draft-ietf-ippm-active-passive-06.txt		rfc7799.txt
	Network Working Group A. Morton		Internet Engineering Task Force (IETF) A. Morton
	Internet-Draft AT&T Labs		Request for Comments: 7799 AT&T Labs
	Intended status: Informational January 21, 2016		Category: Informational May 2016
	Expires: July 24, 2016		ISSN: 2070-1721
	Active and Passive Metrics and Methods (and everything in-between, or		Active and Passive Metrics and Methods
	Hybrid)		(with Hybrid Types In-Between)
	draft-ietf-ippm-active-passive-06
	Abstract		Abstract
	This memo provides clear definitions for Active and Passive		This memo provides clear definitions for Active and Passive
	performance assessment. The construction of Metrics and Methods can		performance assessment. The construction of Metrics and Methods can
	be described as Active or Passive. Some methods may use a subset of		be described as either "Active" or "Passive". Some methods may use a
	both active and passive attributes, and we refer to these as Hybrid		subset of both Active and Passive attributes, and we refer to these
	Methods. This memo also describes multiple dimensions to help		as "Hybrid Methods". This memo also describes multiple dimensions to
	evaluate new methods as they emerge.		help evaluate new methods as they emerge.
	Status of This Memo		Status of This Memo
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	Copyright Notice		Copyright Notice
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	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction ....................................................2
	1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3		1.1. Requirements Language ......................................3
	2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 3		2. Purpose and Scope ...............................................3
	3. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 3		3. Terms and Definitions ...........................................3
	3.1. Performance Metric . . . . . . . . . . . . . . . . . . . 4		3.1. Performance Metric .........................................3
	3.2. Method of Measurement . . . . . . . . . . . . . . . . . . 4		3.2. Method of Measurement ......................................4
	3.3. Observation Point . . . . . . . . . . . . . . . . . . . . 4		3.3. Observation Point ..........................................4
	3.4. Active Methods . . . . . . . . . . . . . . . . . . . . . 4		3.4. Active Methods .............................................4
	3.5. Active Metric . . . . . . . . . . . . . . . . . . . . . . 5		3.5. Active Metric ..............................................5
	3.6. Passive Methods . . . . . . . . . . . . . . . . . . . . . 5		3.6. Passive Methods ............................................5
	3.7. Passive Metric . . . . . . . . . . . . . . . . . . . . . 6		3.7. Passive Metric .............................................6
	3.8. Hybrid Methods and Metrics . . . . . . . . . . . . . . . 6		3.8. Hybrid Methods and Metrics .................................6
	4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 8		4. Discussion ......................................................8
	4.1. Graphical Representation . . . . . . . . . . . . . . . . 8		4.1. Graphical Representation ...................................8
	4.2. Discussion of PDM . . . . . . . . . . . . . . . . . . . . 10		4.2. Discussion of PDM .........................................10
	4.3. Discussion of "Coloring" Method . . . . . . . . . . . . . 11		4.3. Discussion of "Coloring" Method ...........................11
	4.4. Brief Discussion of OAM Methods . . . . . . . . . . . . . 11		4.4. Brief Discussion of OAM Methods ...........................11
	5. Security considerations . . . . . . . . . . . . . . . . . . . 12		5. Security Considerations ........................................12
	6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12		6. References .....................................................12
	7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12		6.1. Normative References ......................................12
	8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13		6.2. Informative References ....................................13
	8.1. Normative References . . . . . . . . . . . . . . . . . . 13		Acknowledgements ..................................................14
	8.2. Informative References . . . . . . . . . . . . . . . . . 14		Author's Address ..................................................14
	Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 15
	1. Introduction		1. Introduction
	The adjectives "active" and "passive" have been used for many years		The adjectives "Active" and "Passive" have been used for many years
	to distinguish two different classes of Internet performance		to distinguish between two different classes of Internet performance
	assessment. The first Passive and Active Measurement (PAM)		assessment. The first Passive and Active Measurement (PAM)
	Conference was held in 2000, but the earliest proceedings available		Conference was held in 2000, but the earliest proceedings available
	on-line are from the second PAM conference in 2001		online are from the second PAM conference in 2001
	[https://www.ripe.net/ripe/meetings/pam-2001].		<https://www.ripe.net/ripe/meetings/pam-2001>.
	The notions of "active" and "passive" are well-established. In		The notions of "Active" and "Passive" are well-established. In
	general:		general:
	An Active metric or method depends on a dedicated measurement		o An Active Metric or Method depends on a dedicated measurement
	packet stream and observations of the stream.		packet stream and observations of the stream.
	A Passive metric or method depends *solely* on observation of one		o A Passive Metric or Method depends *solely* on observation of one
	or more existing packet streams. The streams only serve		or more existing packet streams. The streams only serve
	measurement when they are observed for that purpose, and are		measurement when they are observed for that purpose, and are
	present whether measurements take place or not.		present whether or not measurements take place.
	As new techniques for assessment emerge it is helpful to have clear		As new techniques for assessment emerge, it is helpful to have clear
	definitions of these notions. This memo provides more detailed		definitions of these notions. This memo provides more-detailed
	definitions, defines a new category for combinations of traditional		definitions, defines a new category for combinations of traditional
	active and passive techniques, and discusses dimensions to evaluate		Active and Passive techniques, and discusses dimensions to evaluate
	new techniques as they emerge.		new techniques as they emerge.
	This memo provides definitions for Active and Passive Metrics and		This memo provides definitions for Active and Passive Metrics and
	Methods based on long usage in the Internet measurement community,		Methods based on long usage in the Internet measurement community,
	and especially the Internet Engineering Task Force. This memo also		and especially the Internet Engineering Task Force (IETF). This memo
	describes the combination of fundamental Active and Passive		also describes the combination of fundamental Active and Passive
	categories, which are called Hybrid Methods and Metrics.		categories that are called Hybrid Methods and Metrics.
	1.1. Requirements Language		1.1. Requirements Language
	The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",		The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
	"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this		"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
	document are to be interpreted as described in RFC 2119 [RFC2119].		document are to be interpreted as described in [RFC2119].
	2. Purpose and Scope		2. Purpose and Scope
	The scope of this memo is to define and describe Active and Passive		The scope of this memo is to define and describe Active and Passive
	versions of metrics and methods which are consistent with the long-		versions of metrics and methods that are consistent with the long-
	time usage of these adjectives in the Internet measurement community		time usage of these adjectives in the Internet measurement community
	and especially the Internet Engineering Task Force. Since the		and especially the IETF. Since the science of measurement is
	science of measurement is expanding, we provide a category for		expanding, we provide a category for combinations of the traditional
	combinations of the traditional extremes, treating Active and Passive		extremes, treating Active and Passive as a continuum and designating
	as a continuum and designating combinations of their attributes as		combinations of their attributes as Hybrid Methods.
	Hybrid methods.
	Further, this memo's purpose includes describing multiple dimensions		Further, this memo's purpose includes describing multiple dimensions
	to evaluate new methods as they emerge.		to evaluate new methods as they emerge.
	3. Terms and Definitions		3. Terms and Definitions
	This section defines the key terms of the memo. Some definitions use		This section defines the key terms of the memo. Some definitions use
	the notion of "stream of interest" which is synonymous with		the notion of "stream of interest", which is synonymous with
	"population of interest" defined in clause 6.1.1 of ITU-T		"population of interest" defined in clause 6.1.1 of ITU-T
	Recommendation Y.1540 [Y.1540]. These definitions will be useful for		Recommendation Y.1540 [Y.1540]. These definitions will be useful for
	work-in-progress, such as [I-D.zheng-ippm-framework-passive] (with		any work in progress, such as [PASSIVE] (with which there is already
	which there is already good consistency).		good consistency).
	3.1. Performance Metric		3.1. Performance Metric
	The standard definition of a quantity, produced in an assessment of		The standard definition of a quantity, produced in an assessment of
	performance and/or reliability of the network, which has an intended		performance and/or reliability of the network, which has an intended
	utility and is carefully specified to convey the exact meaning of a		utility and is carefully specified to convey the exact meaning of a
	measured value. (This definition is consistent with that of		measured value. (This definition is consistent with that of
	Performance Metric in [RFC2330] and [RFC6390]).		Performance Metric in [RFC2330] and [RFC6390]).
	3.2. Method of Measurement		3.2. Method of Measurement
	The procedure or set of operations having the object of determining a		The procedure or set of operations having the object of determining a
	Measured Value or Measurement Result.		Measured Value or Measurement Result.
	3.3. Observation Point		3.3. Observation Point
	See section 2 of [RFC7011] for this definition (a location in the		See Section 2 of [RFC7011] for the definition of Observation Point (a
	network where packets can be observed), and related definitions. The		location in the network where packets can be observed), and related
	comparable term defined in IETF literature on Active measurement is		definitions. The comparable term defined in IETF literature on
	Measurement Point, see section 4.1 of [RFC5835]. Both of these terms		Active measurement is "Measurement Point" (see Section 4.1 of
	have come into use describing similar actions at the identified point		[RFC5835]). Both of these terms have come into use describing
	in the network path.		similar actions at the identified point in the network path.
	3.4. Active Methods		3.4. Active Methods
	Active measurement methods have the following attributes:		Active Methods of Measurement have the following attributes:
	1. Active methods generate packet streams. Commonly, the packet		o Active Methods generate packet streams. Commonly, the packet
	stream of interest is generated as the basis of measurement.		stream of interest is generated as the basis of measurement.
	Sometimes, the adjective "synthetic" is used to categorize Active		Sometimes, the adjective "synthetic" is used to categorize Active
	measurement streams [Y.1731]. Accompanying packet stream(s) may		measurement streams [Y.1731]. An accompanying packet stream or
	be generated to increase overall traffic load, though the loading		streams may be generated to increase overall traffic load, though
	stream(s) may not be measured.		the loading stream(s) may not be measured.
	2. The packets in the stream of interest have fields or field values		o The packets in the stream of interest have fields or field values
	(or are augmented or modified to include fields or field values)		(or are augmented or modified to include fields or field values)
	which are dedicated to measurement. Since measurement usually		that are dedicated to measurement. Since measurement usually
	requires determining the corresponding packets at multiple		requires determining the corresponding packets at multiple
	measurement points, a sequence number is the most common		measurement points, a sequence number is the most common
	information dedicated to measurement, and often combined with a		information dedicated to measurement, and it is often combined
	timestamp.		with a timestamp.
	3. The Source and Destination of the packet stream of interest are		o The Source and Destination of the packet stream of interest are
	usually known a priori.		usually known a priori.
	4. The characteristics of the packet stream of interest are known at		o The characteristics of the packet stream of interest are known at
	the Source at least, and may be communicated to Destination as		the Source (at least), and may be communicated to the Destination
	part of the method. Note that some packet characteristics will		as part of the method. Note that some packet characteristics will
	normally change during packet forwarding. Other changes along		normally change during packet forwarding. Other changes along the
	the path are possible, see [I-D.morton-ippm-2330-stdform-typep].		path are possible, see [STDFORM].
	When adding traffic to the network for measurement, Active Methods		When adding traffic to the network for measurement, Active Methods
	influence the quantities measured to some degree, and those		influence the quantities measured to some degree, and those
	performing tests should take steps to quantify the effect(s) and/or		performing tests should take steps to quantify the effect(s) and/or
	minimize such effects.		minimize such effects.
	3.5. Active Metric		3.5. Active Metric
	An Active Metric incorporates one or more of the aspects of Active		An Active Metric incorporates one or more of the aspects of Active
	Methods in the metric definition.		Methods in the metric definition.
	For example, IETF metrics for IP performance (developed according to		For example, IETF metrics for IP performance (developed according to
	the [RFC2330] framework) include the Source packet stream		the framework described in [RFC2330]) include the Source-packet
	characteristics as metric input parameters, and also specify the		stream characteristics as metric-input parameters, and also specify
	packet characteristics (Type-P) and Source and Destination IP		the packet characteristics (Type-P) and Source and Destination IP
	addresses (with their implications on both stream treatment and		addresses (with their implications on both stream treatment and
	interfaces associated with measurement points).		interfaces associated with measurement points).
	3.6. Passive Methods		3.6. Passive Methods
	Passive measurement methods are		Passive Methods of Measurement are:
	o based solely on observations of undisturbed and unmodified packet		o based solely on observations of an undisturbed and unmodified
	stream of interest (in other words, the method of measurement MUST		packet stream of interest (in other words, the method of
	NOT add, change, or remove packets or fields, or change field		measurement MUST NOT add, change, or remove packets or fields or
	values anywhere along the path).		change field values anywhere along the path).
	o dependent on the existence of one or more packet streams to supply		o dependent on the existence of one or more packet streams to supply
	the stream of interest.		the stream of interest.
	o dependent on the presence of the packet stream of interest at one		o dependent on the presence of the packet stream of interest at one
	or more designated observation points.		or more designated Observation Points.
	Some passive methods simply observe and collect information on all		Some Passive Methods simply observe and collect information on all
	packets that pass Observation Point(s), while others filter the		packets that pass Observation Point(s), while others filter the
	packets as a first step and only collect information on packets that		packets as a first step and only collect information on packets that
	match the filter criteria, and thereby narrow the stream of interest.		match the filter criteria, and thereby narrow the stream of interest.
	It is common that passive methods are conducted at one or more		It is common that Passive Methods are conducted at one or more
	Observation Points. Passive methods to assess Performance Metrics		Observation Points. Passive Methods to assess Performance Metrics
	often require multiple observation points, e.g., to assess latency of		often require multiple Observation Points, e.g., to assess the
	packet transfer across a network path between two Observation Points.		latency of packet transfer across a network path between two
	In this case, the observed packets must include enough information to		Observation Points. In this case, the observed packets must include
	determine the corresponding packets at different Observation Points.		enough information to determine the corresponding packets at
			different Observation Points.
	Communication of the observations (in some form) to a collector is an		Communication of the observations (in some form) to a collector is an
	essential aspect of Passive Methods. In some configurations, the		essential aspect of Passive Methods. In some configurations, the
	traffic load associated with results export to a collector may		traffic load generated when communicating (or exporting) the Passive
	influence the network performance. However, the collection of		Method results to a collector may itself influence the measured
	results is not unique to Passive Methods, and the load from		network's performance. However, the collection of results is not
	management and operations of measurement systems must always be		unique to Passive Methods, and the load from management and
	considered for potential effects on the measured values.		operations of measurement systems must always be considered for
			potential effects on the measured values.
	3.7. Passive Metric		3.7. Passive Metric
	Passive Metrics apply to observations of packet traffic (traffic		Passive Metrics apply to observations of packet traffic (traffic
	flows in [RFC7011]).		flows in [RFC7011]).
	Passive performance metrics are assessed independent of the packets		Passive performance metrics are assessed independently of the packets
	or traffic flows, and solely through observation. Some refer to such		or traffic flows, and solely through observation. Some refer to such
	assessments as "out-of-band".		assessments as "out of band".
	One example of passive performance metrics for IP packet transfer can		One example of Passive Performance Metrics for IP packet transfer can
	be found in ITU-T Recommendation Y.1540 [Y.1540], where the metrics		be found in ITU-T Recommendation Y.1540 [Y.1540], where the metrics
	are defined on the basis of reference events generated as packet pass		are defined on the basis of reference events generated as packets
	reference points. The metrics are agnostic to the distinction		pass reference points. The metrics are agnostic to the distinction
	between active and passive when the necessary packet correspondence		between Active and Passive when the necessary packet correspondence
	can be derived from the observed stream of interest as required.		can be derived from the observed stream of interest as required.
	3.8. Hybrid Methods and Metrics		3.8. Hybrid Methods and Metrics
	Hybrid Methods are Methods of Measurement which use a combination of		Hybrid Methods are Methods of Measurement that use a combination of
	Active Methods and Passive Methods, to assess Active Metrics, Passive		Active Methods and Passive Methods, to assess Active Metrics, Passive
	Metrics, or new metrics derived from the a priori knowledge and		Metrics, or new metrics derived from the a priori knowledge and
	observations of the stream of interest. ITU-T Recommendation Y.1540		observations of the stream of interest. ITU-T Recommendation Y.1540
	[Y.1540] defines metrics that are also applicable to the hybrid		[Y.1540] defines metrics that are also applicable to the hybrid
	categories, since packet correspondence at different observation/		categories, since packet correspondence at different observation/
	reference points could be derived from "fields or field values which		reference points could be derived from "fields or field values which
	are dedicated to measurement", but otherwise the methods are passive.		are dedicated to measurement", but otherwise the methods are Passive.
	There are several types of Hybrid methods, as categorized below.		There are several types of Hybrid Methods, as categorized below.
	With respect to a *single* stream of interest, Hybrid Type I methods		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		fit in the continuum as follows, in terms of what happens at the
	Source (or Observation Point nearby):		Source (or Observation Point nearby):
	o If you generate the stream of interest => Active		o Generation of the stream of interest => Active
	o If you augment or modify the stream of interest, or employ methods		o Augmentation or modification of the stream of interest, or
	that modify the treatment of the stream => Hybrid Type I		employment of methods that modify the treatment of the stream =>
			Hybrid Type I
			o Observation of a stream of interest => Passive
	o If you solely observe a stream of interest => Passive
	As an example, consider the case where the method generates traffic		As an example, consider the case where the method generates traffic
	load stream(s), and observes an existing stream of interest according		load stream(s), and observes an existing stream of interest according
	to the criteria for Passive Methods. Since loading streams are an		to the criteria for Passive Methods. Since loading streams are an
	aspect of Active Methods, the stream of interest is not "solely		aspect of Active Methods, the stream of interest is not "solely
	observed", and the measurements involve a single stream of interest		observed", and the measurements involve a single stream of interest
	whose treatment has been modified both the presence of the load.		whose treatment has been modified by the presence of the load.
	Therefore, this is a Hybrid Type I method.		Therefore, this is a Hybrid Type I method.
	We define Hybrid Type II as follows: Methods that employ two or more		We define Hybrid Type II as follows: Methods that employ two or more
	different streams of interest with some degree of mutual coordination		different streams of interest with some degree of mutual coordination
	(e.g., one or more Active streams and one or more undisturbed and		(e.g., one or more Active streams and one or more undisturbed and
	unmodified packet streams) to collect both Active and Passive Metrics		unmodified packet streams) to collect both Active and Passive Metrics
	and enable enhanced characterization from additional joint analysis.		and enable enhanced characterization from additional joint analysis.
	[I-D.trammell-ippm-hybrid-ps] presents a problem statement for Hybrid		[HYBRID] presents a problem statement for Hybrid Type II Methods and
	Type II methods and metrics. Note that one or more Hybrid Type I		Metrics. Note that one or more Hybrid Type I streams could be
	streams could be substituted for the Active streams or undisturbed		substituted for the Active streams or undisturbed streams in the
	streams in the mutually coordinated set. It is the Type II Methods		mutually coordinated set. It is the Type II Methods where unique
	where unique Hybrid Metrics are anticipated to emerge.		Hybrid Metrics are anticipated to emerge.
	Methods based on a combination of a single (generated) Active stream		Methods based on a combination of a single (generated) Active stream
	and Passive observations applied to the stream of interest at		and Passive observations applied to the stream of interest at
	intermediate observation points are also a type of Hybrid Methods.		intermediate Observation Points are also Hybrid Methods. However,
	However, [RFC5644] already defines these as Spatial Metrics and		[RFC5644] already defines these as Spatial Metrics and Methods. It
	Methods. It is possible to replace the Active stream of [RFC5644]		is possible to replace the Active stream of [RFC5644] with a Hybrid
	with a Hybrid Type I stream and measure Spatial Metrics (but this was		Type I stream and measure Spatial Metrics (but this was unanticipated
	un-anticipated when [RFC5644] was developed).		when [RFC5644] was developed).
	The Table below illustrates the categorization of methods (where		The table below illustrates the categorization of methods (where
	"Synthesis" refers to a combination of Active and Passive Method		"Synthesis" refers to a combination of Active and Passive Method
	attributes).		attributes).
	| Single Stream | Multiple Simultaneous		| Single Stream | Multiple Simultaneous
	| of Interest | Streams of Interest		| of Interest | Streams of Interest
	| | from Different Methods		| | from Different Methods
	====================================================================		====================================================================
	Single Fundamental | Active or Passive |		Single Fundamental | Active or Passive |
	Method | |		Method | |
	Synthesis of | Hybrid Type I |		Synthesis of | Hybrid Type I |
	Fundamental Methods | |		Fundamental Methods | |
	Multiple Methods | Spatial Metrics | Hybrid Type II		Multiple Methods | Spatial Metrics | Hybrid Type II
	| [RFC5644] |		| [RFC5644] |
	There may be circumstances where results measured with Hybrid Methods		There may be circumstances where results measured with Hybrid Methods
	can be considered equivalent to Passive Methods. Referencing the		can be considered equivalent to those measured with Passive Methods.
	notion of a "class C" where packets of different Type-P are treated		This notion references the possibility of a "class C" where packets
	equally in Section 13 of [RFC2330]and the terminology for paths from		of different Type-P are treated equally in network implementation, as
	Section 5 of [RFC2330]:		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		Hybrid Methods of measurement that augment or modify packets of a
	"class C" in a host should produce equivalent results to Passive		"class C" in a host should produce results equivalent to Passive
	Methods of Measurement, when hosts accessing and links transporting		Methods of Measurement when hosts accessing and links transporting
	these packets along the path (other than those performing		these packets along the path (other than those performing
	augmentation/modification) treat packets from both categories of		augmentation/modification) treat packets from both categories of
	methods (with and without the augmentation/modification) as the same		methods (with and without the augmentation/modification) as the
	"class C". The Passive Methods of Measurement represent the Ground		same "class C". The Passive Methods of Measurement represent the
	Truth for comparisons of results between Passive and Hybrid methods,		Ground Truth when comparing results between Passive and Hybrid
	and this comparison should be conducted to confirm the class C		Methods, and this comparison should be conducted to confirm the
	treatment.		"class C" treatment.
	4. Discussion		4. Discussion
	This section illustrates the definitions and presents some examples.		This section illustrates the definitions and presents some examples.
	4.1. Graphical Representation		4.1. Graphical Representation
	If we compare the Active and Passive Methods, there are at least two		If we compare the Active and Passive Methods, there are at least two
	dimensions on which methods can be evaluated. This evaluation space		dimensions on which methods can be evaluated. This evaluation space
	may be useful when a method is a combination of the two alternative		may be useful when a method is a combination of the two alternative
	methods.		methods.
	The two dimensions (initially chosen) are:		The two dimensions (initially chosen) are:
	Y-Axis: "Effect of the measured stream on network conditions." The		Y-Axis: "Effect of the measured stream on network conditions". The
	degree to which the stream of interest biases overall network		degree to which the stream of interest biases overall network
	conditions experienced by that stream and other streams. This is		conditions experienced by that stream and other streams. This is
	a key dimension for Active measurement error analysis. (Comment:		a key dimension for Active measurement error analysis. (Comment:
	There is also the notion of time averages - a measurement stream		There is also the notion of time averages -- a measurement stream
	may have significant effect while it is present, but the stream is		may have significant effect while it is present, but the stream is
	only generated 0.1% of the time. On the other hand, observations		only generated 0.1% of the time. On the other hand, observations
	alone have no effect on network performance. To keep these		alone have no effect on network performance. To keep these
	dimensions simple, we consider the stream effect only when it is		dimensions simple, we consider the stream effect only when it is
	present, but note that reactive networks defined in [RFC7312] may		present, but note that reactive networks defined in [RFC7312] may
	exhibit bias for some time beyond the life of a stream.)		exhibit bias for some time beyond the life of a stream.)
	X-Axis: "a priori Stream Knowledge." The degree to which stream		X-Axis: "a priori Stream Knowledge". The degree to which stream
	characteristics are known a priori. There are methodological		characteristics are known a priori. There are methodological
	advantages of knowing the source stream characteristics, and		advantages of knowing the source stream characteristics, and
	having complete control of the stream characteristics. For		having complete control of the stream characteristics. For
	example, knowing the number of packets in a stream allows more		example, knowing the number of packets in a stream allows more-
	efficient operation of the measurement receiver, and so is an		efficient operation of the measurement receiver, and so is an
	asset for active measurement methods. Passive methods (with no		asset for Active Methods of Measurement. Passive Methods (with no
	sample filter) have few clues available to anticipate what the		sample filter) have few clues available to anticipate what
	protocol first packet observed will use or how many packets will		protocol the first packet observed will use or how many packets
	comprise the flow, but once the standard protocol of a flow is		will comprise the flow; once the standard protocol of a flow is
	known the possibilities narrow (for some compliant flows).		known, the possibilities narrow (for some compliant flows).
	Therefore this is a key dimension for Passive measurement error		Therefore, this is a key dimension for Passive measurement error
	analysis.		analysis.
	There are a few examples we can plot on a two-dimensional space. We		There are a few examples we can plot on a two-dimensional space. We
	can anchor the dimensions with reference point descriptions.		can anchor the dimensions with reference point descriptions.
	Y-Axis:Effect of the measured stream on network conditions		Y-Axis:Effect of the measured stream on network conditions
	^ Max		^ Max
	|* Active using max capacity stream		|* Active using max capacity stream
	|		|
	|		|
	skipping to change at page 9, line 30 ¶		skipping to change at page 9, line 23 ¶
	|		|
	|		|
	|		|
	|* Active using extremely sparse, randomized stream		|* Active using extremely sparse, randomized stream
	| * PDM Passive		| * PDM Passive
	| Min *		| Min *
	+----------------------------------------------------------------|		+----------------------------------------------------------------|
	| |		| |
	Stream X-Axis: a priori Stream Knowledge No Stream		Stream X-Axis: a priori Stream Knowledge No Stream
	Characteristics Characteristics		Characteristics Characteristics
	completely Known		Completely Known
	known		Known
	(In the graph above, "PDM" refers to [I-D.ietf-ippm-6man-pdm-option],		(In the graph above, "PDM" refers to [PDMOPTION], an IPv6 Option
	an IPv6 Option Header for Performance and Diagnostic Measurements,		Header for Performance and Diagnostic Measurements, described in
	descrived in section 4.2.)		Section 4.2.)
	We recognize that method categorization could be based on additional		We recognize that method categorization could be based on additional
	dimensions, but this would require a different graphical approach.		dimensions, but this would require a different graphical approach.
	For example, "effect of stream of interest on network conditions"		For example, "effect of stream of interest on network conditions"
	could easily be further qualified into:		could easily be further qualified into:
	1. effect on the performance of the stream of interest itself: for		1. effect on the performance of the stream of interest itself: for
	example, choosing a packet marking or Differentiated Services		example, choosing a packet marking or Differentiated Services
	Code Point (DSCP) resulting in domain treatment as a real-time		Code Point (DSCP) resulting in domain treatment as a real-time
	skipping to change at page 10, line 14 ¶		skipping to change at page 9, line 50 ¶
	2. effect on unmeasured streams that share the path and/or		2. effect on unmeasured streams that share the path and/or
	bottlenecks: for example, an extremely sparse measured stream of		bottlenecks: for example, an extremely sparse measured stream of
	minimal size packets typically has little effect on other flows		minimal size packets typically has little effect on other flows
	(and itself), while a stream designed to characterize path		(and itself), while a stream designed to characterize path
	capacity may affect all other flows passing through the capacity		capacity may affect all other flows passing through the capacity
	bottleneck (including itself).		bottleneck (including itself).
	3. effect on network conditions resulting in network adaptation: for		3. effect on network conditions resulting in network adaptation: for
	example, a network monitoring load and congestion conditions		example, a network monitoring load and congestion conditions
	might change routing, placing some flows to alternate paths to		might change routing, placing some flows on alternate paths to
	mitigate the congestion.		mitigate the congestion.
	We have combined 1 and 2 on the Y-axis, as examination of examples		We have combined 1 and 2 on the Y-axis, as examination of examples
	indicates strong correlation of effects in this pair, and network		indicates strong correlation of the effects in this pair, and network
	adaptation is not addressed.		adaptation is not addressed.
	It is apparent that different methods of IP network measurement can		It is apparent that different methods of IP network measurement can
	produce different results, even when measuring the same path at the		produce different results, even when measuring the same path at the
	same time. The two dimensions of the graph help to understand how		same time. The two dimensions of the graph help us to understand how
	the results might change with the method chosen. For example, an		the results might change with the method chosen. For example, an
	Active Method to assess throughput adds some amount of traffic to the		Active Method to assess throughput adds some amount of traffic to the
	network which might result in lower throughput for all streams.		network, which might result in lower throughput for all streams.
	However, a Passive Method to assess throughput can also err on the		However, a Passive Method to assess throughput can also err on the
	low side due to unknown limitations of the hosts providing traffic,		low side due to unknown limitations of the hosts providing traffic,
	competition for host resources, limitations of the network interface,		competition for host resources, limitations of the network interface,
	or private sub-networks that are not an intentional part of the path,		or private sub-networks that are not an intentional part of the path,
	etc. And Hybrid Methods could easily suffer from both forms of		etc. Hybrid Methods could easily suffer from both forms of error.
	error. Another example of potential errors stems from the pitfalls		Another example of potential errors stems from the pitfalls of using
	of using an Active stream with known bias, such as a periodic stream		an Active stream with known a bias, such as a periodic stream defined
	defined in [RFC3432]. The strength of modelling periodic streams		in [RFC3432]. The strength of modeling periodic streams (like Voice
	(like VoIP) is a potential weakness when extending the measured		over IP (VoIP)) is a potential weakness when extending the measured
	results to other application whose streams are non-periodic. The		results to other application whose streams are non-periodic. The
	solutions are to model the application streams more exactly with an		solutions are to model the application streams more exactly with an
	Active Method, or accept the risks and potential errors with the		Active Method or to accept the risks and potential errors with the
	Passive Method discussed above.		Passive Method discussed above.
	4.2. Discussion of PDM		4.2. Discussion of PDM
	In [I-D.ietf-ippm-6man-pdm-option], an IPv6 Option Header for		In [PDMOPTION], an IPv6 Option Header for Performance and Diagnostic
	Performance and Diagnostic Measurements (PDM) is described which		Measurements (PDM) is described which, when added to the stream of
	(when added to the stream of interest at strategic interfaces)		interest at strategic interfaces, supports performance measurements.
	supports performance measurements. This method processes a user		This method processes a user traffic stream and adds "fields which
	traffic stream and adds "fields which are dedicated to measurement"		are dedicated to measurement" (the measurement intent is made clear
	(the measurement intent is made clear in the title of this option).		in the title of this option). Thus:
	Thus:
	o The method intends to have a small effect on the measured stream		o The method intends to have a minor effect on the measured stream
	and other streams in the network. There are conditions where this		and other streams in the network. There are conditions where this
	intent may not be realized.		intent may not be realized.
	o The measured stream has unknown characteristics until it is		o The measured stream has unknown characteristics until it is
	processed to add the PDM Option header. Note that if the packet		processed to add the PDM Option header. Note that if the packet
	MTU is exceeded after adding the header, the intent to have small		MTU is exceeded after adding the header, the intent to have a
	effect will not be realized.		minor effect will not be realized.
	We conclude that this is a Hybrid Type I method, having at least one		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		characteristic of both Active and Passive Methods for a single stream
	of interest.		of interest.
	4.3. Discussion of "Coloring" Method		4.3. Discussion of "Coloring" Method
	Draft [I-D.tempia-opsawg-p3m], proposed to color packets by re-		[OPSAWG], proposed to color packets by re-writing a field of the
	writing a field of the stream at strategic interfaces to support		stream at strategic interfaces to support performance measurements
	performance measurements (noting that this is a difficult operation		(noting that this is a difficult operation at an intermediate point
	at an intermediate point on an encrypted Virtual Private Network).		on an encrypted Virtual Private Network). This method processes a
	This method processes a user traffic stream and inserts "fields or		user traffic stream and inserts "fields or values which are dedicated
	values which are dedicated to measurement". Thus:		to measurement". Thus:
	o The method intends to have a small effect on the measured stream		o The method intends to have a minor effect on the measured stream
	and other streams in the network (smaller than PDM above). There		and other streams in the network (less than PDM above). There are
	are conditions where this intent may not be realized.		conditions where this intent may not be realized.
	o The measured stream has unknown characteristics until it is		o The measured stream has unknown characteristics until it is
	processed to add the coloring in the header, and the stream could		processed to add the coloring in the header, and the stream could
	be measured and time-stamped during that process.		be measured and time-stamped during that process.
	We note that [I-D.chen-ippm-coloring-based-ipfpm-framework] proposes		We note that [COLORING] proposes a method similar to [OPSAWG], as
	a method similar to [I-D.tempia-opsawg-p3m], as ippm-list discussion		discussion on the IPPM mailing list revealed.
	revealed.
	We conclude that this is a Hybrid Type I method, having at least one		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		characteristic of both Active and Passive Methods for a single stream
	of interest.		of interest.
	4.4. Brief Discussion of OAM Methods		4.4. Brief Discussion of OAM Methods
	Many Operations, Administration, and Management (OAM) methods exist		Many Operations, Administration, and Management (OAM) methods exist
	beyond the IP-layer. For example, [Y.1731] defines several different		beyond the IP layer. For example, [Y.1731] defines several different
	measurement methods which we would classify as follows:		measurement methods that we would classify as follows:
	o Loss Measurement (LM) occasionally injects frames with a count of		o Loss Measurement (LM) occasionally injects frames with a count of
	previous frames since the last LM message. We conclude LM is		previous frames since the last LM message. We conclude LM is
	Hybrid Type I because		Hybrid Type I, because this method processes a user traffic stream
	A. This method processes a user traffic stream,		and augments the stream of interest with frames having "fields
			which are dedicated to measurement".
	B. and augments the stream of interest with frames having "fields
	which are dedicated to measurement".
	o Synthetic Loss Measurement (SLM) and Delay Measurement (DM)		o Synthetic Loss Measurement (SLM) and Delay Measurement (DM)
	methods both inject dedicated measurement frames, so the "stream		methods both inject dedicated measurement frames, so the "stream
	of interest is generated as the basis of measurement". We		of interest is generated as the basis of measurement". We
	conclude that SLM and DM methods are Active Methods.		conclude that SLM and DM methods are Active Methods.
	We also recognize the existence of alternate terminology used in OAM		We also recognize the existence of alternate terminology used in OAM
	at layers other than IP. Readers are encouraged to consult [RFC6374]		at layers other than IP. Readers are encouraged to consult [RFC6374]
	for MPLS Loss and Delay measurement terminology, for example.		for MPLS Loss and Delay measurement terminology, for example.
	5. Security considerations		5. Security Considerations
	When considering security and privacy of those involved in		When considering the security and privacy of those involved in
	measurement or those whose traffic is measured, there is sensitive		measurement or those whose traffic is measured, there is sensitive
	information communicated and observed at observation and measurement		information communicated and observed at observation and measurement
	points described above, and protocol issues to consider. We refer		points described above, and protocol issues to consider. We refer
	the reader to the security and privacy considerations described in		the reader to the security and privacy considerations described in
	the Large Scale Measurement of Broadband Performance (LMAP) Framework		the Large-Scale Measurement of Broadband Performance (LMAP) Framework
	[RFC7594], which covers active and passive measurement techniques and		[RFC7594], which covers Active and Passive measurement techniques and
	supporting material on measurement context.		supporting material on measurement context.
	6. IANA Considerations		6. References
	This memo makes no requests for IANA consideration.
	7. 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 draft 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 WGLC reviews, based
	on their broad measurement experience.
	8. References		6.1. Normative References
	8.1. 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,		[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
	"Framework for IP Performance Metrics", RFC 2330,		"Framework for IP Performance Metrics", RFC 2330,
	DOI 10.17487/RFC2330, May 1998,		DOI 10.17487/RFC2330, May 1998,
	<http://www.rfc-editor.org/info/rfc2330>.		<http://www.rfc-editor.org/info/rfc2330>.
	[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>.
	[RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network		[RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network
	performance measurement with periodic streams", RFC 3432,		performance measurement with periodic streams", RFC 3432,
	DOI 10.17487/RFC3432, November 2002,		DOI 10.17487/RFC3432, November 2002,
	<http://www.rfc-editor.org/info/rfc3432>.		<http://www.rfc-editor.org/info/rfc3432>.
	[RFC5644] Stephan, E., Liang, L., and A. Morton, "IP Performance		[RFC5644] Stephan, E., Liang, L., and A. Morton, "IP Performance
	Metrics (IPPM): Spatial and Multicast", RFC 5644,		Metrics (IPPM): Spatial and Multicast", RFC 5644,
	DOI 10.17487/RFC5644, October 2009,		DOI 10.17487/RFC5644, October 2009,
	<http://www.rfc-editor.org/info/rfc5644>.		<http://www.rfc-editor.org/info/rfc5644>.
	skipping to change at page 14, line 11 ¶		skipping to change at page 13, line 22 ¶
	Framework for IP Performance Metrics (IPPM)", RFC 7312,		Framework for IP Performance Metrics (IPPM)", RFC 7312,
	DOI 10.17487/RFC7312, August 2014,		DOI 10.17487/RFC7312, August 2014,
	<http://www.rfc-editor.org/info/rfc7312>.		<http://www.rfc-editor.org/info/rfc7312>.
	[RFC7594] Eardley, P., Morton, A., Bagnulo, M., Burbridge, T.,		[RFC7594] Eardley, P., Morton, A., Bagnulo, M., Burbridge, T.,
	Aitken, P., and A. Akhter, "A Framework for Large-Scale		Aitken, P., and A. Akhter, "A Framework for Large-Scale
	Measurement of Broadband Performance (LMAP)", RFC 7594,		Measurement of Broadband Performance (LMAP)", RFC 7594,
	DOI 10.17487/RFC7594, September 2015,		DOI 10.17487/RFC7594, September 2015,
	<http://www.rfc-editor.org/info/rfc7594>.		<http://www.rfc-editor.org/info/rfc7594>.
	8.2. Informative References		6.2. Informative References
	[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay		[COLORING]
	Measurement for MPLS Networks", RFC 6374,		Chen, M., Ed., Zheng, L., Ed., Mirsky, G., Ed., Fioccola,
	DOI 10.17487/RFC6374, September 2011,		G., Ed., and T. Mizrahi, Ed., "IP Flow Performance
	<http://www.rfc-editor.org/info/rfc6374>.		Measurement Framework", Work in Progress, draft-chen-ippm-
			coloring-based-ipfpm-framework-06, March 2016.
	[I-D.morton-ippm-2330-stdform-typep]		[HYBRID] Trammell, B., Zheng, L., Berenguer, S., and M. Bagnulo,
	Morton, A., Fabini, J., Elkins, N., mackermann@bcbsm.com,		"Hybrid Measurement using IPPM Metrics", Work in Progress,
	m., and V. Hegde, "IP Options and IPv6 Updates for IPPM's		draft-trammell-ippm-hybrid-ps-01, February 2014.
	Active Metric Framework: Packets of Type-P and Standard-
	Formed Packets", draft-morton-ippm-2330-stdform-typep-02
	(work in progress), December 2015.
	[I-D.ietf-ippm-6man-pdm-option]		[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		Elkins, N. and M. Ackermann, "IPv6 Performance and
	Diagnostic Metrics (PDM) Destination Option", draft-ietf-		Diagnostic Metrics (PDM) Destination Option", Work in
	ippm-6man-pdm-option-01 (work in progress), October 2015.		Progress, draft-ietf-ippm-6man-pdm-option-02, April 2016.
	[I-D.tempia-opsawg-p3m]		[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
	Capello, A., Cociglio, M., Castaldelli, L., and A. Bonda,		Measurement for MPLS Networks", RFC 6374,
	"A packet based method for passive performance		DOI 10.17487/RFC6374, September 2011,
	monitoring", draft-tempia-opsawg-p3m-04 (work in		<http://www.rfc-editor.org/info/rfc6374>.
	progress), February 2014.
	[I-D.chen-ippm-coloring-based-ipfpm-framework]		[STDFORM] Morton, A., Fabini, J., Elkins, N., Ackermann, M., and V.
	Chen, M., Zheng, L., Mirsky, G., and G. Fioccola, "IP Flow		Hegde, "Updates for IPPM's Active Metric Framework:
	Performance Measurement Framework", draft-chen-ippm-		Packets of Type-P and Standard-Formed Packets", Work in
	coloring-based-ipfpm-framework-04 (work in progress), July		Progress, draft-morton-ippm-2330-stdform-typep-02,
	2015.		December 2015.
	[I-D.zheng-ippm-framework-passive]		[Y.1540] ITU-T, "Internet protocol data communication service - IP
	Zheng, L., Elkins, N., Lingli, D., Ackermann, M., and G.		packet transfer and availability performance parameters",
	Mirsky, "Framework for IP Passive Performance		March 2011,
	Measurements", draft-zheng-ippm-framework-passive-03 (work		<https://www.itu.int/rec/T-REC-Y.1540-201103-I/en>.
	in progress), February 2015.
	[I-D.trammell-ippm-hybrid-ps]		[Y.1731] ITU-T, "Operation, administration and management (OAM)
	Trammell, B., Zheng, L., Berenguer, S., and M. Bagnulo,		functions and mechanisms for Ethernet-based networks",
	"Hybrid Measurement using IPPM Metrics", draft-trammell-		August 2015,
	ippm-hybrid-ps-01 (work in progress), February 2014.		<https://www.itu.int/rec/T-REC-G.8013-201508-I/en>.
	[Y.1540] ITU-T Recommendation Y.1540, , "Internet protocol data		Acknowledgements
	communication service - IP packet transfer and
	availability performance parameters", March 2011.
	[Y.1731] ITU-T Recommendation Y.1731, , "Operation, administration		Thanks to Mike Ackermann for asking the right question, and for
	and management (OAM) functions and mechanisms for		several suggestions on terminology. Brian Trammell provided key
	Ethernet-based networks", October 2015.		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		Author's Address
	Al Morton		Al Morton
	AT&T Labs		AT&T Labs
	200 Laurel Avenue South		200 Laurel Avenue South
	Middletown, NJ		Middletown, NJ
	USA		United States
	Email: acmorton@att.com		Email: acmorton@att.com
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