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
By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
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.
Uijterwaal Expires October 19, 2007 [Page 1]
Internet-Draft Packet Duplication Metric April 2007
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
Uijterwaal Expires October 19, 2007 [Page 2]
Internet-Draft Packet Duplication Metric April 2007
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
Uijterwaal Expires October 19, 2007 [Page 3]
Internet-Draft Packet Duplication Metric April 2007
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).
Uijterwaal Expires October 19, 2007 [Page 4]
Internet-Draft Packet Duplication Metric April 2007
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]
Uijterwaal Expires October 19, 2007 [Page 5]
Internet-Draft Packet Duplication Metric April 2007
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
Uijterwaal Expires October 19, 2007 [Page 6]
Internet-Draft Packet Duplication Metric April 2007
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.
Uijterwaal Expires October 19, 2007 [Page 7]
Internet-Draft Packet Duplication Metric April 2007
Author's Address
Henk Uijterwaal
RIPE NCC
Singel 258
1016 AB Amsterdam
The Netherlands
Phone: +31 20 535 4444
Email: henk@ripe.net
Uijterwaal Expires October 19, 2007 [Page 8]
Internet-Draft Packet Duplication Metric April 2007
Full Copyright Statement
Copyright (C) The IETF Trust (2007).
This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors
retain all their rights.
This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Intellectual Property
The IETF takes no position regarding the validity or scope of any
Intellectual Property Rights or other rights that might be claimed to
pertain to the implementation or use of the technology described in
this document or the extent to which any license under such rights
might or might not be available; nor does it represent that it has
made any independent effort to identify any such rights. Information
on the procedures with respect to rights in RFC documents can be
found in BCP 78 and BCP 79.
Copies of IPR disclosures made to the IETF Secretariat and any
assurances of licenses to be made available, or the result of an
attempt made to obtain a general license or permission for the use of
such proprietary rights by implementers or users of this
specification can be obtained from the IETF on-line IPR repository at
http://www.ietf.org/ipr.
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at
ietf-ipr@ietf.org.
Acknowledgment
Funding for the RFC Editor function is provided by the IETF
Administrative Support Activity (IASA).
Uijterwaal Expires October 19, 2007 [Page 9]
