Packet Delay Variation Applicability Statement
RFC 5481

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Network Working Group                                          A. Morton
Request for Comments: 5481                                     AT&T Labs
Category: Informational                                        B. Claise
                                                     Cisco Systems, Inc.
                                                              March 2009

             Packet Delay Variation Applicability Statement

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.

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Morton & Claise              Informational                      [Page 1]
RFC 5481                   Delay Variation AS                 March 2009

Abstract

   Packet delay variation metrics appear in many different standards
   documents.  The metric definition in RFC 3393 has considerable
   flexibility, and it allows multiple formulations of delay variation
   through the specification of different packet selection functions.

   Although flexibility provides wide coverage and room for new ideas,
   it can make comparisons of independent implementations more
   difficult.  Two different formulations of delay variation have come
   into wide use in the context of active measurements.  This memo
   examines a range of circumstances for active measurements of delay
   variation and their uses, and recommends which of the two forms is
   best matched to particular conditions and tasks.

Table of Contents

   1. Introduction ....................................................4
      1.1. Requirements Language ......................................5
      1.2. Background Literature in IPPM and Elsewhere ................5
      1.3. Organization of the Memo ...................................6
   2. Purpose and Scope ...............................................7
   3. Brief Descriptions of Delay Variation Uses ......................7
      3.1. Inferring Queue Occupation on a Path .......................7
      3.2. Determining De-Jitter Buffer Size ..........................8
      3.3. Spatial Composition .......................................10
      3.4. Service-Level Comparison ..................................10
      3.5. Application-Layer FEC Design ..............................10
   4. Formulations of IPDV and PDV ...................................10
      4.1. IPDV: Inter-Packet Delay Variation ........................11
      4.2. PDV: Packet Delay Variation ...............................11
      4.3. A "Point" about Measurement Points ........................12
      4.4. Examples and Initial Comparisons ..........................12
   5. Survey of Earlier Comparisons ..................................13
      5.1. Demichelis' Comparison ....................................13
      5.2. Ciavattone et al. .........................................15
      5.3. IPPM List Discussion from 2000 ............................16
      5.4. Y.1540 Appendix II ........................................18
      5.5. Clark's ITU-T SG 12 Contribution ..........................18
   6. Additional Properties and Comparisons ..........................18
      6.1. Packet Loss ...............................................18
      6.2. Path Changes ..............................................19
           6.2.1. Lossless Path Change ...............................20
           6.2.2. Path Change with Loss ..............................21
      6.3. Clock Stability and Error .................................22
      6.4. Spatial Composition .......................................24
      6.5. Reporting a Single Number (SLA) ...........................24
      6.6. Jitter in RTCP Reports ....................................25

Morton & Claise              Informational                      [Page 2]