Framework for IP Performance Metrics
RFC 2330
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
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