Network Working Group A. Jayasumana
Request for Comments: 5236 Colorado State University
Category: Informational N. Piratla
Deutsche Telekom Labs
T. Banka
Colorado State University
A. Bare
R. Whitner
Agilent Technologies, Inc.
June 2008
Improved Packet Reordering Metrics
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.
IESG Note
The content of this RFC was at one time considered by the IETF, and
therefore it may resemble a current IETF work in progress or a
published IETF work. The IETF standard for reordering metrics is RFC
4737. The metrics in this document were not adopted for inclusion in
RFC 4737. This RFC is not a candidate for any level of Internet
Standard. The IETF disclaims any knowledge of the fitness of this
RFC for any purpose and in particular notes that the decision to
publish is not based on IETF review for such things as security,
congestion control, or inappropriate interaction with deployed
protocols. The RFC Editor has chosen to publish this document at its
discretion. Readers of this RFC should exercise caution in
evaluating its value for implementation and deployment. See RFC 3932
for more information.
Abstract
This document presents two improved metrics for packet reordering,
namely, Reorder Density (RD) and Reorder Buffer-occupancy Density
(RBD). A threshold is used to clearly define when a packet is
considered lost, to bound computational complexity at O(N), and to
keep the memory requirement for evaluation independent of N, where N
is the length of the packet sequence. RD is a comprehensive metric
that captures the characteristics of reordering, while RBD evaluates
the sequences from the point of view of recovery from reordering.
Jayasumana, et al. Informational [Page 1]RFC 5236 Improved Packet Reordering Metrics June 2008
These metrics are simple to compute yet comprehensive in their
characterization of packet reordering. The measures are robust and
orthogonal to packet loss and duplication.
Table of Contents
1. Introduction and Motivation .....................................3
2. Attributes of Packet Reordering Metrics .........................4
3. Reorder Density and Reorder Buffer-Occupancy Density ............7
3.1. Receive Index (RI) .........................................8
3.2. Out-of-Order Packet ........................................9
3.3. Displacement (D) ...........................................9
3.4. Displacement Threshold (DT) ................................9
3.5. Displacement Frequency (FD) ...............................10
3.6. Reorder Density (RD) ......................................10
3.7. Expected Packet (E) .......................................10
3.8. Buffer Occupancy (B) ......................................10
3.9. Buffer-Occupancy Threshold (BT) ...........................11
3.10. Buffer-Occupancy Frequency (FB) ..........................11
3.11. Reorder Buffer-Occupancy Density (RBD) ...................11
4. Representation of Packet Reordering and Reorder Density ........11
5. Selection of DT ................................................12
6. Detection of Lost and Duplicate Packets ........................13
7. Algorithms to Evaluate RD and RBD ..............................14
7.1. Algorithm for RD ..........................................14
7.2. Algorithm for RBD .........................................16
8. Examples .......................................................17
9. Characteristics Derivable from RD and RBD ......................21
10. Comparison with Other Metrics .................................22
11. Security Considerations .......................................22
12. References ....................................................22
12.1. Normative References .....................................22
12.2. Informative References ...................................22
13. Contributors ..................................................24
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