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

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<front>
<title abbrev="Hybrid Measurement">
  Hybrid Measurement using IPPM Metrics
</title>  

<author fullname="Brian Trammell" 
      initials="B." surname="Trammell">
<organization abbrev="ETH Zurich">
  Swiss Federal Institute of Technology Zurich
</organization>
<address>
  <postal>
    <street>Gloriastrasse 35</street>
    <city>8092 Zurich</city>
    <country>Switzerland</country>
  </postal>
  <phone>+41 44 632 70 13</phone>
  <email>trammell@tik.ee.ethz.ch</email>
</address>
</author>

<date month="October" day="12" year="2012"/>
<area>Transport</area>
<workgroup>IP Performance Measurement (ippm)</workgroup>

<keyword>hybrid</keyword>
<keyword>passive</keyword>
<keyword>active</keyword>
<keyword>loss</keyword>
<keyword>delay</keyword>

<abstract>

<t>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 </t>

</abstract>
</front>
<middle>
<section title="Introduction">

    <t>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.</t>

    <t>The IPPM working group has produced a framework <xref
    target="RFC2330"/> for and rich set of well-defined metrics (e.g. <xref
    target="RFC2679"/>, <xref target="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.</t>

</section>

<section title="Problem Statement">

    <t>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 <xref target="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 these complications.</t>

    <t>The proposed specification entails:</t>

    <t><list style="symbols">

        <t>Definition of scenarios and requirements for hybrid
        measurement.</t>

        <t>Selection of existing IPPM metrics to be used for the active side
        of hybrid measurements to meet these requirements.</t>

        <t>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.</t>
        
        <t>Definition of metrics based on these passive methodologies,
        or modification of the definition of existing metrics to add passive
        methodologies.</t>

        <t>Definition of methods for comparison between active and passive
        metrics allowing for estimated uncertainty.</t>

        <t>Definition of methods for spatial and temporal composition of
        active and passive metrics together allowing for estimated
        uncertainty.</t>

    </list></t>

</section>

<section title="Scenarios and Requirements">
    
    <t>[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.]</t>
    
</section>

<section title="Selected IPPM Metrics">
    
    <t>[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.]</t>
    
</section>

<section title="Security Considerations">
    
    <t>[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.]</t>
    
</section>

<section title="IANA Considerations">
    
    <t>This document contains no considerations for IANA.</t>
    
</section>

</middle>
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<references title="Normative References">
    <?rfc include="reference.RFC.2330" ?>
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<references title="Informative References">
    <?rfc include="reference.RFC.2679" ?>
    <?rfc include="reference.RFC.2680" ?>
</references>
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