draft-ietf-ippm-framework-compagg-07.txt   draft-ietf-ippm-framework-compagg-08.txt 
Network Working Group A. Morton, Ed. Network Working Group A. Morton, Ed.
Internet-Draft AT&T Labs Internet-Draft AT&T Labs
Intended status: Informational S. Van den Berghe, Ed. Intended status: Informational S. Van den Berghe, Ed.
Expires: May 2, 2009 Ghent University - IBBT Expires: December 23, 2009 Ghent University - IBBT
October 29, 2008 June 21, 2009
Framework for Metric Composition Framework for Metric Composition
draft-ietf-ippm-framework-compagg-07 draft-ietf-ippm-framework-compagg-08
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Abstract Abstract
This memo describes a detailed framework for composing and This memo describes a detailed framework for composing and
aggregating metrics (both in time and in space) originally defined by aggregating metrics (both in time and in space) originally defined by
the IP Performance Metrics (IPPM) RFC 2330 and developed by the IETF. the IP Performance Metrics (IPPM) RFC 2330 and developed by the IETF.
This new framework memo describes the generic composition and This new framework memo describes the generic composition and
aggregation mechanisms. The memo provides a basis for additional aggregation mechanisms. The memo provides a basis for additional
documents that implement the framework to define detailed documents that implement the framework to define detailed
compositions and aggregations of metrics which are useful in compositions and aggregations of metrics which are useful in
skipping to change at page 3, line 21 skipping to change at page 3, line 21
1.1.3. Data Reduction and Consolidation . . . . . . . . . . . 5 1.1.3. Data Reduction and Consolidation . . . . . . . . . . . 5
1.1.4. Implications on Measurement Design and Reporting . . . 6 1.1.4. Implications on Measurement Design and Reporting . . . 6
2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 6 2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 6
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Measurement Point . . . . . . . . . . . . . . . . . . . . 6 3.1. Measurement Point . . . . . . . . . . . . . . . . . . . . 6
3.2. Complete Path . . . . . . . . . . . . . . . . . . . . . . 7 3.2. Complete Path . . . . . . . . . . . . . . . . . . . . . . 7
3.3. Complete Path Metric . . . . . . . . . . . . . . . . . . . 7 3.3. Complete Path Metric . . . . . . . . . . . . . . . . . . . 7
3.4. Complete Time Interval . . . . . . . . . . . . . . . . . . 7 3.4. Complete Time Interval . . . . . . . . . . . . . . . . . . 7
3.5. Composed Metric . . . . . . . . . . . . . . . . . . . . . 7 3.5. Composed Metric . . . . . . . . . . . . . . . . . . . . . 7
3.6. Composition Function . . . . . . . . . . . . . . . . . . . 7 3.6. Composition Function . . . . . . . . . . . . . . . . . . . 7
3.7. Index . . . . . . . . . . . . . . . . . . . . . . . . . . 7 3.7. Ground Truth . . . . . . . . . . . . . . . . . . . . . . . 7
3.8. Ground Truth . . . . . . . . . . . . . . . . . . . . . . . 8 3.8. Interval . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.9. Interval . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.9. Sub-interval . . . . . . . . . . . . . . . . . . . . . . . 8
3.10. Sub-interval . . . . . . . . . . . . . . . . . . . . . . . 8 3.10. Sub-path . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.11. Sub-path . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.11. Sub-path Metrics . . . . . . . . . . . . . . . . . . . . . 8
3.12. Sub-path Metrics . . . . . . . . . . . . . . . . . . . . . 8
4. Description of Metric Types . . . . . . . . . . . . . . . . . 8 4. Description of Metric Types . . . . . . . . . . . . . . . . . 8
4.1. Temporal Aggregation Description . . . . . . . . . . . . . 8 4.1. Temporal Aggregation Description . . . . . . . . . . . . . 8
4.2. Spatial Aggregation Description . . . . . . . . . . . . . 9 4.2. Spatial Aggregation Description . . . . . . . . . . . . . 9
4.3. Spatial Composition Description . . . . . . . . . . . . . 10 4.3. Spatial Composition Description . . . . . . . . . . . . . 10
4.4. Help Metrics . . . . . . . . . . . . . . . . . . . . . . . 10 4.4. Help Metrics . . . . . . . . . . . . . . . . . . . . . . . 10
4.5. Higher Order Composition . . . . . . . . . . . . . . . . . 10 4.5. Higher Order Composition . . . . . . . . . . . . . . . . . 10
5. Requirements for Composed Metrics . . . . . . . . . . . . . . 11 5. Requirements for Composed Metrics . . . . . . . . . . . . . . 11
5.1. Note on IPR . . . . . . . . . . . . . . . . . . . . . . . 12
6. Guidelines for Defining Composed Metrics . . . . . . . . . . . 12 6. Guidelines for Defining Composed Metrics . . . . . . . . . . . 12
6.1. Ground Truth: Comparison with other IPPM Metrics . . . . . 12 6.1. Ground Truth: Comparison with other IPPM Metrics . . . . . 12
6.1.1. Ground Truth for Temporal Aggregation . . . . . . . . 14 6.1.1. Ground Truth for Temporal Aggregation . . . . . . . . 14
6.1.2. Ground Truth for Spatial Aggregation . . . . . . . . . 14 6.1.2. Ground Truth for Spatial Aggregation . . . . . . . . . 15
6.2. Deviation from the Ground Truth . . . . . . . . . . . . . 14 6.2. Deviation from the Ground Truth . . . . . . . . . . . . . 15
6.3. Incomplete Information . . . . . . . . . . . . . . . . . . 15 6.3. Incomplete Information . . . . . . . . . . . . . . . . . . 15
6.4. Time Varying Metrics . . . . . . . . . . . . . . . . . . . 15 6.4. Time Varying Metrics . . . . . . . . . . . . . . . . . . . 15
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 16
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
10.1. Normative References . . . . . . . . . . . . . . . . . . . 16 10.1. Normative References . . . . . . . . . . . . . . . . . . . 16
10.2. Informative References . . . . . . . . . . . . . . . . . . 16 10.2. Informative References . . . . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 16 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17
Intellectual Property and Copyright Statements . . . . . . . . . . 18
1. Introduction 1. Introduction
The IPPM framework [RFC2330] describes two forms of metric The IPPM framework [RFC2330] describes two forms of metric
composition, spatial and temporal. The text also suggests that the composition, spatial and temporal. The text also suggests that the
concepts of the analytical framework (or A-frame) would help to concepts of the analytical framework (or A-frame) would help to
develop useful relationships to derive the composed metrics from real develop useful relationships to derive the composed metrics from real
metrics. The effectiveness of composed metrics is dependent on their metrics. The effectiveness of composed metrics is dependent on their
usefulness in analysis and applicability to practical measurement usefulness in analysis and applicability to practical measurement
circumstances. circumstances.
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function (e.g., a composition function). The process may use metrics function (e.g., a composition function). The process may use metrics
that are identical to the metric being composed, or metrics that are that are identical to the metric being composed, or metrics that are
dissimilar, or some combination of both types. dissimilar, or some combination of both types.
3.6. Composition Function 3.6. Composition Function
A composition function is a deterministic process applied to A composition function is a deterministic process applied to
individual metrics to derive another metric (such as a Composed individual metrics to derive another metric (such as a Composed
metric). metric).
3.7. Index 3.7. Ground Truth
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. The deterministic
function for an index is often developed after the index range and
index behavior have been determined. Examples include the Effective
Equipment Impairment Factor as described in section 3.5 of ITU-T
Recommendation [G.107].
>>> Comment: Perhaps the definition of an Index should move to the
PMOL Framework?
3.8. Ground Truth
As applied here, the notion of ground truth is defined as the actual As applied here, the notion of ground truth is defined as the actual
performance of a network path over some time interval. The ground performance of a network path over some time interval. The ground
truth is a metric on the (unavailable) packet transfer information truth is a metric on the (unavailable) packet transfer information
for the desired path and time interval that a composed metric seeks for the desired path and time interval that a composed metric seeks
to estimate. to estimate.
3.9. Interval 3.8. Interval
A span of time. A span of time.
3.10. Sub-interval 3.9. Sub-interval
A Sub-interval is a time interval that is included in another A Sub-interval is a time interval that is included in another
interval. interval.
3.11. Sub-path 3.10. Sub-path
A Sub-path is a portion of the complete path where at least the Sub- A Sub-path is a portion of the complete path where at least the Sub-
path Source and Destination hosts are constituents of the complete path Source and Destination hosts are constituents of the complete
path. We say that this sub-path is "involved" in the complete path. path. We say that such a sub-path is "involved" in the complete
path.
3.12. Sub-path Metrics Since sub-paths terminate on hosts, it is important to describe how
sub-paths are considered to be joined. In practice, the Source and
Desitination hosts may perform the funtion of measurement points.
If the Destination and Source hosts of two adjoining paths are co-
located and the link between them would contribute negligible
performance, then these hosts can be considered equivalent (even if
there is no physical link between them, this is a practical
consession).
If the Destination and Source hosts of two adjoining paths have a
link between them that contributes to the complete path performance,
then the link and hosts constitutes another sub-path that is involved
in the complete path, and should be characterized and included in the
composed metric.
3.11. Sub-path Metrics
A sub-path path metric is an element of the process to derive a A sub-path path metric is an element of the process to derive a
Composite metric, quantifying some aspect of the performance a Composite metric, quantifying some aspect of the performance a
particular sub-path from its Source to Destination. particular sub-path from its Source to Destination.
4. Description of Metric Types 4. Description of Metric Types
This section defines the various classes of Composition. There are This section defines the various classes of Composition. There are
two classes more accurately described as aggregation over time and two classes more accurately described as aggregation over time and
space, and the third involves concatenation in space. space, and the third involves concatenation in space.
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4.5. Higher Order Composition 4.5. Higher Order Composition
Composed metrics might themselves be subject to further steps of Composed metrics might themselves be subject to further steps of
composition or aggregation. An example would be the delay of a composition or aggregation. An example would be the delay of a
maximal path obtained through the spatial composition of several maximal path obtained through the spatial composition of several
composed delays for each Complete Path in the maximal path (obtained composed delays for each Complete Path in the maximal path (obtained
through spatial composition). All requirements for first order through spatial composition). All requirements for first order
composition metrics apply to higher order composition. composition metrics apply to higher order composition.
An example using temporal aggregation: twelve 5-minute metrics are An example using temporal aggregation: twelve 5-minute metrics are
aggregated to estimate the performance over an hour. The seconds aggregated to estimate the performance over an hour. The second step
step of aggregation would take 24 hourly metrics and estimate the of aggregation would take 24 hourly metrics and estimate the
performance over a day. performance over a day.
5. Requirements for Composed Metrics 5. Requirements for Composed Metrics
The definitions for all composed metrics MUST include sections to The definitions for all composed metrics MUST include sections to
treat the following topics. treat the following topics.
The description of each metric will clearly state: The description of each metric will clearly state:
1. the definition (and statistic, where appropriate); 1. the definition (and statistic, where appropriate);
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o Requires precisely synchronized measurement time intervals in all o Requires precisely synchronized measurement time intervals in all
component metrics, or loosely synchronized, or no timing component metrics, or loosely synchronized, or no timing
requirements. requirements.
o Requires assumption of component metric independence w.r.t. the o Requires assumption of component metric independence w.r.t. the
metric being defined/composed, or other assumptions. metric being defined/composed, or other assumptions.
o Has known sources of inaccuracy/error, and identifies the sources. o Has known sources of inaccuracy/error, and identifies the sources.
5.1. Note on IPR
If one or more components of the composition process are encumbered If one or more components of the composition process are encumbered
by Intellectual Property Rights (IPR), then the resulting Composed by Intellectual Property Rights (IPR), then the resulting Composed
Metrics may be encumbered as well. See BCP 79 [RFC3979] for IETF Metrics may be encumbered as well. See BCP 79 [RFC3979] for IETF
policies on IPR disclosure. policies on IPR disclosure.
6. Guidelines for Defining Composed Metrics 6. Guidelines for Defining Composed Metrics
6.1. Ground Truth: Comparison with other IPPM Metrics 6.1. Ground Truth: Comparison with other IPPM Metrics
Figure 1 illustrates the process to derive a metric using spatial Figure 1 illustrates the process to derive a metric using spatial
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(Composed-Rcvr1, Composed-Rcvr2, Composed-Rcvr3) (Composed-Rcvr1, Composed-Rcvr2, Composed-Rcvr3)
The "Ground Truth" for this composed metric is of course an actual The "Ground Truth" for this composed metric is of course an actual
One-to-Group metric, where a single source packet has been measured One-to-Group metric, where a single source packet has been measured
after traversing the Complete Paths to the various receivers. after traversing the Complete Paths to the various receivers.
6.1.1. Ground Truth for Temporal Aggregation 6.1.1. Ground Truth for Temporal Aggregation
Temporal Aggregation involves measurements made over sub-intervals of Temporal Aggregation involves measurements made over sub-intervals of
the desired test interval between the same Source and Destination. the complete time interval between the same Source and Destination.
Therefore, the "Ground Truth" is the metric measured over the desired Therefore, the "Ground Truth" is the metric measured over the desired
interval. interval.
6.1.2. Ground Truth for Spatial Aggregation 6.1.2. Ground Truth for Spatial Aggregation
Spatial Aggregation combines many measurements using a weighting Spatial Aggregation combines many measurements using a weighting
function to provide the same emphasis as though the measurements were function to provide the same emphasis as though the measurements were
based on actual traffic, with inherent weights. Therefore, the based on actual traffic, with inherent weights. Therefore, the
"Ground Truth" is the metric measured on the actual traffic instead "Ground Truth" is the metric measured on the actual traffic instead
of the active streams that sample the performance. of the active streams that sample the performance.
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A metric composition can deviate from the ground truth for several A metric composition can deviate from the ground truth for several
reasons. Two main aspects are: reasons. Two main aspects are:
o The propagation of the inaccuracies of the underlying measurements o The propagation of the inaccuracies of the underlying measurements
when composing the metric. As part of the composition function, when composing the metric. As part of the composition function,
errors of measurements might propagate. Where possible, this errors of measurements might propagate. Where possible, this
analysis should be made and included with the description of each analysis should be made and included with the description of each
metric. metric.
o A difference in scope. When concatenating hop-by-hop active o A difference in scope. When concatenating many active measurement
measurement results to obtain the end-to-end metric, the actual results (from two or more sub-paths) to obtain the complete path
measured path will not be identical to the end-to-end path. It is metric, the actual measured path will not be identical to the
in general difficult to quantify this deviation, but a metric complete path. It is in general difficult to quantify this
definition might identify guidelines for keeping the deviation as deviation with exactness, but a metric definition might identify
small as possible. guidelines for keeping the deviation as small as possible.
The description of the metric composition MUST include an section The description of the metric composition MUST include an section
identifying the deviation from the ground truth. identifying the deviation from the ground truth.
6.3. Incomplete Information 6.3. Incomplete Information
In practice, when measurements cannot be initiated on a sub-path or In practice, when measurements cannot be initiated on a sub-path or
during a particular measurement interval (and perhaps the measurement during a particular measurement interval (and perhaps the measurement
system gives up during the test interval), then there will not be a system gives up during the test interval), then there will not be a
value for the sub-path reported, and the result SHOULD be recorded as value for the sub-path reported, and the result SHOULD be recorded as
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7. IANA Considerations 7. IANA Considerations
This document makes no request of IANA. This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an Note to RFC Editor: this section may be removed on publication as an
RFC. RFC.
8. Security Considerations 8. Security Considerations
The security considerations that apply to any active measurement of The security considerations that apply to any active measurement of
live networks are relevant here as well. See [RFC4656]. live networks are relevant here as well. See [RFC4656], and
[RFC5357].
The exchange of sub-path measurements among network providers may be
a source of concern, and the information should be sufficiently
anonymized to avoid revealing unnecessary operational details (e.g.,
the network addresses of measurement devices). However, the schema
for measurement exchange is beyond the scope of this memo, and likely
to be covered by bilateral agreements for some time to come.
9. Acknowledgements 9. Acknowledgements
The authors would like to thank Maurizio Molina, Andy Van Maele, The authors would like to thank Maurizio Molina, Andy Van Maele,
Andreas Haneman, Igor Velimirovic, Andreas Solberg, Athanassios Andreas Haneman, Igor Velimirovic, Andreas Solberg, Athanassios
Liakopulos, David Schitz, Nicolas Simar and the Geant2 Project. We Liakopulos, David Schitz, Nicolas Simar and the Geant2 Project. We
also acknowledge comments and suggestions from Phil Chimento, Emile also acknowledge comments and suggestions from Phil Chimento, Emile
Stephan, Lei Liang, Stephen Wolff, Reza Fardid, Loki Jorgenson, and Stephan, Lei Liang, Stephen Wolff, Reza Fardid, Loki Jorgenson, and
Alan Clark. Alan Clark.
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.ietf-ippm-multimetrics] [I-D.ietf-ippm-multimetrics]
Stephan, E., Liang, L., and A. Morton, "IP Performance Stephan, E., Liang, L., and A. Morton, "IP Performance
Metrics (IPPM) for spatial and multicast", Metrics (IPPM) for spatial and multicast",
draft-ietf-ippm-multimetrics-09 (work in progress), draft-ietf-ippm-multimetrics-11 (work in progress),
October 2008. April 2009.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330, "Framework for IP Performance Metrics", RFC 2330,
May 1998. May 1998.
[RFC3979] Bradner, S., "Intellectual Property Rights in IETF [RFC3979] Bradner, S., "Intellectual Property Rights in IETF
Technology", BCP 79, RFC 3979, March 2005. Technology", BCP 79, RFC 3979, March 2005.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. [RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, September 2006. (OWAMP)", RFC 4656, September 2006.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, October 2008.
10.2. Informative References 10.2. Informative References
[G.107] ITU-T Recommendation G.107, ""The E-model, a computational [G.107] ITU-T Recommendation G.107, ""The E-model, a computational
model for use in transmission planning"", March 2005. model for use in transmission planning"", March 2005.
Authors' Addresses Authors' Addresses
Al Morton (editor) Al Morton (editor)
AT&T Labs AT&T Labs
200 Laurel Avenue South 200 Laurel Avenue South
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Al Morton (editor) Al Morton (editor)
AT&T Labs AT&T Labs
200 Laurel Avenue South 200 Laurel Avenue South
Middletown,, NJ 07748 Middletown,, NJ 07748
USA USA
Phone: +1 732 420 1571 Phone: +1 732 420 1571
Fax: +1 732 368 1192 Fax: +1 732 368 1192
Email: acmorton@att.com Email: acmorton@att.com
URI: http://home.comcast.net/~acmacm/ URI: http://home.comcast.net/~acmacm/
Steven Van den Berghe (editor) Steven Van den Berghe (editor)
Ghent University - IBBT Ghent University - IBBT
G. Crommenlaan 8 bus 201 G. Crommenlaan 8 bus 201
Gent 9050 Gent 9050
Belgium Belgium
Phone: +32 9 331 49 73 Phone: +32 9 331 49 73
Email: steven.vandenberghe@intec.ugent.be Email: steven.vandenberghe@intec.ugent.be
URI: http://www.ibcn.intec.ugent.be URI: http://www.ibcn.intec.ugent.be
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