draft-ietf-ippm-loss-episode-metrics-03.txt   draft-ietf-ippm-loss-episode-metrics-04.txt 
Network Working Group N. Duffield Network Working Group N. Duffield
Internet-Draft AT&T Labs-Research Internet-Draft AT&T Labs-Research
Intended status: Standards Track A. Morton Intended status: Standards Track A. Morton
Expires: April 29, 2012 AT&T Labs Expires: July 20, 2012 AT&T Labs
J. Sommers J. Sommers
Colgate University Colgate University
October 27, 2011 January 17, 2012
Loss Episode Metrics for IPPM Loss Episode Metrics for IPPM
draft-ietf-ippm-loss-episode-metrics-03 draft-ietf-ippm-loss-episode-metrics-04
Abstract Abstract
The IETF has developed a one way packet loss metric that measures the The IETF has developed a one way packet loss metric that measures the
loss rate on a Poisson probe stream between two hosts. However, the loss rate on a Poisson probe stream between two hosts. However, the
impact of packet loss on applications is in general sensitive not impact of packet loss on applications is in general sensitive not
just to the average loss rate, but also to the way in which packet just to the average loss rate, but also to the way in which packet
losses are distributed in loss episodes (i.e., maximal sets of losses are distributed in loss episodes (i.e., maximal sets of
consecutively lost probe packets). This draft defines one-way packet consecutively lost probe packets). This document defines one-way
loss episode metrics, specifically the frequency and average duration packet loss episode metrics, specifically the frequency and average
of loss episodes, and a probing methodology under which the loss duration of loss episodes, and a probing methodology under which the
episode metrics are to be measured. loss episode metrics are to be measured.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119] document are to be interpreted as described in RFC 2119 [RFC2119]
Status of this Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
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Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 29, 2012. This Internet-Draft will expire on July 20, 2012.
Copyright Notice Copyright Notice
Copyright (c) 2011 IETF Trust and the persons identified as the Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Provisions Relating to IETF Documents Provisions Relating to IETF Documents
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the Trust Legal Provisions and are provided without warranty as the Trust Legal Provisions and are provided without warranty as
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6. Loss Episode Metrics derived from Bi-Packet Loss Probing . . . 14 6. Loss Episode Metrics derived from Bi-Packet Loss Probing . . . 14
6.1. Geometric Stream: Loss Ratio . . . . . . . . . . . . . . . 15 6.1. Geometric Stream: Loss Ratio . . . . . . . . . . . . . . . 15
6.1.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 15 6.1.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 15
6.1.2. Metric Parameters . . . . . . . . . . . . . . . . . . 15 6.1.2. Metric Parameters . . . . . . . . . . . . . . . . . . 15
6.1.3. Metric Units . . . . . . . . . . . . . . . . . . . . . 16 6.1.3. Metric Units . . . . . . . . . . . . . . . . . . . . . 16
6.1.4. Metric Definition . . . . . . . . . . . . . . . . . . 16 6.1.4. Metric Definition . . . . . . . . . . . . . . . . . . 16
6.1.5. Discussion . . . . . . . . . . . . . . . . . . . . . . 16 6.1.5. Discussion . . . . . . . . . . . . . . . . . . . . . . 16
6.1.6. Methodologies . . . . . . . . . . . . . . . . . . . . 16 6.1.6. Methodologies . . . . . . . . . . . . . . . . . . . . 16
6.1.7. Errors and Uncertainties . . . . . . . . . . . . . . . 16 6.1.7. Errors and Uncertainties . . . . . . . . . . . . . . . 16
6.1.8. Reporting the Metric . . . . . . . . . . . . . . . . . 16 6.1.8. Reporting the Metric . . . . . . . . . . . . . . . . . 16
6.2. Geometric Steam: Loss Episode Duration . . . . . . . . . . 16 6.2. Geometric Stream: Loss Episode Duration . . . . . . . . . 16
6.2.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 16 6.2.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 16
6.2.2. Metric Parameters . . . . . . . . . . . . . . . . . . 16 6.2.2. Metric Parameters . . . . . . . . . . . . . . . . . . 16
6.2.3. Metric Units . . . . . . . . . . . . . . . . . . . . . 17 6.2.3. Metric Units . . . . . . . . . . . . . . . . . . . . . 17
6.2.4. Metric Definition . . . . . . . . . . . . . . . . . . 17 6.2.4. Metric Definition . . . . . . . . . . . . . . . . . . 17
6.2.5. Discussion . . . . . . . . . . . . . . . . . . . . . . 17 6.2.5. Discussion . . . . . . . . . . . . . . . . . . . . . . 17
6.2.6. Methodologies . . . . . . . . . . . . . . . . . . . . 17 6.2.6. Methodologies . . . . . . . . . . . . . . . . . . . . 17
6.2.7. Errors and Uncertainties . . . . . . . . . . . . . . . 17 6.2.7. Errors and Uncertainties . . . . . . . . . . . . . . . 17
6.2.8. Reporting the Metric . . . . . . . . . . . . . . . . . 18 6.2.8. Reporting the Metric . . . . . . . . . . . . . . . . . 18
6.3. Geometric Stream: Loss Episode Frequency . . . . . . . . . 18 6.3. Geometric Stream: Loss Episode Frequency . . . . . . . . . 18
6.3.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 18 6.3.1. Metric Name . . . . . . . . . . . . . . . . . . . . . 18
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6.3.8. Reporting the Metric . . . . . . . . . . . . . . . . . 19 6.3.8. Reporting the Metric . . . . . . . . . . . . . . . . . 19
7. Applicability of Loss Episode Metrics . . . . . . . . . . . . 19 7. Applicability of Loss Episode Metrics . . . . . . . . . . . . 19
7.1. Relation to Gilbert Model . . . . . . . . . . . . . . . . 19 7.1. Relation to Gilbert Model . . . . . . . . . . . . . . . . 19
8. IPR Considerations . . . . . . . . . . . . . . . . . . . . . . 20 8. IPR Considerations . . . . . . . . . . . . . . . . . . . . . . 20
9. Security Considerations . . . . . . . . . . . . . . . . . . . 20 9. Security Considerations . . . . . . . . . . . . . . . . . . . 20
10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21 12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
12.1. Normative References . . . . . . . . . . . . . . . . . . . 21 12.1. Normative References . . . . . . . . . . . . . . . . . . . 21
12.2. Informative References . . . . . . . . . . . . . . . . . . 21 12.2. Informative References . . . . . . . . . . . . . . . . . . 21
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
1.1. Background and Motivation 1.1. Background and Motivation
Packet loss in the Internet is a complex phenomenon due to the bursty Packet loss in the Internet is a complex phenomenon due to the bursty
nature of traffic and congestion processes, influenced by both end- nature of traffic and congestion processes, influenced by both end-
users and applications, and the operation of transport protocols such users and applications, and the operation of transport protocols such
as TCP. For these reasons, the simplest model of packet loss--the as TCP. For these reasons, the simplest model of packet loss--the
single parameter Bernoulli (independent) loss model--does not single parameter Bernoulli (independent) loss model--does not
represent the complexity of packet loss over periods of time. represent the complexity of packet loss over periods of time.
Correspondingly, a single loss metric--the average packet loss ratio Correspondingly, a single loss metric--the average packet loss ratio
over some period of time--arising, e.g., from a stream of Poisson over some period of time--arising, e.g., from a stream of Poisson
probes as in [RFC2680] is not sufficient to determine the effect of probes as in [RFC2680] is not sufficient to determine the effect of
packet loss on traffic in general. packet loss on traffic in general.
Moving beyond single parameter loss models, Markovian and Markov- Moving beyond single parameter loss models, Markovian and Markov-
modulated loss models involving transitions between a good and bad modulated loss models involving transitions between a good and bad
state, each with an associated loss rate, have been proposed by state, each with an associated loss rate, have been proposed by
Gilbert and more generally by Elliot. In principle, Markovian models Gilbert [Gilbert] and more generally by Elliot [Elliot]. In
can be formulated over state spaces involving patterns of loss of any principle, Markovian models can be formulated over state spaces
desired number of packets. However further increase in the size of involving patterns of loss of any desired number of packets. However
the state space makes such models cumbersome both for parameter further increase in the size of the state space makes such models
estimation (accuracy decreases) and prediction in practice (due to cumbersome both for parameter estimation (accuracy decreases) and
computational complexity and sensitivity to parameter inaccuracy). prediction in practice (due to computational complexity and
In general, the relevance and importance of particular models can sensitivity to parameter inaccuracy). In general, the relevance and
change in time, e.g. in response to the advent of new applications importance of particular models can change in time, e.g. in response
and services. For this reason we are drawn to empirical metrics that to the advent of new applications and services. For this reason we
do not depend on a particular model for their interpretation. are drawn to empirical metrics that do not depend on a particular
model for their interpretation.
An empirical measure of packet loss complexity, the index of An empirical measure of packet loss complexity, the index of
dispersion of counts (IDC), comprise, for each t >0, the ratio v(t) \ dispersion of counts (IDC), comprise, for each t >0, the ratio v(t) /
a(t) of the variance v(t) and average a(t) of the number of losses a(t) of the variance v(t) and average a(t) of the number of losses
over successive measurement windows of a duration t. However, a full over successive measurement windows of a duration t. However, a full
characterization of packet loss over time requires specification of characterization of packet loss over time requires specification of
the IDC for each window size t>0. the IDC for each window size t>0.
In the standards arena, loss pattern sample metrics are defined in In the standards arena, loss pattern sample metrics are defined in
[RFC3357]. Following the Gilbert-Elliot model, burst metrics [RFC3357]. Following the Gilbert-Elliot model, burst metrics
specific for VoIP that characterize complete episodes of lost, specific for VoIP that characterize complete episodes of lost,
transmitted and discarded packets are defined in [RFC3611] transmitted and discarded packets are defined in [RFC3611]
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packet loss ratio, which can be recovered from the loss episode packet loss ratio, which can be recovered from the loss episode
metrics upon dividing the average loss episode duration by the metrics upon dividing the average loss episode duration by the
loss episode frequency. loss episode frequency.
3. the metrics provide the smallest possible increment in complexity 3. the metrics provide the smallest possible increment in complexity
beyond, but in the spirit of, the IPPM average packet loss ratio beyond, but in the spirit of, the IPPM average packet loss ratio
metrics [RFC2680] i.e., moving from a single metric (average metrics [RFC2680] i.e., moving from a single metric (average
packet loss ratio) to a pair of metrics (loss episode frequency packet loss ratio) to a pair of metrics (loss episode frequency
and average loss episode duration). and average loss episode duration).
The draft also describes a probing methodology under which loss The document also describes a probing methodology under which loss
episode metrics are to be measured. The methodology comprises episode metrics are to be measured. The methodology comprises
sending probe packets in pairs, where packets within each probe pair sending probe packets in pairs, where packets within each probe pair
have a fixed separation, and the time between pairs takes the form of have a fixed separation, and the time between pairs takes the form of
a geometric distributed number multiplied by the same separation. a geometric distributed number multiplied by the same separation.
This can be regarded a generalization of Poisson probing where the This can be regarded a generalization of Poisson probing where the
probes are pairs rather than single packets as in [RFC2680], and also probes are pairs rather than single packets as in [RFC2680], and also
of geometric probing described in [RFC2330]. However, it should be of geometric probing described in [RFC2330]. However, it should be
distinguished from back to back packet pairs whose change in distinguished from back to back packet pairs whose change in
separation on traversing a link is used to probe bandwidth. In this separation on traversing a link is used to probe bandwidth. In this
draft, the separation between the packets in a pair is the temporal document, the separation between the packets in a pair is the
resolution at which different loss episodes are to be distinguished. temporal resolution at which different loss episodes are to be
One key feature of this methodology is its efficiency: it estimates distinguished. The methodology does not measure episodes of loss of
the average length of loss episodes without directly measuring the consecutive background packets on the measured path. One key feature
complete episodes themselves. Instead, this information is encoded of this methodology is its efficiency: it estimates the average
in the observed relative frequencies of the 4 possible outcomes length of loss episodes without directly measuring the complete
arising from the loss or successful transmission of each of the two episodes themselves. Instead, this information is encoded in the
packets of the probe pairs. This is distinct from the approach of observed relative frequencies of the 4 possible outcomes arising from
[RFC3611] that reports on directly measured episodes. the loss or successful transmission of each of the two packets of the
probe pairs. This is distinct from the approach of [RFC3611] that
reports on directly measured episodes.
The metrics defined in this memo are "derived metrics", according to The metrics defined in this memo are "derived metrics", according to
Section 6.1 of [RFC2330] the IPPM framework. They are based on the Section 6.1 of [RFC2330] the IPPM framework. They are based on the
singleton loss metric defined in Section 2 of [RFC2680] . singleton loss metric defined in Section 2 of [RFC2680] .
1.3. Outline and Contents 1.3. Outline and Contents
o Section 2 defines the fundamental singleton metric for the o Section 2 defines the fundamental singleton metric for the
possible outcomes of a probe pair: Type-P-One-way-Bi-Packet-Loss. possible outcomes of a probe pair: Type-P-One-way-Bi-Packet-Loss.
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value 0 or 1, where 0 signifies successful transmission of a packet value 0 or 1, where 0 signifies successful transmission of a packet
and 1 signifies loss. and 1 signifies loss.
The metric unit of Type-P-One-way-Bi-Packet-Loss is a Loss Pair. The metric unit of Type-P-One-way-Bi-Packet-Loss is a Loss Pair.
2.4. Metric Definition 2.4. Metric Definition
1. "The Type-P-One-way-Bi-Packet-Loss with parameters (Src, Dst, T1, 1. "The Type-P-One-way-Bi-Packet-Loss with parameters (Src, Dst, T1,
T2, F, P) is (1,1)" means that Src sent the first bit of a Type-P T2, F, P) is (1,1)" means that Src sent the first bit of a Type-P
packet to Dst at wire-time T1 and the first bit of a Type-P packet to Dst at wire-time T1 and the first bit of a Type-P
packet to Dst a wire-time T2>T1, and that neither packet was packet to Dst at wire-time T2>T1, and that neither packet was
received at Dst. received at Dst.
2. The Type-P-One-way-Bi-Packet-Loss with parameters (Src, Dst, T1, 2. The Type-P-One-way-Bi-Packet-Loss with parameters (Src, Dst, T1,
T2, F, P) is (1,0)" means that Src sent the first bit of a Type-P T2, F, P) is (1,0)" means that Src sent the first bit of a Type-P
packet to Dst at wire-time T1 and the first bit of a Type-P packet to Dst at wire-time T1 and the first bit of a Type-P
packet to Dst a wire-time T2>T1, and that the first packet was packet to Dst at wire-time T2>T1, and that the first packet was
not received at Dst, and the second packet was received at Dst not received at Dst, and the second packet was received at Dst
3. The Type-P-One-way-Bi-Packet-Loss with parameters (Src, Dst, T1, 3. The Type-P-One-way-Bi-Packet-Loss with parameters (Src, Dst, T1,
T2, F, P) is (0,1)" means that Src sent the first bit of a Type-P T2, F, P) is (0,1)" means that Src sent the first bit of a Type-P
packet to Dst at wire-time T1 and the first bit of a Type-P packet to Dst at wire-time T1 and the first bit of a Type-P
packet to Dst a wire-time T2>T1, and that the first packet was packet to Dst at wire-time T2>T1, and that the first packet was
received at Dst, and the second packet was not received at Dst received at Dst, and the second packet was not received at Dst
4. The Type-P-One-way-Bi-Packet-Loss with parameters (Src, Dst, T1, 4. The Type-P-One-way-Bi-Packet-Loss with parameters (Src, Dst, T1,
T2, F, P) is (0,0)" means that Src sent the first bit of a Type-P T2, F, P) is (0,0)" means that Src sent the first bit of a Type-P
packet to Dst at wire-time T1 and the first bit of a Type-P packet to Dst at wire-time T1 and the first bit of a Type-P
packet to Dst a wire-time T2>T1, and that both packet were packet to Dst at wire-time T2>T1, and that both packets were
received at Dst. received at Dst.
2.5. Discussion 2.5. Discussion
The purpose of the selection function is to specify exactly which The purpose of the selection function is to specify exactly which
packets are to be used for measurement. The notion is taken from packets are to be used for measurement. The notion is taken from
Section 2.5 of [RFC3393], where examples are discussed. Section 2.5 of [RFC3393], where examples are discussed.
2.6. Methodologies 2.6. Methodologies
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with parameters (Src, Dst, Ti1, Ti2, Fi, P) where Fi is the with parameters (Src, Dst, Ti1, Ti2, Fi, P) where Fi is the
restriction of the selection function F to the packet pair at time restriction of the selection function F to the packet pair at time
Ti1, Ti2. Ti1, Ti2.
3.5. Discussion 3.5. Discussion
The metric definition of Type-P-One-way-Bi-Packet-Loss-Stream is The metric definition of Type-P-One-way-Bi-Packet-Loss-Stream is
sufficiently general to describe the case where packets are sampled sufficiently general to describe the case where packets are sampled
from a pre-existing stream. This is useful in the case that there is from a pre-existing stream. This is useful in the case that there is
a general purpose measurement stream setup between two hosts, and we a general purpose measurement stream setup between two hosts, and we
which to select a substream from it for the purposes of loss episode wish to select a substream from it for the purposes of loss episode
measurement. In the next section we specialize this somewhat to more measurement. Packet pairs selected as bi-packet loss probes need not
concretely describe a purpose built packet stream for loss episode be consecutive within such a stream. In the next section we
measurement. specialize this somewhat to more concretely describe a purpose built
packet stream for loss episode measurement.
3.6. Methodologies 3.6. Methodologies
The methodologies related to the Type-P-One-way-Packet-Loss metric in The methodologies related to the Type-P-One-way-Packet-Loss metric in
Section 2.6 of [RFC2680] are similar for the Type-P-One-way-Bi- Section 2.6 of [RFC2680] are similar for the Type-P-One-way-Bi-
Packet-Loss-Stream metric described above. In particular, the Packet-Loss-Stream metric described above. In particular, the
methodologies described in RFC 2680 apply to both packets of each methodologies described in RFC 2680 apply to both packets of each
pair. pair.
3.7. Errors and Uncertainties 3.7. Errors and Uncertainties
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o q, a launch probability o q, a launch probability
o F, a selection function defining unambiguously the two packets o F, a selection function defining unambiguously the two packets
from the stream selected for the metric. from the stream selected for the metric.
o P, the specification of the packet type, over and above the source o P, the specification of the packet type, over and above the source
and destination address and destination address
6.1.3. Metric Units 6.1.3. Metric Units
A number in the interval [0,1] A decimal number in the interval [0,1]
6.1.4. Metric Definition 6.1.4. Metric Definition
The result obtained by computing the Bi-Packet-Loss-Ratio over a The result obtained by computing the Bi-Packet-Loss-Ratio over a
Type-P-One-way-Bi-Packet-Loss-Geometric-Stream sample with the metric Type-P-One-way-Bi-Packet-Loss-Geometric-Stream sample with the metric
parameters. parameters.
6.1.5. Discussion 6.1.5. Discussion
Type-P-One-way-Bi-Packet-Loss-Geometric-Stream-Ratio estimates the Type-P-One-way-Bi-Packet-Loss-Geometric-Stream-Ratio estimates the
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corresponding idealized version corresponding to q = 1. Estimation corresponding idealized version corresponding to q = 1. Estimation
variance as it applies to Type-P-One-way-Bi-Packet-Loss-Geometric- variance as it applies to Type-P-One-way-Bi-Packet-Loss-Geometric-
Stream-Loss-Ratio is described in [SBDR08]. Stream-Loss-Ratio is described in [SBDR08].
For other issues refer to Section 4.7 For other issues refer to Section 4.7
6.1.8. Reporting the Metric 6.1.8. Reporting the Metric
Refer to Section 4.8 Refer to Section 4.8
6.2. Geometric Steam: Loss Episode Duration 6.2. Geometric Stream: Loss Episode Duration
6.2.1. Metric Name 6.2.1. Metric Name
Type-P-One-way-Bi-Packet-Loss-Geometric-Stream-Episode-Duration Type-P-One-way-Bi-Packet-Loss-Geometric-Stream-Episode-Duration
6.2.2. Metric Parameters 6.2.2. Metric Parameters
o Src, the IP address of a source host o Src, the IP address of a source host
o Dst, the IP address of a destination host o Dst, the IP address of a destination host
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independent parameters, the Markov transition probabilities P(g|b) = independent parameters, the Markov transition probabilities P(g|b) =
1- P(b|b) and P(b|g) = 1- P(g|g), where P(i|j) is the probability to 1- P(b|b) and P(b|g) = 1- P(g|g), where P(i|j) is the probability to
transition from state j and step n to state i at step n+1. With transition from state j and step n to state i at step n+1. With
these parameters, the fraction of steps spent in the bad state is these parameters, the fraction of steps spent in the bad state is
P(b|g)/(P(b|g) + P(g|b)) while the average duration of a sojourn in P(b|g)/(P(b|g) + P(g|b)) while the average duration of a sojourn in
the bad state is 1/P(g|b) steps. the bad state is 1/P(g|b) steps.
Now identify the steps of the Markov chain with the possible sending Now identify the steps of the Markov chain with the possible sending
times of packets for a Type-P-One-way-Bi-Packet-Loss-Geometric-Stream times of packets for a Type-P-One-way-Bi-Packet-Loss-Geometric-Stream
with launch spacing d. Suppose the loss episode metrics Type-P-One- with launch spacing d. Suppose the loss episode metrics Type-P-One-
way-Bi-Packet-Loss-Geometric-Stream-Ratio and ype-P-One-way-Bi- way-Bi-Packet-Loss-Geometric-Stream-Ratio and Type-P-One-way-Bi-
Packet-Loss-Geometric-Stream-Episode-Duration take the values r and m Packet-Loss-Geometric-Stream-Episode-Duration take the values r and m
respectively. Then from the discussion in Section 6.2.5 the respectively. Then from the discussion in Section 6.2.5 the
following can be equated: following can be equated:
r = P(b|g)/(P(b|g) + P(g|b)) and m/d = 1/P(g|b). r = P(b|g)/(P(b|g) + P(g|b)) and m/d = 1/P(g|b).
These relationships can be inverted in order to recover the Gilbert These relationships can be inverted in order to recover the Gilbert
model parameters: model parameters:
P(g|b) = d/m and P(b|g)=d/m/(1/r - 1) P(g|b) = d/m and P(b|g)=d/m/(1/r - 1)
8. IPR Considerations 8. IPR Considerations
An IPR disclosure concerning some of the material covered in this An IPR disclosure concerning some of the material covered in this
draft has been made to the IETF: see document has been made to the IETF: see
https://datatracker.ietf.org/ipr/1354/ https://datatracker.ietf.org/ipr/1354/
9. Security Considerations 9. Security Considerations
Conducting Internet measurements raises both security and privacy Conducting Internet measurements raises both security and privacy
concerns. This memo does not specify an implementation of the concerns. This memo does not specify an implementation of the
metrics, so it does not directly affect the security of the Internet metrics, so it does not directly affect the security of the Internet
nor of applications which run on the Internet. nor of applications which run on the Internet.
However,implementations of these metrics must be mindful of security However,implementations of these metrics must be mindful of security
and privacy concerns. and privacy concerns.
skipping to change at page 21, line 8 skipping to change at page 21, line 8
SHOULD include appropriate techniques to reduce the probability that SHOULD include appropriate techniques to reduce the probability that
measurement traffic can be distinguished from "normal" traffic. measurement traffic can be distinguished from "normal" traffic.
Authentication techniques, such as digital signatures, may be used Authentication techniques, such as digital signatures, may be used
where appropriate to guard against injected traffic attacks. The where appropriate to guard against injected traffic attacks. The
privacy concerns of network measurement are limited by the active privacy concerns of network measurement are limited by the active
measurements described in this memo: they involve no release of user measurements described in this memo: they involve no release of user
data. data.
10. IANA Considerations 10. IANA Considerations
This document requests no actions from IANA.
11. Acknowledgements 11. Acknowledgements
12. References 12. References
12.1. Normative References 12.1. Normative References
[RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way [RFC2680] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Packet Loss Metric for IPPM", RFC 2680, September 1999. Packet Loss Metric for IPPM", RFC 2680, September 1999.
[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation [RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
skipping to change at page 22, line 5 skipping to change at page 21, line 47
"Framework for IP Performance Metrics", RFC 2330, "Framework for IP Performance Metrics", RFC 2330,
May 1998. May 1998.
[RFC3357] Koodli, R. and R. Ravikanth, "One-way Loss Pattern Sample [RFC3357] Koodli, R. and R. Ravikanth, "One-way Loss Pattern Sample
Metrics", RFC 3357, August 2002. Metrics", RFC 3357, August 2002.
[SBDR08] IEEE/ACM Transactions on Networking, 16(2): 307-320, "A [SBDR08] IEEE/ACM Transactions on Networking, 16(2): 307-320, "A
Geometric Approach to Improving Active Packet Loss Geometric Approach to Improving Active Packet Loss
Measurement", 2008. Measurement", 2008.
[Gilbert] Gilbert, E.N., "Capacity of a Burst-Noise Channel. Bell
System Technical Journal 39 pp 1253-1265", 1960.
[Elliot] Elliott, E.O., "Estimates of Error Rates for Codes on
Burst-Noise Channels. Bell System Technical Journal 42 pp
1977-1997", 1963.
Authors' Addresses Authors' Addresses
Nick Duffield Nick Duffield
AT&T Labs-Research AT&T Labs-Research
180 Park Avenue 180 Park Avenue
Florham Park, NJ 07932 Florham Park, NJ 07932
USA USA
Phone: +1 973 360 8726 Phone: +1 973 360 8726
Fax: +1 973 360 8871 Fax: +1 973 360 8871
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