Network Working Group M. Bagnulo Internet-Draft UC3M Intended status: Best Current Practice B. Claise Expires: January 4, 2015 Cisco Systems, Inc. P. Eardley BT A. Morton AT&T Labs July 3, 2014 Registry for Performance Metrics draft-ietf-ippm-metric-registry-00 Abstract This document specifies the common aspects of the IANA Registry for Performance Metrics, both active and passive categories. 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 4, 2015. Copyright Notice Copyright (c) 2014 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 carefully, as they describe your rights and restrictions with respect Bagnulo, et al. Expires January 4, 2015 [Page 1] Internet-Draft Registry for Performance Metrics July 2014 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 . . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5 4. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Design Considerations for the Registry and Registered Metrics 7 5.1. Interoperability . . . . . . . . . . . . . . . . . . . . 8 5.2. Criteria for Registered Performance Metrics . . . . . . . 8 5.3. Single point of reference for Performance metrics . . . . 9 5.4. Side benefits . . . . . . . . . . . . . . . . . . . . . . 9 6. Performance Metric Registry: Prior attempt . . . . . . . . . 9 6.1. Why this Attempt Will Succeed? . . . . . . . . . . . . . 10 7. Common Columns of the Performance Metric Registry . . . . . . 11 7.1. Identifier . . . . . . . . . . . . . . . . . . . . . . . 11 7.2. Name . . . . . . . . . . . . . . . . . . . . . . . . . . 11 7.3. URI . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 7.4. Status . . . . . . . . . . . . . . . . . . . . . . . . . 12 7.5. Requester . . . . . . . . . . . . . . . . . . . . . . . . 13 7.6. Revision . . . . . . . . . . . . . . . . . . . . . . . . 13 7.7. Revision Date . . . . . . . . . . . . . . . . . . . . . . 13 7.8. Description . . . . . . . . . . . . . . . . . . . . . . . 13 7.9. Reference Specification(s) . . . . . . . . . . . . . . . 13 8. The Life-Cycle of Registered Metrics . . . . . . . . . . . . 13 8.1. The Process for Review by the Performance Metric Experts 13 8.2. Revising Registered Performance Metrics . . . . . . . . . 14 8.3. Deprecating Registered Performance Metrics . . . . . . . 16 9. Performance Metric Registry and other Registries . . . . . . 16 10. Security considerations . . . . . . . . . . . . . . . . . . . 17 11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 13.1. Normative References . . . . . . . . . . . . . . . . . . 17 13.2. Informative References . . . . . . . . . . . . . . . . . 18 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19 1. Open Issues 1. Many aspects of the Naming convention are TBD, and need discussion. For example, we have distinguished RTCP-XR metrics as End-Point (neither active nor passive in the traditional sense, so not Act_ or Pas_). Even though we may not cast all Bagnulo, et al. Expires January 4, 2015 [Page 2] Internet-Draft Registry for Performance Metrics July 2014 naming conventions in stone at the start, it will be helpful to look at several examples of passive metric names now. 2. We should expand on the different roles and responsibilities of the Performance Metrics Experts versus the Performance Metric Directorate. At least, the Performance Metric Directorate one should be expanded. --- (v7) If these are different entities, our only concern is the role of the "PM Experts". 3. RTCP-XR metrics are currently referred to as "end-point", and have aspects that are similar to active (the measured stream characteristics are known a priori and measurement commonly takes place at the end-points of the path) and passive (there is no additional traffic dedicated to measurement, with the exception of the RTCP report packets themselves). We have one example expressing an end-point metric in the active sub- registry memo. 4. Revised Registry Entries: Keep for history (deprecated) or Delete? 5. Need to include an example for a name for a passive metric 6. Definition of Parameter needs more work? 7. Whether the name of the metric should contain the version of the metric 8. Suppression Flag for the metrics, does it belong to the registry? If yes, is ti part of the core or the active one? 9. Endpoint metric: I think we need either to remove it from the draft or to properly define it. Currently in the draft we have it as a equal to passive and active but it is not defined, which seems incoherent. 10. 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 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. Bagnulo, et al. Expires January 4, 2015 [Page 3] Internet-Draft Registry for Performance Metrics July 2014 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) WG Information elements related to Performance Metrics are currently proposed. 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. 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 proposes the creation of a Performance Metrics Registry. It also provides best practices on how to define new or updated entries in the Performance Metrics Registry. Bagnulo, et al. Expires January 4, 2015 [Page 4] Internet-Draft Registry for Performance Metrics July 2014 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]. The terms Performance Metric and Performance Metrics Directorate are defined in [RFC6390], and copied over in this document for the readers convenience. Performance Metric: A Performance Metric is a quantitative measure of performance, specific to an IETF-specified protocol or specific 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. Registered Performance Metric: A Registered Performance Metric (or Registered Metric) is a Performance Metric expressed as an entry in the Performance Metric Registry, and comprised of a specifically named metric which has met all the registry review criteria, is under the curation of IETF Performance Metrics Experts, and whose changes are controlled by IANA. 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 experts selected by the IESG to validate the Performance Metrics before updating the Performance Metrics Registry. The Performance Metrics Experts work closely with IANA. Performance Metrics Directorate: The Performance Metrics Directorate is a directorate that provides guidance for Performance Metrics development in the IETF. The Performance Metrics Directorate should be composed of experts in the performance community, potentially selected from the IP Performance Metrics (IPPM), Benchmarking Methodology (BMWG), and Performance Metrics for Other Layers (PMOL) WGs. Parameter: An input factor defined as a variable in the definition of a metric. A numerical or other specified factor forming one of a set that defines a metric or sets the conditions of its Bagnulo, et al. Expires January 4, 2015 [Page 5] Internet-Draft Registry for Performance Metrics July 2014 operation. All Input Parameters must be known to measure using a metric and interpret the results. Although Input Parameters do not change the fundamental nature of the metric's definition, some have substantial influence on the network property being assessed and interpretation of the results. Consider the case of packet loss in the following two 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. An Internet user's host can generate active measurement traffic (virtually all typical user-generated traffic is not dedicated to active measurement, but it can produce such traffic with the necessary application operating). 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. Hybrid Measurement Method: Methods of Measurement which use a combination of Active Measurement and Passive Measurement methods. 4. Scope The intended audience of this document includes those who prepare and submit a request for a Registered Performance Metric, and for the Performance Metric Experts who review a request. This document specifies a Performance Metrics Registry in IANA. This Performance Metric Registry is applicable to Performance Metrics issued from Active Measurement, Passive Measurement, or from end- point calculation. This registry is designed to encompass performance metrics developed throughout the IETF and especially for Bagnulo, et al. Expires January 4, 2015 [Page 6] Internet-Draft Registry for Performance Metrics July 2014 the following existing 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 serves as the foundation for further work. It specifies the set of columns describing common aspects necessary for all entries in the Performance Metrics Registry. Two documents describing sub-registries will be developed separately: one for Active Registered Metrics and another one for the Passive Registered Metrics. Indeed, Active and Passive Performance Metrics appear to have different characteristics that must be documented in their respective sub-registies. For example, Active Performance Methods must specify the packet stream characteristics they generate and measure, so it is essential to include the stream specifications in the Registry entry. In the case of Passive Performance Metrics, there is a need to specify the sampling distribution in the Registry. While it would be possible to force the definition of the Registry field to include both types of distributions in the same Registry column, we believe it is cleaner and clearer to have separated sub- registries with different columns that have a narrow definition. It is possible that future Performance Metrics use Hybrid Measurement methods, and it may be possible to register hybrid metrics in one of the two planned sub-registries (active or passive), or it may be efficient to define a third sub-registry with unique columns. The current design with sub-registries allows for growth, and this is a recognized option for extension. This document makes no attempt to populate the Registry with initial entries. Based on [RFC5226] Section 4.3, this document is processed as Best Current Practice (BCP) [RFC2026]. 5. Design Considerations for the Registry and Registered Metrics In this section, we detail several design considerations that are relevant for understanding the motivations and expected use of the Performance Metric Registry. Bagnulo, et al. Expires January 4, 2015 [Page 7] Internet-Draft Registry for Performance Metrics July 2014 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 this particular case of the Performance Metric Registry, there are two types of protocols that will use the values defined in the Registry for their operation: 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 requirements 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 transferred. Using the LMAP terminology, the Registry is used in the Report protocol to allow a Measurement Agent to report measurement results to a Collector. 5.2. Criteria for Registered Performance Metrics It is neither possible nor desirable to populate the Registry with all combinations of input parameters of all Performance Metrics. The Registered Performance Metrics should be: 1. interpretable by the user. 2. implementable by the software designer, 3. deployable by network operators, without major impact on the networks, 4. accurate, for interoperability and deployment across vendors, 5. Operational useful, so that it has significant industry interest and/or has seen deployment, Bagnulo, et al. Expires January 4, 2015 [Page 8] Internet-Draft Registry for Performance Metrics July 2014 6. Sufficiently tightly defined, so that changing 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 Registry entry has significant industry interest, or has seen deployment, and there is agreement that the candidate Registered Metric serves its intended purpose. 5.3. Single point of reference for Performance metrics A Registry for Performance metrics 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 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 metrics, where different entities that request measurements, execute measurements, and report the results can benefit from a common understanding of the referenced metric. 5.4. 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 metrics, that are normally supported by different implementations of measurement agents. Second, the results of the metrics would be comparable even if they are performed by different implementations and in different networks, as the 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 Registry entries are sufficiently well specified to result in comparable (or equivalent) results. Registry entries which have undergone such testing SHOULD be noted, with a reference to the test results. 6. 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 Bagnulo, et al. Expires January 4, 2015 [Page 9] Internet-Draft Registry for Performance Metrics July 2014 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 entry in the registry with only a few variable Parameters to be specified by the measurement designer, if any. The idea is that entries in the Registry represent different measurement methods which require input 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. We believe 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 with questionable usefulness. Therefore this document defines that the Registry only includes metrics that are well defined and that have proven to be operationally useful. In order to guarantee these two characteristics we require that a set of experts review the allocation request to verify that the metric is well defined and it is operationally useful. 6.1. Why this Attempt Will Succeed? The Registry defined in this document addresses the main issues identified in the previous attempt. As we mention 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. In this Registry, the Registry requests are evaluated by an expert group, the Performance Metrics Experts, who will make sure that the metric is properly defined. This document provides guidelines to assess if a metric is properly defined. 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: Bagnulo, et al. Expires January 4, 2015 [Page 10] Internet-Draft Registry for Performance Metrics July 2014 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 clearly not the case for the previous attempt: defining a metric with an undefined P-Type makes its implementation unpractical. 7. Common Columns of the Performance Metric Registry The Performance Metric Registry is composed of two sub-registries: the registry for Active Performance Metrics and the registry for Passive Performance Metrics. The rationale for having two sub- registries (as opposed to having a single registry for all metrics) is because the set of registry columns must support unambiguous registry entries, and there are fundamental differences in the methods to collect active and passive metrics and the required input parameters. Forcing them into a single, generalized registry would result in a less meaningful structure for some entries in the registry. Nevertheless, it is desirable that the two sub-registries share the same structure as much as possible. In particular, both registries will share the following columns: the identifier and the name, the requester, the revision, the revision date and the description. All these fields are described below. The design of these two sub-registries is work-in-progress. 7.1. Identifier A numeric identifier for the Registered Performance Metric. This identifier MUST be unique within the Performance Metric Registry and sub-registries. 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 active monitoring Registered Performance Metric, and the highest available identifier to the next passive monitoring Registered Performance Metric. 7.2. 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 Bagnulo, et al. Expires January 4, 2015 [Page 11] Internet-Draft Registry for Performance Metrics July 2014 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 (including sub-registries)." 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 composing the Registered Performance Metric name." 5. "MUST start with prefix Act_ for active measurement Registered Performance Metric." 6. "MUST start with prefix Pass_ for passive monitoring Registered Performance Metric." AL COMMENTS: how about just 3 letters for consistency: "Pas_" 7. The remaining rules for naming are left to the Performance 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. >>>> NEED passive naming examples. 7.3. URI The URI column MUST contain a URI [RFC 3986] that uniquely identified the metric. The 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. 7.4. 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. Bagnulo, et al. Expires January 4, 2015 [Page 12] Internet-Draft Registry for Performance Metrics July 2014 7.5. Requester The requester for the Registered Performance Metric. The requester MAY be a document, such as RFC, or person. 7.6. 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. 7.7. Revision Date The date of acceptance or the most recent revision for the Registered Performance Metric. 7.8. Description A Registered Performance Metric Description is a written representation of a particular Registry entry. It supplements the metric name to help Registry users select relevant Registered Performance Metrics. 7.9. Reference Specification(s) Registry entries that follow the common columns must provide the reference specification(s) on which the Registered Performance Metric is based. 8. 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 X 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. 8.1. The Process for Review by the Performance Metric Experts Requests to change Registered Metrics in the Performance Metric Registry or a linked sub-registry are submitted to IANA, which forwards the request to a designated group of experts (Performance Bagnulo, et al. Expires January 4, 2015 [Page 13] Internet-Draft Registry for Performance Metrics July 2014 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 changes 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. 8.2. 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 X, identifying the existing Registry entry. Bagnulo, et al. Expires January 4, 2015 [Page 14] Internet-Draft Registry for Performance Metrics July 2014 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" 4. "it harmonizes with an external reference that was itself corrected." 5. "BENOIT: NOTE THAT THERE ARE MORE RULES IN RFC 7013 SECTION 5 BUT THEY WOULD ONLY APPLY TO THE ACTIVE/PASSIVE DRAFTS. TO BE DISCUSSED." If a change is deemed permissible by the Performance Metric Experts, 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. COMMENT: Al (and Phil) think we should keep old/revised entries as- is, marked as deprecated >>>> Since any revision must be inter- operable according to the criteria above, there is no need for the Performance Metric Registry to store information about old revisions. When a revised Registered Performance Metric is accepted into the Performance Metric Registry, the date of acceptance of the most Bagnulo, et al. Expires January 4, 2015 [Page 15] Internet-Draft Registry for Performance Metrics July 2014 recent revision is placed into the revision Date column of the Registry for that Registered Performance Metric. Where applicable, additions to Registry entries in the form of text Comments or Remarks should include the date, but such additions may not constitute a revision according to this process. 8.3. 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, as in Section 'The Process for Review by the Performance Metric Experts'. 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 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. 9. Performance Metric Registry and other Registries BENOIT: TBD. THE BASIC IDEA IS THAT PEOPLE COULD DIRECTLY DEFINE PERF. METRICS IN OTHER EXISTING REGISTRIES, FOR SPECIFIC PROTOCOL/ENCODING. EXAMPLE: IPFIX. IDEALLY, ALL PERF. METRICS SHOULD BE DEFINED IN THIS REGISTRY AND REFERS TO FROM OTHER REGISTRIES. Bagnulo, et al. Expires January 4, 2015 [Page 16] Internet-Draft Registry for Performance Metrics July 2014 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". This Performance Metrics Registry contains two sub registries once for active and another one for Passive Performance Metrics. These sub registries are not defined in this document. However, these two sub registries MUST contain the common columns defined in Section 7. 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 will initially be drawn from the Working Group Chairs and document editors of the Performance Metrics Directorate [performance- metrics-directorate]. This document requests the allocation of the URI prefix urn:ietf:params:ippm:metric for the purpose of generating URIs for registered metrics. 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 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2026] Bradner, S., "The Internet Standards Process -- Revision 3", BCP 9, RFC 2026, October 1996. [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, "Framework for IP Performance Metrics", RFC 2330, May 1998. Bagnulo, et al. Expires January 4, 2015 [Page 17] Internet-Draft Registry for Performance Metrics July 2014 [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. [RFC3986] Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform Resource Identifier (URI): Generic Syntax", STD 66, RFC 3986, January 2005. [RFC2141] Moats, R., "URN Syntax", RFC 2141, May 1997. 13.2. Informative References [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control Protocol Extended Reports (RTCP XR)", RFC 3611, November 2003. [RFC3550] Schulzrinne, H., Casner, S., Frederick, R., and V. Jacobson, "RTP: A Transport Protocol for Real-Time Applications", STD 64, RFC 3550, July 2003. [RFC6035] Pendleton, A., Clark, A., Johnston, A., and H. Sinnreich, "Session Initiation Protocol Event Package for Voice Quality Reporting", RFC 6035, November 2010. [I-D.ietf-lmap-framework] Eardley, P., Morton, A., Bagnulo, M., Burbridge, T., Aitken, P., and A. Akhter, "A framework for large-scale measurement platforms (LMAP)", draft-ietf-lmap- framework-07 (work in progress), June 2014. Bagnulo, et al. Expires January 4, 2015 [Page 18] Internet-Draft Registry for Performance Metrics July 2014 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 Philip Eardley British Telecom 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 Bagnulo, et al. Expires January 4, 2015 [Page 19]