draft-ietf-ippm-spatial-composition-16.txt | rfc6049.txt | |||
---|---|---|---|---|

Network Working Group A. Morton | Internet Engineering Task Force (IETF) A. Morton | |||

Internet-Draft AT&T Labs | Request for Comments: 6049 AT&T Labs | |||

Intended status: Standards Track E. Stephan | Category: Standards Track E. Stephan | |||

Expires: February 14, 2011 France Telecom Division R&D | ISSN: 2070-1721 France Telecom Orange | |||

August 13, 2010 | January 2011 | |||

Spatial Composition of Metrics | Spatial Composition of Metrics | |||

draft-ietf-ippm-spatial-composition-16 | ||||

Abstract | Abstract | |||

This memo utilizes IP Performance Metrics that are applicable to both | This memo utilizes IP performance metrics that are applicable to both | |||

complete paths and sub-paths, and defines relationships to compose a | complete paths and sub-paths, and it defines relationships to compose | |||

complete path metric from the sub-path metrics with some accuracy | a complete path metric from the sub-path metrics with some accuracy | |||

w.r.t. the actual metrics. This is called Spatial Composition in RFC | with regard to the actual metrics. This is called "spatial | |||

2330. The memo refers to the Framework for Metric Composition, and | composition" in RFC 2330. The memo refers to the framework for | |||

provides background and motivation for combining metrics to derive | metric composition, and provides background and motivation for | |||

others. The descriptions of several composed metrics and statistics | combining metrics to derive others. The descriptions of several | |||

follow. | composed metrics and statistics follow. | |||

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]. | ||||

In this memo, the characters "<=" should be read as "less than or | ||||

equal to" and ">=" as "greater than or equal to". | ||||

Status of this Memo | ||||

This Internet-Draft is submitted in full conformance with the | Status of This Memo | |||

provisions of BCP 78 and BCP 79. | ||||

Internet-Drafts are working documents of the Internet Engineering | This is an Internet Standards Track document. | |||

Task Force (IETF). Note that other groups may also distribute | ||||

working documents as Internet-Drafts. The list of current Internet- | ||||

Drafts is at http://datatracker.ietf.org/drafts/current/. | ||||

Internet-Drafts are draft documents valid for a maximum of six months | This document is a product of the Internet Engineering Task Force | |||

and may be updated, replaced, or obsoleted by other documents at any | (IETF). It represents the consensus of the IETF community. It has | |||

time. It is inappropriate to use Internet-Drafts as reference | received public review and has been approved for publication by the | |||

material or to cite them other than as "work in progress." | Internet Engineering Steering Group (IESG). Further information on | |||

Internet Standards is available in Section 2 of RFC 5741. | ||||

This Internet-Draft will expire on February 14, 2011. | Information about the current status of this document, any errata, | |||

and how to provide feedback on it may be obtained at | ||||

http://www.rfc-editor.org/info/rfc6049. | ||||

Copyright Notice | Copyright Notice | |||

Copyright (c) 2010 IETF Trust and the persons identified as the | ||||

Copyright (c) 2011 IETF Trust and the persons identified as the | ||||

document authors. All rights reserved. | document authors. All rights reserved. | |||

This document is subject to BCP 78 and the IETF Trust's Legal | This document is subject to BCP 78 and the IETF Trust's Legal | |||

Provisions Relating to IETF Documents | Provisions Relating to IETF Documents | |||

(http://trustee.ietf.org/license-info) in effect on the date of | (http://trustee.ietf.org/license-info) in effect on the date of | |||

publication of this document. Please review these documents | publication of this document. Please review these documents | |||

carefully, as they describe your rights and restrictions with respect | carefully, as they describe your rights and restrictions with respect | |||

to this document. Code Components extracted from this document must | to this document. Code Components extracted from this document must | |||

include Simplified BSD License text as described in Section 4.e of | include Simplified BSD License text as described in Section 4.e of | |||

the Trust Legal Provisions and are provided without warranty as | the Trust Legal Provisions and are provided without warranty as | |||

skipping to change at page 3, line 7 | skipping to change at page 3, line 7 | |||

modifications of such material outside the IETF Standards Process. | modifications of such material outside the IETF Standards Process. | |||

Without obtaining an adequate license from the person(s) controlling | Without obtaining an adequate license from the person(s) controlling | |||

the copyright in such materials, this document may not be modified | the copyright in such materials, this document may not be modified | |||

outside the IETF Standards Process, and derivative works of it may | outside the IETF Standards Process, and derivative works of it may | |||

not be created outside the IETF Standards Process, except to format | not be created outside the IETF Standards Process, except to format | |||

it for publication as an RFC or to translate it into languages other | it for publication as an RFC or to translate it into languages other | |||

than English. | than English. | |||

Table of Contents | Table of Contents | |||

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 | 1. Introduction ....................................................4 | |||

1.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 6 | 1.1. Motivation .................................................6 | |||

2. Scope and Application . . . . . . . . . . . . . . . . . . . . 6 | 1.2. Requirements Language ......................................6 | |||

2.1. Scope of work . . . . . . . . . . . . . . . . . . . . . . 6 | 2. Scope and Application ...........................................6 | |||

2.2. Application . . . . . . . . . . . . . . . . . . . . . . . 7 | 2.1. Scope of Work ..............................................6 | |||

2.3. Incomplete Information . . . . . . . . . . . . . . . . . . 7 | 2.2. Application ................................................7 | |||

3. Common Specifications for Composed Metrics . . . . . . . . . . 7 | 2.3. Incomplete Information .....................................7 | |||

3.1. Name: Type-P . . . . . . . . . . . . . . . . . . . . . . . 8 | 3. Common Specifications for Composed Metrics ......................8 | |||

3.1.1. Metric Parameters . . . . . . . . . . . . . . . . . . 8 | 3.1. Name: Type-P ...............................................8 | |||

3.1.2. Definition and Metric Units . . . . . . . . . . . . . 9 | 3.1.1. Metric Parameters ...................................8 | |||

3.1.3. Discussion and other details . . . . . . . . . . . . . 9 | 3.1.2. Definition and Metric Units .........................9 | |||

3.1.4. Statistic: . . . . . . . . . . . . . . . . . . . . . . 9 | 3.1.3. Discussion and Other Details ........................9 | |||

3.1.5. Composition Function . . . . . . . . . . . . . . . . . 9 | 3.1.4. Statistic ...........................................9 | |||

3.1.6. Statement of Conjecture and Assumptions . . . . . . . 9 | 3.1.5. Composition Function ................................9 | |||

3.1.7. Justification of the Composition Function . . . . . . 9 | 3.1.6. Statement of Conjecture and Assumptions ............10 | |||

3.1.8. Sources of Deviation from the Ground Truth . . . . . . 10 | 3.1.7. Justification of the Composition Function ..........10 | |||

3.1.9. Specific cases where the conjecture might fail . . . . 11 | 3.1.8. Sources of Deviation from the Ground Truth .........10 | |||

3.1.10. Application of Measurement Methodology . . . . . . . . 11 | 3.1.9. Specific Cases where the Conjecture Might Fail .....11 | |||

4. One-way Delay Composed Metrics and Statistics . . . . . . . . 12 | 3.1.10. Application of Measurement Methodology ............12 | |||

4.1. Name: Type-P-Finite-One-way-Delay-<Sample>-Stream . . . . 12 | 4. One-Way Delay Composed Metrics and Statistics ..................12 | |||

4.1.1. Metric Parameters . . . . . . . . . . . . . . . . . . 12 | 4.1. Name: Type-P-Finite-One-way-Delay-<Sample>-Stream .........12 | |||

4.1.2. Definition and Metric Units . . . . . . . . . . . . . 12 | 4.1.1. Metric Parameters ..................................12 | |||

4.1.3. Discussion and other details . . . . . . . . . . . . . 12 | 4.1.2. Definition and Metric Units ........................12 | |||

4.1.4. Statistic: . . . . . . . . . . . . . . . . . . . . . . 13 | 4.1.3. Discussion and Other Details .......................13 | |||

4.2. Name: Type-P-Finite-Composite-One-way-Delay-Mean . . . . . 13 | 4.1.4. Statistic ..........................................13 | |||

4.2.1. Metric Parameters . . . . . . . . . . . . . . . . . . 13 | 4.2. Name: Type-P-Finite-Composite-One-way-Delay-Mean ..........13 | |||

4.2.2. Definition and Metric Units of the Mean Statistic . . 13 | 4.2.1. Metric Parameters ..................................13 | |||

4.2.3. Discussion and other details . . . . . . . . . . . . . 14 | 4.2.2. Definition and Metric Units of the Mean Statistic ..14 | |||

4.2.4. Statistic: . . . . . . . . . . . . . . . . . . . . . . 14 | 4.2.3. Discussion and Other Details .......................14 | |||

4.2.5. Composition Function: Sum of Means . . . . . . . . . . 14 | 4.2.4. Statistic ..........................................14 | |||

4.2.6. Statement of Conjecture and Assumptions . . . . . . . 14 | 4.2.5. Composition Function: Sum of Means .................14 | |||

4.2.7. Justification of the Composition Function . . . . . . 14 | 4.2.6. Statement of Conjecture and Assumptions ............15 | |||

4.2.8. Sources of Deviation from the Ground Truth . . . . . . 14 | 4.2.7. Justification of the Composition Function ..........15 | |||

4.2.9. Specific cases where the conjecture might fail . . . . 15 | 4.2.8. Sources of Deviation from the Ground Truth .........15 | |||

4.2.10. Application of Measurement Methodology . . . . . . . . 15 | 4.2.9. Specific Cases where the Conjecture Might Fail .....15 | |||

4.3. Name: Type-P-Finite-Composite-One-way-Delay-Minimum . . . 15 | 4.2.10. Application of Measurement Methodology ............16 | |||

4.3.1. Metric Parameters . . . . . . . . . . . . . . . . . . 15 | 4.3. Name: Type-P-Finite-Composite-One-way-Delay-Minimum .......16 | |||

4.3.2. Definition and Metric Units of the Minimum | 4.3.1. Metric Parameters ..................................16 | |||

Statistic . . . . . . . . . . . . . . . . . . . . . . 15 | 4.3.2. Definition and Metric Units of the Minimum | |||

4.3.3. Discussion and other details . . . . . . . . . . . . . 16 | Statistic ..........................................16 | |||

4.3.4. Statistic: . . . . . . . . . . . . . . . . . . . . . . 16 | 4.3.3. Discussion and Other Details .......................16 | |||

4.3.5. Composition Function: Sum of Minima . . . . . . . . . 16 | 4.3.4. Statistic ..........................................16 | |||

4.3.6. Statement of Conjecture and Assumptions . . . . . . . 16 | 4.3.5. Composition Function: Sum of Minima ................16 | |||

4.3.7. Justification of the Composition Function . . . . . . 16 | 4.3.6. Statement of Conjecture and Assumptions ............17 | |||

4.3.8. Sources of Deviation from the Ground Truth . . . . . . 16 | 4.3.7. Justification of the Composition Function ..........17 | |||

4.3.9. Specific cases where the conjecture might fail . . . . 17 | 4.3.8. Sources of Deviation from the Ground Truth .........17 | |||

4.3.10. Application of Measurement Methodology . . . . . . . . 17 | 4.3.9. Specific Cases where the Conjecture Might Fail .....17 | |||

5. Loss Metrics and Statistics . . . . . . . . . . . . . . . . . 17 | 4.3.10. Application of Measurement Methodology ............17 | |||

5.1. Type-P-Composite-One-way-Packet-Loss-Empirical-Probability 17 | 5. Loss Metrics and Statistics ....................................18 | |||

5.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 17 | 5.1. Type-P-Composite-One-way-Packet-Loss-Empirical-Probability 18 | |||

5.1.2. Definition and Metric Units . . . . . . . . . . . . . 17 | 5.1.1. Metric Parameters ..................................18 | |||

5.1.3. Discussion and other details . . . . . . . . . . . . . 17 | 5.1.2. Definition and Metric Units ........................18 | |||

5.1.4. Statistic: | 5.1.3. Discussion and Other Details .......................18 | |||

Type-P-One-way-Packet-Loss-Empirical-Probability . . . 17 | 5.1.4. Statistic: | |||

5.1.5. Composition Function: Composition of Empirical | Type-P-One-way-Packet-Loss-Empirical-Probability ...18 | |||

Probabilities . . . . . . . . . . . . . . . . . . . . 18 | 5.1.5. Composition Function: Composition of | |||

5.1.6. Statement of Conjecture and Assumptions . . . . . . . 18 | Empirical Probabilities ............................18 | |||

5.1.7. Justification of the Composition Function . . . . . . 18 | 5.1.6. Statement of Conjecture and Assumptions ............19 | |||

5.1.8. Sources of Deviation from the Ground Truth . . . . . . 18 | 5.1.7. Justification of the Composition Function ..........19 | |||

5.1.9. Specific cases where the conjecture might fail . . . . 18 | 5.1.8. Sources of Deviation from the Ground Truth .........19 | |||

5.1.10. Application of Measurement Methodology . . . . . . . . 19 | 5.1.9. Specific Cases where the Conjecture Might Fail .....19 | |||

6. Delay Variation Metrics and Statistics . . . . . . . . . . . . 19 | 5.1.10. Application of Measurement Methodology ............19 | |||

6.1. Name: Type-P-One-way-pdv-refmin-<Sample>-Stream . . . . . 19 | 6. Delay Variation Metrics and Statistics .........................20 | |||

6.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 19 | 6.1. Name: Type-P-One-way-pdv-refmin-<Sample>-Stream ...........20 | |||

6.1.2. Definition and Metric Units . . . . . . . . . . . . . 20 | 6.1.1. Metric Parameters ..................................20 | |||

6.1.3. Discussion and other details . . . . . . . . . . . . . 20 | 6.1.2. Definition and Metric Units ........................20 | |||

6.1.4. Statistics: Mean, Variance, Skewness, Quantile . . . . 20 | 6.1.3. Discussion and Other Details .......................21 | |||

6.1.5. Composition Functions: . . . . . . . . . . . . . . . . 21 | 6.1.4. Statistics: Mean, Variance, Skewness, Quantile .....21 | |||

6.1.6. Statement of Conjecture and Assumptions . . . . . . . 22 | 6.1.5. Composition Functions ..............................22 | |||

6.1.7. Justification of the Composition Function . . . . . . 23 | 6.1.6. Statement of Conjecture and Assumptions ............23 | |||

6.1.8. Sources of Deviation from the Ground Truth . . . . . . 23 | 6.1.7. Justification of the Composition Function ..........23 | |||

6.1.9. Specific cases where the conjecture might fail . . . . 23 | 6.1.8. Sources of Deviation from the Ground Truth .........23 | |||

6.1.10. Application of Measurement Methodology . . . . . . . . 23 | 6.1.9. Specific Cases where the Conjecture Might Fail .....24 | |||

7. Security Considerations . . . . . . . . . . . . . . . . . . . 23 | 6.1.10. Application of Measurement Methodology ............24 | |||

7.1. Denial of Service Attacks . . . . . . . . . . . . . . . . 23 | 7. Security Considerations ........................................24 | |||

7.2. User Data Confidentiality . . . . . . . . . . . . . . . . 24 | 7.1. Denial-of-Service Attacks .................................24 | |||

7.3. Interference with the metrics . . . . . . . . . . . . . . 24 | 7.2. User Data Confidentiality .................................24 | |||

8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 | 7.3. Interference with the Metrics .............................24 | |||

9. Contributors and Acknowledgements . . . . . . . . . . . . . . 27 | 8. IANA Considerations ............................................25 | |||

10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28 | 9. Contributors and Acknowledgements ..............................27 | |||

10.1. Normative References . . . . . . . . . . . . . . . . . . . 28 | 10. References ....................................................28 | |||

10.2. Informative References . . . . . . . . . . . . . . . . . . 29 | 10.1. Normative References .....................................28 | |||

Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29 | 10.2. Informative References ...................................28 | |||

Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29 | ||||

1. Introduction | 1. Introduction | |||

The IP Performance Metrics (IPPM) framework [RFC2330] describes two | The IP Performance Metrics (IPPM) framework [RFC2330] describes two | |||

forms of metric composition, spatial and temporal. The composition | forms of metric composition: spatial and temporal. The composition | |||

framework [RFC5835] expands and further qualifies these original | framework [RFC5835] expands and further qualifies these original | |||

forms into three categories. This memo describes Spatial | forms into three categories. This memo describes spatial | |||

Composition, one of the categories of metrics under the umbrella of | composition, one of the categories of metrics under the umbrella of | |||

the composition 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 main purpose of this memo is to define the deterministic | The main purpose of this memo is to define the deterministic | |||

functions that yield the complete path metrics using metrics of the | functions that yield the complete path metrics using metrics of the | |||

sub-paths. The effectiveness of such metrics is dependent on their | sub-paths. The effectiveness of such metrics is dependent on their | |||

usefulness in analysis and applicability with practical measurement | usefulness in analysis and applicability with practical measurement | |||

methods. | 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 and assumptions of | o the specific conjecture applied to the metric and assumptions of | |||

the statistical model of the process being measured (if any, see | the statistical model of the process being measured (if any; see | |||

[RFC2330] section 12), | [RFC2330], Section 12), | |||

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, | |||

and | and | |||

o an analysis of how the conjecture could be incorrect. | o an analysis of how the conjecture could be incorrect. | |||

Also, [RFC2330] gives an example using the conjecture that the delay | Also, [RFC2330] gives an example using the conjecture that the delay | |||

of a path is very nearly the sum of the delays of the exchanges and | of a path is very nearly the sum of the delays of the exchanges and | |||

clouds of the corresponding path digest. This example is | clouds of the corresponding path digest. This example is | |||

particularly relevant to those who wish to assess the performance of | particularly relevant to those who wish to assess the performance of | |||

an Inter-domain path without direct measurement, and the performance | an inter-domain path without direct measurement, and the performance | |||

estimate of the complete path is related to the measured results for | estimate of the complete path is related to the measured results for | |||

various sub-paths instead. | various sub-paths instead. | |||

Approximate functions between the sub-path and complete path metrics | Approximate functions between the sub-path and complete path 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. | |||

1.1. Motivation | 1.1. Motivation | |||

One-way metrics defined in other RFCs (such as [RFC2679] and | One-way metrics defined in other RFCs (such as [RFC2679] and | |||

[RFC2680]) all assume that the measurement can be practically carried | [RFC2680]) all assume that the measurement can be practically carried | |||

out between the source and the destination of interest. Sometimes | out between the source and the destination of interest. Sometimes | |||

there are reasons that the measurement cannot be executed from the | there are reasons that the measurement cannot be executed from the | |||

source to the destination. For instance, the measurement path may | source to the destination. For instance, the measurement path may | |||

cross several independent domains that have conflicting policies, | cross several independent domains that have conflicting policies, | |||

measurement tools and methods, and measurement time assignment. The | measurement tools and methods, and measurement time assignment. The | |||

solution then may be the composition of several sub-path | solution then may be the composition of several sub-path | |||

measurements. This means each domain performs the One-way | measurements. This means each domain performs the one-way | |||

measurement on a sub path between two nodes that are involved in the | measurement on a sub-path between two nodes that are involved in the | |||

complete path following its own policy, using its own measurement | complete path, following its own policy, using its own measurement | |||

tools and methods, and using its own measurement timing. Under the | tools and methods, and using its own measurement timing. Under the | |||

appropriate conditions, one can combine the sub-path One-way metric | appropriate conditions, one can combine the sub-path one-way metric | |||

results to estimate the complete path One-way measurement metric with | results to estimate the complete path one-way measurement metric with | |||

some degree of accuracy. | some degree of accuracy. | |||

1.2. 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]. | ||||

In this memo, the characters "<=" should be read as "less than or | ||||

equal to" and ">=" as "greater than or equal to". | ||||

2. Scope and Application | 2. Scope and Application | |||

2.1. Scope of work | 2.1. Scope of Work | |||

For the primary IPPM metrics of Loss [RFC2680], Delay [RFC2679], and | For the primary IP Performance Metrics RFCs for loss [RFC2680], delay | |||

Delay Variation [RFC3393], this memo gives a set of metrics that can | [RFC2679], and delay variation [RFC3393], this memo gives a set of | |||

be composed from the same or similar sub-path metrics. This means | metrics that can be composed from the same or similar sub-path | |||

that the composition function may utilize: | metrics. This means that the composition function may utilize: | |||

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 metric that is different from the complete path | o a single sub-path metric that is different from the complete path | |||

metric; | metric; | |||

o different measurement techniques like active [RFC2330], [RFC3432] | o different measurement techniques like active [RFC2330], [RFC3432] | |||

and passive [RFC5474]. | and passive [RFC5474]. | |||

We note a possibility: Using a complete path metric and all but one | We note a possibility: using a complete path metric and all but one | |||

sub-path metric to infer the performance of the missing sub-path, | sub-path metric to infer the performance of the missing sub-path, | |||

especially when the "last" sub-path metric is missing. However, such | especially when the "last" sub-path metric is missing. However, such | |||

de-composition calculations, and the corresponding set of issues they | de-composition calculations, and the corresponding set of issues they | |||

raise, are beyond the scope of this memo. | raise, are beyond the scope of this memo. | |||

2.2. Application | 2.2. Application | |||

The composition framework [RFC5835] requires the specification of the | The composition framework [RFC5835] requires the specification of the | |||

applicable circumstances for each metric. In particular, each | applicable circumstances for each metric. In particular, each | |||

section addresses whether the metric: | section addresses whether the metric: | |||

Requires the same test packets to traverse all sub-paths, or may use | o Requires the same test packets to traverse all sub-paths or may | |||

similar packets sent and collected separately in each sub-path. | use similar packets sent and collected separately in each | |||

sub-path. | ||||

Requires homogeneity of measurement methodologies, or can allow a | o 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, active spatial division | |||

"same" metric). Also, the applicable sending streams will be | [RFC5644], or passive methods produce the "same" metric). Also, | |||

specified, such as Poisson, Periodic, or both. | the applicable sending streams will be specified, such as Poisson, | |||

Periodic, or both. | ||||

Needs information or access that will only be available within an | o Needs information or access that will only be available within an | |||

operator's domain, or is applicable to Inter-domain composition. | operator's domain, or is applicable to inter-domain composition. | |||

Requires synchronized measurement start and stop times in all sub- | o Requires synchronized measurement start and stop times in all | |||

paths, or largely overlapping, or no timing requirements. | sub-paths or largely overlapping measurement intervals, or no | |||

timing requirements. | ||||

Requires assumption of sub-path independence w.r.t. the metric being | o Requires the assumption of sub-path independence with regard to | |||

defined/composed, or other assumptions. | the metric being defined/composed or other assumptions. | |||

Has known sources of inaccuracy/error, and identifies the sources. | o Has known sources of inaccuracy/error and identifies the sources. | |||

2.3. Incomplete Information | 2.3. Incomplete Information | |||

In practice, when measurements cannot be initiated on a sub-path (and | In practice, when measurements cannot be initiated on a sub-path (and | |||

perhaps the measurement system gives up during the test interval), | perhaps the measurement system gives up during the test interval), | |||

then there will not be a value for the sub-path reported, and the | then there will not be a value for the sub-path reported, and the | |||

entire test result SHOULD be recorded as "undefined". This case | entire test result SHOULD be recorded as "undefined". This case | |||

should be distinguished from the case where the measurement system | should be distinguished from the case where the measurement system | |||

continued to send packets throughout the test interval, but all were | continued to send packets throughout the test interval, but all were | |||

declared lost. | declared lost. | |||

When a composed metric requires measurements from sub paths A, B, and | When a composed metric requires measurements from sub-paths A, B, and | |||

C, and one or more of the sub-path results are undefined, then the | C, and one or more of the sub-path results are undefined, then the | |||

composed metric SHOULD also be recorded as undefined. | composed metric SHOULD also be recorded as undefined. | |||

3. Common Specifications for Composed Metrics | 3. Common Specifications for Composed Metrics | |||

To reduce the redundant information presented in the detailed metrics | To reduce the redundant information presented in the detailed metrics | |||

sections that follow, this section presents the specifications that | sections that follow, this section presents the specifications that | |||

are common to two or more metrics. The section is organized using | are common to two or more metrics. The section is organized using | |||

the same subsections as the individual metrics, to simplify | the same subsections as the individual metrics, to simplify | |||

comparisons. | comparisons. | |||

Also, the following index variables represent the following: | Also, the index variables are represented as follows: | |||

o m = index for packets sent | o m = index for packets sent. | |||

o n = index for packets received | o n = index for packets received. | |||

o s = index for involved sub-paths | o s = index for involved sub-paths. | |||

3.1. Name: Type-P | 3.1. Name: Type-P | |||

All metrics use the Type-P convention as described in [RFC2330]. The | All metrics use the "Type-P" convention as described in [RFC2330]. | |||

rest of the name is unique to each metric. | The rest of the name is unique to each metric. | |||

3.1.1. Metric Parameters | 3.1.1. Metric Parameters | |||

o Src, the IP address of a host | o Src, the IP address of a host. | |||

o Dst, the IP address of a host | o Dst, the IP address of a host. | |||

o T, a time (start of test interval) | o T, a time (start of test interval). | |||

o Tf, a time (end of test interval) | o Tf, a time (end of test interval). | |||

o lambda, a rate in reciprocal seconds (for Poisson Streams) | o lambda, a rate in reciprocal seconds (for Poisson Streams). | |||

o incT, the nominal duration of inter-packet interval, first bit to | o incT, the nominal duration of inter-packet interval, first bit to | |||

first bit (for Periodic Streams) | first bit (for Periodic Streams). | |||

o T0, a time that MUST be selected at random from the interval [T, | o dT, the duration of the allowed interval for Periodic Stream | |||

T+dT] to start generating packets and taking measurements (for | sample start times. | |||

Periodic Streams) | ||||

o T0, a time that MUST be selected at random from the interval | ||||

[T, T + dT] to start generating packets and taking measurements | ||||

(for 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) | |||

(measurement point at the source). | ||||

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, set | o Tmax, a maximum waiting time for packets at the destination, set | |||

sufficiently long to disambiguate packets with long delays from | sufficiently long to disambiguate packets with long delays from | |||

packets that are discarded (lost), thus the distribution of delay | packets that are discarded (lost); thus, the distribution of delay | |||

is not truncated. | is not truncated. | |||

o M, the total number of packets sent between T0 and Tf | o M, the total number of packets sent between T0 and Tf. | |||

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). | |||

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. | |||

o Type-P, as defined in [RFC2330], which includes any field that may | o Type-P, as defined in [RFC2330], which includes any field that may | |||

affect a packet's treatment as it traverses the network | affect a packet's treatment as it traverses the network. | |||

In metric names, the term <Sample> is intended to be replaced by the | In metric names, the term "<Sample>" is intended to be replaced by | |||

name of the method used to define a sample of values of parameter | the name of the method used to define a sample of values of parameter | |||

TstampSrc. This can be done in several ways, including: | TstampSrc. This can be done in several ways, including: | |||

1. Poisson: a pseudo-random Poisson process of rate lambda, whose | 1. Poisson: a pseudo-random Poisson process of rate lambda, whose | |||

values fall between T and Tf. The time interval between | values fall between T and Tf. The time interval between | |||

successive values of TstampSrc will then average 1/lambda, as per | successive values of TstampSrc will then average 1/lambda, as per | |||

[RFC2330]. | [RFC2330]. | |||

2. Periodic: a periodic stream process with pseudo-random start time | 2. Periodic: a Periodic stream process with pseudo-random start time | |||

T0 between T and dT, and nominal inter-packet interval incT, as | T0 between T and dT, and nominal inter-packet interval incT, as | |||

per [RFC3432]. | per [RFC3432]. | |||

3.1.2. Definition and Metric Units | 3.1.2. Definition and Metric Units | |||

This section is unique for every metric. | This section is unique for every metric. | |||

3.1.3. Discussion and other details | 3.1.3. Discussion and Other Details | |||

This section is unique for every metric. | This section is unique for every metric. | |||

3.1.4. Statistic: | 3.1.4. Statistic | |||

This section is unique for every metric. | This section is unique for every metric. | |||

3.1.5. Composition Function | 3.1.5. Composition Function | |||

This section is unique for every metric. | This section is unique for every metric. | |||

3.1.6. Statement of Conjecture and Assumptions | 3.1.6. Statement of Conjecture and Assumptions | |||

This section is unique for each metric. The term "ground truth" | This section is unique for each metric. The term "ground truth" is | |||

frequently used in these sections and it is defined in section 4.7 of | frequently used in these sections and is defined in Section 4.7 of | |||

[RFC5835]. | [RFC5835]. | |||

3.1.7. Justification of the Composition Function | 3.1.7. 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. Since the full mesh of N measurement points | every Src-Dst pair. Since the full mesh of N measurement points | |||

grows as N x N, the scope of measurement may be limited by testing | grows as N x N, the scope of measurement may be limited by testing | |||

resources. | resources. | |||

There may be varying limitations on active testing in different parts | There may be varying limitations on active testing in different parts | |||

of the network. For example, it may not be possible to collect the | of the network. For example, it may not be possible to collect the | |||

desired sample size in each test interval when access link speed is | desired sample size in each test interval when access link speed is | |||

limited, because of the potential for measurement traffic to degrade | limited, because of the potential for measurement traffic to degrade | |||

the user traffic performance. The conditions on a low-speed access | the user traffic performance. The conditions on a low-speed access | |||

link may be understood well-enough to permit use of a small sample | 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 other sub- | size/rate, while a larger sample size/rate may be used on other | |||

paths. | 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. | |||

3.1.8. Sources of Deviation from the Ground Truth | 3.1.8. Sources of Deviation from the Ground Truth | |||

3.1.8.1. Sub-path List Differs from Complete Path | 3.1.8.1. Sub-Path List Differs from Complete Path | |||

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 links when | different specific path through the network equipment and links when | |||

compared to packets with the source and destination addresses of the | compared to packets with the source and destination addresses of the | |||

complete path. Examples sources of parallel paths include Equal Cost | complete path. Example sources of parallel paths include Equal Cost | |||

Multi-Path and parallel (or bundled) links. Therefore, the | Multi-Path and parallel (or bundled) links. Therefore, the | |||

performance estimated from the composition of sub-path measurements | performance estimated from the composition of sub-path measurements | |||

may differ from the performance experienced by packets on the | may differ from the performance experienced by packets on the | |||

complete path. Multiple measurements employing sufficient sub-path | complete path. Multiple measurements employing sufficient sub-path | |||

address pairs might produce bounds on the extent of this error. | address pairs might produce bounds on the extent of this error. | |||

We also note the possibility of re-routing during a measurement | We also note the possibility of re-routing during a measurement | |||

interval, as it may affect the correspondence between packets | interval, as it may affect the correspondence between packets | |||

traversing the complete path and the sub-paths that were "involved" | traversing the complete path and the sub-paths that were "involved" | |||

prior to the re-route. | prior to the re-route. | |||

3.1.8.2. Sub-path Contains Extra Network Elements | 3.1.8.2. Sub-Path Contains Extra Network Elements | |||

Related to the case of an alternate path described above is the case | Related to the case of an alternate path described above is the case | |||

where elements in the measured path are unique to measurement system | where elements in the measured path are unique to measurement system | |||

connectivity. For example, a measurement system may use a dedicated | connectivity. For example, a measurement system may use a dedicated | |||

link to a LAN switch, and packets on the complete path do not | link to a LAN switch, and packets on the complete path do not | |||

traverse that link. The performance of such a dedicated link would | traverse that link. The performance of such a dedicated link would | |||

be measured continuously, and its contribution to the sub-path | be measured continuously, and its contribution to the sub-path | |||

metrics SHOULD be minimized as a source of error. | metrics SHOULD be minimized as a source of error. | |||

3.1.8.3. Sub-paths Have Incomplete Coverage | 3.1.8.3. Sub-Paths Have Incomplete Coverage | |||

Measurements of sub-path performance may not cover all the network | Measurements of sub-path performance may not cover all the network | |||

elements on the complete path. For example, the network exchange | elements on the complete path. For example, the network exchange | |||

points might be excluded unless a cooperative measurement is | points might be excluded unless a cooperative measurement is | |||

conducted. In this example, test packets on the previous sub-path | conducted. In this example, test packets on the previous sub-path | |||

are received just before the exchange point and test packets on the | are received just before the exchange point, and test packets on the | |||

next sub-path are injected just after the same exchange point. | next sub-path are injected just after the same exchange point. | |||

Clearly, the set of sub-path measurements SHOULD cover all critical | Clearly, the set of sub-path measurements SHOULD cover all critical | |||

network elements in the complete path. | network elements in the complete path. | |||

3.1.8.4. Absence of route | 3.1.8.4. Absence of Route | |||

At a specific point in time, no viable route exists between the | At a specific point in time, no viable route exists between the | |||

complete path source and destination. The routes selected for one or | complete path source and destination. The routes selected for one or | |||

more sub-paths therefore differs from the complete path. | more sub-paths therefore differ from the complete path. | |||

Consequently, spatial composition may produce finite estimation of a | Consequently, spatial composition may produce finite estimation of a | |||

ground truth metric (see section 4.7 of [RFC5835]) between a source | ground truth metric (see Section 4.7 of [RFC5835]) between a source | |||

and a destination, even when the route between them is undefined. | and a destination, even when the route between them is undefined. | |||

3.1.9. Specific cases where the conjecture might fail | 3.1.9. Specific Cases where the Conjecture Might Fail | |||

This section is unique for most metrics (see the metric-specific | This section is unique for most metrics (see the metric-specific | |||

sections). | sections). | |||

For delay-related metrics, One-way delay always depends on packet | For delay-related metrics, one-way delay always depends on packet | |||

size and link capacity, since it is measured in [RFC2679] from first | size and link capacity, since it is measured in [RFC2679] from first | |||

bit to last bit. If the size of an IP packet changes on route (due | bit to last bit. If the size of an IP packet changes on its route | |||

to encapsulation), this can influence delay performance. However, | (due to encapsulation), this can influence delay performance. | |||

the main error source may be the additional processing associated | However, the main error source may be the additional processing | |||

with encapsulation and encryption/decryption if not experienced or | associated with encapsulation and encryption/decryption if not | |||

accounted for in sub-path measurements. | experienced or accounted for in sub-path measurements. | |||

Fragmentation is a major issue for composition accuracy, since all | Fragmentation is a major issue for composition accuracy, since all | |||

metrics require all fragments to arrive before proceeding, and | metrics require all fragments to arrive before proceeding, and | |||

fragmented complete path performance is likely to be different from | fragmented complete path performance is likely to be different from | |||

performance with non-fragmented packets and composed metrics based on | performance with non-fragmented packets and composed metrics based on | |||

non-fragmented sub-path measurements. | non-fragmented sub-path measurements. | |||

Highly manipulated routing can cause measurement error if not | Highly manipulated routing can cause measurement error if not | |||

expected and compensated. For example, policy-based MPLS routing | expected and compensated for. For example, policy-based MPLS routing | |||

could modify the class of service for the sub-paths and complete | could modify the class of service for the sub-paths and complete | |||

path. | path. | |||

3.1.10. Application of Measurement Methodology | 3.1.10. Application of Measurement Methodology | |||

The methodology: | o The methodology SHOULD use similar packets sent and collected | |||

separately in each sub-path, where "similar" in this case means | ||||

SHOULD use similar packets sent and collected separately in each sub- | that Type-P contains as many equal attributes as possible, while | |||

path, where "similar" in this case means that the Type-P contains as | recognizing that there will be differences. Note that Type-P | |||

many equal attributes as possible, while recognizing that there will | includes stream characteristics (e.g., Poisson, Periodic). | |||

be differences. Note that Type-P includes stream characteristics | ||||

(e.g., Poisson, Periodic). | ||||

Allows a degree of flexibility regarding test stream generation | o The methodology allows a degree of flexibility regarding test | |||

(e.g., active or passive methods can produce an equivalent result, | stream generation (e.g., active or passive methods can produce an | |||

but the lack of control over the source, timing and correlation of | equivalent result, but the lack of control over the source, | |||

passive measurements is much more challenging). | timing, and correlation of passive measurements is much more | |||

challenging). | ||||

Poisson and/or Periodic streams are RECOMMENDED. | o Poisson and/or Periodic streams are RECOMMENDED. | |||

Applies to both Inter-domain and Intra-domain composition. | o The methodology applies to both inter-domain and intra-domain | |||

composition. | ||||

SHOULD have synchronized measurement time intervals in all sub-paths, | o The methodology SHOULD have synchronized measurement time | |||

but largely overlapping intervals MAY suffice. | intervals in all sub-paths, but largely overlapping intervals MAY | |||

suffice. | ||||

Assumption of sub-path independence w.r.t. the metric being defined/ | o Assumption of sub-path independence with regard to the metric | |||

composed is REQUIRED. | being defined/composed is REQUIRED. | |||

4. One-way Delay Composed Metrics and Statistics | 4. One-Way Delay Composed Metrics and Statistics | |||

4.1. Name: Type-P-Finite-One-way-Delay-<Sample>-Stream | 4.1. Name: Type-P-Finite-One-way-Delay-<Sample>-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 | |||

See the common parameters section above. | See the common parameters section (Section 3.1.1). | |||

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 the Type-P-One- | |||

Delay singleton as per [RFC2679]. | way-Delay singleton as per [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 | |||

excluding packets which have undefined one-way delay): | words, excluding packets that have undefined one-way delay): | |||

Type-P-Finite-One-way-Delay-<Sample>-Stream[i] = | Type-P-Finite-One-way-Delay-<Sample>-Stream[i] = | |||

FiniteDelay[i] = TstampDst - TstampSrc | FiniteDelay[i] = TstampDst - TstampSrc | |||

The units of measure for this metric are time in seconds, expressed | This metric is measured in units of time in seconds, expressed in | |||

in sufficiently low resolution to convey meaningful quantitative | sufficiently low resolution to convey meaningful quantitative | |||

information. For example, resolution of microseconds is usually | information. For example, resolution of microseconds is usually | |||

sufficient. | sufficient. | |||

4.1.3. Discussion and other details | 4.1.3. Discussion and Other Details | |||

The "Type-P-Finite-One-way-Delay" metric permits calculation of the | The "Type-P-Finite-One-way-Delay" metric permits calculation of the | |||

sample mean statistic. This resolves the problem of including lost | sample mean statistic. This resolves the problem of including lost | |||

packets in the sample (whose delay is undefined), and the issue with | packets in the sample (whose delay is undefined) and the issue with | |||

the informal assignment of infinite delay to lost packets (practical | the informal assignment of infinite delay to lost packets (practical | |||

systems 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 | The Finite-One-way-Delay approach handles the problem of lost packets | |||

by reducing the event space. We consider conditional statistics, and | by reducing the event space. We consider conditional statistics, and | |||

estimate the mean one-way delay conditioned on the event that all | estimate the mean one-way delay conditioned on the event that all | |||

packets in the sample arrive at the destination (within the specified | packets in the sample arrive at the destination (within the specified | |||

waiting time, Tmax). This offers a way to make some valid statements | waiting time, Tmax). This offers a way to make some valid statements | |||

about one-way delay, and at the same time avoiding events with | about one-way delay, at the same time avoiding events with undefined | |||

undefined outcomes. This approach is derived from the treatment of | outcomes. This approach is derived from the treatment of lost | |||

lost packets in [RFC3393], and is similar to [Y.1540] . | packets in [RFC3393], and is similar to [Y.1540]. | |||

4.1.4. Statistic: | 4.1.4. Statistic | |||

All statistics defined in [RFC2679] are applicable to the finite one- | All statistics defined in [RFC2679] are applicable to the finite one- | |||

way delay,and additional metrics are possible, such as the mean (see | way delay, and additional metrics are possible, such as the mean (see | |||

below). | below). | |||

4.2. Name: Type-P-Finite-Composite-One-way-Delay-Mean | 4.2. Name: Type-P-Finite-Composite-One-way-Delay-Mean | |||

This section describes a statistic based on the Type-P-Finite-One- | This section describes a statistic based on the Type-P-Finite-One- | |||

way-Delay-<Sample>-Stream metric. | way-Delay-<Sample>-Stream metric. | |||

4.2.1. Metric Parameters | 4.2.1. Metric Parameters | |||

See the common parameters section above. | See the common parameters section (Section 3.1.1). | |||

4.2.2. Definition and Metric Units of the Mean Statistic | 4.2.2. Definition and Metric Units of the Mean Statistic | |||

We define | We define | |||

Type-P-Finite-One-way-Delay-Mean = | Type-P-Finite-One-way-Delay-Mean = | |||

N | N | |||

--- | --- | |||

1 \ | 1 \ | |||

= MeanDelay = - * > (FiniteDelay [n]) | MeanDelay = - * > (FiniteDelay [n]) | |||

N / | N / | |||

--- | --- | |||

n = 1 | n = 1 | |||

where all packets n= 1 through N have finite singleton delays. | where all packets n = 1 through N have finite singleton delays. | |||

The units of measure for this metric are time in seconds, expressed | This metric is measured in units of time in seconds, expressed in | |||

in sufficiently fine resolution to convey meaningful quantitative | sufficiently fine resolution to convey meaningful quantitative | |||

information. For example, resolution of microseconds is usually | information. For example, resolution of microseconds is usually | |||

sufficient. | sufficient. | |||

4.2.3. Discussion and other details | 4.2.3. Discussion and Other Details | |||

The Type-P-Finite-One-way-Delay-Mean metric requires the conditional | The Type-P-Finite-One-way-Delay-Mean metric requires the conditional | |||

delay distribution described in section 5.1. | delay distribution described in Section 4.1.3. | |||

4.2.4. Statistic: | 4.2.4. Statistic | |||

This metric, a mean, does not require additional statistics. | This metric, a mean, does not require additional statistics. | |||

4.2.5. Composition Function: Sum of Means | 4.2.5. 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 the | |||

the Mean Delays of all its S constituent sub-paths. | sum of the mean delays of all of its S constituent sub-paths. | |||

Then the | Then the | |||

Type-P-Finite-Composite-One-way-Delay-Mean = | Type-P-Finite-Composite-One-way-Delay-Mean = | |||

S | S | |||

--- | --- | |||

\ | \ | |||

= CompMeanDelay = > (MeanDelay [s]) | CompMeanDelay = > (MeanDelay [s]) | |||

/ | / | |||

--- | --- | |||

s = 1 | s = 1 | |||

where sub-paths s = 1 to S are involved in the complete path. | where sub-paths s = 1 to S are involved in the complete path. | |||

4.2.6. Statement of Conjecture and Assumptions | 4.2.6. Statement of Conjecture and Assumptions | |||

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 | |||

ground truth mean of the delay distribution (and the distributions | ground truth mean of the delay distribution (and the distributions | |||

themselves are sufficiently independent), such that the means may be | themselves are sufficiently independent), such that the means may be | |||

added to produce an estimate of the complete path mean delay. | added to produce an estimate of the complete path mean delay. | |||

skipping to change at page 14, line 42 | skipping to change at page 15, line 29 | |||

4.2.6. Statement of Conjecture and Assumptions | 4.2.6. Statement of Conjecture and Assumptions | |||

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 | |||

ground truth mean of the delay distribution (and the distributions | ground truth mean of the delay distribution (and the distributions | |||

themselves are sufficiently independent), such that the means may be | themselves are sufficiently independent), such that the means may be | |||

added to produce an estimate of the complete path mean delay. | added to produce an estimate of the complete path mean delay. | |||

It is assumed that the one-way delay distributions of the sub-paths | It is assumed that the one-way delay distributions of the sub-paths | |||

and the complete path are continuous. The mean of multi-modal | and the complete path are continuous. The mean of multi-modal | |||

distributions have the unfortunate property that such a value may | distributions has the unfortunate property that such a value may | |||

never occur. | never occur. | |||

4.2.7. Justification of the Composition Function | 4.2.7. Justification of the Composition Function | |||

See the common section. | See the common section (Section 3). | |||

4.2.8. Sources of Deviation from the Ground Truth | 4.2.8. Sources of Deviation from the Ground Truth | |||

See the common section. | See the common section (Section 3). | |||

4.2.9. Specific cases where the conjecture might fail | 4.2.9. Specific Cases where the Conjecture Might Fail | |||

If any of the sub-path distributions are multi-modal, then the | If any of the sub-path distributions are multi-modal, then the | |||

measured means may not be stable, and in this case the mean will not | measured means may not be stable, and in this case the mean will not | |||

be a particularly useful statistic when describing the delay | be a particularly useful statistic when describing the delay | |||

distribution of the complete path. | distribution of the complete path. | |||

The mean may not be a sufficiently robust statistic to produce a | The mean may not be a sufficiently robust statistic to produce a | |||

reliable estimate, or to be useful even if it can be measured. | reliable estimate, or to be useful even if it can be measured. | |||

If a link contributing non-negligible delay is erroneously included | If a link contributing non-negligible delay is erroneously included | |||

or excluded, the composition will be in error. | or excluded, the composition will be in error. | |||

4.2.10. Application of Measurement Methodology | 4.2.10. Application of Measurement Methodology | |||

The requirements of the common section apply here as well. | The requirements of the common section (Section 3) apply here as | |||

well. | ||||

4.3. Name: Type-P-Finite-Composite-One-way-Delay-Minimum | 4.3. Name: Type-P-Finite-Composite-One-way-Delay-Minimum | |||

This section describes is a statistic based on the Type-P-Finite-One- | This section describes a statistic based on the Type-P-Finite-One- | |||

way-Delay-<Sample>-Stream metric, and the composed metric based on | way-Delay-<Sample>-Stream metric, and the composed metric based on | |||

that statistic. | that statistic. | |||

4.3.1. Metric Parameters | 4.3.1. Metric Parameters | |||

See the common parameters section above. | See the common parameters section (Section 3.1.1). | |||

4.3.2. Definition and Metric Units of the Minimum Statistic | 4.3.2. Definition and Metric Units of the Minimum Statistic | |||

We define | We define | |||

Type-P-Finite-One-way-Delay-Minimum = | Type-P-Finite-One-way-Delay-Minimum = | |||

= MinDelay = (FiniteDelay [j]) | ||||

such that for some index, j, where 1<= j <= N | MinDelay = (FiniteDelay [j]) | |||

such that for some index, j, where 1 <= j <= N | ||||

FiniteDelay[j] <= FiniteDelay[n] for all n | FiniteDelay[j] <= FiniteDelay[n] for all n | |||

where all packets n = 1 through N have finite singleton delays. | where all packets n = 1 through N have finite singleton delays. | |||

The units of measure for this metric are time in seconds, expressed | This metric is measured in units of time in seconds, expressed in | |||

in sufficiently fine resolution to convey meaningful quantitative | sufficiently fine resolution to convey meaningful quantitative | |||

information. For example, resolution of microseconds is usually | information. For example, resolution of microseconds is usually | |||

sufficient. | sufficient. | |||

4.3.3. Discussion and other details | 4.3.3. Discussion and Other Details | |||

The Type-P-Finite-One-way-Delay-Minimum metric requires the | The Type-P-Finite-One-way-Delay-Minimum metric requires the | |||

conditional delay distribution described in section 5.1.3. | conditional delay distribution described in Section 4.1.3. | |||

4.3.4. Statistic: | 4.3.4. Statistic | |||

This metric, a minimum, does not require additional statistics. | This metric, a minimum, does not require additional statistics. | |||

4.3.5. Composition Function: Sum of Minima | 4.3.5. Composition Function: Sum of Minima | |||

The Type-P-Finite-Composite-One-way-Delay-Minimum, or CompMinDelay, | The Type-P-Finite-Composite-One-way-Delay-Minimum, or CompMinDelay, | |||

for the complete Source to Destination path can be calculated from | for the complete source to destination path can be calculated from | |||

sum of the Minimum Delays of all its S constituent sub-paths. | the sum of the minimum delays of all of its S constituent sub-paths. | |||

Then the | Then the | |||

Type-P-Finite-Composite-One-way-Delay-Minimum = | Type-P-Finite-Composite-One-way-Delay-Minimum = | |||

S | S | |||

--- | --- | |||

\ | \ | |||

= CompMinDelay = > (MinDelay [s]) | CompMinDelay = > (MinDelay [s]) | |||

/ | / | |||

--- | --- | |||

s = 1 | s = 1 | |||

4.3.6. Statement of Conjecture and Assumptions | 4.3.6. Statement of Conjecture and Assumptions | |||

The minimum of a sufficiently large stream of packets measured on | The minimum of a sufficiently large stream of packets measured on | |||

each sub-path during the interval [T, Tf] will be representative of | each sub-path during the interval [T, Tf] will be representative of | |||

the ground truth minimum of the delay distribution (and the | the ground truth minimum of the delay distribution (and the | |||

distributions themselves are sufficiently independent), such that the | distributions themselves are sufficiently independent), such that the | |||

minima may be added to produce an estimate of the complete path | minima may be added to produce an estimate of the complete path | |||

minimum delay. | minimum delay. | |||

It is assumed that the one-way delay distributions of the sub-paths | It is assumed that the one-way delay distributions of the sub-paths | |||

and the complete path are continuous. | and the complete path are continuous. | |||

4.3.7. Justification of the Composition Function | 4.3.7. Justification of the Composition Function | |||

See the common section. | See the common section (Section 3). | |||

4.3.8. Sources of Deviation from the Ground Truth | 4.3.8. Sources of Deviation from the Ground Truth | |||

See the common section. | See the common section (Section 3). | |||

4.3.9. Specific cases where the conjecture might fail | 4.3.9. Specific Cases where the Conjecture Might Fail | |||

If the routing on any of the sub-paths is not stable, then the | If the routing on any of the sub-paths is not stable, then the | |||

measured minimum may not be stable. In this case the composite | measured minimum may not be stable. In this case the composite | |||

minimum would tend to produce an estimate for the complete path that | minimum would tend to produce an estimate for the complete path that | |||

may be too low for the current path. | may be too low for the current path. | |||

4.3.10. Application of Measurement Methodology | 4.3.10. Application of Measurement Methodology | |||

The requirements of the common section apply here as well. | The requirements of the common section (Section 3) apply here as | |||

well. | ||||

5. Loss Metrics and Statistics | 5. Loss Metrics and Statistics | |||

5.1. Type-P-Composite-One-way-Packet-Loss-Empirical-Probability | 5.1. Type-P-Composite-One-way-Packet-Loss-Empirical-Probability | |||

5.1.1. Metric Parameters: | 5.1.1. Metric Parameters | |||

Same as section 4.1.1. | See the common parameters section (Section 3.1.1). | |||

5.1.2. Definition and Metric Units | 5.1.2. 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 the Type-P-One- | |||

Packet-Loss singleton and stream as per [RFC2680]. | way-Packet-Loss singleton and stream as per [RFC2680]. | |||

We obtain a sequence of pairs with elements as follows: | We obtain a sequence of pairs with elements as follows: | |||

o TstampSrc, as above | o TstampSrc, as above. | |||

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 | |||

arrival at the destination within TstampSrc + Tmax. | indicates arrival at the destination within TstampSrc + Tmax. | |||

5.1.3. Discussion and other details | 5.1.3. Discussion and Other Details | |||

None. | None. | |||

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 stream parameter M, the number of packets sent, we can | Given the stream parameter M, the number of packets sent, we can | |||

define the Empirical Probability of Loss Statistic (Ep), consistent | define the Empirical Probability of Loss Statistic (Ep), consistent | |||

with Average Loss in [RFC2680], as follows: | with average loss in [RFC2680], as follows: | |||

Type-P-One-way-Packet-Loss-Empirical-Probability = | Type-P-One-way-Packet-Loss-Empirical-Probability = | |||

M | M | |||

--- | --- | |||

1 \ | 1 \ | |||

= Ep = - * > (L[m]) | Ep = - * > (L[m]) | |||

M / | M / | |||

--- | --- | |||

m = 1 | m = 1 | |||

where all packets m = 1 through M have a value for L. | where all packets m = 1 through M have a value for L. | |||

5.1.5. Composition Function: 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 the Ep of all of its constituent sub-paths (Ep1, Ep2, | |||

Epn) as | Ep3, ... Epn) as | |||

Type-P-Composite-One-way-Packet-Loss-Empirical-Probability = | Type-P-Composite-One-way-Packet-Loss-Empirical-Probability = | |||

= CompEp = 1 - {(1 - Ep1) x (1 - Ep2) x (1 - Ep3) x ... x (1 - EpS)} | ||||

CompEp = 1 - {(1 - Ep1) x (1 - Ep2) x (1 - Ep3) x ... x (1 - EpS)} | ||||

If any Eps is undefined in a particular measurement interval, | If any Eps is undefined in a particular measurement interval, | |||

possibly because a measurement system failed to report a value, then | possibly because a measurement system failed to report a value, then | |||

any CompEp that uses sub-path s for that measurement interval is | any CompEp that uses sub-path s for that measurement interval is | |||

undefined. | undefined. | |||

5.1.6. Statement of Conjecture and Assumptions | 5.1.6. Statement of Conjecture and Assumptions | |||

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 | |||

Tf] will be representative of the ground truth empirical loss | [T, Tf] will be representative of the ground truth empirical loss | |||

probability (and the probabilities themselves are sufficiently | probability (and the probabilities themselves are sufficiently | |||

independent), such that the sub-path probabilities may be combined to | independent), such that the sub-path probabilities may be combined to | |||

produce an estimate of the complete path empirical loss probability. | produce an estimate of the complete path empirical loss probability. | |||

5.1.7. Justification of the Composition Function | 5.1.7. Justification of the Composition Function | |||

See the common section. | See the common section (Section 3). | |||

5.1.8. Sources of Deviation from the Ground Truth | 5.1.8. Sources of Deviation from the Ground Truth | |||

See the common section. | See the common section (Section 3). | |||

5.1.9. Specific cases where the conjecture might fail | 5.1.9. Specific Cases where the Conjecture Might Fail | |||

A concern for loss measurements combined in this way is that root | A concern for loss measurements combined in this way is that root | |||

causes may be correlated to some degree. | causes may be correlated to some degree. | |||

For example, if the links of different networks follow the same | For example, if the links of different networks follow the same | |||

physical route, then a single catastrophic event like a fire in a | physical route, then a single catastrophic event like a fire in a | |||

tunnel could cause an outage or congestion on remaining paths in | tunnel could cause an outage or congestion on remaining paths in | |||

multiple networks. Here it is important to ensure that measurements | multiple networks. Here it is important to ensure that measurements | |||

before the event and after the event are not combined to estimate the | before the event and after the event are not combined to estimate the | |||

composite performance. | composite performance. | |||

Or, when traffic volumes rise due to the rapid spread of an email- | Or, when traffic volumes rise due to the rapid spread of an email- | |||

borne worm, loss due to queue overflow in one network may help | borne worm, loss due to queue overflow in one network may help | |||

another network to carry its traffic without loss. | another network to carry its traffic without loss. | |||

5.1.10. Application of Measurement Methodology | 5.1.10. Application of Measurement Methodology | |||

See the common section. | See the common section (Section 3). | |||

6. Delay Variation Metrics and Statistics | 6. Delay Variation Metrics and Statistics | |||

6.1. Name: Type-P-One-way-pdv-refmin-<Sample>-Stream | 6.1. Name: Type-P-One-way-pdv-refmin-<Sample>-Stream | |||

This packet delay variation (PDV) metric is a necessary element of | This packet delay variation (PDV) metric is a necessary element of | |||

Composed Delay Variation metrics, and its definition does not | Composed Delay Variation metrics, and its definition does not | |||

formally exist elsewhere in IPPM literature (with the exception of | formally exist elsewhere in IPPM literature (with the exception of | |||

[RFC5481] . | [RFC5481]). | |||

6.1.1. Metric Parameters: | 6.1.1. Metric Parameters | |||

In addition to the parameters of section 4.1.1: | In addition to the parameters of Section 3.1.1: | |||

o TstampSrc[i], the wire time of packet[i] as measured at MP(Src) | o TstampSrc[i], the wire time of packet[i] as measured at MP(Src) | |||

(measurement point at the source) | (measurement point at the source). | |||

o TstampDst[i], the wire time of packet[i] as measured at MP(Dst), | o TstampDst[i], the wire time of packet[i] as measured at MP(Dst), | |||

assigned to packets that arrive within a "reasonable" time. | assigned to packets that arrive within a "reasonable" time. | |||

o B, a packet length in bits | o B, a packet length in bits. | |||

o F, a selection function unambiguously defining the packets from | o F, a selection function unambiguously defining the packets from | |||

the stream that are selected for the packet-pair computation of | the stream that are selected for the packet-pair computation of | |||

this metric. F(current packet), the first packet of the pair, | this metric. F(current packet), the first packet of the pair, | |||

MUST have a valid Type-P-Finite-One-way-Delay less than Tmax (in | MUST have a valid Type-P-Finite-One-way-Delay less than Tmax (in | |||

other words, excluding packets which have undefined one-way delay) | other words, excluding packets that have undefined one-way delay) | |||

and MUST have been transmitted during the interval T, Tf. The | and MUST have been transmitted during the interval [T, Tf]. The | |||

second packet in the pair, F(min_delay packet) MUST be the packet | second packet in the pair, F(min_delay packet) MUST be the packet | |||

with the minimum valid value of Type-P-Finite-One-way-Delay for | with the minimum valid value of Type-P-Finite-One-way-Delay for | |||

the stream, in addition to the criteria for F(current packet). If | the stream, in addition to the criteria for F(current packet). If | |||

multiple packets have equal minimum Type-P-Finite-One-way-Delay | multiple packets have equal minimum Type-P-Finite-One-way-Delay | |||

values, then the value for the earliest arriving packet SHOULD be | values, then the value for the earliest arriving packet SHOULD be | |||

used. | used. | |||

o MinDelay, the Type-P-Finite-One-way-Delay value for F(min_delay | o MinDelay, the Type-P-Finite-One-way-Delay value for F(min_delay | |||

packet) given above. | packet) given above. | |||

o N, the number of packets received at the Destination meeting the | o N, the number of packets received at the destination that meet the | |||

F(current packet) criteria. | F(current packet) criteria. | |||

6.1.2. Definition and Metric Units | 6.1.2. Definition and Metric Units | |||

Using the definition above in section 5.1.2, we obtain the value of | Using the definition above in Section 5.1.2, we obtain the value of | |||

Type-P-Finite-One-way-Delay-<Sample>-Stream[n], the singleton for | Type-P-Finite-One-way-Delay-<Sample>-Stream[n], the singleton for | |||

each packet[i] in the stream (a.k.a. FiniteDelay[i]). | each packet[i] in the stream (a.k.a. FiniteDelay[i]). | |||

For each packet[n] that meets the F(first packet) criteria given | For each packet[n] that meets the F(first packet) criteria given | |||

above: Type-P-One-way-pdv-refmin-<Sample>-Stream[n] = | above: Type-P-One-way-pdv-refmin-<Sample>-Stream[n] = | |||

PDV[n] = FiniteDelay[n] - MinDelay | PDV[n] = FiniteDelay[n] - MinDelay | |||

where PDV[i] is in units of time in seconds, expressed in | where PDV[i] is in units of time in seconds, expressed in | |||

sufficiently fine resolution to convey meaningful quantitative | sufficiently fine resolution to convey meaningful quantitative | |||

information. For example, resolution of microseconds is usually | information. For example, resolution of microseconds is usually | |||

sufficient. | sufficient. | |||

6.1.3. Discussion and other details | 6.1.3. Discussion and Other Details | |||

This metric produces a sample of delay variation normalized to the | This metric produces a sample of delay variation normalized to the | |||

minimum delay of the sample. The resulting delay variation | minimum delay of the sample. The resulting delay variation | |||

distribution is independent of the sending sequence (although | distribution is independent of the sending sequence (although | |||

specific FiniteDelay values within the distribution may be | specific FiniteDelay values within the distribution may be | |||

correlated, depending on various stream parameters such as packet | correlated, depending on various stream parameters such as packet | |||

spacing). This metric is equivalent to the IP Packet Delay Variation | spacing). This metric is equivalent to the IP Packet Delay Variation | |||

parameter defined in [Y.1540]. | parameter defined in [Y.1540]. | |||

6.1.4. Statistics: Mean, Variance, Skewness, Quantile | 6.1.4. Statistics: Mean, Variance, Skewness, Quantile | |||

skipping to change at page 21, line 28 | skipping to change at page 22, line 8 | |||

--- | --- | |||

1 \ 2 | 1 \ 2 | |||

------- > (PDV[n] - MeanPDV) | ------- > (PDV[n] - MeanPDV) | |||

(N - 1) / | (N - 1) / | |||

--- | --- | |||

n = 1 | n = 1 | |||

We define the skewness of PDV as follows: | We define the skewness of PDV as follows: | |||

Type-P-One-way-pdv-refmin-Skewness = SkewPDV = | Type-P-One-way-pdv-refmin-Skewness = SkewPDV = | |||

N | N | |||

--- 3 | --- 3 | |||

\ / \ | \ / \ | |||

> | PDV[n]- MeanPDV | | > | PDV[n] - MeanPDV | | |||

/ \ / | / \ / | |||

--- | --- | |||

n = 1 | n = 1 | |||

----------------------------------- | ----------------------------------- | |||

/ \ | / \ | |||

| ( 3/2 ) | | | ( 3/2 ) | | |||

\ (N - 1) * VarPDV / | \ (N - 1) * VarPDV / | |||

(see Appendix X of [Y.1541] for additional background information). | (See Appendix X of [Y.1541] for additional background information.) | |||

We define the Quantile of the PDVRefMin sample as the value where the | We define the quantile of the PDV sample as the value where the | |||

specified fraction of singletons is less than the given value. | specified fraction of singletons is less than the given value. | |||

6.1.5. Composition Functions: | 6.1.5. Composition Functions | |||

This section gives two alternative composition functions. The | This section gives two alternative composition functions. The | |||

objective is to estimate a quantile of the complete path delay | objective is to estimate a quantile of the complete path delay | |||

variation distribution. The composed quantile will be estimated | variation distribution. The composed quantile will be estimated | |||

using information from the sub-path delay variation distributions. | using information from the sub-path delay variation distributions. | |||

6.1.5.1. Approximate Convolution | 6.1.5.1. Approximate Convolution | |||

The Type-P-Finite-One-way-Delay-<Sample>-Stream samples from each | The Type-P-Finite-One-way-Delay-<Sample>-Stream samples from each | |||

sub-path are summarized as a histogram with 1 ms bins representing | sub-path are summarized as a histogram with 1-ms bins representing | |||

the one-way delay distribution. | the one-way delay distribution. | |||

From [Stats], the distribution of the sum of independent random | From [STATS], the distribution of the sum of independent random | |||

variables can be derived using the relation: | variables can be derived using the relation: | |||

Type-P-Composite-One-way-pdv-refmin-quantile-a = | Type-P-Composite-One-way-pdv-refmin-quantile-a = | |||

. . | . . | |||

/ / | / / | |||

P(X + Y + Z <= a) = | | P(X <= a-y-z) * P(Y = y) * P(Z = z) dy dz | P(X + Y + Z <= a) = | | P(X <= a - y - z) * P(Y = y) * P(Z = z) dy dz | |||

/ / | / / | |||

` ` | ` ` | |||

z y | z y | |||

Note that dy and dz indicate partial integration above, and that y | ||||

and z are the integration variables. Also, the probablility of an | ||||

outcome is indicated by the symbol P(outcome). | ||||

where X, Y, and Z are random variables representing the delay | Note that dy and dz indicate partial integration above, and that y | |||

variation distributions of the sub-paths of the complete path (in | and z are the integration variables. Also, the probability of an | |||

this case, there are three sub-paths), and a is the quantile of | outcome is indicated by the symbol P(outcome), where X, Y, and Z are | |||

interest. | random variables representing the delay variation distributions of | |||

the sub-paths of the complete path (in this case, there are three | ||||

sub-paths), and "a" is the quantile of interest. | ||||

This relation can be used to compose a quantile of interest for the | This relation can be used to compose a quantile of interest for the | |||

complete path from the sub-path delay distributions. The histograms | complete path from the sub-path delay distributions. The histograms | |||

with 1 ms bins are discrete approximations of the delay | with 1-ms bins are discrete approximations of the delay | |||

distributions. | distributions. | |||

6.1.5.2. Normal Power Approximation | 6.1.5.2. Normal Power Approximation (NPA) | |||

Type-P-One-way-Composite-pdv-refmin-NPA for the complete Source to | Type-P-One-way-Composite-pdv-refmin-NPA for the complete source to | |||

Destination path can be calculated by combining statistics of all the | destination path can be calculated by combining the statistics of all | |||

constituent sub-paths in the process described in [Y.1541] clause 8 | the constituent sub-paths in the process described in [Y.1541], | |||

and Appendix X. | Clause 8 and Appendix X. | |||

6.1.6. Statement of Conjecture and Assumptions | 6.1.6. Statement of Conjecture and Assumptions | |||

The delay distribution of a sufficiently large stream of packets | The delay distribution of a sufficiently large stream of packets | |||

measured on each sub-path during the interval [T, Tf] will be | measured on each sub-path during the interval [T, Tf] will be | |||

sufficiently stationary and the sub-path distributions themselves are | sufficiently stationary, and the sub-path distributions themselves | |||

sufficiently independent, so that summary information describing the | are sufficiently independent, so that summary information describing | |||

sub-path distributions can be combined to estimate the delay | the sub-path distributions can be combined to estimate the delay | |||

distribution of complete path. | distribution of the complete path. | |||

It is assumed that the one-way delay distributions of the sub-paths | It is assumed that the one-way delay distributions of the sub-paths | |||

and the complete path are continuous. | and the complete path are continuous. | |||

6.1.7. Justification of the Composition Function | 6.1.7. Justification of the Composition Function | |||

See the common section. | See the common section (Section 3). | |||

6.1.8. Sources of Deviation from the Ground Truth | 6.1.8. Sources of Deviation from the Ground Truth | |||

In addition to the common deviations, a few additional sources exist | In addition to the common deviations, a few additional sources exist | |||

here. For one, very tight distributions with range on the order of a | here. For one, very tight distributions with ranges on the order of | |||

few milliseconds are not accurately represented by a histogram with 1 | a few milliseconds are not accurately represented by a histogram with | |||

ms bins. This size was chosen assuming an implicit requirement on | 1-ms bins. This size was chosen assuming an implicit requirement on | |||

accuracy: errors of a few milliseconds are acceptable when assessing | accuracy: errors of a few milliseconds are acceptable when assessing | |||

a composed distribution quantile. | a composed distribution quantile. | |||

Also, summary statistics cannot describe the subtleties of an | Also, summary statistics cannot describe the subtleties of an | |||

empirical distribution exactly, especially when the distribution is | empirical distribution exactly, especially when the distribution is | |||

very different from a classical form. Any procedure that uses these | very different from a classical form. Any procedure that uses these | |||

statistics alone may incur error. | statistics alone may incur error. | |||

6.1.9. Specific cases where the conjecture might fail | 6.1.9. Specific Cases where the Conjecture Might Fail | |||

If the delay distributions of the sub-paths are somehow correlated, | If the delay distributions of the sub-paths are somehow correlated, | |||

then neither of these composition functions will be reliable | then neither of these composition functions will be reliable | |||

estimators of the complete path distribution. | estimators of the complete path distribution. | |||

In practice, sub-path delay distributions with extreme outliers have | In practice, sub-path delay distributions with extreme outliers have | |||

increased the error of the composed metric estimate. | increased the error of the composed metric estimate. | |||

6.1.10. Application of Measurement Methodology | 6.1.10. Application of Measurement Methodology | |||

See the common section. | See the common section (Section 3). | |||

7. Security Considerations | 7. Security Considerations | |||

7.1. Denial of Service Attacks | 7.1. Denial-of-Service Attacks | |||

This metric requires a stream of packets sent from one host (source) | This metric requires a stream of packets sent from one host (source) | |||

to another host (destination) through intervening networks. This | to another host (destination) through intervening networks. This | |||

method could be abused for denial of service attacks directed at the | method could be abused for denial-of-service attacks directed at the | |||

destination and/or the intervening network(s). | destination and/or the intervening network(s). | |||

Administrators of source, destination, and the intervening network(s) | Administrators of source, destination, and intervening networks | |||

should establish bilateral or multi-lateral agreements regarding the | should establish bilateral or multilateral agreements regarding the | |||

timing, size, and frequency of collection of sample metrics. Use of | timing, size, and frequency of collection of sample metrics. Use of | |||

this method in excess of the terms agreed between the participants | this method in excess of the terms agreed upon between the | |||

may be cause for immediate rejection or discard of packets or other | participants may be cause for immediate rejection or discarding of | |||

escalation procedures defined between the affected parties. | packets, or other escalation procedures defined between the affected | |||

parties. | ||||

7.2. User Data Confidentiality | 7.2. User Data Confidentiality | |||

Active use of this method generates packets for a sample, rather than | Active use of this method generates packets for a sample, rather than | |||

taking samples based on user data, and does not threaten user data | taking samples based on user data, and does not threaten user data | |||

confidentiality. Passive measurement MUST restrict attention to the | confidentiality. Passive measurement MUST restrict attention to the | |||

headers of interest. Since user payloads may be temporarily stored | headers of interest. Since user payloads may be temporarily stored | |||

for length analysis, suitable precautions MUST be taken to keep this | for length analysis, suitable precautions MUST be taken to keep this | |||

information safe and confidential. In most cases, a hashing function | information safe and confidential. In most cases, a hashing function | |||

will produce a value suitable for payload comparisons. | will produce a value suitable for payload comparisons. | |||

7.3. Interference with the metrics | 7.3. Interference with the Metrics | |||

It may be possible to identify that a certain packet or stream of | It may be possible to identify that a certain packet or stream of | |||

packets is part of a sample. With that knowledge at the destination | packets is part of a sample. With that knowledge at the destination | |||

and/or the intervening networks, it is possible to change the | and/or the intervening networks, it is possible to change the | |||

processing of the packets (e.g. increasing or decreasing delay) that | processing of the packets (e.g., increasing or decreasing delay), | |||

may distort the measured performance. It may also be possible to | which may distort the measured performance. It may also be possible | |||

generate additional packets that appear to be part of the sample | to generate additional packets that appear to be part of the sample | |||

metric. These additional packets are likely to perturb the results | metric. These additional packets are likely to perturb the results | |||

of the sample measurement. | of the sample measurement. | |||

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. | |||

8. IANA Considerations | 8. IANA Considerations | |||

Metrics defined in IETF are typically registered in the IANA IPPM | Metrics defined in the IETF are typically registered in the IANA IPPM | |||

METRICS REGISTRY as described in initial version of the registry | Metrics Registry as described in the initial version of the registry | |||

[RFC4148]. | [RFC4148]. | |||

IANA is asked to register the following metrics in the IANA-IPPM- | IANA has registered the following metrics in the | |||

METRICS-REGISTRY-MIB: | IANA-IPPM-METRICS-REGISTRY-MIB: | |||

ietfFiniteOneWayDelayStream OBJECT-IDENTITY | ietfFiniteOneWayDelayStream OBJECT-IDENTITY | |||

STATUS current | STATUS current | |||

DESCRIPTION | DESCRIPTION | |||

"Type-P-Finite-One-way-Delay-Stream" | "Type-P-Finite-One-way-Delay-Stream" | |||

REFERENCE | REFERENCE "RFC 6049, Section 4.1." | |||

"Reference "RFCyyyy, section 4.1." | ::= { ianaIppmMetrics 71 } | |||

-- RFC Ed.: replace yyyy with actual RFC number & remove this | ||||

note | ||||

::= { ianaIppmMetrics nn } -- IANA assigns nn | ||||

ietfFiniteOneWayDelayMean OBJECT-IDENTITY | ietfFiniteOneWayDelayMean OBJECT-IDENTITY | |||

STATUS current | STATUS current | |||

DESCRIPTION | DESCRIPTION | |||

"Type-P-Finite-One-way-Delay-Mean" | "Type-P-Finite-One-way-Delay-Mean" | |||

REFERENCE | REFERENCE "RFC 6049, Section 4.2." | |||

"Reference "RFCyyyy, section 4.2." | ::= { ianaIppmMetrics 72 } | |||

-- RFC Ed.: replace yyyy with actual RFC number & remove this | ||||

note | ||||

::= { ianaIppmMetrics nn } -- IANA assigns nn | ||||

ietfCompositeOneWayDelayMean OBJECT-IDENTITY | ietfCompositeOneWayDelayMean OBJECT-IDENTITY | |||

STATUS current | STATUS current | |||

DESCRIPTION | DESCRIPTION | |||

"Type-P-Finite-Composite-One-way-Delay-Mean" | "Type-P-Finite-Composite-One-way-Delay-Mean" | |||

REFERENCE | REFERENCE "RFC 6049, Section 4.2.5." | |||

"Reference "RFCyyyy, section 4.2.5." | ::= { ianaIppmMetrics 73 } | |||

-- RFC Ed.: replace yyyy with actual RFC number & remove this | ||||

note | ||||

::= { ianaIppmMetrics nn } -- IANA assigns nn | ||||

ietfFiniteOneWayDelayMinimum OBJECT-IDENTITY | ietfFiniteOneWayDelayMinimum OBJECT-IDENTITY | |||

STATUS current | STATUS current | |||

DESCRIPTION | DESCRIPTION | |||

"Type-P-Finite-One-way-Delay-Minimum" | "Type-P-Finite-One-way-Delay-Minimum" | |||

REFERENCE | REFERENCE "RFC 6049, Section 4.3.2." | |||

"Reference "RFCyyyy, section 4.3.2." | ::= { ianaIppmMetrics 74 } | |||

-- RFC Ed.: replace yyyy with actual RFC number & remove this | ||||

note | ||||

::= { ianaIppmMetrics nn } -- IANA assigns nn | ||||

ietfCompositeOneWayDelayMinimum OBJECT-IDENTITY | ietfCompositeOneWayDelayMinimum OBJECT-IDENTITY | |||

STATUS current | STATUS current | |||

DESCRIPTION | DESCRIPTION | |||

"Type-P-Finite-Composite-One-way-Delay-Minimum" | "Type-P-Finite-Composite-One-way-Delay-Minimum" | |||

REFERENCE | REFERENCE "RFC 6049, Section 4.3." | |||

"Reference "RFCyyyy, section 4.3." | ::= { ianaIppmMetrics 75 } | |||

-- RFC Ed.: replace yyyy with actual RFC number & remove this | ||||

note | ||||

::= { ianaIppmMetrics nn } -- IANA assigns nn | ||||

ietfOneWayPktLossEmpiricProb OBJECT-IDENTITY | ietfOneWayPktLossEmpiricProb OBJECT-IDENTITY | |||

STATUS current | STATUS current | |||

DESCRIPTION | DESCRIPTION | |||

"Type-P-One-way-Packet-Loss-Empirical-Probability" | "Type-P-One-way-Packet-Loss-Empirical-Probability" | |||

REFERENCE | REFERENCE "RFC 6049, Section 5.1.4" | |||

"Reference "RFCyyyy, section 5.1.4" | ::= { ianaIppmMetrics 76 } | |||

-- RFC Ed.: replace yyyy with actual RFC number & remove this | ||||

note | ||||

::= { ianaIppmMetrics nn } -- IANA assigns nn | ||||

ietfCompositeOneWayPktLossEmpiricProb OBJECT-IDENTITY | ietfCompositeOneWayPktLossEmpiricProb OBJECT-IDENTITY | |||

STATUS current | STATUS current | |||

DESCRIPTION | DESCRIPTION | |||

"Type-P-Composite-One-way-Packet-Loss-Empirical-Probability" | "Type-P-Composite-One-way-Packet-Loss-Empirical-Probability" | |||

REFERENCE | REFERENCE "RFC 6049, Section 5.1." | |||

"Reference "RFCyyyy, section 5.1." | ::= { ianaIppmMetrics 77 } | |||

-- RFC Ed.: replace yyyy with actual RFC number & remove this | ||||

note | ||||

::= { ianaIppmMetrics nn } -- IANA assigns nn | ||||

ietfOneWayPdvRefminStream OBJECT-IDENTITY | ietfOneWayPdvRefminStream OBJECT-IDENTITY | |||

STATUS current | STATUS current | |||

DESCRIPTION | DESCRIPTION | |||

"Type-P-One-way-pdv-refmin-Stream" | "Type-P-One-way-pdv-refmin-Stream" | |||

REFERENCE | REFERENCE "RFC 6049, Section 6.1." | |||

"Reference "RFCyyyy, section 6.1." | ::= { ianaIppmMetrics 78 } | |||

-- RFC Ed.: replace yyyy with actual RFC number & remove this | ||||

note | ||||

::= { ianaIppmMetrics nn } -- IANA assigns nn | ||||

ietfOneWayPdvRefminMean OBJECT-IDENTITY | ietfOneWayPdvRefminMean OBJECT-IDENTITY | |||

STATUS current | STATUS current | |||

DESCRIPTION | DESCRIPTION | |||

"Type-P-One-way-pdv-refmin-Mean" | "Type-P-One-way-pdv-refmin-Mean" | |||

REFERENCE | REFERENCE "RFC 6049, Section 6.1.4." | |||

"Reference "RFCyyyy, section 6.1.4." | ::= { ianaIppmMetrics 79 } | |||

-- RFC Ed.: replace yyyy with actual RFC number & remove this | ||||

note | ||||

::= { ianaIppmMetrics nn } -- IANA assigns nn | ||||

ietfOneWayPdvRefminVariance OBJECT-IDENTITY | ietfOneWayPdvRefminVariance OBJECT-IDENTITY | |||

STATUS current | STATUS current | |||

DESCRIPTION | DESCRIPTION | |||

"Type-P-One-way-pdv-refmin-Variance" | "Type-P-One-way-pdv-refmin-Variance" | |||

REFERENCE | REFERENCE "RFC 6049, Section 6.1.4." | |||

"Reference "RFCyyyy, section 6.1.4." | ::= { ianaIppmMetrics 80 } | |||

-- RFC Ed.: replace yyyy with actual RFC number & remove this | ||||

note | ||||

::= { ianaIppmMetrics nn } -- IANA assigns nn | ||||

ietfOneWayPdvRefminSkewness OBJECT-IDENTITY | ietfOneWayPdvRefminSkewness OBJECT-IDENTITY | |||

STATUS current | STATUS current | |||

DESCRIPTION | DESCRIPTION | |||

"Type-P-One-way-pdv-refmin-Skewness" | "Type-P-One-way-pdv-refmin-Skewness" | |||

REFERENCE | REFERENCE "RFC 6049, Section 6.1.4." | |||

"Reference "RFCyyyy, section 6.1.4." | ::= { ianaIppmMetrics 81 } | |||

-- RFC Ed.: replace yyyy with actual RFC number & remove this | ||||

note | ||||

::= { ianaIppmMetrics nn } -- IANA assigns nn | ||||

ietfCompositeOneWayPdvRefminQtil OBJECT-IDENTITY | ietfCompositeOneWayPdvRefminQtil OBJECT-IDENTITY | |||

STATUS current | STATUS current | |||

DESCRIPTION | DESCRIPTION | |||

"Type-P-Composite-One-way-pdv-refmin-quantile-a" | "Type-P-Composite-One-way-pdv-refmin-quantile-a" | |||

REFERENCE | REFERENCE "RFC 6049, Section 6.1.5.1." | |||

"Reference "RFCyyyy, section 6.1.5.1." | ::= { ianaIppmMetrics 82 } | |||

-- RFC Ed.: replace yyyy with actual RFC number & remove this | ||||

note | ||||

::= { ianaIppmMetrics nn } -- IANA assigns nn | ||||

ietfCompositeOneWayPdvRefminNPA OBJECT-IDENTITY | ietfCompositeOneWayPdvRefminNPA OBJECT-IDENTITY | |||

STATUS current | STATUS current | |||

DESCRIPTION | DESCRIPTION | |||

"Type-P-One-way-Composite-pdv-refmin-NPA" | "Type-P-One-way-Composite-pdv-refmin-NPA" | |||

REFERENCE | REFERENCE "RFC 6049, Section 6.1.5.2." | |||

"Reference "RFCyyyy, section 6.1.5.2." | ::= { ianaIppmMetrics 83 } | |||

-- RFC Ed.: replace yyyy with actual RFC number & remove this | ||||

note | ||||

::= { ianaIppmMetrics nn } -- IANA assigns nn | ||||

9. Contributors and Acknowledgements | 9. Contributors and Acknowledgements | |||

The following people have contributed useful ideas, suggestions, or | The following people have contributed useful ideas, suggestions, or | |||

the text of sections that have been incorporated into this memo: | the text of sections that have been incorporated into this memo: | |||

- Phil Chimento <vze275m9@verizon.net> | - Phil Chimento <vze275m9@verizon.net> | |||

- Reza Fardid <RFardid@cariden.com> | - Reza Fardid <RFardid@cariden.com> | |||

skipping to change at page 29, line 17 | skipping to change at page 28, line 45 | |||

10.2. Informative References | 10.2. Informative References | |||

[RFC5474] Duffield, N., Chiou, D., Claise, B., Greenberg, A., | [RFC5474] Duffield, N., Chiou, D., Claise, B., Greenberg, A., | |||

Grossglauser, M., and J. Rexford, "A Framework for Packet | Grossglauser, M., and J. Rexford, "A Framework for Packet | |||

Selection and Reporting", RFC 5474, March 2009. | Selection and Reporting", RFC 5474, March 2009. | |||

[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation | [RFC5481] Morton, A. and B. Claise, "Packet Delay Variation | |||

Applicability Statement", RFC 5481, March 2009. | Applicability Statement", RFC 5481, March 2009. | |||

[Stats] McGraw-Hill NY NY, "Introduction to the Theory of | [RFC5644] Stephan, E., Liang, L., and A. Morton, "IP Performance | |||

Statistics, 3rd Edition,", 1974. | Metrics (IPPM): Spatial and Multicast", RFC 5644, | |||

October 2009. | ||||

[STATS] Mood, A., Graybill, F., and D. Boes, "Introduction to the | ||||

Theory of Statistics, 3rd Edition", McGraw-Hill, New York, | ||||

NY, 1974. | ||||

[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", November 2007. | availability performance parameters", November 2007. | |||

[Y.1541] ITU-T Recommendation Y.1541, "Network Performance | [Y.1541] ITU-T Recommendation Y.1541, "Network Performance | |||

Objectives for IP-based Services", February 2006. | Objectives for IP-based Services", February 2006. | |||

Index | ||||

? | ||||

??? 14 | ||||

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 | |||

Email: acmorton@att.com | EMail: acmorton@att.com | |||

URI: http://home.comcast.net/~acmacm/ | URI: http://home.comcast.net/~acmacm/ | |||

Emile Stephan | ||||

France Telecom Division R&D | Stephan Emile | |||

France Telecom Orange | ||||

2 avenue Pierre Marzin | 2 avenue Pierre Marzin | |||

Lannion, F-22307 | Lannion, F-22307 | |||

France | France | |||

Phone: | EMail: emile.stephan@orange-ftgroup.com | |||

Fax: +33 2 96 05 18 52 | ||||

Email: emile.stephan@orange-ftgroup.com | ||||

URI: | ||||

End of changes. 184 change blocks. | ||||

478 lines changed or deleted | | 453 lines changed or added | ||

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