Packet Reordering Metrics
RFC 4737

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Network Working Group                                          A. Morton
Request for Comments: 4737                                 L. Ciavattone
Category: Standards Track                                G. Ramachandran
                                                               AT&T Labs
                                                             S. Shalunov
                                                               Internet2
                                                               J. Perser
                                                                Veriwave
                                                           November 2006

                       Packet Reordering Metrics

Status of This Memo

   This document specifies an Internet standards track protocol for the
   Internet community, and requests discussion and suggestions for
   improvements.  Please refer to the current edition of the "Internet
   Official Protocol Standards" (STD 1) for the standardization state
   and status of this protocol.  Distribution of this memo is unlimited.

Copyright Notice

   Copyright (C) The IETF Trust (2006).

Abstract

   This memo defines metrics to evaluate whether a network has
   maintained packet order on a packet-by-packet basis.  It provides
   motivations for the new metrics and discusses the measurement issues,
   including the context information required for all metrics.  The memo
   first defines a reordered singleton, and then uses it as the basis
   for sample metrics to quantify the extent of reordering in several
   useful dimensions for network characterization or receiver design.
   Additional metrics quantify the frequency of reordering and the
   distance between separate occurrences.  We then define a metric
   oriented toward assessment of reordering effects on TCP.  Several
   examples of evaluation using the various sample metrics are included.
   An appendix gives extended definitions for evaluating order with
   packet fragmentation.

Morton, et al.           Standards Track                        [Page 1]
RFC 4737               Packet Reordering Metrics           November 2006

Table of Contents

   1. Introduction ....................................................4
      1.1. Motivation .................................................4
      1.2. Goals and Objectives .......................................5
      1.3. Required Context for All Reordering Metrics ................6
   2. Conventions Used in this Document ...............................7
   3. A Reordered Packet Singleton Metric .............................7
      3.1. Metric Name ................................................8
      3.2. Metric Parameters ..........................................8
      3.3. Definition .................................................8
      3.4. Sequence Discontinuity Definition ..........................9
      3.5. Evaluation of Reordering in Dimensions of Time or Bytes ...10
      3.6. Discussion ................................................10
   4. Sample Metrics .................................................11
      4.1. Reordered Packet Ratio ....................................11
           4.1.1. Metric Name ........................................11
           4.1.2. Metric Parameters ..................................11
           4.1.3. Definition .........................................12
           4.1.4. Discussion .........................................12
      4.2. Reordering Extent .........................................12
           4.2.1. Metric Name ........................................12
           4.2.2. Notation and Metric Parameters .....................12
           4.2.3. Definition .........................................13
           4.2.4. Discussion .........................................13
      4.3. Reordering Late Time Offset ...............................14
           4.3.1. Metric Name ........................................14
           4.3.2. Metric Parameters ..................................14
           4.3.3. Definition .........................................15
           4.3.4. Discussion .........................................15
      4.4. Reordering Byte Offset ....................................16
           4.4.1. Metric Name ........................................16
           4.4.2. Metric Parameters ..................................16
           4.4.3. Definition .........................................16
           4.4.4. Discussion .........................................17
      4.5. Gaps between Multiple Reordering Discontinuities ..........17
           4.5.1. Metric Names .......................................17
           4.5.2. Parameters .........................................17
           4.5.3. Definition of Reordering Discontinuity .............17
           4.5.4. Definition of Reordering Gap .......................18
           4.5.5. Discussion .........................................18