draft-ietf-ippm-active-passive-06.txt   rfc7799.txt 
Network Working Group A. Morton Internet Engineering Task Force (IETF) A. Morton
Internet-Draft AT&T Labs Request for Comments: 7799 AT&T Labs
Intended status: Informational January 21, 2016 Category: Informational May 2016
Expires: July 24, 2016 ISSN: 2070-1721
Active and Passive Metrics and Methods (and everything in-between, or Active and Passive Metrics and Methods
Hybrid) (with Hybrid Types In-Between)
draft-ietf-ippm-active-passive-06
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 either "Active" or "Passive". Some methods may use a
both active and passive attributes, and we refer to these as Hybrid subset of both Active and Passive attributes, and we refer to these
Methods. This memo also describes multiple dimensions to help as "Hybrid Methods". This memo also describes multiple dimensions to
evaluate new methods as they emerge. help evaluate new methods as they emerge.
Status of This Memo Status of This Memo
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction ....................................................2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language ......................................3
2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 3 2. Purpose and Scope ...............................................3
3. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 3 3. Terms and Definitions ...........................................3
3.1. Performance Metric . . . . . . . . . . . . . . . . . . . 4 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 . . . . . . . . . . . . . . . . . . . . . . . . . 8 4. Discussion ......................................................8
4.1. Graphical Representation . . . . . . . . . . . . . . . . 8 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. References .....................................................12
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 12 6.1. Normative References ......................................12
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 13 6.2. Informative References ....................................13
8.1. Normative References . . . . . . . . . . . . . . . . . . 13 Acknowledgements ..................................................14
8.2. Informative References . . . . . . . . . . . . . . . . . 14 Author's Address ..................................................14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 15
1. Introduction 1. Introduction
The adjectives "active" and "passive" have been used for many years The adjectives "Active" and "Passive" have been used for many years
to distinguish two different classes of Internet performance to distinguish between two different classes of Internet performance
assessment. The first Passive and Active Measurement (PAM) assessment. The first Passive and Active Measurement (PAM)
Conference was held in 2000, but the earliest proceedings available Conference was held in 2000, but the earliest proceedings available
on-line are from the second PAM conference in 2001 online are from the second PAM conference in 2001
[https://www.ripe.net/ripe/meetings/pam-2001]. <https://www.ripe.net/ripe/meetings/pam-2001>.
The notions of "active" and "passive" are well-established. In The notions of "Active" and "Passive" are well-established. In
general: general:
An Active metric or method depends on a dedicated measurement o An Active Metric or Method depends on a dedicated measurement
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 o 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 or not measurements take place.
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 dimensions to evaluate Active and Passive techniques, and discusses dimensions to evaluate
new 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 (IETF). This memo
describes the combination of fundamental Active and Passive also describes the combination of fundamental Active and Passive
categories, which are called Hybrid Methods and Metrics. categories that 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 [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 that 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 IETF. Since the science of measurement is
science of measurement is expanding, we provide a category for expanding, we provide a category for combinations of the traditional
combinations of the traditional extremes, treating Active and Passive extremes, treating Active and Passive as a continuum and designating
as a continuum and designating combinations of their attributes as 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
to evaluate new 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]. These definitions will be useful for Recommendation Y.1540 [Y.1540]. These definitions will be useful for
work-in-progress, such as [I-D.zheng-ippm-framework-passive] (with any work in progress, such as [PASSIVE] (with which there is already
which there is already good consistency). good consistency).
3.1. Performance Metric 3.1. Performance Metric
The standard definition of a quantity, produced in an assessment of The standard definition of a quantity, produced in an assessment of
performance and/or reliability of the network, which has an intended performance and/or reliability of the network, which has an intended
utility and is carefully specified to convey the exact meaning of a utility and is carefully specified to convey the exact meaning of a
measured value. (This definition is consistent with that of measured value. (This definition is consistent with that of
Performance Metric in [RFC2330] and [RFC6390]). Performance Metric in [RFC2330] and [RFC6390]).
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 the definition of Observation Point (a
network where packets can be observed), and related definitions. The location in the network where packets can be observed), and related
comparable term defined in IETF literature on Active measurement is definitions. The comparable term defined in IETF literature on
Measurement Point, see section 4.1 of [RFC5835]. Both of these terms Active measurement is "Measurement Point" (see Section 4.1 of
have come into use describing similar actions at the identified point [RFC5835]). Both of these terms have come into use describing
in the network path. similar actions at the identified point in the network path.
3.4. Active Methods 3.4. Active Methods
Active measurement methods have the following attributes: Active Methods of Measurement have the following attributes:
1. Active methods generate packet streams. Commonly, the packet o Active Methods generate packet streams. Commonly, the packet
stream of interest is generated as the basis of measurement. stream of interest is generated as the basis of measurement.
Sometimes, the adjective "synthetic" is used to categorize Active Sometimes, the adjective "synthetic" is used to categorize Active
measurement streams [Y.1731]. Accompanying packet stream(s) may measurement streams [Y.1731]. An accompanying packet stream or
be generated to increase overall traffic load, though the loading streams may be generated to increase overall traffic load, though
stream(s) may not be measured. the loading stream(s) may not be measured.
2. The packets in the stream of interest have fields or field values o 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 that 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 it is often combined
timestamp. with a timestamp.
3. The Source and Destination of the packet stream of interest are o 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 o 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 the Destination
part of the method. Note that some packet characteristics will as part of the method. Note that some packet characteristics will
normally change during packet forwarding. Other changes along normally change during packet forwarding. Other changes along the
the path are possible, see [I-D.morton-ippm-2330-stdform-typep]. path are possible, see [STDFORM].
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.
For example, IETF metrics for IP performance (developed according to For example, IETF metrics for IP performance (developed according to
the [RFC2330] framework) include the Source packet stream the framework described in [RFC2330]) include the Source-packet
characteristics as metric input parameters, and also specify the stream characteristics as metric-input parameters, and also specify
packet characteristics (Type-P) and Source and Destination IP the 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 Methods of Measurement are:
o based solely on observations of undisturbed and unmodified packet o based solely on observations of an undisturbed and unmodified
stream of interest (in other words, the method of measurement MUST packet stream of interest (in other words, the method of
NOT add, change, or remove packets or fields, or change field measurement MUST NOT add, change, or remove packets or fields or
values anywhere along the path). change field 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
Observation Points. Passive methods to assess Performance Metrics Observation Points. Passive Methods to assess Performance Metrics
often require multiple observation points, e.g., to assess latency of often require multiple Observation Points, e.g., to assess the
packet transfer across a network path between two Observation Points. latency of packet transfer across a network path between two
In this case, the observed packets must include enough information to Observation Points. In this case, the observed packets must include
determine the corresponding packets at different Observation Points. enough information to determine the corresponding packets at
different Observation Points.
Communication of the observations (in some form) to a collector is an Communication of the observations (in some form) to a collector is an
essential aspect of Passive Methods. In some configurations, the essential aspect of Passive Methods. In some configurations, the
traffic load associated with results export to a collector may traffic load generated when communicating (or exporting) the Passive
influence the network performance. However, the collection of Method results to a collector may itself influence the measured
results is not unique to Passive Methods, and the load from network's performance. However, the collection of results is not
management and operations of measurement systems must always be unique to Passive Methods, and the load from management and
considered for potential effects on the measured values. operations of measurement systems must always be considered for
potential effects on the measured values.
3.7. Passive Metric 3.7. Passive Metric
Passive Metrics apply to observations of packet traffic (traffic Passive Metrics apply to observations of packet traffic (traffic
flows in [RFC7011]). flows in [RFC7011]).
Passive performance metrics are assessed independent of the packets Passive performance metrics are assessed independently of the packets
or traffic flows, and solely through observation. Some refer to such or traffic flows, and solely through observation. Some refer to such
assessments as "out-of-band". assessments as "out of band".
One example of passive performance metrics for IP packet transfer can One example of Passive Performance Metrics for IP packet transfer can
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 packets
reference points. The metrics are agnostic to the distinction pass 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 that 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
Source (or Observation Point nearby): Source (or Observation Point nearby):
o If you generate the stream of interest => Active o Generation of the stream of interest => Active
o If you augment or modify the stream of interest, or employ methods o Augmentation or modification of the stream of interest, or
that modify the treatment of the stream => Hybrid Type I employment of methods that modify the treatment of the stream =>
Hybrid Type I
o Observation of a stream of interest => Passive
o If you solely observe a stream of interest => Passive
As an example, consider the case where the method generates traffic As an example, consider the case where the method generates traffic
load stream(s), and observes an existing stream of interest according load stream(s), and observes an existing stream of interest according
to the criteria for Passive Methods. Since loading streams are an to the criteria for Passive Methods. Since loading streams are an
aspect of Active Methods, the stream of interest is not "solely aspect of Active Methods, the stream of interest is not "solely
observed", and the measurements involve a single stream of interest observed", and the measurements involve a single stream of interest
whose treatment has been modified both the presence of the load. whose treatment has been modified by the presence of the load.
Therefore, this is a Hybrid Type I method. Therefore, this is a Hybrid Type I method.
We define Hybrid Type II as follows: Methods that employ two or more We define Hybrid Type II as follows: Methods that employ two or more
different streams of interest with some degree of mutual coordination different streams of interest with some degree of mutual coordination
(e.g., one or more Active streams and one or more undisturbed and (e.g., one or more Active streams and one or more undisturbed and
unmodified packet streams) to collect both Active and Passive Metrics unmodified packet streams) to collect both Active and Passive Metrics
and enable enhanced characterization from additional joint analysis. and enable enhanced characterization from additional joint analysis.
[I-D.trammell-ippm-hybrid-ps] presents a problem statement for Hybrid [HYBRID] presents a problem statement for Hybrid Type II Methods and
Type II methods and metrics. Note that one or more Hybrid Type I Metrics. Note that one or more Hybrid Type I streams could be
streams could be substituted for the Active streams or undisturbed substituted for the Active streams or undisturbed streams in the
streams in the mutually coordinated set. It is the Type II Methods mutually coordinated set. It is the Type II Methods where unique
where unique Hybrid Metrics are anticipated to emerge. Hybrid Metrics are anticipated to emerge.
Methods based on a combination of a single (generated) Active stream Methods based on a combination of a single (generated) Active stream
and Passive observations applied to the stream of interest at and Passive observations applied to the stream of interest at
intermediate observation points are also a type of Hybrid Methods. intermediate Observation Points are also Hybrid Methods. However,
However, [RFC5644] already defines these as Spatial Metrics and [RFC5644] already defines these as Spatial Metrics and Methods. It
Methods. It is possible to replace the Active stream of [RFC5644] is possible to replace the Active stream of [RFC5644] with a Hybrid
with a Hybrid Type I stream and measure Spatial Metrics (but this was Type I stream and measure Spatial Metrics (but this was unanticipated
un-anticipated when [RFC5644] was developed). when [RFC5644] was developed).
The Table below illustrates the categorization of methods (where The table below illustrates the categorization of methods (where
"Synthesis" refers to a combination of Active and Passive Method "Synthesis" refers to a combination of Active and Passive Method
attributes). attributes).
| Single Stream | Multiple Simultaneous | Single Stream | Multiple Simultaneous
| 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
| [RFC5644] | | [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 those measured with Passive Methods.
notion of a "class C" where packets of different Type-P are treated This notion references the possibility of a "class C" where packets
equally in Section 13 of [RFC2330]and the terminology for paths from of different Type-P are treated equally in network implementation, as
Section 5 of [RFC2330]: described in Section 13 of [RFC2330] and using the terminology for
paths from 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 results equivalent to Passive
Methods of Measurement, when hosts accessing and links transporting Methods of Measurement when hosts accessing and links transporting
these packets along the path (other than those performing these packets along the path (other than those performing
augmentation/modification) treat packets from both categories of augmentation/modification) treat packets from both categories of
methods (with and without the augmentation/modification) as the same methods (with and without the augmentation/modification) as the
"class C". The Passive Methods of Measurement represent the Ground same "class C". The Passive Methods of Measurement represent the
Truth for comparisons of results between Passive and Hybrid methods, Ground Truth when comparing results between Passive and Hybrid
and this comparison should be conducted to confirm the class C Methods, and this comparison should be conducted to confirm the
treatment. "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.
The two dimensions (initially chosen) are: The two dimensions (initially chosen) are:
Y-Axis: "Effect of the measured stream on network conditions." The Y-Axis: "Effect of the measured stream on network conditions". The
degree to which the stream of interest biases overall network degree to which the stream of interest biases overall network
conditions experienced by that stream and other streams. This is conditions experienced by that stream and other streams. This is
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 known 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 Methods of Measurement. Passive Methods (with no
sample filter) have few clues available to anticipate what the sample filter) have few clues available to anticipate what
protocol first packet observed will use or how many packets will protocol the first packet observed will use or how many packets
comprise the flow, but once the standard protocol of a flow is will comprise the flow; 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
analysis. analysis.
There are a few examples we can plot on a two-dimensional space. We There are a few examples we can plot on a two-dimensional space. We
can anchor the dimensions with reference point descriptions. can anchor the dimensions with reference point descriptions.
Y-Axis:Effect of the measured stream on network conditions Y-Axis:Effect of the measured stream on network conditions
^ Max ^ Max
|* Active using max capacity stream |* Active using max capacity stream
| |
| |
skipping to change at page 9, line 30 skipping to change at page 9, line 23
| |
| |
| |
|* Active using extremely sparse, randomized stream |* Active using extremely sparse, randomized stream
| * PDM Passive | * PDM Passive
| Min * | Min *
+----------------------------------------------------------------| +----------------------------------------------------------------|
| | | |
Stream X-Axis: a priori Stream Knowledge No Stream Stream X-Axis: a priori Stream Knowledge No Stream
Characteristics Characteristics Characteristics Characteristics
completely Known Completely Known
known Known
(In the graph above, "PDM" refers to [I-D.ietf-ippm-6man-pdm-option], (In the graph above, "PDM" refers to [PDMOPTION], an IPv6 Option
an IPv6 Option Header for Performance and Diagnostic Measurements, Header for Performance and Diagnostic Measurements, described in
descrived in section 4.2.) Section 4.2.)
We recognize that method categorization could be based on additional We recognize that method categorization could be based on additional
dimensions, but this would require a different graphical approach. dimensions, but this would require a different graphical approach.
For example, "effect of stream of interest on network conditions" For example, "effect of stream of interest on network conditions"
could easily be further qualified into: could easily be further qualified into:
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 Differentiated Services example, choosing a packet marking or Differentiated Services
Code Point (DSCP) resulting in domain treatment as a real-time Code Point (DSCP) resulting in domain treatment as a real-time
skipping to change at page 10, line 14 skipping to change at page 9, line 50
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 affect 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 on 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 effects in this pair, and network indicates strong correlation of the 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 us 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,
competition for host resources, limitations of the network interface, competition for host resources, limitations of the network interface,
or private sub-networks that are not an intentional part of the path, or private sub-networks that are not an intentional part of the path,
etc. And Hybrid Methods could easily suffer from both forms of etc. Hybrid Methods could easily suffer from both forms of error.
error. Another example of potential errors stems from the pitfalls Another example of potential errors stems from the pitfalls of using
of using an Active stream with known bias, such as a periodic stream an Active stream with known a bias, such as a periodic stream defined
defined in [RFC3432]. The strength of modelling periodic streams in [RFC3432]. The strength of modeling periodic streams (like Voice
(like VoIP) is a potential weakness when extending the measured over IP (VoIP)) is a potential weakness when extending the measured
results to other application whose streams are non-periodic. The results to other application whose streams are non-periodic. The
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 to 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 [PDMOPTION], an IPv6 Option Header for Performance and Diagnostic
Performance and Diagnostic Measurements (PDM) is described which Measurements (PDM) is described which, when added to the stream of
(when added to the stream of interest at strategic interfaces) interest at strategic interfaces, supports performance measurements.
supports performance measurements. This method processes a user This method processes a user traffic stream and adds "fields which
traffic stream and adds "fields which are dedicated to measurement" are dedicated to measurement" (the measurement intent is made clear
(the measurement intent is made clear in the title of this option). 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 minor 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. Note that if the packet processed to add the PDM Option header. Note that if the packet
MTU is exceeded after adding the header, the intent to have small MTU is exceeded after adding the header, the intent to have a
effect will not be realized. minor 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- [OPSAWG], proposed to color packets by re-writing a field of the
writing a field of the stream at strategic interfaces to support stream at strategic interfaces to support performance measurements
performance measurements (noting that this is a difficult operation (noting that this is a difficult operation at an intermediate point
at an intermediate point on an encrypted Virtual Private Network). on an encrypted Virtual Private Network). This method processes a
This method processes a user traffic stream and inserts "fields or user traffic stream and inserts "fields or values which are dedicated
values which are dedicated to measurement". Thus: to measurement". Thus:
o The method intends to have a small effect on the measured stream o The method intends to have a minor effect on the measured stream
and other streams in the network (smaller than PDM above). There and other streams in the network (less than PDM above). There are
are conditions where this intent may not be realized. conditions where this 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 coloring in the header, and the stream could processed to add the coloring in the header, and the stream could
be measured and time-stamped during that process. be measured and time-stamped during that process.
We note that [I-D.chen-ippm-coloring-based-ipfpm-framework] proposes We note that [COLORING] proposes a method similar to [OPSAWG], as
a method similar to [I-D.tempia-opsawg-p3m], as ippm-list discussion discussion on the IPPM mailing list revealed.
revealed.
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.
4.4. Brief Discussion of OAM Methods 4.4. Brief Discussion of OAM Methods
Many Operations, Administration, and Management (OAM) methods exist Many Operations, Administration, and Management (OAM) methods exist
beyond the IP-layer. For example, [Y.1731] defines several different beyond the IP layer. For example, [Y.1731] defines several different
measurement methods which we would classify as follows: measurement methods that we would classify as follows:
o Loss Measurement (LM) occasionally injects frames with a count of o Loss Measurement (LM) occasionally injects frames with a count of
previous frames since the last LM message. We conclude LM is previous frames since the last LM message. We conclude LM is
Hybrid Type I because Hybrid Type I, because this method processes a user traffic stream
A. This method processes a user traffic stream, and augments the stream of interest with frames having "fields
which are dedicated to measurement".
B. and augments the stream of interest with frames having "fields
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 existence 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 security and privacy of those involved in When considering the security and privacy of those involved in
measurement or those whose traffic is measured, there is sensitive measurement or those whose traffic is measured, there is sensitive
information communicated and observed at observation and measurement information communicated and observed at observation and measurement
points described above, and protocol issues to consider. We refer points described above, and protocol issues to consider. We refer
the reader to the security and privacy considerations described in the reader to the security and privacy considerations described in
the Large Scale Measurement of Broadband Performance (LMAP) Framework the Large-Scale Measurement of Broadband Performance (LMAP) Framework
[RFC7594], which covers active and passive measurement techniques and [RFC7594], which covers Active and Passive measurement techniques and
supporting material on measurement context. supporting material on measurement context.
6. IANA Considerations 6. References
This memo makes no requests for IANA consideration.
7. Acknowledgements
Thanks to Mike Ackermann for asking the right question, and for
several suggestions on terminology. Brian Trammell provided key
terms and references for the passive category, and suggested ways to
expand the Hybrid description and types. Phil Eardley suggested some
hybrid scenarios for categorization as part of his review. Tiziano
Ionta reviewed the draft and suggested the classification for the
"coloring" method of measurement. Nalini Elkins identified several
areas for clarification following her review. Bill Jouris, Stenio
Fernandes, and Spencer Dawkins suggested several editorial
improvements. Tal Mizrahi, Joachim Fabini, Greg Mirsky and Mike
Ackermann raised many key considerations in their WGLC reviews, based
on their broad measurement experience.
8. References 6.1. Normative References
8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[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>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
[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,
DOI 10.17487/RFC3432, November 2002, DOI 10.17487/RFC3432, November 2002,
<http://www.rfc-editor.org/info/rfc3432>. <http://www.rfc-editor.org/info/rfc3432>.
[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,
DOI 10.17487/RFC5644, October 2009, DOI 10.17487/RFC5644, October 2009,
<http://www.rfc-editor.org/info/rfc5644>. <http://www.rfc-editor.org/info/rfc5644>.
skipping to change at page 14, line 11 skipping to change at page 13, line 22
Framework for IP Performance Metrics (IPPM)", RFC 7312, Framework for IP Performance Metrics (IPPM)", RFC 7312,
DOI 10.17487/RFC7312, August 2014, DOI 10.17487/RFC7312, August 2014,
<http://www.rfc-editor.org/info/rfc7312>. <http://www.rfc-editor.org/info/rfc7312>.
[RFC7594] Eardley, P., Morton, A., Bagnulo, M., Burbridge, T., [RFC7594] Eardley, P., Morton, A., Bagnulo, M., Burbridge, T.,
Aitken, P., and A. Akhter, "A Framework for Large-Scale Aitken, P., and A. Akhter, "A Framework for Large-Scale
Measurement of Broadband Performance (LMAP)", RFC 7594, Measurement of Broadband Performance (LMAP)", RFC 7594,
DOI 10.17487/RFC7594, September 2015, DOI 10.17487/RFC7594, September 2015,
<http://www.rfc-editor.org/info/rfc7594>. <http://www.rfc-editor.org/info/rfc7594>.
8.2. Informative References 6.2. Informative References
[RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay [COLORING]
Measurement for MPLS Networks", RFC 6374, Chen, M., Ed., Zheng, L., Ed., Mirsky, G., Ed., Fioccola,
DOI 10.17487/RFC6374, September 2011, G., Ed., and T. Mizrahi, Ed., "IP Flow Performance
<http://www.rfc-editor.org/info/rfc6374>. Measurement Framework", Work in Progress, draft-chen-ippm-
coloring-based-ipfpm-framework-06, March 2016.
[I-D.morton-ippm-2330-stdform-typep] [HYBRID] Trammell, B., Zheng, L., Berenguer, S., and M. Bagnulo,
Morton, A., Fabini, J., Elkins, N., mackermann@bcbsm.com, "Hybrid Measurement using IPPM Metrics", Work in Progress,
m., and V. Hegde, "IP Options and IPv6 Updates for IPPM's draft-trammell-ippm-hybrid-ps-01, February 2014.
Active Metric Framework: Packets of Type-P and Standard-
Formed Packets", draft-morton-ippm-2330-stdform-typep-02
(work in progress), December 2015.
[I-D.ietf-ippm-6man-pdm-option] [OPSAWG] Capello, A., Cociglio, M., Castaldelli, L., and A. Bonda,
"A packet based method for passive performance
monitoring", Work in Progress, draft-tempia-opsawg-p3m-04,
February 2014.
[PASSIVE] Zheng, L., Elkins, N., Lingli, D., Ackermann, M., and G.
Mirsky, "Framework for IP Passive Performance
Measurements", Work in Progress, draft-zheng-ippm-
framework-passive-03, February 2015.
[PDMOPTION]
Elkins, N. and M. Ackermann, "IPv6 Performance and Elkins, N. and M. Ackermann, "IPv6 Performance and
Diagnostic Metrics (PDM) Destination Option", draft-ietf- Diagnostic Metrics (PDM) Destination Option", Work in
ippm-6man-pdm-option-01 (work in progress), October 2015. Progress, draft-ietf-ippm-6man-pdm-option-02, April 2016.
[I-D.tempia-opsawg-p3m] [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay
Capello, A., Cociglio, M., Castaldelli, L., and A. Bonda, Measurement for MPLS Networks", RFC 6374,
"A packet based method for passive performance DOI 10.17487/RFC6374, September 2011,
monitoring", draft-tempia-opsawg-p3m-04 (work in <http://www.rfc-editor.org/info/rfc6374>.
progress), February 2014.
[I-D.chen-ippm-coloring-based-ipfpm-framework] [STDFORM] Morton, A., Fabini, J., Elkins, N., Ackermann, M., and V.
Chen, M., Zheng, L., Mirsky, G., and G. Fioccola, "IP Flow Hegde, "Updates for IPPM's Active Metric Framework:
Performance Measurement Framework", draft-chen-ippm- Packets of Type-P and Standard-Formed Packets", Work in
coloring-based-ipfpm-framework-04 (work in progress), July Progress, draft-morton-ippm-2330-stdform-typep-02,
2015. December 2015.
[I-D.zheng-ippm-framework-passive] [Y.1540] ITU-T, "Internet protocol data communication service - IP
Zheng, L., Elkins, N., Lingli, D., Ackermann, M., and G. packet transfer and availability performance parameters",
Mirsky, "Framework for IP Passive Performance March 2011,
Measurements", draft-zheng-ippm-framework-passive-03 (work <https://www.itu.int/rec/T-REC-Y.1540-201103-I/en>.
in progress), February 2015.
[I-D.trammell-ippm-hybrid-ps] [Y.1731] ITU-T, "Operation, administration and management (OAM)
Trammell, B., Zheng, L., Berenguer, S., and M. Bagnulo, functions and mechanisms for Ethernet-based networks",
"Hybrid Measurement using IPPM Metrics", draft-trammell- August 2015,
ippm-hybrid-ps-01 (work in progress), February 2014. <https://www.itu.int/rec/T-REC-G.8013-201508-I/en>.
[Y.1540] ITU-T Recommendation Y.1540, , "Internet protocol data Acknowledgements
communication service - IP packet transfer and
availability performance parameters", March 2011.
[Y.1731] ITU-T Recommendation Y.1731, , "Operation, administration Thanks to Mike Ackermann for asking the right question, and for
and management (OAM) functions and mechanisms for several suggestions on terminology. Brian Trammell provided key
Ethernet-based networks", October 2015. terms and references for the Passive category, and suggested ways to
expand the Hybrid description and types. Phil Eardley suggested some
hybrid scenarios for categorization as part of his review. Tiziano
Ionta reviewed the document and suggested the classification for the
"coloring" Method of Measurement. Nalini Elkins identified several
areas for clarification following her review. Bill Jouris, Stenio
Fernandes, and Spencer Dawkins suggested several editorial
improvements. Tal Mizrahi, Joachim Fabini, Greg Mirsky, and Mike
Ackermann raised many key considerations in their Working Group Last
Call (WGLC) reviews, based on their broad measurement experience.
Author's Address Author's Address
Al Morton Al Morton
AT&T Labs AT&T Labs
200 Laurel Avenue South 200 Laurel Avenue South
Middletown, NJ Middletown, NJ
USA United States
Email: acmorton@att.com Email: acmorton@att.com
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