Internet DRAFT - draft-morton-ippm-registry-pdv
draft-morton-ippm-registry-pdv
Network Working Group A. Morton
Internet-Draft AT&T Labs
Intended status: Standards Track August 26, 2013
Expires: February 27, 2014
A Registry Investigation for IPPM Packet Delay Variation Metrics
draft-morton-ippm-registry-pdv-00
Abstract
This memo investigates a scheme to organize registry entries,
primarily those defined in RFCs prepared in the IP Performance
Metrics (IPPM) Working Group of the IETF. Three aspects make IPPM
metric registration difficult: (1) Use of the Type-P notion to allow
users to specify their own packet types. (2) Use of Flexible input
variables, called Parameters in IPPM definitions, some which
determine the quantity measured and others which should not be
specified until execution of the measurement. (3) Allowing
flexibility in choice of statistics to summarize the results on a
stream of measurement packets. Specifically, this memo investigates
registry entries that would follow from RFC 3393, the specification
IP Packet Delay Variation that allows for many different forms of
unique metrics, as a difficult and important test of the registry
structure.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on February 27, 2014.
Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. List of Registry Columns . . . . . . . . . . . . . . . . . . . 5
3.1. Element ID . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 5
3.3. Run-time Parameters . . . . . . . . . . . . . . . . . . . 6
3.4. Fixed Parameters . . . . . . . . . . . . . . . . . . . . . 6
3.5. Metric Definition . . . . . . . . . . . . . . . . . . . . 6
3.6. Metric Units (and Data Format?) . . . . . . . . . . . . . 6
3.7. Stream Type and Stream Parameters . . . . . . . . . . . . 6
3.8. Method of Measurement . . . . . . . . . . . . . . . . . . 7
3.9. Output Statistic . . . . . . . . . . . . . . . . . . . . . 7
3.10. Discussion/Remarks . . . . . . . . . . . . . . . . . . . . 7
4. Registry Column Entries for PDV . . . . . . . . . . . . . . . 7
4.1. Element ID . . . . . . . . . . . . . . . . . . . . . . . . 7
4.2. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 7
4.3. Run-time Parameters . . . . . . . . . . . . . . . . . . . 7
4.4. Fixed Parameters . . . . . . . . . . . . . . . . . . . . . 8
4.5. Metric Definition . . . . . . . . . . . . . . . . . . . . 8
4.6. Metric Units (and Data Format?) . . . . . . . . . . . . . 8
4.7. Stream Type and Stream Parameters . . . . . . . . . . . . 9
4.8. Method of Measurement . . . . . . . . . . . . . . . . . . 9
4.9. Output Statistic . . . . . . . . . . . . . . . . . . . . . 9
4.10. Discussion/Remarks . . . . . . . . . . . . . . . . . . . . 9
5. Registry Column Entries for IPDV . . . . . . . . . . . . . . . 10
5.1. Element ID . . . . . . . . . . . . . . . . . . . . . . . . 10
5.2. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 10
5.3. Run-time Parameters . . . . . . . . . . . . . . . . . . . 10
5.4. Fixed Parameters . . . . . . . . . . . . . . . . . . . . . 11
5.5. Metric Definition . . . . . . . . . . . . . . . . . . . . 11
5.6. Metric Units (and Data Format?) . . . . . . . . . . . . . 11
5.7. Stream Type and Stream Parameters . . . . . . . . . . . . 11
5.8. Method of Measurement . . . . . . . . . . . . . . . . . . 12
5.9. Output Statistic . . . . . . . . . . . . . . . . . . . . . 12
5.10. Discussion/Remarks . . . . . . . . . . . . . . . . . . . . 12
6. Security Considerations . . . . . . . . . . . . . . . . . . . 12
6.1. Denial of Service Attacks . . . . . . . . . . . . . . . . 12
6.2. User Data Confidentiality . . . . . . . . . . . . . . . . 13
6.3. Interference with the metrics . . . . . . . . . . . . . . 13
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
9.1. Normative References . . . . . . . . . . . . . . . . . . . 14
9.2. Informative References . . . . . . . . . . . . . . . . . . 14
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 15
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1. Introduction
This memo investigates a scheme to organize registry entries,
primarily those defined in RFCs prepared in the IP Performance
Metrics (IPPM) Working Group of the IETF, according to their
framework [RFC2330]. Three aspects make IPPM metric registration
difficult: (1) Use of the Type-P notion to allow users to specify
their own packet types. (2) Use of Flexible input variables, called
Parameters in IPPM definitions, some which determine the quantity
measured and others which should not be specified until execution of
the measurement. (3) Allowing flexibility in choice of statistics to
summarize the results on a stream of measurement packets.
Specifically, this memo investigates registry entries that would
follow from [RFC3393], the specification IP Packet Delay Variation
that allows for many different forms of unique metrics, as a
difficult and important test of the registry structure.
Although there are several standard templates for organizing
specifications of performance metrics (see [RFC2679] for an example
of the traditional IPPM template, based to large extent on the
Benchmarking Methodology Working Group's traditional template in
[RFC1242], and [RFC6390] for a similar template), none of these
templates were intended to become the basis for the columns of an
IETF-wide registry of metrics. As we examine the aspects of metric
specifications which need to appear in the registry, we will see that
none of the existing metric templates fully satisfies the needs of a
registry.
The authors of [draft-bagnulo-ippm-new-registry] and
[draft-bagnulo-ippm-new-registry-independent] made important
contributions to this memo in the registry column structure, and the
problem of registry development in general. We also acknowledge
input from the authors of [draft-claise-ippm-perf-metric-registry],
especially the value of an Element ID and the need for naming
conventions.
2. Scope
This memo investigates the registry structure that best describes
IPPM delay variation metrics based on [RFC3393] using the conventions
of the IPPM framework [RFC2330].
We find that the flexibility allowed in [RFC3393] requires further
specificity to have a metric worthy of registration, and we refer to
[RFC5481] for the needed definition details.
In this memo, we attempt a combinatoric registry, where all factors
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that can be reasonably specified ARE specified, and changing even one
factor would require a new registry entry (row). It is believed that
this exercise can also be instructive for a registry based on
independent factors, [draft-bagnulo-ippm-new-registry-independent]
but that topic is beyond the scope of this effort.
3. List of Registry Columns
This section briefly describes the columns used by this draft, as
this is likely to be a topic for discussion and revision. Taken as a
whole, the entries in the columns give a registered instance of a
metric with sufficient specificity to promote comparable results
across independent implementations. In other words, a complete
Metric Description.
3.1. Element ID
An integer having enough digits to uniquely identify each entry in
the Registry.
3.2. Metric Name
A metric naming convention is TBD.
The current guidance from Section 13 of [RFC2330], where Type-P is a
feature of all IPPM metric names, is:
"... we introduce the generic notion of a "packet of type P", where
in some contexts P will be explicitly defined (i.e., exactly what
type of packet we mean), partially defined (e.g., "with a payload of
B octets"), or left generic. Thus we may talk about generic IP-type-
P-connectivity or more specific IP-port-HTTP-connectivity. Some
metrics and methodologies may be fruitfully defined using generic
type P definitions which are then made specific when performing
actual measurements. Whenever a metric's value depends on the type
of the packets involved in the metric, the metric's name will include
either a specific type or a phrase such as "type-P". ..."
Registry entries are a context where Type-P must be defined.
IPPM Metric names have also included the typically included the
stream type, to distinguish between singleton and sample metrics (see
[RFC2330] for the definition of these terms).
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3.3. Run-time Parameters
Run-Time Parameters are input factors that must be determined,
configured into the measurement system, and reported with the results
for the context to be complete. However, the values of these
parameters is not specified in the Registry, rather these parameters
are listed as an aid to the measurement system implementor or user
(they must be left as variables, and supplied on execution).
Where metrics supply a list of Parameters as part of their
descriptive template, a sub-set of the Parameters will be designated
as Run-Time Parameters.
3.4. Fixed Parameters
Fixed Parameters are input factors that must be determined and
embedded in the measurement system for use when needed. The values
of these parameters is specified in the Registry.
Where metrics supply a list of Parameters as part of their
descriptive template, a sub-set of the Parameters will be designated
as Fixed Parameters.
A Parameter which is Fixed for one Registry element may be designated
as a Run-time Parameter for another Registry element.
3.5. Metric Definition
This entry provides references to relevant sections of the RFC(s)
defining the metric, as well as any supplemental information needed
to ensure an unambiguous definition for implementations.
3.6. Metric Units (and Data Format?)
The results of a metric must be expressed using some standard
dimension or units of measure. This column provides the units (and
if possible, the data format, whose specification will simplify both
measurement implementation and collection/storage tasks).
When a sample of singletons is collected, this entry will include the
data format and units of measure for each measured value.
3.7. Stream Type and Stream Parameters
Principally, two different streams are used in IPPM metrics, Poisson
distributed as described in [RFC2330] and Periodic as described in
[RFC3432]. Both Poisson and Periodic have their own unique
parameters, and the relevant set is specified in as Fixed Parameters
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in this column.
3.8. Method of Measurement
This entry provides references to relevant sections of the RFC(s)
describing the method of measurement, as well as any supplemental
information needed to ensure an unambiguous methods for
implementations.
3.9. Output Statistic
For entries which involve a stream and many singleton measurements, a
statistic may be specified in this column to summarize the results to
a single value.
3.10. Discussion/Remarks
Besides providing additional details which do not appear in other
columns, the Discussion/Remarks column allows for unforeseen issues
to be addressed by simply updating this Informational column.
4. Registry Column Entries for PDV
This is a complete Metric Description for one Packet Delay Variation
(PDV) metric.
4.1. Element ID
An integer with enough digits to uniquely identify the entry.
4.2. Metric Name
A metric naming convention is TBD.
One possibility based on IPPM's framework is:
IP-UDP-One-way-pdv-95th-percentile-Poisson
4.3. Run-time Parameters
Where metrics supply a list of Parameters as part of their
descriptive template, a sub-set of the Parameters will be designated
as Run-Time Parameters.
o Src, the IP address of a host
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o Dst, the IP address of a host
o T, a time (start of test interval)
o Tf, a time (end of test interval)
o T1, the wire time of the first packet in a pair, measured at
MP(Src) as it leaves for Dst.
o T2, the wire time of the second packet in a pair, measured at
MP(Src) as it leaves for Dst.
o I(i),I(i+1), i >=0, pairs of times which mark the beginning and
ending of the intervals in which the packet stream from which the
measurement is taken occurs. Here, I(0) = T0 and assuming that n
is the largest index, I(n) = Tf.
4.4. Fixed Parameters
Where metrics supply a list of Parameters as part of their
descriptive template, a sub-set of the Parameters will be designated
as Fixed Parameters.
o F, a selection function defining unambiguously the packets from
the stream selected for the metric. See section 4.2 of [RFC5481]
for the PDV form.
o L, a packet length in bits. L = 200 bits.
o Tmax, a maximum waiting time for packets to arrive at Dst, set
sufficiently long to disambiguate packets with long delays from
packets that are discarded (lost). Tmax = 3 seconds.
o Type-P, as defined in [RFC2330], which includes any field that may
affect a packet's treatment as it traverses the network. The
packets are IP/UDP, with DSCP = 0 (BE).
4.5. Metric Definition
See sections 2.4 and 3.4 of [RFC3393]. Singleton delay differences
measured are referred to by the variable name "ddT".
4.6. Metric Units (and Data Format?)
See section 3.3 of [RFC3393] for singleton elements.
[RFC2330] recommends that when a time is given, it will be expressed
in UTC.
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The timestamp format (for T, Tf, etc.) is the same as in [RFC5905]
(64 bits) and is as follows: the first 32 bits represent the unsigned
integer number of seconds elapsed since 0h on 1 January 1900; the
next 32 bits represent the fractional part of a second that has
elapsed since then.
The result format for ddT is *similar to* the short format in
[RFC5905] (32 bits) and is as follows: the first 16 bits represent
the *signed* integer number of seconds; the next 16 bits represent
the fractional part of a second.
4.7. Stream Type and Stream Parameters
Poisson distributed as described in [RFC2330], with the following
Parameters.
o lambda, a rate in reciprocal seconds (for Poisson Streams). lambda
= 1 packet per second
o Upper limit on Poisson distribution (values above this limit will
be clipped and set to the limit value). Upper limit = 30 seconds.
4.8. Method of Measurement
See section 2.6 and 3.6 of [RFC3393] for singleton elements.
4.9. Output Statistic
See section 4.3 of [RFC3393] for details on the percentile statistic.
The percentile = 95.
Individual results (singletons) should be represented by the
following triple
o T1 and T2, times as described above
o ddT as defined in section 2.4 of [RFC3393]
if needed.
4.10. Discussion/Remarks
Lost packets represent a challenge for delay variation metrics. See
section 4.1 of [RFC3393] and the delay variation applicability
statement[RFC5481] for extensive analysis and comparison of PDV and
IPDV.
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5. Registry Column Entries for IPDV
This is a complete Metric Description for one Inter-Packet Delay
Variation (IPDV) metric.
5.1. Element ID
An integer with enough digits to uniquely identify the entry.
5.2. Metric Name
A metric naming convention is TBD.
One possibility based on IPPM's framework is:
IP-UDP-One-way-ipdv-range-Periodic
5.3. Run-time Parameters
Where metrics supply a list of Parameters as part of their
descriptive template, a sub-set of the Parameters will be designated
as Run-Time Parameters.
o Src, the IP address of a host
o Dst, the IP address of a host
o T, the beginning of a time interval where a periodic sample is
desired.
o T0, a time that MUST be selected at random from the interval [T,
T+PdT] to start generating packets and taking measurements (start
of test interval)
o Tf, a time, greater than T0, for stopping generation of packets
for a sample (Tf may be relative to T0 if desired).
o T1, the wire time of the first packet in a pair, measured at
MP(Src) as it leaves for Dst.
o T2, the wire time of the second packet in a pair, measured at
MP(Src) as it leaves for Dst.
o I(i),I(i+1), i >=0, pairs of times which mark the beginning and
ending of the intervals in which the packet stream from which the
measurement is taken occurs. Here, I(0) = T0 and assuming that n
is the largest index, I(n) = Tf.
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5.4. Fixed Parameters
Where metrics supply a list of Parameters as part of their
descriptive template, a sub-set of the Parameters will be designated
as Fixed Parameters.
o F, a selection function defining unambiguously the packets from
the stream selected for the metric. See section 4.1 of [RFC5481]
for the IPDV form.
o L, a packet length in bits. L = 200 bits.
o Tmax, a maximum waiting time for packets to arrive at Dst, set
sufficiently long to disambiguate packets with long delays from
packets that are discarded (lost). Tmax = 3 seconds.
o Type-P, as defined in [RFC2330], which includes any field that may
affect a packet's treatment as it traverses the network. The
packets are IP/UDP, with DSCP = 0 (BE).
5.5. Metric Definition
See section 3.4 of [RFC3393].
5.6. Metric Units (and Data Format?)
See section 3.3 of [RFC3393] for singleton elements.
[RFC2330] recommends that when a time is given, it will be expressed
in UTC.
The timestamp format (for T, Tf, etc.) is the same as in [RFC5905]
(64 bits) and is as follows: the first 32 bits represent the unsigned
integer number of seconds elapsed since 0h on 1 January 1900; the
next 32 bits represent the fractional part of a second that has
elapsed since then.
The result format for ddT is *similar to* the short format in
[RFC5905] (32 bits) and is as follows: the first 16 bits represent
the *signed* integer number of seconds; the next 16 bits represent
the fractional part of a second (resolving 15 microseconds).
5.7. Stream Type and Stream Parameters
Periodic distributed as described in [RFC3432], with the following
Parameters.
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o incT, the nominal duration of inter-packet interval, first bit to
first bit (for Periodic Streams). incT = 1 second (per packet)
o PdT, the duration of the interval for allowed sample start times.
T0 may be drawn from a uniform distribution, such as T0 = T +
Unif(0,PdT), or other distribution for PdT.
5.8. Method of Measurement
See section 2.6 and 3.6 of [RFC3393] for singleton elements.
5.9. Output Statistic
See sections 5.2 and 6.5 of [RFC5481] for details on the range
statistic, or max(ddT) - min(ddT). Note that min(ddT) will almost
always be a negative value.
Individual results (singletons) should be represented by the
following triple
o T1 and T2, times as described above
o ddT as defined in section 2.4 of [RFC3393]
if needed.
5.10. Discussion/Remarks
Lost packets represent a challenge for delay variation metrics. See
section 4.1 of [RFC3393] and the delay variation applicability
statement[RFC5481] for extensive analysis and comparison of PDV and
IPDV.
6. Security Considerations
6.1. Denial of Service Attacks
The metrics in this memo require a stream of packets sent from one
host (source) to another host (destination) through intervening
networks, and back. This method could be abused for denial of
service attacks directed at the destination and/or the intervening
network(s).
Administrators of source, destination, and the intervening network(s)
should establish bilateral or multi-lateral agreements regarding the
timing, size, and frequency of collection of sample metrics. Use of
this method in excess of the terms agreed between the participants
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may be cause for immediate rejection or discard of packets or other
escalation procedures defined between the affected parties.
6.2. User Data Confidentiality
Active use of this method generates packets for a sample, rather than
taking samples based on user data, and does not threaten user data
confidentiality.
6.3. Interference with the metrics
It may be possible to identify that a certain packet or stream of
packets is part of a sample. With that knowledge at the destination
and/or the intervening networks, it is possible to change the
processing of the packets (e.g. increasing or decreasing delay) in a
way that may distort the measured performance. It may also be
possible to generate additional packets that appear to be part of the
sample metric. These additional packets are likely to perturb the
results of the sample measurement.
Authentication or encryption techniques, such as digital signatures,
MAY be used where appropriate to guard against injected traffic
attacks. [RFC5357] includes both authentication and encryption
features.
7. IANA Considerations
Metrics previously defined in IETF were registered in the IANA IPPM
METRICS REGISTRY, however this process was discontinued when the
registry structure was found to be inadequate, and the registry was
declared Obsolete [RFC6248].
Although the metrics in this draft may be considered for some form of
registration in the future, no IANA Action is requested at this time.
8. Acknowledgements
The author thanks Brian Trammell for suggesting the term "Run-time
Parameters", which led to the distinction between run-time and fixed
parameters implemented in this memo.
9. References
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9.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330,
May 1998.
[RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Delay Metric for IPPM", RFC 2679, September 1999.
[RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Packet Loss Metric for IPPM", RFC 2680, September 1999.
[RFC2681] Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
Delay Metric for IPPM", RFC 2681, September 1999.
[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
Metric for IP Performance Metrics (IPPM)", RFC 3393,
November 2002.
[RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network
performance measurement with periodic streams", RFC 3432,
November 2002.
[RFC4737] Morton, A., Ciavattone, L., Ramachandran, G., Shalunov,
S., and J. Perser, "Packet Reordering Metrics", RFC 4737,
November 2006.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, October 2008.
[RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
Time Protocol Version 4: Protocol and Algorithms
Specification", RFC 5905, June 2010.
9.2. Informative References
[RFC1242] Bradner, S., "Benchmarking terminology for network
interconnection devices", RFC 1242, July 1991.
[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation
Applicability Statement", RFC 5481, March 2009.
[RFC6248] Morton, A., "RFC 4148 and the IP Performance Metrics
(IPPM) Registry of Metrics Are Obsolete", RFC 6248,
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April 2011.
[RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New
Performance Metric Development", BCP 170, RFC 6390,
October 2011.
Author's Address
Al Morton
AT&T Labs
200 Laurel Avenue South
Middletown,, NJ 07748
USA
Phone: +1 732 420 1571
Fax: +1 732 368 1192
Email: acmorton@att.com
URI: http://home.comcast.net/~acmacm/
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