Network Working Group A. Morton Internet-Draft AT&T Labs Intended status: Standards Track August 26, 2013 Expires: February 27, 2014 A Registry Investigation for IPPM Packet Delay Variation Metrics draft-morton-ippm-registry-pdv-00 Abstract This memo investigates a scheme to organize registry entries, primarily those defined in RFCs prepared in the IP Performance Metrics (IPPM) Working Group of the IETF. Three aspects make IPPM metric registration difficult: (1) Use of the Type-P notion to allow users to specify their own packet types. (2) Use of Flexible input variables, called Parameters in IPPM definitions, some which determine the quantity measured and others which should not be specified until execution of the measurement. (3) Allowing flexibility in choice of statistics to summarize the results on a stream of measurement packets. Specifically, this memo investigates registry entries that would follow from RFC 3393, the specification IP Packet Delay Variation that allows for many different forms of unique metrics, as a difficult and important test of the registry structure. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. 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." Morton Expires February 27, 2014 [Page 1] Internet-Draft Round-trip Loss August 2013 This Internet-Draft will expire on February 27, 2014. Copyright Notice Copyright (c) 2013 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 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. Morton Expires February 27, 2014 [Page 2] Internet-Draft Round-trip Loss August 2013 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. List of Registry Columns . . . . . . . . . . . . . . . . . . . 5 3.1. Element ID . . . . . . . . . . . . . . . . . . . . . . . . 5 3.2. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 5 3.3. Run-time Parameters . . . . . . . . . . . . . . . . . . . 6 3.4. Fixed Parameters . . . . . . . . . . . . . . . . . . . . . 6 3.5. Metric Definition . . . . . . . . . . . . . . . . . . . . 6 3.6. Metric Units (and Data Format?) . . . . . . . . . . . . . 6 3.7. Stream Type and Stream Parameters . . . . . . . . . . . . 6 3.8. Method of Measurement . . . . . . . . . . . . . . . . . . 7 3.9. Output Statistic . . . . . . . . . . . . . . . . . . . . . 7 3.10. Discussion/Remarks . . . . . . . . . . . . . . . . . . . . 7 4. Registry Column Entries for PDV . . . . . . . . . . . . . . . 7 4.1. Element ID . . . . . . . . . . . . . . . . . . . . . . . . 7 4.2. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 7 4.3. Run-time Parameters . . . . . . . . . . . . . . . . . . . 7 4.4. Fixed Parameters . . . . . . . . . . . . . . . . . . . . . 8 4.5. Metric Definition . . . . . . . . . . . . . . . . . . . . 8 4.6. Metric Units (and Data Format?) . . . . . . . . . . . . . 8 4.7. Stream Type and Stream Parameters . . . . . . . . . . . . 9 4.8. Method of Measurement . . . . . . . . . . . . . . . . . . 9 4.9. Output Statistic . . . . . . . . . . . . . . . . . . . . . 9 4.10. Discussion/Remarks . . . . . . . . . . . . . . . . . . . . 9 5. Registry Column Entries for IPDV . . . . . . . . . . . . . . . 10 5.1. Element ID . . . . . . . . . . . . . . . . . . . . . . . . 10 5.2. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 10 5.3. Run-time Parameters . . . . . . . . . . . . . . . . . . . 10 5.4. Fixed Parameters . . . . . . . . . . . . . . . . . . . . . 11 5.5. Metric Definition . . . . . . . . . . . . . . . . . . . . 11 5.6. Metric Units (and Data Format?) . . . . . . . . . . . . . 11 5.7. Stream Type and Stream Parameters . . . . . . . . . . . . 11 5.8. Method of Measurement . . . . . . . . . . . . . . . . . . 12 5.9. Output Statistic . . . . . . . . . . . . . . . . . . . . . 12 5.10. Discussion/Remarks . . . . . . . . . . . . . . . . . . . . 12 6. Security Considerations . . . . . . . . . . . . . . . . . . . 12 6.1. Denial of Service Attacks . . . . . . . . . . . . . . . . 12 6.2. User Data Confidentiality . . . . . . . . . . . . . . . . 13 6.3. Interference with the metrics . . . . . . . . . . . . . . 13 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 9.1. Normative References . . . . . . . . . . . . . . . . . . . 14 9.2. Informative References . . . . . . . . . . . . . . . . . . 14 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 15 Morton Expires February 27, 2014 [Page 3] Internet-Draft Round-trip Loss August 2013 1. Introduction This memo investigates a scheme to organize registry entries, primarily those defined in RFCs prepared in the IP Performance Metrics (IPPM) Working Group of the IETF, according to their framework [RFC2330]. Three aspects make IPPM metric registration difficult: (1) Use of the Type-P notion to allow users to specify their own packet types. (2) Use of Flexible input variables, called Parameters in IPPM definitions, some which determine the quantity measured and others which should not be specified until execution of the measurement. (3) Allowing flexibility in choice of statistics to summarize the results on a stream of measurement packets. Specifically, this memo investigates registry entries that would follow from [RFC3393], the specification IP Packet Delay Variation that allows for many different forms of unique metrics, as a difficult and important test of the registry structure. Although there are several standard templates for organizing specifications of performance metrics (see [RFC2679] for an example of the traditional IPPM template, based to large extent on the Benchmarking Methodology Working Group's traditional template in [RFC1242], and [RFC6390] for a similar template), none of these templates were intended to become the basis for the columns of an IETF-wide registry of metrics. As we examine the aspects of metric specifications which need to appear in the registry, we will see that none of the existing metric templates fully satisfies the needs of a registry. The authors of [draft-bagnulo-ippm-new-registry] and [draft-bagnulo-ippm-new-registry-independent] made important contributions to this memo in the registry column structure, and the problem of registry development in general. We also acknowledge input from the authors of [draft-claise-ippm-perf-metric-registry], especially the value of an Element ID and the need for naming conventions. 2. Scope This memo investigates the registry structure that best describes IPPM delay variation metrics based on [RFC3393] using the conventions of the IPPM framework [RFC2330]. We find that the flexibility allowed in [RFC3393] requires further specificity to have a metric worthy of registration, and we refer to [RFC5481] for the needed definition details. In this memo, we attempt a combinatoric registry, where all factors Morton Expires February 27, 2014 [Page 4] Internet-Draft Round-trip Loss August 2013 that can be reasonably specified ARE specified, and changing even one factor would require a new registry entry (row). It is believed that this exercise can also be instructive for a registry based on independent factors, [draft-bagnulo-ippm-new-registry-independent] but that topic is beyond the scope of this effort. 3. List of Registry Columns This section briefly describes the columns used by this draft, as this is likely to be a topic for discussion and revision. Taken as a whole, the entries in the columns give a registered instance of a metric with sufficient specificity to promote comparable results across independent implementations. In other words, a complete Metric Description. 3.1. Element ID An integer having enough digits to uniquely identify each entry in the Registry. 3.2. Metric Name A metric naming convention is TBD. The current guidance from Section 13 of [RFC2330], where Type-P is a feature of all IPPM metric names, is: "... we introduce the generic notion of a "packet of type P", where in some contexts P will be explicitly defined (i.e., exactly what type of packet we mean), partially defined (e.g., "with a payload of B octets"), or left generic. Thus we may talk about generic IP-type- P-connectivity or more specific IP-port-HTTP-connectivity. Some metrics and methodologies may be fruitfully defined using generic type P definitions which are then made specific when performing actual measurements. Whenever a metric's value depends on the type of the packets involved in the metric, the metric's name will include either a specific type or a phrase such as "type-P". ..." Registry entries are a context where Type-P must be defined. IPPM Metric names have also included the typically included the stream type, to distinguish between singleton and sample metrics (see [RFC2330] for the definition of these terms). Morton Expires February 27, 2014 [Page 5] Internet-Draft Round-trip Loss August 2013 3.3. Run-time Parameters Run-Time Parameters are input factors 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, rather these parameters are listed as an aid to the measurement system implementor 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. 3.4. Fixed Parameters Fixed Parameters are input factors that must be determined and embedded in the measurement system for use when needed. The values of these parameters is specified in the Registry. Where metrics supply a list of Parameters as part of their descriptive template, a sub-set of the Parameters will be designated as Fixed Parameters. A Parameter which is Fixed for one Registry element may be designated as a Run-time Parameter for another Registry element. 3.5. Metric Definition This entry provides references to relevant sections of the RFC(s) defining the metric, as well as any supplemental information needed to ensure an unambiguous definition for implementations. 3.6. Metric Units (and Data Format?) The results of a metric must be expressed using some standard dimension or units of measure. This column provides the units (and if possible, the data format, whose specification will simplify both measurement implementation and collection/storage tasks). When a sample of singletons is collected, this entry will include the data format and units of measure for each measured value. 3.7. Stream Type and Stream Parameters Principally, two different streams are used in IPPM metrics, Poisson distributed as described in [RFC2330] and Periodic as described in [RFC3432]. Both Poisson and Periodic have their own unique parameters, and the relevant set is specified in as Fixed Parameters Morton Expires February 27, 2014 [Page 6] Internet-Draft Round-trip Loss August 2013 in this column. 3.8. Method of Measurement 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 an unambiguous methods for implementations. 3.9. Output Statistic 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. 3.10. Discussion/Remarks Besides providing additional details which do not appear in other columns, the Discussion/Remarks column allows for unforeseen issues to be addressed by simply updating this Informational column. 4. Registry Column Entries for PDV This is a complete Metric Description for one Packet Delay Variation (PDV) metric. 4.1. Element ID An integer with enough digits to uniquely identify the entry. 4.2. Metric Name A metric naming convention is TBD. One possibility based on IPPM's framework is: IP-UDP-One-way-pdv-95th-percentile-Poisson 4.3. Run-time Parameters 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. o Src, the IP address of a host Morton Expires February 27, 2014 [Page 7] Internet-Draft Round-trip Loss August 2013 o Dst, the IP address of a host o T, a time (start of test interval) o Tf, a time (end of test interval) o T1, the wire time of the first packet in a pair, measured at MP(Src) as it leaves for Dst. o T2, the wire time of the second packet in a pair, measured at MP(Src) as it leaves for Dst. o I(i),I(i+1), i >=0, pairs of times which mark the beginning and ending of the intervals in which the packet stream from which the measurement is taken occurs. Here, I(0) = T0 and assuming that n is the largest index, I(n) = Tf. 4.4. Fixed Parameters Where metrics supply a list of Parameters as part of their descriptive template, a sub-set of the Parameters will be designated as Fixed Parameters. o F, a selection function defining unambiguously the packets from the stream selected for the metric. See section 4.2 of [RFC5481] for the PDV form. o L, a packet length in bits. L = 200 bits. o Tmax, a maximum waiting time for packets to arrive at Dst, set sufficiently long to disambiguate packets with long delays from packets that are discarded (lost). Tmax = 3 seconds. o Type-P, as defined in [RFC2330], which includes any field that may affect a packet's treatment as it traverses the network. The packets are IP/UDP, with DSCP = 0 (BE). 4.5. Metric Definition See sections 2.4 and 3.4 of [RFC3393]. Singleton delay differences measured are referred to by the variable name "ddT". 4.6. Metric Units (and Data Format?) See section 3.3 of [RFC3393] for singleton elements. [RFC2330] recommends that when a time is given, it will be expressed in UTC. Morton Expires February 27, 2014 [Page 8] Internet-Draft Round-trip Loss August 2013 The timestamp format (for T, Tf, etc.) is the same as in [RFC5905] (64 bits) and is as follows: the first 32 bits represent the unsigned integer number of seconds elapsed since 0h on 1 January 1900; the next 32 bits represent the fractional part of a second that has elapsed since then. The result format for ddT is *similar to* the short format in [RFC5905] (32 bits) and is as follows: the first 16 bits represent the *signed* integer number of seconds; the next 16 bits represent the fractional part of a second. 4.7. Stream Type and Stream Parameters Poisson distributed as described in [RFC2330], with the following Parameters. o lambda, a rate in reciprocal seconds (for Poisson Streams). lambda = 1 packet per second o Upper limit on Poisson distribution (values above this limit will be clipped and set to the limit value). Upper limit = 30 seconds. 4.8. Method of Measurement See section 2.6 and 3.6 of [RFC3393] for singleton elements. 4.9. Output Statistic See section 4.3 of [RFC3393] for details on the percentile statistic. The percentile = 95. Individual results (singletons) should be represented by the following triple o T1 and T2, times as described above o ddT as defined in section 2.4 of [RFC3393] if needed. 4.10. Discussion/Remarks Lost packets represent a challenge for delay variation metrics. See section 4.1 of [RFC3393] and the delay variation applicability statement[RFC5481] for extensive analysis and comparison of PDV and IPDV. Morton Expires February 27, 2014 [Page 9] Internet-Draft Round-trip Loss August 2013 5. Registry Column Entries for IPDV This is a complete Metric Description for one Inter-Packet Delay Variation (IPDV) metric. 5.1. Element ID An integer with enough digits to uniquely identify the entry. 5.2. Metric Name A metric naming convention is TBD. One possibility based on IPPM's framework is: IP-UDP-One-way-ipdv-range-Periodic 5.3. Run-time Parameters 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. o Src, the IP address of a host o Dst, the IP address of a host o T, the beginning of a time interval where a periodic sample is desired. o T0, a time that MUST be selected at random from the interval [T, T+PdT] to start generating packets and taking measurements (start of test interval) o Tf, a time, greater than T0, for stopping generation of packets for a sample (Tf may be relative to T0 if desired). o T1, the wire time of the first packet in a pair, measured at MP(Src) as it leaves for Dst. o T2, the wire time of the second packet in a pair, measured at MP(Src) as it leaves for Dst. o I(i),I(i+1), i >=0, pairs of times which mark the beginning and ending of the intervals in which the packet stream from which the measurement is taken occurs. Here, I(0) = T0 and assuming that n is the largest index, I(n) = Tf. Morton Expires February 27, 2014 [Page 10] Internet-Draft Round-trip Loss August 2013 5.4. Fixed Parameters Where metrics supply a list of Parameters as part of their descriptive template, a sub-set of the Parameters will be designated as Fixed Parameters. o F, a selection function defining unambiguously the packets from the stream selected for the metric. See section 4.1 of [RFC5481] for the IPDV form. o L, a packet length in bits. L = 200 bits. o Tmax, a maximum waiting time for packets to arrive at Dst, set sufficiently long to disambiguate packets with long delays from packets that are discarded (lost). Tmax = 3 seconds. o Type-P, as defined in [RFC2330], which includes any field that may affect a packet's treatment as it traverses the network. The packets are IP/UDP, with DSCP = 0 (BE). 5.5. Metric Definition See section 3.4 of [RFC3393]. 5.6. Metric Units (and Data Format?) See section 3.3 of [RFC3393] for singleton elements. [RFC2330] recommends that when a time is given, it will be expressed in UTC. The timestamp format (for T, Tf, etc.) is the same as in [RFC5905] (64 bits) and is as follows: the first 32 bits represent the unsigned integer number of seconds elapsed since 0h on 1 January 1900; the next 32 bits represent the fractional part of a second that has elapsed since then. The result format for ddT is *similar to* the short format in [RFC5905] (32 bits) and is as follows: the first 16 bits represent the *signed* integer number of seconds; the next 16 bits represent the fractional part of a second (resolving 15 microseconds). 5.7. Stream Type and Stream Parameters Periodic distributed as described in [RFC3432], with the following Parameters. Morton Expires February 27, 2014 [Page 11] Internet-Draft Round-trip Loss August 2013 o incT, the nominal duration of inter-packet interval, first bit to first bit (for Periodic Streams). incT = 1 second (per packet) o PdT, the duration of the interval for allowed sample start times. T0 may be drawn from a uniform distribution, such as T0 = T + Unif(0,PdT), or other distribution for PdT. 5.8. Method of Measurement See section 2.6 and 3.6 of [RFC3393] for singleton elements. 5.9. Output Statistic See sections 5.2 and 6.5 of [RFC5481] for details on the range statistic, or max(ddT) - min(ddT). Note that min(ddT) will almost always be a negative value. Individual results (singletons) should be represented by the following triple o T1 and T2, times as described above o ddT as defined in section 2.4 of [RFC3393] if needed. 5.10. Discussion/Remarks Lost packets represent a challenge for delay variation metrics. See section 4.1 of [RFC3393] and the delay variation applicability statement[RFC5481] for extensive analysis and comparison of PDV and IPDV. 6. Security Considerations 6.1. Denial of Service Attacks The metrics in this memo require a stream of packets sent from one host (source) to another host (destination) through intervening networks, and back. This method could be abused for denial of service attacks directed at the destination and/or the intervening network(s). Administrators of source, destination, and the intervening network(s) should establish bilateral or multi-lateral agreements regarding the timing, size, and frequency of collection of sample metrics. Use of this method in excess of the terms agreed between the participants Morton Expires February 27, 2014 [Page 12] Internet-Draft Round-trip Loss August 2013 may be cause for immediate rejection or discard of packets or other escalation procedures defined between the affected parties. 6.2. User Data Confidentiality Active use of this method generates packets for a sample, rather than taking samples based on user data, and does not threaten user data confidentiality. 6.3. Interference with the metrics It may be possible to identify that a certain packet or stream of packets is part of a sample. With that knowledge at the destination and/or the intervening networks, it is possible to change the processing of the packets (e.g. increasing or decreasing delay) in a way that may distort the measured performance. It may also be possible to generate additional packets that appear to be part of the sample metric. These additional packets are likely to perturb the results of the sample measurement. Authentication or encryption techniques, such as digital signatures, MAY be used where appropriate to guard against injected traffic attacks. [RFC5357] includes both authentication and encryption features. 7. IANA Considerations Metrics previously defined in IETF were registered in the IANA IPPM METRICS REGISTRY, however this process was discontinued when the registry structure was found to be inadequate, and the registry was declared Obsolete [RFC6248]. Although the metrics in this draft may be considered for some form of registration in the future, no IANA Action is requested at this time. 8. Acknowledgements The author thanks Brian Trammell for suggesting the term "Run-time Parameters", which led to the distinction between run-time and fixed parameters implemented in this memo. 9. References Morton Expires February 27, 2014 [Page 13] Internet-Draft Round-trip Loss August 2013 9.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, "Framework for IP Performance Metrics", RFC 2330, May 1998. [RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way Delay Metric for IPPM", RFC 2679, September 1999. [RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way Packet Loss Metric for IPPM", RFC 2680, September 1999. [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. [RFC4737] Morton, A., Ciavattone, L., Ramachandran, G., Shalunov, S., and J. Perser, "Packet Reordering Metrics", RFC 4737, November 2006. [RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J. Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)", RFC 5357, October 2008. [RFC5905] Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network Time Protocol Version 4: Protocol and Algorithms Specification", RFC 5905, June 2010. 9.2. Informative References [RFC1242] Bradner, S., "Benchmarking terminology for network interconnection devices", RFC 1242, July 1991. [RFC5481] Morton, A. and B. Claise, "Packet Delay Variation Applicability Statement", RFC 5481, March 2009. [RFC6248] Morton, A., "RFC 4148 and the IP Performance Metrics (IPPM) Registry of Metrics Are Obsolete", RFC 6248, Morton Expires February 27, 2014 [Page 14] Internet-Draft Round-trip Loss August 2013 April 2011. [RFC6390] Clark, A. and B. Claise, "Guidelines for Considering New Performance Metric Development", BCP 170, RFC 6390, October 2011. Author's Address Al Morton AT&T Labs 200 Laurel Avenue South Middletown,, NJ 07748 USA Phone: +1 732 420 1571 Fax: +1 732 368 1192 Email: acmorton@att.com URI: http://home.comcast.net/~acmacm/ Morton Expires February 27, 2014 [Page 15]