draft-ietf-ippm-spatial-composition-00.txt   draft-ietf-ippm-spatial-composition-01.txt 
Network Working Group A. Morton Network Working Group A. Morton
Internet-Draft AT&T Labs Internet-Draft AT&T Labs
Expires: August 30, 2006 E. Stephan Expires: December 26, 2006 E. Stephan
France Telecom Division R&D France Telecom Division R&D
February 26, 2006 June 24, 2006
Spatial Composition of Metrics Spatial Composition of Metrics
draft-ietf-ippm-spatial-composition-00 draft-ietf-ippm-spatial-composition-01
Status of this Memo Status of this Memo
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This Internet-Draft will expire on August 30, 2006. This Internet-Draft will expire on December 26, 2006.
Copyright Notice Copyright Notice
Copyright (C) The Internet Society (2006). Copyright (C) The Internet Society (2006).
Abstract Abstract
This memo utilizes IPPM metrics that are applicable to both complete This memo utilizes IPPM metrics that are applicable to both complete
paths and sub-paths, and defines relationships to compose a complete paths and sub-paths, and defines relationships to compose a complete
path metric from the sub-path metrics with some accuracy w.r.t. the path metric from the sub-path metrics with some accuracy w.r.t. the
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Table of Contents Table of Contents
1. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 5 2.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Scope, Application, and Terminology . . . . . . . . . . . . . 5 3. Scope, Application, and Terminology . . . . . . . . . . . . . 5
3.1. Scope of work . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Scope of work . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Application . . . . . . . . . . . . . . . . . . . . . . . 6 3.2. Application . . . . . . . . . . . . . . . . . . . . . . . 6
3.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 3.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
4. One-way Delay Composition Metrics and Statistics . . . . . . . 7 4. One-way Delay Composed Metrics and Statistics . . . . . . . . 7
4.1. Name: 4.1. Name:
Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream . . . 7 Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream . . . 7
4.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 7 4.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 7
4.1.2. Definition and Metric Units . . . . . . . . . . . . . 8 4.1.2. Definition and Metric Units . . . . . . . . . . . . . 8
4.1.3. Discussion and other details . . . . . . . . . . . . . 8 4.1.3. Discussion and other details . . . . . . . . . . . . . 8
4.1.4. Mean Statistic . . . . . . . . . . . . . . . . . . . . 8 4.1.4. Mean Statistic . . . . . . . . . . . . . . . . . . . . 9
4.1.5. Composition Relationship: Sum of Means . . . . . . . . 9 4.1.5. Composition Function: Sum of Means . . . . . . . . . . 9
4.1.6. Statement of Conjecture . . . . . . . . . . . . . . . 9 4.1.6. Statement of Conjecture . . . . . . . . . . . . . . . 9
4.1.7. Justification of Composite Relationship . . . . . . . 9 4.1.7. Justification of the Composition Function . . . . . . 10
4.1.8. Sources of Error . . . . . . . . . . . . . . . . . . . 10 4.1.8. Sources of Deviation from the Ground Truth . . . . . . 10
4.1.9. Specific cases where the conjecture might fail . . . . 10 4.1.9. Specific cases where the conjecture might fail . . . . 10
4.1.10. Application of Measurement Methodology . . . . . . . . 10 4.1.10. Application of Measurement Methodology . . . . . . . . 10
5. Loss Metrics and Statistics . . . . . . . . . . . . . . . . . 11 5. Loss Metrics and Statistics . . . . . . . . . . . . . . . . . 11
5.1. Name: 5.1. Name:
Type-P-One-way-Packet-Loss-Poisson/Periodic-Stream . . . . 11 Type-P-One-way-Packet-Loss-Poisson/Periodic-Stream . . . . 11
5.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 11 5.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 11
5.1.2. Definition and Metric Units . . . . . . . . . . . . . 11 5.1.2. Definition and Metric Units . . . . . . . . . . . . . 11
5.1.3. Discussion and other details . . . . . . . . . . . . . 11 5.1.3. Discussion and other details . . . . . . . . . . . . . 11
5.1.4. Statistic: 5.1.4. Statistic:
Type-P-One-way-Packet-Loss-Empirical-Probability . . . 11 Type-P-One-way-Packet-Loss-Empirical-Probability . . . 11
5.1.5. Composition Relationship: Composition of Empirical 5.1.5. Composition Function: Composition of Empirical
Probabilities . . . . . . . . . . . . . . . . . . . . 11 Probabilities . . . . . . . . . . . . . . . . . . . . 12
5.1.6. Statement of Conjecture . . . . . . . . . . . . . . . 12 5.1.6. Statement of Conjecture . . . . . . . . . . . . . . . 12
5.1.7. Justification of Composite Relationship . . . . . . . 12 5.1.7. Justification of the Composition Function . . . . . . 12
5.1.8. Sources of Error . . . . . . . . . . . . . . . . . . . 12 5.1.8. Sources of Deviation from the Ground Truth . . . . . . 12
5.1.9. Specific cases where the conjecture might fail . . . . 12 5.1.9. Specific cases where the conjecture might fail . . . . 13
5.1.10. Application of Measurement Methodology . . . . . . . . 13 5.1.10. Application of Measurement Methodology . . . . . . . . 13
6. Delay Variation Metrics and Statistics . . . . . . . . . . . . 13 6. Delay Variation Metrics and Statistics . . . . . . . . . . . . 13
6.1. Name: 6.1. Name:
Type-P-One-way-ipdv-refmin-Poisson/Periodic-Stream . . . . 13 Type-P-One-way-ipdv-refmin-Poisson/Periodic-Stream . . . . 14
6.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 13 6.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 14
6.1.2. Definition and Metric Units . . . . . . . . . . . . . 14 6.1.2. Definition and Metric Units . . . . . . . . . . . . . 14
6.1.3. Discussion and other details . . . . . . . . . . . . . 14 6.1.3. Discussion and other details . . . . . . . . . . . . . 15
6.1.4. Statistics: Mean, Variance, Skewness, Quanitle . . . . 14 6.1.4. Statistics: Mean, Variance, Skewness, Quanitle . . . . 15
6.1.5. Composition Relationships: . . . . . . . . . . . . . . 15 6.1.5. Composition Functions: . . . . . . . . . . . . . . . . 16
6.1.6. Statement of Conjecture . . . . . . . . . . . . . . . 16 6.1.6. Statement of Conjecture . . . . . . . . . . . . . . . 16
6.1.7. Justification of Composite Relationship . . . . . . . 16 6.1.7. Justification of the Composition Function . . . . . . 16
6.1.8. Sources of Error . . . . . . . . . . . . . . . . . . . 16 6.1.8. Sources of Deviation from the Ground Truth . . . . . . 16
6.1.9. Specific cases where the conjecture might fail . . . . 16 6.1.9. Specific cases where the conjecture might fail . . . . 16
6.1.10. Application of Measurement Methodology . . . . . . . . 16 6.1.10. Application of Measurement Methodology . . . . . . . . 16
7. Other Metrics and Statistics: One-way Combined Metric . . . . 16 7. Other Metrics and Statistics: One-way Combined Metric . . . . 16
7.1. Metric Name: . . . . . . . . . . . . . . . . . . . . . . . 16 7.1. Metric Name: . . . . . . . . . . . . . . . . . . . . . . . 16
7.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 16 7.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 16
7.1.2. Definition and Metric Units . . . . . . . . . . . . . 16 7.1.2. Definition and Metric Units . . . . . . . . . . . . . 17
7.1.3. Discussion and other details . . . . . . . . . . . . . 17 7.1.3. Discussion and other details . . . . . . . . . . . . . 17
7.1.4. Type-P-One-way-Combo-subpathes-stream . . . . . . . . 17 7.1.4. Type-P-One-way-Combo-subpathes-stream . . . . . . . . 17
7.1.5. Type-P-One-way-composition . . . . . . . . . . . . . . 17 7.1.5. Type-P-One-way-composition . . . . . . . . . . . . . . 18
7.1.6. Type-P-One-way-composition . . . . . . . . . . . . . . 17 7.1.6. Type-P-One-way-composition . . . . . . . . . . . . . . 18
7.1.7. Statement of Conjecture . . . . . . . . . . . . . . . 18 7.1.7. Statement of Conjecture . . . . . . . . . . . . . . . 18
7.1.8. Justification of Composite Relationship . . . . . . . 18 7.1.8. Justification of Composite Relationship . . . . . . . 18
7.1.9. Sources of Error . . . . . . . . . . . . . . . . . . . 18 7.1.9. Sources of Error . . . . . . . . . . . . . . . . . . . 19
7.1.10. Specific cases where the conjecture might fail . . . . 18 7.1.10. Specific cases where the conjecture might fail . . . . 19
7.1.11. Application of Measurement Methodology . . . . . . . . 18 7.1.11. Application of Measurement Methodology . . . . . . . . 19
8. Security Considerations . . . . . . . . . . . . . . . . . . . 19 8. Security Considerations . . . . . . . . . . . . . . . . . . . 19
8.1. Denial of Service Attacks . . . . . . . . . . . . . . . . 19 8.1. Denial of Service Attacks . . . . . . . . . . . . . . . . 19
8.2. User Data Confidentiality . . . . . . . . . . . . . . . . 19 8.2. User Data Confidentiality . . . . . . . . . . . . . . . . 19
8.3. Interference with the metrics . . . . . . . . . . . . . . 19 8.3. Interference with the metrics . . . . . . . . . . . . . . 20
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20
10. Security Considerations . . . . . . . . . . . . . . . . . . . 20 10. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 20
11. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 20 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21 12.1. Normative References . . . . . . . . . . . . . . . . . . . 21
13.1. Normative References . . . . . . . . . . . . . . . . . . . 21 12.2. Informative References . . . . . . . . . . . . . . . . . . 22
13.2. Informative References . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22 Intellectual Property and Copyright Statements . . . . . . . . . . 24
Intellectual Property and Copyright Statements . . . . . . . . . . 23
1. Contributors 1. Contributors
Thus far, the following people have contributed useful ideas, Thus far, the following people have contributed useful ideas,
suggestions, or the text of sections that have been incorporated into suggestions, or the text of sections that have been incorporated into
this memo: this memo:
- Phil Chimento <vze275m9@verizon.net> - Phil Chimento <vze275m9@verizon.net>
- Reza Fardid <RFardid@Covad.COM> - Reza Fardid <RFardid@Covad.COM>
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- Al Morton <acmorton@att.com> - Al Morton <acmorton@att.com>
- Emile Stephan <emile.stephan@francetelecom.com> - Emile Stephan <emile.stephan@francetelecom.com>
- Lei Liang <L.Liang@surrey.ac.uk> - Lei Liang <L.Liang@surrey.ac.uk>
2. Introduction 2. Introduction
The IPPM framework RFC 2330 [RFC2330] describes two forms of metric The IPPM framework RFC 2330 [RFC2330] describes two forms of metric
composition, spatial and temporal. The new composition framework composition, spatial and temporal. The new composition framework
[FRMWK] expands and further qualifies these original forms into three [I-D.ietf-ippm-framework-compagg] expands and further qualifies these
categories. This memo describes Spatial Composition, one of the original forms into three categories. This memo describes Spatial
categories of metrics under the umbrella of the composition Composition, one of the categories of metrics under the umbrella of
framework. the composition framework.
Spatial composition encompasses the definition of performance metrics Spatial composition encompasses the definition of performance metrics
that are applicable to a complete path, based on metrics collected on that are applicable to a complete path, based on metrics collected on
various sub-paths. various sub-paths.
The purpose of this memo is to define relationships that yield the The main purpose of this memo is to define the deterministic
complete path metrics using metrics of the sub-paths. The functions that yield the complete path metrics using metrics of the
effectiveness of such metrics is dependent on their usefulness in sub-paths. The effectiveness of such metrics is dependent on their
analysis and applicability with practical measurement methods. usefulness in analysis and applicability with practical measurement
methods.
The relationships may involve conjecture, and [RFC2330] lists four The relationships may involve conjecture, and [RFC2330] lists four
points that the metric definitions should include: points that the metric definitions should include:
o the specific conjecture applied to the metric, o the specific conjecture applied to the metric,
o a justification of the practical utility of the composition in o a justification of the practical utility of the composition in
terms of making accurate measurements of the metric on the path, terms of making accurate measurements of the metric on the path,
o a justification of the usefulness of the composition in terms of o a justification of the usefulness of the composition in terms of
making analysis of the path using A-frame concepts more effective, making analysis of the path using A-frame concepts more effective,
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o an analysis of how the conjecture could be incorrect. o an analysis of how the conjecture could be incorrect.
RFC 2330 also gives an example where a conjecture that the delay of a RFC 2330 also gives an example where a conjecture that the delay of a
path is very nearly the sum of the delays of the exchanges and clouds path is very nearly the sum of the delays of the exchanges and clouds
of the corresponding path digest. This example is particularly of the corresponding path digest. This example is particularly
relevant to those who wish to assess the performance of an Inter- relevant to those who wish to assess the performance of an Inter-
domain path without direct measurement, and the performance estimate domain path without direct measurement, and the performance estimate
of the complete path is related to the measured results for various of the complete path is related to the measured results for various
sub-paths instead. sub-paths instead.
Approximate relationships between the sub-path and complete path Approximate functions between the sub-path and complete path metrics
metrics are useful, with knowledge of the circumstances where the are useful, with knowledge of the circumstances where the
relationships are/are not applicable. For example, we would not relationships are/are not applicable. For example, we would not
expect that delay singletons from each sub-path would sum to produce expect that delay singletons from each sub-path would sum to produce
an accurate estimate of a delay singleton for the complete path an accurate estimate of a delay singleton for the complete path
(unless all the delays were essentially constant - very unlikely). (unless all the delays were essentially constant - very unlikely).
However, other delay statistics (based on a reasonable sample size) However, other delay statistics (based on a reasonable sample size)
may have a sufficiently large set of circumstances where they are may have a sufficiently large set of circumstances where they are
applicable. applicable.
2.1. Motivation 2.1. Motivation
One-way metrics defined in other IPPM RFCs all assume that the One-way metrics defined in other IPPM RFCs all assume that the
measurement can be practically carried out between the source and the measurement can be practically carried out between the source and the
destination of the interest. Sometimes there are reasons that the destination of the interest. Sometimes there are reasons that the
measurement can not be executed from the source to the destination. measurement can not be executed from the source to the destination.
For instance, the measurement path may cross several independent For instance, the measurement path may cross several independent
domains that have conflicting policies, measurement tools and domains that have conflicting policies, measurement tools and
methods, and measurement time slot assignment. The solution then may methods, and measurement time assignment. The solution then may be
be the composition of several sub-path measurements. That means each the composition of several sub-path measurements. This means each
domain performs the One-way measurement on a sub path between two domain performs the One-way measurement on a sub path between two
nodes that are involved in the complete path following its own nodes that are involved in the complete path following its own
policy, using its own measurement tools and methods, and within its policy, using its own measurement tools and methods, and using its
own measurement time slot. Under the appropriate conditions, one can own measurement timing. Under the appropriate conditions, one can
combine the sub-path One-way metric results to estimate the complete combine the sub-path One-way metric results to estimate the complete
path One-way measurement metric with some accuracy. path One-way measurement metric with some degree of accuracy.
3. Scope, Application, and Terminology 3. Scope, Application, and Terminology
3.1. Scope of work 3.1. Scope of work
For the primary IPPM metrics (currently Loss, Delay, and Delay For the primary IPPM metrics of Loss, Delay, and Delay Variation,
Variation), this memo gives a set of complete path metrics that can this memo gives a set of complete path metrics that can be composed
be composed from the same or similar sub-path metrics. This means from the same or similar sub-path metrics. This means that the
that the complete path metric may be composed from: complete path metric may be composed from:
o the same metric for each sub-path; o the same metric for each sub-path;
o multiple metrics for each sub-path (possibly one that is the same o multiple metrics for each sub-path (possibly one that is the same
as the complete path metric); as the complete path metric);
o a single sub-path metrics that is different from the complete path o a single sub-path metrics that is different from the complete path
metric; metric;
o different measurement techniques like active and passive o different measurement techniques like active and passive
(recognizing that PSAMP WG will define capabilities to sample (recognizing that PSAMP WG will define capabilities to sample
packets to support measurement). packets to support measurement).
3.2. Application 3.2. Application
The new composition framework [FRMWK] requires the specification of The new composition framework [I-D.ietf-ippm-framework-compagg]
the applicable circumstances for each metric. In particular, the requires the specification of the applicable circumstances for each
application of Spatial Composition metrics are addressed as to metric. In particular, the application of Spatial Composition
whether the metric: metrics are addressed as to whether the metric:
Requires the same test packets to traverse all sub-paths, or may use Requires the same test packets to traverse all sub-paths, or may use
similar packets sent and collected separately in each sub-path. similar packets sent and collected separately in each sub-path.
Requires homogeneity of measurement methodologies, or can allow a Requires homogeneity of measurement methodologies, or can allow a
degree of flexibility (e.g., active or passive methods produce the degree of flexibility (e.g., active or passive methods produce the
"same" metric). Also, the applicable sending streams will be "same" metric). Also, the applicable sending streams will be
specified, such as Poisson, Periodic, or both. specified, such as Poisson, Periodic, or both.
Needs information or access that will only be available within an Needs information or access that will only be available within an
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The complete path is the true path that a packet would follow as it The complete path is the true path that a packet would follow as it
traverses from the packet's Source to its Destination. traverses from the packet's Source to its Destination.
Complete path metric: 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.
Composite Metric (or Composed Metric): Composed Metric:
A composite metric is type of metric that is derived from other A composed metric is derived from other metrics principally by
metrics principally by applying a composition relationship. applying a composition function.
Composition Relationship: Composition Function:
A composition relationship is a deterministic process applied to Sub- A composition function is a deterministic process applied to Sub-path
path metrics to derive another metric (such as a Composite metric). metrics to derive another metric (such as a Composed metric).
Sub-path: 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 this sub-path is "involved" in the complete path.
Sub-path metrics: 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. One-way Delay Composition Metrics and Statistics 4. One-way Delay Composed Metrics and Statistics
4.1. Name: Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream 4.1. Name: Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream
This metric is a necessary element of Delay Composition metrics, and This metric is a necessary element of Delay Composition metrics, and
its definition does not formally exist elsewhere in IPPM literature. its definition does not formally exist elsewhere in IPPM literature.
4.1.1. Metric Parameters: 4.1.1. Metric Parameters:
o Src, the IP address of a host + Dst, the IP address of a host o Src, the IP address of a host + Dst, the IP address of a host
o T, a time (start of test interval) o T, a time (start of test interval)
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o T0, a time that MUST be selected at random from the interval [T, o T0, a time that MUST be selected at random from the interval [T,
T+dT] to start generating packets and taking measurements (for T+dT] to start generating packets and taking measurements (for
Periodic Streams) Periodic Streams)
o TstampSrc, the wire time of the packet as measured at MP(Src) o TstampSrc, the wire time of the packet as measured at MP(Src)
o TstampDst, the wire time of the packet as measured at MP(Dst), o TstampDst, the wire time of the packet as measured at MP(Dst),
assigned to packets that arrive within a "reasonable" time. assigned to packets that arrive within a "reasonable" time.
o Tmax, a maximum waiting time for packets at the destination. o Tmax, a maximum waiting time for packets at the destination, set
sufficiently long to disambiguate packets with long delays from
packets that are discarded (lost), thus the distribution of delay
is not truncated.
4.1.2. Definition and Metric Units 4.1.2. Definition and Metric Units
Using the parameters above, we obtain the value of Type-P-One-way- Using the parameters above, we obtain the value of Type-P-One-way-
Delay singleton as per RFC 2679 [RFC2679]. Delay singleton as per RFC 2679 [RFC2679].
For each packet [i] that has a finite One-way Delay (in other words, For each packet [i] that has a finite One-way Delay (in other words,
excluding packets which have undefined, or infinite one-way delay): excluding packets which have undefined one-way delay):
Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream[i] = Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream[i] =
FiniteDelay[i] = TstampDst - TstampSrc FiniteDelay[i] = TstampDst - TstampSrc
4.1.3. Discussion and other details 4.1.3. Discussion and other details
The "Type-P-Finite-One-way-Delay" metric allows calculation of the The "Type-P-Finite-One-way-Delay" metric permits calculation of the
mean statistic. This avoids the need to include lost packets in the sample mean statistic. This resolves the problem of including lost
sample (whose delay is undefined), and the issue with the prescribed packets in the sample (whose delay is undefined), and the issue with
assignment of infinite delay to lost packets when practical systems the informal assignment of infinite delay to lost packets (practical
can only assign some very large value. systems can only assign some very large value).
The Finite-One-way-Delay approach handles the problem of lost packets
by reducing the event space. We consider conditional statistics, and
estimate the mean one-way delay conditioned on the event that all
packets in the sample arrive at the destination (within the specified
waiting time, Tmax). This offers a way to make some valid statements
about one-way delay, and at the same time avoiding events with
undefined outcomes. This approach is derived from the treatment of
lost packets in [RFC3393], and is similar to[Y.1540] .
4.1.4. Mean Statistic 4.1.4. Mean Statistic
We add the following parameter: We add the following parameter:
o N, the total number of packets received at Dst (sent between T0 o N, the total number of packets received at Dst (sent between T0
and Tf) and Tf)
and define and define
Type-P-Finite-One-way-Delay-Mean = Type-P-Finite-One-way-Delay-Mean =
N N
--- ---
1 \ 1 \
- * > (FiniteDelay [i]) - * > (FiniteDelay [i])
N / N /
--- ---
i = 1 i = 1
where all packets i= 1 through N have finite singleton delays. where all packets i= 1 through N have finite singleton delays.
skipping to change at page 9, line 15 skipping to change at page 9, line 28
N N
--- ---
1 \ 1 \
- * > (FiniteDelay [i]) - * > (FiniteDelay [i])
N / N /
--- ---
i = 1 i = 1
where all packets i= 1 through N have finite singleton delays. where all packets i= 1 through N have finite singleton delays.
4.1.5. Composition Relationship: Sum of Means 4.1.5. Composition Function: Sum of Means
The Type-P-Finite--Composite-One-way-Delay-Mean, or CompMeanDelay for The Type-P-Finite--Composite-One-way-Delay-Mean, or CompMeanDelay for
the complete Source to Destination path can be calculated from sum of the complete Source to Destination path can be calculated from sum of
the Mean Delays of all its S constituent sub-paths. the Mean Delays of all its S constituent sub-paths.
o S, the number of sub-paths involved in the complete Src-Dst path. o S, the number of sub-paths involved in the complete Src-Dst path.
Then the Then the
Type-P-Finite-Composite-One-way-Delay-Mean = Type-P-Finite-Composite-One-way-Delay-Mean =
skipping to change at page 9, line 37 skipping to change at page 10, line 5
CompMeanDelay = (1/S)Sum(from i=1 to S, MeanDelay[i]) CompMeanDelay = (1/S)Sum(from i=1 to S, MeanDelay[i])
4.1.6. Statement of Conjecture 4.1.6. Statement of Conjecture
The mean of a sufficiently large stream of packets measured on each The mean of a sufficiently large stream of packets measured on each
sub-path during the interval [T, Tf] will be representative of the sub-path during the interval [T, Tf] will be representative of the
true mean of the delay distribution (and the distributions themselves true mean of the delay distribution (and the distributions themselves
are sufficiently independent), such that the means may be added to are sufficiently independent), such that the means may be added to
produce an estimate of the complete path mean delay. produce an estimate of the complete path mean delay.
4.1.7. Justification of Composite Relationship 4.1.7. Justification of the Composition Function
It is sometimes impractical to conduct active measurements between It is sometimes impractical to conduct active measurements between
every Src-Dst pair. For example, it may not be possible to collect every Src-Dst pair. For example, it may not be possible to collect
the desired sample size in each test interval when access link speed the desired sample size in each test interval when access link speed
is limited, because of the potential for measurement traffic to is limited, because of the potential for measurement traffic to
degrade the user traffic performance. The conditions on a low-speed degrade the user traffic performance. The conditions on a low-speed
access link may be understood well-enough to permit use of a small access link may be understood well-enough to permit use of a small
sample size/rate, while a larger sample size/rate may be used on sample size/rate, while a larger sample size/rate may be used on
other sub-paths. other sub-paths.
Also, since measurement operations have a real monetary cost, there Also, since measurement operations have a real monetary cost, there
is value in re-using measurements where they are applicable, rather is value in re-using measurements where they are applicable, rather
than launching new measurements for every possible source-destination than launching new measurements for every possible source-destination
pair. pair.
4.1.8. Sources of Error 4.1.8. Sources of Deviation from the Ground Truth
The measurement packets, each having source and destination addresses The measurement packets, each having source and destination addresses
intended for collection at edges of the sub-path, may take a intended for collection at edges of the sub-path, may take a
different specific path through the network equipment and parallel different specific path through the network equipment and parallel
exchanges than packets with the source and destination addresses of exchanges than packets with the source and destination addresses of
the complete path. Therefore, the sub-path measurements may differ the complete path. Therefore, the sub-path measurements may differ
from the performance experienced by packets on the complete path. from the performance experienced by packets on the complete path.
Multiple measurements employing sufficient sub-path address pairs Multiple measurements employing sufficient sub-path address pairs
might produce bounds on the extent of this error. might produce bounds on the extent of this error.
skipping to change at page 11, line 31 skipping to change at page 11, line 45
o L, either zero or one, where L=1 indicates loss and L=0 indicates o L, either zero or one, where L=1 indicates loss and L=0 indicates
arrival at the destination within TstampSrc + Tmax. arrival at the destination within TstampSrc + Tmax.
5.1.3. Discussion and other details 5.1.3. Discussion and other details
5.1.4. Statistic: Type-P-One-way-Packet-Loss-Empirical-Probability 5.1.4. Statistic: Type-P-One-way-Packet-Loss-Empirical-Probability
Given the following stream parameter Given the following stream parameter
o N, the total number of packets sent between T0 and Tf o M, the total number of packets sent between T0 and Tf
We can define the Empirical Probability of Loss Statistic (Ep), We can define the Empirical Probability of Loss Statistic (Ep),
consistent with Average Loss in [RFC2680], as follows: consistent with Average Loss in [RFC2680], as follows:
Type-P-One-way-Packet-Loss-Empirical-Probability = Type-P-One-way-Packet-Loss-Empirical-Probability =
Ep = (1/M)Sum(from i=1 to M, L[i])
Ep = (1/N)Sum(from i=1 to N, L[i]) where all packets i= 1 through M have a value for L.
where all packets i= 1 through N have a value for L.
5.1.5. Composition Relationship: Composition of Empirical Probabilities 5.1.5. Composition Function: Composition of Empirical Probabilities
The Type-P-One-way-Composite-Packet-Loss-Empirical-Probability, or The Type-P-One-way-Composite-Packet-Loss-Empirical-Probability, or
CompEp for the complete Source to Destination path can be calculated CompEp for the complete Source to Destination path can be calculated
by combining Ep of all its constituent sub-paths (Ep1, Ep2, Ep3, ... by combining Ep of all its constituent sub-paths (Ep1, Ep2, Ep3, ...
Epn) as Epn) as
Type-P-One-way-Composite-Packet-Loss-Empirical-Probability = CompEp = Type-P-One-way-Composite-Packet-Loss-Empirical-Probability = CompEp =
1 - {(1 - Ep1) x (1 - Ep2) x (1 - Ep3) x ... x (1 - Epn)} 1 - {(1 - Ep1) x (1 - Ep2) x (1 - Ep3) x ... x (1 - Epn)}
5.1.6. Statement of Conjecture 5.1.6. Statement of Conjecture
The empirical probability of loss calculated on a sufficiently large The empirical probability of loss calculated on a sufficiently large
stream of packets measured on each sub-path during the interval [T, stream of packets measured on each sub-path during the interval [T,
Tf] will be representative of the true loss probability (and the Tf] will be representative of the true loss probability (and the
probabilities themselves are sufficiently independent), such that the probabilities themselves are sufficiently independent), such that the
sub-path probabilities may be combined to produce an estimate of the sub-path probabilities may be combined to produce an estimate of the
complete path loss probability. complete path loss probability.
5.1.7. Justification of Composite Relationship 5.1.7. Justification of the Composition Function
It is sometimes impractical to conduct active measurements between It is sometimes impractical to conduct active measurements between
every Src-Dst pair. For example, it may not be possible to collect every Src-Dst pair. For example, it may not be possible to collect
the desired sample size in each test interval when access link speed the desired sample size in each test interval when access link speed
is limited, because of the potential for measurement traffic to is limited, because of the potential for measurement traffic to
degrade the user traffic performance. The conditions on a low-speed degrade the user traffic performance. The conditions on a low-speed
access link may be understood well-enough to permit use of a small access link may be understood well-enough to permit use of a small
sample size/rate, while a larger sample size/rate may be used on sample size/rate, while a larger sample size/rate may be used on
other sub-paths. other sub-paths.
Also, since measurement operations have a real monetary cost, there Also, since measurement operations have a real monetary cost, there
is value in re-using measurements where they are applicable, rather is value in re-using measurements where they are applicable, rather
than launching new measurements for every possible source-destination than launching new measurements for every possible source-destination
pair. pair.
5.1.8. Sources of Error 5.1.8. Sources of Deviation from the Ground Truth
The measurement packets, each having source and destination addresses The measurement packets, each having source and destination addresses
intended for collection at edges of the sub-path, may take a intended for collection at edges of the sub-path, may take a
different specific path through the network equipment and parallel different specific path through the network equipment and parallel
exchanges than packets with the source and destination addresses of exchanges than packets with the source and destination addresses of
the complete path. Therefore, the sub-path measurements may differ the complete path. Therefore, the sub-path measurements may differ
from the performance experienced by packets on the complete path. from the performance experienced by packets on the complete path.
Multiple measurements employing sufficient sub-path address pairs Multiple measurements employing sufficient sub-path address pairs
might produce bounds on the extent of this error. might produce bounds on the extent of this error.
skipping to change at page 15, line 43 skipping to change at page 16, line 21
--- ---
i = 1 i = 1
------------------------------------------- -------------------------------------------
/ \ / \
| ( 3/2 ) | | ( 3/2 ) |
\ (N - 1) * VarIPDVRefMin / \ (N - 1) * VarIPDVRefMin /
We define the Quantile of the IPDVRefMin sample as the value where We define the Quantile of the IPDVRefMin sample as the value where
the specified fraction of points is less than the given value. the specified fraction of points is less than the given value.
6.1.5. Composition Relationships: 6.1.5. Composition Functions:
The Type-P-One-way-Composite-ipdv-refmin-<something> for the complete The Type-P-One-way-Composite-ipdv-refmin-<something> for the complete
Source to Destination path can be calculated by combining statistics Source to Destination path can be calculated by combining statistics
of all the constituent sub-paths in the following process: of all the constituent sub-paths in the following process:
< to be provided > < see [Y.1541] >
6.1.6. Statement of Conjecture 6.1.6. Statement of Conjecture
6.1.7. Justification of Composite Relationship 6.1.7. Justification of the Composition Function
6.1.8. Sources of Error 6.1.8. Sources of Deviation from the Ground Truth
6.1.9. Specific cases where the conjecture might fail 6.1.9. Specific cases where the conjecture might fail
6.1.10. Application of Measurement Methodology 6.1.10. Application of Measurement Methodology
7. Other Metrics and Statistics: One-way Combined Metric 7. Other Metrics and Statistics: One-way Combined Metric
This definition may be the common part for the definition of "Loss This definition may be the common part for the definition of "Loss
Metrics/Statistics" and for the definition of "One-way Delay Metrics/Statistics" and for the definition of "One-way Delay
Composition Metrics and Statistics". Composition Metrics and Statistics".
skipping to change at page 20, line 5 skipping to change at page 20, line 28
To discourage the kind of interference mentioned above, packet To discourage the kind of interference mentioned above, packet
interference checks, such as cryptographic hash, may be used. interference checks, such as cryptographic hash, may be used.
9. IANA Considerations 9. IANA Considerations
Metrics defined in this memo will be registered in the IANA IPPM Metrics defined in this memo will be registered in the IANA IPPM
METRICS REGISTRY as described in initial version of the registry RFC METRICS REGISTRY as described in initial version of the registry RFC
4148 [RFC4148]. 4148 [RFC4148].
10. Security Considerations 10. Open Issues
11. Open Issues
>>>>>>>>>>>>Open issue: >>>>>>>>>>>>Open issue:
What is the relationship between the decomposition and composition What is the relationship between the decomposition and composition
metrics? Should we put both kinds in one draft to make up a metrics? Should we put both kinds in one draft to make up a
framework? The motivation of decomposition is as follows: framework? The motivation of decomposition is as follows:
The One-way measurement can provide result to show what the network The One-way measurement can provide result to show what the network
performance between two end hosts is and whether it meets operator performance between two end hosts is and whether it meets operator
expectations or not. It cannot provide further information to expectations or not. It cannot provide further information to
skipping to change at page 20, line 29 skipping to change at page 21, line 4
and the destination. For instance, if the network performance is not and the destination. For instance, if the network performance is not
acceptable in terms of the One-way measurement, in which part of the acceptable in terms of the One-way measurement, in which part of the
network the engineers should put their efforts. This question can to network the engineers should put their efforts. This question can to
be answered by decompose the One-way measurement to sub-path be answered by decompose the One-way measurement to sub-path
measurement to investigate the performance of different part of the measurement to investigate the performance of different part of the
network. network.
Editor's Questions for clarification: What additional information Editor's Questions for clarification: What additional information
would be provided to the decomposition process, beyond the would be provided to the decomposition process, beyond the
measurement of the complete path? measurement of the complete path?
Is the decomposition described above intended to estimate a metric Is the decomposition described above intended to estimate a metric
for some/all disjoint sub-paths involved in the complete path? for some/all disjoint sub-paths involved in the complete path?
>>>>>>>>>>>>>>>>>>RESOLUTION: treat this topic in a seperate memo
>>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>>>>OPEN Issue >>>>>>>>>>>>>>>>>>>OPEN Issue
Section 7 defines a new type of metric, a "combination" of metrics Section 7 defines a new type of metric, a "combination" of metrics
for one-way delay and packet loss. The purpose of this metric is to for one-way delay and packet loss. The purpose of this metric is to
link these two primary metrics in a convenient way. link these two primary metrics in a convenient way.
Readers are asked to comment on the efficiency of the combination Readers are asked to comment on the efficiency of the combination
metric. metric.
>>>>>>>>>>>>>>>>>RESOLUTION: If a delay singleton is recorded as
having "undefined" delay when the packet does not arrive within the
waiting time Tmax, then this information is sufficient to determine
the fraction of lost packets in the sample, and the additional loss
indication of this combo is not needed.
>>>>>>>>>>>>>>>>>> >>>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>>> OPEN Issue >>>>>>>>>>>>>>>>> OPEN Issue
How can we introduce multicast metrics here, without causing too much How can we introduce multicast metrics here, without causing too much
confusion? Should the multicast version of this draft wait until the confusion? Should the multicast version of this draft wait until the
Unicast concepts are stable (or maybe appear in a separate draft)? Unicast concepts are stable (or maybe appear in a separate draft)?
12. Acknowledgements >>>>>>>>>>>>>>>>RESOLUTION: Yes and Yes.
13. References 11. Acknowledgements
13.1. Normative References 12. References
[FRMWK] Morton, A. and S.Van Den Berghe, "Framework for Metric 12.1. Normative References
Composition", February 2006.
[I-D.ietf-ippm-framework-compagg]
Morton, A. and S. Berghe, "Framework for Metric
Composition", draft-ietf-ippm-framework-compagg-00 (work
in progress), February 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.
[RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way [RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Delay Metric for IPPM", RFC 2679, September 1999. Delay Metric for IPPM", RFC 2679, September 1999.
[RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way [RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Packet Loss Metric for IPPM", RFC 2680, September 1999. Packet Loss Metric for IPPM", RFC 2680, September 1999.
[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
Metric for IP Performance Metrics (IPPM)", RFC 3393,
November 2002.
[RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network [RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network
performance measurement with periodic streams", RFC 3432, performance measurement with periodic streams", RFC 3432,
November 2002. November 2002.
[RFC4148] Stephan, E., "IP Performance Metrics (IPPM) Metrics [RFC4148] Stephan, E., "IP Performance Metrics (IPPM) Metrics
Registry", BCP 108, RFC 4148, August 2005. Registry", BCP 108, RFC 4148, August 2005.
13.2. Informative References 12.2. Informative References
[I-D.stephan-ippm-multimetrics] [I-D.stephan-ippm-multimetrics]
Stephan, E., "IP Performance Metrics (IPPM) for spatial Stephan, E., "IP Performance Metrics (IPPM) for spatial
and multicast", draft-stephan-ippm-multimetrics-02 (work and multicast", draft-stephan-ippm-multimetrics-02 (work
in progress), October 2005. in progress), October 2005.
[Y.1540] ITU-T Recommendation Y.1540, "Internet protocol data [Y.1540] ITU-T Recommendation Y.1540, "Internet protocol data
communication service - IP packet transfer and communication service - IP packet transfer and
availability performance parameters", December 2002. availability performance parameters", December 2002.
[Y.1541] ITU-T Recommendation Y.1540, "Network Performance
Objectives for IP-based Services", February 2006.
Authors' Addresses Authors' Addresses
Al Morton Al Morton
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
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