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diff --git a/doc/rfc/rfc7799.txt b/doc/rfc/rfc7799.txt new file mode 100644 index 0000000..6fac1a2 --- /dev/null +++ b/doc/rfc/rfc7799.txt @@ -0,0 +1,787 @@ + + + + + + +Internet Engineering Task Force (IETF) A. Morton +Request for Comments: 7799 AT&T Labs +Category: Informational May 2016 +ISSN: 2070-1721 + + + Active and Passive Metrics and Methods + (with Hybrid Types In-Between) + +Abstract + + This memo provides clear definitions for Active and Passive + performance assessment. The construction of Metrics and Methods can + be described as either "Active" or "Passive". Some methods may use a + subset of both Active and Passive attributes, and we refer to these + as "Hybrid Methods". This memo also describes multiple dimensions to + help evaluate new methods as they emerge. + +Status of This Memo + + This document is not an Internet Standards Track specification; it is + published for informational purposes. + + This document is a product of the Internet Engineering Task Force + (IETF). It represents the consensus of the IETF community. It has + received public review and has been approved for publication by the + Internet Engineering Steering Group (IESG). Not all documents + approved by the IESG are a candidate for any level of Internet + Standard; see Section 2 of RFC 5741. + + Information about the current status of this document, any errata, + and how to provide feedback on it may be obtained at + http://www.rfc-editor.org/info/rfc7799. + +Copyright Notice + + Copyright (c) 2016 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 + (http://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. + + + +Morton Informational [Page 1] + +RFC 7799 Active, Passive and Hybrid May 2016 + + +Table of Contents + + 1. Introduction ....................................................2 + 1.1. Requirements Language ......................................3 + 2. Purpose and Scope ...............................................3 + 3. Terms and Definitions ...........................................3 + 3.1. Performance Metric .........................................3 + 3.2. Method of Measurement ......................................4 + 3.3. Observation Point ..........................................4 + 3.4. Active Methods .............................................4 + 3.5. Active Metric ..............................................5 + 3.6. Passive Methods ............................................5 + 3.7. Passive Metric .............................................6 + 3.8. Hybrid Methods and Metrics .................................6 + 4. Discussion ......................................................8 + 4.1. Graphical Representation ...................................8 + 4.2. Discussion of PDM .........................................10 + 4.3. Discussion of "Coloring" Method ...........................11 + 4.4. Brief Discussion of OAM Methods ...........................11 + 5. Security Considerations ........................................12 + 6. References .....................................................12 + 6.1. Normative References ......................................12 + 6.2. Informative References ....................................13 + Acknowledgements ..................................................14 + Author's Address ..................................................14 + +1. Introduction + + The adjectives "Active" and "Passive" have been used for many years + to distinguish between two different classes of Internet performance + assessment. The first Passive and Active Measurement (PAM) + Conference was held in 2000, but the earliest proceedings available + online are from the second PAM conference in 2001 + <https://www.ripe.net/ripe/meetings/pam-2001>. + + The notions of "Active" and "Passive" are well-established. In + general: + + o An Active Metric or Method depends on a dedicated measurement + packet stream and observations of the stream. + + o A Passive Metric or Method depends *solely* on observation of one + or more existing packet streams. The streams only serve + measurement when they are observed for that purpose, and are + present whether or not measurements take place. + + + + + + +Morton Informational [Page 2] + +RFC 7799 Active, Passive and Hybrid May 2016 + + + As new techniques for assessment emerge, it is helpful to have clear + definitions of these notions. This memo provides more-detailed + definitions, defines a new category for combinations of traditional + Active and Passive techniques, and discusses dimensions to evaluate + new techniques as they emerge. + + This memo provides definitions for Active and Passive Metrics and + Methods based on long usage in the Internet measurement community, + and especially the Internet Engineering Task Force (IETF). This memo + also describes the combination of fundamental Active and Passive + categories that are called Hybrid Methods and Metrics. + +1.1. Requirements Language + + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this + document are to be interpreted as described in [RFC2119]. + +2. Purpose and Scope + + The scope of this memo is to define and describe Active and Passive + versions of metrics and methods that are consistent with the long- + time usage of these adjectives in the Internet measurement community + and especially the IETF. Since the science of measurement is + expanding, we provide a category for combinations of the traditional + extremes, treating Active and Passive as a continuum and designating + combinations of their attributes as Hybrid Methods. + + Further, this memo's purpose includes describing multiple dimensions + to evaluate new methods as they emerge. + +3. Terms and Definitions + + This section defines the key terms of the memo. Some definitions use + the notion of "stream of interest", which is synonymous with + "population of interest" defined in clause 6.1.1 of ITU-T + Recommendation Y.1540 [Y.1540]. These definitions will be useful for + any work in progress, such as [PASSIVE] (with which there is already + good consistency). + +3.1. Performance Metric + + The standard definition of a quantity, produced in an assessment of + performance and/or reliability of the network, which has an intended + utility and is carefully specified to convey the exact meaning of a + measured value. (This definition is consistent with that of + Performance Metric in [RFC2330] and [RFC6390]). + + + + +Morton Informational [Page 3] + +RFC 7799 Active, Passive and Hybrid May 2016 + + +3.2. Method of Measurement + + The procedure or set of operations having the object of determining a + Measured Value or Measurement Result. + +3.3. Observation Point + + See Section 2 of [RFC7011] for the definition of Observation Point (a + location in the network where packets can be observed), and related + definitions. The comparable term defined in IETF literature on + Active measurement is "Measurement Point" (see Section 4.1 of + [RFC5835]). Both of these terms have come into use describing + similar actions at the identified point in the network path. + +3.4. Active Methods + + Active Methods of Measurement have the following attributes: + + o Active Methods generate packet streams. Commonly, the packet + stream of interest is generated as the basis of measurement. + Sometimes, the adjective "synthetic" is used to categorize Active + measurement streams [Y.1731]. An accompanying packet stream or + streams may be generated to increase overall traffic load, though + the loading stream(s) may not be measured. + + o The packets in the stream of interest have fields or field values + (or are augmented or modified to include fields or field values) + that are dedicated to measurement. Since measurement usually + requires determining the corresponding packets at multiple + measurement points, a sequence number is the most common + information dedicated to measurement, and it is often combined + with a timestamp. + + o The Source and Destination of the packet stream of interest are + usually known a priori. + + o The characteristics of the packet stream of interest are known at + the Source (at least), and may be communicated to the Destination + as part of the method. Note that some packet characteristics will + normally change during packet forwarding. Other changes along the + path are possible, see [STDFORM]. + + When adding traffic to the network for measurement, Active Methods + influence the quantities measured to some degree, and those + performing tests should take steps to quantify the effect(s) and/or + minimize such effects. + + + + + +Morton Informational [Page 4] + +RFC 7799 Active, Passive and Hybrid May 2016 + + +3.5. Active Metric + + An Active Metric incorporates one or more of the aspects of Active + Methods in the metric definition. + + For example, IETF metrics for IP performance (developed according to + the framework described in [RFC2330]) include the Source-packet + stream characteristics as metric-input parameters, and also specify + the packet characteristics (Type-P) and Source and Destination IP + addresses (with their implications on both stream treatment and + interfaces associated with measurement points). + +3.6. Passive Methods + + Passive Methods of Measurement are: + + o based solely on observations of an undisturbed and unmodified + packet stream of interest (in other words, the method of + measurement MUST NOT add, change, or remove packets or fields or + change field values anywhere along the path). + + o dependent on the existence of one or more packet streams to supply + the stream of interest. + + o dependent on the presence of the packet stream of interest at one + or more designated Observation Points. + + Some Passive Methods simply observe and collect information on all + packets that pass Observation Point(s), while others filter the + packets as a first step and only collect information on packets that + match the filter criteria, and thereby narrow the stream of interest. + + It is common that Passive Methods are conducted at one or more + Observation Points. Passive Methods to assess Performance Metrics + often require multiple Observation Points, e.g., to assess the + latency of packet transfer across a network path between two + Observation Points. In this case, the observed packets must include + enough information to determine the corresponding packets at + different Observation Points. + + Communication of the observations (in some form) to a collector is an + essential aspect of Passive Methods. In some configurations, the + traffic load generated when communicating (or exporting) the Passive + Method results to a collector may itself influence the measured + network's performance. However, the collection of results is not + unique to Passive Methods, and the load from management and + operations of measurement systems must always be considered for + potential effects on the measured values. + + + +Morton Informational [Page 5] + +RFC 7799 Active, Passive and Hybrid May 2016 + + +3.7. Passive Metric + + Passive Metrics apply to observations of packet traffic (traffic + flows in [RFC7011]). + + Passive performance metrics are assessed independently of the packets + or traffic flows, and solely through observation. Some refer to such + assessments as "out of band". + + One example of Passive Performance Metrics for IP packet transfer can + be found in ITU-T Recommendation Y.1540 [Y.1540], where the metrics + are defined on the basis of reference events generated as packets + pass reference points. The metrics are agnostic to the distinction + between Active and Passive when the necessary packet correspondence + can be derived from the observed stream of interest as required. + +3.8. Hybrid Methods and Metrics + + Hybrid Methods are Methods of Measurement that use a combination of + Active Methods and Passive Methods, to assess Active Metrics, Passive + Metrics, or new metrics derived from the a priori knowledge and + observations of the stream of interest. ITU-T Recommendation Y.1540 + [Y.1540] defines metrics that are also applicable to the hybrid + categories, since packet correspondence at different observation/ + reference points could be derived from "fields or field values which + are dedicated to measurement", but otherwise the methods are Passive. + + There are several types of Hybrid Methods, as categorized below. + + With respect to a *single* stream of interest, Hybrid Type I methods + fit in the continuum as follows, in terms of what happens at the + Source (or Observation Point nearby): + + o Generation of the stream of interest => Active + + o Augmentation or modification of the stream of interest, or + employment of methods that modify the treatment of the stream => + Hybrid Type I + + o Observation of a stream of interest => Passive + + As an example, consider the case where the method generates traffic + load stream(s), and observes an existing stream of interest according + to the criteria for Passive Methods. Since loading streams are an + aspect of Active Methods, the stream of interest is not "solely + observed", and the measurements involve a single stream of interest + whose treatment has been modified by the presence of the load. + Therefore, this is a Hybrid Type I method. + + + +Morton Informational [Page 6] + +RFC 7799 Active, Passive and Hybrid May 2016 + + + We define Hybrid Type II as follows: Methods that employ two or more + different streams of interest with some degree of mutual coordination + (e.g., one or more Active streams and one or more undisturbed and + unmodified packet streams) to collect both Active and Passive Metrics + and enable enhanced characterization from additional joint analysis. + [HYBRID] presents a problem statement for Hybrid Type II Methods and + Metrics. Note that one or more Hybrid Type I streams could be + substituted for the Active streams or undisturbed streams in the + mutually coordinated set. It is the Type II Methods where unique + Hybrid Metrics are anticipated to emerge. + + Methods based on a combination of a single (generated) Active stream + and Passive observations applied to the stream of interest at + intermediate Observation Points are also Hybrid Methods. However, + [RFC5644] already defines these as Spatial Metrics and Methods. It + is possible to replace the Active stream of [RFC5644] with a Hybrid + Type I stream and measure Spatial Metrics (but this was unanticipated + when [RFC5644] was developed). + + The table below illustrates the categorization of methods (where + "Synthesis" refers to a combination of Active and Passive Method + attributes). + + | Single Stream | Multiple Simultaneous + | of Interest | Streams of Interest + | | from Different Methods + ==================================================================== + Single Fundamental | Active or Passive | + Method | | + + Synthesis of | Hybrid Type I | + Fundamental Methods | | + + Multiple Methods | Spatial Metrics | Hybrid Type II + | [RFC5644] | + + There may be circumstances where results measured with Hybrid Methods + can be considered equivalent to those measured with Passive Methods. + This notion references the possibility of a "class C" where packets + of different Type-P are treated equally in network implementation, as + described in Section 13 of [RFC2330] and using the terminology for + paths from Section 5 of [RFC2330]: + + Hybrid Methods of measurement that augment or modify packets of a + "class C" in a host should produce results equivalent to Passive + Methods of Measurement when hosts accessing and links transporting + these packets along the path (other than those performing + augmentation/modification) treat packets from both categories of + + + +Morton Informational [Page 7] + +RFC 7799 Active, Passive and Hybrid May 2016 + + + methods (with and without the augmentation/modification) as the + same "class C". The Passive Methods of Measurement represent the + Ground Truth when comparing results between Passive and Hybrid + Methods, and this comparison should be conducted to confirm the + "class C" treatment. + +4. Discussion + + This section illustrates the definitions and presents some examples. + +4.1. Graphical Representation + + If we compare the Active and Passive Methods, there are at least two + dimensions on which methods can be evaluated. This evaluation space + may be useful when a method is a combination of the two alternative + methods. + + The two dimensions (initially chosen) are: + + Y-Axis: "Effect of the measured stream on network conditions". The + degree to which the stream of interest biases overall network + conditions experienced by that stream and other streams. This is + a key dimension for Active measurement error analysis. (Comment: + There is also the notion of time averages -- a measurement stream + may have significant effect while it is present, but the stream is + only generated 0.1% of the time. On the other hand, observations + alone have no effect on network performance. To keep these + dimensions simple, we consider the stream effect only when it is + present, but note that reactive networks defined in [RFC7312] may + exhibit bias for some time beyond the life of a stream.) + + X-Axis: "a priori Stream Knowledge". The degree to which stream + characteristics are known a priori. There are methodological + advantages of knowing the source stream characteristics, and + having complete control of the stream characteristics. For + example, knowing the number of packets in a stream allows more- + efficient operation of the measurement receiver, and so is an + asset for Active Methods of Measurement. Passive Methods (with no + sample filter) have few clues available to anticipate what + protocol the first packet observed will use or how many packets + will comprise the flow; once the standard protocol of a flow is + known, the possibilities narrow (for some compliant flows). + Therefore, this is a key dimension for Passive measurement error + analysis. + + There are a few examples we can plot on a two-dimensional space. We + can anchor the dimensions with reference point descriptions. + + + + +Morton Informational [Page 8] + +RFC 7799 Active, Passive and Hybrid May 2016 + + + Y-Axis:Effect of the measured stream on network conditions + ^ Max + |* Active using max capacity stream + | + | + | + | + |* Active using stream with load of typical user + | + | + | + |* Active using extremely sparse, randomized stream + | * PDM Passive + | Min * + +----------------------------------------------------------------| + | | + Stream X-Axis: a priori Stream Knowledge No Stream + Characteristics Characteristics + Completely Known + Known + + (In the graph above, "PDM" refers to [PDMOPTION], an IPv6 Option + Header for Performance and Diagnostic Measurements, described in + Section 4.2.) + + We recognize that method categorization could be based on additional + dimensions, but this would require a different graphical approach. + + For example, "effect of stream of interest on network conditions" + could easily be further qualified into: + + 1. effect on the performance of the stream of interest itself: for + example, choosing a packet marking or Differentiated Services + Code Point (DSCP) resulting in domain treatment as a real-time + stream (as opposed to default/best-effort marking). + + 2. effect on unmeasured streams that share the path and/or + bottlenecks: for example, an extremely sparse measured stream of + minimal size packets typically has little effect on other flows + (and itself), while a stream designed to characterize path + capacity may affect all other flows passing through the capacity + bottleneck (including itself). + + 3. effect on network conditions resulting in network adaptation: for + example, a network monitoring load and congestion conditions + might change routing, placing some flows on alternate paths to + mitigate the congestion. + + + + +Morton Informational [Page 9] + +RFC 7799 Active, Passive and Hybrid May 2016 + + + We have combined 1 and 2 on the Y-axis, as examination of examples + indicates strong correlation of the effects in this pair, and network + adaptation is not addressed. + + It is apparent that different methods of IP network measurement can + produce different results, even when measuring the same path at the + same time. The two dimensions of the graph help us to understand how + the results might change with the method chosen. For example, an + Active Method to assess throughput adds some amount of traffic to the + network, which might result in lower throughput for all streams. + However, a Passive Method to assess throughput can also err on the + low side due to unknown limitations of the hosts providing traffic, + competition for host resources, limitations of the network interface, + or private sub-networks that are not an intentional part of the path, + etc. Hybrid Methods could easily suffer from both forms of error. + Another example of potential errors stems from the pitfalls of using + an Active stream with known a bias, such as a periodic stream defined + in [RFC3432]. The strength of modeling periodic streams (like Voice + over IP (VoIP)) is a potential weakness when extending the measured + results to other application whose streams are non-periodic. The + solutions are to model the application streams more exactly with an + Active Method or to accept the risks and potential errors with the + Passive Method discussed above. + +4.2. Discussion of PDM + + In [PDMOPTION], an IPv6 Option Header for Performance and Diagnostic + Measurements (PDM) is described which, when added to the stream of + interest at strategic interfaces, supports performance measurements. + This method processes a user traffic stream and adds "fields which + are dedicated to measurement" (the measurement intent is made clear + in the title of this option). Thus: + + o The method intends to have a minor effect on the measured stream + and other streams in the network. There are conditions where this + intent may not be realized. + + o The measured stream has unknown characteristics until it is + processed to add the PDM Option header. Note that if the packet + MTU is exceeded after adding the header, the intent to have a + minor effect will not be realized. + + We conclude that this is a Hybrid Type I method, having at least one + characteristic of both Active and Passive Methods for a single stream + of interest. + + + + + + +Morton Informational [Page 10] + +RFC 7799 Active, Passive and Hybrid May 2016 + + +4.3. Discussion of "Coloring" Method + + [OPSAWG], proposed to color packets by re-writing a field of the + stream at strategic interfaces to support performance measurements + (noting that this is a difficult operation at an intermediate point + on an encrypted Virtual Private Network). This method processes a + user traffic stream and inserts "fields or values which are dedicated + to measurement". Thus: + + o The method intends to have a minor effect on the measured stream + and other streams in the network (less than PDM above). There are + conditions where this intent may not be realized. + + o The measured stream has unknown characteristics until it is + processed to add the coloring in the header, and the stream could + be measured and time-stamped during that process. + + We note that [COLORING] proposes a method similar to [OPSAWG], as + discussion on the IPPM mailing list revealed. + + We conclude that this is a Hybrid Type I method, having at least one + characteristic of both Active and Passive Methods for a single stream + of interest. + +4.4. Brief Discussion of OAM Methods + + Many Operations, Administration, and Management (OAM) methods exist + beyond the IP layer. For example, [Y.1731] defines several different + measurement methods that we would classify as follows: + + o Loss Measurement (LM) occasionally injects frames with a count of + previous frames since the last LM message. We conclude LM is + Hybrid Type I, because this method processes a user traffic stream + and augments the stream of interest with frames having "fields + which are dedicated to measurement". + + o Synthetic Loss Measurement (SLM) and Delay Measurement (DM) + methods both inject dedicated measurement frames, so the "stream + of interest is generated as the basis of measurement". We + conclude that SLM and DM methods are Active Methods. + + We also recognize the existence of alternate terminology used in OAM + at layers other than IP. Readers are encouraged to consult [RFC6374] + for MPLS Loss and Delay measurement terminology, for example. + + + + + + + +Morton Informational [Page 11] + +RFC 7799 Active, Passive and Hybrid May 2016 + + +5. Security Considerations + + When considering the security and privacy of those involved in + measurement or those whose traffic is measured, there is sensitive + information communicated and observed at observation and measurement + points described above, and protocol issues to consider. We refer + the reader to the security and privacy considerations described in + the Large-Scale Measurement of Broadband Performance (LMAP) Framework + [RFC7594], which covers Active and Passive measurement techniques and + supporting material on measurement context. + +6. References + +6.1. Normative References + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, + DOI 10.17487/RFC2119, March 1997, + <http://www.rfc-editor.org/info/rfc2119>. + + [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, + "Framework for IP Performance Metrics", RFC 2330, + DOI 10.17487/RFC2330, May 1998, + <http://www.rfc-editor.org/info/rfc2330>. + + [RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network + performance measurement with periodic streams", RFC 3432, + DOI 10.17487/RFC3432, November 2002, + <http://www.rfc-editor.org/info/rfc3432>. + + [RFC5644] Stephan, E., Liang, L., and A. Morton, "IP Performance + Metrics (IPPM): Spatial and Multicast", RFC 5644, + DOI 10.17487/RFC5644, October 2009, + <http://www.rfc-editor.org/info/rfc5644>. + + [RFC5835] Morton, A., Ed. and S. Van den Berghe, Ed., "Framework for + Metric Composition", RFC 5835, DOI 10.17487/RFC5835, April + 2010, <http://www.rfc-editor.org/info/rfc5835>. + + [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New + Performance Metric Development", BCP 170, RFC 6390, + DOI 10.17487/RFC6390, October 2011, + <http://www.rfc-editor.org/info/rfc6390>. + + + + + + + + +Morton Informational [Page 12] + +RFC 7799 Active, Passive and Hybrid May 2016 + + + [RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken, + "Specification of the IP Flow Information Export (IPFIX) + Protocol for the Exchange of Flow Information", STD 77, + RFC 7011, DOI 10.17487/RFC7011, September 2013, + <http://www.rfc-editor.org/info/rfc7011>. + + [RFC7312] Fabini, J. and A. Morton, "Advanced Stream and Sampling + Framework for IP Performance Metrics (IPPM)", RFC 7312, + DOI 10.17487/RFC7312, August 2014, + <http://www.rfc-editor.org/info/rfc7312>. + + [RFC7594] Eardley, P., Morton, A., Bagnulo, M., Burbridge, T., + Aitken, P., and A. Akhter, "A Framework for Large-Scale + Measurement of Broadband Performance (LMAP)", RFC 7594, + DOI 10.17487/RFC7594, September 2015, + <http://www.rfc-editor.org/info/rfc7594>. + +6.2. Informative References + + [COLORING] + Chen, M., Ed., Zheng, L., Ed., Mirsky, G., Ed., Fioccola, + G., Ed., and T. Mizrahi, Ed., "IP Flow Performance + Measurement Framework", Work in Progress, draft-chen-ippm- + coloring-based-ipfpm-framework-06, March 2016. + + [HYBRID] Trammell, B., Zheng, L., Berenguer, S., and M. Bagnulo, + "Hybrid Measurement using IPPM Metrics", Work in Progress, + draft-trammell-ippm-hybrid-ps-01, February 2014. + + [OPSAWG] Capello, A., Cociglio, M., Castaldelli, L., and A. Bonda, + "A packet based method for passive performance + monitoring", Work in Progress, draft-tempia-opsawg-p3m-04, + February 2014. + + [PASSIVE] Zheng, L., Elkins, N., Lingli, D., Ackermann, M., and G. + Mirsky, "Framework for IP Passive Performance + Measurements", Work in Progress, draft-zheng-ippm- + framework-passive-03, February 2015. + + [PDMOPTION] + Elkins, N. and M. Ackermann, "IPv6 Performance and + Diagnostic Metrics (PDM) Destination Option", Work in + Progress, draft-ietf-ippm-6man-pdm-option-02, April 2016. + + + + + + + + +Morton Informational [Page 13] + +RFC 7799 Active, Passive and Hybrid May 2016 + + + [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay + Measurement for MPLS Networks", RFC 6374, + DOI 10.17487/RFC6374, September 2011, + <http://www.rfc-editor.org/info/rfc6374>. + + [STDFORM] Morton, A., Fabini, J., Elkins, N., Ackermann, M., and V. + Hegde, "Updates for IPPM's Active Metric Framework: + Packets of Type-P and Standard-Formed Packets", Work in + Progress, draft-morton-ippm-2330-stdform-typep-02, + December 2015. + + [Y.1540] ITU-T, "Internet protocol data communication service - IP + packet transfer and availability performance parameters", + March 2011, + <https://www.itu.int/rec/T-REC-Y.1540-201103-I/en>. + + [Y.1731] ITU-T, "Operation, administration and management (OAM) + functions and mechanisms for Ethernet-based networks", + August 2015, + <https://www.itu.int/rec/T-REC-G.8013-201508-I/en>. + +Acknowledgements + + Thanks to Mike Ackermann for asking the right question, and for + several suggestions on terminology. Brian Trammell provided key + terms and references for the Passive category, and suggested ways to + expand the Hybrid description and types. Phil Eardley suggested some + hybrid scenarios for categorization as part of his review. Tiziano + Ionta reviewed the document and suggested the classification for the + "coloring" Method of Measurement. Nalini Elkins identified several + areas for clarification following her review. Bill Jouris, Stenio + Fernandes, and Spencer Dawkins suggested several editorial + improvements. Tal Mizrahi, Joachim Fabini, Greg Mirsky, and Mike + Ackermann raised many key considerations in their Working Group Last + Call (WGLC) reviews, based on their broad measurement experience. + +Author's Address + + Al Morton + AT&T Labs + 200 Laurel Avenue South + Middletown, NJ + United States + + Email: acmorton@att.com + + + + + + +Morton Informational [Page 14] + |