-
Notifications
You must be signed in to change notification settings - Fork 0
/
Copy pathdraft-clemm-netconf-push-smart-filters-ps.txt
392 lines (256 loc) · 14.9 KB
/
draft-clemm-netconf-push-smart-filters-ps.txt
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
Network Working Group A. Clemm
Internet-Draft Futurewei Technologies, Inc.
Intended status: Informational E. Voit
Expires: April 19, 2018 Cisco Systems
X. Liu
Jabil
I. Bryskin
T. Zhou
G. Zheng
Huawei
H. Birkholz
Fraunhofer SIT
October 16, 2017
Smart filters for Push Updates - Problem Statement
draft-clemm-netconf-push-smart-filters-ps-00
Abstract
This document defines a problem statement for Smart Filters for Push
Updates. Smart Filters for Push Updates (referred to simply as
"Smart Filters" in the context of this document) allows to filter
push updates based on values of pushed objects and/or state, such as
previous updates. Smart Filters provide an important building block
for service assurance and network automation.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 19, 2018.
Clemm, et al. Expires April 19, 2018 [Page 1]
Internet-Draft October 2017
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Key Words . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Definitions and Acronyms . . . . . . . . . . . . . . . . . . 3
4. Problem Statement . . . . . . . . . . . . . . . . . . . . . . 3
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
6. Security Considerations . . . . . . . . . . . . . . . . . . . 5
7. Normative References . . . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
YANG-Push [yang-push] allows client applications to subscribe to
continuous datastore updates without needing to poll. YANG-Push
subscriptions allow client applications to select which datanodes are
of interest. For this purpose, filters that act as node selectors
are offered. However, what is currently not supported are filters
that filter updates based on values, such as sending updates only
when the value falls within a certain range. Also not supported are
filters that would require additional state, such as sending updates
only when the value exceeds a certain threshold for the first time
but not again until the threshold is cleared. We refer to such
filters as "smart filters", with further subcategories of "smart
stateless filters" and "smart stateful filters", respectively.
Smart filters involve more complex subscription and implementation
semantics than the simple selection filters that are currently
offered as part of YANG-Push. They involve post processing of
updates that goes beyond basic update generation for polling
avoidance and place additional intelligence at the server. Because
of this, smart filter functionality was not included in the YANG-Push
specification, although it was recognized that YANG-Push could be
Clemm, et al. Expires April 19, 2018 [Page 2]
Internet-Draft October 2017
extended to include such functionality if needed. This is the
purpose of this specification.
Smart filters facilitate service assurance, because they allow client
applications to focus on "outliers" and updates that signify
exceptions and conditions of interest have the biggest operational
significance. They save network resources by avoiding the need to
stream updates that would be discarded anyway, and allow applications
to scale better since larger networks imply a larger amount of smart
filtering operations delegated away from the application to the
network. Smart filters also facilitate network automation as they
constitute an important ingredient to specify triggers for automated
actions.
2. Key Words
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
3. Definitions and Acronyms
Smart Filter: A filter that involves some processing, such as
comparing values or differentiating behavior depending on state.
TCA: Threshold Crossing Alert.
YANG-Push: A server capability that allows client applications to
subscribe to network management datastore updates.
4. Problem Statement
YANG-Push provides client applications with the ability to subscribe
to continuous updates from network management datastores, obviating
the need to perform polling and resulting in more robust and
efficient applications. However, many applications do not require
every update, only updates that are of certain interest.
For example, an update concerning interface utilization may be only
needed when a certain utilization level is breached. Sending
continuous updates when utilization is low might divert processing
resources away from updates regarding interfaces whose utilization
level may reach a critical point that requires attention. Doing so
will require a filter based on an object value. Even sending
continuous updates when utilization is high may be too much and
counterproductive. It may be sufficient to send an update when a
Clemm, et al. Expires April 19, 2018 [Page 3]
Internet-Draft October 2017
threshold is breached to raise a flag of attention, but then not to
continue sending updates while the condition still persists but
simply let the client application know when the threshold is cleared.
This behavior cannot be accomplished simply by a value-based filter,
but requires additional state to be maintained (so that the server
has a memory whether or not the condition of a breached threshold has
already been reported in prior update cycles).
What is needed are "Smart Filters" that provide the ability to apply
filters based on object values, possibly also state state. Smart
Filters are useful for Service Assurance applications that need to
monitor operational data for values that fall outside normal
operational ranges. They are also useful for network automation, in
which automated actions are automatically triggered based on when
certain events in the network occur while certain conditions hold. A
YANG-Push subscription with a smart filter can in effect act as a
source for such events. Combined with an optional check for a
condition when an event is observed, this can serve as the basis of
action triggers.
Smart Filters for Push Updates will provide support for the following
features:
o Support for smart filter extensions to YANG-Push subscriptions.
The targeted model takes a "base" YANG-Push subscription and
subjects updates to an additional filtering stage that is based on
value.
o Support for refined on-change update semantics that allow client
to distinguish whether object values were omitted or included
because the object was created or deleted, or because the object's
value fell outside filter range.
o Support for selected stateful filters:
* This includes specifically support for generalized "threshold
crossing alert" filters, or filters that provide an update only
when an object's value passes a filter for the first time, and
not again until the object's value passes a counter filter. In
effect, the support involves attaching filter and counter
filter to an object, including a switch at the object
indicating which filter is in effect, and providing a
distinction in the update which filter (e.g. onset of clear)
was applied.
* It may include additional filters, such a "recent high water
mark" filters that allow to specify a time horizon until the
current high water mark clears. A recent high water mark
Clemm, et al. Expires April 19, 2018 [Page 4]
Internet-Draft October 2017
filter sends an update to an object only if its new value is
greater than the last value that had been previously reported.
It is easy to conceive of filters that are very smart and powerful
yet also very complex. While filters as defined in YANG-Push may be
a tad too simple for the applications envisioned here, it is
important to keep filters still simple enough to ensure broad
implementation and support by networking devices. The purpose of
smart filters defined in this effort is to address the 90% of cases
that can be addressed using 10% of the complexity. Items like the
following will therefore be outside the scope:
o Filters that involve freely programmable logic.
o Filters that aggregate or otherwise process information over time.
An example would be filters that compute an aggregate over a time
series of data (e.g. an object's average or top percentile value)
o Filters that aggregate or compare an object's values with those of
other objects (e.g. the maximum or average from objects over a
list).
5. IANA Considerations
Not applicable
6. Security Considerations
The application of smart filters requires a certain amount of
processing resources at the server. An attacker could attempt to
attack a server by creating YANG-push subscriptions with a large
number of complex smart filters in an attempt to diminish server
resources. Server implementations can guard against such scenarios
in several ways. For one, they can implement NACM in order to
require proper authorization for requests to be made. Second, server
implementations can reject requests made for a a larger number of
smart filters than the implementation can reasonably sustain.
7. Normative References
[notif-sub]
Voit, E., Clemm, A., Gonzalez Prieto, A., Nilsen-Nygaard,
E., and A. Tripathy, "Custom subscription to event
notifications", July 2017,
<https://datatracker.ietf.org/doc/
draft-ietf-netconf-subscribed-notifications/>.
Clemm, et al. Expires April 19, 2018 [Page 5]
Internet-Draft October 2017
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3688] Mealling, M., "The IETF XML Registry", BCP 81, RFC 3688,
DOI 10.17487/RFC3688, January 2004,
<https://www.rfc-editor.org/info/rfc3688>.
[RFC6020] Bjorklund, M., Ed., "YANG - A Data Modeling Language for
the Network Configuration Protocol (NETCONF)", RFC 6020,
DOI 10.17487/RFC6020, October 2010,
<https://www.rfc-editor.org/info/rfc6020>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<https://www.rfc-editor.org/info/rfc6241>.
[RFC7950] Bjorklund, M., Ed., "The YANG 1.1 Data Modeling Language",
RFC 7950, DOI 10.17487/RFC7950, August 2016,
<https://www.rfc-editor.org/info/rfc7950>.
[RFC8040] Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", RFC 8040, DOI 10.17487/RFC8040, January 2017,
<https://www.rfc-editor.org/info/rfc8040>.
[RFC8072] Bierman, A., Bjorklund, M., and K. Watsen, "YANG Patch
Media Type", RFC 8072, DOI 10.17487/RFC8072, February
2017, <https://www.rfc-editor.org/info/rfc8072>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[yang-push]
Clemm, A., Voit, E., Gonzalez Prieto, A., Tripathy, A.,
Nilsen-Nygaard, E., Bierman, A., and B. Lengyel,
"Subscribing to YANG datastore push updates", August 2017,
<https://datatracker.ietf.org/doc/
draft-ietf-netconf-yang-push/>.
Authors' Addresses
Clemm, et al. Expires April 19, 2018 [Page 6]
Internet-Draft October 2017
Alexander Clemm
Futurewei Technologies, Inc.
2330 Central Expressway
Santa Clara, CA 95050
USA
Email: [email protected]
Eric Voit
Cisco Systems
Email: [email protected]
Xufeng Liu
Jabil
Igor Bryskin
Huawei
Tianran Zhou
Huawei
Guangying Zheng
Huawei
Henk Birkholz
Fraunhofer SIT
Clemm, et al. Expires April 19, 2018 [Page 7]