One document matched: draft-trammell-ippm-hybrid-ps-00.txt

IP Performance Measurement (ippm)                            B. Trammell
Internet-Draft                                                ETH Zurich
Intended status: Informational                          October 12, 2012
Expires: April 15, 2013


                 Hybrid Measurement using IPPM Metrics
                  draft-trammell-ippm-hybrid-ps-00.txt

Abstract

   Hybrid measurement is the combination of metrics derived from passive
   and active measurement to produce a measurement result.  This
   document discusses use cases for hybrid measurement using metrics
   defined within the IPPM framework

Status of this Memo

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1.  Introduction

   Hybrid measurement is the combination of metrics derived from passive
   and active measurement to produce a measurement result.  This
   combination can be either spatial or temporal.  For example, one way
   delay to a given endpoint could be derived from passive measurements
   from a sample of remote endpoints with which traffic is frequently
   exchanged, and supplemented with active measurements from endpoints
   with less frequent traffic, to build a "delay map" to a certain point
   in the network.  On the temporal side, loss or delay metrics could be
   passively measured and stored over time to provide a baseline against
   which actively-measured loss or delay metrics could be compared
   during troubleshooting, in order to determine whether a specific path
   or path segment is contributing to an observed performance problem.

   The IPPM working group has produced a framework [RFC2330] for and
   rich set of well-defined metrics (e.g.  [RFC2679], [RFC2680]) for IP
   performance measurement using active methods, and protocols for
   measuring them.  These metrics could form the basis of a platform for
   hybrid measurement, provided that passively-derived metrics were
   defined to compatible with the corresponding actively-derived
   metrics; or alternately, provided that methodologies for passive
   measurement can be defined for each of the existing active metrics to
   be used, such that those methodologies produce values for the metrics
   equivalent to the active methodology for the same metric parameters,
   given some assumptions about the packet stream to be observed to
   perform the passive measurement, and given tolerances for uncertainty
   in the results.


2.  Problem Statement

   Complicating the definition of hybrid measurements is that passive
   measurement must make do with the traffic that is observable, while
   active measurement has some control over the traffic observed.
   Measurements for some set of parameters are not possible if no
   suitable traffic is observed, and the timing of the measurement
   cannot be controlled.  Placement of the observation points for
   passive measurement along a path additionally introduces uncertainty
   in the results.  For example, passive one-way delay measurement could
   be performed using two measurement points, one close to each
   endpoint, with synchronized clocks, comparing the observation times
   of packets via their hashes.  This will not produce a value which is
   directly comparable to a Type-P-One-way-Delay measured as specified
   in section 3.6 of [RFC2679], because it will not account for the one-
   way-delay from the source to the source-side observation point, or
   from the destination-side observation point to the destination.  Any
   specification of hybrid measurement using IPPM metrics must handle



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   these complications.

   The proposed specification entails:

   o  Definition of scenarios and requirements for hybrid measurement.

   o  Selection of existing IPPM metrics to be used for the active side
      of hybrid measurements to meet these requirements.

   o  Definition of equivalent passive measurement methodologies for
      each selected metric, specifically addressing the assumptions
      about the observed packet stream which must hold for the metric to
      be valid, and with a specific allowance for the measurement and/or
      estimation of uncertainty due to uncontrollable conditions or
      observation point placement.

   o  Definition of metrics based on these passive methodologies, or
      modification of the definition of existing metrics to add passive
      methodologies.

   o  Definition of methods for comparison between active and passive
      metrics allowing for estimated uncertainty.

   o  Definition of methods for spatial and temporal composition of
      active and passive metrics together allowing for estimated
      uncertainty.


3.  Scenarios and Requirements

   [EDITOR'S NOTE: This section will contain scenarios and requirements
   for hybrid measurement.  Candidate scenarios include (1) use of
   passive measurement to measure delay, loss, etc. on paths on which
   traffic is frequently sent, supplemented with active measurement on
   low-traffic paths or during low-traffic times and (2) use of passive
   measurement to establish a long-term baseline against which active
   measurements can be compared to detect and isolate anomalies, as in
   the introduction.]


4.  Selected IPPM Metrics

   [EDITOR'S NOTE: this section will contain information on the metrics
   selected for passive measurement, and initial discussion of passive
   measurement methodologies for them.  Metric definition will
   presumably be left for a future document.]





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5.  Security Considerations

   [EDITOR'S NOTE: this section will discuss general security
   considerations of using passive measurement for performance, both on
   the potential for attacks against the measurement system as well as
   the potential for privacy or security threats posed by the
   measurement system itself.]


6.  IANA Considerations

   This document contains no considerations for IANA.


7.  References

7.1.  Normative References

   [RFC2330]  Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
              "Framework for IP Performance Metrics", RFC 2330,
              May 1998.

7.2.  Informative References

   [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.


Author's Address

   Brian Trammell
   Swiss Federal Institute of Technology Zurich
   Gloriastrasse 35
   8092 Zurich
   Switzerland

   Phone: +41 44 632 70 13
   Email: trammell@tik.ee.ethz.ch










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