Internet DRAFT - draft-zheng-ippm-passive-gap-analysis
draft-zheng-ippm-passive-gap-analysis
Network Working Group L. Zheng
Internet-Draft S. Aldrin
Intended status: Informational Huawei Technologies
Expires: April 21, 2014 October 18, 2013
Gap Analysis of IPPM Passive Measurements
draft-zheng-ippm-passive-gap-analysis-00.txt
Abstract
This document performs a gap analysis of the current state of IPPM WG
and ongoing work, in terms of passive measurements, according to the
new charter of the IPPM WG.
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
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This Internet-Draft will expire on April 21, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Passive Measurements VS Active Measurements . . . . . . . . . 2
3. Gap Analysis for Passive Measurements . . . . . . . . . . . . 3
3.1. Framework for IP Performance Metrics . . . . . . . . . . 3
3.2. IP Performance Metrics . . . . . . . . . . . . . . . . . 4
3.3. Registry . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Future Work for Passive Measurement . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 5
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative References . . . . . . . . . . . . . . . . . . 6
8.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
1. Introduction
The IPPM working group has been recently re-chartered. According to
the new charter, passive measurement and hybrid measurement methods
are now included. This document performs a gap analysis of the
current status of work in the IPPM WG in terms of passive
measurements. Section 2 of the document gives a brief introduction
of passive measurement. Section 3 summarizes the current status of
the IPPM, and gives an analysis on what is missing or was not
considered, for passive measurements, in terms of framework of
metrics, measurement of metrics, registry, etc. Section 4 lists the
future work required for passive measurements based on the gap
analysis. The analysis for hybrid measurements is out of the scope
of this document.
2. Passive Measurements VS Active Measurements
Passive and active measurements are two common approaches for
monitoring the network. The passive approach measures real traffic
and does not increase the traffic on the network for the
measurements. This makes it attractive for in-service monitoring,
network trouble-shooting and fault location. Since the passive
approach may require viewing packets on the network, there can be
privacy or security issues. The active approach relies on the
capability to inject test packets into the network, but as such it
creates extra traffic. The benefit of active measurements is that
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they can be run from virtually anywhere in the network. One
difficulty, though, is that the discrete nature of active probing
limits the resolution of the measurements. There is also evidence of
limitations of probe-based packet loss measurement in low-loss
environments. Both passive and active measurements have their
strengths and should be regarded as complementary.
3. Gap Analysis for Passive Measurements
This section gives an analysis on what is missing for passive
measurements in relation to IPPM, in terms of framework of metrics,
measurement of metrics and registry.
3.1. Framework for IP Performance Metrics
The IETF IP Performance Metrics (IPPM) working group first created a
framework for metric development in [RFC2330], which enabled
development of many fundamental metrics. [RFC2330] has been updated
once by [RFC5835], which describes a detailed framework for composing
and aggregating metrics originally defined in [RFC2330].
The ongoing work [I-D.ietf-ippm-2330-update] proposes to update the
IPPM Framework with advanced considerations for measurement
methodology and testing. It describes new stream parameters for both
network characterization and support of application design using IPPM
metrics. All the previous work done for IP performance metrics
framework and the ongoing update for the framework has the
assumption, which is not explicitly stated, that the measurement
method of the metrics is active measurement.
The result of this is, while many of the current framework aspects
are still applicable to passive measurement, some of them are not
applicable. In one example, section 11 of [RFC2330] introduces a
separation between three distinct notions: singletons, samples, and
statistics, which are not applicable to passive measurements, since
the test packet is not required for passive measurements, nor is the
sampling.
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But there are certainly equivalent concepts in passive measurements.
For example, consider using TCP traffic to determine the two-way
delay between two hosts. A singleton would be the timing of a single
sequence number - acknowledgement pairing, a sample would be a
collection of these, and the statistical metric would take the
minimum, over a short time interval (in order to reduce or eliminate
think-time and delayed-ACK effects). In another example, the concept
of a packet of type "P", while still applicable in principle, will
have to be specified differently. An updated or new passive
framework document is needed, while equivalent concepts need to be
carried over as much as possible with passive-friendly definitions.
3.2. IP Performance Metrics
The IPPM WG has defined more than 30 metrics, the most recently
published document that defines metrics is [RFC6049]. The commonly
used metrics include IPPM Metrics for Measuring Connectivity
[RFC2678], One-way Delay Metrics[RFC2679], One-way Packet Loss
Metrics [RFC2680], Round-trip Delay Metrics [RFC2681], One-way Loss
Pattern Sample Metrics[RFC3357], IP Packet Delay Variation Metric
[RFC3393], IPPM Metrics for periodic streams [RFC3432] etc.
All the existing metrics defined follow the framework for IP
performance metrics [RFC2330] , which has the implicit assumption
that the measurement method of the metrics is active measurement.
Passive methodologies for existing [RFC2330] based active metrics
need to be defined, which would require loosening some of the
constraints as well as changes to the guidelines. For example, the
measurement methodologies for One-way Delay Metrics [RFC2679] and
One-way Packet Loss Metrics [RFC2680] call for, amongst other things,
selection of the Src and Dst addresses at the Src host. This will be
difficult to achieve for passive measurement.
Careful examination and thorough analysis needs to be made, in order
to decide, which aspects of current metrics need to be redefined for
passive measurements, and which aspects could be reused by passive
measurements as is.
3.3. Registry
[RFC4148] defines an initial registry of the metrics defined in the
IPPM WG and the rules to manage the registry. However, [RFC4148] was
obsoleted by [RFC6248] because it was "not believed to be feasible or
even useful to register every possible combination of Type P, metric
parameters, and Stream parameters using the current structure of the
IPPM Metrics Registry". This led to the [RFC4148] registry having
"very few users, if any".
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The ongoing work [I-D.bagnulo-ippm-new-registry-independent] and
[I-D.bagnulo-ippm-new-registry] creates, a registry for commonly used
metrics, defines the rules for assignments in the new registry and
performs initial allocations, respectively.
[I-D.bagnulo-ippm-new-registry-independent] proposes one particular
registry structure with independent registries for each of the fields
involved, while [I-D.bagnulo-ippm-new-registry] explores an
alternative structure with a single registry with multiple sub-
registries. The metrics for passive measurement should be taken into
consideration for both registry structure designs.
4. Future Work for Passive Measurement
Based on the above gap analysis, it could be concluded that the
following new work needs to be done in the IPPM working group:
1. Framework for metrics: An passive-friendly updated framework
document is needed for passive measurement.
2. Metrics: Careful examination on currently defined metrics,
particularly the measurement aspects, needs to be made by the working
group. Some metrics need to be updated for passive measurement, some
metrics may be reused by passive measurements as is. New metrics may
also need to be defined for passive measurement.
3. Registry: The passive measurement should be taken into
consideration for the ongoing registry structure design work.
5. Security Considerations
This document does not bring new security issue to IPPM.
6. IANA Considerations
This document makes no request to IANA.
7. Acknowledgements
The authors would like to thank Brain Trammell, Paul Coverdale for
their valuable comments.
8. References
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8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References
[I-D.bagnulo-ippm-new-registry-independent]
Bagnulo, M., Burbridge, T., Crawford, S., Eardley, P., and
A. Morton, "A registry for commonly used metrics.
Independent registries", draft-bagnulo-ippm-new-registry-
independent-01 (work in progress), July 2013.
[I-D.bagnulo-ippm-new-registry]
Bagnulo, M., Burbridge, T., Crawford, S., Eardley, P., and
A. Morton, "A registry for commonly used metrics", draft-
bagnulo-ippm-new-registry-01 (work in progress), July
2013.
[I-D.ietf-ippm-2330-update]
Fabini, J. and A. Morton, "Advanced Stream and Sampling
Framework for IPPM", draft-ietf-ippm-2330-update-01 (work
in progress), October 2013.
[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330, May
1998.
[RFC2678] Mahdavi, J. and V. Paxson, "IPPM Metrics for Measuring
Connectivity", RFC 2678, September 1999.
[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.
[RFC3357] Koodli, R. and R. Ravikanth, "One-way Loss Pattern Sample
Metrics", RFC 3357, August 2002.
[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
Metric for IP Performance Metrics (IPPM)", RFC 3393,
November 2002.
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[RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network
performance measurement with periodic streams", RFC 3432,
November 2002.
[RFC4148] Stephan, E., "IP Performance Metrics (IPPM) Metrics
Registry", BCP 108, RFC 4148, August 2005.
[RFC5835] Morton, A. and S. Van den Berghe, "Framework for Metric
Composition", RFC 5835, April 2010.
[RFC6049] Morton, A. and E. Stephan, "Spatial Composition of
Metrics", RFC 6049, January 2011.
[RFC6248] Morton, A., "RFC 4148 and the IP Performance Metrics
(IPPM) Registry of Metrics Are Obsolete", RFC 6248, April
2011.
Authors' Addresses
Lianshu Zheng
Huawei Technologies
China
Email: vero.zheng@huawei.com
Sam K. Aldrin
Huawei Technologies
Email: aldrin.ietf@gmail.com
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