draft-ietf-ippm-framework-compagg-02.txt   draft-ietf-ippm-framework-compagg-03.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: April 25, 2007 Ghent University - IBBT Expires: September 5, 2007 Ghent University - IBBT
October 22, 2006 March 4, 2007
Framework for Metric Composition Framework for Metric Composition
draft-ietf-ippm-framework-compagg-01 draft-ietf-ippm-framework-compagg-03
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
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This Internet-Draft will expire on April 25, 2007. This Internet-Draft will expire on September 5, 2007.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2006). Copyright (C) The IETF Trust (2007).
Abstract Abstract
This memo describes a framework for composing and aggregating metrics This memo describes a framework for composing and aggregating metrics
(both in time and in space) defined by RFC 2330 and developed by the (both in time and in space) defined by RFC 2330 and developed by the
IPPM working group. The framework describes the generic composition IPPM working group. The framework describes the generic composition
and aggregation mechanisms. It provides a basis for additional and aggregation mechanisms. It provides a basis for additional
documents that implement this framework for detailed, and practically documents that implement this framework for detailed, and practically
useful, compositions and aggregations of metrics. useful, compositions and aggregations of metrics.
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4.2. Spatial Aggregation Description . . . . . . . . . . . . . 7 4.2. Spatial Aggregation Description . . . . . . . . . . . . . 7
4.3. Spatial Composition Description . . . . . . . . . . . . . 8 4.3. Spatial Composition Description . . . . . . . . . . . . . 8
4.4. Help Metrics . . . . . . . . . . . . . . . . . . . . . . . 8 4.4. Help Metrics . . . . . . . . . . . . . . . . . . . . . . . 8
4.5. Higher Order Composition . . . . . . . . . . . . . . . . . 9 4.5. Higher Order Composition . . . . . . . . . . . . . . . . . 9
5. Requirements for Composed Metrics . . . . . . . . . . . . . . 9 5. Requirements for Composed Metrics . . . . . . . . . . . . . . 9
6. Guidelines for Defining Composed Metrics . . . . . . . . . . . 10 6. Guidelines for Defining Composed Metrics . . . . . . . . . . . 10
6.1. Ground Truth: Comparison with other IPPM Metrics . . . . . 10 6.1. Ground Truth: Comparison with other IPPM Metrics . . . . . 10
6.1.1. Ground Truth for Temporal Aggregation . . . . . . . . 12 6.1.1. Ground Truth for Temporal Aggregation . . . . . . . . 12
6.1.2. Ground Truth for Spatial Aggregation . . . . . . . . . 13 6.1.2. Ground Truth for Spatial Aggregation . . . . . . . . . 13
6.2. Deviation from the Ground Truth . . . . . . . . . . . . . 13 6.2. Deviation from the Ground Truth . . . . . . . . . . . . . 13
6.3. Incomplete Information . . . . . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13 8. Security Considerations . . . . . . . . . . . . . . . . . . . 14
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14
10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
10.1. Normative References . . . . . . . . . . . . . . . . . . . 14 10.1. Normative References . . . . . . . . . . . . . . . . . . . 14
10.2. Informative References . . . . . . . . . . . . . . . . . . 14 10.2. Informative References . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
Intellectual Property and Copyright Statements . . . . . . . . . . 16 Intellectual Property and Copyright Statements . . . . . . . . . . 16
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. Also, the text suggests that the composition, spatial and temporal. Also, the text suggests that the
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considered more critical than others. considered more critical than others.
Metric composition can help to provide, from raw measurement data, Metric composition can help to provide, from raw measurement data,
some tangible, well-understood and agreed upon information about the some tangible, well-understood and agreed upon information about the
service guarantees provided by a network. Such information can be service guarantees provided by a network. Such information can be
used in the Service Level Agreement/Service Level Specification (SLA/ used in the Service Level Agreement/Service Level Specification (SLA/
SLS) contracts between a service provider and its customers. SLS) contracts between a service provider and its customers.
1.1.4. Implications on Measurement Design and Reporting 1.1.4. Implications on Measurement Design and Reporting
If a network operator can anticipate needing to aggregate or compose If a network measurement system operator anticipates needing to
overall metrics in the future, it is more efficient to start by produce overall metrics by composition, then it is prudent to keep
considering the tenants of these methods in the measurement design/ that requirement in mind when considering the measurement design and
sampling plan, and reporting the results. The Summary Statistics of sampling plan. Also, certain summary statistics are more conducive
certain metrics are more conducive to composition than others. This to composition than others, and this figures prominently in the
figures prominently in the design of measurements and the results design of measurements and when reporting the results.
reports.
2. Purpose and Scope 2. Purpose and Scope
The purpose of this memo is provide a common framework for the The purpose of this memo is provide a common framework for the
various classes of metrics based on composition of primary metrics. various classes of metrics based on composition of primary metrics.
The scope is limited to the definitions of metrics that are composed The scope is limited to the definitions of metrics that are composed
from primary metrics using a deterministic function. Key information from primary metrics using a deterministic function. Key information
about each metric, such as its assumptions under which the about each metric, such as its assumptions under which the
relationship holds, and possible sources of error/circumstances where relationship holds, and possible sources of error/circumstances where
the composition may fail, are included. the composition may fail, are included.
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traverses from the packet's Source to its Destination. traverses from the packet's Source to its Destination.
3.3. Complete path metric 3.3. Complete path metric
The complete path metric is the Source to Destination metric that a The complete path metric is the Source to Destination metric that a
composed metric is estimating. A complete path metric represents the composed metric is estimating. A complete path metric represents the
ground-truth for a composed metric. ground-truth for a composed metric.
3.4. Composed Metric 3.4. Composed Metric
A composed metric is derived from other metrics principally by A composed metric is an estimate of an actual metric describing the
applying a composition function. performance of a path over some time interval. A composed metric is
derived from other metrics by applying a deterministic process or
function (e.g., a composition function).
3.5. Composition Function 3.5. Composition Function
A composition function is a deterministic process applied to Sub-path A composition function is a deterministic process applied to
metrics to derive another metric (such as a Composed metric). individual metrics to derive another metric (such as a Composed
metric).
3.6. Ground Truth 3.6. 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 entity over some time interval. The ground performance of a network path over some time interval. The ground
truth is the (unavailable) measurement that a composed metric seeks truth is metric based on the (unavailable) measurement that a
to estimate. composed metric seeks to estimate.
3.7. Sub-interval 3.7. 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.
3.8. Sub-path 3.8. 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
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3.9. Sub-path metrics 3.9. 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 referred to as aggregation over time and two classes more accurately described as aggregation over time and
space, and the third is simply composition in space. space, and the third involves concatenation in space.
4.1. Temporal Aggregation Description 4.1. Temporal Aggregation Description
Aggregation in time is defined as the composition of metrics with the Aggregation in time is defined as the composition of metrics with the
same type and scope obtained in different time instants or time same type and scope obtained in different time instants or time
windows. For example, starting from a time series of One-Way Delay windows. For example, starting from a time series of the
measurements on a certain network path obtained in 5-minute periods measurements of maximum and minimum One-Way Delay on a certain
and averaging groups of 12 consecutive values, we obtain a time network path obtained over 5-minute intervals, we obtain a time
series measurement with a coarser resolution (60 minutes). The main series measurement with a coarser resolution (60 minutes) by taking
reason for doing time aggregation is to reduce the amount of data the max of 12 consecutive 5-minute maxima and the min of 12
that has to be stored, and make the visualization/spotting of regular consecutive 5-minute minima.
cycles and/or growing or decreasing trends easier. Another useful
application is to detect anomalies or abnormal changes in the network The main reason for doing time aggregation is to reduce the amount of
characteristics. data that has to be stored, and make the visualization/spotting of
regular cycles and/or growing or decreasing trends easier. Another
useful application is to detect anomalies or abnormal changes in the
network characteristics.
In RFC 2330, the term "temporal composition" is introduced and In RFC 2330, the term "temporal composition" is introduced and
differs from temporal aggregation in that it refers to methodologies differs from temporal aggregation in that it refers to methodologies
to predict future metrics on the basis of past observations, to predict future metrics on the basis of past observations,
exploiting the time correlation that certain metrics can exhibit. We exploiting the time correlation that certain metrics can exhibit. We
do not consider this type of composition here. do not consider this type of composition here.
>>>>>>>>Comment: Why no forecasting? This was apparently a limit on >>>>>>>>Comment: Why no forecasting? This was apparently a limit on
the Geant2 project, but may not apply here. the Geant2 project, but may not apply here.
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o A difference in scope. When concatenating hop-by-hop active o A difference in scope. When concatenating hop-by-hop active
measurement results to obtain the end-to-end metric, the actual measurement results to obtain the end-to-end metric, the actual
measured path will not be identical to the end-to-end path. It is measured path will not be identical to the end-to-end path. It is
in general difficult to quantify this deviation, but a metric in general difficult to quantify this deviation, but a metric
definition might identify guidelines for keeping the deviation as definition might identify guidelines for keeping the deviation as
small as possible. 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
In practice, when measurements cannot be initiated on a sub-path or
during a particular measurement interval (and perhaps the measurement
system gives up during the test interval), then there will not be a
value for the subpath reported, and the result SHOULD be recorded as
"undefined".
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].
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 and Lei Liang. Stephan, Lei Liang, and Stephen Wolff.
10. References 10. References
10.1. Normative References 10.1. Normative References
[I-D.ietf-ippm-multimetrics] [I-D.ietf-ippm-multimetrics]
Stephan, E., "IP Performance Metrics (IPPM) for spatial Stephan, E., "IP Performance Metrics (IPPM) for spatial
and multicast", draft-ietf-ippm-multimetrics-01 (work in and multicast", draft-ietf-ippm-multimetrics-02 (work in
progress), July 2006. progress), October 2006.
[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.
[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
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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
Full Copyright Statement Full Copyright Statement
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