draft-ietf-ippm-spatial-composition-11.txt   draft-ietf-ippm-spatial-composition-12.txt 
Network Working Group A. Morton Network Working Group A. Morton
Internet-Draft AT&T Labs Internet-Draft AT&T Labs
Intended status: Standards Track E. Stephan Intended status: Standards Track E. Stephan
Expires: October 16, 2010 France Telecom Division R&D Expires: December 1, 2010 France Telecom Division R&D
April 14, 2010 May 30, 2010
Spatial Composition of Metrics Spatial Composition of Metrics
draft-ietf-ippm-spatial-composition-11 draft-ietf-ippm-spatial-composition-12
Abstract Abstract
This memo utilizes IPPM metrics that are applicable to both complete This memo utilizes IP Performance Metrics that are applicable to both
paths and sub-paths, and defines relationships to compose a complete complete paths and sub-paths, and defines relationships to compose a
path metric from the sub-path metrics with some accuracy w.r.t. the complete path metric from the sub-path metrics with some accuracy
actual metrics. This is called Spatial Composition in RFC 2330. The w.r.t. the actual metrics. This is called Spatial Composition in RFC
memo refers to the Framework for Metric Composition, and provides 2330. The memo refers to the Framework for Metric Composition, and
background and motivation for combining metrics to derive others. provides background and motivation for combining metrics to derive
The descriptions of several composed metrics and statistics follow. others. The descriptions of several composed metrics and statistics
follow.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
In this memo, the characters "<=" should be read as "less than or In this memo, the characters "<=" should be read as "less than or
equal to" and ">=" as "greater than or equal to". equal to" and ">=" as "greater than or equal to".
skipping to change at page 1, line 46 skipping to change at page 1, line 47
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
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."
This Internet-Draft will expire on October 16, 2010. This Internet-Draft will expire on December 1, 2010.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 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
skipping to change at page 3, line 25 skipping to change at page 3, line 25
4.1. Name: Type-P . . . . . . . . . . . . . . . . . . . . . . . 8 4.1. Name: Type-P . . . . . . . . . . . . . . . . . . . . . . . 8
4.1.1. Metric Parameters . . . . . . . . . . . . . . . . . . 8 4.1.1. Metric Parameters . . . . . . . . . . . . . . . . . . 8
4.1.2. Definition and Metric Units . . . . . . . . . . . . . 9 4.1.2. Definition and Metric Units . . . . . . . . . . . . . 9
4.1.3. Discussion and other details . . . . . . . . . . . . . 9 4.1.3. Discussion and other details . . . . . . . . . . . . . 9
4.1.4. Statistic: . . . . . . . . . . . . . . . . . . . . . . 9 4.1.4. Statistic: . . . . . . . . . . . . . . . . . . . . . . 9
4.1.5. Composition Function . . . . . . . . . . . . . . . . . 9 4.1.5. Composition Function . . . . . . . . . . . . . . . . . 9
4.1.6. Statement of Conjecture and Assumptions . . . . . . . 9 4.1.6. Statement of Conjecture and Assumptions . . . . . . . 9
4.1.7. Justification of the Composition Function . . . . . . 10 4.1.7. Justification of the Composition Function . . . . . . 10
4.1.8. Sources of Deviation from the Ground Truth . . . . . . 10 4.1.8. Sources of Deviation from the Ground Truth . . . . . . 10
4.1.9. Specific cases where the conjecture might fail . . . . 11 4.1.9. Specific cases where the conjecture might fail . . . . 11
4.1.10. Application of Measurement Methodology . . . . . . . . 11 4.1.10. Application of Measurement Methodology . . . . . . . . 12
5. One-way Delay Composed Metrics and Statistics . . . . . . . . 12 5. One-way Delay Composed Metrics and Statistics . . . . . . . . 12
5.1. Name: 5.1. Name:
Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream . . . 12 Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream . . . 12
5.1.1. Metric Parameters . . . . . . . . . . . . . . . . . . 12 5.1.1. Metric Parameters . . . . . . . . . . . . . . . . . . 12
5.1.2. Definition and Metric Units . . . . . . . . . . . . . 12 5.1.2. Definition and Metric Units . . . . . . . . . . . . . 12
5.1.3. Discussion and other details . . . . . . . . . . . . . 12 5.1.3. Discussion and other details . . . . . . . . . . . . . 13
5.1.4. Statistic: . . . . . . . . . . . . . . . . . . . . . . 13 5.1.4. Statistic: . . . . . . . . . . . . . . . . . . . . . . 13
5.2. Name: Type-P-Finite-Composite-One-way-Delay-Mean . . . . . 13 5.2. Name: Type-P-Finite-Composite-One-way-Delay-Mean . . . . . 13
5.2.1. Metric Parameters . . . . . . . . . . . . . . . . . . 13 5.2.1. Metric Parameters . . . . . . . . . . . . . . . . . . 13
5.2.2. Definition and Metric Units of the Mean Statistic . . 13 5.2.2. Definition and Metric Units of the Mean Statistic . . 13
5.2.3. Discussion and other details . . . . . . . . . . . . . 14 5.2.3. Discussion and other details . . . . . . . . . . . . . 14
5.2.4. Statistic: . . . . . . . . . . . . . . . . . . . . . . 14 5.2.4. Statistic: . . . . . . . . . . . . . . . . . . . . . . 14
5.2.5. Composition Function: Sum of Means . . . . . . . . . . 14 5.2.5. Composition Function: Sum of Means . . . . . . . . . . 14
5.2.6. Statement of Conjecture and Assumptions . . . . . . . 14 5.2.6. Statement of Conjecture and Assumptions . . . . . . . 14
5.2.7. Justification of the Composition Function . . . . . . 14 5.2.7. Justification of the Composition Function . . . . . . 15
5.2.8. Sources of Deviation from the Ground Truth . . . . . . 14 5.2.8. Sources of Deviation from the Ground Truth . . . . . . 15
5.2.9. Specific cases where the conjecture might fail . . . . 15 5.2.9. Specific cases where the conjecture might fail . . . . 15
5.2.10. Application of Measurement Methodology . . . . . . . . 15 5.2.10. Application of Measurement Methodology . . . . . . . . 15
5.3. Name: Type-P-Finite-Composite-One-way-Delay-Minimum . . . 15 5.3. Name: Type-P-Finite-Composite-One-way-Delay-Minimum . . . 15
5.3.1. Metric Parameters . . . . . . . . . . . . . . . . . . 15 5.3.1. Metric Parameters . . . . . . . . . . . . . . . . . . 15
5.3.2. Definition and Metric Units of the Minimum 5.3.2. Definition and Metric Units of the Minimum
Statistic . . . . . . . . . . . . . . . . . . . . . . 15 Statistic . . . . . . . . . . . . . . . . . . . . . . 15
5.3.3. Discussion and other details . . . . . . . . . . . . . 16 5.3.3. Discussion and other details . . . . . . . . . . . . . 16
5.3.4. Statistic: . . . . . . . . . . . . . . . . . . . . . . 16 5.3.4. Statistic: . . . . . . . . . . . . . . . . . . . . . . 16
5.3.5. Composition Function: Sum of Minima . . . . . . . . . 16 5.3.5. Composition Function: Sum of Minima . . . . . . . . . 16
5.3.6. Statement of Conjecture and Assumptions . . . . . . . 16 5.3.6. Statement of Conjecture and Assumptions . . . . . . . 16
5.3.7. Justification of the Composition Function . . . . . . 16 5.3.7. Justification of the Composition Function . . . . . . 17
5.3.8. Sources of Deviation from the Ground Truth . . . . . . 16 5.3.8. Sources of Deviation from the Ground Truth . . . . . . 17
5.3.9. Specific cases where the conjecture might fail . . . . 17 5.3.9. Specific cases where the conjecture might fail . . . . 17
5.3.10. Application of Measurement Methodology . . . . . . . . 17 5.3.10. Application of Measurement Methodology . . . . . . . . 17
6. Loss Metrics and Statistics . . . . . . . . . . . . . . . . . 17 6. Loss Metrics and Statistics . . . . . . . . . . . . . . . . . 17
6.1. Type-P-Composite-One-way-Packet-Loss-Empirical-Probability 17 6.1. Type-P-Composite-One-way-Packet-Loss-Empirical-Probability 17
6.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 17 6.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 17
6.1.2. Definition and Metric Units . . . . . . . . . . . . . 17 6.1.2. Definition and Metric Units . . . . . . . . . . . . . 17
6.1.3. Discussion and other details . . . . . . . . . . . . . 17 6.1.3. Discussion and other details . . . . . . . . . . . . . 17
6.1.4. Statistic: 6.1.4. Statistic:
Type-P-One-way-Packet-Loss-Empirical-Probability . . . 17 Type-P-One-way-Packet-Loss-Empirical-Probability . . . 18
6.1.5. Composition Function: Composition of Empirical 6.1.5. Composition Function: Composition of Empirical
Probabilities . . . . . . . . . . . . . . . . . . . . 18 Probabilities . . . . . . . . . . . . . . . . . . . . 18
6.1.6. Statement of Conjecture and Assumptions . . . . . . . 18 6.1.6. Statement of Conjecture and Assumptions . . . . . . . 18
6.1.7. Justification of the Composition Function . . . . . . 18 6.1.7. Justification of the Composition Function . . . . . . 18
6.1.8. Sources of Deviation from the Ground Truth . . . . . . 18 6.1.8. Sources of Deviation from the Ground Truth . . . . . . 19
6.1.9. Specific cases where the conjecture might fail . . . . 18 6.1.9. Specific cases where the conjecture might fail . . . . 19
6.1.10. Application of Measurement Methodology . . . . . . . . 19 6.1.10. Application of Measurement Methodology . . . . . . . . 19
7. Delay Variation Metrics and Statistics . . . . . . . . . . . . 19 7. Delay Variation Metrics and Statistics . . . . . . . . . . . . 19
7.1. Name: Type-P-One-way-pdv-refmin-Poisson/Periodic-Stream . 19 7.1. Name: Type-P-One-way-pdv-refmin-Poisson/Periodic-Stream . 19
7.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 19 7.1.1. Metric Parameters: . . . . . . . . . . . . . . . . . . 19
7.1.2. Definition and Metric Units . . . . . . . . . . . . . 20 7.1.2. Definition and Metric Units . . . . . . . . . . . . . 20
7.1.3. Discussion and other details . . . . . . . . . . . . . 20 7.1.3. Discussion and other details . . . . . . . . . . . . . 20
7.1.4. Statistics: Mean, Variance, Skewness, Quanitle . . . . 20 7.1.4. Statistics: Mean, Variance, Skewness, Quanitle . . . . 20
7.1.5. Composition Functions: . . . . . . . . . . . . . . . . 21 7.1.5. Composition Functions: . . . . . . . . . . . . . . . . 21
7.1.6. Statement of Conjecture and Assumptions . . . . . . . 22 7.1.6. Statement of Conjecture and Assumptions . . . . . . . 22
7.1.7. Justification of the Composition Function . . . . . . 22 7.1.7. Justification of the Composition Function . . . . . . 22
skipping to change at page 4, line 43 skipping to change at page 4, line 43
8. Security Considerations . . . . . . . . . . . . . . . . . . . 23 8. Security Considerations . . . . . . . . . . . . . . . . . . . 23
8.1. Denial of Service Attacks . . . . . . . . . . . . . . . . 23 8.1. Denial of Service Attacks . . . . . . . . . . . . . . . . 23
8.2. User Data Confidentiality . . . . . . . . . . . . . . . . 23 8.2. User Data Confidentiality . . . . . . . . . . . . . . . . 23
8.3. Interference with the metrics . . . . . . . . . . . . . . 24 8.3. Interference with the metrics . . . . . . . . . . . . . . 24
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
10. Acknowlegements . . . . . . . . . . . . . . . . . . . . . . . 24 10. Acknowlegements . . . . . . . . . . . . . . . . . . . . . . . 24
11. Issues (Open and Closed) . . . . . . . . . . . . . . . . . . . 24 11. Issues (Open and Closed) . . . . . . . . . . . . . . . . . . . 24
12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26
13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 26
13.1. Normative References . . . . . . . . . . . . . . . . . . . 26 13.1. Normative References . . . . . . . . . . . . . . . . . . . 26
13.2. Informative References . . . . . . . . . . . . . . . . . . 26 13.2. Informative References . . . . . . . . . . . . . . . . . . 27
Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27 Index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27
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>
skipping to change at page 6, line 33 skipping to change at page 6, line 33
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 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 assignment. The solution then may be methods, and measurement time assignment. The solution then may be
the composition of several sub-path measurements. This 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 using its policy, using its own measurement tools and methods, and using its
own measurement timing. 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
skipping to change at page 7, line 19 skipping to change at page 7, line 19
function may utilize: 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 and passive o different measurement techniques like active [RFC2330], [RFC3432]
(recognizing that PSAMP WG will define capabilities to sample and passive [RFC5474].
packets to support measurement).
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.
3.2. Application 3.2. Application
The new composition framework [RFC5835] requires the specification of The new composition framework [RFC5835] requires the specification of
skipping to change at page 9, line 4 skipping to change at page 8, line 49
4.1.1. Metric Parameters 4.1.1. 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 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),
skipping to change at page 9, line 30 skipping to change at page 9, line 28
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
affect a packet's treatment as it traverses network
4.1.2. Definition and Metric Units 4.1.2. Definition and Metric Units
This section is unique for every metric. This section is unique for every metric.
4.1.3. Discussion and other details 4.1.3. Discussion and other details
This section is unique for every metric. This section is unique for every metric.
4.1.4. Statistic: 4.1.4. Statistic:
skipping to change at page 11, line 34 skipping to change at page 11, line 34
ground truth metric between a source and a destination, even when the ground truth metric between a source and a destination, even when the
route between them is undefined. route between them is undefined.
4.1.9. Specific cases where the conjecture might fail 4.1.9. 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 (due to bit to last bit. If the size of an IP packet changes on route (due
encapsulation for security reasons), this will influence delay to encapsulation), this can influence delay performance. However,
performance. the main error source may be the additional processing associated
with encapsulation and encryption/decryption if not experienced or
accounted for in sub-path measurements.
Fragmentation is a major issue for compostion 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
expected and compensated. For example, policy-based MPLS routing
could modify the class of service for the sub-paths and complete
path.
4.1.10. Application of Measurement Methodology 4.1.10. Application of Measurement Methodology
The methodology: The methodology:
SHOULD use similar packets sent and collected separately in each sub- SHOULD use similar packets sent and collected separately in each sub-
path. path, where "similar" in this case means that the Type-P contains as
many equal attributes as possible, while recognizing that there will
be differences. Note that Type-P includes stream characteristics
(e.g., Poisson, Periodic).
Allows a degree of flexibility regarding test stream generation Allows a degree of flexibility regarding test stream generation
(e.g., active or passive methods can produce an equivalent result, (e.g., active or passive methods can produce an equivalent result,
but the lack of control over the source, timing and correlation of but the lack of control over the source, timing and correlation of
passive measurements is much more challenging). passive measurements is much more challenging).
Poisson and/or Periodic streams are RECOMMENDED. Poisson and/or Periodic streams are RECOMMENDED.
Applies to both Inter-domain and Intra-domain composition. Applies to both Inter-domain and Intra-domain composition.
skipping to change at page 14, line 30 skipping to change at page 14, line 45
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 invloved in the complete path. where sub-paths s = 1 to S are involved in the complete path.
5.2.6. Statement of Conjecture and Assumptions 5.2.6. 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 bi-modal and the complete path are continuous. The mean of multi-modal
distributions have the unfortunate property that such a value may distributions have the unfortunate property that such a value may
never occur. never occur.
5.2.7. Justification of the Composition Function 5.2.7. Justification of the Composition Function
See the common section. See the common section.
5.2.8. Sources of Deviation from the Ground Truth 5.2.8. Sources of Deviation from the Ground Truth
See the common section. See the common section.
5.2.9. Specific cases where the conjecture might fail 5.2.9. Specific cases where the conjecture might fail
If any of the sub-path distributions are bimodal, then the measured If any of the sub-path distributions are multi-modal, then the
means may not be stable, and in this case the mean will not be a measured means may not be stable, and in this case the mean will not
particularly useful statistic when describing the delay distribution be a particularly useful statistic when describing the delay
of the complete path. distribution of the complete path.
The mean may not be sufficiently robust statistic to produce a The mean may not be 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.
5.2.10. Application of Measurement Methodology 5.2.10. Application of Measurement Methodology
The requirements of the common section apply here as well. The requirements of the common section apply here as well.
skipping to change at page 19, line 16 skipping to change at page 19, line 25
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-
born worm, loss due to queue overflow in one network may help another born worm, loss due to queue overflow in one network may help another
network to carry its traffic without loss. network to carry its traffic without loss.
others...
6.1.10. Application of Measurement Methodology 6.1.10. Application of Measurement Methodology
See the common section. See the common section.
7. Delay Variation Metrics and Statistics 7. Delay Variation Metrics and Statistics
7.1. Name: Type-P-One-way-pdv-refmin-Poisson/Periodic-Stream 7.1. Name: Type-P-One-way-pdv-refmin-Poisson/Periodic-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
skipping to change at page 19, line 44 skipping to change at page 19, line 51
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(first packet), the first packet of the pair, MUST this metric. F(current packet), the first packet of the pair,
have a valid Type-P-Finite-One-way-Delay less than Tmax (in other MUST have a valid Type-P-Finite-One-way-Delay less than Tmax (in
words, excluding packets which have undefined one-way delay) and other words, excluding packets which have undefined one-way delay)
MUST have been transmitted during the interval T, Tf. The second and MUST have been transmitted during the interval T, Tf. The
packet in the pair, F(second packet) MUST be the packet with the second packet in the pair, F(min_delay packet) MUST be the packet
minimum valid value of Type-P-Finite-One-way-Delay for the stream, with the minimum valid value of Type-P-Finite-One-way-Delay for
in addition to the criteria for F(first packet). If multiple the stream, in addition to the criteria for F(current packet). If
packets have equal minimum Type-P-Finite-One-way-Delay values, multiple packets have equal minimum Type-P-Finite-One-way-Delay
then the value for the earliest arriving packet SHOULD be used. values, then the value for the earliest arriving packet SHOULD be
used.
o MinDelay, the Type-P-Finite-One-way-Delay value for F(second 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 meeting the
F(first packet) criteria. F(current packet) criteria.
7.1.2. Definition and Metric Units 7.1.2. 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-Poisson/Periodic-Stream[n], the singleton Type-P-Finite-One-way-Delay-Poisson/Periodic-Stream[n], the singleton
for each packet[i] in the stream (a.k.a. FiniteDelay[i]). for 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-Poisson/Periodic-Stream[n] = above: Type-P-One-way-pdv-refmin-Poisson/Periodic-Stream[n] =
skipping to change at page 21, line 40 skipping to change at page 21, line 40
\ / \ \ / \
> | PDV[n]- MeanPDV | > | PDV[n]- MeanPDV |
/ \ / / \ /
--- ---
n = 1 n = 1
----------------------------------- -----------------------------------
/ \ / \
| ( 3/2 ) | | ( 3/2 ) |
\ (N - 1) * VarPDV / \ (N - 1) * VarPDV /
We define the Quantile of the IPDVRefMin sample as the value where We define the Quantile of the PDVRefMin sample as the value where the
the specified fraction of singletons is less than the given value. specified fraction of singletons is less than the given value.
7.1.5. Composition Functions: 7.1.5. 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.
7.1.5.1. Approximate Convolution 7.1.5.1. Approximate Convolution
skipping to change at page 24, line 36 skipping to change at page 24, line 36
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 METRICS REGISTRY as described in initial version of the registry
[RFC4148]. [RFC4148].
10. Acknowlegements 10. Acknowlegements
A long time ago, in a galaxy far, far away (Minneapolis), Will Leland A long time ago, in a galaxy far, far away (Minneapolis), Will Leland
suggested the simple and elegant Type-P-Finite-One-way-Delay concept. suggested the simple and elegant Type-P-Finite-One-way-Delay concept.
Thanks Will. Thanks Will.
Yaakov Stein and Donald McLachlan also provided useful comments along
the way.
11. Issues (Open and Closed) 11. Issues (Open and Closed)
This section to be removed at publication.
>>>>>>>>>>>>Issue: >>>>>>>>>>>>Issue:
Is Section 4.1.8.4 really describing a new error case, about Is Section 4.1.8.4 really describing a new error case, about
Alternate Routing? Or does Section 4.1.8.1 on sub-path differences Alternate Routing? Or does Section 4.1.8.1 on sub-path differences
cover it all? cover it all?
RESOLUTION: The section was re-worded in -10 version to make the RESOLUTION: The section was re-worded in -10 version to make the
topic, Absence of a real Route between the Src and Dst, more clear. topic, Absence of a real Route between the Src and Dst, more clear.
>>>>>>>>>>>> >>>>>>>>>>>>
>>>>>>>>>>>>Issue: >>>>>>>>>>>>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
engineers where and how to improve the performance between the source engineers where and how to improve the performance between the source
skipping to change at page 26, line 32 skipping to change at page 26, line 38
[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 [RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
Metric for IP Performance Metrics (IPPM)", RFC 3393, Metric for IP Performance Metrics (IPPM)", RFC 3393,
November 2002. November 2002.
[RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network
performance measurement with periodic streams", RFC 3432,
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.
[RFC5474] Duffield, N., Chiou, D., Claise, B., Greenberg, A.,
Grossglauser, M., and J. Rexford, "A Framework for Packet
Selection and Reporting", RFC 5474, March 2009.
[RFC5835] Morton, A. and S. Van den Berghe, "Framework for Metric [RFC5835] Morton, A. and S. Van den Berghe, "Framework for Metric
Composition", RFC 5835, April 2010. Composition", RFC 5835, April 2010.
13.2. Informative References 13.2. Informative References
[RFC5644] Stephan, E., Liang, L., and A. Morton, "IP Performance [RFC5644] Stephan, E., Liang, L., and A. Morton, "IP Performance
Metrics (IPPM): Spatial and Multicast", RFC 5644, Metrics (IPPM): Spatial and Multicast", RFC 5644,
October 2009. October 2009.
[Stats] McGraw-Hill NY NY, "Introduction to the Theory of [Stats] McGraw-Hill NY NY, "Introduction to the Theory of
 End of changes. 34 change blocks. 
53 lines changed or deleted 78 lines changed or added

This html diff was produced by rfcdiff 1.38. The latest version is available from http://tools.ietf.org/tools/rfcdiff/