Framework for IP Performance Metrics
RFC 2330

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Network Working Group                                          V. Paxson
Request for Comments: 2330                Lawrence Berkeley National Lab
Category: Informational                                         G. Almes
                                             Advanced Network & Services
                                                              J. Mahdavi
                                                               M. Mathis
                                         Pittsburgh Supercomputer Center
                                                                May 1998

                  Framework for IP Performance Metrics

1. Status of this Memo

   This memo provides information for the Internet community.  It does
   not specify an Internet standard of any kind.  Distribution of this
   memo is unlimited.

2. Copyright Notice

   Copyright (C) The Internet Society (1998).  All Rights Reserved.

Table of Contents

   1.  STATUS OF THIS MEMO.............................................1
   2.  COPYRIGHT NOTICE................................................1
   3.  INTRODUCTION....................................................2
   4.  CRITERIA FOR IP PERFORMANCE METRICS.............................3
   5.  TERMINOLOGY FOR PATHS AND CLOUDS................................4
   6.  FUNDAMENTAL CONCEPTS............................................5
     6.1  Metrics......................................................5
     6.2  Measurement Methodology......................................6
     6.3  Measurements, Uncertainties, and Errors......................7
   7.  METRICS AND THE ANALYTICAL FRAMEWORK............................8
   8.  EMPIRICALLY SPECIFIED METRICS..................................11
   9.  TWO FORMS OF COMPOSITION.......................................12
     9.1  Spatial Composition of Metrics..............................12
     9.2  Temporal Composition of Formal Models and Empirical Metrics.13
   10.  ISSUES RELATED TO TIME........................................14
     10.1  Clock Issues...............................................14
     10.2  The Notion of "Wire Time"..................................17
   11. SINGLETONS, SAMPLES, AND STATISTICS............................19
     11.1  Methods of Collecting Samples..............................20
       11.1.1 Poisson Sampling........................................21
       11.1.2 Geometric Sampling......................................22
       11.1.3 Generating Poisson Sampling Intervals...................22

Paxson, et. al.              Informational                      [Page 1]
RFC 2330          Framework for IP Performance Metrics          May 1998

     11.2  Self-Consistency...........................................24
     11.3  Defining Statistical Distributions.........................25
     11.4  Testing For Goodness-of-Fit................................27
   12. AVOIDING STOCHASTIC METRICS....................................28
   13. PACKETS OF TYPE P..............................................29
   14. INTERNET ADDRESSES VS. HOSTS...................................30
   15. STANDARD-FORMED PACKETS........................................30
   16. ACKNOWLEDGEMENTS...............................................31
   17. SECURITY CONSIDERATIONS........................................31
   18. APPENDIX.......................................................32
   19. REFERENCES.....................................................38
   20. AUTHORS' ADDRESSES.............................................39
   21. FULL COPYRIGHT STATEMENT.......................................40

3. Introduction

   The purpose of this memo is to define a general framework for
   particular metrics to be developed by the IETF's IP Performance
   Metrics effort, begun by the Benchmarking Methodology Working Group
   (BMWG) of the Operational Requirements Area, and being continued by
   the IP Performance Metrics Working Group (IPPM) of the Transport
   Area.

   We begin by laying out several criteria for the metrics that we
   adopt.  These criteria are designed to promote an IPPM effort that
   will maximize an accurate common understanding by Internet users and
   Internet providers of the performance and reliability both of end-
   to-end paths through the Internet and of specific 'IP clouds' that
   comprise portions of those paths.

   We next define some Internet vocabulary that will allow us to speak
   clearly about Internet components such as routers, paths, and clouds.

   We then define the fundamental concepts of 'metric' and 'measurement
   methodology', which allow us to speak clearly about measurement
   issues.  Given these concepts, we proceed to discuss the important
   issue of measurement uncertainties and errors, and develop a key,
   somewhat subtle notion of how they relate to the analytical framework
   shared by many aspects of the Internet engineering discipline.  We
   then introduce the notion of empirically defined metrics, and finish