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Versions: 00 01 02 03 04 05 06 07 08 RFC 5560

Network Working Group                                      H. Uijterwaal
Internet-Draft                                                  RIPE NCC
Intended status: Standards Track                          April 17, 2007
Expires: October 19, 2007


              A One-Way Packet Duplication Metric for IPPM
                    draft-ietf-ippm-duplicate-00.txt

Status of this Memo

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   This Internet-Draft will expire on October 19, 2007.

Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   The IETF IPPM working group has defined a metric for packet loss.
   The packet loss metric quantifies the case where a packet that is
   sent, never arrives at its destination.  However, the opposite is
   also possible: a packet is sent and arrives more than once.  This
   document defines a metric to quantify these kinds of events.






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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
     1.1.  Requirements notation . . . . . . . . . . . . . . . . . . . 3
     1.2.  Motivation  . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  A Singleton Definition for One-Way Packet Duplication . . . . . 3
     2.1.  Metric Name . . . . . . . . . . . . . . . . . . . . . . . . 3
     2.2.  Metrics Parameters  . . . . . . . . . . . . . . . . . . . . 4
     2.3.  Metric Units  . . . . . . . . . . . . . . . . . . . . . . . 4
     2.4.  Definition  . . . . . . . . . . . . . . . . . . . . . . . . 4
     2.5.  Discussion  . . . . . . . . . . . . . . . . . . . . . . . . 4
     2.6.  Methodology . . . . . . . . . . . . . . . . . . . . . . . . 4
     2.7.  Errors and uncertainties  . . . . . . . . . . . . . . . . . 4
     2.8.  Reporting the metric  . . . . . . . . . . . . . . . . . . . 5
   3.  A definition for Samples of One-way Packet Duplication  . . . . 5
     3.1.  Metric Name . . . . . . . . . . . . . . . . . . . . . . . . 5
     3.2.  Metric Parameters . . . . . . . . . . . . . . . . . . . . . 5
     3.3.  Metric Units  . . . . . . . . . . . . . . . . . . . . . . . 5
     3.4.  Definition  . . . . . . . . . . . . . . . . . . . . . . . . 5
     3.5.  Methodology . . . . . . . . . . . . . . . . . . . . . . . . 5
     3.6.  Errors and uncertainties  . . . . . . . . . . . . . . . . . 5
     3.7.  Reporting the metric  . . . . . . . . . . . . . . . . . . . 6
   4.  Some statistics definitions for One-way Duplication . . . . . . 6
     4.1.  Type-P-one-way-packet-duplication-average . . . . . . . . . 6
   5.  Security Considerations . . . . . . . . . . . . . . . . . . . . 6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . . . 7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . . . 7
     8.2.  Informative References  . . . . . . . . . . . . . . . . . . 7
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . . . 8
   Intellectual Property and Copyright Statements  . . . . . . . . . . 9



















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1.  Introduction

   This document defines a metric for one-way packet duplication across
   Internet paths.  It builds on the IPPM Framework document [RFC2330];
   the reader is assumed to be familiar with that document.

   This document follows the same structure as the document for One-way
   Packet Loss [RFC2680]; the reader is assumed to be familiar with that
   document as well.

   The structure of this memo is as follows:
   o  First, a singleton metric, called Type-P-One-way-packet-
      duplication, is introduced to describe a single instance of packet
      duplication.
   o  Then, this singleton metric is used to define a sample, Type-P-
      One-way-Packet-Duplication-Poisson-Stream, is introduced to
      measure duplication in a series of packets sent.
   o  Finally, a method to summarise the properties of this sample is
      introduced.

1.1.  Requirements notation

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

1.2.  Motivation

   The IETF IPPM working group has defined a metric for packet loss
   [RFC2680].  The packet loss metric quantifies the case where a packet
   that is sent, never arrives at its destination.  However, the
   opposite is also possible: a packet is sent and arrives more than
   once.  This document defines a metric to quantify these kinds of
   events.

   As this document describes a case similar to the one discussed in
   [RFC2680], all considerations from that document on timing and
   accuracy apply.


2.  A Singleton Definition for One-Way Packet Duplication

2.1.  Metric Name

   Type-P-One-way-Packet-Duplication






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2.2.  Metrics Parameters

   o  Src, the IP address of a host
   o  Dst, the IP address of a host
   o  T, a time
   o  T0, a time

2.3.  Metric Units

   A positive integer number

2.4.  Definition

   The value of a Type-P-One-way-Packet-Duplication is a positive
   integer number indicating the number of (uncorrupted and identical)
   copies received by dst in the interval [T, T+T0] for a packet sent by
   src at time T.

   If a packet is sent, but it is lost or does not arrive in the
   interval [T, T+T0], then the metric is undefined.

2.5.  Discussion

   This metric counts the number of packets arriving for each packet
   sent.  The time-out value T0 SHOULD be set to a value when the
   application could potentially still use the packet and not discard it
   automatically.

   The metric only counts packets that are not corrupted during
   transmission and may have been resent automatically by lower layers
   or intermediate devices.  Packets that were corrupted during
   transmission but nevertheless still arrived at dst are not counted.

   If a packet is fragmented and one of the fragments arrives more than
   once, then the packet is counted as duplicated.

2.6.  Methodology

   Refer to section 2.6 of [RFC2680] (We may cut and paste relevant text
   into this document later).

2.7.  Errors and uncertainties

   Refer to section 2.7 of [RFC2680] (We may cut and paste relevant text
   into this document later).






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2.8.  Reporting the metric

   Refer to section 2.8 of [RFC2680] (We may cut and paste relevant text
   into this document later).


3.  A definition for Samples of One-way Packet Duplication

3.1.  Metric Name

   Type-P-One-way-Packet-Duplication-Poisson-Stream

3.2.  Metric Parameters

   o  Src, the IP address of a host
   o  Dst, the IP address of a host
   o  Ts, a time
   o  T0, a time
   o  Tf, a time
   o  lamba, a rate in reciprocal seconds

3.3.  Metric Units

   A sequence of pairs; the elements of each pair are:
   o  T, a time
   o  Type-P-One-way-Packet-Duplication for the packet sent at T.

3.4.  Definition

   Given Ts, Tf and lambda, we compute a pseudo-random Poisson process
   beginning at or before Ts, with average rate lambda and ending at or
   after Tf.  Those time values greater than or equal to Ts, and less
   than or equal to Tf are then selected.  At each of the times in this
   process, we obtain the value of Type-P-One-way-Packet-Duplication.
   the value of the sample is the sequence made up of the resulting
   {time, duplication} pairs.  If there are no such pairs, the sequence
   is of length zero and the sample is said to be empty.

3.5.  Methodology

   Refer to [RFC2680]

3.6.  Errors and uncertainties

   Refer to [RFC2680]






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3.7.  Reporting the metric

   Refer to [RFC2680]


4.  Some statistics definitions for One-way Duplication

4.1.  Type-P-one-way-packet-duplication-average

   This statistics gives an estimate of the fraction of additional
   packets that arrives for every packet that was sent.

   Given a Type-P-One-way-Packet-Duplication-Poisson-Stream, one first
   removes all values of Type-P-One-way-Packet-Duplication which are
   undefined.  For the remaining pairs in the stream, one calculates:
   (Sum Type-P-One-Way-Packet-Duplication/Number of pairs left) - 1 (In
   other words, #packets received/(#sent and not lost).)

   The number can be expressed as a percentage.

   For example, 0% indicates that no duplication occurred in the sample.
   A value of 100% indicates that every packet was duplicated once, a
   value of 200% indicates that every packet was duplicated twice.  Note
   that a value of 100% can also be obtained if half the packets are
   duplicated twice and the other half not.  The statistics cannot show
   this difference, if it is relevant for the application, one will have
   to examine the sample.


5.  Security Considerations

   Conducting Internet measurements raises both security and privacy
   concerns.  This memo does not specify an implementation of the
   metrics, so it does not directly affect the security of the Internet
   nor of applications which run on the Internet.  However,
   implementations of these metrics must be mindful of security and
   privacy concerns.

   There are two types of security concerns: potential harm caused by
   the measurements, and potential harm to the measurements.  The
   measurements could cause harm because they are active, and inject
   packets into the network.  The measurement parameters MUST be
   carefully selected so that the measurements inject trivial amounts of
   additional traffic into the networks they measure.  If they inject
   "too much" traffic, they can skew the results of the measurement, and
   in extreme cases cause congestion and denial of service.

   The measurements themselves could be harmed by routers giving



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   measurement traffic a different priority than "normal" traffic, or by
   an attacker injecting artificial measurement traffic.  If routers can
   recognize measurement traffic and treat it separately, the
   measurements will not reflect actual user traffic.  If an attacker
   injects artificial traffic that is accepted as legitimate, the loss
   rate will be artificially lowered.  Therefore, the measurement
   methodologies SHOULD include appropriate techniques to reduce the
   probability measurement traffic can be distinguished from "normal"
   traffic.  Authentication techniques, such as digital signatures, may
   be used where appropriate to guard against injected traffic attacks.

   The privacy concerns of network measurement are limited by the active
   measurements described in this memo.  Unlike passive measurements,
   there can be no release of existing user data.


6.  IANA Considerations

   This document makes no requests from the IANA.  This section can be
   removed upon publication as a RFC.


7.  Acknowledgements

   The idea to write this draft came up in a meeting with Al Morton,
   Stanislav Shalunov, Emile Stephan and the author.

   This document relies heavily on [RFC2680] and the author likes to
   thank the authors of that document for writing it.

   Finally, thanks are due to ... for their comments.


8.  References

8.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

8.2.  Informative References

   [RFC2330]  Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
              "Framework for IP Performance Metrics", RFC 2330,
              May 1998.

   [RFC2680]  Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
              Packet Loss Metric for IPPM", RFC 2680, September 1999.



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Author's Address

   Henk Uijterwaal
   RIPE NCC
   Singel 258
   1016 AB Amsterdam
   The Netherlands

   Phone: +31 20 535 4444
   Email: henk@ripe.net









































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Full Copyright Statement

   Copyright (C) The IETF Trust (2007).

   This document is subject to the rights, licenses and restrictions
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Acknowledgment

   Funding for the RFC Editor function is provided by the IETF
   Administrative Support Activity (IASA).





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