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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-13) exists of draft-ietf-ippm-6man-pdm-option-00 == Outdated reference: A later version (-06) exists of draft-chen-ippm-coloring-based-ipfpm-framework-03 Summary: 0 errors (**), 0 flaws (~~), 4 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group A. Morton 3 Internet-Draft AT&T Labs 4 Intended status: Informational June 30, 2015 5 Expires: January 1, 2016 7 Active and Passive Metrics and Methods (and everything in-between, or 8 Hybrid) 9 draft-ietf-ippm-active-passive-00 11 Abstract 13 This memo provides clear definitions for Active and Passive 14 performance assessment. The construction of Metrics and Methods can 15 be described as Active or Passive. Some methods may use a subset of 16 both active and passive attributes, and we refer to these as Hybrid 17 Methods. 19 Status of This Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at http://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on January 1, 2016. 36 Copyright Notice 38 Copyright (c) 2015 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (http://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 55 2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 3 56 3. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 3 57 3.1. Performance Metric . . . . . . . . . . . . . . . . . . . 3 58 3.2. Method of Measurement . . . . . . . . . . . . . . . . . . 4 59 3.3. Observation Point . . . . . . . . . . . . . . . . . . . . 4 60 3.4. Active Methods . . . . . . . . . . . . . . . . . . . . . 4 61 3.5. Active Metric . . . . . . . . . . . . . . . . . . . . . . 4 62 3.6. Passive Methods . . . . . . . . . . . . . . . . . . . . . 5 63 3.7. Passive Metric . . . . . . . . . . . . . . . . . . . . . 5 64 3.8. Hybrid Methods and Metrics . . . . . . . . . . . . . . . 6 65 4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 6 66 4.1. Graphical Representation . . . . . . . . . . . . . . . . 6 67 4.2. Discussion of PDM . . . . . . . . . . . . . . . . . . . . 8 68 4.3. Discussion of "Coloring" Method . . . . . . . . . . . . . 9 69 5. Security considerations . . . . . . . . . . . . . . . . . . . 9 70 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 71 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 10 72 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 10 73 8.1. Normative References . . . . . . . . . . . . . . . . . . 10 74 8.2. Informative References . . . . . . . . . . . . . . . . . 10 75 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 11 77 1. Introduction 79 The adjectives "active" and "passive" have been used for many years 80 to distinguish two different classes of Internet performance 81 assessment. The first Passive and Active Measurement (PAM) 82 Conference was held in 2000, but the earliest proceedings available 83 on-line are from the second PAM conference in 2001 84 [https://www.ripe.net/ripe/meetings/pam-2001]. 86 The notions of "active" and "passive" are well-established. In 87 general: 89 An Active metric or method depends on a dedicated measurement 90 packet stream and observations of the stream. 92 A Passive metric or method depends *solely* on observation of one 93 or more existing packet streams. The streams only serve 94 measurement when they are observed for that purpose, and are 95 present whether measurements take place or not. 97 As new techniques for assessment emerge it is helpful to have clear 98 definitions of these notions. This memo provides more detailed 99 definitions, defines a new category for combinations of traditional 100 active and passive techniques, and discusses means to evaluate new 101 techniques as they emerge. 103 This memo provides definitions for Active and Passive Metrics and 104 Methods based on long usage in the Internet measurement community, 105 and especially the Internet Engineering Task Force. 107 1.1. Requirements Language 109 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 110 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 111 document are to be interpreted as described in RFC 2119 [RFC2119]. 113 2. Purpose and Scope 115 The scope of this memo is to define and describe Active and Passive 116 versions of metrics and methods which are consistent with the long- 117 time usage of these adjectives in the Internet measurement community 118 and especially the Internet Engineering Task Force. Since the 119 science of measurement is expanding, we provide a category for 120 combinations of the traditional extremes, treating Active and Passive 121 as a continuum and designating combinations of their attributes as 122 Hybrid methods. 124 Further, this memo's purpose includes describing multiple dimensions 125 in which to evaluate methods as they emerge. 127 3. Terms and Definitions 129 This section defines the key terms of the memo. Some definitions use 130 the notion of "stream of interest" which is synonymous with 131 "population of interest" defined in clause 6.1.1 of ITU-T 132 Recommendation Y.1540. The definitions are consistent with 133 [I-D.zheng-ippm-framework-passive]. 135 3.1. Performance Metric 137 The standard definition of a quantity, produced in an assessment of 138 performance and/or reliability of the network, which has an intended 139 utility and is carefully specified to convey the exact meaning of a 140 measured value. (This definition is consistent with that of 141 Performance Metric in RFC 2330 and RFC 6390). 143 3.2. Method of Measurement 145 The procedure or set of operations having the object of determining a 146 Measured Value or Measurement Result. 148 3.3. Observation Point 150 See section 2 of [RFC7011] for this definition (a location in the 151 network where packets can be observed), and related definitions. The 152 comparable term defined in IETF literature on Active measurement is 153 Measurement Point, see section 4.1 of [RFC5835]. Two terms have come 154 into use describing similar actions at the identified point in the 155 network path. 157 3.4. Active Methods 159 Active measurement methods have the following attributes: 161 1. Commonly, the packet stream of interest is generated as the basis 162 of measurement. Another packet stream may be generated to 163 increase traffic load, but the loading stream itself may not be 164 measured. 166 2. The packets in the stream of interest have fields (or are 167 augmented or modified to include fields) which are dedicated to 168 measurement. Since measurement usually requires determining the 169 corresponding packets at multiple measurement points, a sequence 170 number is the most common information dedicated to measurement. 172 3. The Source and Destination of the packet stream of interest are 173 usually known a' priori. 175 4. The characteristics of the packet stream of interest are known at 176 the Source at least, and may be communicated to Destination as 177 part of the method. 179 When adding traffic to the network for measurement, Active Methods 180 influence the quantities measured to some degree, and those 181 performing tests should take steps to quantify the effect(s) and/or 182 minimize such effects. 184 3.5. Active Metric 186 An Active Metric incorporates one or more of the aspects of Active 187 Methods in the metric definition. 189 For example, IETF metrics for IP performance (developed according to 190 the [RFC2330] framework) include the Source packet stream 191 characteristics as metric input parameters, and also specify the 192 packet characteristics (Type-P) and Source and Destination IP 193 addresses (with their implications on both stream treatment and 194 interfaces associated with measurement points). 196 3.6. Passive Methods 198 Passive measurement methods are 200 o based solely on observations of undisturbed and unmodified packet 201 stream of interest 203 o dependent on the existence of one or more packet streams to supply 204 the stream of interest 206 o dependent on the presence of the packet stream of interest at one 207 or more designated observation points. 209 Some passive methods simply observe and collect information on all 210 packets that pass Observation Point(s), while others filter the 211 packets as a first step and only collect information on packets that 212 match the filter criteria, and thereby narrow the stream of interest. 214 It is common that passive methods are conducted at one or more 215 Observation Points. Passive methods to assess Performance Metrics 216 often require multiple observation points, e.g., to assess latency of 217 packet transfer across a network path between two Observation Points. 218 In this case, the observed packets must include enough information to 219 determine the corresponding packets at different Observation Points. 221 Communication of the observations (in some form) to a collector is an 222 essential aspect of Passive Methods. In some configurations, the 223 traffic load associated with results export to a collector may 224 influence the network performance. However, the collection of 225 results is not unique to Passive Methods, and the load from 226 management and operations of measurement systems must always be 227 considered for potential effects on the measured values. 229 3.7. Passive Metric 231 Passive Metrics apply to observations of packet traffic (traffic 232 flows in [RFC7011]). 234 Passive performance metrics are assessed independent of the packets 235 or traffic flows, and solely through observation. Some refer to such 236 assessments as "out-of-band". 238 One example of passive performance metrics for IP packet transfer can 239 be found in ITU-T Recommendation Y.1540, where the metrics are 240 defined on the basis of reference events as packet pass reference 241 points, so the metrics are agnostic to the distinction between active 242 and passive when the necessary packet correspondence can be derived 243 from the observed stream of interest when required. 245 3.8. Hybrid Methods and Metrics 247 Methods of Measurement which use a combination of Active Methods and 248 Passive Methods, to assess Active Metrics, Passive Metrics, or new 249 metrics derived from the a' priori knowledge and observations of the 250 stream of interest. ITU-T Recommendation Y.1540 defines metrics are 251 applicable to the hybrid category, since packet correspondence at 252 different observation/reference points could be derived from "fields 253 which are dedicated to measurement", but otherwise the methods are 254 passive. 256 With respect to the stream of interest, Hybrid methods fit in the 257 continuum as follows, in terms of what happens at the Source(or 258 Observation Point nearby): 260 o If you generate the stream of interest => Active 262 o If you augment of modify a stream of interest => Hybrid 264 o If you solely observe a stream of interest => Passive 266 4. Discussion 268 This section illustrates the definitions and presents some examples. 270 4.1. Graphical Representation 272 If we compare the Active and Passive Methods, there are at least two 273 dimensions on which methods can be evaluated. This evaluation space 274 may be useful when a method is a combination of the two alternative 275 methods. 277 The two dimensions (initially chosen) are: 279 1. The degree to which the stream of interest effects overall 280 network conditions experienced by that stream and other streams. 281 This is a key dimension for Active measurement error analysis. 282 (Comment: There is also the notion of time averages - a 283 measurement stream may have significant effect while it is 284 present, but the stream is only generated 0.1% of the time. On 285 the other hand, observations alone have no effect on network 286 performance. To keep things simple, we consider the stream 287 effect only when it is present.) 289 2. The degree to which stream characteristics are know a' priori. 290 There are methodological advantages of knowing the source stream 291 characteristics, and having complete control of the stream 292 characteristics. For example, knowing the number of packets in a 293 stream allows more efficient operation of the measurement 294 receiver, and so is an asset for active measurement methods. 295 Passive methods (with no sample filter) have few clues available 296 to anticipate what the protocol first packet observed will use or 297 how many packets will comprise the flow, but once the standard 298 protocol of a flow is known the possibilities narrow (for some 299 compliant flows). Therefore this is a key dimension for Passive 300 measurement error analysis. 302 There are a few examples we can plot on a two-dimensional space. We 303 can anchor the dimensions with reference point descriptions. 305 Effect of the measured stream on network conditions 306 ^ Max 307 |* Active using max capacity stream 308 | 309 | 310 | 311 | 312 |* Active using stream with load of typical user 313 | 314 | 315 | 316 |* Active using extremely sparse, randomized stream 317 | * PDM Passive 318 | Min * 319 +----------------------------------------------------------------| 320 | | 321 Stream No Stream 322 Characteristics Characteristics 323 completely Known 324 known 326 We recognize that method categorization could be based on additional 327 dimensions, but this would require a different graphical approach. 329 For example, "effect of stream of interest on network conditions" 330 could easily be further qualified into: 332 1. effect on the performance of the stream of interest itself: for 333 example, choosing a packet marking or DSCP resulting in domain 334 treatment as a real-time stream (as opposed to default/best- 335 effort marking. 337 2. effect on unmeasured streams that share the path and/or 338 bottlenecks: for example, an extremely sparse measured stream of 339 minimal size packets typically has little effect on other flows 340 (and itself), while a stream designed to characterize path 341 capacity may effect all other flows passing through the capacity 342 bottleneck (including itself). 344 3. effect on network conditions resulting in network adaptation: for 345 example, a network monitoring load and congestion conditions 346 might change routing, placing some flows to alternate paths to 347 mitigate the congestion. 349 At present, we have combined 1 and 2 on one axis, as examination of 350 examples indicates strong correlation of affects on this pair, and 351 network adaptation is not addressed. As suggestions emerge we will 352 re-examine the possibilities. 354 It is apparent that different methods of IP network measurement can 355 produce different results, even when measuring the same path at the 356 same time. The two dimensions of the graph help to understand how 357 the results might change with the method chosen. For example, an 358 Active Method to assess throughput adds some amount of traffic to the 359 network which might result in lower throughput for all streams. 360 However, a Passive Method to assess throughput can also err on the 361 low side due to unknown limitations of the hosts providing traffic, 362 competition for host resources, limitations of the network interface, 363 or private sub-networks that are not an intentional part of the path, 364 etc. And Hybrid Methods could easily suffer from both forms of 365 error. Another example of potential errors stems from the pitfalls 366 of using an Active stream with known bias, such as a periodic stream 367 defined in [RFC3432]. The strength of modelling periodic streams 368 (like VoIP) is a potential weakness when extending the measured 369 results to other application whose streams are non-periodic. The 370 solutions are to model the application streams more exactly with an 371 Active Method, or accept the risks and potential errors with the 372 Passive Method discussed above. 374 4.2. Discussion of PDM 376 In [I-D.ietf-ippm-6man-pdm-option], an IPv6 Option Header for 377 Performance and Diagnostic Measurements (PDM) is described which 378 (when added to the stream of interest at strategic interfaces) 379 supports performance measurements. This method processes a user 380 traffic stream and adds "fields which are dedicated to measurement". 381 Thus: 383 o The method may have a small effect on the measured stream and 384 other streams in the network. 386 o The measured stream has unknown characteristics until it is 387 processed to add the PDM Option header. 389 We conclude that this is a Hybrid method, having at least one 390 characteristic of both active and passive methods. 392 4.3. Discussion of "Coloring" Method 394 Draft [I-D.tempia-opsawg-p3m], proposed to color packets by re- 395 writing a field of the stream at strategic interfaces to support 396 performance measurements. This method processes a user traffic 397 stream and inserts "fields which are dedicated to measurement". 398 Thus: 400 o The method may have a small effect on the measured stream and 401 other streams in the network (smaller than PDM above). 403 o The measured stream has unknown characteristics until it is 404 processed to add the coloring in the header, and the stream could 405 be measured and time-stamped during that process. 407 We note that [I-D.chen-ippm-coloring-based-ipfpm-framework] proposes 408 a method similar to [I-D.tempia-opsawg-p3m], and ippm-list discussion 409 indicates [I-D.chen-ippm-coloring-based-ipfpm-framework] may be 410 covered by the same IPR as [I-D.tempia-opsawg-p3m]. 412 We conclude that this is a Hybrid method, having at least one 413 characteristic of both active and passive methods. 415 5. Security considerations 417 When considering privacy of those involved in measurement or those 418 whose traffic is measured, there is sensitive information 419 communicated and observed at observation and measurement points 420 described above. We refer the reader to the privacy considerations 421 described in the Large Scale Measurement of Broadband Performance 422 (LMAP) Framework [I-D.ietf-lmap-framework], which covers active and 423 passive measurement techniques and supporting material on measurement 424 context. 426 6. IANA Considerations 428 This memo makes no requests for IANA consideration. 430 7. Acknowledgements 432 Thanks to Mike Ackermann for asking the right question, and for 433 several suggestions on terminology. Brian Trammell provided key 434 terms and references for the passive category. Tiziano Ionta 435 reviewed the draft and suggested the classification for the 436 "coloring" method of measurement. Nalini Elkins identified several 437 areas for clarification following her review. Bill Jouris reviewed 438 01 editorially and suggested several improvements. 440 8. References 442 8.1. Normative References 444 [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, 445 "Framework for IP Performance Metrics", RFC 2330, May 446 1998. 448 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 449 Requirement Levels", BCP 14, RFC 2119, March 1997. 451 [RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network 452 performance measurement with periodic streams", RFC 3432, 453 November 2002. 455 [RFC5835] Morton, A. and S. Van den Berghe, "Framework for Metric 456 Composition", RFC 5835, April 2010. 458 [RFC7011] Claise, B., Trammell, B., and P. Aitken, "Specification of 459 the IP Flow Information Export (IPFIX) Protocol for the 460 Exchange of Flow Information", STD 77, RFC 7011, September 461 2013. 463 8.2. Informative References 465 [I-D.ietf-lmap-framework] 466 Eardley, P., Morton, A., Bagnulo, M., Burbridge, T., 467 Aitken, P., and A. Akhter, "A framework for Large-Scale 468 Measurement of Broadband Performance (LMAP)", draft-ietf- 469 lmap-framework-14 (work in progress), April 2015. 471 [I-D.ietf-ippm-6man-pdm-option] 472 Elkins, N. and M. Ackermann, "IPv6 Performance and 473 Diagnostic Metrics (PDM) Destination Option", draft-ietf- 474 ippm-6man-pdm-option-00 (work in progress), June 2015. 476 [I-D.tempia-opsawg-p3m] 477 Capello, A., Cociglio, M., Castaldelli, L., and A. Bonda, 478 "A packet based method for passive performance 479 monitoring", draft-tempia-opsawg-p3m-04 (work in 480 progress), February 2014. 482 [I-D.chen-ippm-coloring-based-ipfpm-framework] 483 Chen, M., Zheng, L., Mirsky, G., and G. Fioccola, "IP Flow 484 Performance Measurement Framework", draft-chen-ippm- 485 coloring-based-ipfpm-framework-03 (work in progress), 486 February 2015. 488 [I-D.zheng-ippm-framework-passive] 489 Zheng, L., Elkins, N., Lingli, D., Ackermann, M., and G. 490 Mirsky, "Framework for IP Passive Performance 491 Measurements", draft-zheng-ippm-framework-passive-03 (work 492 in progress), February 2015. 494 Author's Address 496 Al Morton 497 AT&T Labs 498 200 Laurel Avenue South 499 Middletown, NJ 500 USA 502 Email: acmorton@att.com