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Versions: (draft-stephan-ippm-multimetrics) 00 01 02 03 04 05 06 07 08 09 10 11 12 RFC 5644

Network Working Group                                         E. Stephan
Internet-Draft                                            France Telecom
Intended status: Informational                                  L. Liang
Expires: April 25, 2007                             University of Surrey
                                                               A. Morton
                                                               AT&T Labs
                                                        October 22, 2006


        IP Performance Metrics (IPPM) for spatial and multicast
                    draft-ietf-ippm-multimetrics-02

Status of this Memo

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Copyright Notice

   Copyright (C) The Internet Society (2006).

Abstract

   The IETF IP Performance Metrics (IPPM) working group has standardized
   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
   defines spatial metrics for measuring the performance of segments
   along a path and metrics for measuring the performance of a group of



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   users in multiparty communications.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  5
     2.1.  Multiparty metric  . . . . . . . . . . . . . . . . . . . .  5
     2.2.  Spatial metric . . . . . . . . . . . . . . . . . . . . . .  5
     2.3.  Spatial metric points of interest  . . . . . . . . . . . .  5
     2.4.  One-to-group metric  . . . . . . . . . . . . . . . . . . .  5
     2.5.  One-to-group metric points of interest . . . . . . . . . .  5
     2.6.  Reference point  . . . . . . . . . . . . . . . . . . . . .  5
     2.7.  Vector . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     2.8.  Matrix . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Motivations for spatial and one-to-group metrics . . . . . . .  7
     3.1.  spatial metrics  . . . . . . . . . . . . . . . . . . . . .  7
     3.2.  One-to-group metrics . . . . . . . . . . . . . . . . . . .  8
     3.3.  Discussion on Group-to-one and Group-to-group metrics  . .  9
   4.  Spatial metrics definitions  . . . . . . . . . . . . . . . . .  9
     4.1.  A Definition for Spatial One-way Delay Vector  . . . . . . 10
     4.2.  A Definition of a sample of One-way Delay of a sub path  . 12
     4.3.  A Definition for Spatial One-way Packet Loss Vector  . . . 15
     4.4.  A Definition for Spatial One-way Jitter Vector . . . . . . 16
     4.5.  Pure Passive Metrics . . . . . . . . . . . . . . . . . . . 18
     4.6.  Discussion on spatial statistics . . . . . . . . . . . . . 20
   5.  One-to-group metrics definitions . . . . . . . . . . . . . . . 20
     5.1.  A Definition for one-to-group One-way Delay  . . . . . . . 20
     5.2.  A Definition for one-to-group One-way Packet Loss  . . . . 21
     5.3.  A Definition for one-to-group One-way Jitter . . . . . . . 21
     5.4.  Discussion on one-to-group statistics  . . . . . . . . . . 23
   6.  Extension from one-to-one to one-to-many measurement . . . . . 26
   7.  Open issues  . . . . . . . . . . . . . . . . . . . . . . . . . 27
   8.  Security Considerations  . . . . . . . . . . . . . . . . . . . 27
   9.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 27
   10. IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 27
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 28
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 28
     11.2. Informative References . . . . . . . . . . . . . . . . . . 28
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 29
   Intellectual Property and Copyright Statements . . . . . . . . . . 30










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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
   measurements:

   o  A general framework for defining performance metrics, described in
      the Framework for IP Performance Metrics, RFC 2330 [RFC2330];

   o  A One-way Active Measurement Protocol Requirements, RFC 3763
      [RFC3763];

   o  A One-way Active Measurement Protocol (OWAMP) [work in progress];

   o  An IP Performance Metrics Registry , RFC 4148 [RFC4148];

   It specified a set of end-to-end metrics, which conform to this
   framework:

   o  The IPPM Metrics for Measuring Connectivity, RFC 2678 [RFC2678];

   o  The One-way Delay Metric for IPPM, RFC 2679 [RFC2679];

   o  The One-way Packet Loss Metric for IPPM, RFC 2680 [RFC2680];

   o  The Round-trip Delay Metric for IPPM, RFC 2681 [RFC2681];

   o  A Framework for Defining Empirical Bulk Transfer Capacity Metrics
      RFC 3148 [RFC3148];

   o  One-way Loss Pattern Sample Metrics, RFC 3357 [RFC3357];

   o  IP Packet Delay Variation Metric for IPPM, RFC 3393 [RFC3393];

   o  Network performance measurement for periodic streams, RFC 3432
      [RFC3432];




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   o  Packet Reordering Metric for IPPM [Work in progress];

   Based on these works, this memo defines 2 kinds of multi party
   metrics.

   Firstly it defines spatial metrics:

   o  A 'sample', called Type-P-Spatial-One-way-Delay-Vector, will be
      introduced to divide an end-to-end Type-P-One-way-Delay in a
      spatial sequence of one-way delays.

   o  A 'sample', called Type-P-Spatial-One-way-Packet-Loss-Vector, will
      be introduced to divide an end-to-end Type-P-One-way-Packet-Loss
      in a spatial sequence of packet loss.

   o  Using the Type-P-Spatial-One-way-Delay-Vector metric, a 'sample',
      called Type-P-Spatial-One-way-Jitter-Vector, will be introduced to
      divide an end-to-end Type-P-One-way-ipdv in a spatial sequence of
      jitter.

   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
      define the one-way-delay between a pair of host of the path.  This
      metric is similar to Type-P-One-way-Delay-Stream.

   o  Using Type-P-subpath-One-way-Delay-Stream, a 'sample' Type-P-
      Passive-One-way-Delay-Stream will be introduced to define passive
      metrics.  These metrics are designed for pure passive measurement
      methodology as introduced by PSAMP WG.

   Then it defines one-to-group metrics.

   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-
      Vector, will be introduced to define the list of Type-P-one-way-
      delay between this sender and the group of receivers.

   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-
      Loss-Vector, will be introduced to define the list of Type-P-One-
      way-Packet-Loss between this sender and the group of receivers

   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-
      Vector, will be introduced to define the list of Type-P-One-way-
      ipdv between this sender and the group of receivers





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   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
      view of a group of users as well as the requirements of relative
      QoS on multiparty communications.


2.  Terminology

2.1.  Multiparty metric

   A metric is said to be multiparty if the definition involved more
   than two sources or destinations in the measurements.  All multiparty
   metrics define a set of hosts called "points of interest", where one
   host is the source and other hosts are the measurement collection
   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
   destinations, then measurements may be conducted between < ha, hb>, <
   ha, hc>, ..., <ha, hn >.

2.2.  Spatial metric

   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

   Points of interest of a spatial metric are the routers or sibling in
   the path between source and destination (in addition to the source
   and the destination themself).

2.4.  One-to-group metric

   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,
   the topology of the communication group can be viewed as a centre-
   distributed or server-client topology with the source as the centre/
   server in the topology.

2.5.  One-to-group metric points of interest

   Points of interest of One-to-group metrics are the set of host
   destinations receiving packets from the source (in addition to the
   source itself).

2.6.  Reference point

   The centre/server in the one-to-group measurement that is controlled
   by network operators can be a very good reference point where



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   measurement data can be collected for further processing although the
   actual measurements have to be carried out at all points of interest.
   I.e., the measurement points will be all clients/receivers while the
   reference point acts as source for the one-to-group metric.  Thus, we
   can define the reference point as the host while the statistic
   calculation will be carried out.

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
   observation of the behaviour of the same packet at different places
   of a network at different time.  For instance, if One-way delay
   singletons abserved 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
   elements can be orgnized as {dT1, dT2,..., dTN}.  The elements in one
   vector are singletons distinct with each other in terms of both
   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
   time T1.  Additional to a singleton, Vector gives information over a
   space dimension.

2.8.  Matrix

   Several vectors can orgnize form up a Matrix, which contains results
   observed in a sampling interval at different place of a network at
   different time.  For instance, given One-way delay vectors V1={dT11,
   dT12,..., dT1N}, V2={dT21, dT22,..., dT2N},..., Vm={dTm1, dTm2,...,
   dTmN} for Packet P1, P2,...,Pm, we can have a One-way delay Matrix
   {V1, V2,...,Vm}.  Additional to the information given by a Vector, a
   Matrix is more powerful to present network performance in both space
   and time dimensions.  It normally corresponding to a sample.

















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   The relation among Singleton, Vector and Matrix can be shown in the
   following Fig 1.

           one to group     Singleton
                           /            Sample
   Src             Rcvr ..............................
     ..................R1dT1   R1dT2     R1dT3    R1dT4
      `:=-.._
     T   `._ ``-..__
            `.      `- R2dT1   R2dT2     R2dT3    R2dT4
              `-.
                 `-.
                    `._R3dT1   R3dT2     R3dT3    R3dT4

                      Vector           Matrix
                     (space)           (time)


   Figure 1.


3.  Motivations for spatial and one-to-group metrics

   All IPPM metrics are defined for end-to-end measurement.  These
   metrics provide very good guides for measurement in the pair
   communications.  However, further efforts should be put to define
   metrics for multiparty measurements such as one to one trajectory
   metrics and one to multipoint metrics.

3.1.  spatial metrics

   Decomposition of instantaneous end-to-end measures is needed:

   o  The PCE WG is extending existing protocols to permit remote path
      computation and path computation quality, including inter domain.
      One may say that in intra domain the decomposing the performance
      of a path is not whished.  However such decomposition is desirable
      in interdomain to qualify each AS computation with the initial
      request.  So it is necessary to define standard spatial metrics
      before going further in the computation of inter domain path with
      QoS constraint.

   o  Traffic engineering and troubleshooting applications require
      spatial views of the one-way delay consumption, identification of
      the location of the lost of packets and the decomposition of the
      jitter over the path.





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   o  Monitoring the QoS of a multicast tree, of MPLS point-to-
      multipoint and inter-domain communication require spatial
      decomposition of the one-way delay, of the packet loss and of the
      jitter.

   o  Composition of metrics is a need to scale in the measurement
      plane.  The definition of composition metrics is a work in
      progress [I-D.ietf-ippm-spatial-composition]; .  Spatial measure
      give typically the individual performance of an intra domain
      segment.  It is the elementary piece of information to exchange
      for measuring interdomain performance based on composition of
      metrics.

   o  The PSAMP WG defines capabilities to sample packets in a way to to
      support measurement.  [I-D.boschi-ipfix-reducing-redundancy];
      defines a method to collect packets information to measure the
      instantaneous spatial performance without injecting test traffic.
      Consequently it is urgent to define a set of common spatial
      metrics for passive and active techniques which respect the IPPM
      framework [RFC2330].  This need is emphases by the fact that end-
      to-end spatial measurement involves the 2 techniques;

3.2.  One-to-group metrics

   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
   the performance of a multiparty communication in the view of a group
   with consideration that it involves a group of people rather than
   two.  As a consequence a simple one-way metric cannot describe the
   multi-connection situation.  We need some new metrics to collect
   performance of all the connections for further statistics analysis.
   A group of metrics are proposed in this stage named one-to-group
   performance metrics based on the unicast metrics defined in IPPM WG.
   One-to-group metrics are trying to composite one-way metrics from one
   source to a group of destinations to make up new metrics.  The
   compositions are necessary for judging the network performance of
   multiparty communications and can also be used to describe the
   difference of the QoS served among a group of users.

   One-to-group performance metrics are needed for several reasons:

   o  For designing and engineering multicast trees and MPLS point-to-
      multipoint LSP;

   o  For evaluating and controlling of the quality of the multicast
      services;





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   o  For controlling the performance of the inter domain multicast
      services;

   o  For presenting and evaluating the relative QoS requirements for
      the multiparty communications.

   To understand the connection situation between one source and any one
   receiver in the multiparty communication group, we need the
   collection of instantaneous end-to-end measures.  It will give us
   very detailed insight into each branch of the multicast tree in terms
   of end-to-end absolute QoS.  It can provide clear and helpful
   information for engineers to identify the connection with problems in
   a complex multiparty routing tree.

3.3.  Discussion on Group-to-one and Group-to-group metrics

   We note that points of interest can also be selected to define
   measurements on Group-to-one and Group-to-group topologies.  These
   topologies are currently beyond the scope of this memo, because they
   would involve multiple packets launched from different sources.
   However, we can give some clues here on these two cases.

   The measurements for group-to-one topology can be easily derived from
   the one-to-group measurement.  The measurement point is the reference
   point that is acting as a receiver while all of clients/receivers
   defined for one-to-group measurement act as sources in this case.

   For the group-to-group connection topology, we can hardly define the
   reference point and, therefore, have difficulty to define the
   measurement points.  However, we can always avoid this confusion by
   treating the connections as one-to-group or group-to-one in our
   measurements without consideration on how the real communication will
   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
   hosts < Ha, Hb, Hc, ..., Hm >, we can always decompose them into n
   one-to-group communications as < ha, Ha, Hb, Hc, ..., Hm >, < hb, Ha,
   Hb, Hc, ..., Hm >, <hc, Ha, Hb, Hc, ..., Hm >, ..., < hn, Ha, Hb, Hc,
   ..., Hm >.


4.  Spatial metrics definitions

   Spatial decomposition metrics are based on standard end-to-end
   metrics.

   The definition of a spatial metric is coupled with the corresponding
   end-to-end metric.  The methodoly is based on the measure of the same
   test packet and parameters of the corresponding end-to-end metric.



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4.1.  A Definition for Spatial One-way Delay Vector

   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
   section, it will be tagged with a trailing asterisk.

   Sections 3.5 to 3.8 of [RFC2679] give requirements and applicability
   statements for end-to-end one-way-delay measurements.  They are
   applicable to each point of interest Hi involved in the measure.
   Spatial one-way-delay 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
   spatial measurement.

4.1.1.  Metric Name

   Type-P-Spatial-One-way-Delay-Vector

4.1.2.  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.

             + T*, a time, the sending (or initial observation) time for
             a measured packet.

             + dT* a delay,  the one-way delay for a measured packet.

             + dT1,..., dTn a list of delay.

             + P*, the specification of the packet type.

             + <Src, H1, H2,..., Hn, Dst>, a path digest.


4.1.3.  Metric Units

   A sequence of times.






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4.1.4.  Definition

   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
   sequence of values <T+dT1,T+dT2,...,T+dTn,T+dT> such that dT is the
   Type-P-One-way-Delay from Src to Dst and such that for each Hi of the
   path, T+dTi is either a real number corresponding to the wire-time
   the packet passes (last bit received) Hi, or undefined if the packet
   never passes Hi.

   Type-P-Spatial-One-way-Delay-Vector metric is defined for the path
   <Src, H1, H2,..., Hn, Dst> as the sequence of values
   <T,dT1,dT2,...,dTn,dT>.

4.1.5.  Discussion

   Following are specific issues which may occur:

   o  the delay looks to decrease: dTi > DTi+1. this seem typically du
      to some clock synchronisation issue. this point is discussed in
      the section 3.7.1.  "Errors or uncertainties related to Clocks" of
      of [RFC2679];

   o  The location of the point of interest in the device influences the
      result (see [I-D.quittek-ipfix-middlebox]).  If the packet is not
      observed on the input interface the delay includes buffering time
      and consequently an uncertainty due to the difference between
      'wire time' and 'host time';

4.1.6.  Interference with other test packet

   To avoid packet collision it is preferable to include a sequence
   number in the packet.

4.1.7.  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.

4.1.8.  Methodologies

   Section 3.6 of [RFC2679] gives methodologies for end-to-end one-way-
   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
   proceed as follows:




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   o  At each Hi, prepare to capture the packet sent a time T, take a
      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
   the packet.

4.1.9.  Reporting the metric

   Section 3.6 of [RFC2679] indicates the items to report.

4.1.10.  Path

   It is clear that a end-to-end Type-P-One-way-Delay can't determine
   the list of hosts the packet passes throught.  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-
   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

   This metric is similar to the metric Type-P-One-way-Delay-Poisson-
   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
   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
   hosts of a path usable by active and passive measurements.

   Sections 3.5 to 3.8 of [RFC2679] give requirements and applicability
   statements for end-to-end one-way-delay measurements.  They are
   applicable to each point of interest Hi involved in the measure.
   Subpath one-way-delay measurement SHOULD be respectful of them,
   especially those related to methodology, clock, uncertainties and
   reporting.



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4.2.1.  Metric Name

   Type-P-subpath-One-way-Delay-Stream

4.2.2.  Metric Parameters

             + Src*, the IP address of the sender.

             + Dst*, the IP address of the receiver.

             + i, An integer which orders exchange points in the path.

             + k, An integer which orders the packets sent.

         + <Src, H1, H2,..., Hn, Dst>, a path digest.

             + 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 order in the path must greater that Ha;

             + Hi, exchange points of the path digest.

             + dT1,..., dTn a list of delay.

             + P*, the specification of the packet type.



4.2.3.  Metric Units

   A sequence of pairs <Tk,dt>.

   T is one of time of the sequence T1...Tn;

   dt is a delay.

4.2.4.  Definition

   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,
   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
   value of the sample Type-P-subpath-One-way-Delay-Stream as the
   sequence made up of the couples <Tk,dTk.b - dTk.a>. dTk.a is the
   delay between Src and Ha. dTk.b is the delay between Src and Hb.
   'dTk.b - dTk.a' is the one-way delay experienced by the packet sent
   at the time Tk by Src when going from Ha to Hb.



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4.2.5.  Discussion

   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 b is Dst <Tk,dTk.b - dTk.a> is the measure of the last hop.

   o  the delay looks to decrease: dTi > DTi+1:

      *  This is typically du to clock synchronisation issue. this point
         is discussed in the section 3.7.1.  "Errors or uncertainties
         related to Clocks" of of [RFC2679];

      *  This may occurs too when the clock resolution of one probe is
         bigger than the minimun delay of a path.  As an example this
         happen when measuring the delay of a path which is 500 km long
         with one probe synchronized using NTP having a clock resolution
         of 8ms.

   o  The location of the point of interest in the device influences the
      result (see [I-D.quittek-ipfix-middlebox]).  If the packet is not
      observed on the input interface the delay includes buffering time
      and consequently an uncertainty due to the difference between
      'wire time' and 'host time';

   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
      pure passive measure.  In this case Tk may be forced to Tk+dTk.a.
      This motivate separate metrics names for pure passive measurement
      or specific reporting information.

   o  Pure passive measure should consider packets of the same size and
      of the same Type-P.

4.2.6.  Interference with other packet

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.





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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, uncertainities and
   reporting.

   Following we define the spatial metric, then we adapt some of the
   points above and introduce points specific to spatial measurement.

4.3.1.  Metric Name

   Type-P-Spatial-One-way-Packet-Loss-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.

           + 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.

           + <Src, H1, H2,..., Hn, Dst>, a path digest.

           + B1, B2, ..., Bi, ..., Bn, a list of boolean values.





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4.3.3.  Metric Units

   A sequence of boolean values.

4.3.4.  Definition

   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.

4.3.5.  Discussion

   Following are specific issues wich 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;

   o

   The location of the meter in the device influences the result:

   o  Even if the packet is received by a device, it may be not observed
      by a meter located after a buffer;

4.3.6.  Reporting

   Section in progress.

4.4.  A Definition for Spatial One-way Jitter 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.

   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.
   Spatial one-way-ipdv measurement SHOULD be respectful of them,
   especially those related to methodology, clock, uncertainities and
   reporting.

   Following we adapt some of them and introduce points specific to



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   spatial measurement.

4.4.1.  Metric Name

   Type-P-Spatial-One-way-Jitter-Vector

4.4.2.  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.

             + <Src, H1, H2,..., Hn, Dst>, a 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.


4.4.3.  Metric Units

   A sequence of times.





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4.4.4.  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-Jitter-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*.

4.4.5.  Sections in progress

   See sections 3.5 to 3.7 of [RFC3393].

4.5.  Pure Passive Metrics

   Spatial metrics may be measured without injecting test traffic as
   described in [I-D.boschi-ipfix-reducing-redundancy] .

4.5.1.  Discussion on Passive measurement

   One might says that most of the operational issues occur in the last
   mile and that consequently such measure are less useful than active
   measuremeent.  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.

4.5.1.1.  Passive One way delay

   As the packet is not a test packet, it does not include the time it
   was sent.

   Consequently a point of interest Hi ignores the time the packet was



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   send.  So It is not possible to measure the delay between Src and Hi
   in the same manner it is not possible to measure the delay betwwen Hi
   and Dst.

4.5.1.2.  Passive Packet loss

   The packet is not a test packet, so it does not include a sequence
   number.

   Packet lost measurement doe not require time synchronization and
   require only one point of observation.  Nevertheless it requires the
   point of interest Hi to be expecting the packet.  Practically Hi may
   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
   the packet does not carry the time it was injected in the network.
   So a probe Hi can not compute dTi.

   An alternative to these issues consist in considering sample spatial
   One-way delay that T is the time when H1 (the first passive probe of
   the path) observed the packet.

4.5.2.  Reporting and composition

   To avoid misunderstanding and to address specific reporting
   constraint a proposal consists in defining distinct metrics for pure
   passive measurement based on the definition above.

   It is crucial to know the methodologie used because of the difference
   of method of detection (expecting Seq++); because of the difference
   of source of time (H1 vs Src) and because of the difference of
   behavior of the source (Poisson/unknown).

4.5.3.  naming and registry

   Having distinct metrics identifiers for spatial metrics and passive
   spatial metrics in the [RFC4148] will avoid interoperabily issues
   especially during composition of metrics.

4.5.4.  Passive One way delay metrics

4.5.5.  Passive One way PacketLoss metrics

4.5.6.  Passive One way jitter metrics







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4.6.  Discussion on spatial statistics

   Do we define min, max, avg of spatial 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.


5.  One-to-group metrics definitions

5.1.  A Definition for one-to-group One-way Delay

5.1.1.  Metric Name

   Type-P-one-to-group-One-way-Delay-Vector

5.1.2.  Metric Parameters

   o  Src, the IP address of a host acting as the source.

   o  Recv1,..., RecvN, the IP addresses of the N hosts acting as
      receivers.

   o  T, a time.

   o  dT1,...,dTn a list of time.

   o  P, the specification of the packet type.

   o  Gr, the multicast group address (optional).  The parameter Gr is
      the multicast group address if the measured packets are
      transmitted by multicast.  This parameter is to identify the
      measured traffic from other unicast and multicast traffic.  It is
      set to be optional in the metric to avoid losing any generality,
      i.e. to make the metric also applicable to unicast measurement
      where there is only one receivers.

5.1.3.  Metric Units

   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].





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5.1.4.  Definition

   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 {
   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
   and each receiver with value of { dT1, dT2,...,dTn }.

5.2.  A Definition for one-to-group One-way Packet Loss

5.2.1.  Metric Name

   Type-P-one-to-group-One-way-Packet-Loss-Vector

5.2.2.  Metric Parameters

   o  Src, the IP address of a host acting as the source.

   o  Recv1,..., RecvN, the IP addresses of the N hosts acting as
      receivers.

   o  T, a time.

   o  T1,...,Tn a list of time.

   o  P, the specification of the packet type.

   o  Gr, the multicast group address (optional).

5.2.3.  Metric Units

   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].

5.2.4.  Definition

   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
   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
   receivers {<T1,0|1>,<T2,0|1>,..., <Tn,0|1>}.

5.3.  A Definition for one-to-group One-way Jitter

5.3.1.  Metric Name

   Type-P-one-to-group-One-way-Jitter-Vector




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5.3.2.  Metric Parameters

           + Src, the IP address of a host acting as the source.

           + Recv1,..., RecvN, the IP addresses of the N hosts acting as
           receivers.

           + T1, a time.

           + T2, a time.

           + ddT1,...,ddTn, a list of time.

           + P, the specification of the packet type.

           + F, a selection function defining unambiguously the two
           packets from the stream selected for the metric.

    + Gr, the multicast group address (optional)

5.3.3.  Metric Units

   The value of a Type-P-one-to-group-One-way-Jitter-Vector is a set of
   singletons metrics Type-P-One-way-ipdv [RFC3393].

5.3.4.  Definition

   Given a Type P packet stream, Type-P-one-to-group-One-way-Jitter-
   Vector is defined for two packets from the source Src to the N hosts
   {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-
   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 {
   Recv1,...,RecvN } at time T2.  T1 is the wire-time at which Scr sent
   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
   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-
   group-One-way-Jitter-Vector from Src to { Recv1,...,RecvN } at T1, T2
   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)
   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
   {dT'1+T2,...,dT'n+T2} (last bit of the second packet), and that
   {dT'1-dT1,...,dT'n-dTn} ={ddT1,...,ddTn}.





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5.4.  Discussion on one-to-group statistics

   The defined one-to-group metrics above can all be directly achieved
   from the relevant unicast one-way metrics.  They managed to collect
   all unicast measurement results of one-way metrics together in one
   profile and sort them by receivers and packets in a multicast group.
   They can provide sufficient information regarding the network
   performance in terms of each receiver and guide engineers to identify
   potential problem happened on each branch of a multicast routing
   tree.  However, these metrics can not be directly used to
   conveniently present the performance in terms of a group and neither
   to identify the relative performance situation.

   One may say that no matter how many people join the communication,
   the connections can still be treated as a set of one-to-one
   connection.  However, we might not describe a multiparty
   communication by a set of one-way measurement metrics because of the
   difficulty for understanding and the lack of convenience.  For
   instance, an engineer might not describe the connections of a
   multiparty online conference in terms of one-to-group one-way delay
   for user A and B, B and C, and C and A because people might be
   confused.  If there are more users in the same communication, the
   description might be very long.  And he might use the one-way metrics
   with worst and the best value to give users an idea of the
   performance range of the service they are providing.  But it is not
   clear enough and might not be accurate in a large multiparty
   communication scenario.

   From the performance point of view, the multiparty communication
   services not only require the absolute performance support but also
   the relative performance.  The relative performance means the
   difference between absolute performance of all users.  Directly using
   the one-way metrics cannot present the relative performance
   situation.  However, if we use the variations of all users one-way
   parameters, we can have new metrics to measure the difference of the
   absolute performance and hence provide the threshold value of
   relative performance that a multiparty service might demand.  A very
   good example of the high relative performance requirement is the
   online gaming.  A very light worse delay will result in failure in
   the game.  We have to use the new statistic metrics to define exactly
   how small the relative delay the online gaming requires.  There are
   many other services, e.g. online biding, online stock market, etc.,
   need a rule to judge the relative performance requirement.
   Therefore, we can see the importance of new statistic metrics to feed
   this need.

   We might use some one-to-group statistic conceptions to present and
   report the group performance and relative performance to save the



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   report transmission bandwidth.  Statistics have been defined for One-
   way metrics in corresponding FRCs.  They provide the foundation of
   definition for performance statistics.  For instance, there are
   definitions for minimum and maximum One-way delay in [RFC2679] and
   One-way delay mean in [I-D.ietf-ippm-spatial-composition].  However,
   there is a dramatic difference between the statistics for one-to-one
   communications and for one-to-many communications.  The former one
   only has statistics over the time dimension while the later one can
   have statistics over both time dimension and space dimention.  This
   space dimension is introduced by the Matrix concept.  For a Matrix M
   shown in the Fig. 2, each row is a set of One-way singletons
   spreading over the space dimension and each colume is another set of
   One-way singletons spreading over the time dimension.

   (preamble)
   /                    \
   | dT11, dT12,..., dT1N |
   | dT21, dT22,..., dT2N |
   |                 :      |
   |                 :      |
   | dTm1, dTm2,..., dTmN |
   \                    /

   Fig. 2 Matrix M (m*N)

   In Matrix M, each element is a One-way delay singleton.  Each row is
   a delay vector contains the One-way delays of the same packet
   observed at N points of interest.  It implies the geographical factor
   of the performance within a group.  Each colume is a set of One-way
   delays observed during a sampling interval at one of the points of
   interest.  It presents the delay performance at a receiver over the
   time dimension.

   Therefore, one can either calculate statistics by rows over the space
   dimension or by columes over the time dimension.  It's up to the
   operators or service provides which dimension they are interested in.
   For example, a TV broadcast service provider might want to know the
   statistical performance of each user in a long term run to make sure
   their services are acceptable and stable.  While for an online gaming
   service provider, he might be more interested to know if all users
   are served farely by calculating the statistics over the space
   dimension.  This memo does not intent to recommend which of the
   statistics are better than the other.

   To save the report transmission bandwidth, each point of interest can
   send statistics in a pre-defined time interval to the reference point
   rather than sending every One-way singleton it observed.  As long as
   an appropriate time interval is decided, appropriate stantistics can



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   represent the performance in a certain accurate scale.  How to decide
   the time interval and how to bootstrap all points of interest and the
   reference point depend on applications.  For instance, applications
   with lower transmission rate can have the time interval longer and
   ones with higher transmission rate can have the time interval
   shorter.  However, this is out of the scope of this memo.

   Moreover, after knowing the statistics over the time dimension, one
   might want to know how this statistics distributed over the space
   dimension.  For instance, a TV broadcast service provider had the
   performance Matrix M and calculated the One-way delay mean over the
   time dimension to obtain a delay Vector as {V1,V2,..., VN}.  He then
   calculated the mean of all the elements in the Vector to see what
   level of delay he has served to all N users.  This new delay mean
   gives information on how good the service has been delivered to a
   group of users during a sampling interval in terms of delay.  It
   needs twice calculation to have this statistic over both time and
   space dimensions.  We name this kind of statistics 2-level statistics
   to distinct with those 1-level statistics calculated over either
   space or time dimension.  It can be easily prove that no matter over
   which dimension a 2-level statistic is calculated first, the results
   are the same.  I.e. one can calculate the 2-level delay mean using
   the Matrix M by having the 1-level delay mean over the time dimension
   first and then calculate the mean of the obtained vector to find out
   the 2-level delay mean.  Or, he can do the 1-level statistic
   calculation over the space dimention first and then have the 2-level
   delay mean.  Both two results will be exactly the same.  Therefore,
   when define a 2-level statistic, it is no need to specify in which
   procedure the calculation should follow.

   There are many statistics can be defined for the proposed one-to-
   group metrics over either the space dimension or the time dimension
   or both.  In this memo, we define one-to-group mean and one-to-group
   variation over the space dimension.  These statistics are offered
   mostly to be illustrative of what could be done.

   One-to-group mean are trying to measure the overall performance for a
   multicast group associated to one source.  It is a reflection of the
   absolute performance of a multiparty communication service when we
   treat all receivers as one customer.  It can also present the trend
   of the absolute performance of all receivers, i.e., it shows that
   most of the receivers in the multiparty communication service trend
   to receive an absolute performance close to the mean.

   One-to-group variation streams are trying to measure how the
   performance varies among all of the users in a multicast group
   associated to one source.  The word "variation" in this memo is the
   population standard deviation.  It reflects the relative



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   performancesituation in a multiparty communication service, i.e., the
   level of the difference between the absolute performanceof each
   receivers.

   Using the one-to-group mean and one-to-group variation concepts, we
   can have a much clear understand on the performanceof a multiparty
   communication service in terms of its trend and range.  There can be
   mean and variation stream definitions for each of the three one-to-
   group metrics defined above.  We only present the definition of Type-
   P-one-to-group-One-way-Delay-Space-Mean and Type-P-one-to-group- One-
   way-Delay-Space-Variation as examples in this memo.

5.4.1.  Type-P-one-to-group-One-way-Delay-Space-Mean

   Given a Type-P-one-to-group-One-way-Delay-Vector, the mean { dT1,
   dT2,...,dTN } for the packet from Src at time T to { Recv1,...,RecvN
   }.

   For example, suppose we take a delay vector and the results is:

      Delay_Vector = {dT1,...,dTN}

   Then the mean over space dimension would be:

      Delay_Space_Mean = DsM = sum{dT1,...,dTN}/N

5.4.2.  Type-P-one-to-group-One-way-Delay-Variation-Stream

   Given a Type-P-one-to-group-One-way-Delay-Vector, the variation {
   dT1, dT2,...,dTN } for the packet from Src at time T to {
   Recv1,...,RecvN }.

   We still take the above Delay_Vector as an sample and the variation
   would be:

      Delay_Variation_Stream = {SUM[(dT1-DsM)^2,...,(dTN-
      DsM)^2)}/N)^(1/2)


6.  Extension from one-to-one to one-to-many measurement

   The above one-to-group metrics were defined to compose measurement
   results of a group of users who receive the same data from one
   source.  Moreover, this is one of efforts to introducing the one-to-
   many concern to the IPPM working group with respect to the fact that
   all existing documents in the group are unicast oriented, which talk
   about only one-to-one single "path" in measurements.  This concept
   can be extended from the "path" to "path tree" to cover both one-to-



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   one and one-to-many communications.  Actually, the one-to-one
   communications can be viewed as a special case of one-to-many from
   the routing point of view.  The one-to-many communications build up a
   routing tree in the networks and one-to-one can be viewed as a
   special simplified tree without branches but only the "trunk".

   Therefore, the one-to-group metrics described in this memo can even
   be viewed as general metrics to measure the delay, jitter and packet
   loss in IP networks.  When it applies to one-to-one communications,
   the metrics will have N receivers while N equal to 1.  And the
   statistic metrics for one-to-one communications are exactly the one-
   to-group metrics themselves when calculated using the methods given.


7.  Open issues


8.  Security Considerations

   Active measumrement: see security section in owd pl, jitter rfcs
   (editor notes: add references).

   passive measurement:

      The generation of packets which match systematically the hash
      function may lead to a DoS attack toward the collector.

      The generation of packets with spoofing adresses may corrupt the
      results without any possibility to detect the spoofing.

   one-to-group metrics require collection of singletons which may
   overload the network the measurement controller is attach to.


9.  Acknowledgments

   Lei would like to acknowledge Zhili Sun from CCSR, University of
   Surrey, for his instruction and helpful comments on this work.


10.  IANA Considerations

   Metrics defined in this memo will be registered in the IANA IPPM
   METRICS REGISTRY as described in initial version of the registry
   [RFC4148].


11.  References



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11.1.  Normative References

   [RFC2330]  Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
              "Framework for IP Performance Metrics", RFC 2330,
              May 1998.

   [RFC2679]  Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
              Delay Metric for IPPM", RFC 2679, September 1999.

   [RFC2680]  Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
              Packet Loss Metric for IPPM", RFC 2680, September 1999.

   [RFC3393]  Demichelis, C. and P. Chimento, "IP Packet Delay Variation
              Metric for IP Performance Metrics (IPPM)", RFC 3393,
              November 2002.

   [RFC4148]  Stephan, E., "IP Performance Metrics (IPPM) Metrics
              Registry", BCP 108, RFC 4148, August 2005.

11.2.  Informative References

   [I-D.boschi-ipfix-reducing-redundancy]
              Boschi, E., "Reducing redundancy in IPFIX and PSAMP
              reports", draft-boschi-ipfix-reducing-redundancy-02 (work
              in progress), June 2006.

   [I-D.ietf-ippm-spatial-composition]
              Morton, A. and E. Stephan, "Spatial Composition of
              Metrics", draft-ietf-ippm-spatial-composition-01 (work in
              progress), June 2006.

   [I-D.quittek-ipfix-middlebox]
              Quittek, J., "Guidelines for IPFIX Implementations on
              Middleboxes", draft-quittek-ipfix-middlebox-00 (work in
              progress), February 2004.

   [RFC2678]  Mahdavi, J. and V. Paxson, "IPPM Metrics for Measuring
              Connectivity", RFC 2678, September 1999.

   [RFC2681]  Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
              Delay Metric for IPPM", RFC 2681, September 1999.

   [RFC3148]  Mathis, M. and M. Allman, "A Framework for Defining
              Empirical Bulk Transfer Capacity Metrics", RFC 3148,
              July 2001.

   [RFC3357]  Koodli, R. and R. Ravikanth, "One-way Loss Pattern Sample
              Metrics", RFC 3357, August 2002.



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   [RFC3432]  Raisanen, V., Grotefeld, G., and A. Morton, "Network
              performance measurement with periodic streams", RFC 3432,
              November 2002.

   [RFC3763]  Shalunov, S. and B. Teitelbaum, "One-way Active
              Measurement Protocol (OWAMP) Requirements", RFC 3763,
              April 2004.


Authors' Addresses

   Stephan Emile
   France Telecom Division R&D
   2 avenue Pierre Marzin
   Lannion,   F-22307

   Fax:   +33 2 96 05 18 52
   Email: emile.stephan@orange-ft.com


   Lei Liang
   CCSR, University of Surrey
   Guildford
   Surrey,   GU2 7XH

   Fax:   +44 1483 683641
   Email: L.Liang@surrey.ac.uk


   Al Morton
   200 Laurel Ave. South
   Middletown, NJ  07748
   USA

   Phone: +1 732 420 1571
   Email: acmorton@att.com















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