--- 1/draft-ietf-ippm-loss-episode-metrics-02.txt 2011-10-27 21:14:04.534921278 +0200 +++ 2/draft-ietf-ippm-loss-episode-metrics-03.txt 2011-10-27 21:14:04.574921312 +0200 @@ -1,21 +1,21 @@ Network Working Group N. Duffield Internet-Draft AT&T Labs-Research Intended status: Standards Track A. Morton -Expires: December 22, 2011 AT&T Labs +Expires: April 29, 2012 AT&T Labs J. Sommers Colgate University - June 20, 2011 + October 27, 2011 Loss Episode Metrics for IPPM - draft-ietf-ippm-loss-episode-metrics-02 + draft-ietf-ippm-loss-episode-metrics-03 Abstract The IETF has developed a one way packet loss metric that measures the loss rate on a Poisson probe stream between two hosts. However, the impact of packet loss on applications is in general sensitive not just to the average loss rate, but also to the way in which packet losses are distributed in loss episodes (i.e., maximal sets of consecutively lost probe packets). This draft defines one-way packet loss episode metrics, specifically the frequency and average duration @@ -36,21 +36,21 @@ 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 December 22, 2011. + This Internet-Draft will expire on April 29, 2012. Copyright Notice Copyright (c) 2011 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 @@ -98,21 +98,21 @@ 3.8. Reporting the Metric . . . . . . . . . . . . . . . . . . . 11 4. An active probing methodology for Bi-Packet Loss . . . . . . . 11 4.1. Metric Name . . . . . . . . . . . . . . . . . . . . . . . 11 4.2. Metric Parameters . . . . . . . . . . . . . . . . . . . . 11 4.3. Metric Units . . . . . . . . . . . . . . . . . . . . . . . 12 4.4. Metric Definition . . . . . . . . . . . . . . . . . . . . 12 4.5. Discussion . . . . . . . . . . . . . . . . . . . . . . . . 12 4.6. Methodologies . . . . . . . . . . . . . . . . . . . . . . 12 4.7. Errors and Uncertainties . . . . . . . . . . . . . . . . . 13 4.8. Reporting the Metric . . . . . . . . . . . . . . . . . . . 13 - 5. Loss Epsiode Proto-Metrics . . . . . . . . . . . . . . . . . . 13 + 5. Loss Episode Proto-Metrics . . . . . . . . . . . . . . . . . . 13 5.1. Loss-Pair-Counts . . . . . . . . . . . . . . . . . . . . . 13 5.2. Bi-Packet-Loss-Ratio . . . . . . . . . . . . . . . . . . . 14 5.3. Bi-Packet-Loss-Episode-Duration-Number . . . . . . . . . . 14 5.4. Bi-Packet-Loss-Episode-Frequency-Number . . . . . . . . . 14 6. Loss Episode Metrics derived from Bi-Packet Loss Probing . . . 14 6.1. Geometric Stream: Loss Ratio . . . . . . . . . . . . . . . 15 6.1.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 15 6.1.2. Metric Parameters . . . . . . . . . . . . . . . . . . 15 6.1.3. Metric Units . . . . . . . . . . . . . . . . . . . . . 16 6.1.4. Metric Definition . . . . . . . . . . . . . . . . . . 16 @@ -127,29 +127,29 @@ 6.2.4. Metric Definition . . . . . . . . . . . . . . . . . . 17 6.2.5. Discussion . . . . . . . . . . . . . . . . . . . . . . 17 6.2.6. Methodologies . . . . . . . . . . . . . . . . . . . . 17 6.2.7. Errors and Uncertainties . . . . . . . . . . . . . . . 17 6.2.8. Reporting the Metric . . . . . . . . . . . . . . . . . 18 6.3. Geometric Stream: Loss Episode Frequency . . . . . . . . . 18 6.3.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 18 6.3.2. Metric Parameters . . . . . . . . . . . . . . . . . . 18 6.3.3. Metric Units . . . . . . . . . . . . . . . . . . . . . 18 6.3.4. Metric Definition . . . . . . . . . . . . . . . . . . 18 - 6.3.5. Discussion . . . . . . . . . . . . . . . . . . . . . . 18 + 6.3.5. Discussion . . . . . . . . . . . . . . . . . . . . . . 19 6.3.6. Methodologies . . . . . . . . . . . . . . . . . . . . 19 6.3.7. Errors and Uncertainties . . . . . . . . . . . . . . . 19 6.3.8. Reporting the Metric . . . . . . . . . . . . . . . . . 19 7. Applicability of Loss Episode Metrics . . . . . . . . . . . . 19 7.1. Relation to Gilbert Model . . . . . . . . . . . . . . . . 19 8. IPR Considerations . . . . . . . . . . . . . . . . . . . . . . 20 9. Security Considerations . . . . . . . . . . . . . . . . . . . 20 - 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 20 + 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21 12.1. Normative References . . . . . . . . . . . . . . . . . . . 21 12.2. Informative References . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21 1. Introduction 1.1. Background and Motivation @@ -206,22 +206,22 @@ 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 loss, being sensitive not only to the long term average loss rate, but how losses are distributed in time. As an example: MPEG video traffic may be sensitive to loss involving the I-frame in a group of pictures, but further losses within an episode of sufficiently short duration have no further impact; the damage is already done. - The loss episode metrics presented here represent have the following - useful properties: + The loss episode metrics presented here have the following useful + properties: 1. the metrics are empirical and do not depend on an underlying model; e.g., the loss process is not assumed to be Markovian. On the other hand, it turns out that the metrics of this memo can be related to the special case of the Gilbert Model parameters; see Section 7. 2. the metric units can be directly compared with applications or user requirements or tolerance for network loss performance, in the frequency and duration of loss episodes, as well as the usual @@ -314,22 +314,21 @@ o P, the specification of the packet type, over and above the source and destination addresses 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 + The metric unit of Type-P-One-way-Bi-Packet-Loss 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, @@ -418,24 +417,37 @@ The metric definition of Type-P-One-way-Bi-Packet-Loss-Stream is sufficiently general to describe the case where packets are sampled from a pre-existing stream. This is useful in the case that there is a general purpose measurement stream setup between two hosts, and we which to select a substream from it for the purposes of loss episode measurement. In the next section we specialize this somewhat to more concretely describe a purpose built packet stream for loss episode measurement. 3.6. 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-Stream metric described above. In particular, the + methodologies described in RFC 2680 apply to both packets of each + pair. + 3.7. 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 each pair for the Type-P- + One-way-Bi-Packet-Loss-Stream metric. + 3.8. Reporting the Metric + Refer to Section 2.8 of [RFC2680]. + 4. An active probing methodology for Bi-Packet Loss This section specializes the preceding section for an active probing methodology. The basic idea is a follows. We set up a sequence of evenly spaced times T1 < T2 < ... < Tn. Each time Ti is potentially the first packet time for a packet pair measurement. We make an independent random decision at each time, whether to initiate such a measurement. Hence the interval count between successive times at which a pair is initiated follows a geometric distribution. We also specify that the spacing between successive times Ti is the same as @@ -527,21 +538,21 @@ schedule. Note that the choice of time spacing directly affects the ability of the host CPU to meet the required schedule (e.g., consider a 100 microsecond spacing versus a 100 millisecond spacing). For other considerations, refer to Section 3.7. [RFC2680]. 4.8. Reporting the Metric Refer to Section 3.8. of [RFC2680]. -5. Loss Epsiode Proto-Metrics +5. Loss Episode Proto-Metrics This section describes four generic proto-metric quantities associated with an arbitrary set of loss pairs. These are the Loss- Pair-Counts, Bi-Packet-Loss-Ratio, Bi-Packet-Loss-Episode-Duration- Number, Bi-Packet-Loss-Episode-Frequency-Number. Specific loss episode metrics can then be constructed when these proto metrics take as their input, sets of loss pairs samples generated by the Type-P- One-way-Bi-Packet-Loss-Stream and Type-P-One-way-Bi-Packet-Loss- Geometric Stream. The second of these is described in Section 4. It is not expected that these proto-metrics would be reported @@ -783,21 +793,21 @@ and destination address 6.3.3. Metric Units A positive number. 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, then dividing he result by the launch spacing + metric parameters, then dividing the result by the launch spacing parameter d. 6.3.5. Discussion Type-P-One-way-Bi-Packet-Loss-Geometric-Stream-Episode-Frequency estimates the average frequency per unit time with which loss episodes start (or finish). The frequency relative to the count of potential probe launches is obtained by multiplying the metric value by the packet launch spacing parameter d. @@ -845,24 +855,23 @@ r = P(b|g)/(P(b|g) + P(g|b)) and m/d = 1/P(g|b). These relationships can be inverted in order to recover the Gilbert model parameters: P(g|b) = d/m and P(b|g)=d/m/(1/r - 1) 8. 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/ + An IPR disclosure concerning some of the material covered in this + draft has been made to the IETF: see + https://datatracker.ietf.org/ipr/1354/ 9. 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. @@ -883,44 +892,45 @@ 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. 10. IANA Considerations + 11. Acknowledgements 12. References 12.1. 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. + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, March 1997. + + [RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network + performance measurement with periodic streams", RFC 3432, + November 2002. + 12.2. 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