draft-mhmcsfh-ippm-pam-01.txt		draft-mhmcsfh-ippm-pam-02.txt
	Network Working Group G. Mirsky		Network Working Group G. Mirsky
	Internet-Draft J. Halpern		Internet-Draft J. Halpern
	Intended status: Standards Track Ericsson		Intended status: Standards Track Ericsson
	Expires: 20 December 2022 X. Min		Expires: 17 February 2023 X. Min
	ZTE Corp.		ZTE Corp.
	A. Clemm		A. Clemm
	J. Strassner		J. Strassner
	Futurewei		Futurewei
	J. Francois		J. Francois
	Inria		Inria
	18 June 2022		16 August 2022
	Precision Availability Metrics for SLO-Governed End-to-End Services		Precision Availability Metrics for SLO-Governed End-to-End Services
	draft-mhmcsfh-ippm-pam-01		draft-mhmcsfh-ippm-pam-02
	Abstract		Abstract
	This document defines a set of metrics for networking services with		This document defines a set of metrics for networking services with
	performance requirements expressed as Service Level Objectives (SLO).		performance requirements expressed as Service Level Objectives (SLO).
	These metrics, referred to as Precision Availability Metrics (PAM),		These metrics, referred to as Precision Availability Metrics (PAM),
	can be used to assess the service levels that are being delivered.		are useful for defining and monitoring of SLOs. Specifically, PAM
	Specifically, PAM can be used to assess whether a service is provided		can be used by providers and/or users of the Network Slice service to
	in compliance with its specified quality, i.e., in accordance with		assess whether the service is provided in compliance with its
	its defined SLOs.		specified quality, i.e., in accordance with its defined SLOs.
	Status of This Memo		Status of This Memo
	This Internet-Draft is submitted in full conformance with the		This Internet-Draft is submitted in full conformance with the
	provisions of BCP 78 and BCP 79.		provisions of BCP 78 and BCP 79.
	Internet-Drafts are working documents of the Internet Engineering		Internet-Drafts are working documents of the Internet Engineering
	Task Force (IETF). Note that other groups may also distribute		Task Force (IETF). Note that other groups may also distribute
	working documents as Internet-Drafts. The list of current Internet-		working documents as Internet-Drafts. The list of current Internet-
	Drafts is at https://datatracker.ietf.org/drafts/current/.		Drafts is at https://datatracker.ietf.org/drafts/current/.
	Internet-Drafts are draft documents valid for a maximum of six months		Internet-Drafts are draft documents valid for a maximum of six months
	and may be updated, replaced, or obsoleted by other documents at any		and may be updated, replaced, or obsoleted by other documents at any
	time. It is inappropriate to use Internet-Drafts as reference		time. It is inappropriate to use Internet-Drafts as reference
	material or to cite them other than as "work in progress."		material or to cite them other than as "work in progress."
	This Internet-Draft will expire on 20 December 2022.		This Internet-Draft will expire on 17 February 2023.
	Copyright Notice		Copyright Notice
	Copyright (c) 2022 IETF Trust and the persons identified as the		Copyright (c) 2022 IETF Trust and the persons identified as the
	document authors. All rights reserved.		document authors. All rights reserved.
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	provided without warranty as described in the Revised BSD License.		provided without warranty as described in the Revised BSD License.
	Table of Contents		Table of Contents
	1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2		1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
	2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4		2. Conventions and Terminology . . . . . . . . . . . . . . . . . 4
	2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4		2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
	2.2. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 4		2.2. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . 4
	3. Performance Availability Metrics . . . . . . . . . . . . . . 5		3. Precision Availability Metrics . . . . . . . . . . . . . . . 5
	3.1. Introducing Violated Intervals . . . . . . . . . . . . . 5		3.1. Introducing Violated Intervals . . . . . . . . . . . . . 5
	3.2. Derived Precision Availability Metrics . . . . . . . . . 6		3.2. Derived Precision Availability Metrics . . . . . . . . . 6
	3.3. Service Availability in PAMs . . . . . . . . . . . . . . 7		3.3. Service Availability in PAMs . . . . . . . . . . . . . . 7
	4. Statistical SLO . . . . . . . . . . . . . . . . . . . . . . . 7		4. Statistical SLO . . . . . . . . . . . . . . . . . . . . . . . 8
	5. Other PAM Benefits . . . . . . . . . . . . . . . . . . . . . 8		5. Other PAM Benefits . . . . . . . . . . . . . . . . . . . . . 9
	6. Discussion Items . . . . . . . . . . . . . . . . . . . . . . 9		6. Discussion Items . . . . . . . . . . . . . . . . . . . . . . 9
	7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9		7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
	8. Security Considerations . . . . . . . . . . . . . . . . . . . 9		8. Security Considerations . . . . . . . . . . . . . . . . . . . 10
	9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 10		9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 11
	10. References . . . . . . . . . . . . . . . . . . . . . . . . . 10		10. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
	10.1. Informative References . . . . . . . . . . . . . . . . . 10		10.1. Informative References . . . . . . . . . . . . . . . . . 11
	Contributors' Addresses . . . . . . . . . . . . . . . . . . . . . 11		Contributors' Addresses . . . . . . . . . . . . . . . . . . . . . 11
	Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11		Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
	1. Introduction		1. Introduction
	Network operators and network users often need to assess the quality		Network operators and network users often need to assess the quality
	with which network services are being provided and delivered. In		with which network services are being provided and delivered. In
	particular in cases where service level guarantees are given and		particular in cases where service level guarantees are given and
	service level objectives (SLOs) are defined, it is essential to		service level objectives (SLOs) are defined, it is essential to
	provide a measure of the degree with which actual service levels that		provide a measure of the degree with which actual service levels that
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	the SLOs that are in effect. PAM can be used to assess whether a		the SLOs that are in effect. PAM can be used to assess whether a
	service is provided in compliance with its specified quality, i.e.,		service is provided in compliance with its specified quality, i.e.,
	in accordance with its defined SLOs. This information can be used in		in accordance with its defined SLOs. This information can be used in
	multiple ways, for example, to optimize service delivery, take timely		multiple ways, for example, to optimize service delivery, take timely
	counteractions in the event of service degradation, or account for		counteractions in the event of service degradation, or account for
	the quality of services being delivered.		the quality of services being delivered.
	Availability is discussed in Section 3.4 of [RFC7297]. In this		Availability is discussed in Section 3.4 of [RFC7297]. In this
	document, the term "availability" reflects that a service which is		document, the term "availability" reflects that a service that is
	characterized by its SLOs is considered unavailable whenever those		characterized by its SLOs is considered unavailable whenever those
	SLOs are violated, even if basic connectivity is still working.		SLOs are violated, even if basic connectivity is still working.
	"Precision" refers to the fact that services whose end-to-end service		"Precision" refers to the fact that services whose end-to-end service
	levels are governed by SLOs, and which must therefore be precisely		levels are governed by SLOs, and which must therefore be precisely
	delivered according to the associated quality and performance		delivered according to the associated quality and performance
	requirements. It should be noted that "precision" refers to what is		requirements. It should be noted that precision refers to what is
	being assessed, not to the mechanism used to measure it; in other		being assessed, not the mechanism used to measure it; in other words,
	words, it does not refer to the precision of the mechanism with which		it does not refer to the precision of the mechanism with which actual
	actual service levels are measured. The specification and		service levels are measured. Furthermore, the precision, with
			respect to the delivery of an SLO, only applies when the metric value
			approaches the specified threshold levels in the SLO. The
	implementation of methods that provide for accurate measurements is a		specification and implementation of methods that provide for accurate
	separate topic independent of the definition of the metrics in which		measurements is a separate topic independent of the definition of the
	the results of such measurements would be expressed.		metrics in which the results of such measurements would be expressed.
			Service Level Expectations, as defined in Section 4.1 of
			[I-D.ietf-teas-ietf-network-slices], are outside the scope of this
			document.
	[Ed.note: It should be noted that at this point, the set of metrics		[Ed.note: It should be noted that at this point, the set of metrics
	proposed here is intended as a "starter set" that is intended to		proposed here is intended as a "starter set" that is intended to
	spark further discussion. Other metrics are certainly conceivable;		spark further discussion. Other metrics are certainly conceivable;
	we expect that the list of metrics will evolve as part of the Working		we expect that the list of metrics will evolve as part of the Working
	Group discussions.]		Group discussions.]
	2. Conventions and Terminology		2. Conventions and Terminology
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	2.2. Acronyms		2.2. Acronyms
	[Ed.Note: needs updating.]		[Ed.Note: needs updating.]
	PAM Precision Availability Metric		PAM Precision Availability Metric
	OAM Operations, Administration, and Maintenance		OAM Operations, Administration, and Maintenance
	VI Violated Interval		VI Violated Interval
	VIR Violated Interval Ratio		VIR Violated Interval Ratio
	SVI Severely Violated Interval		SVI Severely Violated Interval
	SVIR Severely Violated Interval Ratio		SVIR Severely Violated Interval Ratio
	VFI Violation-Free Interval		VFI Violation-Free Interval
	3. Performance Availability Metrics		3. Precision Availability Metrics
	3.1. Introducing Violated Intervals		3.1. Introducing Violated Intervals
	When analyzing the availability metrics of a service flow between two		When analyzing the availability metrics of a service flow between two
	nodes, we need to select a time interval as the unit of PAM. In		nodes, we need to select a time interval as the unit of PAM. In
	[ITU.G.826], a time interval of one second is used. That is		[ITU.G.826], a time interval of one second is used. That is
	reasonable, but some services may require different granularity. For		reasonable, but some services may require different granularity. For
	that reason, the time interval in PAM is viewed as a variable		that reason, the time interval in PAM is viewed as a variable
	parameter though constant for a particular measurement session.		parameter though constant for a particular measurement session.
	Further, for the purpose of PAM, each time interval, e.g., second or		Further, for the purpose of PAM, each time interval, e.g., second or
	decamillisecond, is classified either as Violated Interval (VI),		decamillisecond, is classified either as Violated Interval (VI),
	Severely Violated Interval (SVI), or Violation-Free Interval (VFI ).		Severely Violated Interval (SVI), or Violation-Free Interval (VFI ).
	These are defined as follows:		These are defined as follows:
	* VI is a time interval during which at least one of the performance		* VI is a time interval during which at least one of the performance
	parameters degraded compared to its pre-defined optimal level		parameters degraded below its pre-defined optimal level threshold.
	threshold.
	* SVI is a time interval during which at least one the performance		* SVI is a time interval during which at least one the performance
	parameters degraded compared to its pre-defined critical		parameters degraded below its pre-defined critical threshold.
	threshold.
	* Consequently, VFI is a time interval during which all performance		* Consequently, VFI is a time interval during which all performance
	objectives are at or better than their respective pre-defined		objectives are at or better than their respective pre-defined
	optimal levels. In such a case, the service is in compliance with		optimal levels.
	its specification.
	Mechanisms of setting levels of threshold of an SLO are outside the		Mechanisms of setting levels of threshold of an SLO are outside the
	scope for this document.		scope for this document.
	From these defitions, a set of basic metrics can be defined that		From these defitions, a set of basic metrics can be defined that
	count the numbers of time intervals that fall into each category:		count the numbers of time intervals that fall into each category:
	* VI count.		* VI count.
	* SVI count.		* SVI count.
	* VFI count.		* VFI count.
	These count metrics are essential in calculating respective ratios		These count metrics are essential in calculating respective ratios
	that can be used to assess the instability of the service.		(see Section 3.2) that can be used to assess the instability of the
			service.
	3.2. Derived Precision Availability Metrics		3.2. Derived Precision Availability Metrics
	A set of metrics can be created based on PAM introduced in Section 3.		A set of metrics can be created based on PAM introduced in Section 3.
	In this document, these metrics are referred to as derived PAM. Some		In this document, these metrics are referred to as derived PAM. Some
	of these metrics are modeled after Mean Time Between Failure (MTBF)		of these metrics are modeled after Mean Time Between Failure (MTBF)
	metrics - a "failure" in this context referring to a failure to		metrics - a "failure" in this context referring to a failure to
	deliver a packet according to its SLO.		deliver a packet according to its SLO.
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	ms, since last violated second). (This parameter is suitable for		ms, since last violated second). (This parameter is suitable for
	monitoring the current compliance status of the service, e.g., for		monitoring the current compliance status of the service, e.g., for
	trending analysis.)		trending analysis.)
	* Packets since the last violated packet. (This parameter is		* Packets since the last violated packet. (This parameter is
	suitable for the monitoring of the current compliance status of		suitable for the monitoring of the current compliance status of
	the service.)		the service.)
	* Mean time between EIs (e.g., between violated milliseconds,		* Mean time between VIs (e.g., between violated milliseconds,
	violated seconds) is the arithmetic mean of time between		violated seconds) is the arithmetic mean of time between
	consecutive EIs.		consecutive VIs.
	* Mean packets between EIs is the arithmetic mean of the number of		* Mean packets between VIs is the arithmetic mean of the number of
	SLO-compliant packets between consecutive EIs. (Another variation		SLO-compliant packets between consecutive VIs. (Another variation
	of "MTBF" in a service setting.)		of "MTBF" in a service setting.)
	An analogous set of metrics can be produced for SVI:		An analogous set of metrics can be produced for SVI:
	* Time since the last SVI (e.g., since last violated ms, since last		* Time since the last SVI (e.g., since last violated ms, since last
	violated second). (This parameter is suitable for the monitoring		violated second). (This parameter is suitable for the monitoring
	of the current compliance status of the service.)		of the current compliance status of the service.)
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	* Mean time between SVIs (e.g., between severely violated		* Mean time between SVIs (e.g., between severely violated
	milliseconds, severely violated seconds) is the arithmetic mean of		milliseconds, severely violated seconds) is the arithmetic mean of
	time between consecutive SVIs.		time between consecutive SVIs.
	* Mean packets between SVIs is the arithmetic mean of the number of		* Mean packets between SVIs is the arithmetic mean of the number of
	SLO-compliant packets between consecutive SVIs. (Another		SLO-compliant packets between consecutive SVIs. (Another
	variation of "MTBF" in a service setting.)		variation of "MTBF" in a service setting.)
	Determining the condition in which the path is currently with respect		Determining the condition in which the monitored service is currently
	to availability/unavailability is helpful. But because switching		with respect to availability/unavailability is helpful. But because
	between periods requires ten consecutive intervals, shorter		the transition between service availability/unavailability periods is
			based on a pre-defined number of consecutive intervals, e.g., ten,
	conditions may not be adequately reflected. Two additional PAMs can		shorter conditions may not be adequately reflected. Two additional
	be used, and they are defined as follows:		PAMs can be used, and they are defined as follows:
	* violated interval ratio (VIR) is the ratio of VI to the total		* violated interval ratio (VIR) is the ratio of the combined number
	number of time unit intervals in a time of the availability		of VIs and SVIs to the total number of time unit intervals in a
	periods during a fixed measurement interval.		time of the availability periods during a fixed measurement
			interval.
	* severely violated interval ratio (SVIR) - is the ratio of SVIs to		* severely violated interval ratio (SVIR) - is the ratio of SVIs to
	the total number of time unit intervals in a time of the		the total number of time unit intervals in a time of the
	availability periods during a fixed measurement interval.		availability periods during a fixed measurement interval.
	3.3. Service Availability in PAMs		3.3. Service Availability in PAMs
	VI, SVI, and VFI characterize the communication between two nodes		VI, SVI, and VFI characterize the communication between two nodes
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	condition in this document defined to as service availability. The		condition in this document defined to as service availability. The
	latter is defined as service unavailability. Based on the		latter is defined as service unavailability. Based on the
	definitions in Section 3.1, SVI is the one time interval of service		definitions in Section 3.1, SVI is the one time interval of service
	unavailability while VI and VFI present an interval of service		unavailability while VI and VFI present an interval of service
	availability. Since the conditions of the service are are		availability. Since the conditions of the service are are
	continually changing, periods of availability and unavailability need		continually changing, periods of availability and unavailability need
	to be defined with duration larger than one time interval to reduce		to be defined with duration larger than one time interval to reduce
	the number of state changes while correctly reflecting the service		the number of state changes while correctly reflecting the service
			condition.
			It is worth noting that a service might include a set of connectivity
			constructs. An SLO might apply to all the constructs, or some
			constructs are assigned different SLO values or even different sets
			of SLOs. It is worth noting that a composite service might include a
			set of connectivity constructs. An SLO might apply to all the
			constructs, or some constructs are assigned different sets of SLOs.
			For the purpose of PAM, each connectivity construct that composes the
			service can be monitored for its own SLO conformance as a sub-
			service. The composition of PAMs of these sub-services can be viewed
			as the PAM of the composite service. The composition of PAMs of
			these sub-services can be viewed as the PAM of the composite service.
	condition. The method to determine the state of the service in terms		The method to determine the state of the service in terms of PAM is
	of PAM is described below:		described below:
	* If ten consecutive SVIs been detected, then the PAM state of the		* If ten consecutive SVIs been detected, then the PAM state of the
	service is defined as unavailability, and the beginning of that		service is defined as unavailability, and the beginning of that
	period of unavailability state is at the start of the first SVI in		period of unavailability state is at the start of the first SVI in
	the sequence of the consecutive SVIs.		the sequence of the consecutive SVIs.
	* Similarly, for ten consecutive non-SVIs (i.e., either VIs or		* Similarly, for ten consecutive non-SVIs (i.e., either VIs or
	VFIs), the service is defined to be available. The start of that		VFIs), the service is defined to be available. The start of that
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	unavailable, a sequence of seven VFI s is not viewed as an		unavailable, a sequence of seven VFI s is not viewed as an
	availability period.		availability period.
	4. Statistical SLO		4. Statistical SLO
	It should be noted that certain Service Level Agreements (SLA) may be		It should be noted that certain Service Level Agreements (SLA) may be
	statistical, requiring the service levels of packets in a flow to		statistical, requiring the service levels of packets in a flow to
	adhere to specific distributions. For example, an SLA might state		adhere to specific distributions. For example, an SLA might state
	that any given SLO applies only to a certain percentage of packets,		that any given SLO applies to at least a certain percentage of
	allowing for a certain level of, for example, packet loss and/or		packets, allowing for a certain level of, for example, packet loss
	exceeding packet delay threshold to take place. Each such event, in		and/or exceeding packet delay threshold to take place. Each such
	that case, does not necessarily constitute an SLO violation.		event, in that case, does not necessarily constitute an SLO
	However, it is still useful to maintain those statistics, as the		violation. However, it is still useful to maintain those statistics,
	number of out-of-SLO packets still matters when looked at in		as the number of out-of-SLO packets still matters when looked at in
	proportion to the total number of packets.		proportion to the total number of packets.
	Along that vein, an SLA might establish an SLO of, say, end-to-end		Along that vein, an SLA might establish an SLO of, say, end-to-end
	latency to not exceed 20 ms for 99% of packets, to not exceed 25ms		latency to not exceed 20 ms for 99% of packets, to not exceed 25ms
	for 99.999% of packets, and to never exceed 30ms for any packet. In		for 99.999% of packets, and to never exceed 30ms for any packet. In
	that case, any individual packet with latency larger than 20 ms		that case, any individual packet with latency larger than 20 ms
	latency and lower than 30 ms cannot be considered an SLO violation in		latency and lower than 30 ms cannot be considered an SLO violation in
	itself, but compliance with the SLO may need to be assessed after the		itself, but compliance with the SLO may need to be assessed after the
	fact.		fact.
	To support statistical services more directly requires additional		To support statistical SLOs more directly requires additional
	metrics, such as metrics that represent histograms for service level		metrics, such as metrics that represent histograms for service level
	parameters with buckets corresponding to individual service level		parameters with buckets corresponding to individual service level
	objectives. For the example just given, a histogram for a given flow		objectives. For the example just given, a histogram for a given flow
	could be maintained with three buckets: one containing the count of		could be maintained with three buckets: one containing the count of
	packets within 20ms, a second with a count of packets between 20 and		packets within 20ms, a second with a count of packets between 20 and
	25ms (or simply all within 25ms), a third with a count of packets		25ms (or simply all within 25ms), a third with a count of packets
	between 25 and 30ms (or merely all packets within 30ms, and a fourth		between 25 and 30ms (or merely all packets within 30ms, and a fourth
	with a count of anything beyond (or simply a total count). Of		with a count of anything beyond (or simply a total count). Of
	course, the number of buckets and the boundaries between those		course, the number of buckets and the boundaries between those
	buckets should correspond to the needs of the SLA associated with the		buckets should correspond to the needs of the SLA associated with the
	application, i.e., to the specific guarantees and SLOs that were		application, i.e., to the specific guarantees and SLOs that were
	provided. The definition of histogram metrics is for further study.		provided. The definition of histogram metrics is for further study
			(see Section 6).
	5. Other PAM Benefits		5. Other PAM Benefits
	PAM provides a number of benefits with other, more conventional		PAM provides a number of benefits with other, more conventional
	performance metrics. Without PAM, it would be possible to conduct		performance metrics. Without PAM, it would be possible to conduct
	ongoing measurements of service levels and maintain a time-series of		ongoing measurements of service levels and maintain a time-series of
	service level records, then assess compliance with specific SLOs		service level records, then assess compliance with specific SLOs
	after the fact. However, doing so would require the collection of		after the fact. However, doing so would require the collection of
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	scale and in real-time would present significant additional		scale and in real-time would present significant additional
	challenges.		challenges.
	Adding PAM allows for a more compact expression of service level		Adding PAM allows for a more compact expression of service level
	compliance. In that sense, PAM does not simply represent raw data		compliance. In that sense, PAM does not simply represent raw data
	but expresses actionable information. In conjunction with proper		but expresses actionable information. In conjunction with proper
	instrumentation, PAM can thus help avoid expensive postprocessing.		instrumentation, PAM can thus help avoid expensive postprocessing.
	6. Discussion Items		6. Discussion Items
	The following items require further discussion:		The following items require further discussion:
	* Metrics. The foundational metrics defined in this draft refer to		* Metrics. The foundational metrics defined in this draft refer to
	violated intervals. In addition, counts of violations related to		violated intervals. In addition, counts of violations related to
	individual packets may also need to be maintained. Metrics		individual packets may also need to be maintained. Metrics
	referring to violated packets (i.e., packets that on an individual		referring to violated packets (i.e., packets that on an individual
	basis miss a performance objective) may be added in a later		basis miss a performance objective) may be added in a later
	revision of this document.		revision of this document.
	The following is a list of items for which further discussion is		The following is a list of items for which further discussion is
	needed as to whether they should be included in the scope of this		needed as to whether they should be included in the scope of this
	specification:		specification:
	* A YANG data model.		* A YANG data model.
	* A set of IPFIX Information Elements.		* A set of IPFIX Information Elements.
	* Statistical metrics: e.g., histograms/buckets.		* Statistical metrics: e.g., histograms/buckets.
	* Policies regarding the definition of "violated" and "severely		* Policies regarding the definition of "violated" and "severely
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	adequately secured to ensure accurate measurements and prohibit		adequately secured to ensure accurate measurements and prohibit
	tampering with metrics being kept.		tampering with metrics being kept.
	Where metrics are being defined relative to an SLO, the configuration		Where metrics are being defined relative to an SLO, the configuration
	of those SLOs needs to be adequately secured. Likewise, where SLOs		of those SLOs needs to be adequately secured. Likewise, where SLOs
	can be adjusted, the correlation between any metrics instance and a		can be adjusted, the correlation between any metrics instance and a
	particular SLO must be clear. The same service levels that		particular SLO must be clear. The same service levels that
	constitute SLO violations for one flow that should be maintained as		constitute SLO violations for one flow that should be maintained as
	part of the "violated time units" and related metrics, may be		part of the "violated time units" and related metrics, may be
	perfectly compliant for another flow. In cases when it is impossible		perfectly compliant for another flow. In cases when it is impossible
	to tie together SLOs and PAM properly, it will be preferable to		to tie together SLOs and PAM properly, it will be preferable to
	merely maintain statistics about service levels delivered (for		merely maintain statistics about service levels delivered (for
	example, overall histograms of end-to-end latency) without assessing		example, overall histograms of end-to-end latency) without assessing
	which constitutes violations.		which constitutes violations.
	By the same token, where the definition of what constitutes a		By the same token, where the definition of what constitutes a
	"severe" or a "significant" violation depends on policy or context.		"severe" or a "significant" violation depends on policy or context.
	The configuration of such policy or context needs to be specially		The configuration of such policy or context needs to be specially
	secured. Also, the configuration of this policy must be bound to the		secured. Also, the configuration of this policy must be bound to the
	metrics being maintained. This way, it will be clear which policy		metrics being maintained. This way, it will be clear which policy
	was in effect when those metrics were being assessed. An attacker		was in effect when those metrics were being assessed. An attacker
	that can tamper with such policies will render the corresponding		that can tamper with such policies will render the corresponding
	metrics useless (in the best case) or misleading (in the worst case).		metrics useless (in the best case) or misleading (in the worst case).
	9. Acknowledgments		9. Acknowledgments
	TBA		TBA
	10. References		10. References
	10.1. Informative References		10.1. Informative References
	[I-D.ietf-teas-ietf-network-slices]		[I-D.ietf-teas-ietf-network-slices]
	Farrel, A., Drake, J., Rokui, R., Homma, S., Makhijani,		Farrel, A., Drake, J., Rokui, R., Homma, S., Makhijani,
	K., Contreras, L. M., and J. Tantsura, "Framework for IETF		K., Contreras, L. M., and J. Tantsura, "Framework for IETF
	Network Slices", Work in Progress, Internet-Draft, draft-		Network Slices", Work in Progress, Internet-Draft, draft-
	ietf-teas-ietf-network-slices-10, 27 March 2022,		ietf-teas-ietf-network-slices-14, 3 August 2022,
	<https://datatracker.ietf.org/doc/html/draft-ietf-teas-		<https://datatracker.ietf.org/doc/html/draft-ietf-teas-
	ietf-network-slices-10>.		ietf-network-slices-14>.
	[ITU.G.826]		[ITU.G.826]
	ITU-T, "End-to-end error performance parameters and		ITU-T, "End-to-end error performance parameters and
	objectives for international, constant bit-rate digital		objectives for international, constant bit-rate digital
	paths and connections", ITU-T G.826, December 2002.		paths and connections", ITU-T G.826, December 2002.
	[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group		[RFC2863] McCloghrie, K. and F. Kastenholz, "The Interfaces Group
	MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000,		MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000,
	<https://www.rfc-editor.org/info/rfc2863>.		<https://www.rfc-editor.org/info/rfc2863>.
	[RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken,		[RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
	"Specification of the IP Flow Information Export (IPFIX)		"Specification of the IP Flow Information Export (IPFIX)
	Protocol for the Exchange of Flow Information", STD 77,		Protocol for the Exchange of Flow Information", STD 77,
	RFC 7011, DOI 10.17487/RFC7011, September 2013,		RFC 7011, DOI 10.17487/RFC7011, September 2013,
	<https://www.rfc-editor.org/info/rfc7011>.		<https://www.rfc-editor.org/info/rfc7011>.
	[RFC7012] Claise, B., Ed. and B. Trammell, Ed., "Information Model		[RFC7012] Claise, B., Ed. and B. Trammell, Ed., "Information Model
	for IP Flow Information Export (IPFIX)", RFC 7012,		for IP Flow Information Export (IPFIX)", RFC 7012,
	DOI 10.17487/RFC7012, September 2013,		DOI 10.17487/RFC7012, September 2013,
	<https://www.rfc-editor.org/info/rfc7012>.		<https://www.rfc-editor.org/info/rfc7012>.
	[RFC7297] Boucadair, M., Jacquenet, C., and N. Wang, "IP		[RFC7297] Boucadair, M., Jacquenet, C., and N. Wang, "IP
	Connectivity Provisioning Profile (CPP)", RFC 7297,		Connectivity Provisioning Profile (CPP)", RFC 7297,
	DOI 10.17487/RFC7297, July 2014,		DOI 10.17487/RFC7297, July 2014,
	<https://www.rfc-editor.org/info/rfc7297>.		<https://www.rfc-editor.org/info/rfc7297>.
	[RFC8343] Bjorklund, M., "A YANG Data Model for Interface		[RFC8343] Bjorklund, M., "A YANG Data Model for Interface
	Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,		Management", RFC 8343, DOI 10.17487/RFC8343, March 2018,
	<https://www.rfc-editor.org/info/rfc8343>.		<https://www.rfc-editor.org/info/rfc8343>.
	Contributors' Addresses		Contributors' Addresses
	Liuyan Han		Liuyan Han
	China Mobile		China Mobile
	32 XuanWuMenXi Street		32 XuanWuMenXi Street
	Beijing		Beijing
	100053		100053
	China		China
	Email: hanliuyan@chinamobile.com		Email: hanliuyan@chinamobile.com
	Skipping		Skipping
	Email: joel.halpern@ericsson.com		Email: joel.halpern@ericsson.com
	Xiao Min		Xiao Min
	ZTE Corp.		ZTE Corp.
	Email: xiao.min2@zte.com.cn		Email: xiao.min2@zte.com.cn
	Alexander Clemm		Alexander Clemm
	Futurewei		Futurewei
	2330 Central Expressway		2330 Central Expressway
	Santa Clara, CA 95050		Santa Clara, CA 95050
	United States of America		United States of America
	Email: ludwig@clemm.org		Email: ludwig@clemm.org
	John Strassner		John Strassner
	Futurewei		Futurewei
	2330 Central Expressway		2330 Central Expressway
	Santa Clara, CA 95050		Santa Clara, CA 95050
	United States of America		United States of America
	Email: strazpdj@gmail.com		Email: strazpdj@gmail.com
	Jerome Francois		Jerome Francois
	Inria		Inria
	615 Rue du Jardin Botanique		615 Rue du Jardin Botanique
	54600 Villers-les-Nancy		54600 Villers-les-Nancy
	France		France
	Email: jerome.francois@inria.fr		Email: jerome.francois@inria.fr
	Skipping		Skipping