Registry for Performance
MetricsUniversidad Carlos III de
MadridAv. Universidad 30LeganesMadrid28911SPAIN34 91 6249500marcelo@it.uc3m.eshttp://www.it.uc3m.esCisco Systems,
Inc.De Kleetlaan 6a b11831 DiegemBelgiumbclaise@cisco.comBTAdastral Park, Martlesham HeathIpswichENGLANDphilip.eardley@bt.comAT&T Labs200 Laurel Avenue SouthMiddletown, NJUSAacmorton@att.comConsultant118 Timber HitchCaryNCUSAaakhter@gmail.comThis document defines the IANA Registry for
Performance Metrics. This document
also gives a set of guidelines for Registered Performance Metric
requesters and reviewers.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 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)" , 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", .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 .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 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.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 . 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
and broader than the definition of performance metric in .A Registered Performance 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.The IANA
registry containing Registered Performance Metrics.A set of metrics that are
registered in a proprietary registry, as opposed to Performance Metrics Registry.The Performance Metrics
Experts is a group of designated experts selected by
the IESG to validate the Performance Metrics before updating the Performance
Metrics Registry. The Performance Metrics Experts work closely with IANA.
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.
There are two types of Parameters, Fixed and Run-time parameters. For the Fixed Parameters,
the value of the variable is specified in the Performance Metrics Registry entry and different Fixed Parameter values results in
different Registered Performance Metrics. For the Run-time Parameters, the value of the variable is defined when the metric
measurement method is executed and a given Registered Performance Metric supports multiple values for the parameter.
Although Run-time Parameters do not change the
fundamental nature of the Performance Metric's 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 Run-time 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 Run-time 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 Run-time Parameters (at least), to the extreme where
we are actually using loss to infer its compliment: delivered throughput.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. A detailed definition of Active Measurement Method is provided in
. Examples of Active Measurement Methods are
the measurement methods for the One way delay metric defined in
and the one for round trip delay defined in .Methods of Measurement conducted on
network traffic, generated either from the end users or from network elements that
would exist regardless whether the measurement was being conducted or not.
One characteristic of Passive Measurement Methods is that sensitive information
may be observed, and as a consequence, stored in the measurement system.
A detailed definition of Passive Measurement Method is provided in
.
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 Performance Metrics are
useful for a measurement study, instructions for
writing the text for each column of the Registered Performance Metrics, and
information on the supporting documentation required for the new
Performance Metrics 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 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 .
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 Performance Metrics 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 Section 4.3, this document is
processed as Best Current Practice (BCP) .In this section, we detail several motivations for the
Performance Metric Registry.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 Performance Metrics Registry
during their operation (by referring to the Index values):
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 Performance Metrics Registry. One particular example is
the LMAP framework . Using
the LMAP terminology, the Performance Metrics 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. 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 Performance Metrics Registry is used in
the Report protocol to allow a Measurement Agent to report
measurement results to a Collector.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.
There are a couple of side benefits of having such a registry.
First, the Performance Metrics 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
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.It is neither possible nor desirable to populate the Performance Metrics Registry with
all combinations of Parameters of all Performance Metrics. The
Registered Performance Metrics should be: interpretable by the user.implementable by the software designer,deployable by network operators,accurate, for interoperability and deployment across
vendors,Operationally useful, so that it has significant industry interest
and/or has seen deployment, 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.There was a previous attempt to define a metric registry RFC 4148. However, it was obsoleted by RFC 6248 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. "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.""The registry structure has been found to be insufficiently
detailed to uniquely identify IPPM metrics.""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 Performance Metrics 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 Performance Metrics Registry. There is 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.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 Performance Metrics Registry:
the LMAP framework and protocol. Because the LMAP protocol will use
the Performance Metrics 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) allows implementation to be ambiguous.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 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 Performance Metric.Each column serves as a check-list item and helps to avoid omissions
during registration and expert review.
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
lowest available identifier to the next Registered
Performance Metric.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:
"MUST be chosen carefully to describe the Registered
Performance Metric and the context in which it will be used.""MUST be unique within the Performance Metric Registry.""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'."MUST use '_' between each component of the Registered
Performance Metric name.MUST start with prefix Act_ for active measurement Registered
Performance Metric.MUST start with prefix Pas_ for passive monitoring Registered
Performance Metric.Other types of Performance Metric should define a proper prefix for
identifying the type.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 RFCAn example is "Act_UDP_Latency_Poisson_mean" for a active
monitoring UDP latency metric using a Poisson stream of packets and
producing the mean as output.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)The URIs column MUST contain a URI [RFC 3986] that uniquely
identifies the metric. This URI is a URN [RFC 2141]. The URI is
automatically generated by prepending the prefix
urn:ietf:params:ippm:metric: to the metric name. The resulting URI
is globally unique. The URIs column MUST contain a second URI which is a URL [RFC
3986] and uniquely identifies and locates the metric entry so it is
accessible through the Internet. The exact composition of each
metric URL will be determined by IANA, but there will be some
overlap with the URN described above.A Registered Performance Metric description is a written
representation of a particular Performance Metrics Registry entry. It supplements the
Registered Performance Metric name to help Performance Metrics Registry users select
relevant Registered Performance Metrics.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.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.
Fixed Parameters are Paremeters whose value must be specified
in the Performance Metrics 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 , 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 .
Varying MIN_SEQUENTIAL values can alter the loss report and this
value could be set as a Fixed ParameterA Parameter which is a Fixed Parameter for one Performance Metrics Registry entry may be
designated as a Run-time Parameter for another Performance Metrics Registry entry.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.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.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:
Value: The name of the packet stream scheduling
disciplineStream 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.Reference: the specification where the stream is definedThe simplest example of stream specification is Singleton
scheduling (see ), 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 distributed as described in and
Periodic as described in . Both Poisson and
Periodic have their own unique parameters, and the relevant set of
values is specified in this column.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 Property Match Filtering which reuses IPFIX
. 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.
The traffic filter includes the following information:
Type: the type of traffic filter used, e.g. BPF, PSAMP, OpenFlow rule, etc. as defined by a normative referenceValue: the actual set of rules expressed 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 distributionParameters: 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)
, while the Framework for Packet Selection and Reporting,
provides more background information. The sampling distribution parameters might be expressed in terms of the
Information Model for Packet Sampling Exports, , and the Flow Selection Techniques,
.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 Performance Metrics 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.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.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.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 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").This column contains a pointer to the specification where the output type is
definedThe measured results must be expressed using some standard
dimension or units of measure. This column provides the units.When a sample of singletons (see for
definitions of these terms) is collected, this entry will specify
the units for each measured value.The status of the specification of this Registered Performance
Metric. Allowed values are 'current' and 'deprecated'. All newly
defined Information Elements have 'current' status.The requester for the Registered Performance Metric. The requester
MAY be a document, such as RFC, or person.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.The date of acceptance or the most recent revision for the
Registered Performance Metric.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.Once a Performance Metric or set of Performance Metrics has been
identified for a given application, candidate Performance Metrics Registry entry
specifications in accordance with 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 Performance Metrics Registry entry
seek review in the relevant IETF working group, or offer the opportunity
for review on the WG mailing list.Requests to change Registered Performance 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 Performance 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.A request for Revision is only permissible when the changes
maintain backward-compatibility with implementations of the prior
Performance Metrics Registry entry describing a Registered Performance 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 Performance 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 Performance Metrics 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 Performance Metric and possibly the deprecation of the earlier metric.A change to a Registered Performance Metric is held to be
backward-compatible only when: "it involves the correction of an error that is obviously only
editorial; or""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""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""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
Performance Metrics Registry.Each Registered Performance Metric in the Performance Metrics 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".Changes that are not permissible by the above criteria for
Registered Performance Metric's revision may only be handled by deprecation. A
Registered Performance Metric MAY be deprecated and replaced when:
"the Registered Performance Metric definition has an error or
shortcoming that cannot be permissibly changed as in Section
Revising Registered Performance Metrics; or""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.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 Performance Metrics should result in a log
entry or human-readable warning by the respective application.Names and Metric ID of deprecated Registered Performance 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").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.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 .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 Performance Metrics.Thanks to Brian Trammell and Bill Cerveny, IPPM chairs, for leading
some brainstorming sessions on this topic.