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 | |||
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