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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: Informational E. Voit 5 Expires: January 3, 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 July 2, 2018 16 Smart Filters for Push Updates 17 draft-clemm-netmod-push-smart-filters-00 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 January 3, 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 . . . . . . . . . . . . . . . . . . . . . 5 72 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 73 8. Normative References . . . . . . . . . . . . . . . . . . . . 6 74 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 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 TBD 231 6. IANA Considerations 233 TBD 235 7. Security Considerations 237 The application of Smart Filters requires a certain amount of 238 processing resources at the server. An attacker could attempt to 239 attack a server by creating YANG-push subscriptions with a large 240 number of complex Smart Filters in an attempt to diminish server 241 resources. Server implementations can guard against such scenarios 242 in several ways. For one, they can implement NACM in order to 243 require proper authorization for requests to be made. Second, server 244 implementations can reject requests made for a a larger number of 245 Smart Filters than the implementation can reasonably sustain. 247 8. Normative References 249 [notif-sub] 250 Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard, 251 E., and A. Tripathy, "Custom Subscriptions to a 252 Publisher's Event Streams", June 2018, 253 . 256 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 257 Requirement Levels", BCP 14, RFC 2119, 258 DOI 10.17487/RFC2119, March 1997, 259 . 261 [RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688, 262 DOI 10.17487/RFC3688, January 2004, 263 . 265 [RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for 266 the Network Configuration Protocol (NETCONF)", RFC 6020, 267 DOI 10.17487/RFC6020, October 2010, 268 . 270 [RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., 271 and A. Bierman, Ed., "Network Configuration Protocol 272 (NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011, 273 . 275 [RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language", 276 RFC 7950, DOI 10.17487/RFC7950, August 2016, 277 . 279 [RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF 280 Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017, 281 . 283 [RFC8072] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Patch 284 Media Type", RFC 8072, DOI 10.17487/RFC8072, February 285 2017, . 287 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 288 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 289 May 2017, . 291 [yang-push] 292 Clemm, A., Voit, E., Gonzalez Prieto, A., Tripathy, A., 293 Nilsen-Nygaard, E., Bierman, A., and B. Lengyel, 294 "Subscribing to YANG datastore push updates", July 2018, 295 . 298 Authors' Addresses 300 Alexander Clemm 301 Huawei - Futurewei Technologies, Inc. 302 2330 Central Expressway 303 Santa Clara, CA 95050 304 USA 306 Email: ludwig@clemm.org 308 Eric Voit 309 Cisco Systems 311 Email: evoit@cisco.com 313 Xufeng Liu 314 Volta Networks 316 Email: xufeng.liu.ietf@gmail.com 318 Igor Bryskin 319 Huawei 321 Email: igor.bryskin@huawei.com 323 Tianran Zhou 324 Huawei 326 Email: zhoutianran@huawei.com 327 Guangying Zheng 328 Huawei 330 Email: zhengguangying@huawei.com 332 Henk Birkholz 333 Fraunhofer SIT 335 Email: henk.birkholz@sit.fraunhofer.de