Network Working Group N. Duffield Internet-Draft AT&T Labs-Research Intended status: Standards Track A. Morton Expires: January 10, 2010 AT&T Labs J. Sommers Colgate University July 9, 2009 Burst Loss Metrics for IPPM draft-duffield-ippm-burst-loss-metrics-01 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. This document may contain material from IETF Documents or IETF Contributions published or made publicly available before November 10, 2008. The person(s) controlling the copyright in some of this material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format it for publication as an RFC or to translate it into languages other than English. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 10, 2010. Copyright Notice Copyright (c) 2009 IETF Trust and the persons identified as the Duffield, et al. Expires January 10, 2010 [Page 1] Internet-Draft Burst Loss Metrics for IPPM July 2009 document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract The IPPM Working Group has developed a one way packet loss metric that measures the loss rate on a Poisson probe stream between two hosts. However, the burst properties of packet loss are required to understand the impact of packet loss on applications. This draft defines one-way burst packet loss metrics that express the frequency and duration of loss episode, i.e., maximal sets of consecutively lost probe packets. The draft also defines a probing methodology under which the burst loss metrics are to be measured. 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]. Duffield, et al. Expires January 10, 2010 [Page 2] Internet-Draft Burst Loss Metrics for IPPM July 2009 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 5 2. Singleton Definition for Type-P-One-way Bi-Packet Loss . . . . 5 2.1. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 5 2.2. Metric Parameters . . . . . . . . . . . . . . . . . . . . 5 2.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 6 2.4. Metric Definition . . . . . . . . . . . . . . . . . . . . 6 2.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 6 2.6. Methodologies . . . . . . . . . . . . . . . . . . . . . . 6 2.7. Errors and Uncertainties . . . . . . . . . . . . . . . . . 6 2.8. Reporting the Metric . . . . . . . . . . . . . . . . . . . 7 3. General Definition of samples for Type-P-One-way-Bi-Packet-Loss . . . . . . . . . . . . . . . . 7 3.1. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 7 3.2. Metric Parameters . . . . . . . . . . . . . . . . . . . . 7 3.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 7 3.4. Metric Definition . . . . . . . . . . . . . . . . . . . . 7 3.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 8 3.6. Methodologies . . . . . . . . . . . . . . . . . . . . . . 8 3.7. Errors and Uncertainties . . . . . . . . . . . . . . . . . 8 3.8. Reporting the Metric . . . . . . . . . . . . . . . . . . . 8 4. An active probing methodology for Bi-Packet Loss . . . . . . . 8 4.1. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 8 4.2. Metric Parameters . . . . . . . . . . . . . . . . . . . . 8 4.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 9 4.4. Metric Definition . . . . . . . . . . . . . . . . . . . . 9 4.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 9 4.6. Methodologies . . . . . . . . . . . . . . . . . . . . . . 9 4.7. Errors and Uncertainties . . . . . . . . . . . . . . . . . 10 4.8. Reporting the Metric . . . . . . . . . . . . . . . . . . . 10 5. Burst Loss Proto-Metrics . . . . . . . . . . . . . . . . . . . 10 5.1. Loss-Pair-Counts . . . . . . . . . . . . . . . . . . . . . 10 5.2. Bi-Packet-Loss-Ratio . . . . . . . . . . . . . . . . . . . 10 5.3. Bi-Packet-Loss-Episode-Duration . . . . . . . . . . . . . 11 5.4. Bi-Packet-Loss-Episode-Frequency . . . . . . . . . . . . . 11 6. Burst Loss Metrics derived from Bi-Packet Loss Probing . . . . 11 6.1. Geometric Stream: Loss Ratio . . . . . . . . . . . . . . . 12 6.1.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 12 6.1.2. Metric Parameters . . . . . . . . . . . . . . . . . . 12 6.1.3. Metric Units . . . . . . . . . . . . . . . . . . . . . 12 6.1.4. Metric Definition . . . . . . . . . . . . . . . . . . 13 6.1.5. Discussion . . . . . . . . . . . . . . . . . . . . . . 13 6.1.6. Methodologies . . . . . . . . . . . . . . . . . . . . 13 6.1.7. Errors and Uncertainties . . . . . . . . . . . . . . . 13 6.1.8. Reporting the Metric . . . . . . . . . . . . . . . . . 13 6.2. Geometric Steam: Loss Episode Duration . . . . . . . . . . 13 6.2.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 13 Duffield, et al. Expires January 10, 2010 [Page 3] Internet-Draft Burst Loss Metrics for IPPM July 2009 6.2.2. Metric Parameters . . . . . . . . . . . . . . . . . . 13 6.2.3. Metric Units . . . . . . . . . . . . . . . . . . . . . 14 6.2.4. Metric Definition . . . . . . . . . . . . . . . . . . 14 6.2.5. Discussion . . . . . . . . . . . . . . . . . . . . . . 14 6.2.6. Methodologies . . . . . . . . . . . . . . . . . . . . 14 6.2.7. Errors and Uncertainties . . . . . . . . . . . . . . . 14 6.2.8. Reporting the Metric . . . . . . . . . . . . . . . . . 14 6.3. Geometric Stream: Loss Episode Frequency . . . . . . . . . 14 6.3.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 14 6.3.2. Metric Parameters . . . . . . . . . . . . . . . . . . 14 6.3.3. Metric Units . . . . . . . . . . . . . . . . . . . . . 15 6.3.4. Metric Definition . . . . . . . . . . . . . . . . . . 15 6.3.5. Discussion . . . . . . . . . . . . . . . . . . . . . . 15 6.3.6. Methodologies . . . . . . . . . . . . . . . . . . . . 15 6.3.7. Errors and Uncertainties . . . . . . . . . . . . . . . 15 6.3.8. Reporting the Metric . . . . . . . . . . . . . . . . . 16 7. IPR Considerations . . . . . . . . . . . . . . . . . . . . . . 16 8. Security Considerations . . . . . . . . . . . . . . . . . . . 16 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 17 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 17 11.1. Normative References . . . . . . . . . . . . . . . . . . . 17 11.2. Informative References . . . . . . . . . . . . . . . . . . 17 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 17 Duffield, et al. Expires January 10, 2010 [Page 4] Internet-Draft Burst Loss Metrics for IPPM July 2009 1. Introduction This memo describes one-way burst packet loss metrics. The losses experienced by the packet stream can be viewed as occurring in loss episodes, i.e., maximal set of consecutive lost packets. The burst loss metrics express the frequency and duration of loss episodes. Although the average loss ratio can be expressed in terms of these quantities, they go further in characterizing the statistics of the patterns of packet loss within the stream of probes. This is useful information in understanding the effect of packet losses on application performance, since different applications can have different sensitivities to patterns of burst loss, being sensitive not only to the long term average loss rate, but how losses are distributed in time, i.e., bursty vs. occurring independently. As an example: MPEG video traffic may be sensitive to loss involving the I-frame in a group of pictures, but further burst losses of sufficiently short duration have no further impact (the damage is already done). The metrics defined in this memo are "derived metrics", according to Section 6.1 of [RFC2330] the IPPM framework. They are based on the singleton loss metric defined in Section 2 of [RFC2680] . This is a working draft with several sections still to be completed. 2. Singleton Definition for Type-P-One-way Bi-Packet Loss 2.1. Metric Name Type-P-One-way-Bi-Packet-Loss 2.2. Metric Parameters o Src, the IP address of a source host o Dst, the IP address of a destination host o T1, a sending time of the first packet o T2, a sending time of the second packet, with T2>T1 o F, a selection function defining unambiguously the two packets from the stream selected for the metric. o P, the specification of the packet type, over and above the source and destination addresses Duffield, et al. Expires January 10, 2010 [Page 5] Internet-Draft Burst Loss Metrics for IPPM July 2009 2.3. Metric Units A Loss Pair is pair (l1, l2) where each of l1 and l2 is a binary value 0 or 1, where 0 signifies successful transmission of a packet and 1 signifies loss. The metric unit for Type-P-One-way-Bi-Packet-Loss takes is a Loss Pair 2.4. Metric Definition 1. "The Type-P-One-way-Bi-Packet-Loss with parameters (Src, Dst, T1, T2, F, P) is (1,1)" means that Src sent the first bit of a Type-P packet to Dst at wire-time T1 and the first bit of a Type-P packet to Dst a wire-time T2>T1, and that neither packet was received at Dst. 2. The Type-P-One-way-Bi-Packet-Loss with parameters (Src, Dst, T1, T2, F, P) is (1,0)" means that Src sent the first bit of a Type-P packet to Dst at wire-time T1 and the first bit of a Type-P packet to Dst a wire-time T2>T1, and that the first packet was not received at Dst, and the second packet was received at Dst 3. The Type-P-One-way-Bi-Packet-Loss with parameters (Src, Dst, T1, T2, F, P) is (0,1)" means that Src sent the first bit of a Type-P packet to Dst at wire-time T1 and the first bit of a Type-P packet to Dst a wire-time T2>T1, and that the first packet was received at Dst, and the second packet was not received at Dst 4. The Type-P-One-way-Bi-Packet-Loss with parameters (Src, Dst, T1, T2, F, P) is (0,0)" means that Src sent the first bit of a Type-P packet to Dst at wire-time T1 and the first bit of a Type-P packet to Dst a wire-time T2>T1, and that both packet were received at Dst. 2.5. Discussion 2.6. Methodologies The methodologies related to the Type-P-One-way-Packet-Loss metric in Section 2.6 of [RFC2680] are similar for the Type-P-One-way-Bi- Packet-Loss metric described above. In particular, the methodologies described in RFC 2680 apply to both packets of the pair. 2.7. Errors and Uncertainties Sources of error for the Type-P-One-way-Packet-Loss metric in Section 2.7 of [RFC2680] apply to each packet of the pair for the Type-P-One- Duffield, et al. Expires January 10, 2010 [Page 6] Internet-Draft Burst Loss Metrics for IPPM July 2009 way-Bi-Packet-Loss metric. 2.8. Reporting the Metric Refer to Section 2.8 of [RFC2680]. 3. General Definition of samples for Type-P-One-way-Bi-Packet-Loss Given the singleton metric for Type-P-One-way-Bi-Packet-Loss, we now define examples of samples of singletons. The basic idea is as follows. We first specify a set of times T1 < T2 <...1 o 0 if N(0,1) + N(1,0) + N(1,1) = 0 (no probe packets lost) o Undefined if N(0,1) + N(1,0) + N(0,0) = 0 (all probe packets lost) Note N(0,1) + N(1,0) is zero if there are no transitions between loss and no-loss outcomes. 5.4. Bi-Packet-Loss-Episode-Frequency The Bi-Packet-Loss-Episode-Frequency associated with a set of n loss pairs L1,,,,Ln is defined in terms of their Loss-Pair-Counts as Bi- Packet-Loss-Ratio / Bi-Packet-Loss-Episode-Duration, when this can be defined, specifically, it is: o (N(1,0)+N(1,1)) * (N(0,1)+N(1,0)) / (2*N(1,1)+N(0,1)+N(1,0) ) / n if N(0,1)+N(0,1) > 0 o 0 if N(0,1)+N(1,0) +N(1,1) = 0 (no probe packets lost) o 1 if N(0,1) +N(1,0) +N(0,0) = 0 (all probe packets lost) 6. Burst Loss Metrics derived from Bi-Packet Loss Probing Metrics for the frequency and duration of loss episodes are now defined as functions of set of n loss pairs L1,....,Ln. Although a loss episode is defined as a maximal set of successive lost packets, the burst loss metrics are not defined directly in terms of the sequential patterns of packet loss exhibited by loss pairs. This is because samples, including Type-P-One-way-Bi-Packet-Loss-Geometric- Stream, generally do not report all lost packets in each episode. Instead, the metrics are defined as functions of the Loss-Pair-Counts of the sample, for reasons that are now described. Consider an idealized Type-P-One-way-Bi-Packet-Loss-Geometric-Stream Duffield, et al. Expires January 10, 2010 [Page 11] Internet-Draft Burst Loss Metrics for IPPM July 2009 sample in which the launch probability q =1. It is shown in [SBDR08] that the average number of packets in a loss episode of this ideal sample is exactly the Bi-Packet-Loss-Episode-Duration derived from its set of loss pairs. Note this computation makes no reference to the position of lost packet in the sequence of probes. A general Type-P-One-way-Bi-Packet-Loss-Geometric-Stream sample with launch probability q < 1, independently samples, with probability q, each loss pair of an idealized sample. On average, the Loss-Pair- Counts (if normalized by the total number of pairs) will be the same as in the idealized sample. The burst loss metrics in the general case are thus estimators of those for the idealized case; the statistical properties of this estimation, including a derivation of the estimation variance, is provided in [SBDR08]. 6.1. Geometric Stream: Loss Ratio 6.1.1. Metric Name Type-P-One-way-Bi-Packet-Loss-Geometric-Stream-Ratio 6.1.2. Metric Parameters o Src, the IP address of a source host o Dst, the IP address of a destination host o T0, the randomly selected starting time [RFC3432] for periodic launch opportunities o d, the time spacing between potential launch times, Ti and Ti+1 o n, a count of potential measurement instants o q, a launch probability o F, a selection function defining unambiguously the two packets from the stream selected for the metric. o P, the specification of the packet type, over and above the source and destination address 6.1.3. Metric Units A number in the interval [0,1] Duffield, et al. Expires January 10, 2010 [Page 12] Internet-Draft Burst Loss Metrics for IPPM July 2009 6.1.4. Metric Definition The result obtained by computing the Bi-Packet-Loss-Ratio over a Type-P-One-way-Bi-Packet-Loss-Geometric-Stream sample with the metric parameters. 6.1.5. Discussion 6.1.6. Methodologies Refer to Section 4.6 6.1.7. Errors and Uncertainties Because Type-P-One-way-Bi-Packet-Loss-Geometric-Stream is sampled in general (when the lauch probability q <1) the metrics described in this Section can be regarded as statistical estimators of the corresponding idealized version corresponding to q = 1. Estimation variance as it applies to Type-P-One-way-Bi-Packet-Loss-Geometric- Stream-Loss-Ratio is described in [SBDR08]. For other issues refer to Section 4.7 6.1.8. Reporting the Metric Refer to Section 4.8 6.2. Geometric Steam: Loss Episode Duration 6.2.1. Metric Name Type-P-One-way-Bi-Packet-Loss-Geometric-Stream-Episode-Duration 6.2.2. Metric Parameters o Src, the IP address of a source host o Dst, the IP address of a destination host o T0, the randomly selected starting time [RFC3432] for periodic launch opportunities o d, the time spacing between potential launch times, Ti and Ti+1 o n, a count of potential measurement instants o q, a launch probability Duffield, et al. Expires January 10, 2010 [Page 13] Internet-Draft Burst Loss Metrics for IPPM July 2009 o F, a selection function defining unambiguously the two packets from the stream selected for the metric. o P, the specification of the packet type, over and above the source and destination address 6.2.3. Metric Units A non-negative number of seconds. 6.2.4. Metric Definition The result obtained by computing the Bi-Packet-Loss-Episode-Duration over a Type-P-One-way-Bi-Packet-Loss-Geometric-Stream sample with the metric parameters. 6.2.5. Discussion 6.2.6. Methodologies Refer to Section 4.6 6.2.7. Errors and Uncertainties Because Type-P-One-way-Bi-Packet-Loss-Geometric-Stream is sampled in general (when the lauch probability q <1) the metrics described in this Section can be regarded as statistical estimators of the corresponding idealized version corresponding to q = 1. Estimation variance as it applies to Type-P-One-way-Bi-Packet-Loss-Geometric- Stream-Episode-Duration is described in [SBDR08]. For other issues refer to Section 4.7 6.2.8. Reporting the Metric Refer to Section 4.8 6.3. Geometric Stream: Loss Episode Frequency 6.3.1. Metric Name Type-P-One-way-Bi-Packet-Loss-Geometric-Stream-Episode-Frequency 6.3.2. Metric Parameters o Src, the IP address of a source host Duffield, et al. Expires January 10, 2010 [Page 14] Internet-Draft Burst Loss Metrics for IPPM July 2009 o Dst, the IP address of a destination host o T0, the randomly selected starting time [RFC3432] for periodic launch opportunities o d, the time spacing between potential launch times, Ti and Ti+1 o n, a count of potential measurement instants o q, a launch probability o F, a selection function defining unambiguously the two packets from the stream selected for the metric. o P, the specification of the packet type, over and above the source and destination address 6.3.3. Metric Units A number in the interval [0,1] 6.3.4. Metric Definition The result obtained by computing the Bi-Packet-Loss-Episode-Frequency over a Type-P-One-way-Bi-Packet-Loss-Geometric-Stream sample with the metric parameters . 6.3.5. Discussion 6.3.6. Methodologies Refer toSection 4.6 6.3.7. Errors and Uncertainties Because Type-P-One-way-Bi-Packet-Loss-Geometric-Stream is sampled in general (when the lauch probability q <1) the metrics described in this Section can be regarded as statistical estimators of the corresponding idealized version corresponding to q = 1. Estimation variance as it applies to Type-P-One-way-Bi-Packet-Loss-Geometric- Stream-Episode-Frequency is described in [SBDR08]. For other issues refer to Section 4.7 Duffield, et al. Expires January 10, 2010 [Page 15] Internet-Draft Burst Loss Metrics for IPPM July 2009 6.3.8. Reporting the Metric Refer to Section 4.8 7. IPR Considerations IPR disclosures concerning some of the material covered in this draft has been made to the IETF: see https://datatracker.ietf.org/ipr/1009/ , https://datatracker.ietf.org/ipr/1010/ , and https://datatracker.ietf.org/ipr/1126/ 8. Security Considerations Conducting Internet measurements raises both security and privacy concerns. This memo does not specify an implementation of the metrics, so it does not directly affect the security of the Internet nor of applications which run on the Internet. However,implementations of these metrics must be mindful of security and privacy concerns. There are two types of security concerns: potential harm caused by the measurements, and potential harm to the measurements. The measurements could cause harm because they are active, and inject packets into the network. The measurement parameters MUST be carefully selected so that the measurements inject trivial amounts of additional traffic into the networks they measure. If they inject "too much" traffic, they can skew the results of the measurement, and in extreme cases cause congestion and denial of service. The measurements themselves could be harmed by routers giving measurement traffic a different priority than "normal" traffic, or by an attacker injecting artificial measurement traffic. If routers can recognize measurement traffic and treat it separately, the measurements may not reflect actual user traffic. If an attacker injects artificial traffic that is accepted as legitimate, the loss rate will be artificially lowered. Therefore, the measurement methodologies SHOULD include appropriate techniques to reduce the probability that measurement traffic can be distinguished from "normal" traffic. Authentication techniques, such as digital signatures, may be used where appropriate to guard against injected traffic attacks. The privacy concerns of network measurement are limited by the active measurements described in this memo: they involve no release of user data. 9. IANA Considerations Duffield, et al. Expires January 10, 2010 [Page 16] Internet-Draft Burst Loss Metrics for IPPM July 2009 10. Acknowledgements 11. References 11.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way Packet Loss Metric for IPPM", RFC 2680, 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. [RFC3611] Friedman, T., Caceres, R., and A. Clark, "RTP Control Protocol Extended Reports (RTCP XR)", RFC 3611, November 2003. 11.2. Informative References [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, "Framework for IP Performance Metrics", RFC 2330, May 1998. [RFC3357] Koodli, R. and R. Ravikanth, "One-way Loss Pattern Sample Metrics", RFC 3357, August 2002. [SBDR08] IEEE/ACM Transactions on Networking, 16(2): 307-320, "A Geometric Approach to Improving Active Packet Loss Measurement", 2008. Duffield, et al. Expires January 10, 2010 [Page 17] Internet-Draft Burst Loss Metrics for IPPM July 2009 Authors' Addresses Nick Duffield AT&T Labs-Research 180 Park Avenue Florham Park, NJ 07932 USA Phone: +1 973 360 8726 Fax: Email: duffield@research.att.com URI: http://www.research.att.com/info/duffield 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/ Joel Sommers Colgate University 304 McGregory Hall Hamilton, NY 13346 USA Phone: +1 315 228 7587 Fax: Email: jsommers@colgate.edu URI: http://cs.colgate.edu/faculty/jsommers Duffield, et al. Expires January 10, 2010 [Page 18]