draft-ietf-ippm-active-passive-02.txt   draft-ietf-ippm-active-passive-03.txt 
Network Working Group A. Morton Network Working Group A. Morton
Internet-Draft AT&T Labs Internet-Draft AT&T Labs
Intended status: Informational October 19, 2015 Intended status: Informational November 2, 2015
Expires: April 21, 2016 Expires: May 5, 2016
Active and Passive Metrics and Methods (and everything in-between, or Active and Passive Metrics and Methods (and everything in-between, or
Hybrid) Hybrid)
draft-ietf-ippm-active-passive-02 draft-ietf-ippm-active-passive-03
Abstract Abstract
This memo provides clear definitions for Active and Passive This memo provides clear definitions for Active and Passive
performance assessment. The construction of Metrics and Methods can performance assessment. The construction of Metrics and Methods can
be described as Active or Passive. Some methods may use a subset of be described as Active or Passive. Some methods may use a subset of
both active and passive attributes, and we refer to these as Hybrid both active and passive attributes, and we refer to these as Hybrid
Methods. Methods.
Status of This Memo Status of This Memo
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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-
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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 April 21, 2016. This Internet-Draft will expire on May 5, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 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
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2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 3 2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 3
3. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 3 3. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 3
3.1. Performance Metric . . . . . . . . . . . . . . . . . . . 3 3.1. Performance Metric . . . . . . . . . . . . . . . . . . . 3
3.2. Method of Measurement . . . . . . . . . . . . . . . . . . 4 3.2. Method of Measurement . . . . . . . . . . . . . . . . . . 4
3.3. Observation Point . . . . . . . . . . . . . . . . . . . . 4 3.3. Observation Point . . . . . . . . . . . . . . . . . . . . 4
3.4. Active Methods . . . . . . . . . . . . . . . . . . . . . 4 3.4. Active Methods . . . . . . . . . . . . . . . . . . . . . 4
3.5. Active Metric . . . . . . . . . . . . . . . . . . . . . . 5 3.5. Active Metric . . . . . . . . . . . . . . . . . . . . . . 5
3.6. Passive Methods . . . . . . . . . . . . . . . . . . . . . 5 3.6. Passive Methods . . . . . . . . . . . . . . . . . . . . . 5
3.7. Passive Metric . . . . . . . . . . . . . . . . . . . . . 6 3.7. Passive Metric . . . . . . . . . . . . . . . . . . . . . 6
3.8. Hybrid Methods and Metrics . . . . . . . . . . . . . . . 6 3.8. Hybrid Methods and Metrics . . . . . . . . . . . . . . . 6
4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 7 4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 8
4.1. Graphical Representation . . . . . . . . . . . . . . . . 7 4.1. Graphical Representation . . . . . . . . . . . . . . . . 8
4.2. Discussion of PDM . . . . . . . . . . . . . . . . . . . . 10 4.2. Discussion of PDM . . . . . . . . . . . . . . . . . . . . 10
4.3. Discussion of "Coloring" Method . . . . . . . . . . . . . 11 4.3. Discussion of "Coloring" Method . . . . . . . . . . . . . 11
4.4. Brief Discussion of OAM Methods . . . . . . . . . . . . . 11 4.4. Brief Discussion of OAM Methods . . . . . . . . . . . . . 11
5. Security considerations . . . . . . . . . . . . . . . . . . . 12 5. Security considerations . . . . . . . . . . . . . . . . . . . 12
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1. Normative References . . . . . . . . . . . . . . . . . . 12 8.1. Normative References . . . . . . . . . . . . . . . . . . 12
8.2. Informative References . . . . . . . . . . . . . . . . . 13 8.2. Informative References . . . . . . . . . . . . . . . . . 13
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 14
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of measurement. Sometimes, the adjective "synthetic" is used to of measurement. Sometimes, the adjective "synthetic" is used to
categorize Active measurement streams [Y.1731]. Accompanying categorize Active measurement streams [Y.1731]. Accompanying
packet stream(s) may be generated to increase overall traffic packet stream(s) may be generated to increase overall traffic
load, though the loading stream(s) may not be measured. load, though the loading stream(s) may not be measured.
2. The packets in the stream of interest have fields or field values 2. The packets in the stream of interest have fields or field values
(or are augmented or modified to include fields or field values) (or are augmented or modified to include fields or field values)
which are dedicated to measurement. Since measurement usually which are dedicated to measurement. Since measurement usually
requires determining the corresponding packets at multiple requires determining the corresponding packets at multiple
measurement points, a sequence number is the most common measurement points, a sequence number is the most common
information dedicated to measurement, often combined with a information dedicated to measurement, and often combined with a
timestamp. timestamp.
3. The Source and Destination of the packet stream of interest are 3. The Source and Destination of the packet stream of interest are
usually known a priori. usually known a priori.
4. The characteristics of the packet stream of interest are known at 4. The characteristics of the packet stream of interest are known at
the Source at least, and may be communicated to Destination as the Source at least, and may be communicated to Destination as
part of the method. Note that some packet characteristics will part of the method. Note that some packet characteristics will
normaly change during packet forwarding. Other changes along the normaly change during packet forwarding. Other changes along the
path are possible, see [I-D.morton-ippm-2330-stdform-typep]. path are possible, see [I-D.morton-ippm-2330-stdform-typep].
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be found in ITU-T Recommendation Y.1540 [Y.1540], where the metrics be found in ITU-T Recommendation Y.1540 [Y.1540], where the metrics
are defined on the basis of reference events generated as packet pass are defined on the basis of reference events generated as packet pass
reference points. The metrics are agnostic to the distinction reference points. The metrics are agnostic to the distinction
between active and passive when the necessary packet correspondence between active and passive when the necessary packet correspondence
can be derived from the observed stream of interest as required. can be derived from the observed stream of interest as required.
3.8. Hybrid Methods and Metrics 3.8. Hybrid Methods and Metrics
Hybrid Methods are Methods of Measurement which use a combination of Hybrid Methods are Methods of Measurement which use a combination of
Active Methods and Passive Methods, to assess Active Metrics, Passive Active Methods and Passive Methods, to assess Active Metrics, Passive
Metrics, or new metrics derived from the a' priori knowledge and Metrics, or new metrics derived from the a priori knowledge and
observations of the stream of interest. ITU-T Recommendation Y.1540 observations of the stream of interest. ITU-T Recommendation Y.1540
[Y.1540] defines metrics that are also applicable to the hybrid [Y.1540] defines metrics that are also applicable to the hybrid
categories, since packet correspondence at different observation/ categories, since packet correspondence at different observation/
reference points could be derived from "fields or field values which reference points could be derived from "fields or field values which
are dedicated to measurement", but otherwise the methods are passive. are dedicated to measurement", but otherwise the methods are passive.
There are several types of Hybrid methods, as categorized below. There are several types of Hybrid methods, as categorized below.
With respect to a *single* stream of interest, Hybrid Type I methods With respect to a *single* stream of interest, Hybrid Type I methods
fit in the continuum as follows, in terms of what happens at the fit in the continuum as follows, in terms of what happens at the
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==================================================================== ====================================================================
Single Fundamental | Active or Passive | Single Fundamental | Active or Passive |
Method | | Method | |
Synthesis of | Hybrid Type I | Synthesis of | Hybrid Type I |
Fundamental Methods | | Fundamental Methods | |
Multiple Methods | Spatial Metrics | Hybrid Type II Multiple Methods | Spatial Metrics | Hybrid Type II
| [RFC 5644] | | [RFC 5644] |
There may be circumstances where results measured with Hybrid Methods
can be considered equivalent to Passive Methods. Referencing the
notion of a "class C" where packets of different Type-P are treated
equally in Section 13 of [RFC2330]and the terminology for paths from
Section 5 of [RFC2330]:
Hybrid Methods of Measurement that augment or modify packets of a
"class C" in a host should produce equivalent results to Passive
Methods of Measurement, when hosts accessing and links transporting
these packets along the path (other than those performing
augmentation/modification) treat packets from both categories of
methods (with and without the augmentation/modification) as the same
"class C". The Passive Methods of Measurement represent the Ground
Truth for comparisons of results between Passive and Hybrid methods,
and this comparison should be conducted to confirm the class C
treatment.
4. Discussion 4. Discussion
This section illustrates the definitions and presents some examples. This section illustrates the definitions and presents some examples.
4.1. Graphical Representation 4.1. Graphical Representation
If we compare the Active and Passive Methods, there are at least two If we compare the Active and Passive Methods, there are at least two
dimensions on which methods can be evaluated. This evaluation space dimensions on which methods can be evaluated. This evaluation space
may be useful when a method is a combination of the two alternative may be useful when a method is a combination of the two alternative
methods. methods.
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a key dimension for Active measurement error analysis. (Comment: a key dimension for Active measurement error analysis. (Comment:
There is also the notion of time averages - a measurement stream There is also the notion of time averages - a measurement stream
may have significant effect while it is present, but the stream is may have significant effect while it is present, but the stream is
only generated 0.1% of the time. On the other hand, observations only generated 0.1% of the time. On the other hand, observations
alone have no effect on network performance. To keep these alone have no effect on network performance. To keep these
dimensions simple, we consider the stream effect only when it is dimensions simple, we consider the stream effect only when it is
present, but note that reactive networks defined in [RFC7312] may present, but note that reactive networks defined in [RFC7312] may
exhibit bias for some time beyond the life of a stream.) exhibit bias for some time beyond the life of a stream.)
X-Axis: "a priori Stream Knowledge." The degree to which stream X-Axis: "a priori Stream Knowledge." The degree to which stream
characteristics are know a' priori. There are methodological characteristics are know a priori. There are methodological
advantages of knowing the source stream characteristics, and advantages of knowing the source stream characteristics, and
having complete control of the stream characteristics. For having complete control of the stream characteristics. For
example, knowing the number of packets in a stream allows more example, knowing the number of packets in a stream allows more
efficient operation of the measurement receiver, and so is an efficient operation of the measurement receiver, and so is an
asset for active measurement methods. Passive methods (with no asset for active measurement methods. Passive methods (with no
sample filter) have few clues available to anticipate what the sample filter) have few clues available to anticipate what the
protocol first packet observed will use or how many packets will protocol first packet observed will use or how many packets will
comprise the flow, but once the standard protocol of a flow is comprise the flow, but once the standard protocol of a flow is
known the possibilities narrow (for some compliant flows). known the possibilities narrow (for some compliant flows).
Therefore this is a key dimension for Passive measurement error Therefore this is a key dimension for Passive measurement error
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solutions are to model the application streams more exactly with an solutions are to model the application streams more exactly with an
Active Method, or accept the risks and potential errors with the Active Method, or accept the risks and potential errors with the
Passive Method discussed above. Passive Method discussed above.
4.2. Discussion of PDM 4.2. Discussion of PDM
In [I-D.ietf-ippm-6man-pdm-option], an IPv6 Option Header for In [I-D.ietf-ippm-6man-pdm-option], an IPv6 Option Header for
Performance and Diagnostic Measurements (PDM) is described which Performance and Diagnostic Measurements (PDM) is described which
(when added to the stream of interest at strategic interfaces) (when added to the stream of interest at strategic interfaces)
supports performance measurements. This method processes a user supports performance measurements. This method processes a user
traffic stream and adds "fields which are dedicated to measurement". traffic stream and adds "fields which are dedicated to measurement"
(the measurement intent is made clear in the title of this option).
Thus: Thus:
o The method intends to have a small effect on the measured stream o The method intends to have a small effect on the measured stream
and other streams in the network. There are conditions where this and other streams in the network. There are conditions where this
intent may not be realized. intent may not be realized.
o The measured stream has unknown characteristics until it is o The measured stream has unknown characteristics until it is
processed to add the PDM Option header. processed to add the PDM Option header. Note that if the packet
MTU is exceeded after adding the header, the intent to have small
effect will not be realized.
We conclude that this is a Hybrid Type I method, having at least one We conclude that this is a Hybrid Type I method, having at least one
characteristic of both active and passive methods for a single stream characteristic of both active and passive methods for a single stream
of interest. of interest.
4.3. Discussion of "Coloring" Method 4.3. Discussion of "Coloring" Method
Draft [I-D.tempia-opsawg-p3m], proposed to color packets by re- Draft [I-D.tempia-opsawg-p3m], proposed to color packets by re-
writing a field of the stream at strategic interfaces to support writing a field of the stream at strategic interfaces to support
performance measurements. This method processes a user traffic performance measurements. This method processes a user traffic
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7. Acknowledgements 7. Acknowledgements
Thanks to Mike Ackermann for asking the right question, and for Thanks to Mike Ackermann for asking the right question, and for
several suggestions on terminology. Brian Trammell provided key several suggestions on terminology. Brian Trammell provided key
terms and references for the passive category, and suggested ways to terms and references for the passive category, and suggested ways to
expand the Hybrid description and types. Phil Eardley suggested some expand the Hybrid description and types. Phil Eardley suggested some
hybrid scenaios for categorization as part of his review. Tiziano hybrid scenaios for categorization as part of his review. Tiziano
Ionta reviewed the draft and suggested the classification for the Ionta reviewed the draft and suggested the classification for the
"coloring" method of measurement. Nalini Elkins identified several "coloring" method of measurement. Nalini Elkins identified several
areas for clarification following her review. Bill Jouris suggested areas for clarification following her review. Bill Jouris suggested
several editorial improvements. Tal Mizrahi and Joachim Fabini several editorial improvements. Tal Mizrahi, Joachim Fabini, Greg
raised many key considerations in their reviews, based on their broad Mirsky and Mike Ackermann raised many key considerations in their
measurement experience. WGLC reviews, based on their broad measurement experience.
8. References 8. References
8.1. Normative References 8.1. Normative References
[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,
DOI 10.17487/RFC2330, May 1998, DOI 10.17487/RFC2330, May 1998,
<http://www.rfc-editor.org/info/rfc2330>. <http://www.rfc-editor.org/info/rfc2330>.
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