draft-ietf-ippm-multimetrics-03.txt   draft-ietf-ippm-multimetrics-04.txt 
Network Working Group E. Stephan Network Working Group E. Stephan
Internet-Draft France Telecom Internet-Draft France Telecom
Intended status: Informational L. Liang Intended status: Informational L. Liang
Expires: September 2, 2007 University of Surrey Expires: January 7, 2008 University of Surrey
A. Morton A. Morton
AT&T Labs AT&T Labs
March 1, 2007 July 6, 2007
IP Performance Metrics (IPPM) for spatial and multicast IP Performance Metrics (IPPM) for spatial and multicast
draft-ietf-ippm-multimetrics-03 draft-ietf-ippm-multimetrics-04
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
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Abstract Abstract
The IETF IP Performance Metrics (IPPM) working group has standardized The IETF IP Performance Metrics (IPPM) working group has standardized
metrics for measuring end-to-end performance between 2 points. This metrics for measuring end-to-end performance between 2 points. This
memo defines 2 sets of metrics to extend these end-to-end ones. It memo defines 2 sets of metrics to extend these end-to-end ones. It
defines spatial metrics for measuring the performance of segments defines spatial metrics for measuring the performance of segments
along a path and metrics for measuring the performance of a group of along a path and metrics for measuring the performance of a group of
users in multiparty communications. users in multiparty communications.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Multiparty metric . . . . . . . . . . . . . . . . . . . . 6 2.1. Path Digest Hosts . . . . . . . . . . . . . . . . . . . . 6
2.2. Spatial metric . . . . . . . . . . . . . . . . . . . . . . 6 2.2. Multiparty metric . . . . . . . . . . . . . . . . . . . . 6
2.3. Spatial metric points of interest . . . . . . . . . . . . 6 2.3. Spatial metric . . . . . . . . . . . . . . . . . . . . . . 6
2.4. One-to-group metric . . . . . . . . . . . . . . . . . . . 6 2.4. One-to-group metric . . . . . . . . . . . . . . . . . . . 6
2.5. One-to-group metric points of interest . . . . . . . . . . 6 2.5. Points of interest . . . . . . . . . . . . . . . . . . . . 6
2.6. Reference point . . . . . . . . . . . . . . . . . . . . . 6 2.6. Reference point . . . . . . . . . . . . . . . . . . . . . 8
2.7. Vector . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.7. Vector . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.8. Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . 7 2.8. Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3. Motivations for spatial and one-to-group metrics . . . . . . . 8 3. Motivations . . . . . . . . . . . . . . . . . . . . . . . . . 9
3.1. spatial metrics . . . . . . . . . . . . . . . . . . . . . 8 3.1. Motivations for spatial metrics . . . . . . . . . . . . . 9
3.2. One-to-group metrics . . . . . . . . . . . . . . . . . . . 9 3.2. Motivations for One-to-group metrics . . . . . . . . . . . 10
3.3. Discussion on Group-to-one and Group-to-group metrics . . 10 3.3. Discussion on Group-to-one and Group-to-group metrics . . 11
4. Spatial metrics definitions . . . . . . . . . . . . . . . . . 10 4. Spatial vectors metrics definitions . . . . . . . . . . . . . 11
4.1. A Definition for Spatial One-way Delay Vector . . . . . . 10 4.1. A Definition for Spatial One-way Delay Vector . . . . . . 12
4.2. A Definition of a sample of One-way Delay of a sub path . 13 4.2. A Definition for Spatial One-way Packet Loss Vector . . . 13
4.3. A Definition for Spatial One-way Packet Loss Vector . . . 16 4.3. A Definition for Spatial One-way Ipdv Vector . . . . . . . 15
4.4. A Definition for Spatial One-way Jitter Vector . . . . . . 17 4.4. Spatial Methodology . . . . . . . . . . . . . . . . . . . 17
4.5. Pure Passive Metrics . . . . . . . . . . . . . . . . . . . 19 5. Spatial Segments metrics definitions . . . . . . . . . . . . . 19
4.6. Discussion on spatial statistics . . . . . . . . . . . . . 21 5.1. A Definition of a sample of One-way Delay of a segment
5. One-to-group metrics definitions . . . . . . . . . . . . . . . 21 of the path . . . . . . . . . . . . . . . . . . . . . . . 19
5.1. A Definition for one-to-group One-way Delay . . . . . . . 21 5.2. A Definition of a sample of Packet Loss of a segment
5.2. A Definition for one-to-group One-way Packet Loss . . . . 22 of the path . . . . . . . . . . . . . . . . . . . . . . . 21
5.3. A Definition for one-to-group One-way Jitter . . . . . . . 22 5.3. A Definition of a sample of One-way Ipdv of a segment
6. One-to-Group Sample Statistics . . . . . . . . . . . . . . . . 24 of the path . . . . . . . . . . . . . . . . . . . . . . . 24
6.1. Discussion on the Impact of packet loss on statistics . . 26 5.4. Discussion on Passive Segment Metrics . . . . . . . . . . 24
6.2. General Metric Parameters . . . . . . . . . . . . . . . . 27 6. One-to-group metrics definitions . . . . . . . . . . . . . . . 27
6.3. One-to-Group one-way Delay Statistics . . . . . . . . . . 28 6.1. A Definition for one-to-group One-way Delay . . . . . . . 27
6.4. One-to-Group one-way Loss Statistics . . . . . . . . . . . 31 6.2. A Definition for one-to-group One-way Packet Loss . . . . 28
6.5. One-to-Group one-way Delay Variation Statistics . . . . . 33 6.3. A Definition for one-to-group One-way Ipdv . . . . . . . . 28
7. Measurement Methods: Scaleability and Reporting . . . . . . . 33 7. One-to-Group Sample Statistics . . . . . . . . . . . . . . . . 30
7.1. Computation methods . . . . . . . . . . . . . . . . . . . 34 7.1. Discussion on the Impact of packet loss on statistics . . 32
7.2. Measurement . . . . . . . . . . . . . . . . . . . . . . . 35 7.2. General Metric Parameters . . . . . . . . . . . . . . . . 33
7.3. effect of Time and Space Aggregation Order on Group 7.3. One-to-Group one-way Delay Statistics . . . . . . . . . . 34
Stats . . . . . . . . . . . . . . . . . . . . . . . . . . 35 7.4. One-to-Group one-way Loss Statistics . . . . . . . . . . . 37
7.4. effect of Time and Space Aggregation Order on Spatial 7.5. One-to-Group one-way Delay Variation Statistics . . . . . 39
Stats . . . . . . . . . . . . . . . . . . . . . . . . . . 37 8. Measurement Methods: Scaleability and Reporting . . . . . . . 39
8. Open issues . . . . . . . . . . . . . . . . . . . . . . . . . 37 8.1. Computation methods . . . . . . . . . . . . . . . . . . . 40
9. Security Considerations . . . . . . . . . . . . . . . . . . . 37 8.2. Measurement . . . . . . . . . . . . . . . . . . . . . . . 41
9.1. passive measurement . . . . . . . . . . . . . . . . . . . 37 8.3. Effect of Time and Space Aggregation Order on Stats . . . 41
9.2. one-to-group metric . . . . . . . . . . . . . . . . . . . 37 9. Manageability Considerations . . . . . . . . . . . . . . . . . 43
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 37 9.1. Reporting spatial metric . . . . . . . . . . . . . . . . . 43
11. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38 9.2. Reporting One-to-group metric . . . . . . . . . . . . . . 44
12. References . . . . . . . . . . . . . . . . . . . . . . . . . . 42 9.3. Metric identification . . . . . . . . . . . . . . . . . . 44
12.1. Normative References . . . . . . . . . . . . . . . . . . . 42 9.4. Reporting data model . . . . . . . . . . . . . . . . . . . 44
12.2. Informative References . . . . . . . . . . . . . . . . . . 43 10. Open issues . . . . . . . . . . . . . . . . . . . . . . . . . 48
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 43 11. Security Considerations . . . . . . . . . . . . . . . . . . . 48
Intellectual Property and Copyright Statements . . . . . . . . . . 45 11.1. Spatial metrics . . . . . . . . . . . . . . . . . . . . . 48
11.2. one-to-group metric . . . . . . . . . . . . . . . . . . . 48
12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 49
13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 49
14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 55
14.1. Normative References . . . . . . . . . . . . . . . . . . . 55
14.2. Informative References . . . . . . . . . . . . . . . . . . 56
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 56
Intellectual Property and Copyright Statements . . . . . . . . . . 58
1. Introduction 1. Introduction
The metrics specified in this memo are built on notions introduced
and discussed in the IPPM Framework document, RFC 2330 [RFC2330].
The reader should be familiar with these documents.
This memo makes use of definitions of end-to-end One-way Delay
Metrics defined in the RFC 2679 [RFC2679] to define metrics for
decomposition of end-to-end one-way delays measurements.
This memo makes use of definitions of end-to-end One-way Packet loss
Metrics defined in the RFC 2680 [RFC2680] to define metrics for
decomposition of end-to-end one-way packet loss measurements.
The IPPM WG defined a framework for metric definitions and end-to-end The IPPM WG defined a framework for metric definitions and end-to-end
measurements: measurements:
o A general framework for defining performance metrics, described in o A general framework for defining performance metrics, described in
the Framework for IP Performance Metrics [RFC2330]; the Framework for IP Performance Metrics [RFC2330];
o A One-way Active Measurement Protocol Requirements [RFC3763]; o A One-way Active Measurement Protocol Requirements [RFC3763];
o A One-way Active Measurement Protocol (OWAMP) [RFC4656]; o A One-way Active Measurement Protocol (OWAMP) [RFC4656];
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o A Framework for Defining Empirical Bulk Transfer Capacity Metrics o A Framework for Defining Empirical Bulk Transfer Capacity Metrics
[RFC3148]; [RFC3148];
o One-way Loss Pattern Sample Metrics [RFC3357]; o One-way Loss Pattern Sample Metrics [RFC3357];
o IP Packet Delay Variation Metric for IPPM [RFC3393]; o IP Packet Delay Variation Metric for IPPM [RFC3393];
o Network performance measurement for periodic streams [RFC3432]; o Network performance measurement for periodic streams [RFC3432];
o Packet Reordering Metric for IPPM [RFC4737][Work in progress]; o Packet Reordering Metric for IPPM [RFC4737];
Based on these works, this memo defines 2 kinds of multi party
metrics. This memo defines spatial and one-to-group metrics based on the
framework and on the end-to-end metrics defined in these documents.
Firstly it defines spatial metrics: Firstly it defines spatial metrics:
o A 'sample', called Type-P-Spatial-One-way-Delay-Vector, will be o A 'vector', called Type-P-Spatial-One-way-Delay-Vector, will be
introduced to divide an end-to-end Type-P-One-way-Delay in a introduced to divide an end-to-end Type-P-One-way-Delay [RFC2679]
spatial sequence of one-way delays. in a spatial sequence of one-way delays.
o A 'sample', called Type-P-Spatial-One-way-Packet-Loss-Vector, will o A 'vector', called Type-P-Spatial-One-way-Packet-Loss-Vector, will
be introduced to divide an end-to-end Type-P-One-way-Packet-Loss be introduced to divide an end-to-end Type-P-One-way-Packet-Loss
in a spatial sequence of packet loss. [RFC2680] in a spatial sequence of packet loss.
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 'vector',
called Type-P-Spatial-One-way-Jitter-Vector, will be introduced to called Type-P-Spatial-One-way-ipdv-Vector, will be introduced to
divide an end-to-end Type-P-One-way-ipdv in a spatial sequence of divide an end-to-end Type-P-One-way-ipdv in a spatial sequence of
jitter. ipdv.
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-subpath-One-way-Delay-Stream, will be introduced to called Type-P-Segment-One-way-Delay-Stream, will be introduced to
define the one-way-delay between a pair of host of the path. This define a set of one-way delays between a pair of host of the path;
metric is similar to Type-P-One-way-Delay-Stream.
o Using Type-P-subpath-One-way-Delay-Stream, a 'sample' Type-P- o Using the Type-P-Spatial-Packet-Loss-Vector metric, a 'sample',
Passive-One-way-Delay-Stream will be introduced to define passive called Type-P-Segment-Packet-Loss-Stream, will be introduced to
metrics. These metrics are designed for pure passive measurement define a set of packet losses between a pair of host of the path;
methodology as introduced by PSAMP WG.
o Using the Type-P-Spatial-ipdv-Vector metric, a 'sample', called
Type-P-Segment-ipdv-Stream, will be introduced to define a set of
ipdvs between a pair of host of the path;
Then it defines one-to-group metrics. Then it defines one-to-group metrics.
o Using one test packet sent from one sender to a group of o Using one test packet sent from one sender to a group of
receivers, a 'sample', called Type-P-one-to-group-One-way-Delay- receivers, a 'sample', called Type-P-one-to-group-One-way-Delay-
Vector, will be introduced to define the list of Type-P-one-way- Vector, will be introduced to define the list of Type-P-one-way-
delay between this sender and the group of receivers. delay [RFC2679] between this sender and the group of receivers.
o Using one test packet sent from one sender to a group of o Using one test packet sent from one sender to a group of
receivers, a 'sample', called Type-P-one-to-group-One-way-Packet- receivers, a 'sample', called Type-P-one-to-group-One-way-Packet-
Loss-Vector, will be introduced to define the list of Type-P-One- Loss-Vector, will be introduced to define the list of Type-P-One-
way-Packet-Loss between this sender and the group of receivers way-Packet-Loss [RFC2680] between this sender and the group of
receivers
o Using one test packet sent from one sender to a group of o Using one test packet sent from one sender to a group of
receivers, a 'sample', called Type-P-one-to-group-One-way-Jitter- receivers, a 'sample', called Type-P-one-to-group-One-way-ipdv-
Vector, will be introduced to define the list of Type-P-One-way- Vector, will be introduced to define the list of Type-P-One-way-
ipdv between this sender and the group of receivers ipdv between this sender and the group of receivers
o Then a discussion section presents the set of statistics that may o Then a discussion section presents the set of statistics that may
be computed on the top of these metrics to present the QoS in a be computed using these metrics to present the network performance
view of a group of users as well as the requirements of relative in the view of a group of users. The statistics may be the basis
QoS on multiparty communications. for requirements (e.g. fairness) on multiparty communications. .
Reporting of metrics is defined in the section "Manageability
Consideration".
2. Terminology 2. Terminology
2.1. Multiparty metric 2.1. Path Digest Hosts
A metric is said to be multiparty if the definition involved more The list of the hosts of a path from a source to a destination.
than two sources or destinations in the measurements. All multiparty
2.2. Multiparty metric
A metric is said to be multiparty if the topology involves more than
one source or destination in the measurements. All multiparty
metrics define a set of hosts called "points of interest", where one metrics define a set of hosts called "points of interest", where one
host is the source and other hosts are the measurement collection host is the source and other hosts are the measurement collection
points. For example, if the set of points of interest is < ha, hb, points. For example, if the set of points of interest is < ha, hb,
hc, ..., hn >, where ha is the source and < hb, hc, ..., hn > are the hc, ..., hn >, where ha is the source and < hb, hc, ..., hn > are the
destinations, then measurements may be conducted between < ha, hb>, < destinations, then measurements may be conducted between < ha, hb>, <
ha, hc>, ..., <ha, hn >. ha, hc>, ..., <ha, hn >.
2.2. Spatial metric For the purposes of this memo (reflecting the scope of a single
source), the only multiparty metrics are one-to-group metrics.
A metric is said to be spatial if one of the hosts involved is
neither the source nor the destination of the metered packet.
2.3. Spatial metric points of interest 2.3. Spatial metric
Points of interest of a spatial metric are the routers or sibling in A metric is said to be spatial if one of the hosts involved is
the path between source and destination (in addition to the source neither the source nor the destination of the measured packet.
and the destination themselves).
2.4. One-to-group metric 2.4. 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 several destinations. Thus, one source and (potentially) received by several destinations. Thus,
the topology of the communication group can be viewed as a centre- the topology of the communication group can be viewed as a centre-
distributed or server-client topology with the source as the centre/ distributed or server-client topology with the source as the centre/
server in the topology. server in the topology.
2.5. One-to-group metric points of interest 2.5. Points of interest
Points of interest of One-to-group metrics are the set of host Points of interest are the set of hosts* (as per RFC2330 definition,
destinations receiving packets from the source (in addition to the that is including nodes) of the set of hosts involved in the delivery
source itself). of the packets (in addition to the source itself). Note that the set
of the points of interest are (a possibly arbitrary) subset of all
the hosts involved in the path. Points of interest of One-to-group
metrics are the hosts receiving packets from the source (in addition
to the source itself).
Src Recv
`. ,-.
`. ,' `...... 1
`. ; :
`. ; :
; :... 2
| |
: ;
: ;.... 3
: ;
`. ,'
`-'....... N
Figure 1: One-to-group points of interest
A points of interest of spatial metrics is a host of the set of hosts
involved in the delivery of the packets from the source.
Src ------. Hosts
\
`---X ... 1
\
x
/
.---------X .... 2
/
x
\
`---X .... 3
\
\
\
X .... N
\
\
\
`---- Dst
Note: 'x' are nodes which are not points of interest
Figure 2: Spatial points of interest
2.6. Reference point 2.6. Reference point
The centre/server in the one-to-group measurement that is controlled The centre/server in the multimetrics measurement that is controlled
by network operators can be a very good reference point where by network operators can be a very good reference point where
measurement data can be collected for further processing although the measurement data can be collected for further processing although the
actual measurements have to be carried out at all points of interest. actual measurements have to be carried out at all points of interest.
I.e., the measurement points will be all clients/receivers while the Thus, we can define the reference point as the server where the
reference point acts as source for the one-to-group metric. Thus, we statistic calculation will be carried out.
can define the reference point as the host while the statistic
calculation will be carried out.
2.7. Vector 2.7. Vector
A group of singletons is the set of results of the observation of the
behaviour of the same packet at different places of a network.
A Vector is a set of singletons, which are a set of results of the A Vector is a set of singletons, which are a set of results of the
observation of the behaviour of the same packet at different places observation of the behaviour of the same packet at different places
of a network at different time. For instance, if One-way delay of a network at different time. For instance, if One-way delay
singletons observed at N receivers for Packet P sent by the source singletons observed at N receivers for Packet P sent by the source
Src are dT1, dT2,..., dTN, it can be say that a vector V with N Src are dT1, dT2,..., dTN, it can be say that a vector V with N
elements can be organized as {dT1, dT2,..., dTN}. The elements in elements can be organized as {dT1, dT2,..., dTN}. The elements in
one vector are singletons distinct with each other in terms of both one vector are singletons distinct with each other in terms of both
measurement point and time. Given the vector V as an example, the measurement point and time. Given the vector V as an example, the
element dT1 is distinct from the rest by measured at receiver 1 at element dT1 is distinct from the rest by measured at receiver 1 at
time T1. Additional to a singleton, Vector gives information over a time T1. Additional to a singleton, Vector gives information over a
space dimension. space dimension.
2.8. Matrix 2.8. Matrix
Several vectors can organize form up a Matrix, which contains results Several vectors can form up a Matrix, which contains results observed
observed in a sampling interval at different place of a network at in a sampling interval at different place of a network at different
different time. For instance, given One-way delay vectors V1={dT11, time. For instance, given One-way delay vectors V1={dT11, dT12,...,
dT12,..., dT1N}, V2={dT21, dT22,..., dT2N},..., Vm={dTm1, dTm2,..., dT1N}, V2={dT21, dT22,..., dT2N},..., Vm={dTm1, dTm2,..., dTmN} for
dTmN} for Packet P1, P2,...,Pm, we can have a One-way delay Matrix Packet P1, P2,...,Pm, we can have a One-way delay Matrix {V1,
{V1, V2,...,Vm}. Additional to the information given by a Vector, a V2,...,Vm}. Additional to the information given by a Vector, a
Matrix is more powerful to present network performance in both space Matrix is more powerful to present network performance in both space
and time dimensions. It normally corresponds to a sample. and time dimensions. It normally corresponds to a sample.
The relation among Singleton, Vector and Matrix can be shown in the The relation among Singleton, Vector and Matrix can be shown in the
following Figure 1. following Figure 3.
one-to-group Singleton Point of Singleton
/ Sample interest / Samples
Src Recv .............................. ,----. ^ /
.................... 1 R1dT1 R1dT2 R1dT3 R1dT4 / R1.....| / R1dT1 R1dT2 R1dT3 ... R3dTk \
`:=-.._ / \ | | |
T `._ ``-..__ ; R2........| | R2dT1 R2dT2 R2dT3 ... R3dTk |
`. `-... 2 R2dT1 R2dT2 R2dT3 R2dT4 Src | || | |
`-. | R3....| | R3dT1 R3dT2 R3dT3 ... R3dTk |
`-. | || | |
`.... N R3dT1 R3dT2 R3dT3 R3dT4 : ;| | |
\ / | | |
\ Rn......| \ RndT1 RndT2 RndT3 ... RndTk /
`-----' +-------------------------------------> time
Vector Matrix Vector Matrix
(space) (time) (space) (time)
Figure 1: Relation beween Singletons, vectors and matrix Figure 3: Relation beween Singletons, vectors and matrix
3. Motivations for spatial and one-to-group metrics 3. Motivations
All IPPM metrics are defined for end-to-end measurement. These All IPPM metrics are defined for end-to-end measurement. These
metrics provide very good guides for measurement in the pair metrics provide very good guides for measurement in the pair
communications. However, further efforts should be put to define communications. However, further efforts should be put to define
metrics for multiparty measurements such as one to one trajectory metrics for multiparty measurements such as one to one trajectory
metrics and one to multipoint metrics. metrics and one to multipoint metrics.
3.1. spatial metrics 3.1. Motivations for spatial metrics
Decomposition of instantaneous end-to-end measures is needed: Decomposition of instantaneous end-to-end measures is needed:
o Decomposing the performance of interdomain path is desirable in o Decomposing the performance of interdomain path is desirable in
interdomain to qualify per AS contribution to the performance. So interdomain to qualify per AS contribution to the performance. So
it is necessary to define standard spatial metrics before going it is necessary to define standard spatial metrics before going
further in the computation of inter domain path with QoS further in the computation of inter domain path with QoS
constraint. constraint.
o Traffic engineering and troubleshooting applications require o Traffic engineering and troubleshooting applications require
spatial views of the one-way delay consumption, identification of spatial views of the one-way delay consumption, identification of
the location of the lost of packets and the decomposition of the the location of the lost of packets and the decomposition of the
jitter over the path. ipdv over the path.
o Monitoring the QoS of a multicast tree, of MPLS point-to- o Monitoring the QoS of a multicast tree, of MPLS point-to-
multipoint and inter-domain communication require spatial multipoint and inter-domain communication require spatial
decomposition of the one-way delay, of the packet loss and of the decomposition of the one-way delay, of the packet loss and of the
jitter. ipdv.
o Composition of metrics is a need to scale in the measurement o Composition of metrics is a need to scale in the measurement
plane. Spatial measure give typically the individual performance plane. Spatial measure give typically the individual performance
of an intra domain segment. It is the elementary piece of of an intra domain segment. It is the elementary piece of
information to exchange for measuring interdomain performance information to exchange for measuring interdomain performance
based on composition of metrics. based on composition of metrics.
o The PSAMP WG defines capabilities to sample packets in a way to to o The PSAMP WG defines capabilities to sample packets in a way to to
support instantaneous measurement respecful of the IPPM framework support instantaneous measurement respecful of the IPPM framework
[RFC2330]. Consequently it is necessary to define a set of [RFC2330]. Consequently it is necessary to define a set of
spatial metrics for passive and active techniques. spatial metrics for passive and active techniques.
3.2. One-to-group metrics 3.2. 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 in the view of a group the performance of a multiparty communication in the view of a group
with consideration that it involves a group of people rather than with consideration that it involves a group of people rather than
two. As a consequence a simple one-way metric cannot describe the two. As a consequence a simple one-way metric cannot describe the
multi-connection situation. We need some new metrics to collect multi-connection situation. We need some new metrics to collect
performance of all the connections for further statistics analysis. performance of all the connections for further statistics analysis.
A group of metrics are proposed in this stage named one-to-group A group of metrics are proposed in this stage named one-to-group
performance metrics based on the unicast metrics defined in IPPM WG. performance metrics based on the unicast metrics defined in IPPM WG.
skipping to change at page 10, line 38 skipping to change at page 11, line 39
measurement points. However, we can always avoid this confusion by measurement points. However, we can always avoid this confusion by
treating the connections as one-to-group or group-to-one in our treating the connections as one-to-group or group-to-one in our
measurements without consideration on how the real communication will measurements without consideration on how the real communication will
be carried out. For example, if one group of hosts < ha, hb, hc, be carried out. For example, if one group of hosts < ha, hb, hc,
..., hn > are acting as sources to send data to another group of ..., hn > are acting as sources to send data to another group of
hosts < Ha, Hb, Hc, ..., Hm >, we can always decompose them into n hosts < Ha, Hb, Hc, ..., Hm >, we can always decompose them into n
one-to-group communications as < ha, Ha, Hb, Hc, ..., Hm >, < hb, Ha, one-to-group communications as < ha, Ha, Hb, Hc, ..., Hm >, < hb, Ha,
Hb, Hc, ..., Hm >, <hc, Ha, Hb, Hc, ..., Hm >, ..., < hn, Ha, Hb, Hc, Hb, Hc, ..., Hm >, <hc, Ha, Hb, Hc, ..., Hm >, ..., < hn, Ha, Hb, Hc,
..., Hm >. ..., Hm >.
4. Spatial metrics definitions 4. Spatial vectors metrics definitions
Spatial decomposition metrics are based on standard end-to-end This section defines vectors for the decomposition of end-to-end
metrics. singleton metrics over a path.
The definition of a spatial metric is coupled with the corresponding Spatial vectors metrics are based on the decomposition of standard
end-to-end metric. The methodology is based on the measure of the end-to-end metrics defined by the IPPM WG in [RFC2679], [RFC2680],
same test packet and parameters of the corresponding end-to-end [RFC3393] and [RFC3432].
metric.
Definitions are coupled with the corresponding end-to-end metrics.
Methodology specificities are common to all the vectors defined and
are consequently discussed in a common section.
4.1. A Definition for Spatial One-way Delay Vector 4.1. 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.
When a parameter from section 3 of [RFC2679] is first used in this When a parameter from section 3 of [RFC2679] is first used in this
section, it will be tagged with a trailing asterisk. section, it will be 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.
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Following we adapt some of them and introduce points specific to Following we adapt some of them and introduce points specific to
spatial measurement. spatial measurement.
4.1.1. Metric Name 4.1.1. Metric Name
Type-P-Spatial-One-way-Delay-Vector Type-P-Spatial-One-way-Delay-Vector
4.1.2. Metric Parameters 4.1.2. Metric Parameters
+ Src*, the IP address of the sender. o Src*, the IP address of the sender.
+ Dst*, the IP address of the receiver. o Dst*, the IP address of the receiver.
+ i, An integer which ordered the hosts in the path. o i, An integer if the list <1,2,...,n> which ordered the hosts in
the path.
+ Hi, exchange points of the path digest. o Hi, A host* of the path digest.
+ T*, a time, the sending (or initial observation) time for o T*, a time, the sending (or initial observation) time for a
a measured packet. measured packet.
+ dT* a delay, the one-way delay for a measured packet. o dT* a delay, the one-way delay for a measured packet.
+ dT1,..., dTn a list of delay. o <dT1,..., dTn> a list of delay.
+ P*, the specification of the packet type. o P*, the specification of the packet type.
+ <Src, H1, H2,..., Hn, Dst>, a path digest. o <H1, H2,..., Hn>, hosts path digest.
4.1.3. Metric Units 4.1.3. Metric Units
A sequence of times. A sequence of times.
4.1.4. Definition 4.1.4. Definition
Given a Type-P packet sent by the sender Src at wire-time (first bit) Given a Type-P packet sent by the sender Src at wire-time (first bit)
T to the receiver Dst in the path <H1, H2,..., Hn>. Given the T to the receiver Dst in the path <H1, H2,..., Hn>. Given the
sequence of values <T+dT1,T+dT2,...,T+dTn,T+dT> such that dT is the sequence of values <T+dT1,T+dT2,...,T+dTn,T+dT> such that dT is the
skipping to change at page 12, line 16 skipping to change at page 13, line 23
never passes Hi. never passes Hi.
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>.
4.1.5. Discussion 4.1.5. Discussion
Following are specific issues which may occur: Following are specific issues which may occur:
o the delay looks to decrease: dTi > DTi+1. this seem typically du o the delay looks to decrease: dTi > DTi+1. This seem typically du
to some clock synchronisation issue. this point is discussed in to some clock synchronisation issue. This point is discussed in
the section 3.7.1. "Errors or uncertainties related to Clocks" of the section 3.7.1. "Errors or uncertainties related to Clocks" of
of [RFC2679]; of [RFC2679]. One consequence of these uncertainties is that
times of a measure at different hosts shall not be used to order
hosts on the path of a measure;
o The location of the point of interest in the device influences the o The location of the point of interest in the device influences the
result. If the packet is not observed on the input interface the result. If the packet is not observed on the input interface the
delay includes buffering time and consequently an uncertainty due delay includes buffering time and consequently an uncertainty due
to the difference between 'wire time' and 'host time'; to the difference between 'wire time' and 'host time';
4.1.6. Interference with other test packet 4.2. A Definition for Spatial One-way Packet Loss Vector
To avoid packet collision it is preferable to include a sequence This section is coupled with the definition of Type-P-One-way-Packet-
number in the packet. Loss. Then when a parameter from the section 2 of [RFC2680] is first
used in this section, it will be tagged with a trailing asterisk.
4.1.7. loss threshold Sections 2.5 to 2.8 of [RFC2680] give requirements and applicability
statements for end-to-end one-way-Packet-Loss measurements. They are
applicable to each point of interest Hi involved in the measure.
Spatial packet loss measurement SHOULD be respectful of them,
especially those related to methodology, clock, uncertainties and
reporting.
To determine if a dTi is defined or undefined it is necessary to Following we define the spatial metric, then we adapt some of the
define a period of time after which a packet is considered loss. points above and introduce points specific to spatial measurement.
4.1.8. Methodologies 4.2.1. Metric Name
Section 3.6 of [RFC2679] gives methodologies for end-to-end one-way- Type-P-Spatial-One-way-Packet-Loss-Vector
delay measurements. Most of them apply to each points interest Hi
and are relevant to this section.
Generally, for a given Type-P, in a given Hi, the methodology would 4.2.2. Metric Parameters
proceed as follows:
o At each Hi, prepare to capture the packet sent a time T, take a + Src*, the IP address of the sender.
timestamp Ti', determine the internal delay correction dTi',
extract the timestamp T from the packet, then compute the one-way-
delay from Src to Hi: dTi = Ti' - dTi' - T. The one-way delay is
undefined (infinite) if the packet is not detected after the 'loss
threshold' duration;
o Gather the set of dTi of each Hi and order them according to the
path to build the Type-P-Spatial-One-way-Delay-Vector metric
<T,dT1,dT2,...,dTn,dT> over the path <H1, H2,..., Hn>.
It is out of the scope of this document to define how each Hi detects + Dst*, the IP address of the receiver.
the packet.
4.1.9. Reporting the metric + i, An integer which ordered the hosts in the path.
Section 3.6 of [RFC2679] indicates the items to report. + Hi, exchange points of the path digest.
4.1.10. Path + T*, a time, the sending (or initial observation) time for
a measured packet.
It is clear that a end-to-end Type-P-One-way-Delay can't determine + dT1,..., dTn, dT, a list of delay.
the list of hosts the packet passes through. Section 3.8.4 of
[RFC2679] says that the path traversed by the packet SHOULD be
reported but is practically impossible to determine.
This part of the job is provide by Type-P-Spatial-One-way-Delay- + P*, the specification of the packet type.
Vector metric because each points of interest Hi which capture the
packet is part of the path.
4.2. A Definition of a sample of One-way Delay of a sub path + <SH1, H2,..., Hn>, hosts path digest.
This metric is similar to the metric Type-P-One-way-Delay-Poisson- + B1, B2, ..., Bi, ..., Bn, a list of Boolean values.
stream defined in [RFC2679] and to the metric Type-P-One-way-Delay-
Periodic-Stream defined in [RFC3432].
Nevertheless its definition differs because it is based of the 4.2.3. Metric Units
division of end-to-end One-way delay using the metric Type-P-Spatial-
One-way-Delay-Vector defined above.
It aims is to define a sample of One-way-Delay between a pair of A sequence of Boolean values.
hosts of a path usable by active and passive measurements.
Sections 3.5 to 3.8 of [RFC2679] give requirements and applicability 4.2.4. Definition
statements for end-to-end one-way-delay measurements. They are
Given a Type-P packet sent by the sender Src at time T to the
receiver Dst in the path <H1, H2, ..., Hn>. Given the sequence of
times <T+dT1,T+dT2,...,T+dTn,T+dT> the packet passes <H1, H2 ..., Hn,
Dst>,
Type-P-One-way-Packet-Lost-Vector metric is defined as the sequence
of values <B1, B2, ..., Bn> such that for each Hi of the path, a
value of Bi of 0 means that dTi is a finite value, and a value of 1
means that dTi is undefined.
4.2.5. Discussion
Following are specific issues which may occur:
o the result includes the sequence 1,0. This case means that the
packet was seen by a host but not by it successor on the path;
The location of the point of interest in the device influences the
result:
o Even if the packet is received by a host, it may be not observed
by the point of interest located after a buffer;
4.3. A Definition for Spatial One-way Ipdv Vector
This section uses parameters from the definition of Type-P-One-way-
ipdv. When a parameter from section 2 of [RFC3393] is first used in
this section, it will be tagged with a trailing asterisk.
Following we adapt some of them and introduce points specific which
are to spatial measurement.
4.3.1. Metric Name
Type-P-Spatial-One-way-ipdv-Vector
4.3.2. Metric Parameters
+ Src*, the IP address of the sender.
+ Dst*, the IP address of the receiver.
+ i, An integer which ordered the hosts in the path.
+ Hi, exchange points of the path digest.
+ T1*, the time the first packet was sent.
+ T2*, the time the second packet was sent.
+ P, the specification of the packet type.
+ P1, the first packet sent at time T1.
+ P2, the second packet sent at time T2.
+ <H1, H2,..., Hn>, host path digest.
+ <T1,dT1.1, dT1.2,..., dT1.n,dT1>,
the Type-P-Spatial-One-way-Delay-Vector for packet sent at
time T1;
+ <T2,dT2.1, dT2.2,..., dT2.n,dT2>,
the Type-P-Spatial-One-way-Delay-Vector for packet sent at
time T2;
+ 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 is taken MUST
all be of the same length.
4.3.3. Metric Units
A sequence of times.
4.3.4. Definition
Given the Type-P packet having the size L and sent by the sender Src
at wire-time (first bit) T1 to the receiver Dst in the path <H1,
H2,..., Hn>.
Given the Type-P packet having the size L and sent by the sender Src
at wire-time (first bit) T2 to the receiver Dst in the same path.
Given the Type-P-Spatial-One-way-Delay-Vector <T1,dT1.1, dT1.2,...,
dT1,n,dT1> of the packet P1.
Given the Type-P-Spatial-One-way-Delay-Vector <T2,dT2.1, dT2.2,...,
dT2,n,dT2> of the packet P2.
Type-P-Spatial-One-way-ipdv-Vector metric is defined as the sequence
of values <T2-T1,dT2.1-dT1.1,dT2.2-dT1.2,...,dT2.n-dT1.n,dT2-dT1>
Such that for each Hi of the path <H1, H2,..., Hn>, dT2.i-dT1.i is
either a real number if the packets P1 and P2 passes Hi at wire-time
(last bit) dT1.i, respectively dT2.i, or undefined if at least one of
them never passes Hi. T2-T1 is the inter-packet emission interval
and dT2-dT1 is ddT* the Type-P-One-way-ipdv at T1,T2*.
4.4. Spatial Methodology
Methodology, reporting and uncertainties points specified in section
3 of [RFC2679][RFC2679] applies to each point of interest Hi
measuring a element of a spatial delay vector.
Methodology, reporting and uncertainties points specified in section
2 of [RFC2680][RFC2680] applies to each point of interest Hi
measuring a element of a spatial packet loss vector.
Sections 3.5 to 3.7 of [RFC3393] give requirements and applicability
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.
Subpath one-way-delay measurement SHOULD be respectful of them, Spatial One-way ipdv measurement SHOULD be respectful of methodology,
especially those related to methodology, clock, uncertainties and clock, uncertainties and reporting aspects given in this section.
reporting.
4.2.1. Metric Name Passive and active measurement approaches of the metrology are
considered as orthogonal. Active measure differs mainly from passive
measure by the knowledge of the time the packet was send by the
source and received by the destination, making the RFC2330 framework
difficults to apply to passive measurement. On the other hand,
spatial metrics rely on passive observation of the packets involved
in the measure.
Type-P-subpath-One-way-Delay-Stream In fact each approach compliments the other setting the base of
spatial measurement methodology: Active points of interest provide
information observed at the source and at the destination while
Passive points of interests provide information observed at
intermediary hosts of the path.
4.2.2. Metric Parameters Generally, for a given Type-P of length L, in a given Hi, the
methodology for spatial vector metrics would proceed as follows:
o At each Hi, points of interest prepare to capture the packet sent
a time T, take a timestamp Ti', determine the internal delay
correction dTi' (See section 3.7.1. "Errors or uncertainties
related to Clocks" of [RFC2679]),
o Each Hi extracts the path ordering information from the packet
(e.g. time-to-live);
o Each Hi compute the wiretime from Src to Hi: Ti = Ti' - dTi'.
This arrival time is undefined (infinite) if the packet is not
detected after the 'loss threshold' duration;
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 The reference point gathers the result and time-to-live of each Hi
and order them according to the path to build the Type-P-Spatial-
One-way-Delay-Vector metric <T,dT1,dT2,...,dTn,dT> over the path
<Src,H1, H2,..., Hn, Dst>.
4.4.1. Loss threshold
Loss threshold is the centrality of any methodology because it
determines the presence the packet in the measurement process of the
point of interest and consequently determines any ground truth metric
result. It determines the presence of an effective delay, and bias
the measure of ipdv, of packet loss and of the statistics.
This is consistent for end-to-end but impacts spatial measure:
depending on the consistency of the Loss threshold among the points
of interest, a packet may be considered loss a one host but present
in another one, or may be observed by the last host (last hop) of the
path but considered lost by Dst. The analysis of such results is not
deterministic: has the path change? Does the packet arrive at
destination or was it lost during the last mile? The same applies,
of course, for one-way-delay measures: a delay measured may be
infinite at one host but a real value in another one, or may be
measured as a real value by the last host of the path but observed as
infinite by Dst. The Loss threshold should be set up with the same
value in each host of the path and in the destination. The Loss
threshold must be systematically reported to permit careful
introspection and to avoid the introduction of any contradiction in
the statistic computation process.
4.4.2. Host Path Digest
The methodology given above adds the order of the points of interest
over the path to [RFC2679] one's.
A perfect Host Path Digest (hum! of cource from the measurement point
of view only, that is, corresponding to the real path the test packet
experimented) may include several times several hosts:
o <Ha,..., Ha> coresponds to a loop in the path;
o <Ha,..,Hb,..., Ha,...,Hb> coresponds to a loop in the path which
may occurs during rerouting phases;
These cases MUST be identified before statistics computation to avoid
corrupted results' production. This applies especially to the
measure of segments which are build from results of a measure of a
vector metric.
5. Spatial Segments metrics definitions
This section defines samples to measure a sequence of delays, a
sequence of lost and a sequence of ipdv between 2 hosts of the path,
a segment. Singletons are taken from segments of vectors defined
above.
5.1. A Definition of a sample of One-way Delay of a segment of the path
This metric defines a sample of One-way delays between a pair of
hosts of a path.
5.1.1. Metric Name
Type-P-Segment-One-way-Delay-Stream
5.1.2. Metric Parameters
+ Src*, the IP address of the sender. + Src*, the IP address of the sender.
+ Dst*, the IP address of the receiver. + Dst*, the IP address of the receiver.
+ P*, the specification of the packet type;
+ i, An integer which orders exchange points in the path. + i, An integer which orders exchange points in the path.
+ k, An integer which orders the packets sent. + k, An integer which orders the packets sent.
+ <Src, H1, H2,..., Hn, Dst>, a path digest. + Hi, a host of the path digest;
+ <H1, H2,..., Hn>, host path digest.
+ Ha, a host of the path digest different from Dst and Hb; + Ha, a host of the path digest different from Dst and Hb;
+ Hb, a host of the path digest different from Src and Ha. + Hb, a host of the path digest different from Src and Ha.
Hb order in the path must greater that Ha; Hb order in the path must greater that Ha;
+ Hi, exchange points of the path digest. + <T1, ..., Tk>, a list of time ordered by k;
+ dT1,..., dTn a list of delay.
+ P*, the specification of the packet type.
4.2.3. Metric Units
A sequence of pairs <Tk,dt>. + dT1,..., dTn a list of delay;
T is one of time of the sequence T1...Tn; 5.1.3. Metric Units
dt is a delay. A sequence of delay
4.2.4. Definition 5.1.4. Definition
Given 2 hosts Ha and Hb of the path <Src, H1, H2,..., Hn, Dst>, given Given 2 hosts Ha and Hb of the path <Src, H1, H2,..., Hn, Dst>, given
a flow of packets of Type-P sent from Src to Dst at the times T1, a flow of packets of Type-P sent from Src to Dst at the times T1,
T2... Tn. At each of these times, we obtain a Type-P-Spatial-One- T2... Tn. At each of these times, we obtain a Type-P-Spatial-One-
way-Delay-Vector <T1,dT1.1, dT1.2,..., dT1.n,dT1>. We define the way-Delay-Vector <T1,dT1.a, ..., dT1.b,...,, dT1.n,dT1>. We define
value of the sample Type-P-subpath-One-way-Delay-Stream as the the value of the sample Type-P-segment-One-way-Delay-Stream as the
sequence made up of the couples <Tk,dTk.b - dTk.a>. dTk.a is the sequence made up of the delays dTk.b - dTk.a. dTk.a is the delay
delay between Src and Ha. dTk.b is the delay between Src and Hb. between Src and Ha. dTk.b is the delay between Src and Hb. 'dTk.b -
'dTk.b - dTk.a' is the one-way delay experienced by the packet sent dTk.a' is the one-way delay experienced by the packet sent by Src at
at the time Tk by Src when going from Ha to Hb. the time Tk when going from Ha to Hb.
4.2.5. Discussion 5.1.5. Discussion
Following are specific issues which may occur: Following are specific issues which may occur:
o When a is Src <Tk,dTk.b - dTk.a> is the measure of the first hop. o When a is Src <Tk,dTk.b - dTk.a> is the measure of the first hop.
o When b is Dst <Tk,dTk.b - dTk.a> is the measure of the last hop. o When b is Dst <Tk,dTk.b - dTk.a> is the measure of the last hop.
o the delay looks to decrease: dTi > DTi+1: o the delay looks to decrease: dTi > DTi+1:
* This is typically du to clock synchronisation issue. this point * This is typically du to clock synchronisation issue. this point
skipping to change at page 15, line 40 skipping to change at page 21, line 40
o dTk.b may be observed and not dTk.a. o dTk.b may be observed and not dTk.a.
o Tk is unknown if the flow is made of end user packets, that is o Tk is unknown if the flow is made of end user packets, that is
pure passive measure. In this case Tk may be forced to Tk+dTk.a. pure passive measure. In this case Tk may be forced to Tk+dTk.a.
This motivate separate metrics names for pure passive measurement This motivate separate metrics names for pure passive measurement
or specific reporting information. or specific reporting information.
o Pure passive measure should consider packets of the same size and o Pure passive measure should consider packets of the same size and
of the same Type-P. of the same Type-P.
4.2.6. Interference with other packet 5.2. A Definition of a sample of Packet Loss of a segment of the path
4.2.7. loss threshold
To determine if a dTi is defined or undefined it is necessary to
define a period of time after which a packet is considered loss.
4.2.8. Methodologies
Both active and passive method should discussed.
4.2.9. Reporting the metric
Section 3.6 of [RFC2679] indicates the items to report.
4.2.10. Path
4.3. A Definition for Spatial One-way Packet Loss Vector
This section is coupled with the definition of Type-P-One-way-Packet-
Loss. Then when a parameter from the section 2 of [RFC2680] is first
used in this section, it will be tagged with a trailing asterisk.
Sections 2.5 to 2.8 of [RFC2680] give requirements and applicability
statements for end-to-end one-way-Packet-Loss measurements. They are
applicable to each point of interest Hi involved in the measure.
Spatial packet loss measurement SHOULD be respectful of them,
especially those related to methodology, clock, uncertainties and
reporting.
Following we define the spatial metric, then we adapt some of the This metric defines a sample of Packet lost between a pair of hosts
points above and introduce points specific to spatial measurement. of a path.
4.3.1. Metric Name 5.2.1. Metric Name
Type-P-Spatial-One-way-Packet-Loss-Vector Type-P-segment-Packet-loss-Stream
4.3.2. Metric Parameters 5.2.2. Metric Parameters
+ Src*, the IP address of the sender. + Src*, the IP address of the sender.
+ Dst*, the IP address of the receiver. + Dst*, the IP address of the receiver.
+ i, An integer which ordered the hosts in the path.
+ Hi, exchange points of the path digest.
+ T*, a time, the sending (or initial observation) time for
a measured packet.
+ dT1,..., dTn, dT, a list of delay.
+ P*, the specification of the packet type. + P*, the specification of the packet type.
+ <Src, H1, H2,..., Hn, Dst>, a path digest. + k, An integer which orders the packets sent.
+ B1, B2, ..., Bi, ..., Bn, a list of Boolean values.
4.3.3. Metric Units + n, An integer which orders the hosts on the path.
A sequence of Boolean values. + <H1, H2,..., Hn>, hosts path digest.
4.3.4. Definition + Ha, a host of the path digest different from Dst and Hb;
Given a Type-P packet sent by the sender Src at time T to the + Hb, a host of the path digest different from Src and Ha.
receiver Dst in the path <H1, H2, ..., Hn>. Given the sequence of Hb order in the path must greater that Ha;
times <T+dT1,T+dT2,...,T+dTn,T+dT> the packet passes <H1, H2 ..., Hn,
Dst>,
Type-P-One-way-Packet-Lost-Vector metric is defined as the sequence + Hi, exchange points of the path digest.
of values <B1, B2, ..., Bn> such that for each Hi of the path, a
value of Bi of 0 means that dTi is a finite value, and a value of 1
means that dTi is undefined.
4.3.5. Discussion + <B1, B2, ..., Bn> a list of bits.
Following are specific issues which may occur: + <L1, L2, ..., Ln> a list of integers.
o the result includes the sequence 1,0. This case means that the 5.2.3. Metric Units
packet was seen by a host but not by it successor on the path;
o A sequence of integers <L1, L2,..., Lk>
The location of the meter in the device influences the result: 5.2.4. Definition
o Even if the packet is received by a device, it may be not observed Given 2 hosts Ha and Hb of the path <Src, H1, H2,..., Hn, Dst>, given
by a meter located after a buffer; a flow of packets of Type-P sent from Src to Dst at the times T1,
T2... Tn. At each of these times, we obtain a Type-P-Spatial-
Packet-Lost-Vector <B1.1, B1.2,..., B1.n>. We define the value of
the sample Type-P-segment-Packet-Lost-Stream between Ha and Hb as the
sequence made up of the integer <L1, L2,..., Lk> such that for each
Tk:
4.3.6. Reporting o a value of Lk of 0 means that Bk.a has a value of 0 (observed) and
that Bk.b have a value of 0 (observed);
Section in progress. o a value of Lk of 1 means that Bk.a has a value of 0 (observed) and
that Bk.b have a value of 1 (not observed);
4.4. A Definition for Spatial One-way Jitter Vector o a value of Lk of 2 means that Bk.a has a value of 1 (not observed)
and that Bk.b have a value of 0 (observed);
o a value of Lk of 3 means that Bk.a has a value of 1 (not observed)
and that Bk.b have a value of 1 (not observed).
This section uses parameters from the definition of Type-P-One-way- 5.2.5. Discussion
ipdv. When a parameter from section 2 of [RFC3393] is first used in
this section, it will be tagged with a trailing asterisk.
Sections 3.5 to 3.7 of [RFC3393] give requirements and applicability The semantic of a Type-P-segment-Packet-loss-Stream is similar to the
statements for end-to-end one-way-ipdv measurements. They are one of Type-P-Packet-loss-Stream:
applicable to each point of interest Hi involved in the measure.
Spatial one-way-ipdv measurement SHOULD be respectful of them,
especially those related to methodology, clock, uncertainties and
reporting.
Following we adapt some of them and introduce points specific to o a value of 0 means that the packet was observed by Ha (similar to
spatial measurement. 'send by Src') and not observed by Hb ( similar to 'not received
by Dst');
4.4.1. Metric Name o a value of 1 means that it was observed by Ha (similar to 'send by
Src') and observed by Hb ( similar to 'received by Dst').
Type-P-Spatial-One-way-Jitter-Vector This definition of Type-P-segment-Packet-loss-Stream is similar to
the Type-P-Packet-loss-Stream defined in [RFC2680] excepted that in a
Type-P-segment-Packet-loss-Stream the rules of the point of interests
Ha and Hb are symetrical: The asumption that a set of packets are
going from Ha to Hb does not apply to Type-P-segment-Packet-loss-
Stream because as the host path digest is dynamic each packet has its
own host path digest.
4.4.2. Metric Parameters Making the asumption that the host path digest of a Type-P-spatial-
Packet-loss-vector does not change and that the set of (Hk, Hk+1)
tuples is mostly stable over time lead to unusable results and to the
introduction of mistakes in the metrics aggregation processes. The
right approach consists in carefully scrutening the path ordering
information to build sample with elements of vectors sharing the same
properties in term of Ha and Hb and 'Ha to Hb'. So a measure of
Type-P-spatial-Packet-loss-vector differs from a Type-P-Packet-loss
one in that it produces different samples of packet loss over time.
+ Src*, the IP address of the sender. The semantic of a Type-P-segment-Packet-loss-Stream defines 2 new
results:
+ Dst*, the IP address of the receiver. o A value of Lk of 2 (1,0) corresponds to a mistake in the ordering
of Ha and Hb over the path coming either from the configuration
(asumption on the path) or from the processing of the vectors: bad
scrutening of the path ordering information, or some other mistake
in the measure or the reporting. It is not in the scope of this
document to go in further details which are mostly implementation
dependent. This value MUST not be used to compute packet lost
statistics.
+ i, An integer which ordered the hosts in the path. o A value of Lk of 3 (1,1) corresponds to a lost of the packet in
upper segment of the path.
+ Hi, exchange points of the path digest. 5.3. A Definition of a sample of One-way Ipdv of a segment of the path
+ T1*, the time the first packet was sent. This metric defines a sample of ipdv between a pair of hosts of a
path.
+ T2*, the time the second packet was sent. Editor note: work in progress
+ P, the specification of the packet type. 5.3.1. Metric Name
+ P1, the first packet sent at time T1. Type-P-Segment-Ipdv-Stream
+ P2, the second packet sent at time T2. 5.3.2. Metric Parameters
+ <Src, H1, H2,..., Hn, Dst>, a path digest. 5.3.3. Metric Units
+ <T1,dT1.1, dT1.2,..., dT1.n,dT1>, 5.3.4. Definition
the Type-P-Spatial-One-way-Delay-Vector for packet sent at
time T1;
+ <T2,dT2.1, dT2.2,..., dT2.n,dT2>, 5.3.5. Discussion
the Type-P-Spatial-One-way-Delay-Vector for packet sent at
time T2;
+ L*, a packet length in bits. The packets of a Type P 5.4. Discussion on Passive Segment Metrics
packet stream from which the
Type-P-Spatial-One-way-Delay-Vector metric is taken MUST
all be of the same length.
4.4.3. Metric Units A pure passive spatial measure is the measure of a spatial metric
based on the observation of user traffic instead of packets dedicated
to the measure.
A sequence of times. This section discusses the applicability of pure passive measurement
methodology (e.g. without injecting test traffic as described by
PSAMP documents [draft-ietf-psamp-sample-tech-10.txt]) to measure
spatial metrics.
4.4.4. Definition To permit comparison and discussion, we firstly define pure passive
measurement methodology following the spirit of IPPM framework
[RFC2330] and the methodology of [RFC2679]. Then we propose several
passive metrics complying to this framework.
Given the Type-P packet having the size L and sent by the sender Src 5.4.1. A methodololy for passive segment metrics
at wire-time (first bit) T1 to the receiver Dst in the path <H1,
H2,..., Hn>.
Given the Type-P packet having the size L and sent by the sender Src The following starts from the point that the time a packet is sent is
at wire-time (first bit) T2 to the receiver Dst in the same path. not needed to measure the delay from one host Ha of the path to
another host Hb.
Given the Type-P-Spatial-One-way-Delay-Vector <T1,dT1.1, dT1.2,..., Generally, for the packets of Type-P and length L sent a time <T1,
dT1,n,dT1> of the packet P1. T2,..., Tn> by the source Src pure passive methodology might proceed
as follows:
Given the Type-P-Spatial-One-way-Delay-Vector <T2,dT2.1, dT2.2,..., o Each point of interest Ha and Hb prepares to capture these
dT2,n,dT2> of the packet P2. packets;
o Each point of interest Ha and Hb takes a timestamp Ti', determines
the internal delay correction dTi' (See section 3.7.1. "Errors or
uncertainties related to Clocks" of [RFC2679]),
Type-P-Spatial-One-way-Jitter-Vector metric is defined as the o Each points of interest Ha and Hb extracts the path ordering
sequence of values <T2-T1,dT2.1-dT1.1,dT2.2-dT1.2,...,dT2.n- information from the packet (e.g. time-to-live)
dT1.n,dT2-dT1> Such that for each Hi of the path <H1, H2,..., Hn>,
dT2.i-dT1.i is either a real number if the packets P1 and P2 passes
Hi at wire-time (last bit) dT1.i, respectively dT2.i, or undefined if
at least one of them never passes Hi. T2-T1 is the inter-packet
emission interval and dT2-dT1 is ddT* the Type-P-One-way-ipdv at
T1,T2*.
4.4.5. Sections in progress o Each points of interest Ha and Hb computes the wiretime fSrom Src
to Hi: Ti = Ti' - dTi'. ;
See sections 3.5 to 3.7 of [RFC3393]. o The reference point gathers individual information for the packets
sent a time <T1, T2,..., Tn> from each point of interest Ha and Hb
and proceeds as follow:
4.5. Pure Passive Metrics * Orders them according to the path ordering information;
Spatial metrics may be measured without injecting test traffic. * Extracts the timestamps Ti.a and Ti+1.b. This arrival time is
undefined (infinite) if the packet is not detected;
4.5.1. Discussion on Passive measurement * Computes the one-way-delay from Ha to Hb as (Ti+1.b - Ti.a).
The delay is undefined (infinite) if the packet is not detected
in Ha or Hb;
One might says that most of the operational issues occur in the last o The reference point builds the segment sample <T1.b - T1.a, T2.b -
mile and that consequently such measure are less useful than active T2.a,..., Tn.b - Tn.a> from Ha to Hb;
measurement. Nevertheless they are usable for network TE and
interdomain QoS monitoring, and composition of metric.
Such a technique have some limitations that are discussed below. 5.4.2. Discussion on passive methodololy
4.5.1.1. Passive One way delay Intrinsically passive methodololy does not known (neither in the
points of interest nor in the point of reference) the time each
packet is sent <T1, T2,..., Tn> and the time each packet it received.
As the packet is not a test packet, it does not include the time it Section 5.4.1 shows that a passive segment one-way delay measure does
was sent. not rely on the time T the packet is sent to compute the delay from a
host Ha to a host Hb.
Consequently a point of interest Hi ignores the time the packet was Intuitively, packets loss measurement does not require any time
send. So It is not possible to measure the delay between Src and Hi information and only expects the packet was sent. Passive packet
in the same manner it is not possible to measure the delay betwwen Hi loss methodology relies on the detection of the packet by one point
and Dst. of interest and not by another. This relies on asumptions similar to
spatial methodology:
4.5.1.2. Passive Packet loss o The knowledge of the path and the order of the points of interest
over the path;
The packet is not a test packet, so it does not include a sequence o The packet is observed by one point of interest and not by
number. another;
Nevertheless, passive packet loss measure is limited by the fact that
information that neither a packet has be sent nor that the packet was
received is never available:
Packet lost measurement doe not require time synchronization and when the path changes and the packet is not observed it is not
require only one point of observation. Nevertheless it requires the deterministic to state that the packet is lost because the measure
point of interest Hi to be expecting the packet. Practically Hi may does not known that the packet is received by Dst.
not detect a lost of packet that occurs between Src and Hi.
A point of interest Hi ignores the time the packet is send because when the measure does not observe any packets it is not possible
the packet does not carry the time it was injected in the network. to state that all packets are lost because the measure does not
So a probe Hi can not compute dTi. known that any packets were sent.
An alternative to these issues consist in considering sample spatial The drawback is that monitoring finely these events is crucial for
One-way delay that T is the time when H1 (the first passive probe of troubleshooting workflow.
the path) observed the packet.
4.5.2. Reporting and composition IPPM framework relies on the mesure of the behavior of packets of the
same size. Consequently a passive metric sample MUST not mix
information of packets of different sizes.
To avoid misunderstanding and to address specific reporting Segment metrics may be measured using pure passive technics. Passive
constraint a proposal consists in defining distinct metrics for pure segment metrics definitions are very closed to spatial segment
passive measurement based on the definition above. metrics definitions. Therefore below we just name passive segment
metrics to distinguish the methodology used. Having distinct metrics
identifiers for spatial metrics and passive spatial metrics in the
[RFC4148] will avoid interoperability issues especially during
composition of metrics the IPPM WG is currently defining.
It is crucial to know the methodologies used because of the 5.4.3. Passive Segment metrics
difference of method of detection (expecting Seq++); because of the
difference of source of time (H1 vs Src) and because of the
difference of behaviour of the source (Poisson/unknown).
4.5.3. naming and registry 5.4.3.1. Passive Segment One way Delay metric
Having distinct metrics identifiers for spatial metrics and passive This metric definition is based on the top of the Type-P-spatial-
spatial metrics in the [RFC4148] will avoid interoperability issues segment-One-way-Delay-Stream metric definition.
especially during composition of metrics.
4.5.4. Passive One way delay metrics name: Type-P-Passive-Segment-One-way-Delay-Stream
4.5.5. Passive One way PacketLoss metrics 5.4.3.2. Passive Segment Packet Loss metric
4.5.6. Passive One way jitter metrics This metric definition is based on the top of the Type-P-spatial-
segment-Packet-Loss-Stream metric definition.
4.6. Discussion on spatial statistics name: Type-P-Passive-Segment-Packet-Loss-Stream
Do we define min, max, avg of spatial metrics ? 5.4.3.3. Passive Segment One-way Ipdv metric
having the maximum loss metric value could be interesting. Say, This metric definition is based on the top of the Type-P-Segment-
the segment between router A and B always contributes loss metric Ipdv-Stream metric definition.
value of "1" means it could be the potential problem segment.
Uploading dTi of each Hi consume a lot of bandwidth. Computing name: Type-P-Passive-Segment-One-way-Ipdv-Stream
statistics (min, max and avg) of dTi locally in each Hi reduce the
bandwidth consumption.
5. One-to-group metrics definitions 6. One-to-group metrics definitions
5.1. A Definition for one-to-group One-way Delay 6.1. A Definition for one-to-group One-way Delay
5.1.1. Metric Name 6.1.1. Metric Name
Type-P-one-to-group-One-way-Delay-Vector Type-P-one-to-group-One-way-Delay-Vector
5.1.2. Metric Parameters 6.1.2. 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 time. o dT1,...,dTn a list of time.
o P, the specification of the packet type. o P, the specification of the packet type.
o Gr, the multicast group address (optional). The parameter Gr is o Gr, the multicast group address (optional). The parameter Gr is
the multicast group address if the measured packets are the multicast group address if the measured packets are
transmitted by multicast. This parameter is to identify the transmitted by multicast. This parameter is to identify the
measured traffic from other unicast and multicast traffic. It is measured traffic from other unicast and multicast traffic. It is
set to be optional in the metric to avoid losing any generality, set to be optional in the metric to avoid losing any generality,
i.e. to make the metric also applicable to unicast measurement i.e. to make the metric also applicable to unicast measurement
where there is only one receivers. where there is only one receivers.
5.1.3. Metric Units 6.1.3. Metric Units
The value of a Type-P-one-to-group-One-way-Delay-Vector is a set of The value of a Type-P-one-to-group-One-way-Delay-Vector is a set of
singletons metrics Type-P-One-way-Delay [RFC2679]. singletons metrics Type-P-One-way-Delay [RFC2679].
5.1.4. Definition 6.1.4. Definition
Given a Type P packet sent by the source Src at Time T, given the N Given a Type P packet sent by the source Src at Time T, given 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 }, a Type-P-one-to-group-One-way-Delay-Vector is T+dT1,...,T+dTn }, a Type-P-one-to-group-One-way-Delay-Vector is
defined as the set of the Type-P-One-way-Delay singleton between Src defined as the set of the Type-P-One-way-Delay singleton between Src
and each receiver with value of { dT1, dT2,...,dTn }. and each receiver with value of { dT1, dT2,...,dTn }.
5.2. A Definition for one-to-group One-way Packet Loss 6.2. A Definition for one-to-group One-way Packet Loss
5.2.1. Metric Name 6.2.1. Metric Name
Type-P-one-to-group-One-way-Packet-Loss-Vector Type-P-one-to-group-One-way-Packet-Loss-Vector
5.2.2. Metric Parameters 6.2.2. 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 T1,...,Tn a list of time. o T1,...,Tn a list of time.
o P, the specification of the packet type. o P, the specification of the packet type.
o Gr, the multicast group address (optional). o Gr, the multicast group address (optional).
5.2.3. Metric Units 6.2.3. Metric Units
The value of a Type-P-one-to-group-One-way-Packet-Loss-Vector is a The value of a Type-P-one-to-group-One-way-Packet-Loss-Vector is a
set of singletons metrics Type-P-One-way-Packet-Loss [RFC2680]. set of singletons metrics Type-P-One-way-Packet-Loss [RFC2680].
5.2.4. Definition 6.2.4. 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, which should receive the packet at T1,...,Tn, a Recv1,...,RecvN, which should receive the packet at T1,...,Tn, a
Type-P-one-to-group-One-way-Packet-Loss-Vector is defined as a set of Type-P-one-to-group-One-way-Packet-Loss-Vector is defined as a set of
the Type-P-One-way-Packet-Loss singleton between Src and each of the the Type-P-One-way-Packet-Loss singleton between Src and each of the
receivers {<T1,0|1>,<T2,0|1>,..., <Tn,0|1>}. receivers {<T1,0|1>,<T2,0|1>,..., <Tn,0|1>}.
5.3. A Definition for one-to-group One-way Jitter 6.3. A Definition for one-to-group One-way Ipdv
5.3.1. Metric Name 6.3.1. Metric Name
Type-P-one-to-group-One-way-Jitter-Vector Type-P-One-to-group-One-way-ipdv-Vector
5.3.2. Metric Parameters 6.3.2. Metric Parameters
+ Src, the IP address of a host acting as the source. + Src, the IP address of a host acting as the source.
+ Recv1,..., RecvN, the IP addresses of the N hosts acting as + Recv1,..., RecvN, the IP addresses of the N hosts acting as
receivers. receivers.
+ T1, a time. + T1, a time.
+ T2, a time. + T2, a time.
+ ddT1,...,ddTn, a list of time. + ddT1,...,ddTn, a list of time.
+ P, the specification of the packet type. + P, the specification of the packet type.
+ F, a selection function defining unambiguously the two + F, a selection function defining unambiguously the two
packets from the stream selected for the metric. packets from the stream selected for the metric.
+ Gr, the multicast group address (optional) + Gr, the multicast group address (optional)
5.3.3. Metric Units 6.3.3. Metric Units
The value of a Type-P-one-to-group-One-way-Jitter-Vector is a set of The value of a Type-P-One-to-group-One-way-ipdv-Vector is a set of
singletons metrics Type-P-One-way-ipdv [RFC3393]. singletons metrics Type-P-One-way-ipdv [RFC3393].
5.3.4. Definition 6.3.4. Definition
Given a Type P packet stream, Type-P-one-to-group-One-way-Jitter- Given a Type P packet stream, Type-P-one-to-group-One-way-ipdv-Vector
Vector is defined for two packets from the source Src to the N hosts is defined for two packets from the source Src to the N hosts
{Recv1,...,RecvN },which are selected by the selection function F, as {Recv1,...,RecvN },which are selected by the selection function F, as
the difference between the value of the Type-P-one-to-group-One-way- the difference between the value of the Type-P-one-to-group-One-way-
Delay-Vector from Src to { Recv1,..., RecvN } at time T1 and the Delay-Vector from Src to { Recv1,..., RecvN } at time T1 and the
value of the Type-P-one-to-group- One-way-Delay-Vector from Src to { value of the Type-P-one-to-group- One-way-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
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-One-way-Delay-Vector metric. from the Type-P-one-to- group-One-way-Delay-Vector metric.
Therefore, for a set of real number {ddT1,...,ddTn},Type-P-one- to- Therefore, for a set of real number {ddT1,...,ddTn},Type-P-one- to-
group-One-way-Jitter-Vector from Src to { Recv1,...,RecvN } at T1, T2 group-One-way-ipdv-Vector from Src to { Recv1,...,RecvN } at T1, T2
is {ddT1,...,ddTn} means that Src sent two packets, the first at is {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) wire-time T1 (first bit), and the second at wire-time T2 (first bit)
and the packets were received by { Recv1,...,RecvN } at wire-time and the packets were received by { Recv1,...,RecvN } at wire-time
{dT1+T1,...,dTn+T1}(last bit of the first packet), and at wire-time {dT1+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}. {dT'1-dT1,...,dT'n-dTn} ={ddT1,...,ddTn}.
6. One-to-Group Sample Statistics 7. One-to-Group Sample Statistics
The defined one-to-group metrics above can all be directly achieved The defined one-to-group metrics above can all be directly achieved
from the relevant unicast one-way metrics. They managed to collect from the relevant unicast one-way metrics. They managed to collect
all unicast measurement results of one-way metrics together in one all unicast measurement results of one-way metrics together in one
profile and sort them by receivers and packets in a multicast group. profile and sort them by receivers and packets in a multicast group.
They can provide sufficient information regarding the network They can provide sufficient information regarding the network
performance in terms of each receiver and guide engineers to identify performance in terms of each receiver and guide engineers to identify
potential problem happened on each branch of a multicast routing potential problem happened on each branch of a multicast routing
tree. However, these metrics can not be directly used to tree. However, these metrics can not be directly used to
conveniently present the performance in terms of a group and neither conveniently present the performance in terms of a group and neither
skipping to change at page 24, line 40 skipping to change at page 30, line 40
metrics to define exactly how small the relative delay the online metrics to define exactly how small the relative delay the online
gaming requires. There are many other services, e.g. online biding, gaming requires. 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 FRCs. 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 7. For a Matrix M each row is a set of One-way illustrated in Figure 9. For a Matrix M each row is a set of One-way
singletons spreading over the time dimension and each column is 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 ... R3dTk \ 1 | / R1dT1 R1dT2 R1dT3 ... R3dTk \
| | | | | |
2 | | R2dT1 R2dT2 R2dT3 ... R3dTk | 2 | | R2dT1 R2dT2 R2dT3 ... R3dTk |
| | | | | |
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 7: Matrix M (n*m) Figure 9: 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 contains the One-way delays of the same packet is a delay vector contains the One-way delays of the same packet
observed at M points of interest. It implies the geographical factor observed at M 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.
Therefore, one can either calculate statistics by rows over the space Therefore, one can either calculate statistics by rows over the space
skipping to change at page 26, line 38 skipping to change at page 32, line 38
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 either the space dimension or the time dimension or both. This
memo treats the case where a stream of packets from the Source memo treats the case where a stream of packets from the Source
results in a sample at each of the Receivers in the Group, and these results in a sample at each of the Receivers in the Group, and these
samples are each summarized with the usual statistics employed in samples are each summarized with the usual statistics employed in
one-to-one communication. New statistic definitions are presented, one-to-one communication. New statistic definitions are presented,
which summarize the one-to-one statistics over all the Receivers in which summarize the one-to-one statistics over all the Receivers in
the Group. the Group.
6.1. Discussion on the Impact of packet loss on statistics 7.1. Discussion on the Impact of packet loss on statistics
The packet loss does have effects on one-way metrics and their The packet loss does have effects on one-way metrics and their
statistics. For example, the lost packet can result an infinite one- statistics. For example, the lost packet can result an infinite one-
way delay. It is easy to handle the problem by simply ignoring the way delay. It is easy to handle the problem by simply ignoring the
infinite value in the metrics and in the calculation of the infinite value in the metrics and in the calculation of the
corresponding statistics. However, the packet loss has so strong corresponding statistics. However, the packet loss has so 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 complex of building a Matrix, which is metrics. This is due to the complex of building a Matrix, which is
needed for calculation of the statistics proposed in this memo. needed for calculation of the statistics proposed in this memo.
skipping to change at page 27, line 27 skipping to change at page 33, line 27
R1dT1 R1dT2 R1dT3 ... R1dTK-1 UNDEF R1dTK+1... R1DM } where "UNDEF" R1dT1 R1dT2 R1dT3 ... R1dTK-1 UNDEF R1dTK+1... R1DM } where "UNDEF"
is an undefined value, the reference point can replace it by R1dTK = is an undefined value, the reference point can replace it by R1dTK =
{(R1dTK-1)+( R1dTK+1)}/2. Therefore, this result can be used to {(R1dTK-1)+( R1dTK+1)}/2. Therefore, this result can be used to
build up the group Matrix with an estimated value R1dTK. There are build up the group Matrix with an estimated value R1dTK. There are
other possible solutions such as using the overall mean of the whole other possible solutions such as using the overall mean of the whole
result to replace the infinite/undefined value, and so on. It is out result to replace the infinite/undefined value, and so on. It is out
of the scope of this memo. of the scope of 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 jitter 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 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 in Figure. 8 without any packet loss and User2 calculates the R2DM
with N-2 packet loss. The R1DM and R2DM should not be treated with 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 equal weight because R2DM was calculated only based on 2 delay values
in the whole sample interval. One possible solution is to use a in the whole sample interval. One possible solution is to use a
weight factor to mark every statistic value sent by users and use weight factor to mark every statistic value sent by users and use
this factor for further statistic calculation. this factor for further statistic calculation.
6.2. General Metric Parameters 7.2. General Metric Parameters
o Src, the IP address of a host o Src, the IP address of a host
o G, the Group IP address o G, the Group IP address
o N, the number of Receivers (Recv1, Recv2, ... RecvN) o N, the number of Receivers (Recv1, Recv2, ... RecvN)
o T, a time (start of test interval) o T, a time (start of test interval)
o Tf, a time (end of test interval) o Tf, a time (end of test interval)
skipping to change at page 28, line 37 skipping to change at page 34, line 37
o dT, shorthand notation for a one-way delay singleton value o dT, shorthand notation for a one-way delay singleton value
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
6.3. One-to-Group one-way Delay Statistics 7.3. One-to-Group one-way Delay Statistics
This section defines the overall one-way delay statistics for an This section defines the overall one-way delay statistics for an
entire Group or receivers. For example, we can define the group mean entire Group or receivers. For example, we can define the group mean
delay, as illustrated below. This is a metric designed to summarize delay, as illustrated below. This is a metric designed to summarize
the entire Matrix. the whole matrix.
Recv /----------- Sample -------------\ Stats Group Stat Recv /----------- Sample -------------\ Stats Group Stat
1 R1dT1 R1dT2 R1dT3 ... R1dTk R1DM \ 1 R1dT1 R1dT2 R1dT3 ... R1dTk R1DM \
| |
2 R2dT1 R2dT2 R2dT3 ... R2dTk R2DM | 2 R2dT1 R2dT2 R2dT3 ... R2dTk R2DM |
| |
3 R3dT1 R3dT2 R3dT3 ... R3dTk R2DM > GMD 3 R3dT1 R3dT2 R3dT3 ... R3dTk R2DM > GMD
. | . |
. | . |
. | . |
n RndT1 RndT2 RndT3 ... RndTk RnDM / n RndT1 RndT2 RndT3 ... RndTk RnDM /
Figure 8: One-to-GroupGroup Mean Delay Figure 10: One-to-GroupGroup Mean Delay
where: where:
R1dT1 is the Type-P-Finite-One-way-Delay singleton evaluated at R1dT1 is the Type-P-Finite-One-way-Delay singleton evaluated at
Receiver 1 for packet 1. Receiver 1 for packet 1.
R1DM is the Type-P-Finite-One-way-Delay-Mean evaluated at Receiver 1 R1DM is the Type-P-Finite-One-way-Delay-Mean evaluated at Receiver 1
for the sample of packets (1,...K). for the sample of packets (1,...K).
GMD is the mean of the sample means over all Receivers (1, ...N). GMD is the mean of the sample means over all Receivers (1, ...N).
6.3.1. Definition and Metric Units 7.3.1. Definition and Metric Units
Using the parameters above, we obtain the value of Type-P-One-way- Using the parameters above, we obtain the value of Type-P-One-way-
Delay singleton for all packets sent during the test interval at each Delay singleton for all packets sent during the test interval at each
Receiver (Destination), as per [RFC2679]. For each packet that Receiver (Destination), as per [RFC2679]. For each packet that
arrives within Tmax of its sending time, TstampSrc, the one-way delay arrives within Tmax of its sending time, TstampSrc, the one-way delay
singleton (dT) will be a finite value in units of seconds. singleton (dT) will be a finite value in units of seconds.
Otherwise, the value of the singleton is Undefined. Otherwise, the value of the singleton is Undefined.
For each packet [i] that has a finite One-way Delay at Receiver n (in For each packet [i] that has a finite One-way Delay at Receiver n (in
other words, excluding packets which have undefined one-way delay): other words, excluding packets which have undefined one-way delay):
Type-P-Finite-One-way-Delay-Receiver-n-[i] = Type-P-Finite-One-way-Delay-Receiver-n-[i] =
= TstampRecv[i] - TstampSrc[i] = TstampRecv[i] - TstampSrc[i]
The units of Finite one-way delay are seconds, with sufficient The units of Finite one-way delay are seconds, with sufficient
resolution to convey 3 significant digits. resolution to convey 3 significant digits.
6.3.2. Sample Mean Statistic 7.3.2. Sample Mean Statistic
This section defines the Sample Mean at each of N Receivers. This section defines the Sample Mean at each of N Receivers.
Type-P-Finite-One-way-Delay-Mean-Receiver-n = RnDM = Type-P-Finite-One-way-Delay-Mean-Receiver-n = RnDM =
J[n] J[n]
--- ---
1 \ 1 \
--- * > Type-P-Finite-One-way-Delay-Receiver-n-[i] --- * > Type-P-Finite-One-way-Delay-Receiver-n-[i]
J[n] / J[n] /
--- ---
i = 1 i = 1
Figure 9: Type-P-Finite-One-way-Delay-Mean-Receiver-n Figure 11: Type-P-Finite-One-way-Delay-Mean-Receiver-n
where all packets i= 1 through J[n] have finite singleton delays. where all packets i= 1 through J[n] have finite singleton delays.
6.3.3. One-to-Group Mean Delay Statistic 7.3.3. One-to-Group Mean Delay Statistic
This section defines the Mean One-way Delay calculated over the This section defines the Mean One-way Delay calculated over the
entire Group (or Matrix). entire Group (or Matrix).
Type-P-One-to-Group-Mean-Delay = GMD = Type-P-One-to-Group-Mean-Delay = GMD =
N N
--- ---
1 \ 1 \
- * > RnDM - * > RnDM
N / N /
--- ---
n = 1 n = 1
Figure 10: Type-P-One-to-Group-Mean-Delay Figure 12: 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.
6.3.4. One-to-Group Range of Mean Delays 7.3.4. One-to-Group Range of Mean Delays
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, (R1DM, R2DM,...RnDM). receivers in the Group, (R1DM, R2DM,...RnDM).
Type-P-One-to-Group-Range-Mean-Delay = GRMD = max(RnDM) - min(RnDM) Type-P-One-to-Group-Range-Mean-Delay = GRMD = max(RnDM) - min(RnDM)
6.3.5. One-to-Group Maximum of Mean Delays 7.3.5. One-to-Group Maximum of Mean Delays
This section defines a metrics for the maximum of mean delays over This section defines a metrics for the maximum of mean delays over
all N receivers in the Group, (R1DM, R2DM,...RnDM). all N receivers in the Group, (R1DM, R2DM,...RnDM).
Type-P-One-to-Group-Max-Mean-Delay = GMMD = max(RnDM) Type-P-One-to-Group-Max-Mean-Delay = GMMD = max(RnDM)
6.4. One-to-Group one-way Loss Statistics 7.4. One-to-Group one-way Loss Statistics
This section defines the overall 1-way loss statistics for an entire This section defines the overall 1-way loss statistics for an entire
Group. For example, we can define the group loss ratio, as Group. For example, we can define the group loss ratio, as
illustrated below. This is a metric designed to summarize the entire illustrated below. This is a metric designed to summarize the entire
Matrix. Matrix.
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 > GLR 3 R3L1 R3L2 R3L3 ... R3Lk R3LR > GLR
. | . |
. | . |
. | . |
n RnL1 RnL2 RnL3 ... RnLk RnLR / n RnL1 RnL2 RnL3 ... RnLk RnLR /
Figure 11: One-to-Group Loss Ratio Figure 13: One-to-Group Loss Ratio
where: where:
R1L1 is the Type-P-One-way-Loss singleton (L) evaluated at Receiver 1 R1L1 is the Type-P-One-way-Loss singleton (L) evaluated at Receiver 1
for packet 1. for packet 1.
R1LR is the Type-P-One-way-Loss-Ratio evaluated at Receiver 1 for the R1LR is the Type-P-One-way-Loss-Ratio evaluated at Receiver 1 for the
sample of packets (1,...K). sample of packets (1,...K).
GLR is the loss ratio over all Receivers (1, ..., N). GLR is the loss ratio over all Receivers (1, ..., N).
6.4.1. One-to-Group Loss Ratio 7.4.1. One-to-Group Loss Ratio
The overall Group loss ratio id defined as The overall Group loss ratio id defined as
Type-P-One-to-Group-Loss-Ratio = Type-P-One-to-Group-Loss-Ratio =
K,N K,N
--- ---
1 \ 1 \
= --- * > L(k,n) = --- * > L(k,n)
K*N / K*N /
--- ---
k,n = 1 k,n = 1
Figure 12 Figure 14
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.
6.4.2. One-to-Group Loss Ratio Range 7.4.2. One-to-Group Loss Ratio Range
Given a Matrix of loss singletons as illustrated above, determine the Given a Matrix of loss singletons as illustrated above, determine the
Type-P-One-way-Packet-Loss-Average for the sample at each receiver, Type-P-One-way-Packet-Loss-Average for the sample at each receiver,
according to the definitions and method of [RFC2680]. The Type-P- according to the definitions and method of [RFC2680]. The Type-P-
One-way-Packet-Loss-Average, RnLR for receiver n, and the Type-P-One- One-way-Packet-Loss-Average, RnLR for receiver n, and the Type-P-One-
way-Loss-Ratio illustrated above are equivalent metrics. In terms of way-Loss-Ratio illustrated above are equivalent metrics. In terms of
the parameters used here, these metrics definitions can be expressed the parameters used here, these metrics definitions can be expressed
as as
Type-P-One-way-Loss-Ratio-Receiver-n = RnLR = Type-P-One-way-Loss-Ratio-Receiver-n = RnLR =
K K
--- ---
1 \ 1 \
- * > RnLk - * > RnLk
K / K /
--- ---
k = 1 k = 1
Figure 13: Type-P-One-way-Loss-Ratio-Receiver-n Figure 15: Type-P-One-way-Loss-Ratio-Receiver-n
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-Loss-Ratio-Range = max(RnLR) - min(RnLR) Type-P-One-to-Group-Loss-Ratio-Range = 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 max and
minimum loss ratios for the Group, rather than only reporting the minimum loss ratios for the Group, rather than only reporting the
difference between them. difference between them.
6.4.3. Comparative Loss Ratio 7.4.3. Comparative 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. receiver for the sample and test interval of interest.
The Comparative Loss Ratio is defined as The Comparative Loss Ratio is defined as
Type-P-Comp-Loss-Ratio-Receiver-n = RnCLR = Type-P-Comp-Loss-Ratio-Receiver-n = RnCLR =
K K
skipping to change at page 33, line 24 skipping to change at page 39, line 24
k=1 k=1
= ----------------------------- = -----------------------------
/ K \ / K \
| --- | | --- |
| \ | | \ |
K - Min | > Ln(k) | K - Min | > Ln(k) |
| / | | / |
| --- | | --- |
\ k=1 / N \ k=1 / N
Figure 14: Type-P-Comp-Loss-Ratio-Receiver-n Figure 16: Type-P-Comp-Loss-Ratio-Receiver-n
6.5. One-to-Group one-way Delay Variation Statistics 7.5. One-to-Group one-way Delay Variation Statistics
There is are two delay variation (DV) statistics to summarize the There are two delay variation (DV) statistics that summarize the
performance over the Group: the maximum DV over all receivers and the performance over the Group: the maximum DV over all receivers and the
range of DV over all receivers. minimum DV over all receivers (where DV is a point-to-point metric).
For each receiver, the DV is usually expressed as the 1-10^(-3)
The detailed definitions are T0 BE PROVIDED. quantile of one-way delay minus the minimum one-way delay.
7. Measurement Methods: Scaleability and Reporting 8. Measurement Methods: Scaleability 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 measurement points where a multiparty configurations require multiple measurement points where a
stream of singletons will be collected. The amount of information stream of singletons will be collected. The amount of information
requiring storage grows with both the number of metrics and the requiring storage grows with both the number of metrics and the
number of measurement points, so the scale of the measurement number of measurement points, so the scale of the measurement
architecture multiplies the number of singleton results that must be architecture multiplies the number of singleton results that must be
skipping to change at page 34, line 18 skipping to change at page 40, line 18
architectures today, where even the individual singletons may not be architectures today, where even the individual singletons may not be
stored at each measurement point. stored at each measurement point.
In recognition of the likely need to minimize form of the results for In recognition of the likely need to minimize form of the results for
storage and communication, the Group metrics above have been 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
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).
7.1. Computation methods 8.1. 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 one is a
centralized statistic calculation method and the latter one is a centralized statistic calculation method and the latter one 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
skipping to change at page 35, line 11 skipping to change at page 41, line 11
the reference point first to obtain the general information of the the reference point first to obtain the general information of the
group performance. If the detail results are required, the reference group performance. If the detail 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. It is out of the scope of this memo. results. It is out of the scope of this memo.
7.2. Measurement 8.2. Measurement
To prevent any biais in the result, the configuration of a one-to- To prevent any bias in the result, the configuration of a one-to-many
many measure must take in consideration that implicitly more packets measure must take in consideration that implicitly more packets will
will to be routed than send and selects a test packets rate that will to be routed than send and selects a test packets rate that will not
not impact the network performance. impact the network performance.
7.3. effect of Time and Space Aggregation Order on Group Stats 8.3. 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 the computation. It makes scalability of the reporting and of the computation. It makes the
the hypothesis that receivers are managed remotly and not co-located. hypothesis that receivers are managed remotely and not co-located.
2 methods are available to compute group statistics:
Figure 8and (Figure 11) illustrate the method method choosen: the
one-to-one statistic is computed per interval of time before the
computation of the mean over the group of receivers [method1];
Figure 15 presents the second one, metric is computed over space
and then over time [method2].
They differ only by the order of the time and of the space
aggregation. View as a matrix this order is neutral as it does not
impact the result, but the impact on a measurement deployement is
critical.
Recv multimetrics samples represented a matrix as illustrated below
Point of
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
\------------- ------------/ \------------- ------------/
\/ \/
Group Stat over space and time Stat over space and time
Figure 15: Impact of space aggregation on Group Stat Figure 17: Impact of space aggregation on multimetrics Stat
2 methods are available to compute statistics on the resulting
matrix:
o metric is computed over time and then over space;
o metric is computed over space and then over time.
They differ only by the order of the time and of the space
aggregation. View as a matrix this order is neutral as does not
impact the result, but the impact on a measurement deployment is
critical.
In both cases the volume of data to report is proportional to the In both cases the volume of data to report is proportional to the
number of probes. But there is a major difference between these 2 number of probes. But there is a major difference between these 2
methods: methods:
method2: In space and time aggregation mode the volume of data to method2: In space and time aggregation mode the volume of data to
collect is proportionnal to the number of test packets received; collect is proportional to the number of test packets received;
Each received packet RiSi triggers out a block of data that must Each received packet RiSi triggers out a block of data that must
be reported to a common place for computing the stat over space; be reported to a common place for computing the stat over space;
method1: In time and space aggregation mode the volume of data to method1: In time and space aggregation mode the volume of data to
collect is proportionnal to the period of aggregation, so it does collect is proportional to the period of aggregation, so it does
not depend on the number of packet received; not depend on the number of packet received;
Method 2 property has severe drawbacks in terms of security and Method 2 property has severe drawbacks in terms of security and
dimensionning: dimensioning:
The increasing of the rate of the test packets may result in a The increasing of the rate of the test packets may result in a
sort of DoS toward the computation points; sort of DoS toward the computation points;
The dimensioning of a measurement system is quite impossible to The dimensioning of a measurement system is quite impossible to
validate. validate.
The time agregation interval provides the reporting side with a The time aggregation interval provides the reporting side with a
control of various collecting aspects such as bandwidth and control of various collecting aspects such as bandwidth and
computation and storage capacities. So this draft defines metrics computation and storage capacities. So this draft defines metrics
based on method 1. based on method 1.
Note: In some specific cases one may need sample of singletons over Note: In some specific cases one may need sample of singletons over
space. To adress this need it is suggested firstly to limit the space. To address this need it is suggested firstly to limit the
number of test and the number of test packets per seconds. Then number of test and the number of test packets per seconds. Then
reducing the size of the sample over time to one packet give sample reducing the size of the sample over time to one packet give sample
of singleton over space.. of singleton over space..
7.4. effect of Time and Space Aggregation Order on Spatial Stats 8.3.1. Impact on group stats
TBD 2 methods are available to compute group statistics:
8. Open issues o method1: Figure 10 andFigure 13 illustrate the method chosen: the
one-to-one statistic is computed per interval of time before the
computation of the mean over the group of receivers;
o method2: Figure 17 presents the second one, metric is computed
over space and then over time.
9. Security Considerations 8.3.2. Impact on spatial stats
Active measurement: (TODO: security considerations of owd pl, jitter 2 methods are available to compute group statistics:
rfcs applies (editor notes: add references).
9.1. passive measurement o method 1: spatial segment metrics and statistics are preferably
computed over time by each points of interest;
The generation of packets which match systematically the hash o method 2: Vectors metrics are intrinsecally instantaneous space
function may lead to a DoS attack toward the collector. metrics which must be reported using method2 whenever
instantaneous metrics information is needed. Pure passive
measurement approach has no choice but to use this method because
delay and losses may not be computed in each point of interest.
The generation of packets with spoofing addresses may corrupt the 9. Manageability Considerations
results without any possibility to detect the spoofing.
9.2. one-to-group metric Usually IPPM WG documents defines each metric reporting within its
definition. This document defines the reporting of all the metrics
introduced in a single section to provide consistent information
while avoiding repetitions. the aim is to contribute to the work of
the WG on the reporting and to satisfy IESG recommendation of
gathering manageability considerations in a dedicated section.
Data models of spatial and one-to-group metrics are similar excepted
that points of interests of spatial vectors must be ordered.
The complexity of the reporting relies on the number of points of
interests.
9.1. Reporting spatial metric
The reporting of spatial metrics shares a lot of aspects with
RFC2679-80. New ones are common to all the definitions and are
mostly related to the reporting of the path and of methodology
parameters that may bias raw results analysis. This section presents
these specific parameters and then lists exhaustively the parameters
that shall be reported.
9.1.1. Path
End-to-end metrics can't determine the path of the measure despite
IPPM RFCs recommend it to be reported (Section 3.8.4 of [RFC2679]).
Spatial metrics vectors provide this path. The report of a spatial
vector must include the points of interests involved: the sub set of
the hosts of the path participating to the instantaneous measure.
9.1.2. Host order
A spatial vector must order the points of interest according to their
order in the path. It is highly suggested to use the TTL in IPv4,
the Hop Limit in IPv6 or the corresponding information in MPLS.
The report of a spatial vector must include the ordered list of the
hosts involved in the instantaneous measure.
9.1.3. Timestamping bias
The location of the point of interest inside a node influences the
timestamping skew and accuracy. As an example, consider that some
internal machinery delays the timestamping up to 3 milliseconds then
the minimal uncertainty reported be 3 ms if the internal delay is
unknown at the time of the timestamping.
The report of a spatial vector must include the uncertainty of the
timestamping compared to wire time.
9.1.4. Reporting spatial One-way Delay
The reporting includes information to report for one-way-delay as
perthe Section 3.6 of [RFC2679].the same apply for packet loss and
ipdv
9.2. Reporting One-to-group metric
9.3. Metric identification
IANA assigns each metric defined by the IPPM WG with a unique
identifier as per [RFC4148] in the IANA-IPPM-METRICS-REGISTRY-MIB.
To avoid misunderstanding and to address specific reporting
constraints, section Section 5.4.3 of this memo gives distinct names
to passive metrics and Section 13 requests a distinct metric
identifier for each metrics the memo defines.
As it is crucial for composition of metrics to know the methodology
used (e.g. generation method, detection method...), the report of a
metric result used in composition of metrics MUST alway include its
metric identifier.
9.4. Reporting data model
This section presents the elements of the datamodel and the usage of
the information reported for real network performance analysis. It
is out of the scope of this section to define how the information is
reported.
The data model is build with pieces of information introduced and
explained in one-way delay definitions [RFC2679], in packet loss
definitions [RFC2680] and in IPDV definitions[RFC3393][RFC3432]. It
includes not only information given by "Reporting the metric"
sections but by sections "Methodology" and "Errors and Uncertainties"
sections.
Following are the elements of the datamodel taken from end-to-end
definitions referred in this memo and from spatial and multicast
metrics it defines:
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 Dst_host, the IP address of the receiver;
o Hosts_serie: <H1, H2,..., Hn>, a list of points of interest;
o Loss_threshold: The threshold of infinite delay;
o Systematic_error: constant delay between wire time and
timestamping;
o Calibration_error: maximal uncertainty;
o Src_time, the sending time for a measured packet;
o Dst_time, the receiving time for a measured packet;
o Result_status : an indicator of usability of a result 'Resource
exhaustion' 'infinite', 'lost';
o Delays_serie: <dT1,..., dTn> a list of delays;
o Losses_serie: <B1, B2, ..., Bi, ..., Bn>, a list of Boolean values
(spatial) or a set of Boolean values (one-to-group);
o Result_status_serie: 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.
Following is the information of each vector that should be available
to compute samples:
o Packet_type;
o Packet_length;
o Src_host, the sender of the packet;
o Dst_host, the receiver of the packet, apply only for spatial
vectors;
o Hosts_serie: not ordered for one-to-group;
o Src_time, the sending time for the measured packet;
o dT, the end-to-end one-way delay for the measured packet, apply
only for spatial vectors;
o Delays_serie: apply only for delays and ipdv vector, not ordered
for one-to-group;
o Losses_serie: apply only for packets loss vector, not ordered for
one-to-group;
o Result_status_serie;
o Observation_duration: the difference between the time of the last
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;
* Systematic error: constant delay between wire time and
timestamping;
* Calibration error: maximal uncertainty;
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.
Following is the information that should be available for each sample
to compute statistics:
o Packet_type;
o Packet_length;
o Src_host, the sender of the packet;
o Dst_host, the receiver of the 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 Result_status_serie;
o Observation_duration: the difference between the time of the last
singleton of the last sample and the time of the first singleton
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
reported:
o Result;
o Start_time;
o Duration;
o Result_status;
o Singleton_number, the number of singletons the statistic is
computed on;
10. Open issues
Do we define min, max, avg of for each segment metrics ?
having the maximum loss metric value could be interesting. Say,
the segment between router A and B always contributes loss metric
value of "1" means it could be the potential problem segment.
Uploading dTi of each Hi consume a lot of bandwidth. Computing
statistics (min, max and avg) of dTi locally in each Hi reduce the
bandwidth consumption.
11. Security Considerations
Spatial and one-to-group metrics are defined on the top of end-to-end
metrics. Security considerations discussed in One-way delay metrics
definitions of [RFC2679] , in packet loss metrics definitions
of[RFC2680] and in IPDV metrics definitions of[RFC3393] and [RFC3432]
apply to multimetrics.
11.1. Spatial metrics
Malicious generation of packets with spoofing addresses may corrupt
the results without any possibility to detect the spoofing.
Malicious generation of packets which match systematically the hash
function used to detect the packets may lead to a DoS attack toward
the point of reference.
11.2. one-to-group metric
The reporting of measurement results from a huge number of probes may
overload the network the reference point is attach to, the reference
point network interfaces and the reference point computation
capacities.
The configuration of a measure must take in consideration that The configuration of a measure must take in consideration that
implicitly more packets will to be routed than send and selects a implicitly more packets will to be routed than send and selects a
test packets rate accordingly. test packets rate accordingly. Collecting statistics from a huge
number of probes may overload any combination of the network where
Collecting statistics from a huge number of probes may overload any the measurement controller is attach to, measurement controller
combination of the network the measurement controller is attach to, network interfaces and measurement controller computation capacities.
measurement controller network interfaces and measurement controller
computation capacities.
one-to-group metrics: one-to-group metrics measurement should consider using source
authentication protocols, standardized in the MSEC group, to avoid
fraud packet in the sampling interval. The test packet rate could be
negotiated before any measurement session to avoid deny of service
attacks.
10. Acknowledgments 12. Acknowledgments
Lei would like to acknowledge Zhili Sun from CCSR, University of Lei would like to acknowledge Prof. Zhili Sun from CCSR, University
Surrey, for his instruction and helpful comments on this work. of Surrey, for his instruction and helpful comments on this work.
11. IANA Considerations 13. IANA Considerations
Metrics defined in this memo Metrics defined in this memo are Metrics defined in this memo Metrics defined in this memo are
designed to be registered in the IANA IPPM METRICS REGISTRY as designed to be registered in the IANA IPPM METRICS REGISTRY as
described in initial version of the registry [RFC4148] : described in initial version of the registry [RFC4148] :
IANA is asked to register the following metrics in the IANA-IPPM- IANA is asked to register the following metrics in the IANA-IPPM-
METRICS-REGISTRY-MIB : METRICS-REGISTRY-MIB :
Spatial-One-way-Delay-Vector OBJECT-IDENTITY Spatial-One-way-Delay-Vector OBJECT-IDENTITY
skipping to change at page 38, line 31 skipping to change at page 49, line 37
REFERENCE REFERENCE
"Reference "RFCyyyy, section 4.1." "Reference "RFCyyyy, section 4.1."
-- RFC Ed.: replace yyyy with actual RFC number & remove this -- RFC Ed.: replace yyyy with actual RFC number & remove this
note note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics nn } -- IANA assigns nn
subpath-One-way-Delay-Stream OBJECT-IDENTITY Spatial-Packet-Loss-Vector OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-subpath-One-way-Delay-Stream" "Type-P-Spatial-Packet-Loss-Vector"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 4.2." "Reference "RFCyyyy, section 4.2."
-- RFC Ed.: replace yyyy with actual RFC number & remove this -- RFC Ed.: replace yyyy with actual RFC number & remove this
note note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics nn } -- IANA assigns nn
Spatial-One-way-Packet-Loss-Vector OBJECT-IDENTITY Spatial-One-way-ipdv-Vector OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-Spatial-One-way-Packet-Loss-Vector" "Type-P-Spatial-One-way-ipdv-Vector"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 4.3." "Reference "RFCyyyy, section 4.3."
-- RFC Ed.: replace yyyy with actual RFC number & remove this -- RFC Ed.: replace yyyy with actual RFC number & remove this
note note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics nn } -- IANA assigns nn
Spatial-One-way-Jitter-Vector OBJECT-IDENTITY Spatial-Segment-One-way-Delay-Stream OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-Spatial-One-way-Jitter-Vector" "Type-P-Spatial-Segment-One-way-Delay-Stream"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 4.4." "Reference "RFCyyyy, section 5.1."
-- RFC Ed.: replace yyyy with actual RFC number & remove this -- RFC Ed.: replace yyyy with actual RFC number & remove this
note note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics nn } -- IANA assigns nn
Spatial-Segment-Packet-Loss-Stream OBJECT-IDENTITY
STATUS current
DESCRIPTION
"Type-P-Spatial-Segment-Packet-Loss-Stream"
REFERENCE
"Reference "RFCyyyy, section 5.2."
-- RFC Ed.: replace yyyy with actual RFC number & remove this
note
:= { ianaIppmMetrics nn } -- IANA assigns nn
Spatial-Segment-One-way-ipdv-Stream OBJECT-IDENTITY
STATUS current
DESCRIPTION
"Type-P-Spatial-Segment-ipdv-Stream"
REFERENCE
"Reference "RFCyyyy, section 5.3."
-- RFC Ed.: replace yyyy with actual RFC number & remove this
note
:= { ianaIppmMetrics nn } -- IANA assigns nn
Passive-Segment-One-way-Delay-Stream OBJECT-IDENTITY
STATUS current
DESCRIPTION
"Type-P-Passive-Segment-One-way-Delay-Stream"
REFERENCE
"Reference "RFCyyyy, section 5.4.1."
-- RFC Ed.: replace yyyy with actual RFC number & remove this
note
:= { ianaIppmMetrics nn } -- IANA assigns nn
Passive-Segment-Packet-Loss-Stream OBJECT-IDENTITY
STATUS current
DESCRIPTION
"Type-P-Passive-Segment-Packet-Loss-Stream"
REFERENCE
"Reference "RFCyyyy, section 5.4.2."
-- RFC Ed.: replace yyyy with actual RFC number & remove this
note
:= { ianaIppmMetrics nn } -- IANA assigns nn
Passive-Segment-One-way-ipdv-Stream OBJECT-IDENTITY
STATUS current
DESCRIPTION
"Type-P-Passive-Segment-One-way-ipdv-Stream"
REFERENCE
"Reference "RFCyyyy, section 5.4.3."
-- RFC Ed.: replace yyyy with actual RFC number & remove this
note
:= { ianaIppmMetrics nn } -- IANA assigns nn
-- One-to-group metrics
one-to-group-One-way-Delay-Vector OBJECT-IDENTITY one-to-group-One-way-Delay-Vector OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-one-to-group-One-way-Delay-Vector" "Type-P-one-to-group-One-way-Delay-Vector"
REFERENCE REFERENCE
skipping to change at page 40, line 21 skipping to change at page 53, line 23
REFERENCE REFERENCE
"Reference "RFCyyyy, section 5.2." "Reference "RFCyyyy, section 5.2."
-- RFC Ed.: replace yyyy with actual RFC number & remove this -- RFC Ed.: replace yyyy with actual RFC number & remove this
note note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics nn } -- IANA assigns nn
one-to-group-One-way-Jitter-Vector OBJECT-IDENTITY one-to-group-One-way-ipdv-Vector OBJECT-IDENTITY
STATUS current STATUS current
DESCRIPTION DESCRIPTION
"Type-P-one-to-group-One-way-Jitter-Vector" "Type-P-one-to-group-One-way-ipdv-Vector"
REFERENCE REFERENCE
"Reference "RFCyyyy, section 5.3." "Reference "RFCyyyy, section 5.3."
-- RFC Ed.: replace yyyy with actual RFC number & remove this -- RFC Ed.: replace yyyy with actual RFC number & remove this
note note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics nn } -- IANA assigns nn
skipping to change at page 42, line 30 skipping to change at page 55, line 34
"Reference "RFCyyyy, section 6.4.2." "Reference "RFCyyyy, section 6.4.2."
-- RFC Ed.: replace yyyy with actual RFC number & remove this -- RFC Ed.: replace yyyy with actual RFC number & remove this
note note
:= { ianaIppmMetrics nn } -- IANA assigns nn := { ianaIppmMetrics nn } -- IANA assigns nn
-- --
12. References 14. References
12.1. Normative References 14.1. Normative References
[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.
[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.
[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.
12.2. Informative References 14.2. Informative References
[RFC2678] Mahdavi, J. and V. Paxson, "IPPM Metrics for Measuring [RFC2678] Mahdavi, J. and V. Paxson, "IPPM Metrics for Measuring
Connectivity", RFC 2678, September 1999. Connectivity", RFC 2678, September 1999.
[RFC2681] Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip [RFC2681] Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
Delay Metric for IPPM", RFC 2681, September 1999. Delay Metric for IPPM", RFC 2681, September 1999.
[RFC3148] Mathis, M. and M. Allman, "A Framework for Defining [RFC3148] Mathis, M. and M. Allman, "A Framework for Defining
Empirical Bulk Transfer Capacity Metrics", RFC 3148, Empirical Bulk Transfer Capacity Metrics", RFC 3148,
July 2001. July 2001.
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