draft-ietf-ippm-multimetrics-12.txt   rfc5644.txt 
Network Working Group E. Stephan Network Working Group E. Stephan
Internet-Draft France Telecom Request for Comments: 5644 France Telecom
Intended status: Standards Track L. Liang Category: Standards Track L. Liang
Expires: March 5, 2010 University of Surrey University of Surrey
A. Morton A. Morton
AT&T Labs AT&T Labs
September 1, 2009 October 2009
IP Performance Metrics (IPPM) for spatial and multicast
draft-ietf-ippm-multimetrics-12
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79. This document may contain material
from IETF Documents or IETF Contributions published or made publicly
available before November 10, 2008. The person(s) controlling the
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Trust the right to allow modifications of such material outside the
IETF Standards Process. Without obtaining an adequate license from
the person(s) controlling the copyright in such materials, this
document may not be modified outside the IETF Standards Process, and
derivative works of it may not be created outside the IETF Standards
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Internet-Drafts are working documents of the Internet Engineering IP Performance Metrics (IPPM): Spatial and Multicast
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
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Internet-Drafts are draft documents valid for a maximum of six months Abstract
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The IETF has standardized IP Performance Metrics (IPPM) for measuring
http://www.ietf.org/ietf/1id-abstracts.txt. end-to-end performance between two points. This memo defines two new
categories of metrics that extend the coverage to multiple
measurement points. It defines spatial metrics for measuring the
performance of segments of a source to destination path, and metrics
for measuring the performance between a source and many destinations
in multiparty communications (e.g., a multicast tree).
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This Internet-Draft will expire on March 5, 2010. This document specifies an Internet standards track protocol for the
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improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
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The IETF has standardized IP Performance Metrics (IPPM) for measuring This document may contain material from IETF Documents or IETF
end-to-end performance between two points. This memo defines two new Contributions published or made publicly available before November
categories of metrics that extend the coverage to multiple 10, 2008. The person(s) controlling the copyright in some of this
measurement points. It defines spatial metrics for measuring the material may not have granted the IETF Trust the right to allow
performance of segments of a source to destination path, and metrics
for measuring the performance between a source and many destinations
in multiparty communications (e.g., a multicast tree).
Requirements Language RFC 5644 Spatial and Multicast Metrics October 2009
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", modifications of such material outside the IETF Standards Process.
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this Without obtaining an adequate license from the person(s) controlling
document are to be interpreted as described in RFC 2119 [RFC2119]. the copyright in such materials, this document may not be modified
outside the IETF Standards Process, and derivative works of it may
not be created outside the IETF Standards Process, except to format
it for publication as an RFC or to translate it into languages other
than English.
Table of Contents Table of Contents
1. Introduction and Scope . . . . . . . . . . . . . . . . . . . . 4 1. Introduction and Scope ..........................................3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology .....................................................4
3. Brief Metric Descriptions . . . . . . . . . . . . . . . . . . 8 3. Brief Metric Descriptions .......................................7
4. Motivations . . . . . . . . . . . . . . . . . . . . . . . . . 10 4. Motivations ....................................................10
5. Spatial vector metrics definitions . . . . . . . . . . . . . . 12 5. Spatial Vector Metrics Definitions .............................12
6. Spatial Segment Metrics Definitions . . . . . . . . . . . . . 19 6. Spatial Segment Metrics Definitions ............................19
7. One-to-group metrics definitions . . . . . . . . . . . . . . . 24 7. One-to-Group Metrics Definitions ...............................27
8. One-to-group Sample Statistics . . . . . . . . . . . . . . . . 28 8. One-to-Group Sample Statistics .................................30
9. Measurement Methods: Scalability and Reporting . . . . . . . . 37 9. Measurement Methods: Scalability and Reporting .................40
10. Manageability Considerations . . . . . . . . . . . . . . . . . 41 10. Manageability Considerations ..................................44
11. Security Considerations . . . . . . . . . . . . . . . . . . . 45 11. Security Considerations .......................................49
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 47 12. Acknowledgments ...............................................50
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 47 13. IANA Considerations ...........................................50
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 51 14. References ....................................................56
14.1. Normative References . . . . . . . . . . . . . . . . . . 51 14.1. Normative References .....................................56
14.2. Informative References . . . . . . . . . . . . . . . . . 52 14.2. Informative References ...................................57
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 52
RFC 5644 Spatial and Multicast Metrics October 2009
1. Introduction and Scope 1. Introduction and Scope
IETF has standardized IP Performance Metrics (IPPM) for measuring IETF has standardized IP Performance Metrics (IPPM) for measuring
end-to-end performance between two points. This memo defines two new end-to-end performance between two points. This memo defines two new
categories of metrics that extend the coverage to multiple categories of metrics that extend the coverage to multiple
measurement points. It defines spatial metrics for measuring the measurement points. It defines spatial metrics for measuring the
performance of segments of a source to destination path, and metrics performance of segments of a source to destination path, and metrics
for measuring the performance between a source and many destinations for measuring the performance between a source and many destinations
in multiparty communications (e.g., a multicast tree). in multiparty communications (e.g., a multicast tree).
The purpose of the memo is to define metrics to fulfill the new The purpose of this memo is to define metrics to fulfill the new
requirements of measurement involving multiple measurement points. requirements of measurement involving multiple measurement points.
Spatial metrics measure the performance of each segment along a path. Spatial metrics measure the performance of each segment along a path.
One-to-group metrics measure the performance for a group of users. One-to-group metrics measure the performance for a group of users.
These metrics are derived from one-way end-to-end metrics, all of These metrics are derived from one-way end-to-end metrics, all of
which follow the IPPM framework [RFC2330]. which follow the IPPM framework [RFC2330].
This memo is organized as follows: Section 2 introduces new terms This memo is organized as follows: Section 2 introduces new terms
that extend the original IPPM framework [RFC2330]. Section 3 that extend the original IPPM framework [RFC2330]. Section 3 briefly
motivates each metric category and briefly introduces the new introduces the new metrics, and Section 4 motivates each metric
metrics. Sections 4 through 7 develop each category of metrics with category. Sections 5 through 8 develop each category of metrics with
definitions and statistics. Then the memo discusses the impact of definitions and statistics. Then the memo discusses the impact of
the measurement methods on the scalability and proposes an the measurement methods on the scalability and proposes an
information model for reporting the measurements. Finally, the memo information model for reporting the measurements. Finally, the memo
discusses security aspects related to measurement and registers the discusses security aspects related to measurement and registers the
metrics in the IANA IP Performance Metrics Registry [RFC4148]. metrics in the IANA IP Performance Metrics Registry [RFC4148].
The scope of this memo is limited to metrics using a single source The scope of this memo is limited to metrics using a single source
packet or stream, and observations of corresponding packets along the packet or stream, and observations of corresponding packets along the
path (spatial), at one or more destinations (one-to-group), or both. path (spatial), at one or more destinations (one-to-group), or both.
Note that all the metrics defined herein are based on observations of Note that all the metrics defined herein are based on observations of
packets dedicated to testing, a process which is called active packets dedicated to testing, a process that is called active
measurement. Passive measurement (for example, a spatial metric measurement. Passive measurement (for example, a spatial metric
based on the observation of user traffic) is beyond the scope of this based on the observation of user traffic) is beyond the scope of this
memo. memo.
1.1. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
RFC 5644 Spatial and Multicast Metrics October 2009
2. Terminology 2. Terminology
2.1. Naming of the metrics 2.1. Naming of the Metrics
The names of the metrics, including capitalization letters, are as The names of the metrics, including capitalized letters, are as close
close as possible of the names of the one-way end-to-end metrics they as possible of the names of the one-way end-to-end metrics they are
are derived from. derived from.
2.2. Terms Defined Elsewhere 2.2. Terms Defined Elsewhere
host: section 5 of RFC 2330 host: section 5 of RFC 2330
router: section 5 of RFC 2330 router: section 5 of RFC 2330
loss threshold: section 2.8.2 of RFC 2680 loss threshold: section 2.8.2 of RFC 2680
path: section 5 of RFC 2330 path: section 5 of RFC 2330
sample: section 11 of RFC 2330 sample: section 11 of RFC 2330
singleton: section 11 of RFC 2330 singleton: section 11 of RFC 2330
2.3. Routers Digest 2.3. Routers Digest
The list of the routers on the path from the source to the The list of the routers on the path from the source to the
destination which act as points of interest, also referred to as the destination that act as points of interest, also referred to as the
routers digest. routers digest.
2.4. Multiparty metric 2.4. Multiparty Metric
A metric is said to be multiparty if the topology involves more than A metric is said to be multiparty if the topology involves more than
one measurement collection point. All multiparty metrics designate a one measurement collection point. All multiparty metrics designate a
set of hosts as "points of interest", where one host is the source set of hosts as "points of interest", where one host is the source
and other hosts are the measurement collection points. For example, and other hosts are the measurement collection points. For example,
if the set of points of interest is < ha, hb, hc, ..., hn >, where ha if the set of points of interest is < ha, hb, hc, ..., hn >, where ha
is the source and < hb, hc, ..., hn > are the destinations, then is the source and < hb, hc, ..., hn > are the destinations, then
measurements may be conducted between < ha, hb>, < ha, hc>, ..., <ha, measurements may be conducted between < ha, hb>, < ha, hc>, ..., <ha,
hn >. hn >.
For the purposes of this memo (reflecting the scope of a single For the purposes of this memo (reflecting the scope of a single
source), the only multiparty metrics are one-to-group metrics. source), the only multiparty metrics are one-to-group metrics.
2.5. Spatial metric 2.5. Spatial Metric
A metric is said to be spatial if one of the hosts (measurement A metric is said to be spatial if one of the hosts (measurement
collection points) involved is neither the source nor a destination collection points) involved is neither the source nor a destination
of the measured packet(s). Such measurement hosts will usually be of the measured packet(s). Such measurement hosts will usually be
routers member of the routers digest. routers that are members of the routers digest.
2.6. One-to-group metric RFC 5644 Spatial and Multicast Metrics October 2009
2.6. One-to-Group Metric
A metric is said to be one-to-group if the measured packet is sent by A metric is said to be one-to-group if the measured packet is sent by
one source and (potentially) received by more than one destination. one source and (potentially) received by more than one destination.
Thus, the topology of the communication group can be viewed as a Thus, the topology of the communication group can be viewed as a
center-distributed or server-client topology with the source as the center-distributed or server-client topology with the source as the
center/server in the topology. center/server in the topology.
2.7. Points of interest 2.7. Points of Interest
Points of interest are the hosts (as per the RFC 2330 definition, Points of interest are the hosts (as per the RFC 2330 definition,
"hosts" include routing nodes) that are measurement collection "hosts" include routing nodes) that are measurement collection
points, a sub-set of the set of hosts involved in the delivery of the points, which are a sub-set of the set of hosts involved in the
packets (in addition to the source itself). delivery of the packets (in addition to the source itself).
For spatial metrics, points of interest are a (possibly arbitrary) For spatial metrics, points of interest are a (possibly arbitrary)
sub-set of all the routers involved in the path. sub-set of all the routers involved in the path.
Points of interest of one-to-group metrics are the intended Points of interest of one-to-group metrics are the intended
destination hosts for packets from the source (in addition to the destination hosts for packets from the source (in addition to the
source itself). source itself).
Src Dst Src Dst
`. ,-. `. ,-.
skipping to change at page 6, line 32 skipping to change at page 5, line 42
`. ; : `. ; :
`. ; : `. ; :
; :... 2 ; :... 2
| | | |
: ; : ;
: ;.... 3 : ;.... 3
: ; : ;
`. ,' `. ,'
`-'....... I `-'....... I
Figure 1: One-to-group points of interest Figure 1: One-to-Group Points of Interest
A candidate point of interest for spatial metrics is a router from A candidate point of interest for spatial metrics is a router from
the set of routers involved in the delivery of the packets from the set of routers involved in the delivery of the packets from
source to destination. source to destination.
Src ------. Hosts RFC 5644 Spatial and Multicast Metrics October 2009
\
`---X --- 1 Src ------. Hosts
\ \
x `---X --- 1
/ \
.---------X ---- 2 x
/ /
x .---------X ---- 2
... /
`---X ---- ... x
\ ...
`---X ---- ...
\ \
\ \
X ---- J \
\ X ---- J
\ \
\ \
`---- Dst \
`---- Dst
Note: 'X' are nodes which are points of interest, Note: 'X' are nodes that are points of interest,
'x' are nodes which are not points of interest 'x' are nodes that are not points of interest
Figure 2: Spatial points of interest Figure 2: Spatial Points of Interest
2.8. Reference point 2.8. Reference Point
A reference point is defined as the server where the statistical A reference point is defined as the server where the statistical
calculations will be carried out. It is usually a centralized server calculations will be carried out. It is usually a centralized server
in the measurement architecture that is controlled by a network in the measurement architecture that is controlled by a network
operator, where measurement data can be collected for further operator, where measurement data can be collected for further
processing. The reference point is distinctly different from hosts processing. The reference point is distinctly different from hosts
at measurement collection points, where the actual measurements are at measurement collection points, where the actual measurements are
carried out (e.g., points of interest). carried out (e.g., points of interest).
2.9. Vector 2.9. Vector
A vector is a set of singletons (single atomic results) comprised of A vector is a set of singletons (single atomic results) comprised of
observations corresponding to a single source packet at different observations corresponding to a single source packet at different
hosts in a network. For instance, if the one-way delay singletons hosts in a network. For instance, if the one-way delay singletons
observed at N receivers for Packet P sent by the source Src are dT1, observed at N receivers for Packet P sent by the source Src are dT1,
dT2,..., dTN, then a vector V with N elements can be organized as dT2,..., dTN, then a vector V with N elements can be organized as
{dT1, dT2,..., dTN}. The element dT1 is distinct from all others as {dT1, dT2,..., dTN}. The element dT1 is distinct from all others as
the singleton at receiver 1 in response to a packet sent from the the singleton at receiver 1 in response to a packet sent from the
source at a specific time. The complete vector gives information source at a specific time. The complete vector gives information
over the dimension of space; a set of N receivers in this example. over the dimension of space, a set of N receivers in this example.
RFC 5644 Spatial and Multicast Metrics October 2009
The singleton elements of any vector are distinctly different from The singleton elements of any vector are distinctly different from
each other in terms of their measurement collection point. Different each other in terms of their measurement collection point. Different
vectors for common measurement points of interest are distinguished vectors for common measurement points of interest are distinguished
by the source packet sending time. by the source packet sending time.
2.10. Matrix 2.10. Matrix
Several vectors form a matrix, which contains results observed over a Several vectors form a matrix, which contains results observed over a
sampling interval at different places in a network at different sampling interval at different places in a network at different
times. For example, the One-way delay vectors V1={dT11, dT12,..., times. For example, the one-way delay vectors V1={dT11, dT12,...,
dT1N}, V2={dT21, dT22,..., dT2N},..., Vm={dTm1, dTm2,..., dTmN} for dT1N}, V2={dT21, dT22,..., dT2N},..., Vm={dTm1, dTm2,..., dTmN} for
Packet P1, P2,...,Pm, form a One-way delay Matrix {V1, V2,...,Vm}. Packet P1, P2,...,Pm, form a one-way delay Matrix {V1, V2,...,Vm}.
The matrix organizes the vector information to present network The matrix organizes the vector information to present network
performance in both space and time. performance in both space and time.
A one-dimensional matrix (row) corresponds to a sample in simple A one-dimensional matrix (row) corresponds to a sample in simple
point-to-point measurement. point-to-point measurement.
The relationship among singleton, sample, vector and matrix is The relationship among singleton, sample, vector, and matrix is
illustrated in the following Figure 3. illustrated in Figure 3.
points of singleton points of singleton
interest / samples(time) interest / samples(time)
,----. ^ / ,----. ^ /
/ R1.....| / R1dT1 R1dT2 R1dT3 ... R3dTk \ / R1.....| / R1dT1 R1dT2 R1dT3 ... R3dTk \
/ \ | | | / \ | | |
; R2........| | R2dT1 R2dT2 R2dT3 ... R3dTk | ; R2........| | R2dT1 R2dT2 R2dT3 ... R3dTk |
Src | || | | Src | || | |
| R3....| | R3dT1 R3dT2 R3dT3 ... R3dTk | | R3....| | R3dT1 R3dT2 R3dT3 ... R3dTk |
| || | | | || | |
: ;| | | : ;| | |
\ / | | | \ / | | |
\ Rn......| \ RndT1 RndT2 RndT3 ... RndTk / \ Rn......| \ RndT1 RndT2 RndT3 ... RndTk /
`-----' +-------------------------------------> time `-----' +-------------------------------------> time
vector matrix vector matrix
(space) (time and space) (space) (time and space)
Figure 3: Relationship between singletons, samples, vectors and Figure 3: Relationship between Singletons, Samples, Vectors, and
matrix Matrix
3. Brief Metric Descriptions 3. Brief Metric Descriptions
The metrics for spatial and one-to-group measurement are based on the The metrics for spatial and one-to-group measurement are based on the
source-to-destination, or end-to-end metrics defined by IETF in source-to-destination, or end-to-end metrics defined by IETF in
[RFC2679], [RFC2680], [RFC3393], [RFC3432]. [RFC2679], [RFC2680], [RFC3393], and [RFC3432].
RFC 5644 Spatial and Multicast Metrics October 2009
This memo defines seven new spatial metrics using the [RFC2330] This memo defines seven new spatial metrics using the [RFC2330]
framework of parameters, units of measure, and measurement framework of parameters, units of measure, and measurement
methodologies. Each definition includes a section that describes methodologies. Each definition includes a section that describes
measurements constraints and issues, and provides guidance to measurement constraints and issues, and provides guidance to increase
increase the accuracy of the results. the accuracy of the results.
The spatial metrics are: The spatial metrics are:
o Type-P-Spatial-One-way-Delay-Vector divides the end-to-end Type-P- o Type-P-Spatial-One-way-Delay-Vector divides the end-to-end Type-P-
One-way-Delay [RFC2679] into a spatial vector of one-way delay One-way-Delay [RFC2679] into a spatial vector of one-way delay
singletons. singletons.
o Type-P-Spatial-One-way-Packet-Loss-Vector divides an end-to-end o Type-P-Spatial-One-way-Packet-Loss-Vector divides an end-to-end
Type-P-One-way-Packet-Loss [RFC2680] into a spatial vector of Type-P-One-way-Packet-Loss [RFC2680] into a spatial vector of
packet loss singletons. packet loss singletons.
o Type-P-Spatial-One-way-ipdv-Vector divides an end-to-end Type-P- o Type-P-Spatial-One-way-ipdv-Vector divides an end-to-end Type-P-
One-way-ipdv into a spatial vector of ipdv (IP Packet Delay One-way-ipdv into a spatial vector of ipdv (IP Packet Delay
Variation) singletons. Variation) singletons.
o Using elements of the Type-P-Spatial-One-way-Delay-Vector metric, o Using elements of the Type-P-Spatial-One-way-Delay-Vector metric,
a sample called Type-P-Segment-One-way-Delay-Stream collects one- a sample called Type-P-Segment-One-way-Delay-Stream collects one-
way delay metrics between two points of interest on the path over way delay metrics between two points of interest on the path over
time. time.
o Likewise, using elements of the Type-P-Spatial-Packet-Loss-Vector o Likewise, using elements of the Type-P-Spatial-Packet-Loss-Vector
metric, a sample called Type-P-Segment-Packet-Loss-Stream collects metric, a sample called Type-P-Segment-Packet-Loss-Stream collects
one-way delay metrics between two points of interest on the path one-way delay metrics between two points of interest on the path
over time. over time.
o Using the Type-P-Spatial-One-way-Delay-Vector metric, a sample o Using the Type-P-Spatial-One-way-Delay-Vector metric, a sample
called Type-P-Segment-ipdv-prev-Stream, will be introduced to called Type-P-Segment-ipdv-prev-Stream will be introduced to
compute ipdv metrics (using the previous packet selection compute ipdv metrics (using the previous packet selection
function) between two points of interest on the path over time. function) between two points of interest on the path over time.
o Again using the Type-P-Spatial-One-way-Delay-Vector metric, a o Again using the Type-P-Spatial-One-way-Delay-Vector metric, a
sample called Type-P-Segment-ipdv-min-Stream will define another sample called Type-P-Segment-ipdv-min-Stream will define another
set of ipdv metrics (using the minimum delay packet selection set of ipdv metrics (using the minimum delay packet selection
function) between two points of interest on the path over time. function) between two points of interest on the path over time.
The memo also defines three one-to-group metrics to measure the one- The memo also defines three one-to-group metrics to measure the one-
way performance between a source and a group of receivers. They are: way performance between a source and a group of receivers. They are:
o Type-P-One-to-group-Delay-Vector collects the set of Type-P-one-
way-delay singletons between one sender and N receivers. o Type-P-One-to-group-Delay-Vector which collects the set of Type-P-
o Type-P-One-to-group-Packet-Loss-Vector collects the set of Type-P- One-way-Delay singletons between one sender and N receivers;
One-way-Packet-Loss singletons between one sender and N receivers.
o Type-P-One-to-group-ipdv-Vector collects the set of Type-P-One- RFC 5644 Spatial and Multicast Metrics October 2009
way-ipdv singletons between one sender and N receivers.
o Type-P-One-to-group-Packet-Loss-Vector which collects the set of
Type-P-One-way-Packet-Loss singletons between one sender and N
receivers; and
o Type-P-One-to-group-ipdv-Vector which collects the set of Type-P-
One-way-ipdv singletons between one sender and N receivers.
Finally, based on the one-to-group vector metrics listed above, Finally, based on the one-to-group vector metrics listed above,
statistics are defined to capture single receiver performance, group statistics are defined to capture single receiver performance, group
performance and the relative performance for a multiparty performance, and the relative performance for a multiparty
communication: communication:
o Using the Type-P-One-to-group-Delay-Vector, a metric called Type- o Using the Type-P-One-to-group-Delay-Vector, a metric called Type-
P-One-to-group-Receiver-n-Mean-Delay or RnMD, presents the mean of P-One-to-group-Receiver-n-Mean-Delay, or RnMD, presents the mean
delays between one sender and a single receiver 'n'. From this of delays between one sender and a single receiver 'n'. From this
metric, 3 additional metrics are defined to characterize the mean metric, three additional metrics are defined to characterize the
delay over the entire group of receivers during the same time mean delay over the entire group of receivers during the same time
interval: interval:
* Type-P-One-to-group-Mean-Delay or GMD, presents the mean of
* Type-P-One-to-group-Mean-Delay, or GMD, presents the mean of
delays; delays;
* Type-P-One-to-group-Range-Mean-Delay or GRMD, presents the
range of mean delays; * Type-P-One-to-group-Range-Mean-Delay, or GRMD, presents the
* Type-P-One-to-group-Max-Mean-Delay or GMMD, presents the range of mean delays; and
* Type-P-One-to-group-Max-Mean-Delay, or GMMD, presents the
maximum of mean delays. maximum of mean delays.
o Using the Type-P-One-to-group-Packet-Loss-Vector, a metric called o Using the Type-P-One-to-group-Packet-Loss-Vector, a metric called
Type-P-One-to-group-Receiver-n-Loss-Ratio or RnLR, captures the Type-P-One-to-group-Receiver-n-Loss-Ratio, or RnLR, captures the
packet loss ratio between one sender and a single receiver 'n'. packet loss ratio between one sender and a single receiver 'n'.
Based on this definition, 2 more metrics are defined to Based on this definition, two more metrics are defined to
characterize packet loss over the entire group during the same characterize packet loss over the entire group during the same
time interval: time interval:
* Type-P-One-to-group-Loss-Ratio or GLR, captures the overall
packet loss ratio for the entire group of receivers; * Type-P-One-to-group-Loss-Ratio, or GLR, captures the overall
packet loss ratio for the entire group of receivers; and
* Type-P-One-to-group-Range-Loss-Ratio, or GRLR, presents the * Type-P-One-to-group-Range-Loss-Ratio, or GRLR, presents the
comparative packet loss ratio during the test interval between comparative packet loss ratio during the test interval between
one sender and N receivers. one sender and N receivers.
o Using the Type-P-One-to-group-Packet-Loss-Vector, a metric called o Using the Type-P-One-to-group-Packet-Loss-Vector, a metric called
Type-P-One-to-group-Receiver-n-Comp-Loss-Ratio, or RnCLR, computes Type-P-One-to-group-Receiver-n-Comp-Loss-Ratio, or RnCLR, computes
a packet loss ratio using the maximum number of packets received a packet loss ratio using the maximum number of packets received
at any receiver. at any receiver.
RFC 5644 Spatial and Multicast Metrics October 2009
o Using Type-P-One-to-group-ipdv-Vector, a metric called Type-P-One- o Using Type-P-One-to-group-ipdv-Vector, a metric called Type-P-One-
to-group-Range-Delay-Variation, or GRDV, presents the range of to-group-Range-Delay-Variation, or GRDV, presents the range of
delay variation between one sender and a group of receivers. delay variation between one sender and a group of receivers.
4. Motivations 4. Motivations
All existing IPPM metrics are defined for end-to-end (source to All existing IPPM metrics are defined for end-to-end (source-to-
destination) measurement of point-to-point paths. It is logical to destination) measurement of point-to-point paths. It is logical to
extend them to multiparty situations such as one to one trajectory extend them to multiparty situations such as one-to-one trajectory
metrics and one to multipoint metrics. metrics and one-to-multipoint metrics.
4.1. Motivations for spatial metrics 4.1. Motivations for Spatial Metrics
Spatial metrics are needed for: Spatial metrics are needed for:
o Decomposing the performance of an inter-domain path to quantify o Decomposing the performance of an inter-domain path to quantify
the per-AS contribution to the end-to-end performance. the per-AS (Autonomous System) contribution to the end-to-end
performance.
o Traffic engineering and troubleshooting, which benefit from o Traffic engineering and troubleshooting, which benefit from
spatial views of one-way delay and ipdv consumption, or spatial views of one-way delay and ipdv consumption, or
identification of the path segment where packets were lost. identification of the path segment where packets were lost.
o Monitoring the decomposed performance of a multicast tree based on o Monitoring the decomposed performance of a multicast tree based on
MPLS point-to-multipoint communications. MPLS point-to-multipoint communications.
o Dividing end-to-end metrics, so that some segment measurements can o Dividing end-to-end metrics, so that some segment measurements can
be re-used and help measurement systems reach large-scale be re-used and help measurement systems reach large-scale
coverage. Spatial measures could characterize the performance of coverage. Spatial measures could characterize the performance of
an intra-domain segment and provide an elementary piece of an intra-domain segment and provide an elementary piece of
information needed to estimate inter-domain performance to another information needed to estimate inter-domain performance to another
destination using Spatial Composition metrics destination using Spatial Composition metrics [SPATIAL].
[I-D.ietf-ippm-spatial-composition].
4.2. Motivations for One-to-group metrics 4.2. Motivations for One-to-group Metrics
While the node-to-node based spatial measures can provide very useful While the node-to-node-based spatial measures can provide very useful
data in the view of each connection, we also need measures to present data in the view of each connection, we also need measures to present
the performance of a multiparty communication topology. A simple the performance of a multiparty communication topology. A simple
point-to-point metric cannot completely describe the multiparty point-to-point metric cannot completely describe the multiparty
situation. New one-to-group metrics assess performance of the situation. New one-to-group metrics assess performance of the
multiple paths for further statistical analysis. The new metrics are multiple paths for further statistical analysis. The new metrics are
named one-to-group performance metrics, and they are based on the named one-to-group performance metrics, and they are based on the
unicast metrics defined in IPPM RFCs. One-to-group metrics are one- unicast metrics defined in IPPM RFCs. One-to-group metrics are one-
way metrics from one source to a group of destinations, or receivers. way metrics from one source to a group of destinations or receivers.
The metrics are helpful for judging the overall performance of a The metrics are helpful for judging the overall performance of a
multiparty communications network, and for describing the performance multiparty communications network and for describing the performance
variation across a group of destinations. variation across a group of destinations.
RFC 5644 Spatial and Multicast Metrics October 2009
One-to-group performance metrics are needed for: One-to-group performance metrics are needed for:
o Designing and engineering multicast trees and MPLS point-to- o Designing and engineering multicast trees and MPLS point-to-
multipoint LSPs. multipoint Label Switched Paths (LSPs).
o Evaluating and controlling the quality of multicast services, o Evaluating and controlling the quality of multicast services,
including inter-domain multicast. including inter-domain multicast.
o Presenting and evaluating the performance requirements for o Presenting and evaluating the performance requirements for
multiparty communications and overlay multicast. multiparty communications and overlay multicast.
To understand the packet transfer performance between one source and To understand the packet transfer performance between one source and
any one receiver in the multiparty communication group, we need to any one receiver in the multiparty communication group, we need to
collect instantaneous end-to-end metrics, or singletons. This gives collect instantaneous end-to-end metrics, or singletons. This gives
a very detailed view into the performance of each branch of the a very detailed view into the performance of each branch of the
multicast tree, and can provide clear and helpful information for multicast tree, and can provide clear and helpful information for
engineers to identify the branch with problems in a complex engineers to identify the branch with problems in a complex
multiparty routing tree. multiparty routing tree.
The one-to-group metrics described in this memo introduce the The one-to-group metrics described in this memo introduce the
multiparty topology into the IPPM framework, and describe the multiparty topology into the IPPM framework, and they describe the
performance delivered to a group receiving packets from the same performance delivered to a group receiving packets from the same
source. The concept extends the "path" of the point-to-point source. The concept extends the "path" of the point-to-point
measurement to "path tree" to cover one-to-many topologies. If measurement to "path tree" to cover one-to-many topologies. If
applied to one-to-one topology, the one-to-group metrics provide applied to one-to-one topology, the one-to-group metrics provide
exactly the same results as the corresponding one-to-one metrics. exactly the same results as the corresponding one-to-one metrics.
4.3. Discussion on Group-to-one and Group-to-group metrics 4.3. Discussion on Group-to-One and Group-to-Group Metrics
We note that points of interest can also be selected to define We note that points of interest can also be selected to define
measurements on group-to-one and group-to-group topologies. These measurements on group-to-one and group-to-group topologies. These
topologies are beyond the scope of this memo, because they would topologies are beyond the scope of this memo, because they would
involve multiple packets launched from different sources. However, involve multiple packets launched from different sources. However,
this section gives some insights on these two cases. this section gives some insights on these two cases.
The measurements for group-to-one topology can be easily derived from The measurements for group-to-one topology can be easily derived from
the one-to-group measurement. The measurement point is the host that the one-to-group measurement. The measurement point is the host that
is acting as a receiver while all other hosts act as sources in this is acting as a receiver while all other hosts act as sources in this
case. case.
The group-to-group communication topology has no obvious focal point: The group-to-group communication topology has no obvious focal point:
the sources and the measurement collection points can be anywhere. the sources and the measurement collection points can be anywhere.
However, it is possible to organize the problem by applying However, it is possible to organize the problem by applying
measurements in one-to-group or group-to-one topologies for each host measurements in one-to-group or group-to-one topologies for each host
in a uniform way (without taking account of how the real in a uniform way (without taking account of how the real
RFC 5644 Spatial and Multicast Metrics October 2009
communication might be carried out). For example, one group of hosts communication might be carried out). For example, one group of hosts
< ha, hb, hc, ..., hn > might act as sources to send data to another < ha, hb, hc, ..., hn > might act as sources to send data to another
group of hosts < Ha, Hb, Hc, ..., Hm >, and they can be organized group of hosts < Ha, Hb, Hc, ..., Hm >, and they can be organized
into n sets of points of interest for one-to-group communications: into n sets of points of interest for one-to-group communications:
< ha, Ha, Hb, Hc, ..., Hm >, < hb, Ha, Hb, Hc, ..., Hm >, <hc, Ha, < ha, Ha, Hb, Hc, ..., Hm >, < hb, Ha, Hb, Hc, ..., Hm >, <hc, Ha,
Hb, Hc, ..., Hm >, ..., < hn, Ha, Hb, Hc, ..., Hm >. Hb, Hc, ..., Hm >, ..., < hn, Ha, Hb, Hc, ..., Hm >.
5. Spatial vector metrics definitions 5. Spatial Vector Metrics Definitions
This section defines vectors for the spatial decomposition of end-to- This section defines vectors for the spatial decomposition of end-to-
end singleton metrics over a path. end singleton metrics over a path.
Spatial vector metrics are based on the decomposition of standard Spatial vector metrics are based on the decomposition of standard
end-to-end metrics defined by the IPPM WG in [RFC2679], [RFC2680], end-to-end metrics defined by the IPPM WG in [RFC2679], [RFC2680],
[RFC3393] and [RFC3432]. [RFC3393], and [RFC3432].
The spatial vector definitions are coupled with the corresponding The spatial vector definitions are coupled with the corresponding
end-to-end metrics. Measurement methodology aspects are common to end-to-end metrics. Measurement methodology aspects are common to
all the vectors defined and are consequently discussed in a common all the vectors defined and are consequently discussed in a common
section. section.
5.1. A Definition for Spatial One-way Delay Vector 5.1. A Definition for Spatial One-Way Delay Vector
This section is coupled with the definition of Type-P-One-way-Delay This section is coupled with the definition of Type-P-One-way-Delay
of the section 3 of [RFC2679]. When a parameter from the definition in section 3 of [RFC2679]. When a parameter from the definition in
in [RFC2679] is re-used in this section, the first instance will be [RFC2679] is re-used in this section, the first instance will be
tagged with a trailing asterisk. tagged with a trailing asterisk.
Sections 3.5 to 3.8 of [RFC2679] give requirements and applicability Sections 3.5 to 3.8 of [RFC2679] give requirements and applicability
statements for end-to-end one-way-delay measurements. They are statements for end-to-end one-way delay measurements. They are
applicable to each point of interest, Hi, involved in the measure. applicable to each point of interest, Hi, involved in the measure.
Spatial one-way-delay measurement MUST respect them, especially those Spatial one-way delay measurements MUST respect them, especially
related to methodology, clock, uncertainties and reporting. those related to methodology, clock, uncertainties, and reporting.
5.1.1. Metric Name 5.1.1. Metric Name
Type-P-Spatial-One-way-Delay-Vector Type-P-Spatial-One-way-Delay-Vector
5.1.2. Metric Parameters 5.1.2. Metric Parameters
o Src*, the IP address of the sender. o Src*, the IP address of the sender.
o Dst*, the IP address of the receiver. o Dst*, the IP address of the receiver.
o i, an integer in the ordered list <1,2,...,n> of routers in the o i, an integer in the ordered list <1,2,...,n> of routers in the
path. path.
RFC 5644 Spatial and Multicast Metrics October 2009
o Hi, a router of the routers digest. o Hi, a router of the routers digest.
o T*, a time, the sending (or initial observation) time for a o T*, a time, the sending (or initial observation) time for a
measured packet. measured packet.
o dT*, a delay, the one-way delay for a measured packet. o dT*, a delay, the one-way delay for a measured packet.
o dTi, a delay, the one-way delay for a measured packet from the o dTi, a delay, the one-way delay for a measured packet from the
source to router Hi. source to router Hi.
o <dT1,... dTi,... dTn> a list of n delay singletons. o <dT1,... dTi,... dTn> a list of n delay singletons.
o Type-P*, the specification of the packet type. o Type-P*, the specification of the packet type.
o <H1, H2,..., Hn> the routers digest. o <H1, H2,..., Hn> the routers digest.
5.1.3. Metric Units 5.1.3. Metric Units
The value of Type-P-Spatial-One-way-Delay-Vector is a sequence of The value of Type-P-Spatial-One-way-Delay-Vector is a sequence of
times (a real number in the dimension of seconds with sufficient times (a real number in the dimension of seconds with sufficient
resolution to convey the results). resolution to convey the results).
5.1.4. Definition 5.1.4. Definition
skipping to change at page 14, line 8 skipping to change at page 13, line 46
(last bit received) Hi, or undefined if the packet does not pass Hi (last bit received) Hi, or undefined if the packet does not pass Hi
within a specified loss threshold* time. within a specified loss threshold* time.
Type-P-Spatial-One-way-Delay-Vector metric is defined for the path Type-P-Spatial-One-way-Delay-Vector metric is defined for the path
<Src, H1, H2,..., Hn, Dst> as the sequence of values <Src, H1, H2,..., Hn, Dst> as the sequence of values
<T,dT1,dT2,...,dTn,dT>. <T,dT1,dT2,...,dTn,dT>.
5.1.5. Discussion 5.1.5. Discussion
Some specific issues that may occur are as follows: Some specific issues that may occur are as follows:
o the delay singletons "appear" to decrease: dTi > dTi+1. This may o the delay singletons "appear" to decrease: dTi > dTi+1. This may
occur despite being physically impossible with the definition occur despite being physically impossible with the definition
used. used.
RFC 5644 Spatial and Multicast Metrics October 2009
* This is frequently due to a measurement clock synchronization * This is frequently due to a measurement clock synchronization
issue. This point is discussed in the section 3.7.1. "Errors issue. This point is discussed in section 3.7.1 "Errors or
or uncertainties related to Clocks" of [RFC2679]. uncertainties related to Clocks" of [RFC2679]. Consequently,
Consequently, the values of delays measured at multiple routers the values of delays measured at multiple routers may not match
may not match the order of those routers on the path. the order of those routers on the path.
* The actual order of routers on the path may change due to * The actual order of routers on the path may change due to
reconvergence (e.g., recovery from a link failure). reconvergence (e.g., recovery from a link failure).
* The location of the measurement collection point in the device * The location of the measurement collection point in the device
influences the result. If the packet is not observed directly influences the result. If the packet is not observed directly
on the input interface the delay includes buffering time and on the input interface, the delay includes buffering time and
consequently an uncertainty due to the difference between 'wire consequently an uncertainty due to the difference between
time' and 'host time'. 'wire-time' and 'host time'.
5.2. A Definition for Spatial Packet Loss Vector 5.2. A Definition for Spatial Packet Loss Vector
This section is coupled with the definition of Type-P-One-way-Packet- This section is coupled with the definition of Type-P-One-way-Packet-
Loss. When a parameter from section 2 of [RFC2680] is used in this Loss. When a parameter from section 2 of [RFC2680] is used in this
section, the first instance will be tagged with a trailing asterisk. section, the first instance will be tagged with a trailing asterisk.
Sections 2.5 to 2.8 of [RFC2680] give requirements and applicability Sections 2.5 to 2.8 of [RFC2680] give requirements and applicability
statements for end-to-end one-way packet loss measurements. They are statements for end-to-end one-way packet loss measurements. They are
applicable to each point of interest, Hi, involved in the measure. applicable to each point of interest, Hi, involved in the measure.
Spatial packet loss measurement MUST respect them, especially those Spatial packet loss measurement MUST respect them, especially those
related to methodology, clock, uncertainties and reporting. related to methodology, clock, uncertainties, and reporting.
The following sections define the spatial loss vector, adapt some of The following sections define the spatial loss vector, adapt some of
the points above, and introduce points specific to spatial loss the points above, and introduce points specific to spatial loss
measurement. measurement.
5.2.1. Metric Name 5.2.1. Metric Name
Type-P-Spatial-Packet-Loss-Vector Type-P-Spatial-Packet-Loss-Vector
5.2.2. Metric Parameters 5.2.2. Metric Parameters
skipping to change at page 14, line 47 skipping to change at page 14, line 45
the points above, and introduce points specific to spatial loss the points above, and introduce points specific to spatial loss
measurement. measurement.
5.2.1. Metric Name 5.2.1. Metric Name
Type-P-Spatial-Packet-Loss-Vector Type-P-Spatial-Packet-Loss-Vector
5.2.2. Metric Parameters 5.2.2. Metric Parameters
o Src*, the IP address of the sender. o Src*, the IP address of the sender.
o Dst*, the IP address of the receiver. o Dst*, the IP address of the receiver.
o i, an integer in the ordered list <1,2,...,n> of routers in the o i, an integer in the ordered list <1,2,...,n> of routers in the
path. path.
o Hi, a router of the routers digest. o Hi, a router of the routers digest.
o T*, a time, the sending time for a measured packet. o T*, a time, the sending time for a measured packet.
RFC 5644 Spatial and Multicast Metrics October 2009
o dTi, a delay, the one-way delay for a measured packet from the o dTi, a delay, the one-way delay for a measured packet from the
source to host Hi. source to host Hi.
o <dT1,..., dTn>, list of n delay singletons. o <dT1,..., dTn>, list of n delay singletons.
o Type-P*, the specification of packet type. o Type-P*, the specification of packet type.
o <H1, H2,..., Hn>, the routers digest. o <H1, H2,..., Hn>, the routers digest.
o <L1, L2, ...,Ln>, a list of Boolean values. o <L1, L2, ...,Ln>, a list of Boolean values.
5.2.3. Metric Units 5.2.3. Metric Units
The value of Type-P-Spatial-Packet-Loss-Vector is a sequence of The value of Type-P-Spatial-Packet-Loss-Vector is a sequence of
Boolean values. Boolean values.
5.2.4. Definition 5.2.4. Definition
Given a Type-P packet sent by the Src at time T to the receiver Dst Given a Type-P packet sent by the Src at time T to the receiver Dst
skipping to change at page 15, line 31 skipping to change at page 15, line 36
on the path <H1, H2, ..., Hn>. For the sequence of times <T+dT1,T+ on the path <H1, H2, ..., Hn>. For the sequence of times <T+dT1,T+
dT2,..., T+dTi, ...,T+dTn> the packet passes in <H1, H2, ..., Hi, dT2,..., T+dTi, ...,T+dTn> the packet passes in <H1, H2, ..., Hi,
..., Hn>, define the Type-P-Packet-Loss-Vector metric as the sequence ..., Hn>, define the Type-P-Packet-Loss-Vector metric as the sequence
of values <T, L1, L2, ..., Ln> such that for each Hi of the path, a of values <T, L1, L2, ..., Ln> such that for each Hi of the path, a
value of 0 for Li means that dTi is a finite value, and a value of 1 value of 0 for Li means that dTi is a finite value, and a value of 1
means that dTi is undefined. means that dTi is undefined.
5.2.5. Discussion 5.2.5. Discussion
Some specific issues that may occur are as follows: Some specific issues that may occur are as follows:
o The result might include the sequence of values 1,0. Although o The result might include the sequence of values 1,0. Although
this appears physically impossible (a packet is lost, then re- this appears physically impossible (a packet is lost, then re-
appears later on the path): appears later on the path):
* The actual routers on the path may change due to reconvergence * The actual routers on the path may change due to reconvergence
(e.g., recovery from a link failure). (e.g., recovery from a link failure).
* The order of routers on the path may change due to * The order of routers on the path may change due to
reconvergence. reconvergence.
* A packet may not be observed in a router due to some buffer or * A packet may not be observed in a router due to some buffer or
CPU overflow at the measurement collection point. CPU overflow at the measurement collection point.
5.3. A Definition for Spatial One-way Ipdv Vector 5.3. A Definition for Spatial One-Way ipdv Vector
When a parameter from section 2 of [RFC3393] (the definition of Type- When a parameter from section 2 of [RFC3393] (the definition of Type-
P-One-way-ipdv) is used in this section, the first instance will be P-One-way-ipdv) is used in this section, the first instance will be
tagged with a trailing asterisk. tagged with a trailing asterisk.
RFC 5644 Spatial and Multicast Metrics October 2009
The following sections define the spatial ipdv vector, adapt some of The following sections define the spatial ipdv vector, adapt some of
the points above, and introduce points specific to spatial ipdv the points above, and introduce points specific to spatial ipdv
measurement. measurement.
5.3.1. Metric Name 5.3.1. Metric Name
Type-P-Spatial-One-way-ipdv-Vector Type-P-Spatial-One-way-ipdv-Vector
5.3.2. Metric Parameters 5.3.2. Metric Parameters
skipping to change at page 16, line 12 skipping to change at page 16, line 18
the points above, and introduce points specific to spatial ipdv the points above, and introduce points specific to spatial ipdv
measurement. measurement.
5.3.1. Metric Name 5.3.1. Metric Name
Type-P-Spatial-One-way-ipdv-Vector Type-P-Spatial-One-way-ipdv-Vector
5.3.2. Metric Parameters 5.3.2. Metric Parameters
o Src*, the IP address of the sender. o Src*, the IP address of the sender.
o Dst*, the IP address of the receiver. o Dst*, the IP address of the receiver.
o i, an integer in the ordered list <1,2,...,n> of routers in the o i, an integer in the ordered list <1,2,...,n> of routers in the
path. path.
o Hi, a router of the routers digest. o Hi, a router of the routers digest.
o T1*, a time, the sending time for a first measured packet. o T1*, a time, the sending time for a first measured packet.
o T2*, a time, the sending time for a second measured packet. o T2*, a time, the sending time for a second measured packet.
o dT*, a delay, the one-way delay for a measured packet. o dT*, a delay, the one-way delay for a measured packet.
o dTi, a delay, the one-way delay for a measured packet from the o dTi, a delay, the one-way delay for a measured packet from the
source to router Hi. source to router Hi.
o Type-P*, the specification of the packets type.
o Type-P*, the specification of the packet type.
o P1, the first packet sent at time T1. o P1, the first packet sent at time T1.
o P2, the second packet sent at time T2. o P2, the second packet sent at time T2.
o <H1, H2,..., Hn>, the routers digest. o <H1, H2,..., Hn>, the routers digest.
o <T1,dT1.1, dT1.2,..., dT1.n,dT1>, the Type-P-Spatial-One-way- o <T1,dT1.1, dT1.2,..., dT1.n,dT1>, the Type-P-Spatial-One-way-
Delay-Vector for packet sent at time T1. Delay-Vector for a packet sent at time T1.
o <T2,dT2.1, dT2.2,..., dT2.n,dT2>, the Type-P-Spatial-One-way- o <T2,dT2.1, dT2.2,..., dT2.n,dT2>, the Type-P-Spatial-One-way-
Delay-Vector for packet sent at time T2. Delay-Vector for a packet sent at time T2.
o L*, a packet length in bits. The packets of a Type P packet
o L*, a packet length in bits. The packets of a Type-P packet
stream from which the Type-P-Spatial-One-way-Delay-Vector metric stream from which the Type-P-Spatial-One-way-Delay-Vector metric
is taken MUST all be of the same length. is taken MUST all be of the same length.
RFC 5644 Spatial and Multicast Metrics October 2009
5.3.3. Metric Units 5.3.3. Metric Units
The value of Type-P-Spatial-One-way-ipdv-Vector is a sequence of The value of Type-P-Spatial-One-way-ipdv-Vector is a sequence of
times (a real number in the dimension of seconds with sufficient times (a real number in the dimension of seconds with sufficient
resolution to convey the results). resolution to convey the results).
5.3.4. Definition 5.3.4. Definition
Given P1 the Type-P packet sent by the sender Src at wire-time (first Given P1 the Type-P packet sent by the sender Src at wire-time (first
bit) T1 to the receiver Dst and <T1, dT1.1, dT1.2,..., dT1.n, dT1> bit) T1 to the receiver Dst. Given <T1, dT1.1, dT1.2,..., dT1.n, dT1>
its Type-P-Spatial-One-way-Delay-Vector over the sequence of routers the Type-P-Spatial-One-way-Delay-Vector of P1 over the sequence of
<H1, H2,..., Hn>. routers <H1, H2,..., Hn>.
Given P2 the Type-P packet sent by the sender Src at wire-time (first Given P2 the Type-P packet sent by the sender Src at wire-time (first
bit) T2 to the receiver Dst and <T2, dT2.1, dT2.2,..., dT2.n, dT2> bit) T2 to the receiver Dst. Given <T2, dT2.1, dT2.2,..., dT2.n, dT2>
its Type-P-Spatial-One-way-Delay-Vector over the same path. the Type-P-Spatial-One-way-Delay-Vector of P2 over the same path.
Type-P-Spatial-One-way-ipdv-Vector metric is defined as the sequence The Type-P-Spatial-One-way-ipdv-Vector metric is defined as the
of values <T1, T2, dT2.1-dT1.1, dT2.2-dT1.2 ,..., dT2.n-dT1.n, dT2- sequence of values <T1, T2, dT2.1-dT1.1, dT2.2-dT1.2 ,..., dT2.n-
dT1> such that for each Hi of the sequence of routers <H1, H2,..., dT1.n, dT2-dT1> such that for each Hi of the sequence of routers <H1,
Hn>, dT2.i-dT1.i is either a real number if the packets P1 and P2 H2,..., Hn>, dT2.i-dT1.i is either a real number if the packets P1
pass Hi at wire-time (last bit) dT1.i and dT2.i respectively, or and P2 pass Hi at wire-time (last bit) dT1.i and dT2.i respectively,
undefined if at least one of them never passes Hi (and the respective or undefined if at least one of them never passes Hi (and the
one-way delay is undefined). The T1,T2* pair indicates the inter- respective one-way delay is undefined). The T1,T2* pair indicates
packet emission interval and dT2-dT1 is ddT* the Type-P-One-way-ipdv. the inter-packet emission interval and dT2-dT1 is ddT* the Type-P-
One-way-ipdv.
5.4. Spatial Methodology 5.4. Spatial Methodology
The methodology, reporting specifications, and uncertainties The methodology, reporting specifications, and uncertainties
specified in section 3 of [RFC2679] apply to each point of interest specified in section 3 of [RFC2679] apply to each point of interest
(or measurement collection point), Hi, measuring an element of a (or measurement collection point), Hi, measuring an element of a
spatial delay vector. spatial delay vector.
Likewise, the methodology, reporting specifications, and Likewise, the methodology, reporting specifications, and
uncertainties specified in section 2 of [RFC2680] apply to each point uncertainties specified in section 2 of [RFC2680] apply to each point
of interest, Hi, measuring an element of a spatial packet loss of interest, Hi, measuring an element of a spatial packet loss
vector. vector.
Sections 3.5 to 3.7 of [RFC3393] give requirements and applicability Sections 3.5 to 3.7 of [RFC3393] give requirements and applicability
statements for end-to-end One-way ipdv measurements. They are statements for end-to-end One-way ipdv measurements. They are
applicable to each point of interest, Hi, involved in the measure. applicable to each point of interest, Hi, involved in the measure.
Spatial One-way ipdv measurement MUST respect the methodology, clock, Spatial One-way ipdv measurement MUST respect the methodology, clock,
uncertainties and reporting aspects given there. uncertainties, and reporting aspects given there.
RFC 5644 Spatial and Multicast Metrics October 2009
Generally, for a given Type-P packet of length L at a specific Hi, Generally, for a given Type-P packet of length L at a specific Hi,
the methodology for spatial vector metrics may proceed as follows: the methodology for spatial vector metrics may proceed as follows:
o At each Hi, points of interest/measurement collection points o At each Hi, points of interest/measurement collection points
prepare to capture the packet sent at time T, record a timestamp prepare to capture the packet sent at time T, record a timestamp
Ti', and determine the internal delay correction dTi' (See section Ti', and determine the internal delay correction dTi' (see section
3.7.1. "Errors or uncertainties related to Clocks" of [RFC2679]); 3.7.1. "Errors or uncertainties related to Clocks" of [RFC2679]);
o Each Hi extracts the path ordering information from the packet o Each Hi extracts the path ordering information from the packet
(e.g. time-to-live); (e.g., time-to-live (TTL));
o Each Hi computes the corrected wiretime from Src to Hi: Ti = Ti' -
dTi'. This arrival time is undefined if the packet is not o Each Hi computes the corrected wire-time from Src to Hi: Ti = Ti'
- dTi'. This arrival time is undefined if the packet is not
detected after the 'loss threshold' duration; detected after the 'loss threshold' duration;
o Each Hi extracts the timestamp T from the packet; o Each Hi extracts the timestamp T from the packet;
o Each Hi computes the one-way-delay from Src to Hi: dTi = Ti - T;
o Each Hi computes the one-way delay from Src to Hi: dTi = Ti - T;
o The reference point gathers the result of each Hi and arranges o The reference point gathers the result of each Hi and arranges
them according to the path ordering information received to build them according to the path ordering information received to build
the type-P spatial one-way vector (e.g. Type-P-Spatial-One-way- the Type-P spatial one-way vector (e.g., Type-P-Spatial-One-way-
Delay-Vector metric <T, dT1, dT2,..., dTn, dT>) over the path Delay-Vector metric <T, dT1, dT2,..., dTn, dT>) over the path
<Src, H1, H2,..., Hn, Dst> at time T. <Src, H1, H2,..., Hn, Dst> at time T.
5.4.1. Packet Loss Detection 5.4.1. Packet Loss Detection
In a pure end-to-end measurement, packet losses are detected by the In a pure end-to-end measurement, packet losses are detected by the
receiver only. A packet is lost when Type-P-One-way-Delay is receiver only. A packet is lost when Type-P-One-way-Delay is
undefined or very large (See section 2.4 ans 2.5 of [RFC2680] and undefined or very large (see sections 2.4 and 2.5 of [RFC2680] and
section 3.5 of [RFC2680]). A packet is deemed lost by the receiver section 3.5 of [RFC2680]). A packet is deemed lost by the receiver
after a duration which starts at the time the packet is sent. This after a duration that starts at the time the packet is sent. This
timeout value is chosen by a measurement process. It determines the timeout value is chosen by a measurement process. It determines the
threshold between recording a long packet transfer time as a finite threshold between recording a long packet transfer time as a finite
value or an undefined value. value or an undefined value.
In a spatial measurement, packet losses may be detected at several In a spatial measurement, packet losses may be detected at several
measurement collection points. Depending on the consistency of the measurement collection points. Depending on the consistency of the
packet loss detections among the points of interest, a packet may be packet loss detections among the points of interest, a packet may be
considered as lost at one point despite having a finite delay at considered as lost at one point despite having a finite delay at
another one, or may be observed by the last measurement collection another, or it may be observed by the last measurement collection
point of the path but considered lost by Dst. point of the path but considered lost by Dst.
There is a risk of misinterpreting such results: Has the path There is a risk of misinterpreting such results: has the path
changed? Did the packet arrive at the destination or was it lost on changed? Did the packet arrive at the destination or was it lost on
the very last link? the very last link?
The same concern applies to one-way-delay measures: a delay measured RFC 5644 Spatial and Multicast Metrics October 2009
The same concern applies to one-way delay measures: a delay measured
may be computed as infinite by one observation point but as a real may be computed as infinite by one observation point but as a real
value by another one, or may be measured as a real value by the last value by another one, or may be measured as a real value by the last
observation point of the path but designated as undefined by Dst. observation point of the path but designated as undefined by Dst.
The observation/measurement collection points and the destination The observation/measurement collection points and the destination
SHOULD use consistent methods to detect packets losses. The methods SHOULD use consistent methods to detect packets losses. The methods
and parameters must be systematically reported to permit careful and parameters must be systematically reported to permit careful
comparison and to avoid introducing any confounding factors in the comparison and to avoid introducing any confounding factors in the
analysis. analysis.
5.4.2. Routers Digest 5.4.2. Routers Digest
The methodology given above relies on knowing the order of the The methodology given above relies on knowing the order of the
router/measurement collection points on the path [RFC2330]. router/measurement collection points on the path [RFC2330].
Path instability might cause a test packet to be observed more than Path instability might cause a test packet to be observed more than
once by the same router, resulting in the repetition of one or more once by the same router, resulting in the repetition of one or more
routers in the routers digest. routers in the routers digest.
For example, repeated observations may occur during rerouting phases For example, repeated observations may occur during rerouting phases
which introduce temporary micro loops. During such an event the that introduce temporary micro loops. During such an event, the
routers digest for a packet crossing Ha and Hb may include the routers digest for a packet crossing Ha and Hb may include the
pattern <Hb, Ha, Hb, Ha, Hb> meaning that Ha ended the computation of pattern <Hb, Ha, Hb, Ha, Hb>, meaning that Ha ended the computation
the new path before Hb and that the initial path was from Ha to Hb of the new path before Hb and that the initial path was from Ha to
and that the new path is from Hb to Ha. Hb, and that the new path is from Hb to Ha.
Consequently, duplication of routers in the routers digest of a Consequently, duplication of routers in the routers digest of a
vector MUST be identified before computation of statistics to avoid vector MUST be identified before computation of statistics to avoid
producing corrupted information. producing corrupted information.
6. Spatial Segment Metrics Definitions 6. Spatial Segment Metrics Definitions
This section defines samples to measure the performance of a segment This section defines samples to measure the performance of a segment
of a path over time. The definitions rely on the matrix of the of a path over time. The definitions rely on the matrix of the
spatial vector metrics defined above. spatial vector metrics defined above.
Firstly this section defines a sample of one-way delay, Type-P- First, this section defines a sample of one-way delay, Type-P-
Segment-One-way-Delay-Stream, and a sample of packet loss, Type-P- Segment-One-way-Delay-Stream, and a sample of packet loss, Type-P-
segment-Packet-Loss-Stream. Segment-Packet-Loss-Stream.
Then it defines 2 different samples of ipdv: Type-P-Segment-ipdv- Then, it defines two different samples of ipdv: Type-P-Segment-ipdv-
prev-Stream uses the current and previous packets as the selection prev-Stream uses the current and previous packets as the selection
function, and Type-P-Segment-ipdv-min-Stream, uses the minimum delay function, and Type-P-Segment-ipdv-min-Stream uses the minimum delay
as one of the selected packets in every pair. as one of the selected packets in every pair.
6.1. A Definition of a Sample of One-way Delay of a Segment of the Path RFC 5644 Spatial and Multicast Metrics October 2009
This metric defines a sample of One-way delays over time between a 6.1. A Definition of a Sample of One-Way Delay of a Segment of the Path
This metric defines a sample of one-way delays over time between a
pair of routers on a path. Since it is very close semantically to pair of routers on a path. Since it is very close semantically to
the metric Type-P-One-way-Delay-Poisson-Stream defined in section 4 the metric Type-P-One-way-Delay-Poisson-Stream defined in section 4
of [RFC2679], sections 4.5 to 4.8 of [RFC2679] are integral parts of of [RFC2679], sections 4.5 to 4.8 of [RFC2679] are integral parts of
the definition text below. the definition text below.
6.1.1. Metric Name 6.1.1. Metric Name
Type-P-Segment-One-way-Delay-Stream Type-P-Segment-One-way-Delay-Stream
6.1.2. Metric Parameters 6.1.2. Metric Parameters
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of [RFC2679], sections 4.5 to 4.8 of [RFC2679] are integral parts of of [RFC2679], sections 4.5 to 4.8 of [RFC2679] are integral parts of
the definition text below. the definition text below.
6.1.1. Metric Name 6.1.1. Metric Name
Type-P-Segment-One-way-Delay-Stream Type-P-Segment-One-way-Delay-Stream
6.1.2. Metric Parameters 6.1.2. Metric Parameters
o Src, the IP address of the sender. o Src, the IP address of the sender.
o Dst, the IP address of the receiver. o Dst, the IP address of the receiver.
o Type-P, the specification of the packet type. o Type-P, the specification of the packet type.
o i, an integer in the ordered list <1,2,...,n> of routers in the o i, an integer in the ordered list <1,2,...,n> of routers in the
path. path.
o k, an integer which orders the packets sent.
o k, an integer that orders the packets sent.
o a and b, two integers where b > a. o a and b, two integers where b > a.
o Hi, a router of the routers digest. o Hi, a router of the routers digest.
o <H1,..., Ha, ..., Hb, ...., Hn>, the routers digest. o <H1,..., Ha, ..., Hb, ...., Hn>, the routers digest.
o <T1, T2, ..., Tm>, a list of times. o <T1, T2, ..., Tm>, a list of times.
6.1.3. Metric Units 6.1.3. Metric Units
The value of a Type-P-Segment-One-way-Delay-Stream is a pair of: The value of a Type-P-Segment-One-way-Delay-Stream is a pair of:
A list of times <T1, T2, ..., Tm>;
A list of times <T1, T2, ..., Tm>; and
A sequence of delays. A sequence of delays.
6.1.4. Definition 6.1.4. Definition
Given two routers, Ha and Hb, of the the path <H1, H2,..., Ha, ..., Given two routers, Ha and Hb, of the path <H1, H2,..., Ha, ..., Hb,
Hb, ..., Hn>, and the matrix of Type-P-Spatial-One-way-Delay-Vector ..., Hn>, and the matrix of Type-P-Spatial-One-way-Delay-Vector for
for the packets sent from Src to Dst at times <T1, T2, ..., Tm-1, Tm> the packets sent from Src to Dst at times <T1, T2, ..., Tm-1, Tm> :
:
RFC 5644 Spatial and Multicast Metrics October 2009
<T1, dT1.1, dT1.2, ..., dT1.a, ..., dT1.b,..., dT1.n, dT1>; <T1, dT1.1, dT1.2, ..., dT1.a, ..., dT1.b,..., dT1.n, dT1>;
<T2, dT2.1, dT2.2, ..., dT2.a, ..., dT2.b,..., dT2.n, dT2>; <T2, dT2.1, dT2.2, ..., dT2.a, ..., dT2.b,..., dT2.n, dT2>;
... ...
<Tm, dTm.1, dTm.2, ..., dTm.a, ..., dTm.b,..., dTm.n, dTm>. <Tm, dTm.1, dTm.2, ..., dTm.a, ..., dTm.b,..., dTm.n, dTm>.
We define the sample Type-P-segment-One-way-Delay-Stream as the We define the sample Type-P-Segment-One-way-Delay-Stream as the
sequence <dT1.ab, dT2.ab, ..., dTk.ab, ..., dTm.ab> such that for sequence <dT1.ab, dT2.ab, ..., dTk.ab, ..., dTm.ab> such that for
each time Tk, 'dTk.ab' is either the real number 'dTk.b - dTk.a' if each time Tk, 'dTk.ab' is either the real number 'dTk.b - dTk.a', if
the packet sent at time Tk passes Ha and Hb or undefined if this the packet sent at the time Tk passes Ha and Hb, or is undefined if
packet never passes Ha or (inclusive) never passes Hb. this packet never passes Ha or (inclusive) never passes Hb.
6.1.5. Discussion 6.1.5. Discussion
Some specific issues that may occur are as follows: Some specific issues that may occur are as follows:
o the delay singletons "appear" to decrease: dTi > DTi+1, and is o the delay singletons "appear" to decrease: dTi > DTi+1, and is
discussed in section 5.1.5. discussed in section 5.1.5.
* This could also occur when the clock resolution of one * This could also occur when the clock resolution of one
measurement collection point is larger than the minimum delay measurement collection point is larger than the minimum delay
of a path. For example, the minimum delay of a 500 km path of a path. For example, the minimum delay of a 500 km path
through optical fiber facilities is 2.5ms, but the measurement through optical fiber facilities is 2.5 ms, but the measurement
collection point has a clock resolution of 8ms. collection point has a clock resolution of 8 ms.
The metric SHALL be invalid for times < T1 , T2, ..., Tm-1, Tm> if The metric SHALL be invalid for times < T1 , T2, ..., Tm-1, Tm> if
the following conditions occur: the following conditions occur:
o Ha or Hb disappears from the path due to some routing change. o Ha or Hb disappears from the path due to some routing change.
o The order of Ha and Hb changes in the path. o The order of Ha and Hb changes in the path.
6.2. A Definition of a Sample of Packet Loss of a Segment of the Path 6.2. A Definition of a Sample of Packet Loss of a Segment of the Path
This metric defines a sample of packet loss over time between a pair This metric defines a sample of packet loss over time between a pair
of routers of a path. Since it is very close semantically to the of routers of a path. Since it is very close semantically to the
metric Type-P-Packet-loss-Stream defined in section 3 of [RFC2680], metric Type-P-Packet-loss-Stream defined in section 3 of [RFC2680],
sections 3.5 to 3.8 of [RFC2680] are integral parts of the definition sections 3.5 to 3.8 of [RFC2680] are integral parts of the definition
text below. text below.
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6.2. A Definition of a Sample of Packet Loss of a Segment of the Path 6.2. A Definition of a Sample of Packet Loss of a Segment of the Path
This metric defines a sample of packet loss over time between a pair This metric defines a sample of packet loss over time between a pair
of routers of a path. Since it is very close semantically to the of routers of a path. Since it is very close semantically to the
metric Type-P-Packet-loss-Stream defined in section 3 of [RFC2680], metric Type-P-Packet-loss-Stream defined in section 3 of [RFC2680],
sections 3.5 to 3.8 of [RFC2680] are integral parts of the definition sections 3.5 to 3.8 of [RFC2680] are integral parts of the definition
text below. text below.
6.2.1. Metric Name 6.2.1. Metric Name
Type-P-segment-Packet-Loss-Stream Type-P-Segment-Packet-Loss-Stream
RFC 5644 Spatial and Multicast Metrics October 2009
6.2.2. Metric Parameters 6.2.2. Metric Parameters
o Src, the IP address of the sender. o Src, the IP address of the sender.
o Dst, the IP address of the receiver. o Dst, the IP address of the receiver.
o Type-P, the specification of the packet type. o Type-P, the specification of the packet type.
o k, an integer which orders the packets sent.
o n, an integer which orders the routers on the path. o k, an integer that orders the packets sent.
o n, an integer that orders the routers on the path.
o a and b, two integers where b > a. o a and b, two integers where b > a.
o <H1, H2, ..., Ha, ..., Hb, ...,Hn>, the routers digest. o <H1, H2, ..., Ha, ..., Hb, ...,Hn>, the routers digest.
o Hi, a router of the routers digest. o Hi, a router of the routers digest.
o <T1, T2, ..., Tm>, a list of times. o <T1, T2, ..., Tm>, a list of times.
o <L1, L2, ..., Ln>, a list of Boolean values. o <L1, L2, ..., Ln>, a list of Boolean values.
6.2.3. Metric Units 6.2.3. Metric Units
The value of a Type-P-segment-Packet-Loss-Stream is a pair of: The value of a Type-P-Segment-Packet-Loss-Stream is a pair of:
A The list of times <T1, T2, ..., Tm>;
The list of times <T1, T2, ..., Tm>; and
A sequence of Boolean values. A sequence of Boolean values.
6.2.4. Definition 6.2.4. Definition
Given two routers, Ha and Hb, of the the path <H1, H2,..., Ha, ..., Given two routers, Ha and Hb, of the path <H1, H2,..., Ha, ..., Hb,
Hb, ..., Hn>, and the matrix of Type-P-Spatial-Packet-Loss-Vector for ..., Hn> and the matrix of Type-P-Spatial-Packet-Loss-Vector for the
the packets sent from Src to Dst at times <T1, T2, ..., Tm-1, Tm> : packets sent from Src to Dst at times <T1, T2, ..., Tm-1, Tm> :
<T1, L1.1, L1.2,..., L1.a, ..., L1.b, ..., L1.n, L>, <T1, L1.1, L1.2,..., L1.a, ..., L1.b, ..., L1.n, L>,
<T2, L2.1, L2.2,..., L2.a, ..., L2.b, ..., L2.n, L>, <T2, L2.1, L2.2,..., L2.a, ..., L2.b, ..., L2.n, L>,
..., ...,
<Tm, Lm.1, Lm.2,..., Lma, ..., Lm.b, ..., Lm.n, L>. <Tm, Lm.1, Lm.2,..., Lma, ..., Lm.b, ..., Lm.n, L>.
We define the value of the sample Type-P-segment-Packet-Loss-Stream We define the value of the sample Type-P-Segment-Packet-Loss-Stream
from Ha to Hb as the sequence of Booleans <L1.ab, L2.ab,..., Lk.ab, from Ha to Hb as the sequence of Booleans <L1.ab, L2.ab,..., Lk.ab,
..., Lm.ab> such that for each Tk: ..., Lm.ab> such that for each Tk:
RFC 5644 Spatial and Multicast Metrics October 2009
o A value of Lk of 0 means that Ha and Hb observed the packet sent o A value of Lk of 0 means that Ha and Hb observed the packet sent
at time Tk (both Lk.a and Lk.b have a value of 0). at time Tk (both Lk.a and Lk.b have a value of 0).
o A value of Lk of 1 means that Ha observed the packet sent at time o A value of Lk of 1 means that Ha observed the packet sent at time
Tk (Lk.a has a value of 0) and that Hb did not observe the packet Tk (Lk.a has a value of 0) and that Hb did not observe the packet
sent at time Tk (Lk.b has a value of 1). sent at time Tk (Lk.b has a value of 1).
o The value of Lk is undefined when neither Ha nor Hb observed the o The value of Lk is undefined when neither Ha nor Hb observed the
packet (both Lk.a and Lk.b have a value of 1). packet (both Lk.a and Lk.b have a value of 1).
6.2.5. Discussion 6.2.5. Discussion
Unlike Type-P-Packet-loss-Stream, Type-P-Segment-Packet-Loss-Stream Unlike Type-P-Packet-loss-Stream, Type-P-Segment-Packet-Loss-Stream
relies on the stability of the routers digest. The metric SHALL be relies on the stability of the routers digest. The metric SHALL be
invalid for times < T1 , T2, ..., Tm-1, Tm> if the following invalid for times < T1 , T2, ..., Tm-1, Tm> if the following
conditions occur: conditions occur:
o Ha or Hb disappears from the path due to some routing change. o Ha or Hb disappears from the path due to some routing change.
o The order of Ha and Hb changes in the path. o The order of Ha and Hb changes in the path.
o Lk.a or Lk.b is undefined. o Lk.a or Lk.b is undefined.
o Lk.a has the value 1 (not observed) and Lk.b has the value 0 o Lk.a has the value 1 (not observed) and Lk.b has the value 0
(observed); (observed).
o L has the value 0 (the packet was received by Dst) and Lk.ab has o L has the value 0 (the packet was received by Dst) and Lk.ab has
the value 1 (the packet was lost between Ha and Hb). the value 1 (the packet was lost between Ha and Hb).
6.3. A Definition of a Sample of ipdv of a Segment using the Previous 6.3. A Definition of a Sample of ipdv of a Segment Using the Previous
Packet Selection Function Packet Selection Function
This metric defines a sample of ipdv [RFC3393] over time between a This metric defines a sample of ipdv [RFC3393] over time between a
pair of routers using the previous packet as the selection function. pair of routers using the previous packet as the selection function.
6.3.1. Metric Name 6.3.1. Metric Name
Type-P-Segment-ipdv-prev-Stream Type-P-Segment-ipdv-prev-Stream
6.3.2. Metric Parameters 6.3.2. Metric Parameters
skipping to change at page 22, line 24 skipping to change at page 23, line 49
This metric defines a sample of ipdv [RFC3393] over time between a This metric defines a sample of ipdv [RFC3393] over time between a
pair of routers using the previous packet as the selection function. pair of routers using the previous packet as the selection function.
6.3.1. Metric Name 6.3.1. Metric Name
Type-P-Segment-ipdv-prev-Stream Type-P-Segment-ipdv-prev-Stream
6.3.2. Metric Parameters 6.3.2. Metric Parameters
o Src, the IP address of the sender. o Src, the IP address of the sender.
o Dst, the IP address of the receiver. o Dst, the IP address of the receiver.
o Type-P, the specification of the packet type. o Type-P, the specification of the packet type.
o k, an integer which orders the packets sent.
o n, an integer which orders the routers on the path. o k, an integer that orders the packets sent.
RFC 5644 Spatial and Multicast Metrics October 2009
o n, an integer that orders the routers on the path.
o a and b, two integers where b > a. o a and b, two integers where b > a.
o <H1, H2, ..., Ha, ..., Hb, ...,Hn>, the routers digest. o <H1, H2, ..., Ha, ..., Hb, ...,Hn>, the routers digest.
o <T1, T2, ..., Tm-1, Tm>, a list of times. o <T1, T2, ..., Tm-1, Tm>, a list of times.
o <Tk, dTk.1, dTk.2, ..., dTk.a, ..., dTk.b,..., dTk.n, dTk>, a o <Tk, dTk.1, dTk.2, ..., dTk.a, ..., dTk.b,..., dTk.n, dTk>, a
Type-P-Spatial-One-way-Delay-Vector. Type-P-Spatial-One-way-Delay-Vector.
6.3.3. Metric Units 6.3.3. Metric Units
The value of a Type-P-Segment-ipdv-prev-Stream is a pair of: The value of a Type-P-Segment-ipdv-prev-Stream is a pair of:
The list of <T1, T2, ..., Tm-1, Tm>;
The list of <T1, T2, ..., Tm-1, Tm>; and
A list of pairs of interval of times and delays; A list of pairs of interval of times and delays;
6.3.4. Definition 6.3.4. Definition
Given two routers, Ha and Hb, of the path <H1, H2,..., Ha, ..., Hb, Given two routers, Ha and Hb, of the path <H1, H2,..., Ha, ..., Hb,
..., Hn>, and the matrix of Type-P-Spatial-One-way-Delay-Vector for ..., Hn> and the matrix of Type-P-Spatial-One-way-Delay-Vector for
the packets sent from Src to Dst at times <T1, T2, ..., Tm-1, Tm> : the packets sent from Src to Dst at times <T1, T2, ..., Tm-1, Tm> :
<T1, dT1.1, dT1.2, ..., dT1.a, ..., dT1.b,..., dT1.n, dT1>, <T1, dT1.1, dT1.2, ..., dT1.a, ..., dT1.b,..., dT1.n, dT1>,
<T2, dT2.1, dT2.2, ..., dT2.a, ..., dT2.b,..., dT2.n, dT2>, <T2, dT2.1, dT2.2, ..., dT2.a, ..., dT2.b,..., dT2.n, dT2>,
... ...
<Tm, dTm.1, dTm.2, ..., dTm.a, ..., dTm.b,..., dTm.n, dTm>. <Tm, dTm.1, dTm.2, ..., dTm.a, ..., dTm.b,..., dTm.n, dTm>.
We define the Type-P-Segment-ipdv-prev-Stream as the sequence of We define the Type-P-Segment-ipdv-prev-Stream as the sequence of
packet time pairs and delay variations packet time pairs and delay variations
<(T1, T2 , dT2.ab - dT1.ab) ,..., <(T1, T2 , dT2.ab - dT1.ab) ,...,
(Tk-1, Tk, dTk.ab - dTk-1.ab), ..., (Tk-1, Tk, dTk.ab - dTk-1.ab), ...,
(Tm-1, Tm, dTm.ab - dTm-1.ab)> (Tm-1, Tm, dTm.ab - dTm-1.ab)>
For any pair, Tk, Tk-1 in k=1 through m, the difference dTk.ab - dTk- For any pair, Tk, Tk-1 in k=1 through m, the difference dTk.ab - dTk-
1.ab is undefined if: 1.ab is undefined if:
o the delay dTk.a or the delay dTk-1.a is undefined, OR o the delay dTk.a or the delay dTk-1.a is undefined, OR
o the delay dTk.b or the delay dTk-1.b is undefined. o the delay dTk.b or the delay dTk-1.b is undefined.
RFC 5644 Spatial and Multicast Metrics October 2009
6.3.5. Discussion 6.3.5. Discussion
This metric belongs to the family of inter packet delay variation This metric belongs to the family of inter-packet delay variation
metrics (IPDV in upper case) whose results are extremely sensitive to metrics (IPDV in uppercase) whose results are extremely sensitive to
the inter-packet interval in practice. the inter-packet interval in practice.
The inter-packet interval of an end-to-end IPDV metric is under the The inter-packet interval of an end-to-end IPDV metric is under the
control of the source (ingress point of interest). In contrast, the control of the source (ingress point of interest). In contrast, the
inter-packet interval of a segment IPDV metric is not under the inter-packet interval of a segment IPDV metric is not under the
control the ingress point of interest of the measure, Ha. The control the ingress point of interest of the measure, Ha. The
interval will certainly vary if there is delay variation between the interval will certainly vary if there is delay variation between the
Source and Ha. Therefore, the ingress inter-packet interval must be Source and Ha. Therefore, the ingress inter-packet interval must be
known at Ha in order to fully comprehend the delay variation between known at Ha in order to fully comprehend the delay variation between
Ha and Hb. Ha and Hb.
6.4. A Definition of a Sample of ipdv of a Segment using the Minimum 6.4. A Definition of a Sample of ipdv of a Segment Using the Minimum
Delay Selection Function Delay Selection Function
This metric defines a sample of ipdv [RFC3393] over time between a This metric defines a sample of ipdv [RFC3393] over time between a
pair of routers on a path using the minimum delay as one of the pair of routers on a path using the minimum delay as one of the
selected packets in every pair. selected packets in every pair.
6.4.1. Metric Name 6.4.1. Metric Name
Type-P-Segment-One-way-ipdv-min-Stream Type-P-Segment-One-way-ipdv-min-Stream
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pair of routers on a path using the minimum delay as one of the pair of routers on a path using the minimum delay as one of the
selected packets in every pair. selected packets in every pair.
6.4.1. Metric Name 6.4.1. Metric Name
Type-P-Segment-One-way-ipdv-min-Stream Type-P-Segment-One-way-ipdv-min-Stream
6.4.2. Metric Parameters 6.4.2. Metric Parameters
o Src, the IP address of the sender. o Src, the IP address of the sender.
o Dst, the IP address of the receiver. o Dst, the IP address of the receiver.
o Type-P, the specification of the packet type. o Type-P, the specification of the packet type.
o k, an integer which orders the packets sent.
o i, an integer which identifies a packet sent. o k, an integer that orders the packets sent.
o n, an integer which orders the routers on the path.
o i, an integer that identifies a packet sent.
o n, an integer that orders the routers on the path.
o a and b, two integers where b > a. o a and b, two integers where b > a.
o <H1, H2, ..., Ha, ..., Hb, ...,Hn>, the routers digest. o <H1, H2, ..., Ha, ..., Hb, ...,Hn>, the routers digest.
o <T1, T2, ..., Tm-1, Tm>, a list of times. o <T1, T2, ..., Tm-1, Tm>, a list of times.
o <Tk, dTk.1, dTk.2, ..., dTk.a, ..., dTk.b,..., dTk.n, dTk>, a o <Tk, dTk.1, dTk.2, ..., dTk.a, ..., dTk.b,..., dTk.n, dTk>, a
Type-P-Spatial-One-way-Delay-Vector. Type-P-Spatial-One-way-Delay-Vector.
RFC 5644 Spatial and Multicast Metrics October 2009
6.4.3. Metric Units 6.4.3. Metric Units
The value of a Type-P-Segment-One-way-ipdv-min-Stream is a pair of: The value of a Type-P-Segment-One-way-ipdv-min-Stream is a pair of:
The list of <T1, T2, ..., Tm-1, Tm>;
The list of <T1, T2, ..., Tm-1, Tm>; and
A list of times. A list of times.
6.4.4. Definition 6.4.4. Definition
Given two routers, Ha and Hb, of the path <H1, H2,..., Ha, ..., Hb, Given two routers, Ha and Hb, of the path <H1, H2,..., Ha, ..., Hb,
..., Hn>, and the matrix of Type-P-Spatial-One-way-Delay-Vector for ..., Hn> and the matrix of Type-P-Spatial-One-way-Delay-Vector for
the packets sent from Src to Dst at times <T1, T2, ..., Tm-1, Tm> : the packets sent from Src to Dst at times <T1, T2, ..., Tm-1, Tm> :
<T1, dT1.1, dT1.2, ..., dT1.a, ..., dT1.b,..., dT1.n, dT1>, <T1, dT1.1, dT1.2, ..., dT1.a, ..., dT1.b,..., dT1.n, dT1>,
<T2, dT2.1, dT2.2, ..., dT2.a, ..., dT2.b,..., dT2.n, dT2>, <T2, dT2.1, dT2.2, ..., dT2.a, ..., dT2.b,..., dT2.n, dT2>,
... ...
<Tm, dTm.1, dTm.2, ..., dTm.a, ..., dTm.b,..., dTm.n, dTm>. <Tm, dTm.1, dTm.2, ..., dTm.a, ..., dTm.b,..., dTm.n, dTm>.
We define the Type-P-Segment-One-way-ipdv-min-Stream as the sequence We define the Type-P-Segment-One-way-ipdv-min-Stream as the sequence
of times <dT1.ab - min(dTi.ab) ,..., dTk.ab - min(dTi.ab), ..., of times <dT1.ab - min(dTi.ab) ,..., dTk.ab - min(dTi.ab), ...,
dTm.ab - min(dTi.ab)> where: dTm.ab - min(dTi.ab)> where:
o min(dTi.ab) is the minimum value of the tuples (dTk.b - dTk.a); o min(dTi.ab) is the minimum value of the tuples (dTk.b - dTk.a);
o for each time Tk, dTk.ab is undefined if dTk.a or (inclusive) o for each time Tk, dTk.ab is undefined if dTk.a or (inclusive)
dTk.b is undefined, or the real number (dTk.b - dTk.a) is dTk.b is undefined, or the real number (dTk.b - dTk.a) is
undefined. undefined.
6.4.5. Discussion 6.4.5. Discussion
This metric belongs to the family of packet delay variation metrics This metric belongs to the family of packet delay variation metrics
(PDV). PDV distributions have less sensitivity to inter-packet (PDV). PDV distributions have less sensitivity to inter-packet
interval variations than IPDV values, as discussed above. interval variations than IPDV values, as discussed above.
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In principle, the PDV distribution reflects the variation over many In principle, the PDV distribution reflects the variation over many
different inter-packet intervals, from the smallest inter-packet different inter-packet intervals, from the smallest inter-packet
interval, up to the length of the evaluation interval, Tm - T1. interval, up to the length of the evaluation interval, Tm - T1.
Therefore, when delay variation occurs and disturbs the packet Therefore, when delay variation occurs and disturbs the packet
spacing observed at Ha, the PDV results will likely compare favorably spacing observed at Ha, the PDV results will likely compare favorably
to a PDV measurement where the source is Ha and the destination is to a PDV measurement where the source is Ha and the destination is
Hb, because a wide range of spacings are reflected in any PDV Hb, because a wide range of spacings are reflected in any PDV
distribution. distribution.
7. One-to-group metrics definitions RFC 5644 Spatial and Multicast Metrics October 2009
7. One-to-Group Metrics Definitions
This section defines performance metrics between a source and a group This section defines performance metrics between a source and a group
of receivers. of receivers.
7.1. A Definition for One-to-group Delay 7.1. A Definition for One-to-Group Delay
This section defines a metric for one-way delay between a source and This section defines a metric for one-way delay between a source and
a group of receivers. a group of receivers.
7.1.1. Metric Name 7.1.1. Metric Name
Type-P-One-to-group-Delay-Vector Type-P-One-to-group-Delay-Vector
7.1.2. Metric Parameters 7.1.2. Metric Parameters
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This section defines a metric for one-way delay between a source and This section defines a metric for one-way delay between a source and
a group of receivers. a group of receivers.
7.1.1. Metric Name 7.1.1. Metric Name
Type-P-One-to-group-Delay-Vector Type-P-One-to-group-Delay-Vector
7.1.2. Metric Parameters 7.1.2. Metric Parameters
o Src, the IP address of a host acting as the source. o Src, the IP address of a host acting as the source.
o Recv1,..., RecvN, the IP addresses of the N hosts acting as o Recv1,..., RecvN, the IP addresses of the N hosts acting as
receivers. receivers.
o T, a time. o T, a time.
o dT1,...,dTn a list of times. o dT1,...,dTn a list of times.
o Type-P, the specification of the packet type. o Type-P, the specification of the packet type.
o Gr, the receiving group identifier. The parameter Gr is the o Gr, the receiving group identifier. The parameter Gr is the
multicast group address if the measured packets are transmitted multicast group address if the measured packets are transmitted
over IP multicast. This parameter is to differentiate the over IP multicast. This parameter is to differentiate the
measured traffic from other unicast and multicast traffic. It is measured traffic from other unicast and multicast traffic. It is
OPTIONAL for this metric to avoid losing any generality, i.e. to OPTIONAL for this metric to avoid losing any generality, i.e., to
make the metric also applicable to unicast measurement where there make the metric also applicable to unicast measurement where there
is only one receiver. is only one receiver.
7.1.3. Metric Units 7.1.3. Metric Units
The value of a Type-P-One-to-group-Delay-Vector is a set of Type-P- The value of a Type-P-One-to-group-Delay-Vector is a set of Type-P-
One-way-Delay singletons [RFC2679], which is a sequence of times (a One-way-Delay singletons [RFC2679], that is a sequence of times (a
real number in the dimension of seconds with sufficient resolution to real number in the dimension of seconds with sufficient resolution to
convey the results). convey the results).
7.1.4. Definition 7.1.4. Definition
Given a Type-P packet sent by the source Src at time T, and the N Given a Type-P packet sent by the source Src at time T, and the N
hosts { Recv1,...,RecvN } which receive the packet at the time { hosts { Recv1,...,RecvN } which receive the packet at the time {
T+dT1,...,T+dTn }, or the packet does not pass a receiver within a T+dT1,...,T+dTn }, or the packet does not pass a receiver within a
specified loss threshold time, then the Type-P-One-to-group-Delay- specified loss threshold time, then the Type-P-One-to-group-Delay-
RFC 5644 Spatial and Multicast Metrics October 2009
Vector is defined as the set of the Type-P-One-way-Delay singletons Vector is defined as the set of the Type-P-One-way-Delay singletons
between Src and each receiver with value of { dT1, dT2,...,dTn }, between Src and each receiver with value of { dT1, dT2,...,dTn },
where any of the singletons may be undefined if the packet did not where any of the singletons may be undefined if the packet did not
pass the corresponding receiver within a specified loss threshold pass the corresponding receiver within a specified loss threshold
time. time.
7.2. A Definition for One-to-group Packet Loss 7.2. A Definition for One-to-Group Packet Loss
7.2.1. Metric Name 7.2.1. Metric Name
Type-P-One-to-group-Packet-Loss-Vector Type-P-One-to-group-Packet-Loss-Vector
7.2.2. Metric Parameters 7.2.2. Metric Parameters
o Src, the IP address of a host acting as the source. o Src, the IP address of a host acting as the source.
o Recv1,..., RecvN, the IP addresses of the N hosts acting as o Recv1,..., RecvN, the IP addresses of the N hosts acting as
receivers. receivers.
o T, a time. o T, a time.
o Type-P, the specification of the packet type. o Type-P, the specification of the packet type.
o Gr, the receiving group identifier, OPTIONAL. o Gr, the receiving group identifier, OPTIONAL.
7.2.3. Metric Units 7.2.3. Metric Units
The value of a Type-P-One-to-group-Packet-Loss-Vector is a set of The value of a Type-P-One-to-group-Packet-Loss-Vector is a set of
Type-P-One-way-Packet-Loss singletons [RFC2680]. Type-P-One-way-Packet-Loss singletons [RFC2680].
o T, time the source packet was sent o T, time the source packet was sent.
o L1,...,LN a list of boolean values
o L1,...,LN a list of Boolean values.
7.2.4. Definition 7.2.4. Definition
Given a Type P packet sent by the source Src at T and the N hosts, Given a Type-P packet sent by the source Src at T and the N hosts,
Recv1,...,RecvN, the Type-P-One-to-group-Packet-Loss-Vector is Recv1,...,RecvN, the Type-P-One-to-group-Packet-Loss-Vector is
defined as a set of the Type-P-One-way-Packet-Loss singletons between defined as a set of the Type-P-One-way-Packet-Loss singletons between
Src and each of the receivers Src and each of the receivers:
{T, <L1=0|1>,<L2=0|1>,..., <LN=0|1>}, {T, <L1=0|1>,<L2=0|1>,..., <LN=0|1>},
where the boolean value 0|1 depends on receiving the packet at a where the Boolean value 0|1 depends on receiving the packet at a
particular receiver within a loss threshold time. particular receiver within a loss threshold time.
7.3. A Definition for One-to-group ipdv RFC 5644 Spatial and Multicast Metrics October 2009
7.3. A Definition for One-to-Group ipdv
7.3.1. Metric Name 7.3.1. Metric Name
Type-P-One-to-group-ipdv-Vector Type-P-One-to-group-ipdv-Vector
7.3.2. Metric Parameters 7.3.2. Metric Parameters
o Src, the IP address of a host acting as the source. o Src, the IP address of a host acting as the source.
o Recv1,..., RecvN, the IP addresses of the N hosts acting as o Recv1,..., RecvN, the IP addresses of the N hosts acting as
receivers. receivers.
o T1, a time. o T1, a time.
o T2, a time. o T2, a time.
o ddT1, ...,ddTn, a list of times. o ddT1, ...,ddTn, a list of times.
o Type-P, the specification of the packet type. o Type-P, the specification of the packet type.
o F, a selection function non-ambiguously defining the two packets o F, a selection function non-ambiguously defining the two packets
from the stream selected for the metric. from the stream selected for the metric.
o Gr, the receiving group identifier. The parameter Gr is the o Gr, the receiving group identifier. The parameter Gr is the
multicast group address if the measured packets are transmitted multicast group address if the measured packets are transmitted
over IP multicast. This parameter is to differentiate the over IP multicast. This parameter is to differentiate the
measured traffic from other unicast and multicast traffic. It is measured traffic from other unicast and multicast traffic. It is
OPTIONAL in the metric to avoid losing any generality, i.e. to OPTIONAL in the metric to avoid losing any generality, i.e., to
make the metric also applicable to unicast measurement where there make the metric also applicable to unicast measurement where there
is only one receiver. is only one receiver.
7.3.3. Metric Units 7.3.3. Metric Units
The value of a Type-P-One-to-group-ipdv-Vector is a set of Type-P- The value of a Type-P-One-to-group-ipdv-Vector is a set of Type-P-
One-way-ipdv singletons [RFC3393]. One-way-ipdv singletons [RFC3393].
7.3.4. Definition 7.3.4. Definition
Given a Type-P packet stream, Type-P-One-to-group-ipdv-Vector is Given a Type-P packet stream, Type-P-One-to-group-ipdv-Vector is
defined for two packets transferred from the source Src to the N defined for two packets transferred from the source Src to the N
hosts {Recv1,...,RecvN }, which are selected by the selection hosts {Recv1,...,RecvN }, which are selected by the selection
function F as the difference between the value of the Type-P-One-to- function F as the difference between the value of the Type-P-One-to-
group-Delay-Vector from Src to { Recv1,..., RecvN } at time T1 and group-Delay-Vector from Src to { Recv1,..., RecvN } at time T1 and
the value of the Type-P-One-to-group-Delay-Vector from Src to { the value of the Type-P-One-to-group-Delay-Vector from Src to {
Recv1,...,RecvN } at time T2. T1 is the wire-time at which Src sent Recv1,...,RecvN } at time T2. T1 is the wire-time at which Src sent
RFC 5644 Spatial and Multicast Metrics October 2009
the first bit of the first packet, and T2 is the wire-time at which the first bit of the first packet, and T2 is the wire-time at which
Src sent the first bit of the second packet. This metric is derived Src sent the first bit of the second packet. This metric is derived
from the Type-P-One-to-group-Delay-Vector metric. from the Type-P-One-to-group-Delay-Vector metric.
For a set of real numbers {ddT1,...,ddTn}, the Type-P-One-to-group- For a set of real numbers {ddT1,...,ddTn}, the Type-P-One-to-group-
ipdv-Vector from Src to { Recv1,...,RecvN } at T1, T2 is ipdv-Vector from Src to { Recv1,...,RecvN } at T1, T2 is
{ddT1,...,ddTn} means that Src sent two packets, the first at wire- {ddT1,...,ddTn} means that Src sent two packets, the first at wire-
time T1 (first bit), and the second at wire-time T2 (first bit) and time T1 (first bit), and the second at wire-time T2 (first bit) and
the packets were received by { Recv1,...,RecvN } at wire-time {dT1+ the packets were received by { Recv1,...,RecvN } at wire-time {dT1+
T1,...,dTn+T1}(last bit of the first packet), and at wire-time {dT'1+ T1,...,dTn+T1}(last bit of the first packet), and at wire-time {dT'1+
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ipdv-Vector from Src to { Recv1,...,RecvN } at T1, T2 is ipdv-Vector from Src to { Recv1,...,RecvN } at T1, T2 is
{ddT1,...,ddTn} means that Src sent two packets, the first at wire- {ddT1,...,ddTn} means that Src sent two packets, the first at wire-
time T1 (first bit), and the second at wire-time T2 (first bit) and time T1 (first bit), and the second at wire-time T2 (first bit) and
the packets were received by { Recv1,...,RecvN } at wire-time {dT1+ the packets were received by { Recv1,...,RecvN } at wire-time {dT1+
T1,...,dTn+T1}(last bit of the first packet), and at wire-time {dT'1+ T1,...,dTn+T1}(last bit of the first packet), and at wire-time {dT'1+
T2,...,dT'n+T2} (last bit of the second packet), and that {dT'1- T2,...,dT'n+T2} (last bit of the second packet), and that {dT'1-
dT1,...,dT'n-dTn} ={ddT1,...,ddTn}. dT1,...,dT'n-dTn} ={ddT1,...,ddTn}.
For any pair of selected packets, the difference dT'n-dTn is For any pair of selected packets, the difference dT'n-dTn is
undefined if: undefined if:
o the delay dTn to Receiver n is undefined, OR o the delay dTn to Receiver n is undefined, OR
o the delay dT'n to Receiver n is undefined. o the delay dT'n to Receiver n is undefined.
8. One-to-group Sample Statistics 8. One-to-Group Sample Statistics
The one-to-group metrics defined above are directly achieved by The one-to-group metrics defined above are directly achieved by
collecting relevant unicast one-way metrics measurements results and collecting relevant unicast one-way metrics measurements results and
by gathering them per group of receivers. They produce network by gathering them per group of receivers. They produce network
performance information which guides engineers toward potential performance information that guides engineers toward potential
problems which may have happened on any branch of a multicast routing problems that may have happened on any branch of a multicast routing
tree. tree.
The results of these metrics are not directly usable to present the The results of these metrics are not directly usable to present the
performance of a group because each result is made of a huge number performance of a group because each result is made of a huge number
of singletons which are difficult to read and analyze. As an of singletons that are difficult to read and analyze. As an example,
example, delays are not comparable because the distance between delays are not comparable because the distance between receiver and
receiver and sender differs. Furthermore they don't capture relative sender differs. Furthermore, they don't capture relative performance
performance situation a multiparty communication. situations in a multiparty communication.
From the performance point of view, the multiparty communication From the performance point of view, the multiparty communication
services not only require the support of absolute performance services not only require the support of absolute performance
information but also information on "relative performance". The information but also information on "relative performance".
relative performance means the difference between absolute "Relative performance" means the difference between absolute
performance of all users. Directly using the one-way metrics cannot performance of all users. Directly using the one-way metrics cannot
present the relative performance situation. However, if we use the present the relative performance situation. However, if we use the
variations of all users one-way parameters, we can have new metrics variations of all users' one-way parameters, we can have new metrics
to measure the difference of the absolute performance and hence to measure the difference of the absolute performance and hence
provide the threshold value of relative performance that a multiparty provide the threshold value of relative performance that a multiparty
service might demand. A very good example of the high relative service might demand. A very good example of the high relative
performance requirement is online gaming. A very small difference in performance requirement is online gaming. A very small difference in
delay might result in failure in the game. We have to use multicast delay might result in failure in the game. We have to use multicast-
RFC 5644 Spatial and Multicast Metrics October 2009
specific statistic metrics to define the relative delay required by specific statistic metrics to define the relative delay required by
online gaming. There are many other services, e.g. online biding, online gaming. There are many other services, e.g., online biding,
online stock market, etc., that require multicast metrics in order to online stock market, etc., that require multicast metrics in order to
evaluate the network against their requirements. Therefore, we can evaluate the network against their requirements. Therefore, we can
see the importance of new, multicast specific, statistic metrics to see the importance of new, multicast specific, statistic metrics to
feed this need. feed this need.
We might also use some one-to-group statistic conceptions to present We might also use some one-to-group statistic conceptions to present
and report the group performance and relative performance to save the and report the group performance and relative performance to save the
report transmission bandwidth. Statistics have been defined for One- report transmission bandwidth. Statistics have been defined for One-
way metrics in corresponding RFCs. They provide the foundation of way metrics in corresponding RFCs. They provide the foundation of
definition for performance statistics. For instance, there are definition for performance statistics. For instance, there are
definitions for minimum and maximum One-way delay in [RFC2679]. definitions for minimum and maximum one-way delay in [RFC2679].
However, there is a dramatic difference between the statistics for However, there is a dramatic difference between the statistics for
one-to-one communications and for one-to-many communications. The one-to-one communications and for one-to-many communications. The
former one only has statistics over the time dimension while the former one only has statistics over the time dimension while the
later one can have statistics over both time and space dimensions. later one can have statistics over both time and space dimensions.
This space dimension is introduced by the Matrix concept as This space dimension is introduced by the Matrix concept as
illustrated in Figure 4. For a Matrix M each row is a set of One-way illustrated in Figure 4. For a Matrix M, each row is a set of one-
singletons spreading over the time dimension and each column is way singletons spreading over the time dimension and each column is
another set of One-way singletons spreading over the space dimension. another set of One-way singletons spreading over the space dimension.
Receivers Receivers
Space Space
^ ^
1 | / R1dT1 R1dT2 R1dT3 ... R1dTk \ 1 | / R1dT1 R1dT2 R1dT3 ... R1dTk \
| | | | | |
2 | | R2dT1 R2dT2 R2dT3 ... R2dTk | 2 | | R2dT1 R2dT2 R2dT3 ... R2dTk |
| | | | | |
3 | | R3dT1 R3dT2 R3dT3 ... R3dTk | 3 | | R3dT1 R3dT2 R3dT3 ... R3dTk |
. | | | . | | |
. | | | . | | |
. | | | . | | |
n | \ RndT1 RndT2 RndT3 ... RndTk / n | \ RndT1 RndT2 RndT3 ... RndTk /
+--------------------------------------------> time +--------------------------------------------> time
T0 T0
Figure 4: Matrix M (n*m) Figure 4: Matrix M (n*m)
In Matrix M, each element is a one-way delay singleton. Each column In Matrix M, each element is a one-way delay singleton. Each column
is a delay vector. It contains the One-way delays of the same packet is a delay vector. It contains the one-way delays of the same packet
observed at n points of interest. It implies the geographical factor observed at n points of interest. It implies the geographical factor
of the performance within a group. Each row is a set of One-way of the performance within a group. Each row is a set of one-way
delays observed during a sampling interval at one of the points of delays observed during a sampling interval at one of the points of
interest. It presents the delay performance at a receiver over the interest. It presents the delay performance at a receiver over the
time dimension. time dimension.
RFC 5644 Spatial and Multicast Metrics October 2009
Therefore, one can either calculate statistics by rows over the space Therefore, one can either calculate statistics by rows over the space
dimension or by columns over the time dimension. It's up to the dimension or by columns over the time dimension. It's up to the
operators or service provides which dimension they are interested in. operators or service providers in which dimension they are
For example, a TV broadcast service provider might want to know the interested. For example, a TV broadcast service provider might want
statistical performance of each user in a long term run to make sure to know the statistical performance of each user in a long-term run
their services are acceptable and stable. While for an online gaming to make sure their services are acceptable and stable. While for an
service provider, he might be more interested to know if all users online gaming service provider, he might be more interested in
are served fairly by calculating the statistics over the space knowing if all users are served fairly by calculating the statistics
dimension. This memo does not intend to recommend which of the over the space dimension. This memo does not intend to recommend
statistics are better than the other. which of the statistics are better than the others.
To save the report transmission bandwidth, each point of interest can To save the report transmission bandwidth, each point of interest can
send statistics in a pre-defined time interval to the reference point send statistics in a pre-defined time interval to the reference point
rather than sending every one-way singleton it observed. As long as rather than sending every one-way singleton it observed. As long as
an appropriate time interval is decided, appropriate statistics can an appropriate time interval is decided, appropriate statistics can
represent the performance in a certain accurate scale. How to decide represent the performance in a certain accurate scale. How to decide
the time interval and how to bootstrap all points of interest and the the time interval and how to bootstrap all points of interest and the
reference point depend on applications. For instance, applications reference point depend on applications. For instance, applications
with lower transmission rate can have the time interval longer and with a lower transmission rate can have the time interval be longer,
ones with higher transmission rate can have the time interval and ones with higher transmission rate can have the time interval be
shorter. However, this is out of the scope of this memo. shorter. However, this is out of the scope of this memo.
Moreover, after knowing the statistics over the time dimension, one Moreover, after knowing the statistics over the time dimension, one
might want to know how these statistics are distributed over the might want to know how these statistics are distributed over the
space dimension. For instance, a TV broadcast service provider had space dimension. For instance, a TV broadcast service provider had
the performance Matrix M and calculated the One-way delay mean over the performance Matrix M and calculated the one-way delay mean over
the time dimension to obtain a delay Vector as {V1,V2,..., VN}. He the time dimension to obtain a delay Vector as {V1,V2,..., VN}. He
then calculated the mean of all the elements in the Vector to see then calculated the mean of all the elements in the Vector to see
what level of delay he has served to all N users. This new delay what level of delay he has served to all N users. This new delay
mean gives information on how good the service has been delivered to mean gives information on how well the service has been delivered to
a group of users during a sampling interval in terms of delay. It a group of users during a sampling interval in terms of delay. It
requires twice as much calculation to have this statistic over both requires twice as much calculation to have this statistic over both
time and space dimensions. These kinds of statistics are referred to time and space dimensions. These kinds of statistics are referred to
as 2-level statistics to distinguish them from 1-level statistics as 2-level statistics to distinguish them from 1-level statistics
calculated over either space or time dimension. It can be easily calculated over either space or time dimension. It can be easily
proven that no matter over which dimension a 2-level statistic is proven that no matter over which dimension a 2-level statistic is
calculated first, the results are the same. I.e. one can calculate calculated first, the results are the same. That is, one can
the 2-level delay mean using the Matrix M by having the 1-level delay calculate the 2-level delay mean using the Matrix M by having the
mean over the time dimension first and then calculate the mean of the 1-level delay mean over the time dimension first and then calculate
obtained vector to find out the 2-level delay mean. Or, he can do the mean of the obtained vector to find out the 2-level delay mean.
the 1-level statistic calculation over the space dimension first and Or, he can do the 1-level statistic calculation over the space
then have the 2-level delay mean. Both two results will be exactly dimension first and then have the 2-level delay mean. Both results
the same. Therefore, when defining a 2-level statistic there is no will be exactly the same. Therefore, when defining a 2-level
need to specify the order in which the calculation is executed. statistic, there is no need to specify the order in which the
calculation is executed.
RFC 5644 Spatial and Multicast Metrics October 2009
Many statistics can be defined for the proposed one-to-group metrics Many statistics can be defined for the proposed one-to-group metrics
over either the space dimension or the time dimension or both. This over the space dimension, the time dimension, or both. This memo
memo treats the case where a stream of packets from the Source treats the case where a stream of packets from the Source results in
results in a sample at each of the Receivers in the Group, and these a sample at each of the Receivers in the Group, and these samples are
samples are each summarized with the usual statistics employed in each summarized with the usual statistics employed in one-to-one
one-to-one communication. New statistic definitions are presented, communication. New statistic definitions are presented, which
which summarize the one-to-one statistics over all the Receivers in summarize the one-to-one statistics over all the Receivers in the
the Group. Group.
8.1. Discussion on the Impact of packet loss on statistics 8.1. Discussion on the Impact of Packet Loss on Statistics
Packet loss does have effects on one-way metrics and their Packet loss does have effects on one-way metrics and their
statistics. For example, a lost packet can result in an infinite statistics. For example, a lost packet can result in an infinite
one-way delay. It is easy to handle the problem by simply ignoring one-way delay. It is easy to handle the problem by simply ignoring
the infinite value in the metrics and in the calculation of the the infinite value in the metrics and in the calculation of the
corresponding statistics. However, the packet loss has such a strong corresponding statistics. However, the packet loss has such a strong
impact on the statistics calculation for the one-to-group metrics impact on the statistics calculation for the one-to-group metrics
that it can not be solved by the same method used for one-way that it can not be solved by the same method used for one-way
metrics. This is due to the complexity of building a matrix, which metrics. This is due to the complexity of building a matrix, which
is needed for calculation of the statistics proposed in this memo. is needed for calculation of the statistics proposed in this memo.
The situation is that measurement results obtained by different end The situation is that measurement results obtained by different end
users might have different packet loss pattern. For example, for users might have different packet loss pattern. For example, for
User1, packet A was observed lost. And for User2, packet A was User1, packet A was observed to be lost. And for User2, packet A was
successfully received but packet B was lost. If the method to successfully received, but packet B was lost. If the method to
overcome the packet loss for one-way metrics is applied, the two overcome the packet loss for one-way metrics is applied, the two
singleton sets reported by User1 and User2 will be different in terms singleton sets reported by User1 and User2 will be different in terms
of the transmitted packets. Moreover, if User1 and User2 have of the transmitted packets. Moreover, if User1 and User2 have a
different number of lost packets, the size of the results will be different number of lost packets, the size of the results will be
different. Therefore, for the centralized calculation, the reference different. Therefore, for the centralized calculation, the reference
point will not be able to use these two results to build up the group point will not be able to use these two results to build up the group
Matrix and can not calculate the statistics. The extreme situation Matrix and cannot calculate the statistics. The extreme situation
being the case when no packets arrive at any user. One of the being the case when no packets arrive at any user. One of the
possible solutions is to replace the infinite/undefined delay value possible solutions is to replace the infinite/undefined delay value
by the average of the two adjacent values. For example, if the by the average of the two adjacent values. For example, if the
result reported by user1 is { R1dT1 R1dT2 R1dT3 ... R1dTK-1 UNDEF result reported by User1 is { R1dT1 R1dT2 R1dT3 ... R1dTK-1 UNDEF
R1dTK+1... R1DM } where "UNDEF" is an undefined value, the reference R1dTK+1... R1MD } where "UNDEF" is an undefined value, the reference
point can replace it by R1dTK = {(R1dTK-1)+( R1dTK+1)}/2. Therefore, point can replace it by R1dTK = {(R1dTK-1)+( R1dTK+1)}/2. Therefore,
this result can be used to build up the group Matrix with an this result can be used to build up the group Matrix with an
estimated value R1dTK. There are other possible solutions such as estimated value R1dTK. There are other possible solutions, such as
using the overall mean of the whole result to replace the infinite/ using the overall mean of the whole result to replace the infinite/
undefined value, and so on. However this is out of the scope of this undefined value, and so on. However, this is out of the scope of
memo. this memo.
For the distributed calculation, the reported statistics might have For the distributed calculation, the reported statistics might have
different "weight" to present the group performance, which is different "weight" to present the group performance, which is
especially true for delay and ipdv relevant metrics. For example, especially true for delay and ipdv relevant metrics. For example,
User1 calculates the Type-P-Finite-One-way-Delay-Mean R1DM as shown
in Figure. 8 without any packet loss and User2 calculates the R2DM RFC 5644 Spatial and Multicast Metrics October 2009
with N-2 packet loss. The R1DM and R2DM should not be treated with
equal weight because R2DM was calculated only based on 2 delay values User1 calculates the Type-P-Finite-One-way-Delay-Mean R1MD as shown
in the whole sample interval. One possible solution is to use a in Figure 7 without any packet loss, and User2 calculates the R2MD
weight factor to mark every statistic value sent by users and use with N-2 packet loss. The R1MD and R2MD should not be treated with
equal weight because R2MD was calculated only based on two delay
values in the whole sample interval. One possible solution is to use
a weight factor to mark every statistic value sent by users and use
this factor for further statistic calculation. this factor for further statistic calculation.
8.2. General Metric Parameters 8.2. General Metric Parameters
o Src, the IP address of a host; o Src, the IP address of a host.
o G, the receiving group identifier;
o N, the number of Receivers (Recv1, Recv2, ... RecvN); o G, the receiving group identifier.
o T, a time (start of test interval);
o Tf, a time (end of test interval); o N, the number of Receivers (Recv1, Recv2, ... RecvN).
o T, a time (start of test interval).
o Tf, a time (end of test interval).
o K, the number of packets sent from the source during the test o K, the number of packets sent from the source during the test
interval; interval.
o J[n], the number of packets received at a particular Receiver, n, o J[n], the number of packets received at a particular Receiver, n,
where 1<=n<=N; where 1<=n<=N.
o lambda, a rate in reciprocal seconds (for Poisson Streams);
o lambda, a rate in reciprocal seconds (for Poisson Streams).
o incT, the nominal duration of inter-packet interval, first bit to o incT, the nominal duration of inter-packet interval, first bit to
first bit (for Periodic Streams); first bit (for Periodic Streams).
o T0, a time that MUST be selected at random from the interval [T, o T0, a time that MUST be selected at random from the interval [T,
T+I] to start generating packets and taking measurements (for T+I] to start generating packets and taking measurements (for
Periodic Streams); Periodic Streams).
o TstampSrc, the wire time of the packet as measured at MP(Src) (the
Source Measurement Point); o TstampSrc, the wire-time of the packet as measured at MP(Src) (the
o TstampRecv, the wire time of the packet as measured at MP(Recv), Source Measurement Point).
assigned to packets that arrive within a "reasonable" time;
o TstampRecv, the wire-time of the packet as measured at MP(Recv),
assigned to packets that arrive within a "reasonable" time.
o Tmax, a maximum waiting time for packets at the destination, set o Tmax, a maximum waiting time for packets at the destination, set
sufficiently long to disambiguate packets with long delays from sufficiently long to disambiguate packets with long delays from
packets that are discarded (lost), thus the distribution of delay packets that are discarded (lost); thus, the distribution of delay
is not truncated; is not truncated.
o dT, shorthand notation for a one-way delay singleton value;
o dT, shorthand notation for a one-way delay singleton value.
RFC 5644 Spatial and Multicast Metrics October 2009
o L, shorthand notation for a one-way loss singleton value, either o L, shorthand notation for a one-way loss singleton value, either
zero or one, where L=1 indicates loss and L=0 indicates arrival at zero or one, where L=1 indicates loss and L=0 indicates arrival at
the destination within TstampSrc + Tmax, may be indexed over n the destination within TstampSrc + Tmax, may be indexed over n
Receivers; Receivers.
o DV, shorthand notation for a one-way delay variation singleton o DV, shorthand notation for a one-way delay variation singleton
value. value.
8.3. One-to-group Delay Statistics 8.3. One-to-Group Delay Statistics
This section defines the overall one-way delay statistics for a This section defines the overall one-way delay statistics for a
receiver and for an entire group as illustrated by the matrix below. receiver and for an entire group as illustrated by the matrix below.
Recv /----------- Sample -------------\ Stats Group Stat Recv /----------- Sample -------------\ Stats Group Stat
1 R1dT1 R1dT2 R1dT3 ... R1dTk R1MD \ 1 R1dT1 R1dT2 R1dT3 ... R1dTk R1MD \
| |
2 R2dT1 R2dT2 R2dT3 ... R2dTk R2MD | 2 R2dT1 R2dT2 R2dT3 ... R2dTk R2MD |
| |
3 R3dT1 R3dT2 R3dT3 ... R3dTk R3MD > Group delay 3 R3dT1 R3dT2 R3dT3 ... R3dTk R3MD > Group Delay
. | . |
. | . |
. | . |
n RndT1 RndT2 RndT3 ... RndTk RnMD / n RndT1 RndT2 RndT3 ... RndTk RnMD /
Receiver-n Receiver-n
delay Delay
Figure 5: One-to-group Mean Delay Figure 5: One-to-Group Mean Delay
Statistics are computed on the finite One-way delays of the matrix Statistics are computed on the finite one-way delays of the matrix
above. above.
All One-to-group delay statistics are expressed in seconds with All one-to-group delay statistics are expressed in seconds with
sufficient resolution to convey 3 significant digits. sufficient resolution to convey three significant digits.
8.3.1. Type-P-One-to-group-Receiver-n-Mean-Delay 8.3.1. Type-P-One-to-group-Receiver-n-Mean-Delay
This section defines Type-P-One-to-group-Receiver-n-Mean-Delay the This section defines Type-P-One-to-group-Receiver-n-Mean-Delay, the
Delay Mean at each Receiver N, also named RnMD. Delay Mean, at each Receiver N, also named RnMD.
We obtain the value of Type-P-One-way-Delay singleton for all packets We obtain the value of Type-P-One-way-Delay singleton for all packets
sent during the test interval at each Receiver (Destination), as per sent during the test interval at each Receiver (Destination), as per
[RFC2679]. For each packet that arrives within Tmax of its sending [RFC2679]. For each packet that arrives within Tmax of its sending
time, TstampSrc, the one-way delay singleton (dT) will be the finite time, TstampSrc, the one-way delay singleton (dT) will be the finite
value TstampRecv[i] - TstampSrc[i] in units of seconds. Otherwise, value TstampRecv[i] - TstampSrc[i] in units of seconds. Otherwise,
the value of the singleton is Undefined. the value of the singleton is Undefined.
RFC 5644 Spatial and Multicast Metrics October 2009
J[n] J[n]
--- ---
1 \ 1 \
RnMD = --- * > TstampRecv[i] - TstampSrc[i] RnMD = --- * > TstampRecv[i] - TstampSrc[i]
J[n] / J[n] /
--- ---
i = 1 i = 1
Note: RnMD value is Undefined when J[n] = 0 for all n. Note: RnMD value is Undefined when J[n] = 0 for all n.
Figure 6: Type-P-One-to-group-Receiver-N-Mean-Delay Figure 6: Type-P-One-to-group-Receiver-n-Mean-Delay
where all packets i= 1 through J[n] have finite singleton delays. where all packets i= 1 through J[n] have finite singleton delays.
8.3.2. Type-P-One-to-group-Mean-Delay 8.3.2. Type-P-One-to-group-Mean-Delay
This section defines Type-P-One-to-group-Mean-Delay, the Mean One-way This section defines Type-P-One-to-group-Mean-Delay, the Mean one-way
delay calculated over the entire Group, also named GMD. Delay calculated over the entire Group, also named GMD.
N N
--- ---
1 \ 1 \
GMD = - * > RnMD GMD = - * > RnMD
N / N /
--- ---
n = 1 n = 1
Figure 7: Type-P-One-to-group-Mean-Delay Figure 7: Type-P-One-to-group-Mean-Delay
Note that the Group Mean Delay can also be calculated by summing the Note that the Group Mean Delay can also be calculated by summing the
Finite one-way Delay singletons in the Matrix, and dividing by the finite one-way delay singletons in the matrix, and dividing by the
number of Finite One-way Delay singletons. number of finite one-way delay singletons.
8.3.3. Type-P-One-to-group-Range-Mean-Delay 8.3.3. Type-P-One-to-group-Range-Mean-Delay
This section defines a metric for the range of mean delays over all N This section defines a metric for the Range of Mean Delays over all N
receivers in the group (R1MD, R2MD...RnMD). receivers in the Group (R1MD, R2MD...RnMD).
Type-P-One-to-group-Range-Mean-Delay = GRMD = max(RnMD) - min(RnMD) Type-P-One-to-group-Range-Mean-Delay = GRMD = max(RnMD) - min(RnMD)
8.3.4. Type-P-One-to-group-Max-Mean-Delay 8.3.4. Type-P-One-to-group-Max-Mean-Delay
This section defines a metric for the maximum of mean delays over all This section defines a metric for the Maximum of Mean Delays over all
N receivers in the group (R1MD, R2MD,...RnMD). N receivers in the Group (R1MD, R2MD,...RnMD).
Type-P-One-to-group-Max-Mean-Delay = GMMD = max(RnMD) Type-P-One-to-group-Max-Mean-Delay = GMMD = max(RnMD)
8.4. One-to-group Packet Loss Statistics RFC 5644 Spatial and Multicast Metrics October 2009
8.4. One-to-Group Packet Loss Statistics
This section defines the overall one-way loss statistics for a This section defines the overall one-way loss statistics for a
receiver and for an entire group as illustrated by the matrix below. receiver and for an entire group as illustrated by the matrix below.
Recv /----------- Sample ----------\ Stats Group Stat Recv /----------- Sample ----------\ Stats Group Stat
1 R1L1 R1L2 R1L3 ... R1Lk R1LR \ 1 R1L1 R1L2 R1L3 ... R1Lk R1LR \
| |
2 R2L1 R2L2 R2L3 ... R2Lk R2LR | 2 R2L1 R2L2 R2L3 ... R2Lk R2LR |
| |
3 R3L1 R3L2 R3L3 ... R3Lk R3LR > Group Loss Ratio 3 R3L1 R3L2 R3L3 ... R3Lk R3LR > Group Loss Ratio
. | . |
. | . |
. | . |
n RnL1 RnL2 RnL3 ... RnLk RnLR / n RnL1 RnL2 RnL3 ... RnLk RnLR /
Receiver-n Receiver-n
Loss Ratio Loss Ratio
Figure 8: One-to-group Loss Ratio Figure 8: One-to-Group Loss Ratio
Statistics are computed on the sample of Type-P-One-way-Packet-Loss Statistics are computed on the sample of Type-P-One-way-Packet-Loss
[RFC2680] of the matrix above. [RFC2680] of the matrix above.
All loss ratios are expressed in units of packets lost to total All loss ratios are expressed in units of packets lost to total
packets sent. packets sent.
8.4.1. Type-P-One-to-group-Receiver-n-Loss-Ratio 8.4.1. Type-P-One-to-group-Receiver-n-Loss-Ratio
Given a Matrix of loss singletons as illustrated above, determine the Given a Matrix of loss singletons as illustrated above, determine the
skipping to change at page 35, line 17 skipping to change at page 38, line 5
K K
--- ---
1 \ 1 \
RnLR = - * > RnLk RnLR = - * > RnLk
K / K /
--- ---
k = 1 k = 1
Figure 9: Type-P-One-to-group-Receiver-n-Loss-Ratio Figure 9: Type-P-One-to-group-Receiver-n-Loss-Ratio
RFC 5644 Spatial and Multicast Metrics October 2009
8.4.2. Type-P-One-to-group-Receiver-n-Comp-Loss-Ratio 8.4.2. Type-P-One-to-group-Receiver-n-Comp-Loss-Ratio
Usually, the number of packets sent is used in the denominator of Usually, the number of packets sent is used in the denominator of
packet loss ratio metrics. For the comparative metrics defined here, packet loss ratio metrics. For the comparative metrics defined here,
the denominator is the maximum number of packets received at any the denominator is the maximum number of packets received at any
receiver for the sample and test interval of interest. The numerator receiver for the sample and test interval of interest. The numerator
is the sum of the losses at receiver n. is the sum of the losses at receiver n.
The Comparative Loss Ratio, also named, RnCLR, is defined as The Comparative Loss Ratio, also named, RnCLR, is defined as
skipping to change at page 36, line 7 skipping to change at page 38, line 40
| --- | | --- |
\ k=1 / N \ k=1 / N
Note: Ln is a set of one-way loss values at receiver n. Note: Ln is a set of one-way loss values at receiver n.
There is one value for each of the K packets sent. There is one value for each of the K packets sent.
Figure 10: Type-P-One-to-group-Receiver-n-Comp-Loss-Ratio Figure 10: Type-P-One-to-group-Receiver-n-Comp-Loss-Ratio
8.4.3. Type-P-One-to-group-Loss-Ratio 8.4.3. Type-P-One-to-group-Loss-Ratio
Type-P-One-to-group-Loss-Ratio, the overall Group loss ratio, also Type-P-One-to-group-Loss-Ratio, the overall Group Loss Ratio, also
named GLR, is defined as named GLR, is defined as:
K,N K,N
--- ---
1 \ 1 \
GLR = --- * > Ln(k) GLR = --- * > Ln(k)
K*N / K*N /
--- ---
k,n = 1 k,n = 1
Figure 11: Type-P-One-to-group-Loss-Ratio Figure 11: Type-P-One-to-group-Loss-Ratio
RFC 5644 Spatial and Multicast Metrics October 2009
Where the sum includes all of the Loss singletons, Ln(k), over the N Where the sum includes all of the Loss singletons, Ln(k), over the N
receivers and K packets sent, in a ratio with the total packets over receivers and K packets sent, in a ratio with the total packets over
all receivers. all receivers.
8.4.4. Type-P-One-to-group-Range-Loss-Ratio 8.4.4. Type-P-One-to-group-Range-Loss-Ratio
The One-to-group Loss Ratio Range is defined as: The One-to-group Loss Ratio Range is defined as:
Type-P-One-to-group-Range-Loss-Ratio = max(RnLR) - min(RnLR) Type-P-One-to-group-Range-Loss-Ratio = max(RnLR) - min(RnLR)
It is most effective to indicate the range by giving both the max and It is most effective to indicate the range by giving both the maximum
minimum loss ratios for the Group, rather than only reporting the and minimum loss ratios for the Group, rather than only reporting the
difference between them. difference between them.
8.5. One-to-group Delay Variation Statistics 8.5. One-to-group Delay Variation Statistics
This section defines one-way delay variation (DV) statistics for an This section defines one-way delay variation (DV) statistics for an
entire group as illustrated by the matrix below. entire group as illustrated by the matrix below.
Recv /------------- Sample --------------\ Stats Recv /------------- Sample --------------\ Stats
1 R1ddT1 R1ddT2 R1ddT3 ... R1ddTk R1DV \ 1 R1ddT1 R1ddT2 R1ddT3 ... R1ddTk R1DV \
skipping to change at page 37, line 5 skipping to change at page 39, line 40
2 R2ddT1 R2ddT2 R2ddT3 ... R2ddTk R2DV | 2 R2ddT1 R2ddT2 R2ddT3 ... R2ddTk R2DV |
| |
3 R3ddT1 R3ddT2 R3ddT3 ... R3ddTk R3DV > Group Stat 3 R3ddT1 R3ddT2 R3ddT3 ... R3ddTk R3DV > Group Stat
. | . |
. | . |
. | . |
n RnddT1 RnddT2 RnddT3 ... RnddTk RnDV / n RnddT1 RnddT2 RnddT3 ... RnddTk RnDV /
Figure 12: One-to-group Delay Variation Matrix (DVMa) Figure 12: One-to-group Delay Variation Matrix (DVMa)
Statistics are computed on the sample of Type-P-One-way-Delay- Statistics are computed on the sample of Type-P-One-way-ipdv
Variation singletons of the group delay variation matrix above where singletons of the group delay variation matrix above where RnddTk is
RnddTk is the Type-P-One-way-Delay-Variation singleton evaluated at the Type-P-One-way-ipdv singleton evaluated at Receiver n for the
Receiver n for the packet k and where RnDV is the point-to-point one- packet k and where RnDV is the point-to-point one-way packet delay
way packet delay variation for Receiver n. variation for Receiver n.
All One-to-group delay variation statistics are expressed in seconds All One-to-group delay variation statistics are expressed in seconds
with sufficient resolution to convey 3 significant digits. with sufficient resolution to convey three significant digits.
8.5.1. Type-P-One-to-group-Range-Delay-Variation 8.5.1. Type-P-One-to-group-Range-Delay-Variation
This section defines a metric for the range of delays variation over This section defines a metric for the Range of Delay Variation over
all N receivers in the Group. all N receivers in the Group.
RFC 5644 Spatial and Multicast Metrics October 2009
Maximum DV and minimum DV over all receivers summarize the Maximum DV and minimum DV over all receivers summarize the
performance over the Group (where DV is a point-to-point metric). performance over the Group (where DV is a point-to-point metric).
For each receiver, the DV is usually expressed as the 1-10^(-3) For each receiver, the DV is usually expressed as the 1-10^(-3)
quantile of one-way delay minus the minimum one-way delay. quantile of one-way delay minus the minimum one-way delay.
Type-P-One-to-group-Range-Delay-Variation = GRDV = Type-P-One-to-group-Range-Delay-Variation = GRDV =
= max(RnDV) - min(RnDV) for all n receivers = max(RnDV) - min(RnDV) for all n receivers
This range is determined from the minimum and maximum values of the This range is determined from the minimum and maximum values of the
point-to-point one-way IP Packet Delay Variation for the set of point-to-point one-way IP Packet Delay Variation for the set of
Destinations in the group and a population of interest, using the Destinations in the group and a population of interest, using the
Packet Delay Variation expressed as the 1-10^-3 quantile of one-way Packet Delay Variation expressed as the 1-10^-3 quantile of one-way
delay minus the minimum one-way delay. If a more demanding service delay minus the minimum one-way delay. If a more demanding service
is considered, one alternative is to use the 1-10^-5 quantile, and in is considered, one alternative is to use the 1-10^-5 quantile, and in
either case the quantile used should be recorded with the results. either case, the quantile used should be recorded with the results.
Both the minimum and the maximum delay variation are recorded, and Both the minimum and the maximum delay variation are recorded, and
both values are given to indicate the location of the range. both values are given to indicate the location of the range.
9. Measurement Methods: Scalability and Reporting 9. Measurement Methods: Scalability and Reporting
Virtually all the guidance on measurement processes supplied by the Virtually all the guidance on measurement processes supplied by the
earlier IPPM RFCs (such as [RFC2679] and [RFC2680]) for one-to-one earlier IPPM RFCs (such as [RFC2679] and [RFC2680]) for one-to-one
scenarios is applicable here in the spatial and multiparty scenarios is applicable here in the spatial and multiparty
measurement scenario. The main difference is that the spatial and measurement scenario. The main difference is that the spatial and
multiparty configurations require multiple points of interest where a multiparty configurations require multiple points of interest where a
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as the reference point. However, both the storage and transfer as the reference point. However, both the storage and transfer
capacity can be reduced if the points of interest are capable of capacity can be reduced if the points of interest are capable of
computing the summary statistics that describe each measurement computing the summary statistics that describe each measurement
interval. This is consistent with many operational monitoring interval. This is consistent with many operational monitoring
architectures today, where even the individual singletons may not be architectures today, where even the individual singletons may not be
stored at each point of interest. stored at each point of interest.
In recognition of the likely need to minimize the form of the results In recognition of the likely need to minimize the form of the results
for storage and communication, the Group metrics above have been for storage and communication, the Group metrics above have been
constructed to allow some computations on a per-Receiver basis. This constructed to allow some computations on a per-Receiver basis. This
RFC 5644 Spatial and Multicast Metrics October 2009
means that each Receiver's statistics would normally have an equal means that each Receiver's statistics would normally have an equal
weight with all other Receivers in the Group (regardless of the weight with all other Receivers in the Group (regardless of the
number of packets received). number of packets received).
9.1. Computation methods 9.1. Computation Methods
The scalability issue can be raised when there are thousands of The scalability issue can be raised when there are thousands of
points of interest in a group who are trying to send back the points of interest in a group who are trying to send back the
measurement results to the reference point for further processing and measurement results to the reference point for further processing and
analysis. The points of interest can send either the whole measured analysis. The points of interest can send either the whole measured
sample or only the calculated statistics. The former one is a sample or only the calculated statistics. The former is a
centralized statistic calculation method and the latter one is a centralized statistic calculation method and the latter is a
distributed statistic calculation method. The sample should include distributed statistic calculation method. The sample should include
all metrics parameters, the values and the corresponding sequence all metrics parameters, the values, and the corresponding sequence
numbers. The transmission of the whole sample can cost much more numbers. The transmission of the whole sample can cost much more
bandwidth than the transmission of the statistics that should include bandwidth than the transmission of the statistics that should include
all statistic parameters specified by policies and the additional all statistic parameters specified by policies and the additional
information about the whole sample, such as the size of the sample, information about the whole sample, such as the size of the sample,
the group address, the address of the point of interest, the ID of the group address, the address of the point of interest, the ID of
the sample session, and so on. Apparently, the centralized the sample session, and so on. Apparently, the centralized
calculation method can require much more bandwidth than the calculation method can require much more bandwidth than the
distributed calculation method when the sample size is big. This is distributed calculation method when the sample size is big. This is
especially true when the measurement has a very large number of the especially true when the measurement has a very large number of the
points of interest. It can lead to a scalability issue at the points of interest. It can lead to a scalability issue at the
skipping to change at page 39, line 17 skipping to change at page 42, line 5
to the reference point first to obtain the general information of the to the reference point first to obtain the general information of the
group performance. If detailed results are required, the reference group performance. If detailed results are required, the reference
point should send the requests to the points of interest, which could point should send the requests to the points of interest, which could
be particular ones or the whole group. This procedure can happen in be particular ones or the whole group. This procedure can happen in
the off peak time and can be well scheduled to avoid delivery of too the off peak time and can be well scheduled to avoid delivery of too
many points of interest at the same time. Compression techniques can many points of interest at the same time. Compression techniques can
also be used to minimize the bandwidth required by the transmission. also be used to minimize the bandwidth required by the transmission.
This could be a measurement protocol to report the measurement This could be a measurement protocol to report the measurement
results. However, this is out of the scope of this memo. results. However, this is out of the scope of this memo.
RFC 5644 Spatial and Multicast Metrics October 2009
9.2. Measurement 9.2. Measurement
To prevent any bias in the result, the configuration of a one-to-many To prevent any bias in the result, the configuration of a one-to-many
measure must take in consideration that more packets will to be measure must take into consideration that more packets will be routed
routed than sent (copies of a packet sent are expected to arrive at than sent (copies of a packet sent are expected to arrive at many
many destination points) and selects a test packets rate that will destination points) and select a test packet rate that will not
not impact the network performance. impact the network performance.
9.3. Effect of Time and Space Aggregation Order on Stats 9.3. Effect of Time and Space Aggregation Order on Stats
This section presents the impact of the aggregation order on the This section presents the impact of the aggregation order on the
scalability of the reporting and of the computation. It makes the scalability of the reporting and of the computation. It makes the
hypothesis that receivers are not co-located and that results are hypothesis that receivers are not co-located and that results are
gathered in a point of reference for further usages. gathered in a point of reference for further usages.
Multimetrics samples are represented in a matrix as illustrated below Multimetric samples are represented in a matrix as illustrated below
Point of Point of
interest Interest
1 R1S1 R1S1 R1S1 ... R1Sk \ 1 R1S1 R1S1 R1S1 ... R1Sk \
| |
2 R2S1 R2S2 R2S3 ... R2Sk | 2 R2S1 R2S2 R2S3 ... R2Sk |
| |
3 R3S1 R3S2 R3S3 ... R3Sk > sample over space 3 R3S1 R3S2 R3S3 ... R3Sk > Sample over Space
. | . |
. | . |
. | . |
n RnS1 RnS2 RnS3 ... RnSk / n RnS1 RnS2 RnS3 ... RnSk /
S1M S2M S3M ... SnM Stats over space S1M S2M S3M ... SnM Stats over Space
\------------- ------------/ \------------- ------------/
\/ \/
Stat over space and time Stats over Space and Time
Figure 13: Impact of space aggregation on multimetrics Stat Figure 13: Impact of Space Aggregation on Multimetrics Stats
Two methods are available to compute statistics on a matrix: Two methods are available to compute statistics on a matrix:
o Method 1: The statistic metric is computed over time and then over o Method 1: The statistic metric is computed over time and then over
space; space; or
o Method 2: The statistic metric is computed over space and then o Method 2: The statistic metric is computed over space and then
over time. over time.
These 2 methods differ only by the order of the aggregation. The RFC 5644 Spatial and Multicast Metrics October 2009
These two methods differ only by the order of the aggregation. The
order does not impact the computation resources required. It does order does not impact the computation resources required. It does
not change the value of the result. However, it impacts severely the not change the value of the result. However, it impacts severely the
minimal volume of data to report: minimal volume of data to report:
o Method 1: Each point of interest computes periodically statistics
o Method 1: Each point of interest periodically computes statistics
over time to lower the volume of data to report. They are over time to lower the volume of data to report. They are
reported to the reference point for for subsequent computations reported to the reference point for subsequent computations over
over the spatial dimension. This volume no longer depends on the the spatial dimension. This volume no longer depends on the
number of samples. It is only proportional to the computation number of samples. It is only proportional to the computation
period; period.
o Method 2: The volume of data to report is proportional to the o Method 2: The volume of data to report is proportional to the
number of samples. Each sample, RiSi, must be reported to the number of samples. Each sample, RiSi, must be reported to the
reference point for computing statistic over space and statistic reference point for computing statistic over space and statistic
over time. The volume increases with the number of samples. It over time. The volume increases with the number of samples. It
is proportional to the number of test packets; is proportional to the number of test packets;
Method 2 has severe drawbacks in terms of security and dimensioning: Method 2 has severe drawbacks in terms of security and dimensioning:
o Increasing the rate of the test packets may result in a Denial of o Increasing the rate of the test packets may result in a Denial of
Service toward the points of reference; Service (DoS) toward the points of reference;
o The dimensioning of a measurement system is quite impossible to o The dimensioning of a measurement system is quite impossible to
validate because any increase of the rate of the test packets will validate because any increase of the rate of the test packets will
increase the bandwidth requested to collect the raw results. increase the bandwidth requested to collect the raw results.
The computation period over time period (commonly named aggregation The computation period over time period (commonly named the
period) provides the reporting side with a control of various aggregation period) provides the reporting side with a control of
collecting aspects such as bandwidth, computation and storage various collecting aspects such as bandwidth, computation, and
capacities. So this draft defines metrics based on method 1. storage capacities. So this document defines metrics based on method
1.
9.3.1. Impact on spatial statistics 9.3.1. Impact on Spatial Statistics
Two methods are available to compute spatial statistics: Two methods are available to compute spatial statistics:
o Method 1: spatial segment metrics and statistics are preferably
o Method 1: Spatial segment metrics and statistics are preferably
computed over time for each points of interest; computed over time for each points of interest;
o Method 2: Vectors metrics are intrinsically instantaneous space o Method 2: Vectors metrics are intrinsically instantaneous space
metrics which must be reported using Method2 whenever metrics, which must be reported using Method 2 whenever
instantaneous metrics information is needed. instantaneous metrics information is needed.
9.3.2. Impact on one-to-group statistics RFC 5644 Spatial and Multicast Metrics October 2009
9.3.2. Impact on One-to-Group Statistics
Two methods are available to compute group statistics: Two methods are available to compute group statistics:
o Method1: Figure 5 and Figure 8 illustrate the method chosen: the
one-to-one statistic is computed per interval of time before the o Method 1: Figure 5 and Figure 8 illustrate the method. The one-
computation of the mean over the group of receivers; to-one statistic is computed per interval of time before the
o Method2: Figure 13 presents the second one, metric is computed computation of the mean over the group of receivers.
over space and then over time.
o Method 2: Figure 13 presents the second method. The metric is
computed over space and then over time.
10. Manageability Considerations 10. Manageability Considerations
This section defines the reporting of all the metrics introduced in This section defines the reporting of all the metrics introduced in
the document. the document.
Information models of spatial metrics and of one-to-group metrics are Information models of spatial metrics and of one-to-group metrics are
similar excepted that points of interests of spatial vectors MUST be similar except that points of interests of spatial vectors MUST be
ordered. ordered.
The complexity of the reporting relies on the number of points of The complexity of the reporting relies on the number of points of
interests. interest.
10.1. Reporting spatial metric 10.1. Reporting Spatial Metric
The reporting of spatial metrics shares a lot of aspects with The reporting of spatial metrics shares a lot of aspects with RFC
RFC2679-80. New ones are common to all the definitions and are 2679 and RFC 2680. New ones are common to all the definitions and
mostly related to the reporting of the path and of methodology are mostly related to the reporting of the path and of methodology
parameters that may bias raw results analysis. This section presents parameters that may bias raw results analysis. This section presents
these specific parameters and then lists exhaustively the parameters these specific parameters and then lists exhaustively the parameters
that SHOULD be reported. that SHOULD be reported.
10.1.1. Path 10.1.1. Path
End-to-end metrics can't determine the path of the measure despite End-to-end metrics can't determine the path of the measure despite
IPPM RFCs recommend it to be reported (See Section 3.8.4 of the fact that IPPM RFCs recommend it be reported (see section 3.8.4
[RFC2679]). Spatial metrics vectors provide this path. The report of [RFC2679]). Spatial metrics vectors provide this path. The
of a spatial vector MUST include the points of interests involved: report of a spatial vector MUST include the points of interests
the sub set of the routers of the path participating to the involved: the sub-set of the routers of the path participating to the
instantaneous measure. instantaneous measure.
10.1.2. Host order 10.1.2. Host Order
A spatial vector MUST order the points of interest according to their A spatial vector MUST order the points of interest according to their
order in the path. The ordering MAY be based on information from the order in the path. The ordering MAY be based on information from the
TTL in IPv4, the Hop Limit in IPv6 or the corresponding information TTL in IPv4, the Hop Limit in IPv6, or the corresponding information
in MPLS. in MPLS.
RFC 5644 Spatial and Multicast Metrics October 2009
The report of a spatial vector MUST include the ordered list of the The report of a spatial vector MUST include the ordered list of the
hosts involved in the instantaneous measure. hosts involved in the instantaneous measure.
10.1.3. Timestamping bias 10.1.3. Timestamping Bias
The location of the point of interest inside a node influences the The location of the point of interest inside a node influences the
timestamping skew and accuracy. As an example, consider that some timestamping skew and accuracy. As an example, consider that some
internal machinery delays the timestamping up to 3 milliseconds then internal machinery delays the timestamping up to three milliseconds;
the minimal uncertainty reported be 3 ms if the internal delay is then the minimal uncertainty reported be 3 ms if the internal delay
unknown at the time of the timestamping. is unknown at the time of the timestamping.
The report of a spatial vector MUST include the uncertainty of the The report of a spatial vector MUST include the uncertainty of the
timestamping compared to wire time. timestamping compared to wire-time.
10.1.4. Reporting spatial One-way Delay 10.1.4. Reporting Spatial One-Way Delay
The reporting includes information to report for one-way-delay as the The reporting includes information to report for one-way delay as
Section 3.6 of [RFC2679]. The same apply for packet loss and ipdv. section 3.6 of [RFC2679]. The same applies for packet loss and ipdv.
10.2. Reporting One-to-group metric 10.2. Reporting One-to-Group Metric
All reporting rules described in [RFC2679] and [RFC2680] apply to the All reporting rules described in [RFC2679] and [RFC2680] apply to the
corresponding One-to-group metrics. Following are specific corresponding One-to-group metrics. The following are specific
parameters that SHOULD be reported. parameters that SHOULD be reported.
10.2.1. Path 10.2.1. Path
As suggested by the [RFC2679] and [RFC2680], the path traversed by As suggested by [RFC2679] and [RFC2680], the path traversed by the
the packet SHOULD be reported, if possible. For One-to-group packet SHOULD be reported, if possible. For One-to-group metrics,
metrics, the path tree between the source and the destinations or the the path tree between the source and the destinations or the set of
set of paths between the source and each destination SHOULD be paths between the source and each destination SHOULD be reported.
reported.
Path tree might not be as valuable as individual paths because an The path tree might not be as valuable as individual paths because an
incomplete path might be difficult to identify in the path tree. For incomplete path might be difficult to identify in the path tree. For
example, how many points of interest are reached by a packet example, how many points of interest are reached by a packet
travelling along an incomplete path? traveling along an incomplete path?
10.2.2. Group size 10.2.2. Group Size
The group size SHOULD be reported as one of the critical management The group size SHOULD be reported as one of the critical management
parameters. One-to-group metrics, unlike spatial metrics, don't parameters. One-to-group metrics, unlike spatial metrics, don't
require the ordering of the points of interests because group members require the ordering of the points of interests because group members
receive the packets in parallel. receive the packets in parallel.
10.2.3. Timestamping bias 10.2.3. Timestamping Bias
It is the same as described in section 10.1.3. It is the same as described in section 10.1.3.
RFC 5644 Spatial and Multicast Metrics October 2009
10.2.4. Reporting One-to-group One-way Delay 10.2.4. Reporting One-to-group One-way Delay
It is the same as described in section 10.1.4. It is the same as described in section 10.1.4.
10.2.5. Measurement method 10.2.5. Measurement Method
As explained in section 9, the measurement method will have impact on As explained in section 9, the measurement method will have impact on
the analysis of the measurement result. Therefore, it SHOULD be the analysis of the measurement result. Therefore, it SHOULD be
reported. reported.
10.3. Metric identification 10.3. Metric Identification
IANA assigns each metric defined by the IPPM WG with a unique IANA assigns each metric defined by the IPPM WG a unique identifier
identifier as per [RFC4148] in the IANA-IPPM-METRICS-REGISTRY-MIB. as per [RFC4148] in the IANA-IPPM-METRICS-REGISTRY-MIB.
10.4. Information model 10.4. Information Model
This section presents the elements of information and the usage of This section presents the elements of information and the usage of
the information reported for network performance analysis. It is out the information reported for network performance analysis. It is out
of the scope of this section to define how the information is of the scope of this section to define how the information is
reported. reported.
The information model is built with pieces of information introduced The information model is built with pieces of information introduced
and explained in one-way delay definitions [RFC2679], in packet loss and explained in the sections of [RFC2679] , [RFC2680] , [RFC3393],
definitions [RFC2680] and in IPDV definitions of [RFC3393] and and [RFC3432] that define the IPPM metrics and from any of the
[RFC3432]. It includes not only information given by "Reporting the sections named "Reporting the metric" , "Methodology", and "Errors
metric" sections but by sections "Methodology" and "Errors and and Uncertainties" whenever they exist in these documents.
Uncertainties".
Following are the elements of information taken from end-to-end The following are the elements of information taken from end-to-end
metrics definitions referred in this memo and from spatial and metrics definitions referred to in this memo and from spatial and
multicast metrics it defines: multicast metrics it defines:
o Packet_type, The Type-P of test packets (Type-P); o Packet_type, the Type-P of test packets (Type-P).
o Packet_length, a packet length in bits (L);
o Src_host, the IP address of the sender; o Packet_length, a packet length in bits (L).
o Dst_host, the IP address of the receiver;
o Hosts_serie: <H1, H2,..., Hn>, a list of points of interest o Src_host, the IP address of the sender.
participating to the instantaneous measure. They are routers in
o Dst_host, the IP address of the receiver.
o Hosts_series: <H1, H2,..., Hn>, a list of points of interest
participating in the instantaneous measure. They are routers in
the case of spatial metrics or receivers in the case of one-to- the case of spatial metrics or receivers in the case of one-to-
group metrics; group metrics.
o Loss_threshold: The threshold of infinite delay;
o Systematic_error: constant delay between wire time and o Loss_threshold, the threshold of infinite delay.
timestamping;
o Calibration_error: maximal uncertainty; RFC 5644 Spatial and Multicast Metrics October 2009
o Src_time, the sending time for a measured packet;
o Dst_time, the receiving time for a measured packet; o Systematic_error, constant delay between wire-time and
o Result_status : an indicator of usability of a result 'Resource timestamping.
exhaustion' 'infinite', 'lost';
o Delays_serie: <dT1,..., dTn> a list of delays; o Calibration_error, maximal uncertainty.
o Losses_serie: <B1, B2, ..., Bi, ..., Bn>, a list of Boolean values
(spatial) or a set of Boolean values (one-to-group); o Src_time, the sending time for a measured packet.
o Result_status_serie: a list of results status;
o dT: a delay; o Dst_time, the receiving time for a measured packet.
o Singleton_number: a number of singletons;
o Observation_duration: An observation duration; o Result_status, an indicator of usability of a result 'Resource
exhaustion' 'infinite', 'lost'.
o Delays_series, <dT1,..., dTn>, a list of delays.
o Losses_series, <B1, B2, ..., Bi, ..., Bn>, a list of Boolean
values (spatial) or a set of Boolean values (one-to-group).
o Result_status_series, a list of results status.
o dT, a delay.
o Singleton_number, a number of singletons.
o Observation_duration, an observation duration.
o metric_identifier. o metric_identifier.
Following is the information of each vector that SHOULD be available The following is the information of each vector that SHOULD be
to compute samples: available to compute samples:
o Packet_type; o Packet_type;
o Packet_length; o Packet_length;
o Src_host, the sender of the packet; o Src_host, the sender of the packet;
o Dst_host, the receiver of the packet, apply only for spatial o Dst_host, the receiver of the packet, apply only for spatial
vectors; vectors;
o Hosts_serie: not ordered for one-to-group;
o Hosts_series, not ordered for one-to-group;
o Src_time, the sending time for the measured packet; o Src_time, the sending time for the measured packet;
o dT, the end-to-end one-way delay for the measured packet, apply o dT, the end-to-end one-way delay for the measured packet, apply
only for spatial vectors; only for spatial vectors;
o Delays_serie: apply only for delays and ipdv vector, not ordered
o Delays_series, apply only for delays and ipdv vector, not ordered
for one-to-group; for one-to-group;
o Losses_serie: apply only for packets loss vector, not ordered for
RFC 5644 Spatial and Multicast Metrics October 2009
o Losses_series, apply only for packets loss vector, not ordered for
one-to-group; one-to-group;
o Result_status_serie;
o Observation_duration: the difference between the time of the last o Result_status_series;
o Observation_duration, the difference between the time of the last
singleton and the time of the first singleton. singleton and the time of the first singleton.
o Following is the context information (measure, points of
interests) that SHOULD be available to compute samples :
* Loss threshold; Following is the context information (measure, points of interests)
* Systematic error: constant delay between wire time and that SHOULD be available to compute samples:
timestamping;
* Calibration error: maximal uncertainty; o Loss threshold;
o Systematic error, constant delay between wire-time and
timestamping;
o Calibration error, maximal uncertainty.
A spatial or a one-to-group sample is a collection of singletons A spatial or a one-to-group sample is a collection of singletons
giving the performance from the sender to a single point of interest. giving the performance from the sender to a single point of interest.
Following is the information that SHOULD be available for each sample
to compute statistics: The following is the information that SHOULD be available for each
sample to compute statistics:
o Packet_type; o Packet_type;
o Packet_length; o Packet_length;
o Src_host, the sender of the packet; o Src_host, the sender of the packet;
o Dst_host, the receiver of the packet; o Dst_host, the receiver of the packet;
o Start_time, the sending time of the first packet; o Start_time, the sending time of the first packet;
o Delays_serie: apply only for delays and ipdv samples;
o Losses_serie: apply only for packets loss samples; o Delays_series, apply only for delays and ipdv samples;
o Result_status_serie;
o Observation_duration: the difference between the time of the last o Losses_series, apply only for packets loss samples;
o Result_status_series;
o Observation_duration, the difference between the time of the last
singleton of the last sample and the time of the first singleton singleton of the last sample and the time of the first singleton
of the first sample. of the first sample.
o Following is the context information (measure, points of
interests) that SHOULD be available to compute statistics :
* Loss threshold;
* Systematic error: constant delay between wire time and
timestamping;
* Calibration error: maximal uncertainty;
Following is the information of each statistic that SHOULD be The following is the context information (measure, points of
interests) that SHOULD be available to compute statistics:
o Loss threshold;
RFC 5644 Spatial and Multicast Metrics October 2009
o Systematic error, constant delay between wire-time and
timestamping;
o Calibration error, maximal uncertainty;
The following is the information of each statistic that SHOULD be
reported: reported:
o Result; o Result;
o Start_time; o Start_time;
o Duration; o Duration;
o Result_status; o Result_status;
o Singleton_number, the number of singletons the statistic is
computed on; o Singleton_number, the number of singletons on which the statistic
is computed;
11. Security Considerations 11. Security Considerations
Spatial and one-to-group metrics are defined on the top of end-to-end Spatial and one-to-group metrics are defined on the top of end-to-end
metrics. Security considerations discussed in One-way delay metrics metrics. Security considerations discussed in the one-way delay
definitions of [RFC2679] , in packet loss metrics definitions of metrics definitions of [RFC2679], in packet loss metrics definitions
[RFC2680] and in IPDV metrics definitions of[RFC3393] and [RFC3432] of [RFC2680] and in IPDV metrics definitions of [RFC3393] and
apply to metrics defined in this memo. [RFC3432] apply to metrics defined in this memo.
Someone may spoof the identity of a Point of interest identity and Someone may spoof the identity of a point of interest identity and
intentionally send corrupt results in order to remotely orient the intentionally send corrupt results in order to remotely orient the
traffic engineering decisions. traffic engineering decisions.
A point of interest could intentionally corrupt its results in order A point of interest could intentionally corrupt its results in order
to remotely orient the traffic engineering decisions. to remotely orient the traffic engineering decisions.
11.1. Spatial metrics 11.1. Spatial Metrics
Malicious generation of packets which match systematically the hash Malicious generation of packets that systematically match the hash
function used to detect the packets may lead to a DoS attack toward function used to detect the packets may lead to a DoS attack toward
the point of reference. the point of reference.
Spatial measurement results carry the performance of individual Spatial measurement results carry the performance of individual
segments of the path and the identity of nodes. An attacker may segments of the path and the identity of nodes. An attacker may
infer from this information the points of weakness of a network (e.g. infer from this information the points of weakness of a network
congested node) which would require the least amount of additional (e.g., congested node) that would require the least amount of
attacking traffic to exploit. Therefore, monitoring information additional attacking traffic to exploit. Therefore, monitoring
should be carried in a way which prevents unintended recipients from information should be carried in a way that prevents unintended
inspecting the measurement reports. A straight forward solution is
to restrict access to the reports using encrypted sessions or secured
networks.
11.2. One-to-group metrics RFC 5644 Spatial and Multicast Metrics October 2009
recipients from inspecting the measurement reports. A
straightforward solution is to restrict access to the reports using
encrypted sessions or secured networks.
11.2. One-to-Group Metrics
Reporting of measurement results from a huge number of probes may Reporting of measurement results from a huge number of probes may
overload reference point resources (network, network interfaces, overload reference point resources (network, network interfaces,
computation capacities ...). computation capacities, etc.).
The configuration of a measurement must take in consideration that The configuration of a measurement must take into consideration that
implicitly more packets will be routed than sent and selects a test implicitly more packets will be routed than sent and select a test
packets rate accordingly. Collecting statistics from a huge number packet rate accordingly. Collecting statistics from a huge number of
of probes may overload any combination of the network where the probes may overload any combination of the network to which the
measurement controller is attached to, measurement controller network measurement controller is attached, measurement controller network
interfaces and measurement controller computation capacities. interfaces, and measurement controller computation capacities.
One-to-group metrics measurement should consider using source One-to-group metric measurements should consider using source
authentication protocols, standardized in the MSEC group, to avoid authentication protocols, standardized in the MSEC group, to avoid
fraud packet in the sampling interval. The test packet rate could be fraud packet in the sampling interval. The test packet rate could be
negotiated before any measurement session to avoid deny of service negotiated before any measurement session to avoid denial-of-service
attacks. attacks.
A point of interest could intentionally degrade its results in order A point of interest could intentionally degrade its results in order
to remotely increase the quality of the network on the branches of to remotely increase the quality of the network on the branches of
the multicast tree it is connected to. the multicast tree to which it is connected.
12. Acknowledgments 12. Acknowledgments
Lei would like to acknowledge Prof. Zhili Sun from CCSR, University Lei would like to acknowledge Professor Zhili Sun from CCSR,
of Surrey, for his instruction and helpful comments on this work. University of Surrey, for his instruction and helpful comments on
this work.
13. IANA Considerations 13. IANA Considerations
Metrics defined in this memo are designed to be registered in the Metrics defined in this memo have been registered in the IANA IPPM
IANA IPPM METRICS REGISTRY as described in initial version of the METRICS REGISTRY as described in the initial version of the registry
registry [RFC4148] : [RFC4148]:
IANA is asked to register the following metrics in the IANA-IPPM- IANA has registered the following metrics in the IANA-IPPM-METRICS-
METRICS-REGISTRY-MIB : REGISTRY-MIB:
ietfSpatialOneWayDelayVector OBJECT-IDENTITY ietfSpatialOneWayDelayVector OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
RFC 5644 Spatial and Multicast Metrics October 2009
"Type-P-Spatial-One-way-Delay-Vector" "Type-P-Spatial-One-way-Delay-Vector"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 5.1."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 5.1."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 52 }
ietfSpatialPacketLossVector OBJECT-IDENTITY ietfSpatialPacketLossVector OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-Spatial-Packet-Loss-Vector" "Type-P-Spatial-Packet-Loss-Vector"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 5.2."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 5.2."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 53 }
ietfSpatialOneWayIpdvVector OBJECT-IDENTITY ietfSpatialOneWayIpdvVector OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-Spatial-One-way-ipdv-Vector" "Type-P-Spatial-One-way-ipdv-Vector"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 5.3."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 5.3."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 54 }
ietfSegmentOneWayDelayStream OBJECT-IDENTITY ietfSegmentOneWayDelayStream OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-Segment-One-way-Delay-Stream" "Type-P-Segment-One-way-Delay-Stream"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 6.1."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 6.1."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn RFC 5644 Spatial and Multicast Metrics October 2009
:= { ianaIppmMetrics 55 }
ietfSegmentPacketLossStream OBJECT-IDENTITY ietfSegmentPacketLossStream OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-Segment-Packet-Loss-Stream" "Type-P-Segment-Packet-Loss-Stream"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 6.2."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 6.2."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 56 }
ietfSegmentIpdvPrevStream OBJECT-IDENTITY ietfSegmentIpdvPrevStream OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-Segment-ipdv-prev-Stream" "Type-P-Segment-ipdv-prev-Stream"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 6.3."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 6.3."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 57 }
ietfSegmentIpdvMinStream OBJECT-IDENTITY ietfSegmentIpdvMinStream OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-Segment-ipdv-min-Stream" "Type-P-Segment-ipdv-min-Stream"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 6.4."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 6.4."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 58 }
-- One-to-group metrics -- One-to-group metrics
ietfOneToGroupDelayVector OBJECT-IDENTITY ietfOneToGroupDelayVector OBJECT-IDENTITY
RFC 5644 Spatial and Multicast Metrics October 2009
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-One-to-group-Delay-Vector" "Type-P-One-to-group-Delay-Vector"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 7.1."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 7.1."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 59 }
ietfOneToGroupPacketLossVector OBJECT-IDENTITY ietfOneToGroupPacketLossVector OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-One-to-group-Packet-Loss-Vector" "Type-P-One-to-group-Packet-Loss-Vector"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 7.2."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 7.2."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 60 }
ietfOneToGroupIpdvVector OBJECT-IDENTITY ietfOneToGroupIpdvVector OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-One-to-group-ipdv-Vector" "Type-P-One-to-group-ipdv-Vector"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 7.3."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 7.3."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 61 }
-- One to group statistics -- One to group statistics
-- --
ietfOnetoGroupReceiverNMeanDelay OBJECT-IDENTITY ietfOnetoGroupReceiverNMeanDelay OBJECT-IDENTITY
STATUS current STATUS current
RFC 5644 Spatial and Multicast Metrics October 2009
DESCRIPTION DESCRIPTION
"Type-P-One-to-group-Receiver-n-Mean-Delay" "Type-P-One-to-group-Receiver-n-Mean-Delay"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 8.3.1."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 8.3.1."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 62 }
ietfOneToGroupMeanDelay OBJECT-IDENTITY ietfOneToGroupMeanDelay OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-One-to-group-Mean-Delay" "Type-P-One-to-group-Mean-Delay"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 8.3.2."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 8.3.2."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 63 }
ietfOneToGroupRangeMeanDelay OBJECT-IDENTITY ietfOneToGroupRangeMeanDelay OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-One-to-group-Range-Mean-Delay" "Type-P-One-to-group-Range-Mean-Delay"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 8.3.3."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 8.3.3."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 64 }
ietfOneToGroupMaxMeanDelay OBJECT-IDENTITY ietfOneToGroupMaxMeanDelay OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-One-to-group-Max-Mean-Delay" "Type-P-One-to-group-Max-Mean-Delay"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 8.3.4."
-- RFC Ed.: replace yyyy with actual RFC number & remove this RFC 5644 Spatial and Multicast Metrics October 2009
note
:= { ianaIppmMetrics nn } -- IANA assigns nn "RFC 5644, section 8.3.4."
:= { ianaIppmMetrics 65 }
ietfOneToGroupReceiverNLossRatio OBJECT-IDENTITY ietfOneToGroupReceiverNLossRatio OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-One-to-group-Receiver-n-Loss-Ratio" "Type-P-One-to-group-Receiver-n-Loss-Ratio"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 8.4.1."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 8.4.1."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 66 }
-- --
ietfOneToGroupReceiverNCompLossRatio OBJECT-IDENTITY ietfOneToGroupReceiverNCompLossRatio OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-One-to-group-Receiver-n-Comp-Loss-Ratio" "Type-P-One-to-group-Receiver-n-Comp-Loss-Ratio"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 8.4.2."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 8.4.2."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 67 }
ietfOneToGroupLossRatio OBJECT-IDENTITY ietfOneToGroupLossRatio OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-One-to-group-Loss-Ratio" "Type-P-One-to-group-Loss-Ratio"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 8.4.3."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 8.4.3."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 68 }
RFC 5644 Spatial and Multicast Metrics October 2009
-- --
ietfOneToGroupRangeLossRatio OBJECT-IDENTITY ietfOneToGroupRangeLossRatio OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-One-to-group-Range-Loss-Ratio" "Type-P-One-to-group-Range-Loss-Ratio"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 8.4.4."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 8.4.4."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 69 }
ietfOneToGroupRangeDelayVariation OBJECT-IDENTITY ietfOneToGroupRangeDelayVariation OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-One-to-group-Range-Delay-Variation" "Type-P-One-to-group-Range-Delay-Variation"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 8.5.1."
-- RFC Ed.: replace yyyy with actual RFC number & remove this "RFC 5644, section 8.5.1."
note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics 70 }
-- --
14. References 14. References
14.1. Normative References 14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way [RFC2679] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
Delay Metric for IPPM", RFC 2679, September 1999. Delay Metric for IPPM", RFC 2679, September 1999.
[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
Metric for IP Performance Metrics (IPPM)", RFC 3393, Metric for IP Performance Metrics (IPPM)", RFC 3393,
November 2002. November 2002.
RFC 5644 Spatial and Multicast Metrics October 2009
[RFC4148] Stephan, E., "IP Performance Metrics (IPPM) Metrics [RFC4148] Stephan, E., "IP Performance Metrics (IPPM) Metrics
Registry", BCP 108, RFC 4148, August 2005. Registry", BCP 108, RFC 4148, August 2005.
14.2. Informative References 14.2. Informative References
[I-D.ietf-ippm-spatial-composition]
Morton, A. and E. Stephan, "Spatial Composition of
Metrics", draft-ietf-ippm-spatial-composition-09 (work in
progress), June 2009.
[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330, "Framework for IP Performance Metrics", RFC 2330,
May 1998. May 1998.
[RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network [RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network
performance measurement with periodic streams", RFC 3432, performance measurement with periodic streams", RFC 3432,
November 2002. November 2002.
[SPATIAL] Morton, A. and E. Stephan, "Spatial Composition of
Metrics", Work in Progress, June 2009.
Authors' Addresses Authors' Addresses
Stephan Emile Stephan Emile
France Telecom Division R&D France Telecom Division R&D
2 avenue Pierre Marzin 2 avenue Pierre Marzin
Lannion, F-22307 Lannion F-22307
France
Fax: +33 2 96 05 18 52 Fax: +33 2 96 05 18 52
Email: emile.stephan@orange-ftgroup.com EMail: emile.stephan@orange-ftgroup.com
Lei Liang Lei Liang
CCSR, University of Surrey CCSR, University of Surrey
Guildford Guildford
Surrey, GU2 7XH Surrey GU2 7XH
UK
Fax: +44 1483 683641 Fax: +44 1483 683641
Email: L.Liang@surrey.ac.uk EMail: L.Liang@surrey.ac.uk
Al Morton Al Morton
200 Laurel Ave. South 200 Laurel Ave. South
Middletown, NJ 07748 Middletown, NJ 07748
USA USA
Phone: +1 732 420 1571 Phone: +1 732 420 1571
Email: acmorton@att.com EMail: acmorton@att.com
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