-info' field MAY contain an 2327 'delete-subscription-error-info' structure."; 2328 input { 2329 leaf identifier { 2330 type subscription-id; 2331 mandatory true; 2332 description 2333 "Identifier of the subscription that is to be deleted. 2334 Only subscriptions that were created using 2335 'establish-subscription' from the same origin as this RPC 2336 can be deleted via this RPC."; 2337 } 2338 } 2339 } 2341 rpc kill-subscription { 2342 description 2343 "This RPC allows an operator to delete a dynamic subscription 2344 without restrictions on the originating subscriber or underlying 2345 transport session. 2347 If an error occurs, the server replies with an 'rpc-error' where 2348 the 'error-info' field MAY contain an 2349 'delete-subscription-error-info' structure."; 2350 input { 2351 leaf identifier { 2352 type subscription-id; 2353 mandatory true; 2354 description 2355 "Identifier of the subscription that is to be deleted. Only 2356 subscriptions that were created using 2357 'establish-subscription' can be deleted via this RPC."; 2358 } 2359 } 2360 } 2362 rc:yang-data delete-subscription-error-info { 2363 container delete-subscription-error-info { 2364 description 2365 "If a 'delete-subscription' RPC or a 'kill-subscription' RPC 2366 fails, the subscription is not deleted and the RPC error 2367 response MUST indicate the reason for this failure. This 2368 yang-data MAY be inserted as structured data within a 2369 subscription's RPC error response to indicate the failure 2370 reason."; 2371 leaf reason { 2372 type identityref { 2373 base delete-subscription-error; 2374 } 2375 mandatory true; 2376 description 2377 "Indicates the reason why the subscription has failed to be 2378 deleted."; 2379 } 2380 } 2381 } 2383 /* 2384 * NOTIFICATIONS 2385 */ 2387 notification replay-completed { 2388 sn:subscription-state-notification; 2389 if-feature "replay"; 2390 description 2391 "This notification is sent to indicate that all of the replay 2392 notifications have been sent. It must not be sent for any other 2393 reason."; 2394 leaf identifier { 2395 type subscription-id; 2396 mandatory true; 2397 description 2398 "This references the affected subscription."; 2399 } 2400 } 2402 notification subscription-completed { 2403 sn:subscription-state-notification; 2404 if-feature "configured"; 2405 description 2406 "This notification is sent to indicate that a subscription has 2407 finished passing event records, as the 'stop-time' has been 2408 reached."; 2409 leaf identifier { 2410 type subscription-id; 2411 mandatory true; 2412 description 2413 "This references the gracefully completed subscription."; 2414 } 2415 } 2417 notification subscription-modified { 2418 sn:subscription-state-notification; 2419 description 2420 "This notification indicates that a subscription has been 2421 modified. Notification messages sent from this point on will 2422 conform to the modified terms of the subscription. For 2423 completeness, this state change notification includes both 2424 modified and non-modified aspects of a subscription."; 2425 leaf identifier { 2426 type subscription-id; 2427 mandatory true; 2428 description 2429 "This references the affected subscription."; 2430 } 2431 uses subscription-policy { 2432 refine "target/stream/stream-filter/within-subscription" { 2433 description 2434 "Filter applied to the subscription. If the 2435 'stream-filter-ref' is populated, the filter within the 2436 subscription came from the 'filters' container. Otherwise it 2437 is populated in-line as part of the subscription."; 2438 } 2439 } 2440 } 2442 notification subscription-resumed { 2443 sn:subscription-state-notification; 2444 description 2445 "This notification indicates that a subscription that had 2446 previously been suspended has resumed. Notifications will once 2447 again be sent. In addition, a 'subscription-resumed' indicates 2448 that no modification of parameters has occurred since the last 2449 time event records have been sent."; 2450 leaf identifier { 2451 type subscription-id; 2452 mandatory true; 2453 description 2454 "This references the affected subscription."; 2455 } 2456 } 2458 notification subscription-started { 2459 sn:subscription-state-notification; 2460 if-feature "configured"; 2461 description 2462 "This notification indicates that a subscription has started and 2463 notifications are beginning to be sent. This notification shall 2464 only be sent to receivers of a subscription; it does not 2465 constitute a general-purpose notification."; 2466 leaf identifier { 2467 type subscription-id; 2468 mandatory true; 2469 description 2470 "This references the affected subscription."; 2471 } 2472 uses subscription-policy { 2473 refine "target/stream/replay-start-time" { 2474 description 2475 "Indicates the time that a replay using for the streaming of 2476 buffered event records. This will be populated with the most 2477 recent of the following: 'replay-log-creation-time', 2478 'replay-log-aged-time', or the most recent publisher boot 2479 time."; 2480 } 2481 refine "target/stream/stream-filter/within-subscription" { 2482 description 2483 "Filter applied to the subscription. If the 2484 'stream-filter-ref' is populated, the filter within the 2485 subscription came from the 'filters' container. Otherwise it 2486 is populated in-line as part of the subscription."; 2487 } 2488 augment "target/stream" { 2489 description 2490 "This augmentation adds additional parameters specific to a 2491 subscription-started notification."; 2492 leaf replay-previous-event-time { 2493 when "../replay-start-time"; 2494 if-feature "replay"; 2495 type yang:date-and-time; 2496 description 2497 "If there is at least one event in the replay buffer prior 2498 to 'replay-start-time', this gives the time of the event 2499 generated immediately prior to the 'replay-start-time'. 2501 If a receiver previously received event records for this 2502 configured subscription, it can compare this time to the 2503 last event record previously received. If the two are not 2504 the same (perhaps due to a reboot), then a dynamic replay 2505 can be initiated to acquire any missing event records."; 2506 } 2507 } 2508 } 2510 } 2512 notification subscription-suspended { 2513 sn:subscription-state-notification; 2514 description 2515 "This notification indicates that a suspension of the 2516 subscription by the publisher has occurred. No further 2517 notifications will be sent until the subscription resumes. 2518 This notification shall only be sent to receivers of a 2519 subscription; it does not constitute a general-purpose 2520 notification."; 2521 leaf identifier { 2522 type subscription-id; 2523 mandatory true; 2524 description 2525 "This references the affected subscription."; 2526 } 2527 leaf reason { 2528 type identityref { 2529 base subscription-suspended-reason; 2530 } 2531 mandatory true; 2532 description 2533 "Identifies the condition which resulted in the suspension."; 2534 } 2535 } 2537 notification subscription-terminated { 2538 sn:subscription-state-notification; 2539 description 2540 "This notification indicates that a subscription has been 2541 terminated."; 2542 leaf identifier { 2543 type subscription-id; 2544 mandatory true; 2545 description 2546 "This references the affected subscription."; 2547 } 2548 leaf reason { 2549 type identityref { 2550 base subscription-terminated-reason; 2551 } 2552 mandatory true; 2553 description 2554 "Identifies the condition which resulted in the termination ."; 2555 } 2556 } 2557 /* 2558 * DATA NODES 2559 */ 2561 container streams { 2562 config false; 2563 description 2564 "This container contains information on the built-in streams 2565 provided by the publisher."; 2566 list stream { 2567 key "name"; 2568 description 2569 "Identifies the built-in event streams that are supported by the 2570 publisher."; 2571 leaf name { 2572 type string; 2573 description 2574 "A handle for a system-provided event stream made up of a 2575 sequential set of event records, each of which is 2576 characterized by its own domain and semantics."; 2577 } 2578 leaf description { 2579 type string; 2580 mandatory true; 2581 description 2582 "A description of the event stream, including such information 2583 as the type of event records that are available within this 2584 event stream."; 2585 } 2586 leaf replay-support { 2587 if-feature "replay"; 2588 type empty; 2589 description 2590 "Indicates that event record replay is available on this 2591 stream."; 2592 } 2593 leaf replay-log-creation-time { 2594 when "../replay-support"; 2595 if-feature "replay"; 2596 type yang:date-and-time; 2597 mandatory true; 2598 description 2599 "The timestamp of the creation of the log used to support the 2600 replay function on this stream. This time might be earlier 2601 than the earliest available information contained in the log. 2602 This object is updated if the log resets for some reason."; 2603 } 2604 leaf replay-log-aged-time { 2605 if-feature "replay"; 2606 type yang:date-and-time; 2607 description 2608 "The timestamp associated with last event record which has 2609 been aged out of the log. This timestamp identifies how far 2610 back into history this replay log extends, if it doesn't 2611 extend back to the 'replay-log-creation-time'. This object 2612 MUST be present if replay is supported and any event records 2613 have been aged out of the log."; 2614 } 2615 } 2616 } 2618 container filters { 2619 description 2620 "This container contains a list of configurable filters 2621 that can be applied to subscriptions. This facilitates 2622 the reuse of complex filters once defined."; 2623 list stream-filter { 2624 key "identifier"; 2625 description 2626 "A list of pre-configured filters that can be applied to 2627 subscriptions."; 2628 leaf identifier { 2629 type filter-id; 2630 description 2631 "An identifier to differentiate between filters."; 2632 } 2633 uses stream-filter-elements; 2634 } 2635 } 2637 container subscriptions { 2638 description 2639 "Contains the list of currently active subscriptions, i.e. 2640 subscriptions that are currently in effect, used for subscription 2641 management and monitoring purposes. This includes subscriptions 2642 that have been setup via RPC primitives as well as subscriptions 2643 that have been established via configuration."; 2644 list subscription { 2645 key "identifier"; 2646 description 2647 "The identity and specific parameters of a subscription. 2648 Subscriptions within this list can be created using a control 2649 channel or RPC, or be established through configuration. 2651 If configuration operations or the 'kill-subscription' RPC are 2652 used to delete a subscription, a 'subscription-terminated' 2653 message is sent to any active or suspended receivers."; 2654 leaf identifier { 2655 type subscription-id; 2656 description 2657 "Identifier of a subscription; unique within a publisher"; 2658 } 2659 uses subscription-policy { 2660 refine "target/stream/stream" { 2661 description 2662 "Indicates the event stream to be considered for this 2663 subscription. If an event stream has been removed, 2664 and no longer can be referenced by an active subscription, 2665 send a 'subscription-terminated' notification with 2666 'stream-unavailable' as the reason. If a configured 2667 subscription refers to a non-existent stream, move that 2668 subscription to the 'invalid' state."; 2669 } 2670 augment "target/stream" { 2671 description 2672 "Enables objects to added to a configured stream 2673 subscription"; 2674 leaf configured-replay { 2675 if-feature "configured"; 2676 if-feature "replay"; 2677 type empty; 2678 description 2679 "The presence of this leaf indicates that replay for the 2680 configured subscription should start at the earliest time 2681 in the event log, or at the publisher boot time, which 2682 ever is later."; 2683 } 2684 } 2685 } 2686 choice notification-message-origin { 2687 if-feature "configured"; 2688 description 2689 "Identifies the egress interface on the publisher from which 2690 notification messages are to be sent."; 2691 case interface-originated { 2692 description 2693 "When notification messages to egress a specific, designated 2694 interface on the publisher."; 2695 leaf source-interface { 2696 if-feature "interface-designation"; 2697 type if:interface-ref; 2698 description 2699 "References the interface for notification messages."; 2700 } 2702 } 2703 case address-originated { 2704 description 2705 "When notification messages are to depart from a publisher 2706 using specific originating address and/or routing context 2707 information."; 2708 leaf source-vrf { 2709 if-feature "supports-vrf"; 2710 type leafref { 2711 path "/ni:network-instances/ni:network-instance/ni:name"; 2712 } 2713 description 2714 "VRF from which notification messages should egress a 2715 publisher."; 2716 } 2717 leaf source-address { 2718 type inet:ip-address-no-zone; 2719 description 2720 "The source address for the notification messages. If a 2721 source VRF exists, but this object doesn't, a publisher's 2722 default address for that VRF must be used."; 2723 } 2724 } 2725 } 2726 leaf configured-subscription-state { 2727 if-feature "configured"; 2728 type enumeration { 2729 enum valid { 2730 value 1; 2731 description 2732 "Connection is active and healthy."; 2733 } 2734 enum invalid { 2735 value 2; 2736 description 2737 "The subscription as a whole is unsupportable with its 2738 current parameters."; 2739 } 2740 enum concluded { 2741 value 3; 2742 description 2743 "A subscription is inactive as it has hit a stop time, 2744 but not yet been removed from configuration."; 2745 } 2746 } 2747 config false; 2748 description 2749 "The presence of this leaf indicates that the subscription 2750 originated from configuration, not through a control channel 2751 or RPC. The value indicates the system established state 2752 of the subscription."; 2753 } 2754 container receivers { 2755 description 2756 "Set of receivers in a subscription."; 2757 list receiver { 2758 key "name"; 2759 min-elements 1; 2760 description 2761 "A host intended as a recipient for the notification 2762 messages of a subscription. For configured subscriptions, 2763 transport specific network parameters (or a leafref to 2764 those parameters) may augmentated to a specific receiver 2765 within this list."; 2766 leaf name { 2767 type string; 2768 description 2769 "Identifies a unique receiver for a subscription."; 2770 } 2771 leaf count-sent { 2772 type yang:zero-based-counter64; 2773 config false; 2774 description 2775 "The number of event records sent to the receiver. The 2776 count is initialized when a dynamic subscription is 2777 established, or when a configured subscription 2778 transitions to the valid state."; 2779 } 2780 leaf count-excluded { 2781 type yang:zero-based-counter64; 2782 config false; 2783 description 2784 "The number of event records explicitly removed either 2785 via an event stream filter or an access control filter so 2786 that they are not passed to a receiver. This count is 2787 set to zero each time 'count-sent' is initialized."; 2788 } 2789 leaf state { 2790 type enumeration { 2791 enum active { 2792 value 1; 2793 description 2794 "Receiver is currently being sent any applicable 2795 notification messages for the subscription."; 2796 } 2797 enum suspended { 2798 value 2; 2799 description 2800 "Receiver state is 'suspended', so the publisher 2801 is currently unable to provide notification messages 2802 for the subscription."; 2803 } 2804 enum connecting { 2805 value 3; 2806 if-feature "configured"; 2807 description 2808 "A subscription has been configured, but a 2809 'subscription-started' state change notification needs 2810 to be successfully received before notification 2811 messages are sent. 2813 If the 'reset' action is invoked for a receiver of an 2814 active configured subscription, the state must be 2815 moved to 'connecting'."; 2816 } 2817 enum timeout { 2818 value 4; 2819 if-feature "configured"; 2820 description 2821 "A subscription has failed in sending a subscription 2822 started state change to the receiver. 2823 Additional attempts at connection attempts are not 2824 currently being made."; 2825 } 2826 } 2827 config false; 2828 mandatory true; 2829 description 2830 "Specifies the state of a subscription from the 2831 perspective of a particular receiver. With this info it 2832 is possible to determine whether a subscriber is currently 2833 generating notification messages intended for that 2834 receiver."; 2835 } 2836 action reset { 2837 if-feature "configured"; 2838 description 2839 "Allows the reset of this configured subscription receiver 2840 to the 'connecting' state. This enables the 2841 connection process to be re-initiated."; 2842 output { 2843 leaf time { 2844 type yang:date-and-time; 2845 mandatory true; 2846 description 2847 "Time a publisher returned the receiver to a 2848 'connecting' state."; 2849 } 2850 } 2851 } 2852 choice transport { 2853 if-feature "configured"; 2854 mandatory true; 2855 description 2856 "Defines the transport-specific configuration data 2857 for the value of the leaf 'transport' specified under 2858 '/subscriptions/subsription'. Individual transport 2859 specifications MUST augment this choice with YANG case 2860 statements. Each transport specific case augmentation 2861 enables the inclusion to transport parameters such as the 2862 IP address, port, and security credentials. It is these 2863 parameters which are used as necessary for making a 2864 secure transport connection to the receiver."; 2865 } 2866 } 2867 } 2868 } 2869 } 2870 } 2871 2873 5. Considerations 2875 5.1. IANA Considerations 2877 This document registers the following namespace URI in the "IETF XML 2878 Registry" [RFC3688]: 2880 URI: urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications 2881 Registrant Contact: The IESG. 2882 XML: N/A; the requested URI is an XML namespace. 2884 This document registers the following YANG module in the "YANG Module 2885 Names" registry [RFC6020]: 2887 Name: ietf-subscribed-notifications 2888 Namespace: urn:ietf:params:xml:ns:yang:ietf-subscribed-notifications 2889 Prefix: sn 2890 Reference: draft-ietf-netconf-ietf-subscribed-notifications-11.txt 2891 (RFC form) 2893 5.2. Implementation Considerations 2895 To support deployments including both configured and dynamic 2896 subscriptions, it is recommended to split subscription identifiers 2897 into static and dynamic halves. That way it eliminates the 2898 possibility of collisions if the configured subscriptions attempt to 2899 set a subscription-id which might have already been dynamically 2900 allocated. A best practice is to use lower half the "identifier" 2901 object's integer space when that "identifier" is assigned by an 2902 external entity (such as with a configured subscription). This 2903 leaves the upper half of subscription identifiers available to be 2904 dynamically assigned by the publisher. 2906 If a subscription is unable to marshal a series of filtered event 2907 records into transmittable notification messages, the receiver should 2908 be suspended with the reason "unsupportable-volume". 2910 For configured subscriptions, operations are against the set of 2911 receivers using the subscription identifier as a handle for that set. 2912 But for streaming updates, state change notifications are local to a 2913 receiver. In this specification it is the case that receivers get no 2914 information from the publisher about the existence of other 2915 receivers. But if a network operator wants to let the receivers 2916 correlate results, it is useful to use the subscription identifier 2917 across the receivers to allow that correlation. 2919 For configured replay subscriptions, the receiver is protected from 2920 duplicated events being pushed after a publisher is rebooted. 2921 However it is possible that a receiver might want to acquire event 2922 records which failed to be delivered just prior to the reboot. 2923 Delivering these event records be accomplished by leveraging the 2924 "eventTime" from the last event record received prior to the receipt 2925 of a "subscription-started" state change notification. With this 2926 "eventTime" and the "replay-start-time" from the "subscription- 2927 started" notification, an independent dynamic subscription can be 2928 established which retrieves any event records which may have been 2929 generated but not sent to the receiver. 2931 5.3. Transport Requirements 2933 This section provides requirements for any subscribed notification 2934 transport supporting the solution presented in this document. 2936 For both configured and dynamic subscriptions the publisher MUST 2937 authenticate a receiver via some transport level mechanism before 2938 sending any event records for which they are authorized to see. In 2939 addition, the receiver MUST authenticate the publisher at the 2940 transport level. The result is mutual authentication between the 2941 two. 2943 A secure transport is highly recommended and the publisher MUST 2944 ensure that the receiver has sufficient authorization to perform the 2945 function they are requesting against the specific subset of content 2946 involved. 2948 A specific transport specification built upon this document may or 2949 may not choose to require the use of the same logical channel for the 2950 RPCs and the event records. However the event records and the 2951 subscription state notifications MUST be sent on the same transport 2952 session to ensure the properly ordered delivery. 2954 Additional transport requirements will be dictated by the choice of 2955 transport used with a subscription. For an example of such 2956 requirements with NETCONF transport, see 2957 [I-D.draft-ietf-netconf-netconf-event-notifications]. 2959 5.4. Security Considerations 2961 The YANG module specified in this document defines a schema for data 2962 that is designed to be accessed via network management transports 2963 such as NETCONF [RFC6241] or RESTCONF [RFC8040]. The lowest NETCONF 2964 layer is the secure transport layer, and the mandatory-to-implement 2965 secure transport is Secure Shell (SSH) [RFC6242]. The lowest 2966 RESTCONF layer is HTTPS, and the mandatory-to-implement secure 2967 transport is TLS [RFC5246]. 2969 The NETCONF Access Control Model (NACM) [RFC8341] provides the means 2970 to restrict access for particular NETCONF or RESTCONF users to a 2971 preconfigured subset of all available NETCONF or RESTCONF operations 2972 and content. 2974 One subscription identifier can be used for two or more receivers of 2975 the same configured subscription. But due to the possibility of 2976 different access control permissions per receiver, it cannot be 2977 assumed that each receiver is getting identical updates. 2979 With configured subscriptions, one or more publishers could be used 2980 to overwhelm a receiver. Notification messages SHOULD NOT be sent to 2981 any receiver which does not support this specification. Receivers 2982 that do not want notification messages need only terminate or refuse 2983 any transport sessions from the publisher. 2985 When a receiver of a configured subscription gets a new 2986 "subscription-started" message for a known subscription where it is 2987 already consuming events, the receiver SHOULD retrieve any event 2988 records generated since the last event record was received. This can 2989 be accomplish by establishing a separate dynamic replay subscription 2990 with the same filtering criteria with the publisher", assuming the 2991 publisher supports the "replay" feature. 2993 For dynamic subscriptions, implementations need to protect against 2994 malicious or buggy subscribers which may send a large number 2995 "establish-subscription" requests, thereby using up system resources. 2996 To cover this possibility operators SHOULD monitor for such cases 2997 and, if discovered,take remedial action to limit the resources used, 2998 such as suspending or terminating a subset of the subscriptions or, 2999 if the underlying transport is session based, terminate the 3000 underlying transport session. 3002 There are a number of data nodes defined in this YANG module that are 3003 writable/creatable/deletable (i.e., config true, which is the 3004 default). These data nodes may be considered sensitive or vulnerable 3005 in some network environments. Write operations (e.g., edit-config) 3006 to these data nodes without proper protection can have a negative 3007 effect on network operations. These are the subtrees and data nodes 3008 where there is a specific sensitivity/vulnerability: 3010 Container: "/filters" 3012 o "stream-subtree-filter": updating a filter could increase the 3013 computational complexity of all referencing subscriptions. 3015 o "stream-xpath-filter": updating a filter could increase the 3016 computational complexity of all referencing subscriptions. 3018 Container: "/subscriptions" 3020 The following considerations are only relevant for configuration 3021 operations made upon configured subscriptions: 3023 o "configured-replay": can be used to send a large number of event 3024 records to a receiver. 3026 o "dependency": can be used to force important traffic to be queued 3027 behind less important updates. 3029 o "dscp": if unvalidated, can result in the sending of traffic with 3030 a higher priority marking than warranted. 3032 o "identifier": can overwrite an existing subscription, perhaps one 3033 configured by another entity. 3035 o "name": adding a new key entry can be used to attempt to send 3036 traffic to an unwilling receiver. 3038 o "replay-start-time": can be used to push very large logs, wasting 3039 resources. 3041 o "source-address": the configured address might not be able to 3042 reach a desired receiver. 3044 o "source-interface": the configured interface might not be able to 3045 reach a desired receiver. 3047 o "source-vrf": can place a subscription into a virtual network 3048 where receivers are not entitled to view the subscribed content. 3050 o "stop-time": could be used to terminate content at an inopportune 3051 time. 3053 o "stream": could set a subscription to an event stream containing 3054 no content permitted for the targeted receivers. 3056 o "stream-filter-ref": could be set to a filter which is irrelevant 3057 to the event stream. 3059 o "stream-subtree-filter": a complex filter can increase the 3060 computational resources for this subscription. 3062 o "stream-xpath-filter": a complex filter can increase the 3063 computational resources for this subscription. 3065 o "transport": this YANG choice node can be augmented with transport 3066 parameters which could then send the subscribed information to an 3067 undesired receiver". 3069 o "weighting": placing a large weight can overwhelm the dequeuing of 3070 other subscriptions. 3072 Some of the readable data nodes in this YANG module may be considered 3073 sensitive or vulnerable in some network environments. It is thus 3074 important to control read access (e.g., via get, get-config, or 3075 notification) to these data nodes. These are the subtrees and data 3076 nodes and their sensitivity/vulnerability: 3078 Container: "/streams" 3080 o "name": if access control is not properly configured, can expose 3081 system internals to those who should have no access to this 3082 information. 3084 o "replay-support": if access control is not properly configured, 3085 can expose logs to those who should have no access. 3087 Container: "/subscriptions" 3089 o "count-excluded": leaf can provide information about filtered 3090 event records. A network operator should have permissions to know 3091 about such filtering. 3093 o "subscription": different operational teams might have a desire to 3094 set varying subsets of subscriptions. Access control should be 3095 designed to permit read access to just the allowed set. 3097 Some of the RPC operations in this YANG module may be considered 3098 sensitive or vulnerable in some network environments. It is thus 3099 important to control access to these operations. These are the 3100 operations and their sensitivity/vulnerability: 3102 RPC: all 3104 o If a malicious or buggy subscriber sends an unexpectedly large 3105 number of RPCs, the result might be an excessive use of system 3106 resources on the publisher just to determine that these 3107 subscriptions should be declined. In such a situation, 3108 subscription interactions MAY be terminated by terminating the 3109 transport session. 3111 RPC: "delete-subscription" 3113 o No special considerations. 3115 RPC: "establish-subscription" 3117 o Subscriptions could overload a publisher's resources. For this 3118 reason, publishers MUST ensure that they have sufficient resources 3119 to fulfill this request or otherwise reject the request. 3121 RPC: "kill-subscription" 3123 o The "kill-subscription" RPC MUST be secured so that only 3124 connections with administrative rights are able to invoke this 3125 RPC. 3127 RPC: "modify-subscription" 3129 o Subscriptions could overload a publisher's resources. For this 3130 reason, publishers MUST ensure that they have sufficient resources 3131 to fulfill this request or otherwise reject the request. 3133 6. Acknowledgments 3135 For their valuable comments, discussions, and feedback, we wish to 3136 acknowledge Andy Bierman, Tim Jenkins, Martin Bjorklund, Kent Watsen, 3137 Balazs Lengyel, Robert Wilton, Sharon Chisholm, Hector Trevino, Susan 3138 Hares, Michael Scharf, and Guangying Zheng. 3140 7. References 3142 7.1. Normative References 3144 [I-D.draft-ietf-rtgwg-ni-model] 3145 Berger, L., Hopps, C., and A. Lindem, "YANG Network 3146 Instances", draft-ietf-rtgwg-ni-model-12 (work in 3147 progress), March 2018. 3149 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 3150 Requirement Levels", BCP 14, RFC 2119, 3151 DOI 10.17487/RFC2119, March 1997, 3152 . 3154 [RFC2474] Nichols, K., Blake, S., Baker, F., and D. Black, 3155 "Definition of the Differentiated Services Field (DS 3156 Field) in the IPv4 and IPv6 Headers", RFC 2474, 3157 DOI 10.17487/RFC2474, December 1998, 3158 . 3160 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, 3161 DOI 10.17487/RFC3688, January 2004, 3162 . 3164 [RFC5246] Dierks, T. and E. Rescorla, "The Transport Layer Security 3165 (TLS) Protocol Version 1.2", RFC 5246, 3166 DOI 10.17487/RFC5246, August 2008, 3167 . 3169 [RFC5277] Chisholm, S. and H. Trevino, "NETCONF Event 3170 Notifications", RFC 5277, DOI 10.17487/RFC5277, July 2008, 3171 . 3173 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for 3174 the Network Configuration Protocol (NETCONF)", RFC 6020, 3175 DOI 10.17487/RFC6020, October 2010, 3176 . 3178 [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., 3179 and A. Bierman, Ed., "Network Configuration Protocol 3180 (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, 3181 . 3183 [RFC6242] Wasserman, M., "Using the NETCONF Protocol over Secure 3184 Shell (SSH)", RFC 6242, DOI 10.17487/RFC6242, June 2011, 3185 . 3187 [RFC6991] Schoenwaelder, J., Ed., "Common YANG Data Types", 3188 RFC 6991, DOI 10.17487/RFC6991, July 2013, 3189 . 3191 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", 3192 RFC 7950, DOI 10.17487/RFC7950, August 2016, 3193 . 3195 [RFC7951] Lhotka, L., "JSON Encoding of Data Modeled with YANG", 3196 RFC 7951, DOI 10.17487/RFC7951, August 2016, 3197 . 3199 [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF 3200 Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, 3201 . 3203 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 3204 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 3205 May 2017, . 3207 [RFC8341] Bierman, A. and M. Bjorklund, "Network Configuration 3208 Access Control Model", STD 91, RFC 8341, 3209 DOI 10.17487/RFC8341, March 2018, 3210 . 3212 [RFC8342] Bjorklund, M., Schoenwaelder, J., Shafer, P., Watsen, K., 3213 and R. Wilton, "Network Management Datastore Architecture 3214 (NMDA)", RFC 8342, DOI 10.17487/RFC8342, March 2018, 3215 . 3217 [RFC8343] Bjorklund, M., "A YANG Data Model for Interface 3218 Management", RFC 8343, DOI 10.17487/RFC8343, March 2018, 3219 . 3221 [XPATH] Clark, J. and S. DeRose, "XML Path Language (XPath) 3222 Version 1.0", November 1999, 3223 . 3225 7.2. Informative References 3227 [I-D.draft-ietf-netconf-netconf-client-server] 3228 Watsen, K. and G. Wu, "NETCONF Client and Server Models", 3229 draft-ietf-netconf-netconf-client-server-06 (work in 3230 progress), June 2018. 3232 [I-D.draft-ietf-netconf-netconf-event-notifications] 3233 Clemm, Alexander., Voit, Eric., Gonzalez Prieto, Alberto., 3234 Nilsen-Nygaard, E., and A. Tripathy, "NETCONF support for 3235 event notifications", May 2018, 3236 . 3239 [I-D.draft-ietf-netconf-restconf-notif] 3240 Voit, Eric., Clemm, Alexander., Tripathy, A., Nilsen- 3241 Nygaard, E., and Alberto. Gonzalez Prieto, "Restconf and 3242 HTTP transport for event notifications", May 2018, 3243 . 3246 [I-D.ietf-netconf-yang-push] 3247 Clemm, Alexander., Voit, Eric., Gonzalez Prieto, Alberto., 3248 Tripathy, A., Nilsen-Nygaard, E., Bierman, A., and B. 3249 Lengyel, "YANG Datastore Subscription", May 2018, 3250 . 3253 [RFC7540] Belshe, M., Peon, R., and M. Thomson, Ed., "Hypertext 3254 Transfer Protocol Version 2 (HTTP/2)", RFC 7540, 3255 DOI 10.17487/RFC7540, May 2015, 3256 . 3258 [RFC7923] Voit, E., Clemm, A., and A. Gonzalez Prieto, "Requirements 3259 for Subscription to YANG Datastores", RFC 7923, 3260 DOI 10.17487/RFC7923, June 2016, 3261 . 3263 [RFC8071] Watsen, K., "NETCONF Call Home and RESTCONF Call Home", 3264 RFC 8071, DOI 10.17487/RFC8071, February 2017, 3265 . 3267 [RFC8340] Bjorklund, M. and L. Berger, Ed., "YANG Tree Diagrams", 3268 BCP 215, RFC 8340, DOI 10.17487/RFC8340, March 2018, 3269 . 3271 Appendix A. Example Configured Transport Augmentation 3273 This appendix provides a non-normative example of how the YANG model 3274 defined in Section 4 may be enhanced to incorporate the configuration 3275 parameters needed to support the transport connectivity process. In 3276 this example, NETCONF transport connectivity is explored. Other 3277 transports may be supported via a similar YANG model. For more on 3278 the overall need, see Section 2.5.7. 3280 Within the YANG model defined below are two main elements. First is 3281 a transport identity "netconf". This transport identity allows a 3282 configuration agent to define NETCONF as the selected type of 3283 transport for s subscription. Second is a YANG case augmentation 3284 "netconf" which is made to the 3285 "/subscriptions/subscription/receivers/receiver/transport" choice 3286 node of Section 4. Within this augmentation are the necessary 3287 transport configuration parameters. In this case the parameters 3288 consist of a leafref to the ietf-netconf-client.yang model of 3289 [I-D.draft-ietf-netconf-netconf-client-server]. This leafref itself 3290 allows referencing to the actual parameters which would be used to 3291 establish the transport connection. 3293 file 3294 "ietf-netconf-subscribed-notifications@2018-08-03.yang" 3295 module ietf-netconf-subscribed-notifications { 3296 yang-version 1.1; 3297 namespace 3298 "urn:ietf:params:xml:ns:yang:ietf-netconf-subscribed-notifications"; 3300 prefix nsn; 3302 import ietf-subscribed-notifications { 3303 prefix sn; 3304 } 3305 import ietf-netconf-client { 3306 prefix ncc; 3307 } 3309 organization "IETF NETCONF (Network Configuration) Working Group"; 3310 contact 3311 "WG Web: 3312 WG List: "; 3314 description 3315 "Defines NETCONF as a supported transport for subscribed event 3316 notifications."; 3318 revision 2018-08-03 { 3319 description 3320 "Initial version"; 3321 reference 3322 "RFC XXXX: Customized Subscriptions to a Publisher's Event Streams"; 3323 } 3325 identity netconf { 3326 base sn:transport; 3327 base sn:inline-address; 3328 description 3329 "NETCONF is used as a configured subscription transport for 3330 notification messages and state change notifications."; 3331 reference 3332 "RFC-6241: Network Configuration Protocol (NETCONF)"; 3333 } 3335 augment "/sn:subscriptions/sn:subscription/sn:receivers/sn:receiver" 3336 + "/sn:transport" { 3337 when 'derived-from(../../../../transport, "nsn:netconf")'; 3338 description 3339 "This augmentation allows NETCONF specific parameters to be 3340 exposed for a receiver."; 3341 case "netconf" { 3342 description 3343 "This case allows NETCONF specific parameters to be 3344 exposed for a receiver."; 3345 leaf netconf-endpoint { 3346 type leafref { 3347 path "/ncc:netconf-client/ncc:initiate/ncc:netconf-server" + 3348 "/ncc:endpoints/ncc:endpoint/ncc:name"; 3349 } 3350 mandatory true; 3351 description 3352 "Remote client which need to initiate the NETCONF transport if 3353 an existing NETCONF session from that client is not 3354 available."; 3355 } 3356 } 3357 } 3359 } 3360 3362 Figure 21: Example Transport Augmentation for NETCONF 3364 Appendix B. Changes between revisions 3366 (To be removed by RFC editor prior to publication) 3368 v14 - v15 3370 o Text tweaks. 3372 o Mandatory empty case "transport" added for transport parameters. 3373 This includes a new section and an appendix explaining it. 3375 v13 - v14 3377 o Removed the 'address' leaf. 3379 o Replay is now of type 'empty' for configured. 3381 v12 - v13 3383 o Tweaks from Kent's comments 3385 o Referenced in YANG model updated per Tom Petch's comments 3387 o Added leaf replay-previous-event-time 3389 o Renamed the event counters, downshifted the subscription states 3391 v11 - v12 3393 o Tweaks from Kent's, Tim's, and Martin's comments 3395 o Clarified dscp text, and made its own feature 3397 o YANG model tweaks alphabetizing, features. 3399 v10 - v11 3401 o access control filtering of events in streams included to match 3402 RFC5277 behavior 3404 o security considerations updated based on YANG template. 3406 o dependency QoS made non-normative on HTTP2 QoS 3408 o tree diagrams referenced for each figure using them 3410 o reference numbers placed into state machine figures 3411 o broke configured replay into its own section 3413 o many tweaks updates based on LC and YANG doctor reviews 3415 o trees and YANG model reconciled were deltas existed 3417 o new feature for interface originated. 3419 o dscp removed from the qos feature 3421 o YANG model updated in a way which collapses groups only used once 3422 so that they are part of the 'subscriptions' container. 3424 o alternative encodings only allowed for transports which support 3425 them. 3427 v09 - v10 3429 o Typos and tweaks 3431 v08 - v09 3433 o NMDA model supported. Non NMDA version at https://github.com/ 3434 netconf-wg/rfc5277bis/ 3436 o Error mechanism revamped to match to embedded implementations. 3438 o Explicitly identified error codes relevant to each RPC/ 3439 Notification 3441 v07 - v08 3443 o Split YANG trees to separate document subsections. 3445 o Clarified configured state machine based on Balazs comments, and 3446 moved it into the configured subscription subsections. 3448 o Normative reference to Network Instance model for VRF 3450 o One transport for all receivers of configured subscriptions. 3452 o QoS section moved in from yang-push 3454 v06 - v07 3456 o Clarification on state machine for configured subscriptions. 3458 v05 - v06 3459 o Made changes proposed by Martin, Kent, and others on the list. 3460 Most significant of these are stream returned to string (with the 3461 SYSLOG identity removed), intro section on 5277 relationship, an 3462 identity set moved to an enumeration, clean up of definitions/ 3463 terminology, state machine proposed for configured subscriptions 3464 with a clean-up of subscription state options. 3466 o JSON and XML become features. Also Xpath and subtree filtering 3467 become features 3469 o Terminology updates with event records, and refinement of filters 3470 to just event stream filters. 3472 o Encoding refined in establish-subscription so it takes the RPC's 3473 encoding as the default. 3475 o Namespaces in examples fixed. 3477 v04 - v05 3479 o Returned to the explicit filter subtyping of v00 3481 o stream object changed to 'name' from 'stream' 3483 o Cleaned up examples 3485 o Clarified that JSON support needs notification-messages draft. 3487 v03 - v04 3489 o Moved back to the use of RFC5277 one-way notifications and 3490 encodings. 3492 v03 - v04 3494 o Replay updated 3496 v02 - v03 3498 o RPCs and Notification support is identified by the Notification 3499 2.0 capability. 3501 o Updates to filtering identities and text 3503 o New error type for unsupportable volume of updates 3505 o Text tweaks. 3507 v01 - v02 3509 o Subscription status moved under receiver. 3511 v00 - v01 3513 o Security considerations updated 3515 o Intro rewrite, as well as scattered text changes 3517 o Added Appendix A, to help match this to related drafts in progress 3519 o Updated filtering definitions, and filter types in yang file, and 3520 moved to identities for filter types 3522 o Added Syslog as an event stream 3524 o HTTP2 moved in from YANG-Push as a transport option 3526 o Replay made an optional feature for events. Won't apply to 3527 datastores 3529 o Enabled notification timestamp to have different formats. 3531 o Two error codes added. 3533 v01 5277bis - v00 subscribed notifications 3535 o Kill subscription RPC added. 3537 o Renamed from 5277bis to Subscribed Notifications. 3539 o Changed the notification capabilities version from 1.1 to 2.0. 3541 o Extracted create-subscription and other elements of RFC5277. 3543 o Error conditions added, and made specific in return codes. 3545 o Simplified yang model structure for removal of 'basic' grouping. 3547 o Added a grouping for items which cannot be statically configured. 3549 o Operational counters per receiver. 3551 o Subscription-id and filter-id renamed to identifier 3553 o Section for replay added. Replay now cannot be configured. 3555 o Control plane notification renamed to subscription state 3556 notification 3558 o Source address: Source-vrf changed to string, default address 3559 option added 3561 o In yang model: 'info' changed to 'policy' 3563 o Scattered text clarifications 3565 v00 - v01 of 5277bis 3567 o YANG Model changes. New groupings for subscription info to allow 3568 restriction of what is changeable via RPC. Removed notifications 3569 for adding and removing receivers of configured subscriptions. 3571 o Expanded/renamed definitions from event server to publisher, and 3572 client to subscriber as applicable. Updated the definitions to 3573 include and expand on RFC 5277. 3575 o Removal of redundancy with other drafts 3577 o Many other clean-ups of wording and terminology 3579 Authors' Addresses 3581 Eric Voit 3582 Cisco Systems 3584 Email: evoit@cisco.com 3586 Alexander Clemm 3587 Huawei 3589 Email: ludwig@clemm.org 3591 Alberto Gonzalez Prieto 3592 Microsoft 3594 Email: alberto.gonzalez@microsoft.com 3596 Einar Nilsen-Nygaard 3597 Cisco Systems 3599 Email: einarnn@cisco.com 3600 Ambika Prasad Tripathy 3601 Cisco Systems 3603 Email: ambtripa@cisco.com