Network Working Group A. Clark
Internet-Draft Telchemy Incorporated
Intended status: BCP B. Claise
Expires: July 17, 2011 Cisco Systems, Inc.
January 13, 2011
Guidelines for Considering New Performance Metric Development
draft-ietf-pmol-metrics-framework-07
Abstract
This document describes a framework and a process for developing
performance metrics of protocols and applications transported over
over IETF-specified protocols, and that can be used to characterize
traffic on live networks and services.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
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This Internet-Draft will expire on July 17, 2011.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Background and Motivation . . . . . . . . . . . . . . . . 4
1.2. Organization of this document . . . . . . . . . . . . . . 5
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.1. Performance Metrics Entity . . . . . . . . . . . . . . . . 6
2.2. Quality of Service . . . . . . . . . . . . . . . . . . . . 6
2.3. Quality of Experience . . . . . . . . . . . . . . . . . . 6
2.4. Performance Metric . . . . . . . . . . . . . . . . . . . . 7
3. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 7
4. Relationship between QoS, QoE and Application-specific
Performance Metrics . . . . . . . . . . . . . . . . . . . . . 7
5. Performance Metrics Development . . . . . . . . . . . . . . . 8
5.1. Identifying and Categorizing the Audience . . . . . . . . 8
5.2. Definitions of a Performance Metric . . . . . . . . . . . 9
5.3. Computed Metrics . . . . . . . . . . . . . . . . . . . . . 10
5.3.1. Composed Metrics . . . . . . . . . . . . . . . . . . . 10
5.3.2. Index . . . . . . . . . . . . . . . . . . . . . . . . 10
5.4. Performance Metric Specification . . . . . . . . . . . . . 11
5.4.1. Outline . . . . . . . . . . . . . . . . . . . . . . . 11
5.4.2. Normative parts of Performance Metric definition . . . 11
5.4.3. Informative parts of Performance Metric definition . . 12
5.4.4. Performance Metric Definition Template . . . . . . . . 13
5.4.5. Example: Burst Packet Loss Frequency . . . . . . . . . 14
5.5. Dependencies . . . . . . . . . . . . . . . . . . . . . . . 15
5.5.1. Timing accuracy . . . . . . . . . . . . . . . . . . . 15
5.5.2. Dependencies of Performance Metric definitions on
related events or metrics . . . . . . . . . . . . . . 15
5.5.3. Relationship between Performance Metric and lower
layer performance metrics . . . . . . . . . . . . . . 16
5.5.4. Middlebox presence . . . . . . . . . . . . . . . . . . 16
5.6. Organization of Results . . . . . . . . . . . . . . . . . 16
5.7. Parameters, the variables of a Performance Metric . . . . 16
6. Performance Metric Development Process . . . . . . . . . . . . 17
6.1. New Proposals for Metrics . . . . . . . . . . . . . . . . 17
6.2. Reviewing Metrics . . . . . . . . . . . . . . . . . . . . 17
6.3. Proposal Approval . . . . . . . . . . . . . . . . . . . . 18
6.4. Performance Metrics Entity Interaction with other WGs . . 18
6.5. Standards Track Performance Metrics . . . . . . . . . . . 19
6.6. Recommendations . . . . . . . . . . . . . . . . . . . . . 19
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 19
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 20
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 20
10.1. Normative References . . . . . . . . . . . . . . . . . . . 20
10.2. Informative References . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
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1. Introduction
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
There are at least three phases in the development of performance
standards. They are:
1. Definition of a performance metric and its units of measure
2. Specification of a method of measurement
3. Specification of the reporting format
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.
The intended audience for this document includes, but is not
restricted to, IETF participants who write performance metrics
documents in the IETF, reviewers of such documents, and members of
the Performance Metrics Entity.
1.1. Background and Motivation
Although the IETF has two active Working Groups (WGs) dedicated to
the development of performance metrics, they each have strict
limitations in their charters:
- The Benchmarking Methodology WG has addressed a range of networking
technologies and protocols in their long history (such as IEEE 802.3,
ATM, Frame Relay, and Routing Protocols), but the charter strictly
limits their performance characterizations to the laboratory
environment.
- The IP Performance Metrics (IPPM) WG has developed a set of
standard metrics that can be applied to the quality, performance, and
reliability of Internet data delivery services. The IPPM metrics
development is applicable to live IP networks, but it is specifically
prohibited from developing metrics that characterize traffic at upper
layers, such as a VoIP stream.
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A BOF held at IETF-69 introduced the IETF community to the
possibility of a generalized activity to define standardized
performance metrics. The existence of a growing list of Internet-
Drafts on performance metrics (with community interest in
development, but in un-chartered areas) illustrates the need for
additional performance work. The majority of people present at the
birds Of a feather (BOF) supported the proposition that IETF should
be working in these areas, and no one objected to any of the
proposals.
Previous IETF work related to reporting of application performance
metrics includes the Real-time Application Quality-of-Service
Monitoring (RAQMON) Framework RFC 4710 [RFC4710], 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) RFC
3611 [RFC3611] and the SIP RTCP Summary Report Protocol [RFC6035] 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.
The IETF is also actively involved in the development of reliable
transport protocols which would affect the relationship between IP
performance and application performance.
Thus there is a gap in the currently chartered coverage of IETF WGs:
development of performance metrics for protocols above and below the
IP-layer that can be used to characterize performance on live
networks.
This document refers to a Performance Metrics Entity, whose goal is
to advice and support the Performance Metric development at the IETF.
A recommendation about the Performance Metrics Entity is made in
Section 6.6.
Similarly to the "Guidelines for Considering Operations and
Management of New Protocols and Protocol Extensions" RFC 5706
[RFC5706], which is the reference document for the IETF Operations
Directorate, this document should be consulted as part of the new
performance metric review.
1.2. Organization of this document
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
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to develop these metrics that is applicable to the IETF environment.
2. Terminology
2.1. Performance Metrics Entity
The Performance Metrics Entity is a directorate that coordinates the
performance metric development in the IETF.
The Performance Metrics Entity should be composed of experts in the
performance community, potentially selected from the IPPM, BMWG, and
PMOL WGs.
2.2. Quality of Service
Quality of Service (QoS) is defined in a similar way to the ITU "QoS
experienced/perceived by customer/user (QoE)" E.800 [E.800], 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."
2.3. Quality of Experience
Quality of Experience (QoE) is defined in a similar way to the ITU
"QoS experienced/perceived by customer/user (QoE)" E.800 [E.800],
i.e.: "a statement expressing the level of quality that customers/
users believe they have experienced."
NOTE 1 - The level of QoS experienced and/or perceived by the
customer/user may be expressed by an opinion rating.
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).
NOTE 3 - The qualitative component can be influenced by user
expectations, ambient conditions, psychological factors, application
context, etc.
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.
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2.4. Performance Metric
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.
3. Purpose and Scope
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 will
not define any performance metrics.
The scope of this document covers guidelines for considering new
Performance Metric development. However this document is not
intended to supercede existing working methods within WGs that have
existing chartered work in this area.
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 RFC 5101 [RFC5101], with specific IPFIX
information elements RFC 5102 [RFC5102], which would benefit from the
framework in this document.
The framework in this document applies to performance metrics derived
from both active and passive measurements.
4. Relationship between QoS, QoE and Application-specific Performance
Metrics
Network QoS deals with the 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 opportunities
to quantify performance at layers between IP and the user. For
example, network QoS metrics (packet loss, delay, and delay variation
[RFC5481]) 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
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codec type) to estimate a Mean Opinion Score (MOS) [P.800]. 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.
5. Performance Metrics Development
This section provides key definitions and qualifications of
Performance Metrics.
5.1. Identifying and Categorizing the Audience
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: in order to properly
maintain service quality? or to identify and quantify problems? The
question, "How will the results be used?" usually yields important
factors to consider when developing performance metrics.
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.
The key areas of variation between different metric users include:
o Suitability of passive measurements of live traffic, or active
measurements using dedicated traffic
o Measurement in laboratory environment, or on a network of deployed
devices
o Accuracy of the results
o Access to measurement points and configuration information
o Measurement topology (point-to-point, point-to-multipoint)
o Scale of the measurement system
o Measurements conducted on-demand, or continuously
o Required reporting formats and periods
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5.2. Definitions of a Performance Metric
A metric is a measure of an observable behavior of an networking
technology, an application, or a service. Most of the time, the
metric can be directly measured. However, sometimes, the metric
definition is computed: it assumes some implicit or explicit
underlying statistical process. In such case, the metric is an
estimate of a parameter of this process, assuming that the
statistical process closely models the behavior of the system.
A 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 metric may also be an input to some other process, for
example the computation of a composite metric or a model or
simulation of a system. Tests of the "usefulness" of a metric
include:
(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
(ii) the correlation between the performance metric, the QoS
[G.1000] and QoE delivered to the user (person or other
application)
(iii) the degree to which the metric is able to support the
identification and location of problems affecting service quality.
(iv) the requirement to develop policies (Service Level Agreement,
and potentially Service Level Contract) based on the metric.
For example, consider a distributed application operating over a
network connection that is subject to packet loss. A Packet Loss
Rate (PLR) 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 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"
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 metric may be a measure of the
duration and frequency of periods during which the PLR exceeds that
rate.
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5.3. Computed Metrics
5.3.1. Composed Metrics
Some metrics may not be measured directly, but can be composed from
base metrics that have been measured. A composed 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.
Some examples of composed metrics and composed metric definitions
are:
Spatial composition is defined as the composition of metrics of the
same type with differing spatial domains [RFC5835] [RFC6049]. 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.
Temporal composition is defined as the composition of sets of metrics
of the same type with differing time spans [RFC5835]. 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.
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.
In the context of flow records in IP Flow Informatin eXport (IPFIX),
the IPFIX Mediation: Framework [I-D.ietf-ipfix-mediators-framework]
also discusses some aspects of the temporal and spatial composition.
5.3.2. Index
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
[G.107]. The deterministic function for an index is often developed
after the index range and behavior have been determined.
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5.4. Performance Metric Specification
5.4.1. Outline
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.
5.4.2. Normative parts of Performance Metric definition
The normative part of a Performance Metric definition MUST define at
least the following:
(i) Metric Name
Performance Metric names MUST be unique within the set of metrics
being defined and MAY be descriptive.
(ii) Metric Description
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.
(iii) Method of Measurement or Calculation
This 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?
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) etc..
(iv) Units of measurement
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The units of measurement MUST be clearly stated.
(v) Measurement Point(s)
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.
In some cases, the measurement requires multiple measurement points:
all measurement points SHOULD be defined, including the measurement
domain(s).
(vi) Measurement timing
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.
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 [RFC5481].
5.4.3. Informative parts of Performance Metric definition
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:
(i) Implementation
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 consistents results.
(ii) Verification
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.
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(iii) Use and Applications
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.
For example:
(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,
(b) the speech level of a telephone signal is commonly expressed in
dBm0. If the user is presented with:
Speech level = -7 dBm0
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.
(iv) Reporting Model
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. RFC 3550) 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.
5.4.4. Performance Metric Definition Template
Normative
o Metric Name
o Metric Description
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o Method of Measurement or Calculation
o Units of Measurement
o Measurement Point(s) with potential Measurement Domain
o Measurement Timing
Informative
o Implementation
o Verification
o Use and Applications
o Reporting Model
5.4.5. Example: Burst Packet Loss Frequency
The burst packet loss frequency can be observed at different layers.
The following example is specific to RTP RFC 3550 [RFC3550].
Metric Name: BurstPacketLossFrequency
Metric Description: A burst of packet loss is defined as a longest
period starting and ending with lost packets during which no more
than Gmin consecutive packets are received. The
BurstPacketLossFrequency is defined as the number of bursts of packet
loss occurring during a specified time interval (e.g. per minute, per
hour, per day). If Gmin is set to 0 then a burst of packet loss
would comprise only consecutive lost packets, whereas a Gmin of 16
would define bursts as periods of both lost and received packets
(sparse bursts) having a loss rate of greater than 5.9%.
Method: Bursts may be detected using the Markov Model algorithm
defined in RFC3611. The BurstPacketLossFrequency is calculated by
counting the number of burst events within the defined measurement
interval. A burst that spans the boundary between two time intervals
shall be counted within the later of the two intervals.
Units of Measurement: Bursts per time interval (e.g. per second, per
hour, per day)
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
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duration by more than +/- 2%.
Implementation Guidelines: See RFC3611.
Verification Testing: See Appendix for C code to generate test
vectors.
Use and Applications: This metric is useful to detect IP network
transients that affect the performance of applications such as Voice
over IP or IP Video. The value of Gmin may be selected to ensure
that bursts correspond to a packet loss ratio that would degrade the
performance of the application of interest (e.g. 16 for VoIP).
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.
5.5. Dependencies
5.5.1. Timing accuracy
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.
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%).
5.5.2. Dependencies of Performance Metric definitions on related events
or metrics
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.
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5.5.3. Relationship between Performance Metric and lower layer
performance metrics
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:
(i) The completeness of the set of metrics - i.e. are there metrics
for all the input values to the application performance model?
(ii) Correlation between input variables (being measured) and
application performance
(iii) Variability in the measured metrics and how this variability
affects application performance
5.5.4. Middlebox presence
Presence of a middlebox RFC 3303 [RFC3303], e.g., proxy, network
address translation (NAT), redirect server, session border controller
(SBC), 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.
5.6. Organization of Results
The IPPM Framework [RFC2330] organizes the results of metrics into
three related notions:
o singleton, an elementary instance, or "atomic" value.
o sample, a set of singletons with some common properties and some
varying properties.
o statistic, a value derived from a sample through deterministic
calculation, such as the mean.
Many Performance Metrics MAY use this organization for the results,
with or without the term names used by IPPM WG. Section 11 of RFC
2330 [RFC2330] should consulted for further details.
5.7. Parameters, the variables of a Performance Metric
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
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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 settings for timers and the thresholds for counters
are all examples of parameters.
All documents defining Performance Metric SHOULD identify all key
parameters for each Performance Metric.
6. Performance Metric Development Process
6.1. New Proposals for Metrics
This process is intended to add additional considerations to the
processes for adopting new work as described in RFC 2026 [RFC2026]
and RFC 2418 [RFC2418]. The following entry criteria will be
considered for each proposal.
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
Entity. 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.
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.
Proposals SHOULD specify the intended audience and users of the
Performance Metrics. The development process encourages
participation by members of the intended audience.
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.
6.2. Reviewing Metrics
Each Performance Metric SHOULD be assessed according to the following
list of qualifications:
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o Unambiguously defined?
o Units of Measure Specified?
o Measurement Interval Specified?
o Measurement Errors Identified?
o Repeatable?
o Implementable?
o Assumptions concerning underlying process?
o Use cases?
o Correlation with application performance/ user experience?
6.3. Proposal Approval
New work item proposals SHALL be approved using the existing IETF
process.
In all cases, the proposal will need to achieve consensus, in the
corresponding protocol development WG (or alternatively, an "Area" WG
with broad charter), that there is interest and a need for the work.
The approval SHOULD include the following steps
o consultation with the Performance Metrics Entity, using this
document
o consultation with Area Director(s)
o and possibly IESG approval of a new or revised charter for the WG
6.4. Performance Metrics Entity Interaction with other WGs
The Performance Metrics Entity SHALL work in partnership with 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, or
from the WG mailing list if it was not closed.
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
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as expert reviews are being performed by other directorates.
Existing mailing lists SHOULD be used, however a dedicated mailing
list MAY be initiated if necessary to facilitate work on a draft.
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.
6.5. Standards Track Performance Metrics
The Performance Metrics Entity will manage the progression of RFCs
along the Standards Track. See [I-D.bradner-metricstest]. 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).
6.6. Recommendations
This document recommends that the Performance Metrics Entity be
implemented as a directorate in one of the IETF Areas, providing
advice and support as described in this document to all areas in the
IETF.
7. IANA Considerations
This document makes no request of IANA.
Note to RFC EDITOR: this section may be removed on publication as an
RFC.
8. Security Considerations
In general, the existence of 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.
The security considerations that apply to any active measurement of
live networks are relevant here. See [RFC4656].
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 [RFC5475].
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9. Acknowledgements
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.
10. References
10.1. Normative References
[RFC2026] Bradner, S., "The Internet Standards Process -- Revision
3", BCP 9, RFC 2026, October 1996.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2418] Bradner, S., "IETF Working Group Guidelines and
Procedures", BCP 25, RFC 2418, September 1998.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, September 2006.
10.2. Informative References
[E.800] "ITU-T Recommendation E.800. SERIES E: OVERALL NETWORK
OPERATION, TELEPHONE SERVICE, SERVICE OPERATION AND HUMAN
FACTORS".
[G.1000] "ITU-T Recommendation G.1000. Communications Quality of
Service: A framework and definitions".
[G.107] "ITU-T Recommendation G.107. : The E-model, a
computational model for use in transmission planning.".
[I-D.bradner-metricstest]
Bradner, S. and V. Paxson, "Advancement of metrics
specifications on the IETF Standards Track",
draft-bradner-metricstest-03 (work in progress),
August 2007.
[I-D.ietf-ipfix-mediators-framework]
Kobayashi, A., Claise, B., Muenz, G., and K. Ishibashi,
"IPFIX Mediation: Framework",
draft-ietf-ipfix-mediators-framework-09 (work in
progress), October 2010.
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[P.800] "ITU-T Recommendation P.800. : Methods for subjective
determination of transmission quality".
[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330,
May 1998.
[RFC3303] Srisuresh, P., Kuthan, J., Rosenberg, J., Molitor, A., and
A. Rayhan, "Middlebox communication architecture and
framework", RFC 3303, August 2002.
[RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V.
Jacobson, "RTP: A Transport Protocol for Real-Time
Applications", STD 64, RFC 3550, July 2003.
[RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control
Protocol Extended Reports (RTCP XR)", RFC 3611,
November 2003.
[RFC4710] Siddiqui, A., Romascanu, D., and E. Golovinsky, "Real-time
Application Quality-of-Service Monitoring (RAQMON)
Framework", RFC 4710, October 2006.
[RFC5101] Claise, B., "Specification of the IP Flow Information
Export (IPFIX) Protocol for the Exchange of IP Traffic
Flow Information", RFC 5101, January 2008.
[RFC5102] Quittek, J., Bryant, S., Claise, B., Aitken, P., and J.
Meyer, "Information Model for IP Flow Information Export",
RFC 5102, January 2008.
[RFC5475] Zseby, T., Molina, M., Duffield, N., Niccolini, S., and F.
Raspall, "Sampling and Filtering Techniques for IP Packet
Selection", RFC 5475, March 2009.
[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation
Applicability Statement", RFC 5481, March 2009.
[RFC5706] Harrington, D., "Guidelines for Considering Operations and
Management of New Protocols and Protocol Extensions",
RFC 5706, November 2009.
[RFC5835] Morton, A. and S. Van den Berghe, "Framework for Metric
Composition", RFC 5835, April 2010.
[RFC6035] Pendleton, A., Clark, A., Johnston, A., and H. Sinnreich,
"Session Initiation Protocol Event Package for Voice
Quality Reporting", RFC 6035, November 2010.
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[RFC6049] Morton, A. and E. Stephan, "Spatial Composition of
Metrics", RFC 6049, January 2011.
Authors' Addresses
Alan Clark
Telchemy Incorporated
2905 Premiere Parkway, Suite 280
Duluth, Georgia 30097
USA
Phone:
Fax:
Email: alan.d.clark@telchemy.com
URI:
Benoit Claise
Cisco Systems, Inc.
De Kleetlaan 6a b1
Diegem 1831
Belgium
Phone: +32 2 704 5622
Fax:
Email: bclaise@cisco.com
URI:
Clark & Claise Expires July 17, 2011 [Page 22]
