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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Unused Reference: 'RFC6020' is defined on line 477, but no explicit reference was found in the text == Unused Reference: 'RFC6241' is defined on line 482, but no explicit reference was found in the text == Unused Reference: 'RFC8040' is defined on line 491, but no explicit reference was found in the text == Unused Reference: 'RFC8072' is defined on line 495, but no explicit reference was found in the text Summary: 0 errors (**), 0 flaws (~~), 6 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Clemm 3 Internet-Draft Huawei - Futurewei Technologies, Inc. 4 Intended status: Standards Track E. Voit 5 Expires: April 25, 2019 Cisco Systems 6 X. Liu 7 Volta Networks 8 I. Bryskin 9 T. Zhou 10 G. Zheng 11 Huawei 12 H. Birkholz 13 Fraunhofer SIT 14 October 22, 2018 16 Smart Filters for Push Updates 17 draft-clemm-netmod-push-smart-filters-01 19 Abstract 21 This document defines a YANG model for Smart Filters for push 22 updates. Smart Filters allow to filter push updates based on values 23 of pushed datastore nodes and/or state, such as previous updates. 24 Smart Filters provide an important building block for service 25 assurance and network automation. 27 This revision of the document is intended as a placeholder, 28 containing the problem statement of draft-clemm-netconf-push-smart- 29 filters-ps-00 that has recently expired. The YANG model itself still 30 needs to be defined. 32 Status of This Memo 34 This Internet-Draft is submitted in full conformance with the 35 provisions of BCP 78 and BCP 79. 37 Internet-Drafts are working documents of the Internet Engineering 38 Task Force (IETF). Note that other groups may also distribute 39 working documents as Internet-Drafts. The list of current Internet- 40 Drafts is at https://datatracker.ietf.org/drafts/current/. 42 Internet-Drafts are draft documents valid for a maximum of six months 43 and may be updated, replaced, or obsoleted by other documents at any 44 time. It is inappropriate to use Internet-Drafts as reference 45 material or to cite them other than as "work in progress." 47 This Internet-Draft will expire on April 25, 2019. 49 Copyright Notice 51 Copyright (c) 2018 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (https://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 Table of Contents 66 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 67 2. Key Words . . . . . . . . . . . . . . . . . . . . . . . . . . 3 68 3. Definitions and Acronyms . . . . . . . . . . . . . . . . . . 3 69 4. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3 70 5. Smart Filter Data Model . . . . . . . . . . . . . . . . . . . 5 71 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 72 7. Security Considerations . . . . . . . . . . . . . . . . . . . 10 73 8. Normative References . . . . . . . . . . . . . . . . . . . . 10 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 76 1. Introduction 78 YANG-Push [yang-push] allows client applications to subscribe to 79 continuous datastore updates without needing to poll. YANG-Push 80 subscriptions allow client applications to select which datastore 81 nodes are of interest. For this purpose, filters that act as node 82 selectors are offered. However, what is currently not supported are 83 filters that filter updates based on values, such as sending updates 84 only when the value falls within a certain range. Also not supported 85 are filters that would require additional state, such as sending 86 updates only when the value exceeds a certain threshold for the first 87 time but not again until the threshold is cleared. We refer to such 88 filters as "Smart Filters", with further subcategories of "smart 89 stateless filters" and "smart stateful filters", respectively. 91 Smart Filters involve more complex subscription and implementation 92 semantics than the simple selection filters that are currently 93 offered as part of YANG-Push. They involve post processing of 94 updates that goes beyond basic update generation for polling 95 avoidance and place additional intelligence at the server. Because 96 of this, Smart Filter functionality was not included in the YANG-Push 97 specification, although it was recognized that YANG-Push could be 98 extended to include such functionality if needed. This is the 99 purpose of this specification. 101 Smart Filters facilitate service assurance, because they allow client 102 applications to focus on "outliers" and updates that signify 103 exceptions and conditions of interest have the biggest operational 104 significance. They save network resources by avoiding the need to 105 stream updates that would be discarded anyway, and allow applications 106 to scale better since larger networks imply a larger amount of Smart 107 Filtering operations delegated away from the application to the 108 network. Smart Filters also facilitate network automation as they 109 constitute an important ingredient to specify triggers for automated 110 actions. 112 2. Key Words 114 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 115 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 116 "OPTIONAL" in this document are to be interpreted as described in BCP 117 14 [RFC2119] [RFC8174] when, and only when, they appear in all 118 capitals, as shown here. 120 3. Definitions and Acronyms 122 Datastore node: An instance of management information in a 123 datastore. Also known as "object". 125 Smart Filter: A filter that involves some processing, such as 126 comparing values or differentiating behavior depending on state. 128 TCA: Threshold Crossing Alert. 130 YANG-Push: A server capability that allows client applications to 131 subscribe to network management datastore updates. 133 4. Problem Statement 135 YANG-Push provides client applications with the ability to subscribe 136 to continuous updates from network management datastores, obviating 137 the need to perform polling and resulting in more robust and 138 efficient applications. However, many applications do not require 139 every update, only updates that are of certain interest. 141 For example, an update concerning interface utilization may be only 142 needed when a certain utilization level is breached. Sending 143 continuous updates when utilization is low might divert processing 144 resources away from updates regarding interfaces whose utilization 145 level may reach a critical point that requires attention. Doing so 146 will require a filter based on an object value. Even sending 147 continuous updates when utilization is high may be too much and 148 counterproductive. It may be sufficient to send an update when a 149 threshold is breached to raise a flag of attention, but then not to 150 continue sending updates while the condition still persists but 151 simply let the client application know when the threshold is cleared. 152 This behavior cannot be accomplished simply by a value-based filter, 153 but requires additional state to be maintained (so that the server 154 has a memory whether or not the condition of a breached threshold has 155 already been reported in prior update cycles). 157 What is needed are "Smart Filters" that provide the ability to apply 158 filters based on object values, possibly also state state. Smart 159 Filters are useful for Service Assurance applications that need to 160 monitor operational data for values that fall outside normal 161 operational ranges. They are also useful for network automation, in 162 which automated actions are automatically triggered based on when 163 certain events in the network occur while certain conditions hold. A 164 YANG-Push subscription with a Smart Filter can in effect act as a 165 source for such events. Combined with an optional check for a 166 condition when an event is observed, this can serve as the basis of 167 action triggers. 169 Smart Filters for Push Updates will provide support for the following 170 features: 172 o Support for Smart Filter extensions to YANG-Push subscriptions. 173 The targeted model takes a "base" YANG-Push subscription and 174 subjects updates to an additional filtering stage that is based on 175 value. 177 o Support for selected stateful filters: 179 * This includes specifically support for generalized "threshold 180 crossing alert" filters, or filters that provide an update only 181 when a datastore node's value passes a filter for the first 182 time, and not again until the datastore node's value passes a 183 counter filter. In effect, the support involves attaching 184 filter and counter filter to a datastore node, including a 185 switch at the datastore node indicating which filter is in 186 effect, and providing a distinction in the update which filter 187 (e.g. onset of clear) was applied. 189 * It may include additional filters, such a "recent high water 190 mark" filters that allow to specify a time horizon until the 191 current high water mark clears. A recent high water mark 192 filter sends an update to an object only if its new value is 193 greater than the last value that had been previously reported. 195 o In addition to new filters, support for features to make them 196 easier to use: 198 * Support for refined on-change update semantics that allow 199 client to distinguish whether datastore node values were 200 omitted or included because the datastore node was created or 201 deleted, or because the datastore node's value fell outside 202 filter range. 204 * Support for a heartbeat that indicates that a filter is still 205 in effect after a longer period of inactivity. 207 It is easy to conceive of filters that are very smart and powerful 208 yet also very complex. While filters as defined in YANG-Push may be 209 a tad too simple for the applications envisioned here, it is 210 important to keep filters still simple enough to ensure broad 211 implementation and support by networking devices. The purpose of 212 Smart Filters defined in this effort is to address the 90% of cases 213 that can be addressed using 10% of the complexity. Items like the 214 following will therefore be outside the scope: 216 o Filters that involve freely programmable logic. 218 o Filters that aggregate or otherwise process information over time. 219 An example would be filters that compute an aggregate over a time 220 series of data (e.g. a datastore node's average or top percentile 221 value) 223 o Filters that aggregate or compare values of several datastore 224 nodes (e.g. the maximum or average from datastore nodes in a 225 list). 227 5. Smart Filter Data Model 229 The following section contains an initial YANG data model for smart 230 filters. The model is at this point still incomplete and included as 231 a starting point only. At this point, the model defines a simple 232 threshold filter. When used with a subscription, objects that meet 233 the filter criterion (i.e. the threshold comparison) are included in 234 the update whereas any other object is filtered. 236 The model will be extended to define a full "smart threshold" model 237 in a later revision. This will add the feature of a hysteresis 238 threshold, i.e. a counter threshold that allows to define when a 239 crossed threshold should be cleared. The value of the hysteresis 240 threshold can be set to a lower value than the threshold itself to 241 avoid unnecessary updates in case of oscillations). It will also add 242 a notion of state to remember whether a threshold crossing has 243 already been reported, to avoid repeated inclusion of objects in 244 updates that remain above their threshold. By including metadata, 245 clients will be able to distinguish between the violation and the 246 clearing of thresholds. 248 The model will furthermore be extended for smart filters that are not 249 threshold-related, such as the previously mentioned recent high water 250 marks. 252 file "ietf-smart-filter@2018-10-22.yang" 253 module ietf-smart-filter { 254 yang-version "1.1"; 255 namespace "urn:ietf:params:xml:ns:yang:ietf-smart-filter"; 256 prefix "sf"; 258 import ietf-yang-types { 259 prefix yang; 260 reference 261 "RFC 6991: Common YANG Data Types"; 262 } 264 import ietf-subscribed-notifications { 266 prefix sn; 267 reference 268 "draft-ietf-netconf-subscribed-notifications: 269 Customized Subscriptions to a Publisher's Event Streams 271 NOTE TO RFC Editor: Please replace above reference to 272 draft-ietf-netconf-subscribed-notifications with RFC number 273 when published (i.e. RFC xxxx)."; 274 } 276 organization "IETF"; 277 contact 278 "WG Web: 279 WG List: 281 Editor: Alexander Clemm 282 284 Editor: Eric Voit 285 287 Editor: Xufeng Liu 288 290 Editor: Igor Bryskin 291 293 Editor: Tianran Zhou 294 296 Editor: Guangying Zheng 297 299 Editor: Henk Birkholz 300 "; 302 description 303 "This module contains YANG specifications for smart filter. 305 Copyright (c) 2018 IETF Trust and the persons identified as authors 306 of the code. All rights reserved. 308 Redistribution and use in source and binary forms, with or without 309 modification, is permitted pursuant to, and subject to the license 310 terms contained in, the Simplified BSD License set forth in Section 311 4.c of the IETF Trust's Legal Provisions Relating to IETF Documents 312 (https://trustee.ietf.org/license-info). 314 This version of this YANG module is part of 315 draft-clemm-netmod-push-smart-filters-01; see the RFC itself 316 for full legal notices. 318 NOTE TO RFC EDITOR: Please replace above reference to 319 with RFC number when 320 published (i.e. RFC xxxx)."; 322 revision 2018-10-22 { 323 description 324 "Initial revision. 325 NOTE TO RFC EDITOR: 326 (1)Please replace the above revision date to 327 the date of RFC publication when published. 328 (2) Please replace the date in the file name 329 (ietf-smart-filter@2018-10-22.yang) to the date of RFC 330 publication. 331 (3) Please replace the following reference to 332 draft-clemm-netmod-push-smart-filters-01 with RFC number when 333 published (i.e. RFC xxxx)."; 334 reference 335 "draft-clemm-netmod-push-smart-filters-01"; 337 } 339 /* 340 * IDENTITIES 341 */ 343 /* Smart-filter type identities */ 345 identity smart-filter { 346 description 347 "A base identity that represents the smart filter types. "; 348 } 350 identity smart-filter-threshold { 351 base smart-filter; 352 description 353 "An identity instance based on smart-filter, which support 354 filter the push data by fix threshold value."; 355 } 357 /* 358 * TYPE DEFINITIONS 359 */ 360 typedef sf-op-type { 361 type enumeration { 362 enum eq { 363 description "equal to"; 364 } 365 enum gt { 366 description "greater than"; 367 } 368 enum ge { 369 description "greater than or equal to"; 370 } 371 enum lt { 372 description "less than"; 373 } 374 enum le { 375 description "less than or equal to"; 376 } 377 } 378 description "A boolean comparator for an object and a data value. 379 Include: eq, gt, ge, lt, le."; 380 } 382 /* 383 * GROUP DEFINITIONS 384 */ 385 grouping sf-threshold{ 386 description 387 "the group for threshold filter"; 388 leaf filter-node { 389 if-feature "sn:xpath"; 390 type yang:xpath1.0; 391 description 392 "This parameter contains an XPath expression identifying 393 the node of the target filter."; 394 } 396 leaf threshold-value { 397 type string; 398 description "threshold value"; 399 } 401 leaf op-type { 402 type sf-op-type; 403 description "comparison operator"; 404 } 405 } 407 //augment statements 408 augment "/sn:subscriptions/sn:subscription" { 409 description "add the smart filter container"; 410 container smart-filter { 411 description "It concludes filter configurations"; 413 choice filter-type { 414 description 415 "Select different smart filter"; 416 case threshold-filter { 417 description 418 "threshold-filter"; 419 uses sf-threshold; 420 } 421 } 422 } 423 } 424 } 425 427 6. IANA Considerations 429 RFC Ed.: In this section, replace all occurrences of 'XXXX' with the 430 actual RFC number (and remove this note). 432 IANA is requested to assign a new URI from the IETF XML Registry 433 [RFC3688]. The following URI is suggested: 435 URI: urn:ietf:params:xml:ns:yang:ietf-smart-filter 436 Registrant Contact: The IESG. 437 XML: N/A; the requested URI is an XML namespace. 439 This document also requests a new YANG module name in the YANG Module 440 Names registry [RFC7950] with the following suggestion: 442 name: ietf-ioam 443 namespace: urn:ietf:params:xml:ns:yang:ietf-smart-filter 444 prefix: sf 445 reference: RFC XXXX 447 7. Security Considerations 449 The application of Smart Filters requires a certain amount of 450 processing resources at the server. An attacker could attempt to 451 attack a server by creating YANG-push subscriptions with a large 452 number of complex Smart Filters in an attempt to diminish server 453 resources. Server implementations can guard against such scenarios 454 in several ways. For one, they can implement NACM in order to 455 require proper authorization for requests to be made. Second, server 456 implementations can reject requests made for a a larger number of 457 Smart Filters than the implementation can reasonably sustain. 459 8. Normative References 461 [notif-sub] 462 Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard, 463 E., and A. Tripathy, "Custom Subscriptions to a 464 Publisher's Event Streams", June 2018, 465 . 468 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 469 Requirement Levels", BCP 14, RFC 2119, 470 DOI 10.17487/RFC2119, March 1997, 471 . 473 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, 474 DOI 10.17487/RFC3688, January 2004, 475 . 477 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for 478 the Network Configuration Protocol (NETCONF)", RFC 6020, 479 DOI 10.17487/RFC6020, October 2010, 480 . 482 [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., 483 and A. Bierman, Ed., "Network Configuration Protocol 484 (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, 485 . 487 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", 488 RFC 7950, DOI 10.17487/RFC7950, August 2016, 489 . 491 [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF 492 Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, 493 . 495 [RFC8072] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Patch 496 Media Type", RFC 8072, DOI 10.17487/RFC8072, February 497 2017, . 499 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 500 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 501 May 2017, . 503 [yang-push] 504 Clemm, A., Voit, E., Gonzalez Prieto, A., Tripathy, A., 505 Nilsen-Nygaard, E., Bierman, A., and B. Lengyel, 506 "Subscribing to YANG datastore push updates", July 2018, 507 . 510 Authors' Addresses 512 Alexander Clemm 513 Huawei - Futurewei Technologies, Inc. 514 2330 Central Expressway 515 Santa Clara, CA 95050 516 USA 518 Email: ludwig@clemm.org 520 Eric Voit 521 Cisco Systems 523 Email: evoit@cisco.com 524 Xufeng Liu 525 Volta Networks 527 Email: xufeng.liu.ietf@gmail.com 529 Igor Bryskin 530 Huawei 532 Email: igor.bryskin@huawei.com 534 Tianran Zhou 535 Huawei 537 Email: zhoutianran@huawei.com 539 Guangying Zheng 540 Huawei 542 Email: zhengguangying@huawei.com 544 Henk Birkholz 545 Fraunhofer SIT 547 Email: henk.birkholz@sit.fraunhofer.de