One document matched: draft-ietf-pmol-metrics-framework-12.xml
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<front>
<title abbrev="Guidelines Perf. Metric Devel.">Guidelines for Considering New Performance Metric Development</title>
<author fullname="Alan Clark" initials="A." surname="Clark">
<organization>Telchemy Incorporated</organization>
<address>
<postal>
<street>2905 Premiere Parkway, Suite 280</street>
<city>Duluth</city>
<region>Georgia</region>
<code>30097</code>
<country>USA</country>
</postal>
<phone></phone>
<facsimile></facsimile>
<email>alan.d.clark@telchemy.com</email>
<uri></uri>
</address>
</author>
<author fullname="Benoit Claise" initials="B." surname="Claise">
<organization>Cisco Systems, Inc.</organization>
<address>
<postal>
<street>De Kleetlaan 6a b1</street>
<city>Diegem</city>
<code>1831</code>
<country>Belgium</country>
</postal>
<phone>+32 2 704 5622</phone>
<facsimile></facsimile>
<email>bclaise@cisco.com</email>
<uri></uri>
</address>
</author>
<date day="28" month="July" year="2011" />
<abstract>
<t>
This document describes a framework and a process for developing
Performance Metrics of protocols and applications transported over
IETF-specified protocols, and that can be used to
characterize traffic on live networks and services.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>Many networking technologies, applications, or services, are distributed
in nature, and their performance may be impacted by IP impairments, server
capacity, congestion and other factors. It is important to measure the
performance of applications and services to ensure that quality objectives
are being met and to support problem diagnosis. Standardized metrics help
to ensure that performance measurement is implemented consistently and facilitate
interpretation and comparison.</t>
<t>There are at least three phases in the development of performance
standards. They are:</t>
<t><list style="numbers">
<t>Definition of a Performance Metric and its units of measure</t>
<t>Specification of a method of measurement</t>
<t>Specification of the reporting format</t>
</list>
During the development of metrics, it is often useful to define
performance objectives and expected value ranges. However, this is not
defined as part of the metric specification. </t>
<t>
The intended audience for this document includes, but is not
limited to, IETF participants who write Performance Metrics documents
in the IETF, reviewers of such documents, and members of the Performance
Metrics Directorate.
</t>
<section title="Background and Motivation">
<t>
Previous IETF work related to reporting of application Performance Metrics
includes the "Real-time Application Quality-of-Service Monitoring (RAQMON) Framework"
<xref target="RFC4710"></xref>, which extends the remote network monitoring
(RMON) family of specifications to allow real-time quality-of-service (QoS)
monitoring of various applications that run on devices such as IP phones,
pagers, Instant Messaging clients, mobile phones, and various other
handheld computing devices. Furthermore, the "RTP Control Protocol Extended
Reports (RTCP XR)" <xref target="RFC3611"></xref> and the "SIP RTCP Summary
Report Protocol" <xref target="RFC6035"></xref> are
protocols that support the real-time reporting of Voice over IP and other
applications running on devices such as IP phones and mobile handsets.
</t>
<t>
The IETF is also actively involved in the development of reliable
transport protocols, such as <xref target="RFC0793">TCP</xref> or
<xref target="RFC4960">SCTP</xref>, which would affect the relationship
between IP performance and application performance.
</t>
<t>
Thus there is a gap in the currently chartered coverage of IETF
Working Groups (WG): development of Performance Metrics for protocols above
and below the IP-layer that can be used to characterize performance on live
networks.
</t>
<t>
Similarly to the "Guidelines for Considering Operations and Management of
New Protocols and Protocol Extensions" <xref target="RFC5706"></xref>, which
is the reference document for the IETF Operations Directorate, this document
should be consulted as part of the new Performance Metric review by the
members of the Performance Metrics Directorate.
</t>
</section>
<section title="Organization of this document">
<t>This document is divided in two major sections beyond the "Purpose and
Scope" section. The first is a definition and description of a
Performance Metric and its key aspects. The second defines a process
to develop these metrics that is applicable to the IETF
environment.</t>
</section>
</section>
<section title="Terminology">
<note title="Requirements Language">
<t>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 <xref
target="RFC2119">RFC 2119</xref>.</t>
</note>
<section title="Performance Metrics Directorate">
<t>
The Performance Metrics Directorate is a directorate provides guidance
for Performance Metrics development in the IETF.
</t>
<t>
The Performance Metrics Directorate should be composed of experts in the performance community,
potentially selected from the IPPM, BMWG, and PMOL WGs.
</t>
</section>
<section title="Quality of Service">
<t>
Quality of Service (QoS) is defined similarly to the ITU
"QoS experienced/perceived by customer/user (QoE)"
<xref target="E.800">E.800</xref>, i.e.:
"Totality of characteristics of a telecommunications service that bear
on its ability to satisfy stated and implied needs of the user of the service."
</t>
</section>
<section title="Quality of Experience">
<t>
Quality of Experience (QoE) is defined in a similar way to the ITU
"QoS experienced/perceived by customer/user (QoE)"
<xref target="E.800">E.800</xref>, i.e.:
"a statement expressing the level of quality that customers/users believe
they have experienced."
</t>
<t>
NOTE 1 - The level of QoS experienced and/or perceived by the customer/user
may be expressed by an opinion rating.
</t>
<t>
NOTE 2 - QoE has two main components: quantitative and
qualitative. The quantitative component can be influenced by the
complete end-to-end system effects (including user devices and
network infrastructure).
</t>
<t>
NOTE 3 - The qualitative component can be influenced by user expectations,
ambient conditions, psychological factors, application context, etc.
</t>
<t>
NOTE 4 - QoE may also be considered as QoS delivered, received, and
interpreted by a user with the pertinent qualitative factors influencing
his/her perception of the service.
</t>
</section>
<section title="Performance Metric">
<t>
A quantitative measure of performance, specific to an IETF-specified
protocol or specific to an application transported over an IETF-specified
protocol. Examples of Performance Metrics are: the FTP response time for a
complete file download, the DNS response time to resolve the IP address, a
database logging time, etc.
</t>
</section>
</section>
<section title="Purpose and Scope">
<t>The purpose of this document is to define a framework and a process
for developing Performance Metrics for protocols above and below the IP-layer
(such as IP-based applications that operate over reliable or datagram transport
protocols), that can be used to characterize traffic on live networks and
services. As such, this document does not define any Performance Metrics.</t>
<t>The scope of this document covers guidelines for the Performance Metrics Directorate
members for considering new Performance Metrics, and suggests how the Performance Metrics
Directorate will interact with the rest of the IETF. However this document is not intended
to supersede existing working methods within WGs that have existing chartered work in
this area. </t>
<t>This process is not intended to govern Performance Metric development
in existing IETF WG that are focused on metrics development, such as
IPPM and BMWG. However, this guidelines document may be useful in
these activities, and MAY be applied where appropriate. A typical example
is the development of Performance Metrics to be exported with the IPFIX
protocol <xref target="RFC5101">RFC 5101</xref>, with specific IPFIX information
elements <xref target="RFC5102">RFC 5102</xref>, which would benefit from
the framework in this document. </t>
<t>The framework in this document applies to Performance Metrics derived from
both active and passive measurements.</t>
</section>
<section title="Relationship between QoS, QoE and Application-specific Performance Metrics">
<t> Network QoS deals with network and network protocol performance, while QoE
deals with the assessment of a user's experience in a context of a task or a
service. As a result, the topic of application-specific Performance Metrics includes the
measurement of performance at layers between IP and the user.
For example, network QoS metrics (packet loss, delay, and delay variation
<xref target="RFC5481"></xref>) can be used to estimate application-specific
Performance Metrics (de-jitter buffer size and RTP-layer packet loss), then
combined with other known aspects of a VoIP application (such as codec type)
to estimate a Mean Opinion Score (MOS) <xref target="P.800"></xref>.
However, the QoE for a particular VoIP user depends on the specific context,
such as a casual conversation, a business conference call, or an emergency call.
Finally, QoS and application-specific Performance Metrics are quantitative, while QoE is
qualitative. Also network QoS and application-specific Performance Metrics can be
directly or indirectly evident to the user, while the QoE is directly evident.</t>
</section>
<section title="Performance Metrics Development">
<t>This section provides key definitions and qualifications of
Performance Metrics.</t>
<section title="Identifying and Categorizing the Audience">
<t>Many of the aspects of metric definition and reporting, even the
selection or determination of the essential metrics, depend on who
will use the results, and for what purpose. For example, the metric description
SHOULD include use cases and example reports that illustrate service quality
monitoring and maintenance or identification and quantification of problems.</t>
<t>All documents defining Performance Metrics SHOULD identify the primary
audience and its associated requirements. The audience can influence
both the definition of metrics and the methods of measurement.</t>
<t>The key areas of variation between different metric users include:</t>
<t><list style="symbols">
<t>Suitability of passive measurements of live traffic, or active
measurements using dedicated traffic</t>
<t>Measurement in laboratory environment, or on a network of deployed
devices</t>
<t>Accuracy of the results</t>
<t>Access to measurement points and configuration information</t>
<t>Measurement topology (point-to-point, point-to-multipoint)</t>
<t>Scale of the measurement system</t>
<t>Measurements conducted on-demand, or continuously</t>
<t>Required reporting formats and periods</t>
<t>Sampling criteria, such systematic or probabilistic</t>
<t>Period (and duration) of measurement, as the live traffic can have patterns</t>
</list></t>
</section>
<section title="Definitions of a Performance Metric">
<t>A Performance Metric is a measure of an observable behavior of a networking technology,
an application, or a service. Most of the time, the Performance Metric can be
directly measured however, sometimes, the Performance Metric value is computed.
The process for determining the value of a metric may assume some implicit or
explicit underlying statistical process, in this case, the Performance Metric is
an estimate of a parameter of this process, assuming that the statistical process
closely models the behavior of the system.</t>
<t>A Performance Metric should serve some defined purpose. This may include the
measurement of capacity, quantifying how bad some problem is,
measurement of service level, problem diagnosis or location and other
such uses. A Performance Metric may also be an input to some other process, for
example the computation of a composite Performance Metric or a model or simulation
of a system. Tests of the "usefulness" of a Performance Metric include:</t>
<t><list style="empty">
<t>(i) the degree to which its absence would cause significant
loss of information on the behavior or performance of the application or
system being measured</t>
<t>(ii) the correlation between the Performance Metric, the QoS
<xref target="G.1000"></xref> and QoE delivered to the
user (person or other application)</t>
<t>(iii) the degree to which the Performance Metric is able to support the
identification and location of problems affecting service
quality.</t>
<t>(iv) the requirement to develop policies (Service Level Agreement,
and potentially Service Level Contract) based on the Performance Metric.</t>
</list>For example, consider a distributed application operating
over a network connection that is subject to packet loss. A Packet
Loss Rate (PLR) Performance Metric is defined as the mean packet loss ratio over
some time period. If the application performs poorly over network
connections with high packet loss ratio and always performs well when
the packet loss ratio is zero then the PLR Performance Metric is useful to some
degree. Some applications are sensitive to short periods of high loss
(bursty loss) and are relatively insensitive to isolated packet loss
events; for this type of application there would be very weak
correlation between PLR and application performance. A "better" Performance Metric
would consider both the packet loss ratio and the distribution of loss
events. If application performance is degraded when the PLR exceeds
some rate then a useful Performance Metric may be a measure of the duration and
frequency of periods during which the PLR exceeds that rate (as for example in RFC3611).</t>
</section>
<section title="Computed Performance Metrics">
<section title="Composed Performance Metrics">
<t>Some Performance Metrics may not be measured directly, but can be composed from
base metrics that have been measured. A composed Performance Metric is derived from
other metrics by applying a deterministic process or function (e.g.,
a composition function). The process may use metrics that are identical
to the metric being composed, or metrics that are dissimilar, or some
combination of both types. Usually the base metrics have a limited scope
in time or space, and they can be combined to estimate the performance
of some larger entities.</t>
<t>Some examples of composed Performance Metrics and composed Performance Metric definitions
are:</t>
<list>
<t>Spatial composition is defined as the composition of metrics of the
same type with differing spatial domains
<xref target="RFC5835"></xref>
<xref target="RFC6049"></xref>. Ideally, for spatially
composed metrics to be meaningful, the spatial domains should be non-overlapping
and contiguous, and the composition operation should be mathematically appropriate
for the type of metric.</t>
<t>Temporal composition is defined as the composition of sets of metrics
of the same type with differing time spans <xref target="RFC5835"></xref>. For temporally
composed metrics to be meaningful, the time spans should be
non-overlapping and contiguous, and the composition operation should
be mathematically appropriate for the type of metric.</t>
<t>Temporal aggregation is a summarization of metrics into a smaller
number of metrics that relate to the total time span covered by the
original metrics. An example would be to compute the minimum,
maximum and average values of a series of time sampled values of a
metric.</t>
</list>
<t>In the context of flow records in IP Flow Information eXport (IPFIX), the IPFIX
Mediation: Framework <xref target="RFC6183"></xref> also discusses some
aspects of the temporal and spatial composition. </t>
</section>
<section title="Index">
<t>An Index is a metric for which the output value range has been
selected for convenience or clarity, and the behavior of which is
selected to support ease of understanding; for example the R Factor
<xref target="G.107"></xref>. The deterministic function for an index
is often developed after the index range and behavior have been
determined.</t>
</section>
</section>
<section title="Performance Metric Specification">
<section title="Outline">
<t>A Performance Metric definition MUST have a normative part that defines what
the metric is and how it is measured or computed and SHOULD have an
informative part that describes the Performance Metric and its application. </t>
</section>
<section title="Normative parts of Performance Metric definition">
<t>The normative part of a Performance Metric definition MUST define at least the
following: </t>
<t>(i) Metric Name</t>
<t> Performance Metric names are RECOMMENDED to be unique within the set of metrics being
defined for the protocol layer and context. While strict uniqueness may not be attainable
(See the IPPM registry <xref target="RFC6248"></xref> for an example of IANA metric registry
failing to provide sufficient specificity), broad review must be sought to avoid naming
overlap. Note that the Performance Metrics Directorate can help with suggestions for IANA
metric registration for unique naming. The Performance Metric name MAY be descriptive.</t>
<t> (ii) Metric Description</t>
<t> The Performance Metric description MUST explain what the metric is, what is being
measured and how this relates to the performance of the system being
measured.</t>
<t> (iii) Method of Measurement or Calculation</t>
<t>
The method of measurement or calculation MUST define what is being
measured or computed and the specific algorithm to be used. Does the
measurement involve active or only passive measurements? Terms such
as "average" should be qualified (e.g. running average or average over
some interval). Exception cases SHOULD also be defined with the
appropriate handling method. For example, there are a number of commonly
used metrics related to packet loss; these often don't define the criteria
by which a packet is determined to be lost (vs very delayed) or how
duplicate packets are handled. For example, if the average packet
loss rate during a time interval is reported, and a packet's arrival
is delayed from one interval to the next then was it "lost" during
the interval during which it should have arrived or should it be
counted as received?</t>
<t>Some methods of calculation might require discarding some data
collected (due to outliers) so as to make the measurement parameters
meaningful. One example is burstable billing that sorts the 5-min samples,
and discard the top 5 percentile.</t>
<t>Some parameters linked to the method MAY also be reported, in
order to fully interpret the Performance Metric. For example, the
time interval, the load, the minimum packet loss, the potential measurement
errors and their sources, the attainable accuracy of the metric (e.g. +/-0,1),
the method of caluclation, etc...</t>
<t>(iv) Units of measurement </t>
<t>The units of measurement MUST be clearly stated.</t>
<t> (v) Measurement Point(s)</t>
<t>If the measurement is specific to a measurement point, this SHOULD be
defined. The measurement domain MAY also be defined. Specifically, if
measurement points are spread across domains, the measurement domain
(intra-, inter-) is another factor to consider.</t>
<t>The Performance Metric definition should discuss how the Performance Metric value might
vary depending which measurement point is chosen. For example, the time between a SIP
request <xref target="RFC3261"></xref> and the final response can be significantly different
at the User Agent Client (UAC) or User Agent Server (UAS).</t>
<t>In some cases, the measurement requires multiple measurement points: all measurement
points SHOULD be defined, including the measurement domain(s).</t>
<t> (vi) Measurement timing</t>
<t>The acceptable range of timing intervals or sampling intervals for a
measurement and the timing accuracy required for such intervals MUST
be specified. Short sampling intervals or frequent samples provide
a rich source of information that can help to assess application
performance but may lead to excessive measurement data. Long
measurement or sampling intervals reduce the amount of reported
and collected data such that it may be insufficient to understand
application performance or service quality insofar as the measured
quantity may vary significantly with time.</t>
<t>In case of multiple measurement points, the potential requirement
for synchronized clocks must be clearly specified. In the specific example
of the IP delay variation application metric, the different aspects of synchronized
clocks are discussed in <xref target="RFC5481"></xref>.</t>
</section>
<section title="Informative parts of Performance Metric definition"></section>
<t>The informative part of a Performance Metric specification is intended to support
the implementation and use of the metric. This part SHOULD provide
the following data:</t>
<t>(i) Implementation </t>
<t>The implementation description MAY be in the form of text, algorithm
or example software. The objective of this part of the metric
definition is to assist implementers to achieve consistent results.</t>
<t>(ii) Verification</t>
<t>The Performance Metric definition SHOULD provide guidance on verification
testing. This may be in the form of test vectors, a formal
verification test method or informal advice.</t>
<t>(iii) Use and Applications</t>
<t>The use and applications description is intended to assist the "user"
to understand how, when and where the metric can be applied, and what
significance the value range for the metric may have. This MAY
include a definition of the "typical" and "abnormal" range of the
Performance Metric, if this was not apparent from the nature of the metric.
The description MAY include information about the influence of extreme
measurement values, i.e. if the Performance Metric is sensitive to
outliers. The Use and Application section SHOULD also include the
security implications in the description.
</t>
<t>For example: </t>
<t>(a) it is fairly intuitive that a lower packet loss ratio
would equate to better performance. However the user may
not know the significance of some given packet loss ratio,</t>
<t>(b) the speech level of a telephone signal is commonly expressed
in dBm0. If the user is presented with:</t>
<t>Speech level = -7 dBm0 </t>
<t>this is not intuitively understandable, unless the user is a
telephony expert. If the metric definition explains that the
typical range is -18 to -28 dBm0, a value higher than -18
means the signal may be too high (loud) and less than -28
means that the signal may be too low (quiet), it is much
easier to interpret the metric. </t>
<t>(iv) Reporting Model</t>
<t>The reporting model definition is intended to make any relationship
between the metric and the reporting model clear. There are often
implied relationships between the method of reporting metrics and the
metric itself, however these are often not made apparent to the
implementor. For example, if the metric is a short term running average
packet delay variation (e.g. the interarrival jitter in <xref target="RFC3550">
</xref>) and this value is reported at intervals of 6-10 seconds,
the resulting measurement may have limited accuracy when packet delay variation
is non-stationary.</t>
<section title="Performance Metric Definition Template">
<t></t>
</section>
<t>Normative</t>
<list style="symbols">
<t>Metric Name</t>
<t>Metric Description</t>
<t>Method of Measurement or Calculation</t>
<t>Units of Measurement</t>
<t>Measurement Point(s) with potential Measurement Domain</t>
<t>Measurement Timing</t>
</list>
<t>Informative</t>
<list style="symbols">
<t>Implementation</t>
<t>Verification</t>
<t>Use and Applications</t>
<t>Reporting Model</t>
</list>
<section title="Example: Loss Rate">
<t>The example used is the loss rate metric as specified in <xref target="RFC3611"> RFC 3611</xref>.</t>
<t>Metric Name: LossRate</t>
<t>Metric Description: The fraction of RTP data packets from the source
lost since the beginning of reception.</t>
<t>Method of measurement or calculation: This value is
calculated by dividing the total number of packets lost (after
the effects of applying any error protection such as FEC) by
the total number of packets expected, multiplying the result of
the division by 256, limiting the maximum value to 255 (to
avoid overflow), and taking the integer part.</t>
<t>Units of Measurement: This metric is expressed as a fixed point number
with the binary point at the left edge of the field. For example, a metric
value of 12 means a loss rate of approximately 5%.</t>
<t>Measurement Point(s): This metric is made at the receiving end of
the RTP stream sent during a Voice over IP call.</t>
<t>Measurement Timing: This metric can be used over a wide range of time
intervals. Using time intervals of longer than one hour may prevent
the detection of variations in the value of this metric due to time-
of-day changes in network load. Timing intervals should not vary
in duration by more than +/- 2%.</t>
<t>Implementation: The numbers of duplicated packets and discarded packets do
not enter into this calculation. Since receivers cannot be required to
maintain unlimited buffers, a receiver MAY categorize late-arriving
packets as lost. The degree of lateness that triggers a loss SHOULD be
significantly greater than that which triggers a discard.</t>
<t>Verification: The metric value ranges between 0 and 255.</t>
<t>Use and Applications: This metric is useful for monitoring VoIP calls. More
precisely, to detect the VoIP loss rate in the network. This loss rate, along
with the rate of packets discarded due to jitter, has some effect on the quality
of the voice stream.</t>
<t>Reporting Model: This metric needs to be associated with a defined
time interval, which could be defined by fixed intervals or by a
sliding window. In the context of RFC3611 the metric is measured continuously from the
start of the RTP stream, the value of the metric is sampled and reported in RTCP
XR VoIP Metrics reports</t>
</section>
</section>
<section title="Dependencies">
<t>This section introduces several Performance Metrics dependencies, which the
Performance Metric designer should keep in mind during the Performance Metric
development. These dependencies, and any others not listed here, SHOULD be documented in
the Performance Metric specifications.
</t>
<section title="Timing accuracy">
<t>The accuracy of the timing of a measurement may affect the accuracy
of the Performance Metric. This may not materially affect a sampled value metric
however would affect an interval based metric. Some metrics, for
example the number of events per time interval, would be directly
affected; for example a 10% variation in time interval would
lead directly to a 10% variation in the measured value. Other
metrics, such as the average packet loss ratio during some time
interval, would be affected to a lesser extent.
</t>
<t>If it is necessary to correlate sampled values or intervals then it
is essential that the accuracy of sampling time and interval start/
stop times is sufficient for the application (for example +/- 2%).
</t>
</section>
<section title="Dependencies of Performance Metric definitions on related events or metrics">
<t>Performance Metric definitions may explicitly or implicitly rely on factors that
may not be obvious. For example, the recognition of a packet as
being "lost" relies on having some method to know the packet was
actually lost (e.g. RTP sequence number), and some time threshold
after which a non-received packet is declared as lost. It is
important that any such dependencies are recognized and incorporated
into the metric definition.
</t>
</section>
<section title="Relationship between Performance Metric and lower layer
Performance Metrics">
<t>Lower layer Performance Metrics may be used to compute or infer the performance
of higher layer applications, potentially using an application
performance model. The accuracy of this will depend on many factors
including:
</t>
<t>
(i) The completeness of the set of metrics - i.e. are there metrics
for all the input values to the application performance model?
</t>
<t>
(ii) Correlation between input variables (being measured) and
application performance
</t>
<t>
(iii) Variability in the measured metrics and how this variability
affects application performance
</t>
</section>
<section title="Middlebox presence">
<t>Presence of a middlebox <xref target="RFC3303"></xref>, e.g.,
proxy, network address translation (NAT), redirect server, session border
controller (SBC, <xref target="RFC5853"></xref>), and application layer gateway (ALG) may add variability
to or restrict the scope of measurements of a metric. For example, an SBC
that does not process RTP loopback packets may block or locally terminate
this traffic rather then pass it through to its target.</t>
</section>
</section>
<section title="Organization of Results">
<t>The IPPM Framework [RFC2330] organizes the results of metrics into
three related notions:</t>
<t><list style="symbols">
<t>singleton, an elementary instance, or "atomic" value.</t>
<t>sample, a set of singletons with some common properties and some
varying properties.</t>
<t>statistic, a value derived from a sample through deterministic
calculation, such as the mean.</t>
</list></t>
<t>Performance Metrics MAY use this organization for the results, with or
without the term names used by IPPM WG. Section 11 of
<xref target="RFC2330">RFC 2330</xref> should consulted for further details.</t>
</section>
<section title="Parameters, the variables of a Performance Metric">
<t>Metrics are completely defined when all options and input variables
have been identified and considered. These variables are sometimes
left unspecified in a metric definition, and their general name
indicates that the user must set them and report them with the
results. Such variables are called "parameters" in the IPPM metric
template. The scope of the metric, the time at which it was
conducted, the length interval of the sliding window measurement,
the settings for timers and the thresholds for counters
are all examples of parameters.</t>
<t>All documents defining Performance Metric SHOULD identify all key
parameters for each Performance Metric.</t>
</section>
</section>
<section title="Performance Metric Development Process">
<t></t>
<section title="New Proposals for Performance Metrics">
<t>This process is intended to add additional considerations to the
processes for adopting new work as described in RFC 2026 <xref
target="RFC2026"></xref> and RFC 2418 <xref target="RFC2418"></xref>.
Note that new Performance Metrics work item proposals SHALL be
approved using the existing IETF process. The following entry criteria will be considered
for each proposal.</t>
<t>Proposals SHOULD be prepared as Internet Drafts, describing the
Performance Metric and conforming to the qualifications above as much as
possible. Proposals SHOULD be deliverables of the corresponding protocol
development WG charters. As such, the Proposals SHOULD be vetted by that
WG prior to discussion by the Performance Metrics Directorate. This
aspect of the process includes an assessment of the need for the
Performance Metric proposed and assessment of the support for their
development in IETF.
</t>
<t>Proposals SHOULD include an assessment of interaction and/or overlap
with work in other Standards Development Organizations. Proposals SHOULD
identify additional expertise that might be consulted.
</t>
<t>Proposals SHOULD specify the intended audience and users of the
Performance Metrics. The development process encourages participation by members
of the intended audience.</t>
<t>Proposals SHOULD identify any security and IANA requirements.
Security issues could potentially involve revealing of user
identifying data or the potential misuse of active test tools. IANA
considerations may involve the need for a Performance Metrics registry.</t>
</section>
<section title="Reviewing Metrics">
<t>Each Performance Metric SHOULD be assessed according to the following list of
qualifications:</t>
<list style="symbols">
<t>Are the performance metrics unambiguously defined?</t>
<t>Are the units of measure specified?</t>
<t>Does the metric clearly define the measurement interval where applicable?</t>
<t>Are significant sources of measurement errors identified and discussed?</t>
<t>Does the method of measurement ensure that results are repeatable?</t>
<t>Do the metric or method of measurement appear to be implement-able,
(or offer evidence of working implementation)?</t>
<t>Are there any undocumented assumptions concerning the underlying
process that would affect an implementation or interpretation
of the metric?</t>
<t>Can the metric results related to application performance or user
experience, when such a relationship is of value?</t>
<t>Relationship to metrics defined elsewhere within IETF or within
other SDO's</t>
<t>Do the Security Considerations adequately address denial of service
attacks, unwanted interference with the metric/measurement, and
user data confidentiality (when measuring live traffic)?</t>
</list>
</section>
<section title="Performance Metrics Directorate Interaction with other WGs">
<t>The Performance Metrics Directorate SHALL provide guidance to the related
protocol development WG when considering an Internet Draft that specifies
Performance Metrics for a protocol. A sufficient number of individuals
with expertise must be willing to consult on the draft. If the related
WG has concluded, comments on the proposal should still be sought from
key RFC authors and former chairs.</t>
<t>A formal review is recommended by the time the document is reviewed by the Area
Directors, or an IETF Last Call is being conducted - same as expert reviews are being
performed by other directorates.</t>
<t>Existing mailing lists SHOULD be used, however a dedicated mailing
list MAY be initiated if necessary to facilitate work on a draft.</t>
<t>In some cases, it will be appropriate to have the IETF session
discussion during the related protocol WG session, to maximize
visibility of the effort to that WG and expand the review.</t>
</section>
<section title="Standards Track Performance Metrics">
<t>
The Performance Metrics Directorate will assist with the progression of RFCs
along the Standards Track. See <xref target="I-D.bradner-metricstest"></xref>.
This may include the preparation of test plans to examine different
implementations of the metrics to ensure that the metric definitions
are clear and unambiguous (depending on the final form of the draft
above).
</t>
</section>
</section>
<section anchor="IANA" title="IANA Considerations">
<t>This document makes no request of IANA.</t>
<t>Note to RFC EDITOR: this section may be removed on publication as an
RFC.</t>
</section>
<section anchor="Security" title="Security Considerations">
<t>In general, the existence of a framework for Performance Metric
development does not constitute a security issue for the Internet.
Performance Metric definitions may introduce security issues and this framework
recommends that those defining Performance Metrics should identify any such risk
factors.</t>
<t>The security considerations that apply to any active measurement of
live networks are relevant here. See <xref target="RFC4656"></xref>.</t>
<t>The security considerations that apply to any passive measurement of
specific packets in live networks are relevant here as well. See the security
considerations in <xref target="RFC5475"></xref>.</t>
</section>
<section anchor="Acknowledgements" title="Acknowledgements">
<t>The authors would like to thank Al Morton, Dan Romascanu, Daryl
Malas and Loki Jorgenson for their comments and contributions.
The authors would like to thank Aamer Akhter, Yaakov Stein, Carsten Schmoll,
and Jan Novak for their reviews.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2026"?>
<?rfc include="reference.RFC.2119"?>
<?rfc include="reference.RFC.2418"?>
<?rfc include='reference.RFC.4656'?>
</references>
<references title="Informative References">
<?rfc include='reference.RFC.0793'?>
<?rfc include='reference.RFC.2330'?>
<?rfc include='reference.RFC.3261'?>
<?rfc include='reference.RFC.3303'?>
<?rfc include='reference.RFC.3550'?>
<?rfc include='reference.RFC.3611'?>
<?rfc include='reference.RFC.4710'?>
<?rfc include='reference.RFC.4960'?>
<?rfc include='reference.RFC.5101'?>
<?rfc include='reference.RFC.5102'?>
<?rfc include='reference.RFC.5481'?>
<?rfc include='reference.RFC.5835'?>
<?rfc include='reference.RFC.5475'?>
<?rfc include='reference.RFC.5706'?>
<?rfc include='reference.RFC.5853'?>
<?rfc include='reference.RFC.6035'?>
<?rfc include='reference.RFC.6049'?>
<?rfc include='reference.RFC.6183'?>
<?rfc include='reference.RFC.6248'?>
<?rfc include='reference.I-D.bradner-metricstest'?>
<reference anchor="E.800">
<front>
<title>ITU-T Recommendation E.800. SERIES E: OVERALL NETWORK
OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN FACTORS
</title>
</front>
</reference>
<reference anchor="G.1000">
<front>
<title>ITU-T Recommendation G.1000. Communications Quality of
Service: A framework and definitions</title>
</front>
</reference>
<reference anchor="P.800">
<front>
<title>ITU-T Recommendation P.800. : Methods for subjective
determination of transmission quality
</title>
</front>
</reference>
<reference anchor="G.107">
<front>
<title>ITU-T Recommendation G.107. : The E-model, a computational model for use in transmission planning.
</title>
</front>
</reference>
</references>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-24 01:07:55 |