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
	skipping to change at page 1, line 47		skipping to change at page 1, line 47
	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.
	This document is subject to BCP 78 and the IETF Trust's Legal		This document is subject to BCP 78 and the IETF Trust's Legal
	Provisions Relating to IETF Documents		Provisions Relating to IETF Documents
	(http://trustee.ietf.org/license-info) in effect on the date of		(http://trustee.ietf.org/license-info) in effect on the date of
	publication of this document. Please review these documents		publication of this document. Please review these documents
	carefully, as they describe your rights and restrictions with respect		carefully, as they describe your rights and restrictions with respect
	to this document. Code Components extracted from this document must		to this document. Code Components extracted from this document must
	include Simplified BSD License text as described in Section 4.e of		include Simplified BSD License text as described in Section 4.e of
	the Trust Legal Provisions and are provided without warranty as		the Trust Legal Provisions and are provided without warranty as
	skipping to change at page 4, line 5		skipping to change at page 4, line 5
	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
	skipping to change at page 4, line 32		skipping to change at page 4, line 32
	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]
	skipping to change at page 6, line 44		skipping to change at page 6, line 44
	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.
	skipping to change at page 8, line 43		skipping to change at page 8, line 43
	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
	skipping to change at page 10, line 42		skipping to change at page 10, line 42
	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
	skipping to change at page 16, line 10		skipping to change at page 16, line 10
	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
	skipping to change at page 16, line 43		skipping to change at page 16, line 43
	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
	skipping to change at page 19, line 50		skipping to change at page 19, line 50
	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
End of changes. 23 change blocks.
	44 lines changed or deleted		57 lines changed or added
This html diff was produced by rfcdiff 1.41. The latest version is available from http://tools.ietf.org/tools/rfcdiff/