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Network Working Group                                         M. Bagnulo
Internet-Draft                                                      UC3M
Intended status: Best Current Practice                         B. Claise
Expires: January 7, 2016                             Cisco Systems, Inc.
                                                              P. Eardley
                                                                      BT
                                                               A. Morton
                                                               AT&T Labs
                                                               A. Akhter
                                                              Consultant
                                                            July 6, 2015


                    Registry for Performance Metrics
                   draft-ietf-ippm-metric-registry-03

Abstract

   This document defines the IANA Registry for Performance Metrics.
   This document also gives a set of guidelines for Registered
   Performance Metric requesters and reviewers.

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."

   This Internet-Draft will expire on January 7, 2016.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Open Issues . . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   5
   4.  Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Motivation for a Performance Metrics Registry . . . . . . . .   7
     5.1.  Interoperability  . . . . . . . . . . . . . . . . . . . .   7
     5.2.  Single point of reference for Performance Metrics . . . .   8
     5.3.  Side benefits . . . . . . . . . . . . . . . . . . . . . .   8
   6.  Criteria for Performance Metrics Registration . . . . . . . .   8
   7.  Performance Metric Registry: Prior attempt  . . . . . . . . .   9
     7.1.  Why this Attempt Will Succeed . . . . . . . . . . . . . .  10
   8.  Definition of the Performance Metric Registry . . . . . . . .  10
     8.1.  Summary Category  . . . . . . . . . . . . . . . . . . . .  11
       8.1.1.  Identifier  . . . . . . . . . . . . . . . . . . . . .  11
       8.1.2.  Name  . . . . . . . . . . . . . . . . . . . . . . . .  12
       8.1.3.  URI . . . . . . . . . . . . . . . . . . . . . . . . .  13
       8.1.4.  Description . . . . . . . . . . . . . . . . . . . . .  13
     8.2.  Metric Definition Category  . . . . . . . . . . . . . . .  13
       8.2.1.  Reference Definition  . . . . . . . . . . . . . . . .  13
       8.2.2.  Fixed Parameters  . . . . . . . . . . . . . . . . . .  13
     8.3.  Method of Measurement Category  . . . . . . . . . . . . .  14
       8.3.1.  Reference Method  . . . . . . . . . . . . . . . . . .  14
       8.3.2.  Packet Generation Stream  . . . . . . . . . . . . . .  14
       8.3.3.  Traffic Filter  . . . . . . . . . . . . . . . . . . .  15
       8.3.4.  Sampling Distribution . . . . . . . . . . . . . . . .  15
       8.3.5.  Run-time Parameters . . . . . . . . . . . . . . . . .  16
       8.3.6.  Role  . . . . . . . . . . . . . . . . . . . . . . . .  16
     8.4.  Output Category . . . . . . . . . . . . . . . . . . . . .  16
       8.4.1.  Type  . . . . . . . . . . . . . . . . . . . . . . . .  16
       8.4.2.  Reference Definition  . . . . . . . . . . . . . . . .  17
       8.4.3.  Metric Units  . . . . . . . . . . . . . . . . . . . .  17
     8.5.  Administrative information  . . . . . . . . . . . . . . .  17
       8.5.1.  Status  . . . . . . . . . . . . . . . . . . . . . . .  17
       8.5.2.  Requester . . . . . . . . . . . . . . . . . . . . . .  17
       8.5.3.  Revision  . . . . . . . . . . . . . . . . . . . . . .  17
       8.5.4.  Revision Date . . . . . . . . . . . . . . . . . . . .  17
     8.6.  Comments and Remarks  . . . . . . . . . . . . . . . . . .  17
   9.  The Life-Cycle of Registered Metrics  . . . . . . . . . . . .  18
     9.1.  Adding new Performance Metrics to the Registry  . . . . .  18
     9.2.  Revising Registered Performance Metrics . . . . . . . . .  19



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     9.3.  Deprecating Registered Performance Metrics  . . . . . . .  20
   10. Security considerations . . . . . . . . . . . . . . . . . . .  21
   11. IANA Considerations . . . . . . . . . . . . . . . . . . . . .  21
   12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .  22
   13. References  . . . . . . . . . . . . . . . . . . . . . . . . .  22
     13.1.  Normative References . . . . . . . . . . . . . . . . . .  22
     13.2.  Informative References . . . . . . . . . . . . . . . . .  23
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  24

1.  Open Issues

   1.  Define the Filter column subcolumns, i.e. how filters are
       expressed.

   2.  Need to include an example for a passive metric

   3.  Shall we remove the definitions of active and passive?  If we
       remove it, shall we keep all the related comments in the draft?

   4.  URL: should we include a URL link in each registry entry with a
       URL specific to the entry that links to a different text page
       that contains all the details of the registry entry as in
       http://www.iana.org/assignments/xml-registry/xml-
       registry.xhtml#ns

   5.  As discussed between Marcelo and Benoit, modify "defines" in the
       Parameter definition.  Reasoning: the distinction between a new
       performance metric and a parameter is not clear.  If it's defined
       as a variable, is it a new perf metric?  "All Parameters must be
       known to measure using a metric": well, if it's a new perf
       metric, we don't have the problem.  And state what the parameter
       is the example.

   6.  As discussed between Marcelo and Benoit, can we find a Parameter
       for passive monitoring?  The sampling distribution is a fixed
       Parameter, right?  Because it's needed "to interpret the
       results", as mentioned in the Parameter definition.

   7.  We miss a new Parameter section that explains the link between
       Parameters, Fixed Parameters, Run-time Parameters, and
       potentially stream parameters.  We must also add in this section
       that "Differences in values for a fixed parameters implies a new
       registry entries"

   8.  The double definitions are annoying: Registered Performance
       Metric = Registered Metric, and Performance Metrics Registry =
       Registry.  I (Benoit) am in favor to only keep a single
       definition (the longest one), and be consistent



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2.  Introduction

   The IETF specifies and uses Performance Metrics of protocols and
   applications transported over its protocols.  Performance metrics are
   such an important part of the operations of IETF protocols that
   [RFC6390] specifies guidelines for their development.

   The definition and use of Performance Metrics in the IETF happens in
   various working groups (WG), most notably:

      The "IP Performance Metrics" (IPPM) WG is the WG primarily
      focusing on Performance Metrics definition at the IETF.

      The "Metric Blocks for use with RTCP's Extended Report Framework"
      (XRBLOCK) WG recently specified many Performance Metrics related
      to "RTP Control Protocol Extended Reports (RTCP XR)" [RFC3611],
      which establishes a framework to allow new information to be
      conveyed in RTCP, supplementing the original report blocks defined
      in "RTP: A Transport Protocol for Real-Time Applications",
      [RFC3550].

      The "Benchmarking Methodology" WG (BMWG) defined many Performance
      Metrics for use in laboratory benchmarking of inter-networking
      technologies.

      The "IP Flow Information eXport" (IPFIX) concluded WG specified an
      IANA process for new Information Elements.  Some Performance
      Metrics related Information Elements are proposed on regular
      basis.

      The "Performance Metrics for Other Layers" (PMOL) concluded WG,
      defined some Performance Metrics related to Session Initiation
      Protocol (SIP) voice quality [RFC6035].

   It is expected that more Performance Metrics will be defined in the
   future, not only IP-based metrics, but also metrics which are
   protocol-specific and application-specific.

   However, despite the importance of Performance Metrics, there are two
   related problems for the industry.  First, how to ensure that when
   one party requests another party to measure (or report or in some way
   act on) a particular Performance Metric, then both parties have
   exactly the same understanding of what Performance Metric is being
   referred to.  Second, how to discover which Performance Metrics have
   been specified, so as to avoid developing new Performance Metric that
   is very similar, but not quite inter-operable.  The problems can be
   addressed by creating a registry of performance metrics.  The usual
   way in which IETF organizes namespaces is with Internet Assigned



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   Numbers Authority (IANA) registries, and there is currently no
   Performance Metrics Registry maintained by the IANA.

   This document therefore creates an IANA-maintained Performance
   Metrics Registry.  It also provides best practices on how to specify
   new entries or update ones in the Performance Metrics Registry.

3.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

   Performance Metric:  A Performance Metric is a quantitative measure
      of performance, targeted to an IETF-specified protocol or targeted
      to an application transported over an IETF-specified protocol.
      Examples of Performance Metrics are the FTP response time for a
      complete file download, the DNS response time to resolve the IP
      address, a database logging time, etc.  This definition is
      consistent with the definition of metric in [RFC2330] and broader
      than the definition of performance metric in [RFC6390].

   Registered Performance Metric:  A Registered Performance Metric (or
      Registered Metric) is a Performance Metric expressed as an entry
      in the Performance Metric Registry, administered by IANA.  Such a
      performance metric has met all the registry review criteria
      defined in this document in order to included in the registry.

   Performance Metrics Registry:  The IANA registry containing
      Registered Performance Metrics.  In this document, it is also
      called simply "Registry".

   Proprietary Registry:  A set of metrics that are registered in a
      proprietary registry, as opposed to Performance Metrics Registry.

   Performance Metrics Experts:  The Performance Metrics Experts is a
      group of designated experts [RFC5226] selected by the IESG to
      validate the Performance Metrics before updating the Performance
      Metrics Registry.  The Performance Metrics Experts work closely
      with IANA.

   Parameter:  An input factor defined as a variable in the definition
      of a Performance Metric.  A numerical or other specified factor
      forming one of a set that defines a metric or sets the conditions
      of its operation.  All Parameters must be known to measure using a
      metric and interpret the results.  Although Parameters do not
      change the fundamental nature of the Performance Metric's



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      definition, some have substantial influence on the network
      property being assessed and interpretation of the results.

         Note: Consider the case of packet loss in the following two
         Active Measurement Method cases.  The first case is packet loss
         as background loss where the parameter set includes a very
         sparse Poisson stream, and only characterizes the times when
         packets were lost.  Actual user streams likely see much higher
         loss at these times, due to tail drop or radio errors.  The
         second case is packet loss as inverse of throughput where the
         parameter set includes a very dense, bursty stream, and
         characterizes the loss experienced by a stream that
         approximates a user stream.  These are both "loss metrics", but
         the difference in interpretation of the results is highly
         dependent on the Parameters (at least), to the extreme where we
         are actually using loss to infer its compliment: delivered
         throughput.

   Active Measurement Method:  Methods of Measurement conducted on
      traffic which serves only the purpose of measurement and is
      generated for that reason alone, and whose traffic characteristics
      are known a priori.  Examples of Active Measurement Methods are
      the measurement methods for the One way delay metric defined in
      [RFC2679] and the one for round trip delay defined in [RFC2681].

   Passive Measurement Method:  Methods of Measurement conducted on
      network traffic, generated either from the end users or from
      network elements.  One characteristic of Passive Measurement
      Methods is that sensitive information may be observed, and as a
      consequence, stored in the measurement system.

4.  Scope

   This document is meant for two different audiences.  For those
   defining new Registered Performance Metrics, it provides
   specifications and best practices to be used in deciding which
   Registered Metrics are useful for a measurement study, instructions
   for writing the text for each column of the Registered Metrics, and
   information on the supporting documentation required for the new
   Registry entry (up to and including the publication of one or more
   RFCs or I-Ds describing it).  For the appointed Performance Metrics
   Experts and for IANA personnel administering the new IANA Performance
   Metric Registry, it defines a set of acceptance criteria against
   which these proposed Registered Performance Metrics should be
   evaluated.

   This Performance Metric Registry is applicable to Performance Metrics
   issued from Active Measurement, Passive Measurement, and any other



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   form of Performance Metric.  This registry is designed to encompass
   Performance Metrics developed throughout the IETF and especially for
   the technologies specified in the following working groups: IPPM,
   XRBLOCK, IPFIX, and BMWG.  This document analyzes an prior attempt to
   set up a Performance Metric Registry, and the reasons why this design
   was inadequate [RFC6248].  Finally, this document gives a set of
   guidelines for requesters and expert reviewers of candidate
   Registered Performance Metrics.

   This document makes no attempt to populate the Registry with initial
   entries.  It does provides a few examples that are merely
   illustrations and should not be included in the registry at this
   point in time.

   Based on [RFC5226] Section 4.3, this document is processed as Best
   Current Practice (BCP) [RFC2026].

5.  Motivation for a Performance Metrics Registry

   In this section, we detail several motivations for the Performance
   Metric Registry.

5.1.  Interoperability

   As any IETF registry, the primary use for a registry is to manage a
   namespace for its use within one or more protocols.  In the
   particular case of the Performance Metric Registry, there are two
   types of protocols that will use the Performance Metrics in the
   Registry during their operation (by referring to the Index values):

   o  Control protocol: this type of protocols is used to allow one
      entity to request another entity to perform a measurement using a
      specific metric defined by the Registry.  One particular example
      is the LMAP framework [I-D.ietf-lmap-framework].  Using the LMAP
      terminology, the Registry is used in the LMAP Control protocol to
      allow a Controller to request a measurement task to one or more
      Measurement Agents.  In order to enable this use case, the entries
      of the Performance Metric Registry must be well enough defined to
      allow a Measurement Agent implementation to trigger a specific
      measurement task upon the reception of a control protocol message.
      This requirement heavily constrains the type of entries that are
      acceptable for the Performance Metric Registry.

   o  Report protocol: This type of protocols is used to allow an entity
      to report measurement results to another entity.  By referencing
      to a specific Performance Metric Registry, it is possible to
      properly characterize the measurement result data being reported.
      Using the LMAP terminology, the Registry is used in the Report



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      protocol to allow a Measurement Agent to report measurement
      results to a Collector.

5.2.  Single point of reference for Performance Metrics

   A Performance Metrics Registry serves as a single point of reference
   for Performance Metrics defined in different working groups in the
   IETF.  As we mentioned earlier, there are several WGs that define
   Performance Metrics in the IETF and it is hard to keep track of all
   them.  This results in multiple definitions of similar Performance
   Metrics that attempt to measure the same phenomena but in slightly
   different (and incompatible) ways.  Having a Registry would allow
   both the IETF community and external people to have a single list of
   relevant Performance Metrics defined by the IETF (and others, where
   appropriate).  The single list is also an essential aspect of
   communication about Performance Metrics, where different entities
   that request measurements, execute measurements, and report the
   results can benefit from a common understanding of the referenced
   Performance Metric.

5.3.  Side benefits

   There are a couple of side benefits of having such a Registry.
   First, the Registry could serve as an inventory of useful and used
   Performance Metrics, that are normally supported by different
   implementations of measurement agents.  Second, the results of
   measurements using the Performance Metrics would be comparable even
   if they are performed by different implementations and in different
   networks, as the Performance Metric is properly defined.  BCP 176
   [RFC6576] examines whether the results produced by independent
   implementations are equivalent in the context of evaluating the
   completeness and clarity of metric specifications.  This BCP defines
   the standards track advancement testing for (active) IPPM metrics,
   and the same process will likely suffice to determine whether
   Registered Performance Metrics are sufficiently well specified to
   result in comparable (or equivalent) results.  Registered Performance
   Metrics which have undergone such testing SHOULD be noted, with a
   reference to the test results.

6.  Criteria for Performance Metrics Registration

   It is neither possible nor desirable to populate the Registry with
   all combinations of Parameters of all Performance Metrics.  The
   Registered Performance Metrics should be:

   1.  interpretable by the user.

   2.  implementable by the software designer,



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   3.  deployable by network operators,

   4.  accurate, for interoperability and deployment across vendors,

   5.  Operationally useful, so that it has significant industry
       interest and/or has seen deployment,

   6.  Sufficiently tightly defined, so that different values for the
       Run-time Parameters does not change the fundamental nature of the
       measurement, nor change the practicality of its implementation.

   In essence, there needs to be evidence that a candidate Registered
   Performance Metric has significant industry interest, or has seen
   deployment, and there is agreement that the candidate Registered
   Performance Metric serves its intended purpose.

7.  Performance Metric Registry: Prior attempt

   There was a previous attempt to define a metric registry RFC 4148
   [RFC4148].  However, it was obsoleted by RFC 6248 [RFC6248] because
   it was "found to be insufficiently detailed to uniquely identify IPPM
   metrics... [there was too much] variability possible when
   characterizing a metric exactly" which led to the RFC4148 registry
   having "very few users, if any".

   A couple of interesting additional quotes from RFC 6248 might help
   understand the issues related to that registry.

   1.  "It is 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."

   2.  "The registry structure has been found to be insufficiently
       detailed to uniquely identify IPPM metrics."

   3.  "Despite apparent efforts to find current or even future users,
       no one responded to the call for interest in the RFC 4148
       registry during the second half of 2010."

   The current approach learns from this by tightly defining each
   Registered Performance Metric with only a few variable (Run-time)
   Parameters to be specified by the measurement designer, if any.  The
   idea is that entries in the Registry stem from different measurement
   methods which require input (Run-time) parameters to set factors like
   source and destination addresses (which do not change the fundamental
   nature of the measurement).  The downside of this approach is that it
   could result in a large number of entries in the Registry.  There is



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   agreement that less is more in this context - it is better to have a
   reduced set of useful metrics rather than a large set of metrics,
   some with with questionable usefulness.

7.1.  Why this Attempt Will Succeed

   As mentioned in the previous section, one of the main issues with the
   previous registry was that the metrics contained in the registry were
   too generic to be useful.  This document specifies stricter criteria
   for performance metric registration (see section 6), and imposes a
   group of Performance Metrics Experts that will provide guidelines to
   assess if a Performance Metric is properly specified.

   Another key difference between this attempt and the previous one is
   that in this case there is at least one clear user for the Registry:
   the LMAP framework and protocol.  Because the LMAP protocol will use
   the Registry values in its operation, this actually helps to
   determine if a metric is properly defined.  In particular, since we
   expect that the LMAP control protocol will enable a controller to
   request a measurement agent to perform a measurement using a given
   metric by embedding the Performance Metric Registry value in the
   protocol, a metric is properly specified if it is defined well-enough
   so that it is possible (and practical) to implement the metric in the
   measurement agent.  This was the failure of the previous attempt: a
   registry entry with an undefined Type-P (section 13 of RFC 2330
   [RFC2330]) allows implementation to be ambiguous.

8.  Definition of the Performance Metric Registry

   In this section we define the columns of the Performance Metric
   Registry.  This Performance Metric Registry is applicable to
   Performance Metrics issued from Active Measurement, Passive
   Measurement, and any other form of Performance Metric.  Because of
   that, it may be the case that some of the columns defined are not
   applicable for a given type of metric.  If this is the case, the
   column(s) SHOULD be populated with the "NA" value (Non Applicable).
   However, the "NA" value MUST NOT be used by any metric in the
   following columns: Identifier, Name, URI, Status, Requester,
   Revision, Revision Date, Description.  In addition, it may be
   possible that, in the future, a new type of metric requires
   additional columns.  Should that be the case, it is possible to add
   new columns to the registry.  The specification defining the new
   column(s) must define how to populate the new column(s) for existing
   entries.

   The columns of the Performance Metric Registry are defined next.  The
   columns are grouped into "Categories" to facilitate the use of the
   registry.  Categories are described at the 8.x heading level, and



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   columns are at the 8.x.y heading level.  The Figure below illustrates
   this organization.  An entry (row) therefore gives a complete
   description of a Registered Metric.

   Each column serves as a check-list item and helps to avoid omissions
   during registration and expert review.

 Registry Categories and Columns, shown as
    Category
    ------------------
    Column |  Column |

    Summary
        -------------------------------
        Identifier  | Name | URI | Description |

        Metric Definition
        -----------------------------------------
        Reference Definition | Fixed Parameters |

        Method of Measurement
    ---------------------------------------------------------------------
    Reference | Packet     | Traffic | Sampling     | Run-time   | Role |
    Method    | Generation | Filter  | Distribution | Parameters |      |
              | Stream     |
    Output
    -----------------------------
    | Type | Reference  | Units |
    |      | Definition |       |

    Administrative Information
    ----------------------------------
    Status |Request | Rev | Rev.Date |

    Comments and Remarks
        --------------------


8.1.  Summary Category

8.1.1.  Identifier

   A numeric identifier for the Registered Performance Metric.  This
   identifier MUST be unique within the Performance Metric Registry.

   The Registered Performance Metric unique identifier is a 16-bit
   integer (range 0 to 65535).  When adding newly Registered Performance
   Metrics to the Performance Metric Registry, IANA should assign the



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   lowest available identifier to the next Registered Performance
   Metric.

8.1.2.  Name

   As the name of a Registered Performance Metric is the first thing a
   potential implementor will use when determining whether it is
   suitable for a given application, it is important to be as precise
   and descriptive as possible.

   New names of Registered Performance Metrics:

   1.  "MUST be chosen carefully to describe the Registered Performance
       Metric and the context in which it will be used."

   2.  "MUST be unique within the Performance Metric Registry."

   3.  "MUST use capital letters for the first letter of each component.
       All other letters MUST be lowercase, even for acronyms.
       Exceptions are made for acronyms containing a mixture of
       lowercase and capital letters, such as 'IPv4' and 'IPv6'."

   4.  MUST use '_' between each component of the Registered Performance
       Metric name.

   5.  MUST start with prefix Act_ for active measurement Registered
       Performance Metric.

   6.  MUST start with prefix Pas_ for passive monitoring Registered
       Performance Metric.

   7.  Other types of Performance Metric should define a proper prefix
       for identifying the type.

   8.  Some examples of names of passive metrics might be:
       Pas_L3_L4_Octets (Layer 3 and 4 level accounting of bytes
       observed), Pas_DNS_RTT (Round Trip Time of in DNS query response
       of observed traffic), and Pas_L3_TCP_RTT (Passively observed
       round trip time in TCP handshake organized with L3 addresses)

   9.  The remaining rules for naming are left for the Performance
       Metric Experts to determine as they gather experience, so this is
       an area of planned update by a future RFC

   An example is "Act_UDP_Latency_Poisson_99mean" for a active
   monitoring UDP latency metric using a Poisson stream of packets and
   producing the 99th percentile mean as output.




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8.1.3.  URI

   The URI column MUST contain a URI [RFC3986] that uniquely identified
   the Registered Performance Metric.  The URI is a URN [RFC2141].  The
   URI is automatically generated by prepending the prefix
   urn:ietf:params:ippm:metric: to the metric name.  The resulting URI
   is globally unique.

8.1.4.  Description

   A Registered Performance Metric description is a written
   representation of a particular Registry entry.  It supplements the
   Registered Performance Metric name to help Registry users select
   relevant Registered Performance Metrics.

8.2.  Metric Definition Category

   This category includes columns to prompt all necessary details
   related to the metric definition, including the RFC reference and
   values of input factors, called fixed parameters, which are left open
   in the RFC but have a particular value defined by the performance
   metric.

8.2.1.  Reference Definition

   This entry provides a reference (or references) to the relevant
   section(s) of the document(s) that define the metric, as well as any
   supplemental information needed to ensure an unambiguous definition
   for implementations.  The reference needs to be an immutable
   document, such as an RFC; for other standards bodies, it is likely to
   be necessary to reference a specific, dated version of a
   specification.

8.2.2.  Fixed Parameters

   Fixed Parameters are Paremeters whose value must be specified in the
   Registry.  The measurement system uses these values.

   Where referenced metrics supply a list of Parameters as part of their
   descriptive template, a sub-set of the Parameters will be designated
   as Fixed Parameters.  For example, for active metrics, Fixed
   Parameters determine most or all of the IPPM Framework convention
   "packets of Type-P" as described in [RFC2330], such as transport
   protocol, payload length, TTL, etc.  An example for passive metrics
   is for RTP packet loss calculation that relies on the validation of a
   packet as RTP which is a multi-packet validation controlled by
   MIN_SEQUENTIAL as defined by [RFC3550].  Varying MIN_SEQUENTIAL




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   values can alter the loss report and this value could be set as a
   Fixed Parameter

   A Parameter which is a Fixed Parameter for one Registry entry may be
   designated as a Run-time Parameter for another Registry entry.

8.3.  Method of Measurement Category

   This category includes columns for references to relevant sections of
   the RFC(s) and any supplemental information needed to ensure an
   unambiguous method for implementations.

8.3.1.  Reference Method

   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 unambiguous interpretation for
   implementations referring to the RFC text.

   Specifically, this section should include pointers to pseudocode or
   actual code that could be used for an unambigious implementation.

8.3.2.  Packet Generation Stream

   This column applies to Performance Metrics that generate traffic for
   a part of their Measurement Method purposes including but not
   necessarily limited to Active metrics.  The generated traffic is
   referred as stream and this columns describe its characteristics.

   Each entry for this column contains the following information:

   o  Value: The name of the packet stream scheduling discipline

   o  Stream Parameters: The values and formats of input factors for
      each type of stream.  For example, the average packet rate and
      distribution truncation value for streams with Poisson-distributed
      inter-packet sending times.

   o  Reference: the specification where the stream is defined

   The simplest example of stream specification is Singleton scheduling
   (see [RFC2330]), where a single atomic measurement is conducted.
   Each atomic measurement could consist of sending a single packet
   (such as a DNS request) or sending several packets (for example, to
   request a webpage).  Other streams support a series of atomic
   measurements in a "sample", with a schedule defining the timing
   between each transmitted packet and subsequent measurement.
   Principally, two different streams are used in IPPM metrics, Poisson



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   distributed as described in [RFC2330] and Periodic as described in
   [RFC3432].  Both Poisson and Periodic have their own unique
   parameters, and the relevant set of values is specified in this
   column.

8.3.3.  Traffic Filter

   This column applies to Performance Metrics that observe packets
   flowing through (the device with) the measurement agent i.e. that is
   not necessarily addressed to the measurement agent.  This includes
   but is not limited to Passive Metrics.  The filter specifies the
   traffic that is measured.  This includes protocol field values/
   ranges, such as address ranges, and flow or session identifiers.

   The traffic filter itself depends on needs of the metric itself and a
   balance of operators measurement needs and user's need for privacy.
   Mechanics for conveying the filter criteria might be the BPF (Berkley
   Packet Filter) or PSAMP [RFC5475] Property Match Filtering which
   reuses IPFIX [RFC7012].  An example BPF string for matching TCP/80
   traffic to remote destination net 192.0.2.0/24 would be "dst net
   192.0.2.0/24 and tcp dst port 80".  More complex filter engines might
   be supported by the implementation that might allow for matching
   using Deep Packet Inspection (DPI) technology.

8.3.4.  Sampling Distribution

   The sampling distribution defines out of all the packets that match
   the traffic filter, which one of those are actually used for the
   measurement.  One possibility is "all" which implies that all packets
   matching the Traffic filter are considered, but there may be other
   sampling strategies.  It includes the following information:

      Value: the name of the sampling distribution

      Parameters: if any.

      Reference definition: pointer to the specification where the
      sampling distribution is properly defined.

   Sampling and Filtering Techniques for IP Packet Selection are
   documented in the PSAMP (Packet Sampling) [RFC5475], while the
   Framework for Packet Selection and Reporting, [RFC5474] provides more
   background information.  The sampling distribution parameters might
   be expressed in terms of the Information Model for Packet Sampling
   Exports, [RFC5477], and the Flow Selection Techniques, [RFC7014].






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8.3.5.  Run-time Parameters

   Run-Time Parameters are Parameters 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 (like the Fixed
   Parameters), rather these parameters are listed as an aid to the
   measurement system implementer 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.

   Examples of Run-time Parameters include IP addresses, measurement
   point designations, start times and end times for measurement, and
   other information essential to the method of measurement.

8.3.6.  Role

   In some method of measurements, there may be several roles defined
   e.g. on a one-way packet delay active measurement, there is one
   measurement agent that generates the packets and the other one that
   receives the packets.  This column contains the name of the role for
   this particular entry.  In the previous example, there should be two
   entries in the registry, one for each role, so that when a
   measurement agent is instructed to perform the one way delay source
   metric know that it is supposed to generate packets.  The values for
   this field are defined in the reference method of measurement.

8.4.  Output Category

   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.  If the complete set of measured singletons is
   output, this will be specified here.

   Some metrics embed one specific statistic in the reference metric
   definition, while others allow several output types or statistics.

8.4.1.  Type

   This column contain the name of the output type.  The output type
   defines the type of result that the metric produces.  It can be the
   raw results or it can be some form of statistic.  The specification
   of the output type must define the format of the output.  In some
   systems, format specifications will simplify both measurement
   implementation and collection/storage tasks.  Note that if two



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   different statistics are required from a single measurement (for
   example, both "Xth percentile mean" and "Raw"), then a new output
   type must be defined ("Xth percentile mean AND Raw").

8.4.2.  Reference Definition

   This column contains a pointer to the specification where the output
   type is defined

8.4.3.  Metric Units

   The measured results must be expressed using some standard dimension
   or units of measure.  This column provides the units.

   When a sample of singletons (see [RFC2330] for definitions of these
   terms) is collected, this entry will specify the units for each
   measured value.

8.5.  Administrative information

8.5.1.  Status

   The status of the specification of this Registered Performance
   Metric.  Allowed values are 'current' and 'deprecated'.  All newly
   defined Information Elements have 'current' status.

8.5.2.  Requester

   The requester for the Registered Performance Metric.  The requester
   MAY be a document, such as RFC, or person.

8.5.3.  Revision

   The revision number of a Registered Performance Metric, starting at 0
   for Registered Performance Metrics at time of definition and
   incremented by one for each revision.

8.5.4.  Revision Date

   The date of acceptance or the most recent revision for the Registered
   Performance Metric.

8.6.  Comments and Remarks

   Besides providing additional details which do not appear in other
   categories, this open Category (single column) allows for unforeseen
   issues to be addressed by simply updating this informational entry.




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9.  The Life-Cycle of Registered Metrics

   Once a Performance Metric or set of Performance Metrics has been
   identified for a given application, candidate Registry entry
   specifications in accordance with Section 8 are submitted to IANA to
   follow the process for review by the Performance Metric Experts, as
   defined below.  This process is also used for other changes to the
   Performance Metric Registry, such as deprecation or revision, as
   described later in this section.

   It is also desirable that the author(s) of a candidate Registry entry
   seek review in the relevant IETF working group, or offer the
   opportunity for review on the WG mailing list.

9.1.  Adding new Performance Metrics to the Registry

   Requests to change Registered Metrics in the Performance Metric
   Registry are submitted to IANA, which forwards the request to a
   designated group of experts (Performance Metric Experts) appointed by
   the IESG; these are the reviewers called for by the Expert Review
   RFC5226 policy defined for the Performance Metric Registry.  The
   Performance Metric Experts review the request for such things as
   compliance with this document, compliance with other applicable
   Performance Metric-related RFCs, and consistency with the currently
   defined set of Registered Performance Metrics.

   Authors are expected to review compliance with the specifications in
   this document to check their submissions before sending them to IANA.

   The Performance Metric Experts should endeavor to complete referred
   reviews in a timely manner.  If the request is acceptable, the
   Performance Metric Experts signify their approval to IANA, which
   updates the Performance Metric Registry.  If the request is not
   acceptable, the Performance Metric Experts can coordinate with the
   requester to change the request to be compliant.  The Performance
   Metric Experts may also choose in exceptional circumstances to reject
   clearly frivolous or inappropriate change requests outright.

   This process should not in any way be construed as allowing the
   Performance Metric Experts to overrule IETF consensus.  Specifically,
   any Registered Metrics that were added with IETF consensus require
   IETF consensus for revision or deprecation.

   Decisions by the Performance Metric Experts may be appealed as in
   Section 7 of RFC5226.






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9.2.  Revising Registered Performance Metrics

   A request for Revision is only permissible when the changes maintain
   backward-compatibility with implementations of the prior Registry
   entry describing a Registered Metric (entries with lower revision
   numbers, but the same Identifier and Name).

   The purpose of the Status field in the Performance Metric Registry is
   to indicate whether the entry for a Registered Metric is 'current' or
   'deprecated'.

   In addition, no policy is defined for revising IANA Performance
   Metric entries or addressing errors therein.  To be certain, changes
   and deprecations within the Performance Metric Registry are not
   encouraged, and should be avoided to the extent possible.  However,
   in recognition that change is inevitable, the provisions of this
   section address the need for revisions.

   Revisions are initiated by sending a candidate Registered Performance
   Metric definition to IANA, as in Section 8, identifying the existing
   Registry entry.

   The primary requirement in the definition of a policy for managing
   changes to existing Registered Performance Metrics is avoidance of
   interoperability problems; Performance Metric Experts must work to
   maintain interoperability above all else.  Changes to Registered
   Performance Metrics may only be done in an inter-operable way;
   necessary changes that cannot be done in a way to allow
   interoperability with unchanged implementations must result in the
   creation of a new Registered Metric and possibly the deprecation of
   the earlier metric.

   A change to a Registered Performance Metric is held to be backward-
   compatible only when:

   1.  "it involves the correction of an error that is obviously only
       editorial; or"

   2.  "it corrects an ambiguity in the Registered Performance Metric's
       definition, which itself leads to issues severe enough to prevent
       the Registered Performance Metric's usage as originally defined;
       or"

   3.  "it corrects missing information in the metric definition without
       changing its meaning (e.g., the explicit definition of 'quantity'
       semantics for numeric fields without a Data Type Semantics
       value); or"




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   4.  "it harmonizes with an external reference that was itself
       corrected."

   If an Performance Metric revision is deemed permissible by the
   Performance Metric Experts, according to the rules in this document,
   IANA makes the change in the Performance Metric Registry.  The
   requester of the change is appended to the requester in the Registry.

   Each Registered Performance Metric in the Registry has a revision
   number, starting at zero.  Each change to a Registered Performance
   Metric following this process increments the revision number by one.

   When a revised Registered Performance Metric is accepted into the
   Performance Metric Registry, the date of acceptance of the most
   recent revision is placed into the revision Date column of the
   Registry for that Registered Performance Metric.

   Where applicable, additions to Registered Performance Metrics in the
   form of text Comments or Remarks should include the date, but such
   additions may not constitute a revision according to this process.

   Older version(s) of the updated metric entries are kept in the
   registry for archival purposes.  The older entries are kept with all
   fields unmodified (version, revision date) except for the status
   field that is changed to "Deprecated".

9.3.  Deprecating Registered Performance Metrics

   Changes that are not permissible by the above criteria for Registered
   Metric's revision may only be handled by deprecation.  A Registered
   Performance Metric MAY be deprecated and replaced when:

   1.  "the Registered Performance Metric definition has an error or
       shortcoming that cannot be permissibly changed as in
       Section Revising Registered Performance Metrics; or"

   2.  "the deprecation harmonizes with an external reference that was
       itself deprecated through that reference's accepted deprecation
       method; or"

   A request for deprecation is sent to IANA, which passes it to the
   Performance Metric Expert for review.  When deprecating an
   Performance Metric, the Performance Metric description in the
   Performance Metric Registry must be updated to explain the
   deprecation, as well as to refer to any new Performance Metrics
   created to replace the deprecated Performance Metric.





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   The revision number of a Registered Performance Metric is incremented
   upon deprecation, and the revision Date updated, as with any
   revision.

   The use of deprecated Registered Metrics should result in a log entry
   or human-readable warning by the respective application.

   Names and Metric ID of deprecated Registered Metrics must not be
   reused.

   The deprecated entries are kept with all fields unmodified, except
   the version, revision date, and the status field (changed to
   "Deprecated").

10.  Security considerations

   This draft doesn't introduce any new security considerations for the
   Internet.  However, the definition of Performance Metrics may
   introduce some security concerns, and should be reviewed with
   security in mind.

11.  IANA Considerations

   This document specifies the procedure for Performance Metrics
   Registry setup.  IANA is requested to create a new Registry for
   Performance Metrics called "Registered Performance Metrics" with the
   columns defined in Section 8.

   New assignments for Performance Metric Registry will be administered
   by IANA through Expert Review [RFC5226], i.e., review by one of a
   group of experts, the Performance Metric Experts, appointed by the
   IESG upon recommendation of the Transport Area Directors.  The
   experts can be initially drawn from the Working Group Chairs and
   document editors of the Performance Metrics Directorate among other
   sources of experts.

   The Identifier values from 64512 to 65536 are reserved for private
   use.  The name starting with the prefix Priv- are reserved for
   private use.

   This document requests the allocation of the URI prefix
   urn:ietf:params:ippm:metric for the purpose of generating URIs for
   registered metrics.








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12.  Acknowledgments

   Thanks to Brian Trammell and Bill Cerveny, IPPM chairs, for leading
   some brainstorming sessions on this topic.

13.  References

13.1.  Normative References

   [RFC2026]  Bradner, S., "The Internet Standards Process -- Revision
              3", BCP 9, RFC 2026, October 1996.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2141]  Moats, R., "URN Syntax", RFC 2141, May 1997.

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

   [RFC3986]  Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform
              Resource Identifier (URI): Generic Syntax", STD 66, RFC
              3986, January 2005.

   [RFC4148]  Stephan, E., "IP Performance Metrics (IPPM) Metrics
              Registry", BCP 108, RFC 4148, August 2005.

   [RFC5226]  Narten, T. and H. Alvestrand, "Guidelines for Writing an
              IANA Considerations Section in RFCs", BCP 26, RFC 5226,
              May 2008.

   [RFC6248]  Morton, A., "RFC 4148 and the IP Performance Metrics
              (IPPM) Registry of Metrics Are Obsolete", RFC 6248, April
              2011.

   [RFC6390]  Clark, A. and B. Claise, "Guidelines for Considering New
              Performance Metric Development", BCP 170, RFC 6390,
              October 2011.

   [RFC6576]  Geib, R., Morton, A., Fardid, R., and A. Steinmitz, "IP
              Performance Metrics (IPPM) Standard Advancement Testing",
              BCP 176, RFC 6576, March 2012.








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13.2.  Informative References

   [RFC2679]  Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
              Delay Metric for IPPM", RFC 2679, 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.

   [RFC3550]  Schulzrinne, H., Casner, S., Frederick, R., and V.
              Jacobson, "RTP: A Transport Protocol for Real-Time
              Applications", STD 64, RFC 3550, July 2003.

   [RFC3611]  Friedman, T., Caceres, R., and A. Clark, "RTP Control
              Protocol Extended Reports (RTCP XR)", RFC 3611, November
              2003.

   [RFC4566]  Handley, M., Jacobson, V., and C. Perkins, "SDP: Session
              Description Protocol", RFC 4566, July 2006.

   [RFC5474]  Duffield, N., Chiou, D., Claise, B., Greenberg, A.,
              Grossglauser, M., and J. Rexford, "A Framework for Packet
              Selection and Reporting", RFC 5474, March 2009.

   [RFC5475]  Zseby, T., Molina, M., Duffield, N., Niccolini, S., and F.
              Raspall, "Sampling and Filtering Techniques for IP Packet
              Selection", RFC 5475, March 2009.

   [RFC5477]  Dietz, T., Claise, B., Aitken, P., Dressler, F., and G.
              Carle, "Information Model for Packet Sampling Exports",
              RFC 5477, March 2009.

   [RFC5481]  Morton, A. and B. Claise, "Packet Delay Variation
              Applicability Statement", RFC 5481, March 2009.

   [RFC5905]  Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
              Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, June 2010.






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   [RFC6035]  Pendleton, A., Clark, A., Johnston, A., and H. Sinnreich,
              "Session Initiation Protocol Event Package for Voice
              Quality Reporting", RFC 6035, November 2010.

   [RFC6776]  Clark, A. and Q. Wu, "Measurement Identity and Information
              Reporting Using a Source Description (SDES) Item and an
              RTCP Extended Report (XR) Block", RFC 6776, October 2012.

   [RFC6792]  Wu, Q., Hunt, G., and P. Arden, "Guidelines for Use of the
              RTP Monitoring Framework", RFC 6792, November 2012.

   [RFC7003]  Clark, A., Huang, R., and Q. Wu, "RTP Control Protocol
              (RTCP) Extended Report (XR) Block for Burst/Gap Discard
              Metric Reporting", RFC 7003, September 2013.

   [RFC7012]  Claise, B. and B. Trammell, "Information Model for IP Flow
              Information Export (IPFIX)", RFC 7012, September 2013.

   [RFC7014]  D'Antonio, S., Zseby, T., Henke, C., and L. Peluso, "Flow
              Selection Techniques", RFC 7014, September 2013.

   [I-D.ietf-lmap-framework]
              Eardley, P., Morton, A., Bagnulo, M., Burbridge, T.,
              Aitken, P., and A. Akhter, "A framework for Large-Scale
              Measurement of Broadband Performance (LMAP)", draft-ietf-
              lmap-framework-14 (work in progress), April 2015.

Authors' Addresses

   Marcelo Bagnulo
   Universidad Carlos III de Madrid
   Av. Universidad 30
   Leganes, Madrid  28911
   SPAIN

   Phone: 34 91 6249500
   Email: marcelo@it.uc3m.es
   URI:   http://www.it.uc3m.es


   Benoit Claise
   Cisco Systems, Inc.
   De Kleetlaan 6a b1
   1831 Diegem
   Belgium

   Email: bclaise@cisco.com




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   Philip Eardley
   BT
   Adastral Park, Martlesham Heath
   Ipswich
   ENGLAND

   Email: philip.eardley@bt.com


   Al Morton
   AT&T Labs
   200 Laurel Avenue South
   Middletown, NJ
   USA

   Email: acmorton@att.com


   Aamer Akhter
   Consultant
   118 Timber Hitch
   Cary, NC
   USA

   Email: aakhter@gmail.com


























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