draft-ietf-ippm-spatial-composition-00.txt | draft-ietf-ippm-spatial-composition-01.txt | |||
---|---|---|---|---|

Network Working Group A. Morton | Network Working Group A. Morton | |||

Internet-Draft AT&T Labs | Internet-Draft AT&T Labs | |||

Expires: August 30, 2006 E. Stephan | Expires: December 26, 2006 E. Stephan | |||

France Telecom Division R&D | France Telecom Division R&D | |||

February 26, 2006 | June 24, 2006 | |||

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

draft-ietf-ippm-spatial-composition-00 | draft-ietf-ippm-spatial-composition-01 | |||

Status of this Memo | Status of this Memo | |||

By submitting this Internet-Draft, each author represents that any | By submitting this Internet-Draft, each author represents that any | |||

applicable patent or other IPR claims of which he or she is aware | applicable patent or other IPR claims of which he or she is aware | |||

have been or will be disclosed, and any of which he or she becomes | have been or will be disclosed, and any of which he or she becomes | |||

aware will be disclosed, in accordance with Section 6 of BCP 79. | aware will be disclosed, in accordance with Section 6 of BCP 79. | |||

Internet-Drafts are working documents of the Internet Engineering | Internet-Drafts are working documents of the Internet Engineering | |||

Task Force (IETF), its areas, and its working groups. Note that | Task Force (IETF), its areas, and its working groups. Note that | |||

skipping to change at page 1, line 35 | skipping to change at page 1, line 35 | |||

and may be updated, replaced, or obsoleted by other documents at any | and may be updated, replaced, or obsoleted by other documents at any | |||

time. It is inappropriate to use Internet-Drafts as reference | time. It is inappropriate to use Internet-Drafts as reference | |||

material or to cite them other than as "work in progress." | material or to cite them other than as "work in progress." | |||

The list of current Internet-Drafts can be accessed at | The list of current Internet-Drafts can be accessed at | |||

http://www.ietf.org/ietf/1id-abstracts.txt. | http://www.ietf.org/ietf/1id-abstracts.txt. | |||

The list of Internet-Draft Shadow Directories can be accessed at | The list of Internet-Draft Shadow Directories can be accessed at | |||

http://www.ietf.org/shadow.html. | http://www.ietf.org/shadow.html. | |||

This Internet-Draft will expire on August 30, 2006. | This Internet-Draft will expire on December 26, 2006. | |||

Copyright Notice | Copyright Notice | |||

Copyright (C) The Internet Society (2006). | Copyright (C) The Internet Society (2006). | |||

Abstract | Abstract | |||

This memo utilizes IPPM metrics that are applicable to both complete | This memo utilizes IPPM metrics that are applicable to both complete | |||

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

path metric from the sub-path metrics with some accuracy w.r.t. the | path metric from the sub-path metrics with some accuracy w.r.t. the | |||

skipping to change at page 2, line 23 | skipping to change at page 2, line 23 | |||

Table of Contents | Table of Contents | |||

1. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 4 | 1. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 4 | |||

2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 | 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 | |||

2.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 5 | 2.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 5 | |||

3. Scope, Application, and Terminology . . . . . . . . . . . . . 5 | 3. Scope, Application, and Terminology . . . . . . . . . . . . . 5 | |||

3.1. Scope of work . . . . . . . . . . . . . . . . . . . . . . 5 | 3.1. Scope of work . . . . . . . . . . . . . . . . . . . . . . 5 | |||

3.2. Application . . . . . . . . . . . . . . . . . . . . . . . 6 | 3.2. Application . . . . . . . . . . . . . . . . . . . . . . . 6 | |||

3.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 | 3.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6 | |||

4. One-way Delay Composition Metrics and Statistics . . . . . . . 7 | 4. One-way Delay Composed Metrics and Statistics . . . . . . . . 7 | |||

4.1. Name: | 4.1. Name: | |||

Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream . . . 7 | Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream . . . 7 | |||

4.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 7 | 4.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 7 | |||

4.1.2. Definition and Metric Units . . . . . . . . . . . . . 8 | 4.1.2. Definition and Metric Units . . . . . . . . . . . . . 8 | |||

4.1.3. Discussion and other details . . . . . . . . . . . . . 8 | 4.1.3. Discussion and other details . . . . . . . . . . . . . 8 | |||

4.1.4. Mean Statistic . . . . . . . . . . . . . . . . . . . . 8 | 4.1.4. Mean Statistic . . . . . . . . . . . . . . . . . . . . 9 | |||

4.1.5. Composition Relationship: Sum of Means . . . . . . . . 9 | 4.1.5. Composition Function: Sum of Means . . . . . . . . . . 9 | |||

4.1.6. Statement of Conjecture . . . . . . . . . . . . . . . 9 | 4.1.6. Statement of Conjecture . . . . . . . . . . . . . . . 9 | |||

4.1.7. Justification of Composite Relationship . . . . . . . 9 | 4.1.7. Justification of the Composition Function . . . . . . 10 | |||

4.1.8. Sources of Error . . . . . . . . . . . . . . . . . . . 10 | 4.1.8. Sources of Deviation from the Ground Truth . . . . . . 10 | |||

4.1.9. Specific cases where the conjecture might fail . . . . 10 | 4.1.9. Specific cases where the conjecture might fail . . . . 10 | |||

4.1.10. Application of Measurement Methodology . . . . . . . . 10 | 4.1.10. Application of Measurement Methodology . . . . . . . . 10 | |||

5. Loss Metrics and Statistics . . . . . . . . . . . . . . . . . 11 | 5. Loss Metrics and Statistics . . . . . . . . . . . . . . . . . 11 | |||

5.1. Name: | 5.1. Name: | |||

Type-P-One-way-Packet-Loss-Poisson/Periodic-Stream . . . . 11 | Type-P-One-way-Packet-Loss-Poisson/Periodic-Stream . . . . 11 | |||

5.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 11 | 5.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 11 | |||

5.1.2. Definition and Metric Units . . . . . . . . . . . . . 11 | 5.1.2. Definition and Metric Units . . . . . . . . . . . . . 11 | |||

5.1.3. Discussion and other details . . . . . . . . . . . . . 11 | 5.1.3. Discussion and other details . . . . . . . . . . . . . 11 | |||

5.1.4. Statistic: | 5.1.4. Statistic: | |||

Type-P-One-way-Packet-Loss-Empirical-Probability . . . 11 | Type-P-One-way-Packet-Loss-Empirical-Probability . . . 11 | |||

5.1.5. Composition Relationship: Composition of Empirical | 5.1.5. Composition Function: Composition of Empirical | |||

Probabilities . . . . . . . . . . . . . . . . . . . . 11 | Probabilities . . . . . . . . . . . . . . . . . . . . 12 | |||

5.1.6. Statement of Conjecture . . . . . . . . . . . . . . . 12 | 5.1.6. Statement of Conjecture . . . . . . . . . . . . . . . 12 | |||

5.1.7. Justification of Composite Relationship . . . . . . . 12 | 5.1.7. Justification of the Composition Function . . . . . . 12 | |||

5.1.8. Sources of Error . . . . . . . . . . . . . . . . . . . 12 | 5.1.8. Sources of Deviation from the Ground Truth . . . . . . 12 | |||

5.1.9. Specific cases where the conjecture might fail . . . . 12 | 5.1.9. Specific cases where the conjecture might fail . . . . 13 | |||

5.1.10. Application of Measurement Methodology . . . . . . . . 13 | 5.1.10. Application of Measurement Methodology . . . . . . . . 13 | |||

6. Delay Variation Metrics and Statistics . . . . . . . . . . . . 13 | 6. Delay Variation Metrics and Statistics . . . . . . . . . . . . 13 | |||

6.1. Name: | 6.1. Name: | |||

Type-P-One-way-ipdv-refmin-Poisson/Periodic-Stream . . . . 13 | Type-P-One-way-ipdv-refmin-Poisson/Periodic-Stream . . . . 14 | |||

6.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 13 | 6.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 14 | |||

6.1.2. Definition and Metric Units . . . . . . . . . . . . . 14 | 6.1.2. Definition and Metric Units . . . . . . . . . . . . . 14 | |||

6.1.3. Discussion and other details . . . . . . . . . . . . . 14 | 6.1.3. Discussion and other details . . . . . . . . . . . . . 15 | |||

6.1.4. Statistics: Mean, Variance, Skewness, Quanitle . . . . 14 | 6.1.4. Statistics: Mean, Variance, Skewness, Quanitle . . . . 15 | |||

6.1.5. Composition Relationships: . . . . . . . . . . . . . . 15 | 6.1.5. Composition Functions: . . . . . . . . . . . . . . . . 16 | |||

6.1.6. Statement of Conjecture . . . . . . . . . . . . . . . 16 | 6.1.6. Statement of Conjecture . . . . . . . . . . . . . . . 16 | |||

6.1.7. Justification of Composite Relationship . . . . . . . 16 | 6.1.7. Justification of the Composition Function . . . . . . 16 | |||

6.1.8. Sources of Error . . . . . . . . . . . . . . . . . . . 16 | 6.1.8. Sources of Deviation from the Ground Truth . . . . . . 16 | |||

6.1.9. Specific cases where the conjecture might fail . . . . 16 | 6.1.9. Specific cases where the conjecture might fail . . . . 16 | |||

6.1.10. Application of Measurement Methodology . . . . . . . . 16 | 6.1.10. Application of Measurement Methodology . . . . . . . . 16 | |||

7. Other Metrics and Statistics: One-way Combined Metric . . . . 16 | 7. Other Metrics and Statistics: One-way Combined Metric . . . . 16 | |||

7.1. Metric Name: . . . . . . . . . . . . . . . . . . . . . . . 16 | 7.1. Metric Name: . . . . . . . . . . . . . . . . . . . . . . . 16 | |||

7.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 16 | 7.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 16 | |||

7.1.2. Definition and Metric Units . . . . . . . . . . . . . 16 | 7.1.2. Definition and Metric Units . . . . . . . . . . . . . 17 | |||

7.1.3. Discussion and other details . . . . . . . . . . . . . 17 | 7.1.3. Discussion and other details . . . . . . . . . . . . . 17 | |||

7.1.4. Type-P-One-way-Combo-subpathes-stream . . . . . . . . 17 | 7.1.4. Type-P-One-way-Combo-subpathes-stream . . . . . . . . 17 | |||

7.1.5. Type-P-One-way-composition . . . . . . . . . . . . . . 17 | 7.1.5. Type-P-One-way-composition . . . . . . . . . . . . . . 18 | |||

7.1.6. Type-P-One-way-composition . . . . . . . . . . . . . . 17 | 7.1.6. Type-P-One-way-composition . . . . . . . . . . . . . . 18 | |||

7.1.7. Statement of Conjecture . . . . . . . . . . . . . . . 18 | 7.1.7. Statement of Conjecture . . . . . . . . . . . . . . . 18 | |||

7.1.8. Justification of Composite Relationship . . . . . . . 18 | 7.1.8. Justification of Composite Relationship . . . . . . . 18 | |||

7.1.9. Sources of Error . . . . . . . . . . . . . . . . . . . 18 | 7.1.9. Sources of Error . . . . . . . . . . . . . . . . . . . 19 | |||

7.1.10. Specific cases where the conjecture might fail . . . . 18 | 7.1.10. Specific cases where the conjecture might fail . . . . 19 | |||

7.1.11. Application of Measurement Methodology . . . . . . . . 18 | 7.1.11. Application of Measurement Methodology . . . . . . . . 19 | |||

8. Security Considerations . . . . . . . . . . . . . . . . . . . 19 | 8. Security Considerations . . . . . . . . . . . . . . . . . . . 19 | |||

8.1. Denial of Service Attacks . . . . . . . . . . . . . . . . 19 | 8.1. Denial of Service Attacks . . . . . . . . . . . . . . . . 19 | |||

8.2. User Data Confidentiality . . . . . . . . . . . . . . . . 19 | 8.2. User Data Confidentiality . . . . . . . . . . . . . . . . 19 | |||

8.3. Interference with the metrics . . . . . . . . . . . . . . 19 | 8.3. Interference with the metrics . . . . . . . . . . . . . . 20 | |||

9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19 | 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 | |||

10. Security Considerations . . . . . . . . . . . . . . . . . . . 20 | 10. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 20 | |||

11. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 20 | 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21 | |||

12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21 | 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21 | |||

13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21 | 12.1. Normative References . . . . . . . . . . . . . . . . . . . 21 | |||

13.1. Normative References . . . . . . . . . . . . . . . . . . . 21 | 12.2. Informative References . . . . . . . . . . . . . . . . . . 22 | |||

13.2. Informative References . . . . . . . . . . . . . . . . . . 21 | Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 23 | |||

Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22 | Intellectual Property and Copyright Statements . . . . . . . . . . 24 | |||

Intellectual Property and Copyright Statements . . . . . . . . . . 23 | ||||

1. Contributors | 1. Contributors | |||

Thus far, the following people have contributed useful ideas, | Thus far, the following people have contributed useful ideas, | |||

suggestions, or the text of sections that have been incorporated into | suggestions, or the text of sections that have been incorporated into | |||

this memo: | this memo: | |||

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

- Reza Fardid <RFardid@Covad.COM> | - Reza Fardid <RFardid@Covad.COM> | |||

skipping to change at page 4, line 29 | skipping to change at page 4, line 29 | |||

- Al Morton <acmorton@att.com> | - Al Morton <acmorton@att.com> | |||

- Emile Stephan <emile.stephan@francetelecom.com> | - Emile Stephan <emile.stephan@francetelecom.com> | |||

- Lei Liang <L.Liang@surrey.ac.uk> | - Lei Liang <L.Liang@surrey.ac.uk> | |||

2. Introduction | 2. Introduction | |||

The IPPM framework RFC 2330 [RFC2330] describes two forms of metric | The IPPM framework RFC 2330 [RFC2330] describes two forms of metric | |||

composition, spatial and temporal. The new composition framework | composition, spatial and temporal. The new composition framework | |||

[FRMWK] expands and further qualifies these original forms into three | [I-D.ietf-ippm-framework-compagg] expands and further qualifies these | |||

categories. This memo describes Spatial Composition, one of the | original forms into three categories. This memo describes Spatial | |||

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

framework. | the composition framework. | |||

Spatial composition encompasses the definition of performance metrics | Spatial composition encompasses the definition of performance metrics | |||

that are applicable to a complete path, based on metrics collected on | that are applicable to a complete path, based on metrics collected on | |||

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

The purpose of this memo is to define relationships that yield the | The main purpose of this memo is to define the deterministic | |||

complete path metrics using metrics of the sub-paths. The | functions that yield the complete path metrics using metrics of the | |||

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

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

methods. | ||||

The relationships may involve conjecture, and [RFC2330] lists four | The relationships may involve conjecture, and [RFC2330] lists four | |||

points that the metric definitions should include: | points that the metric definitions should include: | |||

o the specific conjecture applied to the metric, | o the specific conjecture applied to the metric, | |||

o a justification of the practical utility of the composition in | o a justification of the practical utility of the composition in | |||

terms of making accurate measurements of the metric on the path, | terms of making accurate measurements of the metric on the path, | |||

o a justification of the usefulness of the composition in terms of | o a justification of the usefulness of the composition in terms of | |||

making analysis of the path using A-frame concepts more effective, | making analysis of the path using A-frame concepts more effective, | |||

skipping to change at page 5, line 18 | skipping to change at page 5, line 18 | |||

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

RFC 2330 also gives an example where a conjecture that the delay of a | RFC 2330 also gives an example where a conjecture that the delay of a | |||

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

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

relevant to those who wish to assess the performance of an Inter- | relevant to those who wish to assess the performance of an Inter- | |||

domain path without direct measurement, and the performance estimate | domain path without direct measurement, and the performance estimate | |||

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

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

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

metrics are useful, with knowledge of the circumstances where the | are useful, with knowledge of the circumstances where the | |||

relationships are/are not applicable. For example, we would not | relationships are/are not applicable. For example, we would not | |||

expect that delay singletons from each sub-path would sum to produce | expect that delay singletons from each sub-path would sum to produce | |||

an accurate estimate of a delay singleton for the complete path | an accurate estimate of a delay singleton for the complete path | |||

(unless all the delays were essentially constant - very unlikely). | (unless all the delays were essentially constant - very unlikely). | |||

However, other delay statistics (based on a reasonable sample size) | However, other delay statistics (based on a reasonable sample size) | |||

may have a sufficiently large set of circumstances where they are | may have a sufficiently large set of circumstances where they are | |||

applicable. | applicable. | |||

2.1. Motivation | 2.1. Motivation | |||

One-way metrics defined in other IPPM RFCs all assume that the | One-way metrics defined in other IPPM RFCs all assume that the | |||

measurement can be practically carried out between the source and the | measurement can be practically carried out between the source and the | |||

destination of the interest. Sometimes there are reasons that the | destination of the interest. Sometimes there are reasons that the | |||

measurement can not be executed from the source to the destination. | measurement can not be executed from the source to the destination. | |||

For instance, the measurement path may cross several independent | For instance, the measurement path may cross several independent | |||

domains that have conflicting policies, measurement tools and | domains that have conflicting policies, measurement tools and | |||

methods, and measurement time slot assignment. The solution then may | methods, and measurement time assignment. The solution then may be | |||

be the composition of several sub-path measurements. That means each | the composition of several sub-path measurements. This means each | |||

domain performs the One-way measurement on a sub path between two | domain performs the One-way measurement on a sub path between two | |||

nodes that are involved in the complete path following its own | nodes that are involved in the complete path following its own | |||

policy, using its own measurement tools and methods, and within its | policy, using its own measurement tools and methods, and using its | |||

own measurement time slot. Under the appropriate conditions, one can | own measurement timing. Under the appropriate conditions, one can | |||

combine the sub-path One-way metric results to estimate the complete | combine the sub-path One-way metric results to estimate the complete | |||

path One-way measurement metric with some accuracy. | path One-way measurement metric with some degree of accuracy. | |||

3. Scope, Application, and Terminology | 3. Scope, Application, and Terminology | |||

3.1. Scope of work | 3.1. Scope of work | |||

For the primary IPPM metrics (currently Loss, Delay, and Delay | For the primary IPPM metrics of Loss, Delay, and Delay Variation, | |||

Variation), this memo gives a set of complete path metrics that can | this memo gives a set of complete path metrics that can be composed | |||

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

that the complete path metric may be composed from: | complete path metric may be composed from: | |||

o the same metric for each sub-path; | o the same metric for each sub-path; | |||

o multiple metrics for each sub-path (possibly one that is the same | o multiple metrics for each sub-path (possibly one that is the same | |||

as the complete path metric); | as the complete path metric); | |||

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

metric; | metric; | |||

o different measurement techniques like active and passive | o different measurement techniques like active and passive | |||

(recognizing that PSAMP WG will define capabilities to sample | (recognizing that PSAMP WG will define capabilities to sample | |||

packets to support measurement). | packets to support measurement). | |||

3.2. Application | 3.2. Application | |||

The new composition framework [FRMWK] requires the specification of | The new composition framework [I-D.ietf-ippm-framework-compagg] | |||

the applicable circumstances for each metric. In particular, the | requires the specification of the applicable circumstances for each | |||

application of Spatial Composition metrics are addressed as to | metric. In particular, the application of Spatial Composition | |||

whether the metric: | metrics are addressed as to whether the metric: | |||

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

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

Requires homogeneity of measurement methodologies, or can allow a | Requires homogeneity of measurement methodologies, or can allow a | |||

degree of flexibility (e.g., active or passive methods produce the | degree of flexibility (e.g., active or passive methods produce the | |||

"same" metric). Also, the applicable sending streams will be | "same" metric). Also, the applicable sending streams will be | |||

specified, such as Poisson, Periodic, or both. | specified, such as Poisson, Periodic, or both. | |||

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

skipping to change at page 7, line 18 | skipping to change at page 7, line 18 | |||

The complete path is the true path that a packet would follow as it | The complete path is the true path that a packet would follow as it | |||

traverses from the packet's Source to its Destination. | traverses from the packet's Source to its Destination. | |||

Complete path metric: | Complete path metric: | |||

The complete path metric is the Source to Destination metric that a | The complete path metric is the Source to Destination metric that a | |||

composed metric is estimating. A complete path metric represents the | composed metric is estimating. A complete path metric represents the | |||

ground-truth for a composed metric. | ground-truth for a composed metric. | |||

Composite Metric (or Composed Metric): | Composed Metric: | |||

A composite metric is type of metric that is derived from other | A composed metric is derived from other metrics principally by | |||

metrics principally by applying a composition relationship. | applying a composition function. | |||

Composition Relationship: | Composition Function: | |||

A composition relationship is a deterministic process applied to Sub- | A composition function is a deterministic process applied to Sub-path | |||

path metrics to derive another metric (such as a Composite metric). | metrics to derive another metric (such as a Composed metric). | |||

Sub-path: | Sub-path: | |||

A Sub-path is a portion of the complete path where at least the Sub- | A Sub-path is a portion of the complete path where at least the Sub- | |||

path Source and Destination hosts are constituents of the complete | path Source and Destination hosts are constituents of the complete | |||

path. We say that this sub-path is "involved" in the complete path. | path. We say that this sub-path is "involved" in the complete path. | |||

Sub-path metrics: | Sub-path metrics: | |||

A sub-path path metric is an element of the process to derive a | A sub-path path metric is an element of the process to derive a | |||

Composite metric, quantifying some aspect of the performance a | Composite metric, quantifying some aspect of the performance a | |||

particular sub-path from its Source to Destination. | particular sub-path from its Source to Destination. | |||

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

4.1. Name: Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream | 4.1. Name: Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream | |||

This metric is a necessary element of Delay Composition metrics, and | This metric is a necessary element of Delay Composition metrics, and | |||

its definition does not formally exist elsewhere in IPPM literature. | its definition does not formally exist elsewhere in IPPM literature. | |||

4.1.1. Metric Parameters: | 4.1.1. Metric Parameters: | |||

o Src, the IP address of a host + Dst, the IP address of a host | o Src, the IP address of a host + Dst, the IP address of a host | |||

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

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

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

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

Periodic Streams) | Periodic Streams) | |||

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

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

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

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

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

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

is not truncated. | ||||

4.1.2. Definition and Metric Units | 4.1.2. Definition and Metric Units | |||

Using the parameters above, we obtain the value of Type-P-One-way- | Using the parameters above, we obtain the value of Type-P-One-way- | |||

Delay singleton as per RFC 2679 [RFC2679]. | Delay singleton as per RFC 2679 [RFC2679]. | |||

For each packet [i] that has a finite One-way Delay (in other words, | For each packet [i] that has a finite One-way Delay (in other words, | |||

excluding packets which have undefined, or infinite one-way delay): | excluding packets which have undefined one-way delay): | |||

Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream[i] = | Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream[i] = | |||

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

4.1.3. Discussion and other details | 4.1.3. Discussion and other details | |||

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

mean statistic. This avoids the need to include lost packets in the | sample mean statistic. This resolves the problem of including lost | |||

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

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

can only assign some very large value. | systems can only assign some very large value). | |||

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

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

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

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

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

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

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

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

4.1.4. Mean Statistic | 4.1.4. Mean Statistic | |||

We add the following parameter: | We add the following parameter: | |||

o N, the total number of packets received at Dst (sent between T0 | o N, the total number of packets received at Dst (sent between T0 | |||

and Tf) | and Tf) | |||

and define | and define | |||

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

N | N | |||

--- | --- | |||

1 \ | 1 \ | |||

- * > (FiniteDelay [i]) | - * > (FiniteDelay [i]) | |||

N / | N / | |||

--- | --- | |||

i = 1 | i = 1 | |||

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

skipping to change at page 9, line 15 | skipping to change at page 9, line 28 | |||

N | N | |||

--- | --- | |||

1 \ | 1 \ | |||

- * > (FiniteDelay [i]) | - * > (FiniteDelay [i]) | |||

N / | N / | |||

--- | --- | |||

i = 1 | i = 1 | |||

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

4.1.5. Composition Relationship: Sum of Means | 4.1.5. Composition Function: Sum of Means | |||

The Type-P-Finite--Composite-One-way-Delay-Mean, or CompMeanDelay for | The Type-P-Finite--Composite-One-way-Delay-Mean, or CompMeanDelay for | |||

the complete Source to Destination path can be calculated from sum of | the complete Source to Destination path can be calculated from sum of | |||

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

o S, the number of sub-paths involved in the complete Src-Dst path. | o S, the number of sub-paths involved in the complete Src-Dst path. | |||

Then the | Then the | |||

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

skipping to change at page 9, line 37 | skipping to change at page 10, line 5 | |||

CompMeanDelay = (1/S)Sum(from i=1 to S, MeanDelay[i]) | CompMeanDelay = (1/S)Sum(from i=1 to S, MeanDelay[i]) | |||

4.1.6. Statement of Conjecture | 4.1.6. Statement of Conjecture | |||

The mean of a sufficiently large stream of packets measured on each | The mean of a sufficiently large stream of packets measured on each | |||

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

true mean of the delay distribution (and the distributions themselves | true mean of the delay distribution (and the distributions themselves | |||

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

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

4.1.7. Justification of Composite Relationship | 4.1.7. Justification of the Composition Function | |||

It is sometimes impractical to conduct active measurements between | It is sometimes impractical to conduct active measurements between | |||

every Src-Dst pair. For example, it may not be possible to collect | every Src-Dst pair. For example, it may not be possible to collect | |||

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

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

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

access link may be understood well-enough to permit use of a small | access link may be understood well-enough to permit use of a small | |||

sample size/rate, while a larger sample size/rate may be used on | sample size/rate, while a larger sample size/rate may be used on | |||

other sub-paths. | other sub-paths. | |||

Also, since measurement operations have a real monetary cost, there | Also, since measurement operations have a real monetary cost, there | |||

is value in re-using measurements where they are applicable, rather | is value in re-using measurements where they are applicable, rather | |||

than launching new measurements for every possible source-destination | than launching new measurements for every possible source-destination | |||

pair. | pair. | |||

4.1.8. Sources of Error | 4.1.8. Sources of Deviation from the Ground Truth | |||

The measurement packets, each having source and destination addresses | The measurement packets, each having source and destination addresses | |||

intended for collection at edges of the sub-path, may take a | intended for collection at edges of the sub-path, may take a | |||

different specific path through the network equipment and parallel | different specific path through the network equipment and parallel | |||

exchanges than packets with the source and destination addresses of | exchanges than packets with the source and destination addresses of | |||

the complete path. Therefore, the sub-path measurements may differ | the complete path. Therefore, the sub-path measurements may differ | |||

from the performance experienced by packets on the complete path. | from the performance experienced by packets on the complete path. | |||

Multiple measurements employing sufficient sub-path address pairs | Multiple measurements employing sufficient sub-path address pairs | |||

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

skipping to change at page 11, line 31 | skipping to change at page 11, line 45 | |||

o L, either zero or one, where L=1 indicates loss and L=0 indicates | o L, either zero or one, where L=1 indicates loss and L=0 indicates | |||

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

5.1.3. Discussion and other details | 5.1.3. Discussion and other details | |||

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

Given the following stream parameter | Given the following stream parameter | |||

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

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

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

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

Ep = (1/M)Sum(from i=1 to M, L[i]) | ||||

Ep = (1/N)Sum(from i=1 to N, L[i]) | where all packets i= 1 through M have a value for L. | |||

where all packets i= 1 through N have a value for L. | ||||

5.1.5. Composition Relationship: Composition of Empirical Probabilities | 5.1.5. Composition Function: Composition of Empirical Probabilities | |||

The Type-P-One-way-Composite-Packet-Loss-Empirical-Probability, or | The Type-P-One-way-Composite-Packet-Loss-Empirical-Probability, or | |||

CompEp for the complete Source to Destination path can be calculated | CompEp for the complete Source to Destination path can be calculated | |||

by combining Ep of all its constituent sub-paths (Ep1, Ep2, Ep3, ... | by combining Ep of all its constituent sub-paths (Ep1, Ep2, Ep3, ... | |||

Epn) as | Epn) as | |||

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

1 - {(1 - Ep1) x (1 - Ep2) x (1 - Ep3) x ... x (1 - Epn)} | 1 - {(1 - Ep1) x (1 - Ep2) x (1 - Ep3) x ... x (1 - Epn)} | |||

5.1.6. Statement of Conjecture | 5.1.6. Statement of Conjecture | |||

The empirical probability of loss calculated on a sufficiently large | The empirical probability of loss calculated on a sufficiently large | |||

stream of packets measured on each sub-path during the interval [T, | stream of packets measured on each sub-path during the interval [T, | |||

Tf] will be representative of the true loss probability (and the | Tf] will be representative of the true loss probability (and the | |||

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

sub-path probabilities may be combined to produce an estimate of the | sub-path probabilities may be combined to produce an estimate of the | |||

complete path loss probability. | complete path loss probability. | |||

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

It is sometimes impractical to conduct active measurements between | It is sometimes impractical to conduct active measurements between | |||

every Src-Dst pair. For example, it may not be possible to collect | every Src-Dst pair. For example, it may not be possible to collect | |||

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

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

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

access link may be understood well-enough to permit use of a small | access link may be understood well-enough to permit use of a small | |||

sample size/rate, while a larger sample size/rate may be used on | sample size/rate, while a larger sample size/rate may be used on | |||

other sub-paths. | other sub-paths. | |||

Also, since measurement operations have a real monetary cost, there | Also, since measurement operations have a real monetary cost, there | |||

is value in re-using measurements where they are applicable, rather | is value in re-using measurements where they are applicable, rather | |||

than launching new measurements for every possible source-destination | than launching new measurements for every possible source-destination | |||

pair. | pair. | |||

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

The measurement packets, each having source and destination addresses | The measurement packets, each having source and destination addresses | |||

intended for collection at edges of the sub-path, may take a | intended for collection at edges of the sub-path, may take a | |||

different specific path through the network equipment and parallel | different specific path through the network equipment and parallel | |||

exchanges than packets with the source and destination addresses of | exchanges than packets with the source and destination addresses of | |||

the complete path. Therefore, the sub-path measurements may differ | the complete path. Therefore, the sub-path measurements may differ | |||

from the performance experienced by packets on the complete path. | from the performance experienced by packets on the complete path. | |||

Multiple measurements employing sufficient sub-path address pairs | Multiple measurements employing sufficient sub-path address pairs | |||

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

skipping to change at page 15, line 43 | skipping to change at page 16, line 21 | |||

--- | --- | |||

i = 1 | i = 1 | |||

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

/ \ | / \ | |||

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

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

We define the Quantile of the IPDVRefMin sample as the value where | We define the Quantile of the IPDVRefMin sample as the value where | |||

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

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

The Type-P-One-way-Composite-ipdv-refmin-<something> for the complete | The Type-P-One-way-Composite-ipdv-refmin-<something> for the complete | |||

Source to Destination path can be calculated by combining statistics | Source to Destination path can be calculated by combining statistics | |||

of all the constituent sub-paths in the following process: | of all the constituent sub-paths in the following process: | |||

< to be provided > | < see [Y.1541] > | |||

6.1.6. Statement of Conjecture | 6.1.6. Statement of Conjecture | |||

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

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

6.1.9. Specific cases where the conjecture might fail | 6.1.9. Specific cases where the conjecture might fail | |||

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

7. Other Metrics and Statistics: One-way Combined Metric | 7. Other Metrics and Statistics: One-way Combined Metric | |||

This definition may be the common part for the definition of "Loss | This definition may be the common part for the definition of "Loss | |||

Metrics/Statistics" and for the definition of "One-way Delay | Metrics/Statistics" and for the definition of "One-way Delay | |||

Composition Metrics and Statistics". | Composition Metrics and Statistics". | |||

skipping to change at page 20, line 5 | skipping to change at page 20, line 28 | |||

To discourage the kind of interference mentioned above, packet | To discourage the kind of interference mentioned above, packet | |||

interference checks, such as cryptographic hash, may be used. | interference checks, such as cryptographic hash, may be used. | |||

9. IANA Considerations | 9. IANA Considerations | |||

Metrics defined in this memo will be registered in the IANA IPPM | Metrics defined in this memo will be registered in the IANA IPPM | |||

METRICS REGISTRY as described in initial version of the registry RFC | METRICS REGISTRY as described in initial version of the registry RFC | |||

4148 [RFC4148]. | 4148 [RFC4148]. | |||

10. Security Considerations | 10. Open Issues | |||

11. Open Issues | ||||

>>>>>>>>>>>>Open issue: | >>>>>>>>>>>>Open issue: | |||

What is the relationship between the decomposition and composition | What is the relationship between the decomposition and composition | |||

metrics? Should we put both kinds in one draft to make up a | metrics? Should we put both kinds in one draft to make up a | |||

framework? The motivation of decomposition is as follows: | framework? The motivation of decomposition is as follows: | |||

The One-way measurement can provide result to show what the network | The One-way measurement can provide result to show what the network | |||

performance between two end hosts is and whether it meets operator | performance between two end hosts is and whether it meets operator | |||

expectations or not. It cannot provide further information to | expectations or not. It cannot provide further information to | |||

skipping to change at page 20, line 29 | skipping to change at page 21, line 4 | |||

and the destination. For instance, if the network performance is not | and the destination. For instance, if the network performance is not | |||

acceptable in terms of the One-way measurement, in which part of the | acceptable in terms of the One-way measurement, in which part of the | |||

network the engineers should put their efforts. This question can to | network the engineers should put their efforts. This question can to | |||

be answered by decompose the One-way measurement to sub-path | be answered by decompose the One-way measurement to sub-path | |||

measurement to investigate the performance of different part of the | measurement to investigate the performance of different part of the | |||

network. | network. | |||

Editor's Questions for clarification: What additional information | Editor's Questions for clarification: What additional information | |||

would be provided to the decomposition process, beyond the | would be provided to the decomposition process, beyond the | |||

measurement of the complete path? | measurement of the complete path? | |||

Is the decomposition described above intended to estimate a metric | Is the decomposition described above intended to estimate a metric | |||

for some/all disjoint sub-paths involved in the complete path? | for some/all disjoint sub-paths involved in the complete path? | |||

>>>>>>>>>>>>>>>>>>RESOLUTION: treat this topic in a seperate memo | ||||

>>>>>>>>>>>>>>>>>>> | >>>>>>>>>>>>>>>>>>> | |||

>>>>>>>>>>>>>>>>>>>OPEN Issue | >>>>>>>>>>>>>>>>>>>OPEN Issue | |||

Section 7 defines a new type of metric, a "combination" of metrics | Section 7 defines a new type of metric, a "combination" of metrics | |||

for one-way delay and packet loss. The purpose of this metric is to | for one-way delay and packet loss. The purpose of this metric is to | |||

link these two primary metrics in a convenient way. | link these two primary metrics in a convenient way. | |||

Readers are asked to comment on the efficiency of the combination | Readers are asked to comment on the efficiency of the combination | |||

metric. | metric. | |||

>>>>>>>>>>>>>>>>>RESOLUTION: If a delay singleton is recorded as | ||||

having "undefined" delay when the packet does not arrive within the | ||||

waiting time Tmax, then this information is sufficient to determine | ||||

the fraction of lost packets in the sample, and the additional loss | ||||

indication of this combo is not needed. | ||||

>>>>>>>>>>>>>>>>>> | >>>>>>>>>>>>>>>>>> | |||

>>>>>>>>>>>>>>>>> OPEN Issue | >>>>>>>>>>>>>>>>> OPEN Issue | |||

How can we introduce multicast metrics here, without causing too much | How can we introduce multicast metrics here, without causing too much | |||

confusion? Should the multicast version of this draft wait until the | confusion? Should the multicast version of this draft wait until the | |||

Unicast concepts are stable (or maybe appear in a separate draft)? | Unicast concepts are stable (or maybe appear in a separate draft)? | |||

12. Acknowledgements | >>>>>>>>>>>>>>>>RESOLUTION: Yes and Yes. | |||

13. References | 11. Acknowledgements | |||

13.1. Normative References | 12. References | |||

[FRMWK] Morton, A. and S.Van Den Berghe, "Framework for Metric | 12.1. Normative References | |||

Composition", February 2006. | ||||

[I-D.ietf-ippm-framework-compagg] | ||||

Morton, A. and S. Berghe, "Framework for Metric | ||||

Composition", draft-ietf-ippm-framework-compagg-00 (work | ||||

in progress), February 2006. | ||||

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate | [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate | |||

Requirement Levels", BCP 14, RFC 2119, March 1997. | Requirement Levels", BCP 14, RFC 2119, March 1997. | |||

[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, | [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, | |||

"Framework for IP Performance Metrics", RFC 2330, | "Framework for IP Performance Metrics", RFC 2330, | |||

May 1998. | May 1998. | |||

[RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way | [RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way | |||

Delay Metric for IPPM", RFC 2679, September 1999. | Delay Metric for IPPM", RFC 2679, September 1999. | |||

[RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way | [RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way | |||

Packet Loss Metric for IPPM", RFC 2680, September 1999. | Packet Loss Metric for IPPM", RFC 2680, September 1999. | |||

[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation | ||||

Metric for IP Performance Metrics (IPPM)", RFC 3393, | ||||

November 2002. | ||||

[RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network | [RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network | |||

performance measurement with periodic streams", RFC 3432, | performance measurement with periodic streams", RFC 3432, | |||

November 2002. | November 2002. | |||

[RFC4148] Stephan, E., "IP Performance Metrics (IPPM) Metrics | [RFC4148] Stephan, E., "IP Performance Metrics (IPPM) Metrics | |||

Registry", BCP 108, RFC 4148, August 2005. | Registry", BCP 108, RFC 4148, August 2005. | |||

13.2. Informative References | 12.2. Informative References | |||

[I-D.stephan-ippm-multimetrics] | [I-D.stephan-ippm-multimetrics] | |||

Stephan, E., "IP Performance Metrics (IPPM) for spatial | Stephan, E., "IP Performance Metrics (IPPM) for spatial | |||

and multicast", draft-stephan-ippm-multimetrics-02 (work | and multicast", draft-stephan-ippm-multimetrics-02 (work | |||

in progress), October 2005. | in progress), October 2005. | |||

[Y.1540] ITU-T Recommendation Y.1540, "Internet protocol data | [Y.1540] ITU-T Recommendation Y.1540, "Internet protocol data | |||

communication service - IP packet transfer and | communication service - IP packet transfer and | |||

availability performance parameters", December 2002. | availability performance parameters", December 2002. | |||

[Y.1541] ITU-T Recommendation Y.1540, "Network Performance | ||||

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

Authors' Addresses | Authors' Addresses | |||

Al Morton | Al Morton | |||

AT&T Labs | AT&T Labs | |||

200 Laurel Avenue South | 200 Laurel Avenue South | |||

Middletown,, NJ 07748 | Middletown,, NJ 07748 | |||

USA | USA | |||

Phone: +1 732 420 1571 | Phone: +1 732 420 1571 | |||

Fax: +1 732 368 1192 | Fax: +1 732 368 1192 | |||

End of changes. 57 change blocks. | ||||

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