draft-ietf-ippm-active-passive-03.txt   draft-ietf-ippm-active-passive-04.txt 
Network Working Group A. Morton Network Working Group A. Morton
Internet-Draft AT&T Labs Internet-Draft AT&T Labs
Intended status: Informational November 2, 2015 Intended status: Informational December 10, 2015
Expires: May 5, 2016 Expires: June 12, 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-03 draft-ietf-ippm-active-passive-04
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. This memo also describes multiple dimensions to help
evaluate new methods as they emerge.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
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 May 5, 2016. This Internet-Draft will expire on June 12, 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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packet stream and observations of the stream. packet stream and observations of the stream.
A Passive metric or method depends *solely* on observation of one A Passive metric or method depends *solely* on observation of one
or more existing packet streams. The streams only serve or more existing packet streams. The streams only serve
measurement when they are observed for that purpose, and are measurement when they are observed for that purpose, and are
present whether measurements take place or not. present whether measurements take place or not.
As new techniques for assessment emerge it is helpful to have clear As new techniques for assessment emerge it is helpful to have clear
definitions of these notions. This memo provides more detailed definitions of these notions. This memo provides more detailed
definitions, defines a new category for combinations of traditional definitions, defines a new category for combinations of traditional
active and passive techniques, and discusses means to evaluate new active and passive techniques, and discusses dimensions to evaluate
techniques as they emerge. new techniques as they emerge.
This memo provides definitions for Active and Passive Metrics and This memo provides definitions for Active and Passive Metrics and
Methods based on long usage in the Internet measurement community, Methods based on long usage in the Internet measurement community,
and especially the Internet Engineering Task Force. This memo also and especially the Internet Engineering Task Force. This memo also
describes the comnination of fundamental Active and Passive describes the combination of fundamental Active and Passive
categories, which are called Hybrid Methods and Metrics. categories, which are called Hybrid Methods and Metrics.
1.1. Requirements Language 1.1. 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].
2. Purpose and Scope 2. Purpose and Scope
The scope of this memo is to define and describe Active and Passive The scope of this memo is to define and describe Active and Passive
versions of metrics and methods which are consistent with the long- versions of metrics and methods which are consistent with the long-
time usage of these adjectives in the Internet measurement community time usage of these adjectives in the Internet measurement community
and especially the Internet Engineering Task Force. Since the and especially the Internet Engineering Task Force. Since the
science of measurement is expanding, we provide a category for science of measurement is expanding, we provide a category for
combinations of the traditional extremes, treating Active and Passive combinations of the traditional extremes, treating Active and Passive
as a continuum and designating combinations of their attributes as as a continuum and designating combinations of their attributes as
Hybrid methods. Hybrid methods.
Further, this memo's purpose includes describing multiple dimensions Further, this memo's purpose includes describing multiple dimensions
in which to evaluate methods as they emerge. to evaluate new methods as they emerge.
3. Terms and Definitions 3. Terms and Definitions
This section defines the key terms of the memo. Some definitions use This section defines the key terms of the memo. Some definitions use
the notion of "stream of interest" which is synonymous with the notion of "stream of interest" which is synonymous with
"population of interest" defined in clause 6.1.1 of ITU-T "population of interest" defined in clause 6.1.1 of ITU-T
Recommendation Y.1540 [Y.1540]. The definitions are consistent with Recommendation Y.1540 [Y.1540]. The definitions are consistent with
[I-D.zheng-ippm-framework-passive]. [I-D.zheng-ippm-framework-passive].
3.1. Performance Metric 3.1. Performance Metric
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3.2. Method of Measurement 3.2. Method of Measurement
The procedure or set of operations having the object of determining a The procedure or set of operations having the object of determining a
Measured Value or Measurement Result. Measured Value or Measurement Result.
3.3. Observation Point 3.3. Observation Point
See section 2 of [RFC7011] for this definition (a location in the See section 2 of [RFC7011] for this definition (a location in the
network where packets can be observed), and related definitions. The network where packets can be observed), and related definitions. The
comparable term defined in IETF literature on Active measurement is comparable term defined in IETF literature on Active measurement is
Measurement Point, see section 4.1 of [RFC5835]. Two terms have come Measurement Point, see section 4.1 of [RFC5835]. Both of these terms
into use describing similar actions at the identified point in the have come into use describing similar actions at the identified point
network path. in the network path.
3.4. Active Methods 3.4. Active Methods
Active measurement methods have the following attributes: Active measurement methods have the following attributes:
1. Commonly, the packet stream of interest is generated as the basis 1. Active methods generate packet streams. Commonly, the packet
of measurement. Sometimes, the adjective "synthetic" is used to stream of interest is generated as the basis of measurement.
categorize Active measurement streams [Y.1731]. Accompanying Sometimes, the adjective "synthetic" is used to categorize Active
packet stream(s) may be generated to increase overall traffic measurement streams [Y.1731]. Accompanying packet stream(s) may
load, though the loading stream(s) may not be measured. be generated to increase overall traffic 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, and 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 normally change during packet forwarding. Other changes along
path are possible, see [I-D.morton-ippm-2330-stdform-typep]. the path are possible, see [I-D.morton-ippm-2330-stdform-typep].
When adding traffic to the network for measurement, Active Methods When adding traffic to the network for measurement, Active Methods
influence the quantities measured to some degree, and those influence the quantities measured to some degree, and those
performing tests should take steps to quantify the effect(s) and/or performing tests should take steps to quantify the effect(s) and/or
minimize such effects. minimize such effects.
3.5. Active Metric 3.5. Active Metric
An Active Metric incorporates one or more of the aspects of Active An Active Metric incorporates one or more of the aspects of Active
Methods in the metric definition. Methods in the metric definition.
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packet characteristics (Type-P) and Source and Destination IP packet characteristics (Type-P) and Source and Destination IP
addresses (with their implications on both stream treatment and addresses (with their implications on both stream treatment and
interfaces associated with measurement points). interfaces associated with measurement points).
3.6. Passive Methods 3.6. Passive Methods
Passive measurement methods are Passive measurement methods are
o based solely on observations of undisturbed and unmodified packet o based solely on observations of undisturbed and unmodified packet
stream of interest (in other words, the method of measurement MUST stream of interest (in other words, the method of measurement MUST
NOT add, change, or remove fields, or change field values anywhere NOT add, change, or remove packets or fields, or change field
along the path). values anywhere along the path).
o dependent on the existence of one or more packet streams to supply o dependent on the existence of one or more packet streams to supply
the stream of interest the stream of interest.
o dependent on the presence of the packet stream of interest at one o dependent on the presence of the packet stream of interest at one
or more designated observation points. or more designated observation points.
Some passive methods simply observe and collect information on all Some passive methods simply observe and collect information on all
packets that pass Observation Point(s), while others filter the packets that pass Observation Point(s), while others filter the
packets as a first step and only collect information on packets that packets as a first step and only collect information on packets that
match the filter criteria, and thereby narrow the stream of interest. match the filter criteria, and thereby narrow the stream of interest.
It is common that passive methods are conducted at one or more It is common that passive methods are conducted at one or more
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| of Interest | Streams of Interest | of Interest | Streams of Interest
| | from Different Methods | | from Different Methods
==================================================================== ====================================================================
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] | | [RFC5644] |
There may be circumstances where results measured with Hybrid Methods There may be circumstances where results measured with Hybrid Methods
can be considered equivalent to Passive Methods. Referencing the can be considered equivalent to Passive Methods. Referencing the
notion of a "class C" where packets of different Type-P are treated 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 equally in Section 13 of [RFC2330]and the terminology for paths from
Section 5 of [RFC2330]: Section 5 of [RFC2330]:
Hybrid Methods of Measurement that augment or modify packets of a Hybrid Methods of Measurement that augment or modify packets of a
"class C" in a host should produce equivalent results to Passive "class C" in a host should produce equivalent results to Passive
Methods of Measurement, when hosts accessing and links transporting Methods of Measurement, when hosts accessing and links transporting
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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 known 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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1. effect on the performance of the stream of interest itself: for 1. effect on the performance of the stream of interest itself: for
example, choosing a packet marking or DSCP resulting in domain example, choosing a packet marking or DSCP resulting in domain
treatment as a real-time stream (as opposed to default/best- treatment as a real-time stream (as opposed to default/best-
effort marking. effort marking.
2. effect on unmeasured streams that share the path and/or 2. effect on unmeasured streams that share the path and/or
bottlenecks: for example, an extremely sparse measured stream of bottlenecks: for example, an extremely sparse measured stream of
minimal size packets typically has little effect on other flows minimal size packets typically has little effect on other flows
(and itself), while a stream designed to characterize path (and itself), while a stream designed to characterize path
capacity may effect all other flows passing through the capacity capacity may affect all other flows passing through the capacity
bottleneck (including itself). bottleneck (including itself).
3. effect on network conditions resulting in network adaptation: for 3. effect on network conditions resulting in network adaptation: for
example, a network monitoring load and congestion conditions example, a network monitoring load and congestion conditions
might change routing, placing some flows to alternate paths to might change routing, placing some flows to alternate paths to
mitigate the congestion. mitigate the congestion.
We have combined 1 and 2 on the Y-axis, as examination of examples We have combined 1 and 2 on the Y-axis, as examination of examples
indicates strong correlation of affects in this pair, and network indicates strong correlation of effects in this pair, and network
adaptation is not addressed. adaptation is not addressed.
It is apparent that different methods of IP network measurement can It is apparent that different methods of IP network measurement can
produce different results, even when measuring the same path at the produce different results, even when measuring the same path at the
same time. The two dimensions of the graph help to understand how same time. The two dimensions of the graph help to understand how
the results might change with the method chosen. For example, an the results might change with the method chosen. For example, an
Active Method to assess throughput adds some amount of traffic to the Active Method to assess throughput adds some amount of traffic to the
network which might result in lower throughput for all streams. network which might result in lower throughput for all streams.
However, a Passive Method to assess throughput can also err on the However, a Passive Method to assess throughput can also err on the
low side due to unknown limitations of the hosts providing traffic, low side due to unknown limitations of the hosts providing traffic,
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A. This method processes a user traffic stream, A. This method processes a user traffic stream,
B. and augments the stream of interest with frames having "fields B. and augments the stream of interest with frames having "fields
which are dedicated to measurement". which are dedicated to measurement".
o Synthetic Loss Measurement (SLM) and Delay Measurement (DM) o Synthetic Loss Measurement (SLM) and Delay Measurement (DM)
methods both inject dedicated measurement frames, so the "stream methods both inject dedicated measurement frames, so the "stream
of interest is generated as the basis of measurement". We of interest is generated as the basis of measurement". We
conclude that SLM and DM methods are Active Methods. conclude that SLM and DM methods are Active Methods.
We also recognize the existance of alternate terminology used in OAM We also recognize the existence of alternate terminology used in OAM
at layers other than IP. Readers are encouraged to consult [RFC6374] at layers other than IP. Readers are encouraged to consult [RFC6374]
for MPLS Loss and Delay measurement terminology, for example. for MPLS Loss and Delay measurement terminology, for example.
5. Security considerations 5. Security considerations
When considering privacy of those involved in measurement or those When considering privacy of those involved in measurement or those
whose traffic is measured, there is sensitive information whose traffic is measured, there is sensitive information
communicated and observed at observation and measurement points communicated and observed at observation and measurement points
described above. We refer the reader to the privacy considerations described above. We refer the reader to the privacy considerations
described in the Large Scale Measurement of Broadband Performance described in the Large Scale Measurement of Broadband Performance
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6. IANA Considerations 6. IANA Considerations
This memo makes no requests for IANA consideration. This memo makes no requests for IANA consideration.
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 scenarios 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, Stenio
several editorial improvements. Tal Mizrahi, Joachim Fabini, Greg Fernandes, and Spencer Dawkins suggested several editorial
Mirsky and Mike Ackermann raised many key considerations in their improvements. Tal Mizrahi, Joachim Fabini, Greg Mirsky and Mike
WGLC reviews, based on their broad measurement experience. Ackermann raised many key considerations in their 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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