Network Working Group E. Stephan Internet-Draft France Telecom Intended status: Informational L. Liang Expires:~~September 2, 2007~~January 7, 2008University of Surrey A. Morton AT&T Labs~~March 1,~~July 6,2007 IP Performance Metrics (IPPM) for spatial and multicast~~draft-ietf-ippm-multimetrics-03~~draft-ietf-ippm-multimetrics-04Status of this Memo By submitting this Internet-Draft, each author represents that any applicable patent or other IPR claims of which he or she is aware have been or will be disclosed, and any of which he or she becomes aware will be disclosed, in accordance with Section 6 of BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on~~September 2, 2007.~~January 7, 2008.Copyright Notice Copyright (C) The IETF Trust (2007). 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 users in multiparty communications. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . .~~6~~52.1.~~Multiparty metric~~Path Digest Hosts. . . . . . . . . . . . . . . . . . . . 6 2.2.~~Spatial~~Multipartymetric . . . . . . . . . . . . . . . . . . . .~~. .~~6 2.3. Spatial metric~~points of interest~~. . . . . . . . . .. . . . . . . . . . . . 6 2.4. One-to-group metric . . . . . . . . . . . . . . . . . . . 6 2.5.~~One-to-group metric points~~Pointsof interest . . . . . . . . . .. . . . . . . . . .6 2.6. Reference point . . . . . . . . . . . . . . . . . . . . .~~6~~82.7. Vector . . . . . . . . . . . . . . . . . . . . . . . . . .~~7~~82.8. Matrix . . . . . . . . . . . . . . . . . . . . . . . . . .~~7~~83. Motivations~~for spatial and one-to-group metrics~~. . . . . . .~~8 3.1. spatial metrics~~. . . . . . . . . . . . . . . . . .9 3.1. Motivations for spatial metrics . .. . .~~8 3.2. One-to-group metrics~~. . . . . . . .9 3.2. Motivations for One-to-group metrics. . . . . . . . . . .~~9~~103.3. Discussion on Group-to-one and Group-to-group metrics . .~~10~~114. Spatialvectorsmetrics definitions . . . . . . . . . . . . .~~. . . . 10~~114.1. A Definition for Spatial One-way Delay Vector . . . . . .~~10~~124.2. A Definition~~of a sample of One-way Delay of a sub path . 13 4.3. A Definition~~for Spatial One-way Packet Loss Vector . . .~~16 4.4.~~13 4.3.A Definition for Spatial One-way~~Jitter~~IpdvVector . . . . . .~~17 4.5. Pure Passive Metrics . . . . . . . . . . . .~~.15 4.4. Spatial Methodology. . . . . .~~19 4.6. Discussion on spatial statistics~~. . . . . . . . . . . . .~~21~~175.~~One-to-group~~Spatial Segmentsmetrics definitions . . . . . . . . . . . . .~~. . 21~~195.1. A Definition~~for one-to-group~~of a sample ofOne-way Delayof a segment of the path. . . . . . .~~21 5.2. A Definition for one-to-group One-way Packet Loss . . .~~.~~22 5.3. A Definition for one-to-group One-way Jitter~~. . . . . . .~~22 6. One-to-Group Sample Statistics~~. . . . . . . .19 5.2. A Definition of a sample of Packet Loss of a segment of the path. . . . . . . .~~24 6.1. Discussion on the Impact of packet loss on statistics~~. .~~26 6.2. General Metric Parameters~~. . . . . . . . . . . . .21 5.3. A Definition of a sample of One-way Ipdv of a segment of the path. . .~~27 6.3. One-to-Group one-way Delay Statistics~~. . . . . . . . . .~~28 6.4. One-to-Group one-way Loss Statistics~~. . . . . . . . . .24 5.4. Discussion on Passive Segment Metrics.~~31 6.5. One-to-Group one-way Delay Variation Statistics~~. . . . .~~33 7. Measurement Methods: Scaleability and Reporting~~. . . .24 6. One-to-group metrics definitions. . .~~33 7.1. Computation methods~~. . . . . . . . . . . .27 6.1. A Definition for one-to-group One-way Delay. . . . . . .~~34 7.2. Measurement~~27 6.2. A Definition for one-to-group One-way Packet Loss . . . . 28 6.3. A Definition for one-to-group One-way Ipdv .. . . . . . .28 7. One-to-Group Sample Statistics. . . . . . . . . . . . . . . .~~35 7.3. effect~~30 7.1. Discussion on the Impactof~~Time and Space Aggregation Order~~packet losson~~Group Stats~~statistics . . 32 7.2. General Metric Parameters. . . . . . . . . . . . . . . .33 7.3. One-to-Group one-way Delay Statistics. . . . . . . . . .~~35~~347.4.~~effect~~One-to-Group one-way Loss Statistics . . . . . . . . . . . 37 7.5. One-to-Group one-way Delay Variation Statistics . . . . . 39 8. Measurement Methods: Scaleability and Reporting . . . . . . . 39 8.1. Computation methods . . . . . . . . . . . . . . . . . . . 40 8.2. Measurement . . . . . . . . . . . . . . . . . . . . . . . 41 8.3. Effectof Time and Space Aggregation Order on~~Spatial~~Stats . . .41 9. Manageability Considerations .. . . . . . . . . . . . . . . .43 9.1. Reporting spatial metric. . . . . . .~~37 8.~~. . . . . . . . . . 43 9.2. Reporting One-to-group metric . . . . . . . . . . . . . . 44 9.3. Metric identification . . . . . . . . . . . . . . . . . . 44 9.4. Reporting data model . . . . . . . . . . . . . . . . . . . 44 10.Open issues . . . . . . . . . . . . . . . . . . . . . . . . .~~37 9.~~48 11.Security Considerations . . . . . . . . . . . . . . . . . . .~~37 9.1. passive measurement~~48 11.1. Spatial metrics. . . . . . . . . . . . . . . . . . .~~37 9.2.~~. . 48 11.2.one-to-group metric . . . . . . . . . . . . . . . . . . .~~37 10.~~48 12.Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .~~37 11.~~49 13.IANA Considerations . . . . . . . . . . . . . . . . . . . . .~~38 12.~~49 14.References . . . . . . . . . . . . . . . . . . . . . . . . . .~~42 12.1.~~55 14.1.Normative References . . . . . . . . . . . . . . . . . . .~~42 12.2.~~55 14.2.Informative References . . . . . . . . . . . . . . . . . .~~43~~56Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .~~43~~56Intellectual Property and Copyright Statements . . . . . . . . . .~~45~~581. 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 [RFC2330]; o A One-way Active Measurement Protocol Requirements [RFC3763]; o A One-way Active Measurement Protocol (OWAMP) [RFC4656]; o An IP Performance Metrics Registry [RFC4148]; It specified a set of end-to-end metrics, which conform to this framework: o The IPPM Metrics for Measuring Connectivity [RFC2678]; o The One-way Delay Metric for IPPM [RFC2679]; o The One-way Packet Loss Metric for IPPM [RFC2680]; o The Round-trip Delay Metric for IPPM [RFC2681]; o A Framework for Defining Empirical Bulk Transfer Capacity Metrics [RFC3148]; o One-way Loss Pattern Sample Metrics [RFC3357]; o IP Packet Delay Variation Metric for IPPM [RFC3393]; o Network performance measurement for periodic streams [RFC3432]; o Packet Reordering Metric for IPPM~~[RFC4737][Work in progress]; Based on these works, this~~[RFC4737]; Thismemo defines~~2 kinds of multi party metrics.~~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: o A~~'sample',~~'vector',called Type-P-Spatial-One-way-Delay-Vector, will be introduced to divide an end-to-end Type-P-One-way-Delay[RFC2679]in a spatial sequence of one-way delays. o A~~'sample',~~'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[RFC2680]in a spatial sequence of packet loss. o Using the Type-P-Spatial-One-way-Delay-Vector metric, a~~'sample',~~'vector',called~~Type-P-Spatial-One-way-Jitter-Vector,~~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~~jitter.~~ipdv.o Using the Type-P-Spatial-One-way-Delay-Vector metric, a 'sample', called~~Type-P-subpath-One-way-Delay-Stream,~~Type-P-Segment-One-way-Delay-Stream,will be introduced to define~~the one-way-delay~~a set of one-way delaysbetween a pair of host of the~~path. This metric is similar to Type-P-One-way-Delay-Stream.~~path;o Using~~Type-P-subpath-One-way-Delay-Stream,~~the Type-P-Spatial-Packet-Loss-Vector metric,a~~'sample' Type-P- Passive-One-way-Delay-Stream~~'sample', called Type-P-Segment-Packet-Loss-Stream,will be introduced to define~~passive metrics. These metrics are designed for pure passive measurement methodology as~~a set of packet losses between a pair of host of the path; o Using the Type-P-Spatial-ipdv-Vector metric, a 'sample', called Type-P-Segment-ipdv-Stream, will beintroduced~~by PSAMP WG.~~to define a set of ipdvs between a pair of host of the path;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[RFC2679]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[RFC2680]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-~~Type-P-one-to-group-One-way-ipdv-Vector, will be introduced to define the list of Type-P-One-way- ipdv between this sender and the group of receivers o Then a discussion section presents the set of statistics that may be computed~~on the top of~~usingthese metrics to present the~~QoS~~network performancein~~a~~theview of a group of~~users as well as~~users. The statistics may bethebasis forrequirements~~of relative QoS~~(e.g. fairness)on multiparty communications.. Reporting of metrics is defined in the section "Manageability Consideration".2. Terminology 2.1.Path Digest Hosts The list of the hosts of a path from a source to a destination. 2.2.Multiparty metric A metric is said to be multiparty if the~~definition involved~~topology involvesmore than~~two sources~~one sourceor~~destinations~~destinationin 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.~~For the purposes of this memo (reflecting the scope of a single source), the only multiparty metrics are one-to-group metrics. 2.3.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~~measuredpacket.~~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 themselves). 2.4. One-to-group~~2.4. One-to-groupmetric 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 are the set of hosts* (as per RFC2330 definition, that is including nodes) of the set of hosts involved in the delivery of the packets (in addition to the source itself). Note that the set of thepoints of interestare (a possibly arbitrary) subset of all the hosts involved in the path.Points of interest of One-to-group metrics are the~~set of host destinations~~hostsreceiving 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 interest2.6. Reference point The centre/server in the~~one-to-group~~multimetricsmeasurement that is controlled by network operators can be a very good reference point where 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~~server wherethe 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 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 elements can be organized 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~~organize~~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 corresponds to a sample. The relation among Singleton, Vector and Matrix can be shown in the following Figure~~1. one-to-group~~3. Point ofSingletoninterest / Samples ,----. ^ / / R1.....|/~~Sample Src Recv .............................. .................... 1~~R1dT1 R1dT2 R1dT3~~R1dT4 `:=-.._ T `._ ``-..__ `. `-... 2~~... R3dTk \ / \ | | | ; R2........| |R2dT1 R2dT2 R2dT3~~R2dT4 `-. `-. `.... N~~... R3dTk | Src | || | | | R3....| |R3dT1 R3dT2 R3dT3~~R3dT4 Vector Matrix (space) (time) Figure 1: Relation beween Singletons, vectors and matrix 3. Motivations for spatial and one-to-group metrics~~... R3dTk | | || | | : ;| | | \ / | | | \ Rn......| \ RndT1 RndT2 RndT3 ... RndTk / `-----' +-------------------------------------> time Vector Matrix (space) (time) Figure 3: Relation beween Singletons, vectors and matrix 3. MotivationsAll 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.Motivations forspatial metrics Decomposition of instantaneous end-to-end measures is needed: o Decomposing the performance of interdomain path is desirable in interdomain to qualify per AS contribution to the performance. 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~~ipdvover the path. 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.~~ipdv.o Composition of metrics is a need to scale in the measurement plane. 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 instantaneous measurement respecful of the IPPM framework [RFC2330]. Consequently it is necessary to define a set of spatial metrics for passive and active techniques. 3.2.Motivations forOne-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; 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. The one-to-group metrics described in this memo introduce one-to-many concerns to the IPPM working group to measure the performance of a group of users who receiving data from the same source. The concept extends the "path" in the one-way measurement to "path tree" to cover both one-to-one and one-to-many communications. Nevertheless, applied to one-to-one communications they provide exactly the same results as the corresponding one-to-one metrics. 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. Spatialvectorsmetrics definitions~~Spatial~~This section defines vectors for thedecompositionof end-to-end singleton metrics over a path. Spatial vectorsmetrics are based onthe decomposition ofstandard end-to-end~~metrics. The definition of a spatial metric is~~metrics defined by the IPPM WG in [RFC2679], [RFC2680], [RFC3393] and [RFC3432]. Definitions arecoupled with the corresponding end-to-end~~metric. The methodology is based on the measure of~~metrics. Methodology specificities are common to allthe~~same test packet~~vectors definedand~~parameters of the corresponding end-to-end metric.~~are consequently discussed in a common section.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~~+~~oSrc*, the IP address of the sender.~~+~~oDst*, the IP address of the receiver.~~+~~oi, An integerif the list <1,2,...,n>which ordered the hosts in the path.~~+~~oHi,~~exchange points~~A host*of the path digest.~~+~~oT*, a time, the sending (or initial observation) time for a measured packet.~~+~~odT* a delay, the one-way delay for a measured packet.~~+ dT1,..., dTn~~o <dT1,..., dTn>a list of delay.~~+~~oP*, the specification of the packet type.~~+ <Src, H1,~~o <H1,H2,...,~~Hn, Dst>, a~~Hn>, hostspath digest. 4.1.3. Metric Units A sequence of times. 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~~Thisseem typically du to some clock synchronisation issue.~~this~~Thispoint is discussed in the section 3.7.1. "Errors or uncertainties related to Clocks" of of~~[RFC2679];~~[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 result. 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~~4.2. A Definition for Spatial One-way Packet Loss Vector This sectionis~~preferable to include a sequence number in~~coupled withthe~~packet. 4.1.7. loss threshold To determine if~~definition of Type-P-One-way-Packet- Loss. Then whena~~dTi~~parameter from the section 2 of [RFC2680]is~~defined or undefined~~first used in this section,it~~is necessary to define~~will be tagged witha~~period~~trailing asterisk. Sections 2.5 to 2.8of~~time after which a packet is considered loss. 4.1.8. Methodologies Section 3.6 of [RFC2679] gives methodologies~~[RFC2680] give requirements and applicability statementsfor end-to-end~~one-way- delay~~one-way-Packet-Lossmeasurements.~~Most of them apply~~They are applicableto each~~points~~point ofinterest Hi~~and are relevant to this section. Generally, for a given Type-P,~~involvedin~~a given Hi, the methodology would proceed as follows: o At each Hi, prepare to capture~~themeasure. Spatialpacket~~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~~loss measurement SHOULD be respectful of them, especially those relatedto~~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~~methodology, clock, uncertainties and reporting. Following we definethe~~set of dTi~~spatial metric, then we adapt someof~~each Hi~~the points aboveand~~order them according~~introduce points specifictospatial measurement. 4.2.1. Metric Name Type-P-Spatial-One-way-Packet-Loss-Vector 4.2.2. Metric Parameters + Src*,the~~path to build~~IP address ofthe~~Type-P-Spatial-One-way-Delay-Vector metric <T,dT1,dT2,...,dTn,dT> over~~sender. + Dst*,the~~path <H1, H2,..., Hn>. It is out~~IP addressof the~~scope of this document to define how each Hi detects~~receiver. + i, An integer which orderedthe~~packet. 4.1.9. Reporting~~hosts inthe~~metric Section 3.6~~path. + Hi, exchange pointsof~~[RFC2679] indicates~~the~~items to report. 4.1.10. Path It is clear that~~path digest. + T*,a~~end-to-end Type-P-One-way-Delay can't determine~~time,thesending (or initial observation) time for a measured packet. + dT1,..., dTn, dT, alist of~~hosts~~delay. + P*,the~~packet passes through. Section 3.8.4~~specificationof~~[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~~type. + <SH1, H2,..., Hn>, hosts path digest. + B1, B2, ..., Bi, ..., Bn,a~~sample~~listof~~One-way Delay~~Boolean values. 4.2.3. Metric Units A sequenceofBoolean values. 4.2.4. Definition Givena~~sub path This metric is similar to~~Type-P packet sent bythe~~metric Type-P-One-way-Delay-Poisson- stream defined in [RFC2679] and~~sender Src at time Tto the~~metric Type-P-One-way-Delay- Periodic-Stream defined~~receiver Dstin~~[RFC3432]. Nevertheless its definition differs because it is based of~~the~~division~~path <H1, H2, ..., Hn>. Given the sequenceof~~end-to-end One-way delay using~~times <T+dT1,T+dT2,...,T+dTn,T+dT>thepacket passes <H1, H2 ..., Hn, Dst>, Type-P-One-way-Packet-Lost-Vectormetric~~Type-P-Spatial- One-way-Delay-Vector defined above. It aims~~is~~to define a sample~~defined as the sequenceof~~One-way-Delay between~~values <B1, B2, ..., Bn> such that for each Hi of the path,a~~pair~~valueof~~hosts~~Biof0 means that dTi isa~~path usable by active~~finite value,and~~passive measurements. Sections 3.5 to 3.8~~a valueof~~[RFC2679] give requirements and applicability statements for end-to-end one-way-delay measurements. They~~1 means that dTi is undefined. 4.2.5. Discussion Followingare~~applicable to each~~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 thepoint 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. 4.2.1. Metric Name Type-P-subpath-One-way-Delay-Stream 4.2.2. Metric Parameters + Src*,~~device influencesthe~~IP address of~~result: o Even ifthe~~sender. +~~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~~orders exchange points~~ordered the hostsin the path. +~~k, An integer which orders~~Hi, exchange points ofthe~~packets sent. + <Src, H1, H2,..., Hn, Dst>, a~~path digest. +~~Ha, a host of~~T1*,the~~path digest different from Dst and Hb;~~time the first packet was sent.+~~Hb, a host of~~T2*,the~~path digest different from Src and Ha. Hb order in~~timethe~~path must greater that Ha;~~second packet was sent.+~~Hi, exchange points~~P, the specificationof thepacket type. + P1, the first packet sent at time T1. + P2, the second packet sent at time T2. + <H1, H2,..., Hn>, hostpath digest. +~~dT1,..., dTn~~<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~~list~~packet length in bits. The packetsof~~delay. + P*,~~a Type P packet stream from whichthe~~specification~~Type-P-Spatial-One-way-Delay-Vector metric is taken MUST all beof the~~packet type. 4.2.3.~~same length. 4.3.3.Metric Units A sequence of~~pairs <Tk,dt>. T is one of time of~~times. 4.3.4. Definition Giventhe~~sequence T1...Tn; dt is a delay. 4.2.4. Definition Given 2 hosts Ha~~Type-P packet having the size Land~~Hb of~~sent by the sender Src at wire-time (first bit) T1 to the receiver Dst inthe path~~<Src, H1,~~<H1,H2,...,~~Hn, Dst>, given a flow of packets of~~Hn>. Given theType-Ppacket having the size L andsent~~from~~by the senderSrcat wire-time (first bit) T2tothe receiverDst~~at~~inthe~~times T1, T2... Tn. At each of these times, we obtain a Type-P-Spatial-One- way-Delay-Vector~~same path. Given the Type-P-Spatial-One-way-Delay-Vector<T1,dT1.1, dT1.2,...,~~dT1.n,dT1>. We define~~dT1,n,dT1> ofthe~~value~~packet P1. Given the Type-P-Spatial-One-way-Delay-Vector <T2,dT2.1, dT2.2,..., dT2,n,dT2>of the~~sample Type-P-subpath-One-way-Delay-Stream~~packet P2. Type-P-Spatial-One-way-ipdv-Vector metric is definedas the sequence~~made up~~of values <T2-T1,dT2.1-dT1.1,dT2.2-dT1.2,...,dT2.n-dT1.n,dT2-dT1> Such that for each Hiof the~~couples <Tk,dTk.b - dTk.a>. dTk.a~~path <H1, H2,..., Hn>, dT2.i-dT1.iiseither a real number ifthe~~delay between Src~~packets P1and~~Ha. dTk.b~~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-T1is the~~delay between Src~~inter-packet emission intervaland~~Hb. 'dTk.b - dTk.a'~~dT2-dT1isddT*the~~one-way delay experienced by the packet sent~~Type-P-One-way-ipdvat~~the time Tk by Src when going from Ha~~T1,T2*. 4.4. Spatial Methodology Methodology, reporting and uncertainties points specified in section 3 of [RFC2679][RFC2679] appliesto~~Hb. 4.2.5. Discussion Following are specific issues which may occur: o When a is Src <Tk,dTk.b - dTk.a> is the measure~~each pointof~~the first hop. o When b is Dst <Tk,dTk.b - dTk.a> is the measure~~interest Hi measuring a elementof~~the last hop. o the~~a spatialdelay~~looks~~vector. Methodology, reporting and uncertainties points specified in section 2 of [RFC2680][RFC2680] appliesto~~decrease: dTi > DTi+1: * This is typically du to clock synchronisation issue. this~~eachpoint~~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 minimum delay~~of~~a path. As an example this happen when~~interest Himeasuring~~the delay of a path which is 500 km long with one probe synchronized using NTP having~~a~~clock resolution~~elementof~~8ms. o The location~~a spatial packet loss vector. Sections 3.5 to 3.7of~~the~~[RFC3393] give requirements and applicability statements for end-to-end One-way ipdv measurements. They are applicable to eachpoint of interestHi involvedin the~~device influences the result. If~~measure. Spatial One-way ipdv measurement SHOULD be respectful of methodology, clock, uncertainties and reporting aspects given in this section. Passive and active measurement approaches ofthe~~packet is not observed on~~metrology are considered as orthogonal. Active measure differs mainly from passive measure bythe~~input interface~~knowledge ofthe~~delay includes buffering~~time~~and consequently an uncertainty due to~~the~~difference between 'wire time' and 'host time'; o dTk.b may be observed~~packet was send by the sourceand~~not dTk.a. o Tk is unknown if~~received bythe~~flow is made of end user packets, that is pure passive measure. In this case Tk may be forced~~destination, making the RFC2330 framework difficults to applyto~~Tk+dTk.a. This motivate separate metrics names for pure~~passive~~measurement or specific reporting information. o Pure~~measurement. On the other hand, spatial metrics rely onpassive~~measure should consider packets~~observationof the~~same size and of~~packets involved in the measure. In fact each approach complimentsthe~~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~~setting the baseof~~time after which a packet is considered loss. 4.2.8. Methodologies Both active~~spatial measurement methodology: Active points of interest provide information observed at the sourceand~~passive method should discussed. 4.2.9. Reporting~~atthe~~metric Section 3.6~~destination while Passive points of interests provide information observed at intermediary hostsof~~[RFC2679] indicates~~the~~items to report. 4.2.10. Path 4.3. A Definition~~path. Generally,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~~given Type-Pof~~[RFC2680] is first used~~length L,in~~this section, it will be tagged with~~a~~trailing asterisk. Sections 2.5 to 2.8 of [RFC2680] give requirements and applicability statements~~given Hi, the methodologyfor~~end-to-end one-way-Packet-Loss measurements. They are applicable to~~spatial vector metrics would proceed as follows: o Ateach~~point~~Hi, pointsof interest~~Hi involved in~~prepare to capturethe~~measure. Spatial~~packet~~loss measurement SHOULD be respectful of them, especially those~~sent a time T, take a timestamp Ti', determine the internal delay correction dTi' (See section 3.7.1. "Errors or uncertaintiesrelated to~~methodology, clock, uncertainties and reporting. Following we define the spatial metric, then we adapt some~~Clocks"of[RFC2679]), o Each Hi extractsthe~~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*,~~path ordering information fromthe~~IP address of~~packet (e.g. time-to-live); o Each Hi computethe~~sender. + Dst*,~~wiretime from Src to Hi: Ti = Ti' - dTi'. This arrival time is undefined (infinite) ifthe~~IP address of~~packet is not detected afterthe~~receiver. + i, An integer which ordered~~'loss threshold' duration; o Each Hi extractsthe~~hosts in~~timestamp T fromthe~~path. + Hi, exchange points of~~packet, o Each Hi computesthe~~path digest. + T*, a time,~~one-way-delay from Src to Hi: dTi = Ti - T; o The reference point gathersthe~~sending (or initial observation) time for a measured packet. + dT1,..., dTn, dT, a list~~result and time-to-liveof~~delay. + P*,~~each Hi and order them according tothe~~specification of~~path to buildthe~~packet type. + <Src, H1,~~Type-P-Spatial- One-way-Delay-Vector metric <T,dT1,dT2,...,dTn,dT> over the path <Src,H1,H2,..., Hn,~~Dst>, a path digest. + B1, B2, ..., Bi, ..., Bn, a list of Boolean values. 4.3.3. Metric Units A sequence~~Dst>. 4.4.1. Loss threshold Loss threshold is the centralityof~~Boolean values. 4.3.4. Definition Given a Type-P packet sent by~~any methodology because it determinesthe~~sender Src at time T to~~presencethe~~receiver Dst~~packetin the~~path <H1, H2, ..., Hn>. Given the sequence~~measurement processof~~times <T+dT1,T+dT2,...,T+dTn,T+dT>~~the~~packet passes <H1, H2 ..., Hn, Dst>, Type-P-One-way-Packet-Lost-Vector~~point of interest and consequently determines any ground truthmetric~~is defined as~~result. It determinesthe~~sequence of values <B1, B2, ..., Bn> such that for each Hi~~presenceofan effective delay, and biasthe~~path, a value~~measureof~~Bi~~ipdv,of~~0 means that dTi is a finite value,~~packet lossand~~a value~~of~~1 means that dTi is undefined. 4.3.5. Discussion Following are specific issues which may occur: o the result includes~~the~~sequence 1,0.~~statistics.This~~case means that the packet was seen by a host~~is consistent for end-to-endbut~~not by it successor~~impacts spatial measure: dependingon the~~path; o The location~~consistencyof the~~meter in the device influences the result: o Even if~~Loss threshold amongthepoints of interest, apacket~~is received by~~may be considered lossa~~device, it~~one host but present in another one, ormay 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~~last host (last hop)of~~Type-P-One-way- ipdv. When a parameter from section 2~~the path but considered lost by Dst. The analysisof~~[RFC3393]~~such resultsis~~first used in this section,~~not deterministic: has the path change? Does the packet arrive at destination or wasit~~will~~lost during the last mile? The same applies, of course, for one-way-delay measures: a delay measured maybe~~tagged with~~infinite at one host buta~~trailing asterisk. Sections 3.5 to 3.7~~real value in another one, or may be measured as a real value by the last hostof~~[RFC3393] give requirements and applicability statements for end-to-end one-way-ipdv measurements. They are applicable to~~the path but observed as infinite by Dst. The Loss threshold should be set up with the same value ineach~~point~~hostof~~interest Hi involved~~the path andin the~~measure. Spatial one-way-ipdv measurement SHOULD~~destination. The Loss threshold mustbe~~respectful of them, especially those related~~systematically reportedto~~methodology, clock, uncertainties and reporting. Following we adapt some of them~~permit careful introspectionand~~introduce points specific~~to~~spatial measurement. 4.4.1. Metric Name Type-P-Spatial-One-way-Jitter-Vector 4.4.2. Metric Parameters + Src*,~~avoidthe~~IP address~~introductionofany contradiction inthe~~sender. + Dst*,~~statistic computation process. 4.4.2. Host Path Digest The methodology given above addsthe~~IP address~~orderof the~~receiver. + i, An integer which ordered the hosts in the path. + Hi, exchange~~points ofinterest overthe path~~digest. + T1*, the time~~to [RFC2679] one's. A perfect Host Path Digest (hum! of cource fromthe~~first packet was sent. + T2*, the time the second packet was sent. + P, the specification~~measurement pointofview only, that is, corresponding tothe~~packet type. + P1,~~real paththe~~first~~testpacket~~sent at time T1. + P2,~~experimented) may include several times several hosts: o <Ha,..., Ha> coresponds to a loop inthe~~second packet sent at time T2. + <Src, H1, H2,..., Hn, Dst>,~~path; o <Ha,..,Hb,..., Ha,...,Hb> coresponds toa~~path digest. + <T1,dT1.1, dT1.2,..., dT1.n,dT1>,~~loop inthe~~Type-P-Spatial-One-way-Delay-Vector for packet sent at time T1; + <T2,dT2.1, dT2.2,..., dT2.n,dT2>,~~path which may occurs during rerouting phases; These cases MUST be identified before statistics computation to avoid corrupted results' production. This applies especially tothe~~Type-P-Spatial-One-way-Delay-Vector for packet sent at time T2; + L*,~~measure of segments which are build from results ofa~~packet length in bits. The packets~~measureof a~~Type P packet stream from which~~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 ofthe~~Type-P-Spatial-One-way-Delay-Vector metric is~~path, a segment. Singletons aretaken~~MUST all be~~from segmentsof~~the same length. 4.4.3. Metric Units~~vectors defined above. 5.1.A~~sequence of times. 4.4.4.~~Definition~~Given~~of a sample of One-way Delay of a segment ofthe~~Type-P packet having~~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~~size L and sent by~~IP address ofthe~~sender Src at wire-time (first bit) T1 to~~sender. + Dst*,the~~receiver Dst in~~IP address ofthe~~path <H1, H2,..., Hn>. Given~~receiver. + P*,the~~Type-P packet having~~specification ofthe~~size L and sent by the sender Src at wire-time (first bit) T2 to the receiver Dst~~packet type; + i, An integer which orders exchange pointsin the~~same~~path.~~Given~~+ k, An integer which ordersthe~~Type-P-Spatial-One-way-Delay-Vector <T1,dT1.1, dT1.2,..., dT1,n,dT1>~~packets sent. + Hi, a hostof the~~packet P1. Given~~path digest; + <H1, H2,..., Hn>, host path digest. + Ha, a host ofthe~~Type-P-Spatial-One-way-Delay-Vector <T2,dT2.1, dT2.2,..., dT2,n,dT2>~~path digest different from Dst and Hb; + Hb, a hostof the~~packet P2. Type-P-Spatial-One-way-Jitter-Vector metric is defined as~~path digest different from Src and Ha. Hb order inthepath must greater that Ha; + <T1, ..., Tk>, a list of time ordered by k; + dT1,..., dTn a list of delay; 5.1.3. Metric Units Asequence of~~values <T2-T1,dT2.1-dT1.1,dT2.2-dT1.2,...,dT2.n- dT1.n,dT2-dT1> Such that for each Hi~~delay 5.1.4. Definition Given 2 hosts Ha and Hbof the path~~<H1,~~<Src, H1,H2,...,~~Hn>, dT2.i-dT1.i is either~~Hn, Dst>, givena~~real number if the~~flow ofpackets~~P1 and P2 passes Hi at wire-time (last bit) dT1.i, respectively dT2.i, or undefined if~~of Type-P sent from Src to Dstat~~least one~~the times T1, T2... Tn. At eachof~~them never passes Hi. T2-T1~~these times, we obtain a Type-P-Spatial-One- way-Delay-Vector <T1,dT1.a, ..., dT1.b,...,, dT1.n,dT1>. We define the value of the sample Type-P-segment-One-way-Delay-Stream as the sequence made up of the delays dTk.b - dTk.a. dTk.ais the~~inter-packet emission interval~~delay between Srcand~~dT2-dT1~~Ha. dTk.bis~~ddT*~~the~~Type-P-One-way-ipdv~~delay between Src and Hb. 'dTk.b - dTk.a' is the one-way delay experienced by the packet sent by Srcat~~T1,T2*. 4.4.5. Sections in progress See sections 3.5~~the time Tk when going from Hato~~3.7 of [RFC3393]. 4.5. Pure Passive Metrics Spatial metrics may be measured without injecting test traffic. 4.5.1.~~Hb. 5.1.5.Discussion~~on Passive measurement One might says that most of the operational~~Following are specificissues~~occur in~~which may occur: o When a is Src <Tk,dTk.b - dTk.a> isthe~~last mile and that consequently such~~measure~~are less useful than active 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. 4.5.1.1. Passive One way delay As~~the~~packet~~first hop. o When b is Dst <Tk,dTk.b - dTk.a>is~~not a test packet, it does not include~~the~~time it was sent. Consequently a point~~measureof~~interest Hi ignores~~the~~time~~last hop. othe~~packet was send. So It~~delay looks to decrease: dTi > DTi+1: * Thisis~~not possible~~typically duto~~measure the delay between Src and Hi~~clock synchronisation issue. this point is discussedin the~~same manner it is not possible~~section 3.7.1. "Errors or uncertainties relatedto~~measure~~Clocks" of of [RFC2679]; * This may occurs too whenthe~~delay betwwen Hi and Dst. 4.5.1.2. Passive Packet loss The packet~~clock resolution of one probeis~~not~~bigger than the minimum delay ofa~~test packet, so it does not include~~path. As an example this happen when measuring the delay ofa~~sequence number. Packet lost measurement doe not require time synchronization and require only~~path which is 500 km long withone~~point~~probe synchronized using NTP having a clock resolutionof~~observation. Nevertheless it requires the point~~8ms. o The locationof~~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~~inthe~~time~~device influences the result. Ifthe packet is~~send because the packet does~~not~~carry~~observed onthe~~time it was injected in~~input interfacethe~~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~~includes bufferingtime~~when H1 (the first passive probe of the path) observed~~and consequently an uncertainty due tothe~~packet. 4.5.2. Reporting~~difference between 'wire time'and~~composition To avoid misunderstanding~~'host time'; o dTk.b may be observedandnot 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 forcedto~~address specific reporting constraint a proposal consists in defining distinct~~Tk+dTk.a. This motivate separatemetricsnamesfor pure passive measurement~~based on the definition above. It is crucial to know~~or specific reporting information. o Pure passive measure should consider packets ofthe~~methodologies used because~~same size andof the~~difference~~same Type-P. 5.2. A Definitionof~~method~~a sampleof~~detection (expecting Seq++); because~~Packet Loss of a segmentof the~~difference~~path This metric defines a sampleof~~source~~Packet lost between a pairof~~time (H1 vs Src) and because~~hostsofa path. 5.2.1. Metric Name Type-P-segment-Packet-loss-Stream 5.2.2. Metric Parameters + Src*,the~~difference of behaviour~~IP addressof the~~source (Poisson/unknown). 4.5.3. naming and registry Having distinct metrics identifiers for spatial metrics and passive spatial metrics in~~sender. + Dst*,the~~[RFC4148] will avoid interoperability 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 4.6. Discussion on spatial statistics Do we define min, max, avg~~IP addressof~~spatial metrics ? having~~the~~maximum loss metric value could be interesting. Say,~~receiver. + P*,the~~segment between router A and B always contributes loss metric value~~specificationof~~"1" means it could be~~the~~potential problem segment. Uploading dTi of each Hi consume~~packet type. + k, An integer which orders the packets sent. + n, An integer which orders the hosts on the path. + <H1, H2,..., Hn>, hosts path digest. + Ha,a~~lot~~hostof~~bandwidth. Computing statistics (min, max~~the path digest different from Dstand~~avg)~~Hb; + Hb, a hostof~~dTi locally~~the path digest different from Src and Ha. Hb orderin~~each Hi reduce~~the~~bandwidth consumption. 5. One-to-group metrics definitions 5.1.~~path must greater that Ha; + Hi, exchange points of the path digest. + <B1, B2, ..., Bn> a list of bits. + <L1, L2, ..., Ln> a list of integers. 5.2.3. Metric UnitsAsequence of integers <L1, L2,..., Lk> 5.2.4.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~~Given 2 hosts Ha and Hbofthe path <Src, H1, H2,..., Hn, Dst>, givena~~host acting as~~flow of packets of Type-P sent from Src to Dst atthe~~source. o Recv1,..., RecvN,~~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 definethe~~IP addresses~~valueof the~~N hosts acting~~sample Type-P-segment-Packet-Lost-Stream between Ha and Hbas~~receivers.~~the sequence made up of the integer <L1, L2,..., Lk> such that for each Tk:o~~T,~~a~~time. o dT1,...,dTn~~value of Lk of 0 means that Bk.a hasa~~list~~valueof~~time.~~0 (observed) and that Bk.b have a value of 0 (observed);o~~P, the specification~~a valueof~~the packet type.~~Lk of 1 means that Bk.a has a value of 0 (observed) and that Bk.b have a value of 1 (not observed);o~~Gr, the multicast group address (optional).~~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). 5.2.5. DiscussionThe~~parameter Gr~~semantic of a Type-P-segment-Packet-loss-Streamissimilar tothe~~multicast group address if~~one of Type-P-Packet-loss-Stream: o a value of 0 means thatthe~~measured packets are transmitted~~packet was observedby~~multicast. This parameter is~~Ha (similarto~~identify the measured traffic from other unicast~~'send by Src')and~~multicast traffic. It~~not observed by Hb ( similar to 'not received by Dst'); 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'). This definition of Type-P-segment-Packet-loss-Streamis~~set~~similarto~~be optional~~the Type-P-Packet-loss-Stream defined in [RFC2680] excepted thatina Type-P-segment-Packet-loss-Streamthe~~metric to avoid losing any generality, i.e. to make~~rules ofthe~~metric also applicable to unicast measurement where there is only one receivers. 5.1.3. Metric Units The value~~pointof~~a Type-P-one-to-group-One-way-Delay-Vector is~~interests Ha and Hb are symetrical: The asumption thata set of~~singletons metrics Type-P-One-way-Delay [RFC2679]. 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~~packets are going from Ha to Hb does not apply to Type-P-segment-Packet-loss- Stream because asthehost path digest is dynamic eachpacket~~at~~has its own host path digest. Makingthe~~time { T+dT1,...,T+dTn },~~asumption that the host path digest ofa~~Type-P-one-to-group-One-way-Delay-Vector is defined as~~Type-P-spatial- Packet-loss-vector does not change and thatthe set of~~the Type-P-One-way-Delay singleton between Src~~(Hk, Hk+1) tuples is mostly stable over time lead to unusable resultsand~~each receiver with value~~to the introductionof~~{ 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~~mistakes inthe~~source. o Recv1,..., RecvN,~~metrics aggregation processes. The right approach consists in carefully scruteningthe~~IP addresses~~path ordering information to build sample with elementsofvectors sharingthe~~N hosts acting as receivers. o T,~~same properties in term of Ha and Hb and 'Ha to Hb'. Soa~~time. o T1,...,Tn~~measure of Type-P-spatial-Packet-loss-vector differs froma~~list~~Type-P-Packet-loss one in that it produces different samplesofpacket loss overtime.~~o P, the specification~~The semanticof~~the packet type.~~a Type-P-segment-Packet-loss-Stream defines 2 new results:o~~Gr, the multicast group address (optional). 5.2.3. Metric Units The~~Avalue of~~a Type-P-one-to-group-One-way-Packet-Loss-Vector is a set~~Lkof~~singletons metrics Type-P-One-way-Packet-Loss [RFC2680]. 5.2.4. Definition Given~~2 (1,0) corresponds toa~~Type P packet sent by~~mistake inthe~~source Src at T~~ordering of HaandHb overthe~~N hosts, Recv1,...,RecvN, which should receive~~path coming either fromthe~~packet at T1,...,Tn, a Type-P-one-to-group-One-way-Packet-Loss-Vector~~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. Itis~~defined as~~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. o A value of Lk of 3 (1,1) corresponds toa~~set~~lostof the~~Type-P-One-way-Packet-Loss singleton between Src and each~~packet in upper segmentof the~~receivers {<T1,0|1>,<T2,0|1>,..., <Tn,0|1>}.~~path.5.3. A Definition~~for one-to-group~~of a sample ofOne-way~~Jitter~~Ipdv of a segment of the path This metric defines a sample of ipdv between a pair of hosts of a path. Editor note: work in progress5.3.1. Metric Name~~Type-P-one-to-group-One-way-Jitter-Vector~~Type-P-Segment-Ipdv-Stream5.3.2. Metric Parameters~~+ Src, the IP address of a host acting as the source. + Recv1,..., RecvN,~~5.3.3. Metric Units 5.3.4. Definition 5.3.5. Discussion 5.4. Discussion on Passive Segment Metrics A pure passive spatial measure isthe~~IP addresses~~measureof~~the N hosts acting as receivers. + T1, a time. + T2, a time. + ddT1,...,ddTn,~~a~~list of time. + P,~~spatial metric based onthe~~specification~~observation of user traffic insteadof~~the packet type. + F, a selection function defining unambiguously the two~~packets~~from~~dedicated tothe~~stream selected for~~measure. This section discussesthe~~metric. + Gr,~~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. To permit comparison and discussion, we firstly define pure passive measurement methodology followingthe~~multicast group address (optional) 5.3.3. Metric Units The value~~spiritof~~a Type-P-one-to-group-One-way-Jitter-Vector is a set~~IPPM framework [RFC2330] and the methodologyof~~singletons~~[RFC2679]. Then we propose several passivemetrics~~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~~complying to this framework. 5.4.1. A methodololyfor~~two packets~~passive segment metrics The following startsfrom the~~source Src to the N hosts {Recv1,...,RecvN },which are selected by the selection function F, as~~point thatthe~~difference between~~time a packet is sent is not needed to measurethe~~value~~delay from one host Haof the~~Type-P-one-to-group-One-way- Delay-Vector from Src~~pathto~~{ Recv1,..., RecvN } at time T1 and~~another host Hb. Generally, forthe~~value~~packetsof~~the Type-P-one-to-group- One-way-Delay-Vector from Src to { Recv1,...,RecvN } at~~Type-P and length L sent atime~~T2. T1 is~~<T1, T2,..., Tn> bythe~~wire-time at which~~sourceSrc~~sent the first bit~~pure passive methodology might proceed as follows: o Each pointof~~the first packet,~~interest Haand~~T2 is the wire-time at which Src sent~~Hb prepares to capture these packets; o Each point of interest Ha and Hb takes a timestamp Ti', determinesthe~~first bit~~internal delay correction dTi' (See section 3.7.1. "Errors or uncertainties related to Clocks" of [RFC2679]), o Each pointsofinterest Ha and Hb extractsthe~~second packet. This metric is derived~~path ordering informationfrom the~~Type-P-one-to- group-One-way-Delay-Vector metric. Therefore, for a set~~packet (e.g. time-to-live) o Each pointsof~~real number {ddT1,...,ddTn},Type-P-one- to- group-One-way-Jitter-Vector from~~interest Ha and Hb computes the wiretime fSromSrc to~~{ Recv1,...,RecvN } at T1, T2 is {ddT1,...,ddTn} means that Src sent two packets,~~Hi: Ti = Ti' - dTi'. ; o The reference point gathers individual information forthe~~first at wire-time T1 (first bit),~~packets sent a time <T1, T2,..., Tn> from each point of interest Haand~~the second at wire-time T2 (first bit)~~Hbandproceeds as follow: * Orders them according tothe~~packets were received by { Recv1,...,RecvN } at wire-time {dT1+T1,...,dTn+T1}(last bit of~~path ordering information; * Extractsthe~~first packet),~~timestamps Ti.aand~~at wire-time {dT'1+T2,...,dT'n+T2} (last bit of~~Ti+1.b. This arrival time is undefined (infinite) ifthe~~second packet), and that {dT'1-dT1,...,dT'n-dTn} ={ddT1,...,ddTn}. 6. One-to-Group Sample Statistics The defined one-to-group metrics above can all be directly achieved~~packet is not detected; * Computes the one-way-delayfromHa to Hb as (Ti+1.b - Ti.a). The delay is undefined (infinite) ifthe~~relevant unicast one-way metrics. They managed~~packet is not detected in Ha or Hb; o The reference point builds the segment sample <T1.b - T1.a, T2.b - T2.a,..., Tn.b - Tn.a> from Hato~~collect all unicast measurement results~~Hb; 5.4.2. Discussion on passive methodololy Intrinsically passive methodololy does not known (neither in the pointsof~~one-way metrics together~~interest norin~~one profile~~the point of reference) the time each packet is sent <T1, T2,..., Tn>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~~timeeach~~branch of~~packet it received. Section 5.4.1 shows thata~~multicast routing tree. However, these metrics can~~passive segment one-way delay measure doesnot~~be directly used~~rely on the time T the packet is sentto~~conveniently present~~computethe~~performance in terms of~~delay froma~~group and neither~~host Hato~~identify~~a host Hb. Intuitively, packets loss measurement does not require any time information and only expectsthe~~relative performance situation. From~~packet was sent. Passive packet loss methodology relies onthe~~performance point~~detectionof~~view,~~the~~multiparty communication services~~packet by one point of interest andnot~~only require the absolute performance support but also the relative performance.~~by another. This relies on asumptions similar to spatial methodology: oThe~~relative performance means the difference between absolute performance~~knowledgeof~~all users. Directly using the one-way metrics cannot present~~the~~relative performance situation. However, if we use~~path andthe~~variations~~orderof~~all users one-way parameters, we can have new metrics to measure~~the~~difference~~pointsofinterest overthe~~absolute performance~~path; o The packet is observed by one point of interestand~~hence provide~~not by another; Nevertheless, passive packet loss measure is limited bythe~~threshold value of relative performance~~fact that informationthatneithera~~multiparty service might demand. A very good example of~~packet has be sent nor thatthe~~high relative performance requirement~~packet was receivedisnever available: whenthe~~online gaming. A very light difference in delay might result in failure in~~path changes andthe~~game. We have to use multicast specific statistic metrics~~packet is not observed it is not deterministicto~~define exactly how small~~state thatthe~~relative delay~~packet is lost becausethe~~online gaming requires. There are many other services, e.g. online biding, online stock market, etc.,~~measure does not knownthat~~require multicast metrics in order~~the packet is received by Dst. when the measure does not observe any packets it is not possibleto~~evaluate~~state that all packets are lost becausethe~~network against their requirements. Therefore, we can see~~measure does not known that any packets were sent. The drawback is that monitoring finely these events is crucial for troubleshooting workflow. IPPM framework relies onthe~~importance~~mesureof~~new, multicast specific, statistic~~the behavior of packets of the same size. Consequently a passive metric sample MUST not mix information of packets of different sizes. Segmentmetricsmay be measured using pure passive technics. Passive segment metrics definitions are very closedto~~feed this need. We might also use some one-to-group statistic conceptions to present and report the group performance and relative performance~~spatial segment metrics definitions. Therefore below we just name passive segment metricsto~~save~~distinguishthe~~report transmission bandwidth. Statistics have been defined~~methodology used. Having distinct metrics identifiersfor~~One- way~~spatial metrics and passive spatialmetrics in~~corresponding FRCs. They provide~~the~~foundation~~[RFC4148] will avoid interoperability issues especially during compositionofmetrics the IPPM WG is currently defining. 5.4.3. Passive Segment metrics 5.4.3.1. Passive Segment One way Delay metric This metricdefinition~~for performance statistics. For instance, there are definitions for minimum and maximum One-way delay in [RFC2679]. 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~~based onthe~~time dimension while~~top ofthe~~later one can have statistics over both time and space dimensions.~~Type-P-spatial- segment-One-way-Delay-Stream metric definition. name: Type-P-Passive-Segment-One-way-Delay-Stream 5.4.3.2. Passive Segment Packet Loss metricThis~~space dimension~~metric definitionis~~introduced by~~based onthe~~Matrix concept as illustrated in Figure 7. For a Matrix M each row is a set~~topof~~One-way singletons spreading over~~the~~time dimension and each column~~Type-P-spatial- segment-Packet-Loss-Stream metric definition. name: Type-P-Passive-Segment-Packet-Loss-Stream 5.4.3.3. Passive Segment One-way Ipdv metric This metric definitionis~~another set~~based on the topof~~One-way singletons spreading over~~the~~space dimension. Receivers Space ^ 1 | / R1dT1 R1dT2 R1dT3 ... R3dTk \ | | | 2 | | R2dT1 R2dT2 R2dT3 ... R3dTk | | | | 3 | | R3dT1 R3dT2 R3dT3 ... R3dTk | . | | | . | | | . | | | n | \ RndT1 RndT2 RndT3 ... RndTk / +--------------------------------------------> time T0 Figure 7: Matrix M (n*m) In Matrix M, each element is a~~Type-P-Segment- Ipdv-Stream metric definition. name: Type-P-Passive-Segment-One-way-Ipdv-Stream 6. One-to-group metrics definitions 6.1. A Definition for one-to-groupOne-way~~delay singleton. Each column is a delay vector contains~~Delay 6.1.1. Metric Name Type-P-one-to-group-One-way-Delay-Vector 6.1.2. Metric Parameters o Src,the~~One-way delays~~IP addressofa host acting asthe~~same packet observed at M points of interest. It implies~~source. o Recv1,..., RecvN,the~~geographical factor~~IP addressesof the~~performance within a group. Each row is~~N hosts acting as receivers. o T,a~~set of One-way delays observed during~~time. o dT1,...,dTna~~sampling interval at one~~listoftime. o P,the~~points~~specificationof~~interest. It presents~~the~~delay performance at a receiver over~~packet type. o Gr,the~~time dimension. Therefore, one can either calculate statistics by rows over~~multicast group address (optional). The parameter Gr isthe~~space dimension or by columns over the time dimension. It's up to~~multicast group address ifthe~~operators or service provides which dimension they~~measured packetsare~~interested in. For example, a TV broadcast service provider might want~~transmitted by multicast. This parameter isto~~know~~identifythe~~statistical performance of each user in a long term run to make sure their services are acceptable~~measured traffic from other unicastand~~stable. While for an online gaming service provider, he might be more interested~~multicast traffic. It is setto~~know if all users are served fairly by calculating~~be optional inthe~~statistics over~~metric to avoid losing any generality, i.e. to makethe~~space dimension. This memo does not intend~~metric also applicableto~~recommend which~~unicast measurement where there is only one receivers. 6.1.3. Metric Units The value of a Type-P-one-to-group-One-way-Delay-Vector is a setofsingletons metrics Type-P-One-way-Delay [RFC2679]. 6.1.4. Definition Given a Type P packet sent bythe~~statistics are better than~~source Src at Time T, giventhe~~other. To save~~N hosts { Recv1,...,RecvN } which receivethe~~report transmission bandwidth, each point of interest can send statistics in a pre-defined time interval to~~packet atthe~~reference point rather than sending every One-way singleton it observed. As long as an appropriate~~time~~interval is decided, appropriate statistics can represent the performance in~~{ T+dT1,...,T+dTn },a~~certain accurate scale. How to decide~~Type-P-one-to-group-One-way-Delay-Vector is defined asthe~~time interval and how to bootstrap all points~~setof~~interest and the reference point depend on applications. For instance, applications with lower transmission rate can have~~the~~time interval longer~~Type-P-One-way-Delay singleton between Srcand~~ones~~each receiverwith~~higher transmission rate can have~~value of { dT1, dT2,...,dTn }. 6.2. A Definition for one-to-group One-way Packet Loss 6.2.1. Metric Name Type-P-one-to-group-One-way-Packet-Loss-Vector 6.2.2. Metric Parameters o Src,the~~time interval shorter. However, this is out~~IP addressofa host acting asthe~~scope~~source. o Recv1,..., RecvN, the IP addressesof~~this memo. Moreover, after knowing~~the~~statistics over~~N hosts acting as receivers. o T, a time. o T1,...,Tn a list of time. o P,the~~time dimension, one might want to know how this statistics distributed over~~specification ofthe~~space dimension. For instance,~~packet type. o Gr, the multicast group address (optional). 6.2.3. Metric Units The value ofa~~TV broadcast service provider had~~Type-P-one-to-group-One-way-Packet-Loss-Vector is a set of singletons metrics Type-P-One-way-Packet-Loss [RFC2680]. 6.2.4. Definition Given a Type P packet sent bythe~~performance Matrix M~~source Src at Tand~~calculated~~the~~One-way delay mean over~~N hosts, Recv1,...,RecvN, which should receivethe~~time dimension to obtain~~packet at T1,...,Tn,a~~delay Vector~~Type-P-one-to-group-One-way-Packet-Loss-Vector is definedas~~{V1,V2,..., VN}. He then calculated~~a set ofthe~~mean~~Type-P-One-way-Packet-Loss singleton between Src and eachof~~all~~the~~elements in~~receivers {<T1,0|1>,<T2,0|1>,..., <Tn,0|1>}. 6.3. A Definition for one-to-group One-way Ipdv 6.3.1. Metric Name Type-P-One-to-group-One-way-ipdv-Vector 6.3.2. Metric Parameters + Src,the~~Vector to see what level~~IP addressof~~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~~host acting as the source. + Recv1,..., RecvN, the IP addressesof~~users during~~the N hosts acting as receivers. + T1,a~~sampling interval in terms~~time. + T2, a time. + ddT1,...,ddTn, a listof~~delay. It needs twice calculation to have this statistic over both time and space dimensions. We name this kind~~time. + P, the specificationof~~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~~the packet type. + F,a~~2-level statistic is calculated first,~~selection function defining unambiguouslythe~~results are~~two packets fromthe~~same. I.e. one can calculate~~stream selected forthe~~2-level delay mean using~~metric. + Gr,the~~Matrix M~~multicast group address (optional) 6.3.3. Metric Units 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]. 6.3.4. Definition Given a Type P packet stream, Type-P-one-to-group-One-way-ipdv-Vector is defined for two packets from the source Src to the N hosts {Recv1,...,RecvN },which are selectedby~~having~~the~~1-level delay mean over~~selection function F, as the difference between the value oftheType-P-one-to-group-One-way- Delay-Vector from Src to { Recv1,..., RecvN } attime~~dimension first~~T1and~~then calculate~~the~~mean~~valueof the~~obtained vector~~Type-P-one-to-group- One-way-Delay-Vector from Srcto~~find out~~{ Recv1,...,RecvN } at time T2. T1 isthe~~2-level delay mean. Or, he can do~~wire-time at which Src sentthe~~1-level statistic calculation over~~first bit ofthe~~space dimension~~firstpacket,and~~then have the 2-level delay mean. Both two results will be exactly the same. Therefore, when define a 2-level statistic, there~~T2is~~no need to specify in which procedure~~the~~calculation should follow. Comment: The above statement depends on whether~~wire-time at which Src sentthe~~order~~first bitof~~operations has any affect on~~the~~outcome. Many statistics can be defined for the proposed one-to-group metrics over either the space dimension or the time dimension or both.~~second packet.This~~memo treats~~metric is derived fromthe~~case where~~Type-P-one-to- group-One-way-Delay-Vector metric. Therefore, fora~~stream~~setof~~packets~~real number {ddT1,...,ddTn},Type-P-one- to- group-One-way-ipdv-Vectorfrom~~the Source results in a sample~~Src to { Recv1,...,RecvN }at~~each of the Receivers in~~T1, T2 is {ddT1,...,ddTn} means that Src sent two packets,the~~Group,~~first at wire-time T1 (first bit),and~~these samples are each summarized with the usual statistics employed in one-to-one communication. New statistic definitions are presented, which summarize the one-to-one statistics over all the Receivers in the Group. 6.1. Discussion on~~the~~Impact of packet loss on statistics The packet loss does have effects on one-way metrics~~second at wire-time T2 (first bit)and~~their statistics. For example, the lost packet can result an infinite one- way delay. It is easy to handle~~the~~problem~~packets were receivedby~~simply ignoring the infinite value in~~{ Recv1,...,RecvN } at wire-time {dT1+T1,...,dTn+T1}(last bit ofthe~~metrics~~first packet),and~~in the calculation~~at wire-time {dT'1+T2,...,dT'n+T2} (last bitof the~~corresponding statistics. However, the packet loss has so strong impact on the statistics calculation for the~~second packet), and that {dT'1-dT1,...,dT'n-dTn} ={ddT1,...,ddTn}. 7. One-to-Group Sample Statistics The definedone-to-group metrics~~that it~~abovecan~~not~~allbe~~solved by~~directly achieved fromthe~~same method used for~~relevant unicastone-way metrics.~~This is due~~They managedto~~the complex of building a Matrix, which is needed for calculation of the statistics proposed in this memo. The situation is that~~collect all unicastmeasurement results~~obtained by different end users might have different packet loss pattern. For example, for User1, packet A was observed lost. And for User2, packet A was successfully received but packet B was lost. If the method to overcome the packet loss for~~ofone-way metrics~~is applied, the two singleton sets reported~~together in one profile and sort themby~~User1~~receiversand~~User2 will be different~~packets in a multicast group. They can provide sufficient information regarding the network performancein terms of~~the transmitted packets. Moreover, if User1~~each receiverand~~User2 have different number of lost packets, the size~~guide engineers to identify potential problem happened on each branchof~~the results will be different. Therefore, for the centralized calculation, the reference point will~~a multicast routing tree. However, these metrics cannot be~~able to use these two results~~directly usedto~~build up~~conveniently presenttheperformance in terms of agroup~~Matrix~~and~~can not calculate the statistics. In an extreme situation, no single packet arrives all users in~~neither to identifythe~~measurement and~~relative performance situation. Fromthe~~Matrix will be empty. One~~performance pointofview,the~~possible solutions is to replace~~multiparty communication services not only requirethe~~infinite/undefined delay value by~~absolute performance support but alsothe~~average~~relative performance. The relative performance means the difference between absolute performanceofall users. Directly usingthe~~two adjacent values. For example, if~~one-way metrics cannot presentthe~~result reported by user1 is { R1dT1 R1dT2 R1dT3 ... R1dTK-1 UNDEF R1dTK+1... R1DM } where "UNDEF" is an undefined value,~~relative performance situation. However, if we usethe~~reference point~~variations of all users one-way parameters, wecan~~replace it by R1dTK = {(R1dTK-1)+( R1dTK+1)}/2. Therefore, this result can be used~~have new metricsto~~build up the group Matrix with an estimated value R1dTK. There are other possible solutions such as using~~measurethe~~overall mean~~differenceof the~~whole result to replace the infinite/undefined value,~~absolute performanceand~~so on. It is out of~~hence providethe~~scope~~threshold value of relative performance that a multiparty service might demand. A very good exampleof~~this memo. For~~the~~distributed calculation,~~high relative performance requirement isthe~~reported statistics~~online gaming. A very light difference in delaymightresult in failure in the game. Wehave~~different "weight"~~to~~present~~use multicast specific statistic metrics to define exactly how smallthe~~group performance, which is especially true for~~relativedelay~~and jitter relevant metrics. For example, User1 calculates~~the~~Type-P-Finite-One-way-Delay-Mean R1DM as shown~~online gaming requires. There are many other services, e.g. online biding, online stock market, etc., that require multicast metricsin~~Figure. 8 without any packet loss and User2 calculates~~order to evaluatethe~~R2DM 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 in~~network against their requirements. Therefore, we can seethe~~whole sample interval. One possible solution is~~importance of new, multicast specific, statistic metricstofeed this need. We might alsouse~~a weight factor to mark every~~some one-to-groupstatistic~~value sent by users~~conceptions to presentand~~use this factor for further statistic calculation. 6.2. General Metric Parameters o Src,~~reportthe~~IP address of a host o G,~~group performance and relative performance to savethe~~Group IP address o N, the number of Receivers (Recv1, Recv2, ... RecvN) o T, a time (start of test interval) o Tf, a time (end of test interval) o K, the number of packets sent from the source during the test interval o J[n], the number of packets received at a particular Receiver, n, where 1<=n<=N o lambda, a rate~~report transmission bandwidth. Statistics have been defined for One- way metricsin~~reciprocal seconds (for Poisson Streams) o incT,~~corresponding RFCs. They providethe~~nominal duration~~foundationof~~inter-packet interval, first bit to first bit (for Periodic Streams) o T0,~~definition for performance statistics. For instance, there are definitions for minimum and maximum One-way delay in [RFC2679]. However, there isa~~time that MUST be selected at random from~~dramatic difference betweenthe~~interval [T, T+I] to start generating packets~~statistics for one-to-one communicationsand~~taking measurements (for Periodic Streams) o TstampSrc,~~for one-to-many communications. The former one only has statistics overthe~~wire~~time~~of the packet as measured at MP(Src) (the Source Measurement Point) o TstampRecv,~~dimension whilethe~~wire~~later one can have statistics over bothtime~~of~~and space dimensions. This space dimension is introduced bythe~~packet~~Matrix conceptas~~measured at MP(Recv), assigned to packets that arrive within~~illustrated in Figure 9. Fora~~"reasonable" time o Tmax,~~Matrix M each row isa~~maximum waiting time for packets at the destination,~~set~~sufficiently long to disambiguate packets with long delays from packets that are discarded (lost), thus the distribution~~of~~delay~~One-way singletons spreading over the time dimension and each columnis~~not truncated o dT, shorthand notation for a one-way delay singleton value 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 the destination within TstampSrc + Tmax, may be indexed~~another set of One-way singletons spreadingover~~n Receivers o DV, shorthand notation for a one-way delay variation singleton value 6.3. One-to-Group one-way Delay Statistics This section defines the overall one-way delay statistics for an entire Group or receivers. For example, we can define the group mean delay, as illustrated below. This is a metric designed to summarize~~the~~entire Matrix. Recv /----------- Sample -------------\ Stats Group Stat~~space dimension. Receivers Space ^1| /R1dT1 R1dT2 R1dT3 ...~~R1dTk R1DM~~R3dTk\ || |2| |R2dT1 R2dT2 R2dT3 ...~~R2dTk R2DM~~R3dTk | || | 3| |R3dT1 R3dT2 R3dT3 ... R3dTk~~R2DM > GMD~~|. || |. || |. || |n| \RndT1 RndT2 RndT3 ... RndTk~~RnDM~~/+--------------------------------------------> time T0Figure~~8: One-to-GroupGroup Mean Delay where: R1dT1~~9: Matrix M (n*m) 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 observed at M points of interest. It implies the geographical factor of the performance within a group. Each rowisa 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 columns 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 fairly by calculating the statistics over the space dimension. This memo does not intend 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 statistics can 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 dimension first and then have the 2-level delay mean. Both two results will be exactly the same. Therefore, when define a 2-level statistic, there is no need to specify in which procedure the calculation should follow. Comment: The above statement depends on whether the order of operations has any affect on the outcome. Many statistics can be defined for the proposed one-to-group metrics over either the space dimension or the time dimension or both. This 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 samples are each summarized with the usual statistics employed in one-to-one communication. New statistic definitions are presented, which summarize the one-to-one statistics over all the Receivers in the Group. 7.1. Discussion on the Impact of packet loss on statistics The packet loss does have effects on one-way metrics and their statistics. For example, the lost packet can result an infinite one- way delay. It is easy to handle the problem by simply ignoring the infinite value in the metrics and in the calculation of the corresponding statistics. However, the packet loss has so strong 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 metrics. This is due to the complex of building a Matrix, which is needed for calculation of the statistics proposed in this memo. The situation is that measurement results obtained by different end users might have different packet loss pattern. For example, for User1, packet A was observed lost. And for User2, packet A was successfully received but packet B was lost. If the method to overcome the packet loss for one-way metrics is applied, the two singleton sets reported by User1 and User2 will be different in terms of the transmitted packets. Moreover, if User1 and User2 have different number of lost packets, the size of the results will be different. Therefore, for the centralized calculation, the reference point will not be able to use these two results to build up the group Matrix and can not calculate the statistics. In an extreme situation, no single packet arrives all users in the measurement and the Matrix will be empty. One of the possible solutions is to replace the infinite/undefined delay value by the average of the two adjacent values. For example, if the result reported by user1 is { R1dT1 R1dT2 R1dT3 ... R1dTK-1 UNDEF R1dTK+1... R1DM } where "UNDEF" is an undefined value, the reference point can replace it by R1dTK = {(R1dTK-1)+( R1dTK+1)}/2. Therefore, this result can be used to build up the group Matrix with an estimated value R1dTK. There are 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 of the scope of this memo. For the distributed calculation, the reported statistics might have different "weight" to present the group performance, which is especially true for delay and ipdv relevant metrics. For example, User1 calculates the Type-P-Finite-One-way-Delay-Mean R1DM as shown in Figure. 8 without any packet loss and User2 calculates the R2DM 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 in the whole sample interval. One possible solution is to use a weight factor to mark every statistic value sent by users and use this factor for further statistic calculation. 7.2. General Metric Parameters o Src, the IP address of a host o G, the Group IP address o N, the number of Receivers (Recv1, Recv2, ... RecvN) o T, a time (start of test interval) o Tf, a time (end of test interval) o K, the number of packets sent from the source during the test interval o J[n], the number of packets received at a particular Receiver, n, where 1<=n<=N o lambda, a rate in reciprocal seconds (for Poisson Streams) o incT, the nominal duration of inter-packet interval, first bit to first bit (for Periodic Streams) o T0, a time that MUST be selected at random from the interval [T, T+I] to start generating packets and taking measurements (for Periodic Streams) o TstampSrc, the wire time of the packet as measured at MP(Src) (the Source Measurement Point) o TstampRecv, the wire time of the packet as measured at MP(Recv), assigned to packets that arrive within a "reasonable" time o Tmax, a maximum waiting time for packets at the destination, set sufficiently long to disambiguate packets with long delays from packets that are discarded (lost), thus the distribution of delay is not truncated o dT, shorthand notation for a one-way delay singleton value 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 the destination within TstampSrc + Tmax, may be indexed over n Receivers o DV, shorthand notation for a one-way delay variation singleton value 7.3. One-to-Group one-way Delay Statistics This section defines the overall one-way delay statistics for an entire Group or receivers. For example, we can define the group mean delay, as illustrated below. This is a metric designed to summarize the whole matrix. Recv /----------- Sample -------------\ Stats Group Stat 1 R1dT1 R1dT2 R1dT3 ... R1dTk R1DM \ | 2 R2dT1 R2dT2 R2dT3 ... R2dTk R2DM | | 3 R3dT1 R3dT2 R3dT3 ... R3dTk R2DM > GMD . | . | . | n RndT1 RndT2 RndT3 ... RndTk RnDM / Figure 10: One-to-GroupGroup Mean Delay where: R1dT1 is the Type-P-Finite-One-way-Delay singleton evaluated at Receiver 1 for packet 1. R1DM is the Type-P-Finite-One-way-Delay-Mean evaluated at Receiver 1 for the sample of packets (1,...K). GMD is the mean of the sample means over all Receivers (1, ...N). 7.3.1. Definition and Metric Units 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 Receiver (Destination), as per [RFC2679]. For each packet that arrives within Tmax of its sending time, TstampSrc, the one-way delay singleton (dT) will be a finite value in units of seconds. Otherwise, the value of the singleton is Undefined. 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): Type-P-Finite-One-way-Delay-Receiver-n-[i] = = TstampRecv[i] - TstampSrc[i] The units of Finite one-way delay are seconds, with sufficient resolution to convey 3 significant digits. 7.3.2. Sample Mean Statistic This section defines the Sample Mean at each of N Receivers. Type-P-Finite-One-way-Delay-Mean-Receiver-n = RnDM = J[n] --- 1 \ --- * > Type-P-Finite-One-way-Delay-Receiver-n-[i] J[n] / --- i = 1 Figure 11: Type-P-Finite-One-way-Delay-Mean-Receiver-n where all packets i= 1 through J[n] have finite singleton delays. 7.3.3. One-to-Group Mean Delay Statistic This section defines the Mean One-way Delay calculated over the entire Group (or Matrix). Type-P-One-to-Group-Mean-Delay = GMD = N --- 1 \ - * > RnDM N / --- n = 1 Figure 12: Type-P-One-to-Group-Mean-Delay 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 number of Finite One-way Delay singletons. 7.3.4. One-to-Group Range of Mean Delays This section defines a metric for the range of mean delays over all N receivers in the Group, (R1DM, R2DM,...RnDM). Type-P-One-to-Group-Range-Mean-Delay = GRMD = max(RnDM) - min(RnDM) 7.3.5. One-to-Group Maximum of Mean Delays This section defines a metrics for the maximum of mean delays over all N receivers in the Group, (R1DM, R2DM,...RnDM). Type-P-One-to-Group-Max-Mean-Delay = GMMD = max(RnDM) 7.4. One-to-Group one-way Loss Statistics This section defines the overall 1-way loss statistics for an entire Group. For example, we can define the group loss ratio, as illustrated below. This is a metric designed to summarize the entire Matrix. Recv /----------- Sample ----------\ Stats Group Stat 1 R1L1 R1L2 R1L3 ... R1Lk R1LR \ | 2 R2L1 R2L2 R2L3 ... R2Lk R2LR | | 3 R3L1 R3L2 R3L3 ... R3Lk R3LR > GLR . | . | . | n RnL1 RnL2 RnL3 ... RnLk RnLR / Figure 13: One-to-Group Loss Ratio where: R1L1 is the Type-P-One-way-Loss singleton (L) evaluated at Receiver 1 for packet 1. R1LR is the Type-P-One-way-Loss-Ratio evaluated at Receiver 1 for the sample of packets (1,...K). GLR is the loss ratio over all Receivers (1, ..., N). 7.4.1. One-to-Group Loss Ratio The overall Group loss ratio id defined as Type-P-One-to-Group-Loss-Ratio = K,N --- 1 \ = --- * > L(k,n) K*N / --- k,n = 1 Figure 14 ALL Loss ratios are expressed in units of packets lost to total packets sent. 7.4.2. One-to-Group Loss Ratio Range Given a Matrix of loss singletons as illustrated above, determine the Type-P-One-way-Packet-Loss-Average for the sample at each receiver, 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- way-Loss-Ratio illustrated above are equivalent metrics. In terms of the parameters used here, these metrics definitions can be expressed as Type-P-One-way-Loss-Ratio-Receiver-n = RnLR = K --- 1 \ - * > RnLk K / --- k = 1 Figure 15: Type-P-One-way-Loss-Ratio-Receiver-n The One-to-Group Loss Ratio Range is defined as 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 minimum loss ratios for the Group, rather than only reporting the difference between them. 7.4.3. Comparative Loss Ratio Usually, the number of packets sent is used in the denominator of packet loss ratio metrics. For the comparative metrics defined here, the denominator is the maximum number of packets received at any receiver for the sample and test interval of interest. The Comparative Loss Ratio is defined as Type-P-Comp-Loss-Ratio-Receiver-n = RnCLR = K --- \ > Ln(k) / --- k=1 = ----------------------------- / K \ | --- | | \ | K - Min | > Ln(k) | | / | | --- | \ k=1 / N Figure 16: Type-P-Comp-Loss-Ratio-Receiver-n 7.5. One-to-Group one-way Delay Variation Statistics There are two delay variation (DV) statistics that summarize the performance over the Group: the maximum DV over all receivers and the 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) quantile of one-way delay minus the minimum one-way delay. 8. Measurement Methods: Scaleability and Reporting Virtually all the guidance on measurement processes supplied by the earlier IPPM RFCs (such as [RFC2679] and [RFC2680]) for one-to-one scenarios is applicable here in the spatial and multiparty measurement scenario. The main difference is that the spatial and multiparty configurations require multiple measurement points where a stream of singletons will be collected. The amount of information requiring storage grows with both the number of metrics and the number of measurement points, so the scale of the measurement architecture multiplies the number of singleton results that must be collected and processed. It is possible that the architecture for results collection involves a single aggregation point with connectivity to all the measurement points. In this case, the number of measurement points determines both storage capacity and packet transfer capacity of the host acting as the aggregation point. However, both the storage and transfer capacity can be reduced if the measurement points are capable of computing the summary statistics that describe each measurement interval. This is consistent with many operational monitoring architectures today, where even the individual singletons may not be stored at each measurement point. In recognition of the likely need to minimize form of the results for storage and communication, the Group metrics above have been constructed to allow some computations on a per-Receiver basis. This means that each Receiver's statistics would normally have an equal weight with all other Receivers in the Group (regardless of the number of packets received). 8.1. Computation methods The scalability issue can be raised when there are thousands of points of interest in a group who are trying to send back the measurement results to the reference point for further processing and analysis. The points of interest can send either the whole measured sample or only the calculated statistics. The former one is a centralized statistic calculation method and the latter one is a distributed statistic calculation method. The sample should include all metrics parameters, the values and the corresponding sequence numbers. The transmission of the whole sample can cost much more bandwidth than the transmission of the statistics that should include all statistic parameters specified by policies and the additional information about the whole sample, such asthe~~Type-P-Finite-One-way-Delay singleton evaluated at Receiver 1 for packet 1. R1DM is~~size ofthe~~Type-P-Finite-One-way-Delay-Mean evaluated at Receiver 1 for~~sample,the~~sample~~group address, the addressof~~packets (1,...K). GMD is~~the~~mean~~point of interest, the IDof the sample~~means~~session, and so on. Apparently, the centralized calculation method can require much more bandwidth than the distributed calculation method when the sample size is big. This is especially true when the measurement has huge number of the points of interest. It can lead to a scalability issue at the reference point byover~~all Receivers (1, ...N). 6.3.1. Definition~~load the network resources. The distributed calculation method can save much more bandwidthand~~Metric Units Using~~releasethe~~parameters above, we obtain~~pressure ofthe~~value~~scalability issue at the reference point side. However, it can result in the lackof~~Type-P-One-way- Delay singleton for~~information because notall~~packets sent during~~measured singletons are obtained for building upthe~~test interval at each Receiver (Destination), as per [RFC2679].~~group matrix. The performance over time can be hidden from the analysis.For~~each packet that arrives within Tmax of its sending time, TstampSrc,~~example, the loss pattern can be missed by simply accepting the loss ratio as well asthe~~one-way~~delay~~singleton (dT) will~~pattern. This tradeoff between the bandwidth consuming and the information acquiring has tobe~~a finite value in units of seconds. Otherwise,~~taken into account when design the measurement campaign to optimize the measurement results delivery. The possible solution could be to transit the statistic parameters to the reference point first to obtainthe~~value~~general informationof the~~singleton is Undefined. 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): Type-P-Finite-One-way-Delay-Receiver-n-[i] = = TstampRecv[i] - TstampSrc[i] The units of Finite one-way delay~~group performance. If the detail resultsare~~seconds, with sufficient resolution~~required, the reference point should send the requeststo~~convey 3 significant digits. 6.3.2. Sample Mean Statistic This section defines~~the~~Sample Mean at each~~pointsof~~N Receivers. Type-P-Finite-One-way-Delay-Mean-Receiver-n = RnDM = J[n] --- 1 \ --- * > Type-P-Finite-One-way-Delay-Receiver-n-[i] J[n] / --- i = 1 Figure 9: Type-P-Finite-One-way-Delay-Mean-Receiver-n where all packets i= 1 through J[n] have finite singleton delays. 6.3.3. One-to-Group Mean Delay Statistic This section defines~~interest, which could be particular ones orthe~~Mean One-way Delay calculated over~~whole group. This procedure can happen inthe~~entire Group (or Matrix). Type-P-One-to-Group-Mean-Delay = GMD = N --- 1 \ - * > RnDM N / --- n = 1 Figure 10: Type-P-One-to-Group-Mean-Delay Note that~~off peak time and can be well scheduled to avoid delivery of too many points of interest atthe~~Group Mean Delay~~same time. Compression techniquescan also be~~calculated~~used to minimize the bandwidth requiredby~~summing~~the~~Finite one-way Delay singletons~~transmission. This could be a measurement protocol to report the measurement results. It is out of the scope of this memo. 8.2. Measurement To prevent any biasin the~~Matrix,~~result, the configuration of a one-to-many measure must take in consideration that implicitly more packets will to be routed than sendand~~dividing by~~selects a test packets rate that will not impactthe~~number of Finite One-way Delay singletons. 6.3.4. One-to-Group Range~~network performance. 8.3. Effectof~~Mean Delays~~Time and Space Aggregation Order on StatsThis section~~defines a metric for~~presentsthe~~range~~impactof~~mean delays over all N receivers in~~the~~Group, (R1DM, R2DM,...RnDM). Type-P-One-to-Group-Range-Mean-Delay = GRMD = max(RnDM) - min(RnDM) 6.3.5. One-to-Group Maximum of Mean Delays This section defines a metrics for~~aggregation order onthe~~maximum~~scalabilityof~~mean delays over all N receivers in~~the~~Group, (R1DM, R2DM,...RnDM). Type-P-One-to-Group-Max-Mean-Delay = GMMD = max(RnDM) 6.4. One-to-Group one-way Loss Statistics This section defines~~reporting and ofthe~~overall 1-way loss statistics for an entire Group. For example, we can define~~computation. It makesthe~~group loss ratio,~~hypothesis that receivers are managed remotely and not co-located. multimetrics samples represented a matrixas illustrated~~below. This is a metric designed to summarize the entire Matrix. Recv /----------- Sample ----------\ Stats Group Stat~~below Point of interest1~~R1L1 R1L2 R1L3~~R1S1 R1S1 R1S1...~~R1Lk R1LR~~R1Sk\ | 2~~R2L1 R2L2 R2L3~~R2S1 R2S2 R2S3...~~R2Lk R2LR~~R2Sk| | 3~~R3L1 R3L2 R3L3~~R3S1 R3S2 R3S3...~~R3Lk R3LR~~R3Sk>~~GLR~~sample over space. | . | . | n~~RnL1 RnL2 RnL3~~RnS1 RnS2 RnS3...~~RnLk RnLR~~RnSk/S1M S2M S3M ... SnM Stats over space \------------- ------------/ \/ Stat over space and timeFigure~~11: One-to-Group Loss Ratio where: R1L1 is~~17: Impact of space aggregation on multimetrics Stat 2 methods are available to compute statistics onthe~~Type-P-One-way-Loss singleton (L) evaluated at Receiver 1 for packet 1. R1LR~~resulting matrix: o metric is computed over time and then over space; o metriciscomputed over space and then over time. They differ only bythe~~Type-P-One-way-Loss-Ratio evaluated at Receiver 1 for~~order ofthe~~sample~~time andof~~packets (1,...K). GLR is~~the~~loss ratio over all Receivers (1, ..., N). 6.4.1. One-to-Group Loss Ratio The overall Group loss ratio id defined~~space aggregation. Viewas~~Type-P-One-to-Group-Loss-Ratio = K,N --- 1 \ = --- * > L(k,n) K*N / --- k,n = 1 Figure 12 ALL Loss ratios are expressed in units of packets lost to total packets sent. 6.4.2. One-to-Group Loss Ratio Range Given~~a~~Matrix of loss singletons~~matrix this order is neutralas~~illustrated above, determine~~does not impactthe~~Type-P-One-way-Packet-Loss-Average for~~result, butthe~~sample at each receiver, according~~impact on a measurement deployment is critical. In both cases the volume of data to report is proportionalto the~~definitions and method~~numberof~~[RFC2680]. The Type-P- One-way-Packet-Loss-Average, RnLR for receiver n,~~probes. But there is a major difference between these 2 methods: method2: In spaceandtime aggregation modethe~~Type-P-One- way-Loss-Ratio illustrated above are equivalent metrics. In terms~~volumeof~~the parameters used here, these metrics definitions can be expressed as Type-P-One-way-Loss-Ratio-Receiver-n = RnLR = K --- 1 \ - * > RnLk K / --- k = 1 Figure 13: Type-P-One-way-Loss-Ratio-Receiver-n The One-to-Group Loss Ratio Range is defined as Type-P-One-to-Group-Loss-Ratio-Range = max(RnLR) - min(RnLR) It~~data to collectis~~most effective~~proportionalto~~indicate the range by giving both~~the~~max and minimum loss ratios~~number of test packets received; Each received packet RiSi triggers out a block of data that must be reported to a common placeforcomputingthe~~Group, rather than only reporting the difference between them. 6.4.3. Comparative Loss Ratio Usually,~~stat over space; method1: In time and space aggregation modethe~~number~~volumeof~~packets sent~~data to collectis~~used in~~proportional tothe~~denominator~~periodof~~packet loss ratio metrics. For the comparative metrics defined here, the denominator is~~aggregation, so it does not depend onthe~~maximum~~number of~~packets received at any receiver for the sample~~packet received; Method 2 property has severe drawbacks in terms of securityanddimensioning: The increasing of the rate of thetest~~interval~~packets may result in a sortof~~interest.~~DoS toward the computation points;The~~Comparative Loss Ratio~~dimensioning of a measurement systemis~~defined~~quite impossible to validate. The time aggregation interval provides the reporting side with a control of various collecting aspects suchas~~Type-P-Comp-Loss-Ratio-Receiver-n = RnCLR = K --- \ > Ln(k) / --- k=1 = ----------------------------- / K \ | --- | | \ | K - Min | > Ln(k) | | / | | --- | \ k=1 / N Figure 14: Type-P-Comp-Loss-Ratio-Receiver-n 6.5. One-to-Group one-way Delay Variation Statistics There~~bandwidth and computation and storage capacities. So this draft defines metrics based on method 1. Note: In some specific cases one may need sample of singletons over space. To address this need itis~~are two delay variation (DV) statistics~~suggested firstlyto~~summarize~~limitthe~~performance over~~number of test andthe~~Group:~~number of test packets per seconds. Then reducingthe~~maximum DV over all receivers and~~size ofthe~~range~~sample over time to one packet give sampleof~~DV~~singletonover~~all receivers. The detailed definitions~~space.. 8.3.1. Impact on group stats 2 methodsare~~T0 BE PROVIDED. 7. Measurement Methods: Scaleability and Reporting Virtually all~~available to compute group statistics: o method1: Figure 10 andFigure 13 illustratethe~~guidance on measurement processes supplied by~~method chosen:the~~earlier IPPM RFCs (such as [RFC2679] and [RFC2680]) for~~one-to-one~~scenarios~~statisticis~~applicable here in~~computed per interval of time beforethe~~spatial and multiparty measurement scenario. The main difference is that~~computation of the mean over the group of receivers; o method2: Figure 17 presentsthesecond one, metric is computed over space and then over time. 8.3.2. Impact on spatial stats 2 methods are available to compute group statistics: o method 1:spatialsegment metricsand~~multiparty configurations require multiple measurement~~statistics are preferably computed over time by eachpoints~~where a stream~~of~~singletons will~~interest; o method 2: Vectors metrics are intrinsecally instantaneous space metrics which mustbe~~collected. The amount of information requiring storage grows with both the number of~~reported using method2 whenever instantaneousmetrics~~and the number of~~information is needed. Pure passivemeasurement~~points, so the scale~~approach has no choice but to use this method because delay and losses may not be computed in each pointofinterest. 9. Manageability Considerations Usually IPPM WG documents defines each metric reporting within its definition. This document definesthe~~measurement architecture multiplies the number~~reportingof~~singleton results that must be collected and processed. It is possible that~~allthe~~architecture for results collection involves~~metrics introduced ina single~~aggregation point with connectivity~~sectionto~~all~~provide consistent information while avoiding repetitions.the~~measurement points. In this case,~~aim is to contribute tothe~~number of measurement points determines both storage capacity and packet transfer capacity~~workof the~~host acting as the aggregation point. However, both~~WG onthe~~storage~~reportingand~~transfer capacity can~~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 mustbe~~reduced if~~ordered. The complexity ofthe~~measurement~~reporting relies on the number ofpointsof interests. 9.1. Reporting spatial metric The reporting of spatial metrics shares a lot of aspects with RFC2679-80. New onesare~~capable~~common to all the definitions and are mostly related to the reportingof~~computing~~the~~summary statistics~~path and of methodology parametersthat~~describe each measurement interval.~~may bias raw results analysis.This~~is consistent with many operational monitoring architectures today, where even~~section presents these specific parameters and then lists exhaustivelythe~~individual singletons may not~~parameters that shallbe~~stored at each measurement point. In recognition~~reported. 9.1.1. Path End-to-end metrics can't determine the pathof the~~likely need~~measure despite IPPM RFCs recommend itto~~minimize form~~be reported (Section 3.8.4of~~the results for storage and communication, the Group~~[RFC2679]). Spatialmetrics~~above have been constructed to allow some computations on~~vectors provide this path. The report ofa~~per-Receiver basis. This means that each Receiver's statistics would normally have an equal weight with all other Receivers in~~spatial vector must includethe~~Group (regardless~~pointsofinterests involved:the~~number~~sub setof~~packets received). 7.1. Computation methods The scalability issue can be raised when there are thousands~~the hostsofthe path participating to the instantaneous measure. 9.1.2. Host order A spatial vector must order thepoints of interest~~in a group who are trying~~accordingto~~send back~~their order inthe~~measurement results~~path. It is highly suggestedtousethe~~reference point for further processing and analysis. The points of interest can send either~~TTL in IPv4,the~~whole measured sample~~Hop Limit in IPv6or~~only~~the~~calculated statistics.~~corresponding information in MPLS.The~~former one is a centralized statistic calculation method and the latter one is~~report ofa~~distributed statistic calculation method. The sample should~~spatial vector mustinclude~~all metrics parameters,~~the~~values and~~ordered list ofthe~~corresponding sequence numbers.~~hosts involved in the instantaneous measure. 9.1.3. Timestamping biasThe~~transmission~~locationof the~~whole sample can cost much more bandwidth than the transmission~~pointofinterest inside a node influencesthe~~statistics that should include all statistic parameters specified by policies~~timestamping skewandaccuracy. As an example, consider that some internal machinery delaysthe~~additional information about the whole sample, such as the size of~~timestamping up to 3 milliseconds thenthe~~sample,~~minimal uncertainty reported be 3 ms ifthe~~group address,~~internal delay is unknown atthe~~address~~timeof the~~point~~timestamping. The reportof~~interest,~~a spatial vector must includethe~~ID~~uncertaintyof the~~sample session,~~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 lossand~~so on. Apparently, the centralized calculation method can require much more bandwidth than the distributed calculation method when~~ipdv 9.2. Reporting One-to-group metric 9.3. Metric identification IANA assigns each metric defined bythe~~sample size is big. This is especially true when~~IPPM WG with a unique identifier as per [RFC4148] inthe~~measurement has huge number~~IANA-IPPM-METRICS-REGISTRY-MIB. To avoid misunderstanding and to address specific reporting constraints, section Section 5.4.3ofthis memo gives distinct names to passive metrics and Section 13 requests a distinct metric identifier for each metricsthe~~points~~memo defines. As it is crucial for compositionof~~interest. It can lead~~metricsto~~a scalability issue at~~knowthe~~reference point by over load~~methodology used (e.g. generation method, detection method...),the~~network resources. The distributed calculation method can save much more bandwidth and release~~report of a metric result used in composition of metrics MUST alway include its metric identifier. 9.4. Reporting data model This section presentsthe~~pressure~~elementsof the~~scalability issue at the reference point side. However, it can result in~~datamodel andthe~~lack~~usageoftheinformation~~because not all measured singletons are obtained~~reportedfor~~building up the group matrix. The~~real networkperformance~~over time can be hidden from the~~analysis.~~For example, the loss pattern can be missed by simply accepting~~It is out ofthe~~loss ratio as well as~~scope of this section to define howtheinformation is reported. The data model is build with pieces of information introduced and explained in one-waydelay~~pattern. This tradeoff between the bandwidth consuming~~definitions [RFC2679], in packet loss definitions [RFC2680]and~~the~~in IPDV definitions[RFC3393][RFC3432]. It includes not onlyinformation~~acquiring has to be taken into account when design~~given by "Reportingthe~~measurement campaign to optimize~~metric" sections but by sections "Methodology" and "Errors and Uncertainties" sections. Following arethe~~measurement results delivery.~~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~~possible solution could be to transit~~Type-P of test packets (Type-P); o Packet_length, a packet length in bits (L); o Src_host,the~~statistic parameters to~~IP address ofthe~~reference point first to obtain~~sender; o Dst_host,the~~general information~~IP addressof the~~group performance. If~~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~~detail~~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 ofresults~~are required,~~status; o dT: a delay; o Singleton_number: a number of singletons; o Observation_duration: An observation duration; o metric_identifier. Following isthe~~reference point~~information of each vector thatshould~~send the requests~~be availabletocompute samples: o Packet_type; o Packet_length; o Src_host,the~~points~~senderof~~interest, which could be particular ones or~~the~~whole group. This procedure can happen in~~packet; o Dst_host,the~~off peak time and can be well scheduled to avoid delivery of too many points~~receiverof~~interest at the same time. Compression techniques can also be used to minimize the bandwidth required by~~the~~transmission. This could be a measurement protocol to report~~packet, apply only for spatial vectors; o Hosts_serie: not ordered for one-to-group; o Src_time,the~~measurement results. It is out of~~sending time forthe~~scope of this memo. 7.2. Measurement To prevent any biais in~~measured packet; o dT,the~~result,~~end-to-end one-way delay forthe~~configuration of a one-to- many measure must take in consideration that implicitly more packets will to be routed than send~~measured packet, apply only for spatial vectors; o Delays_serie: apply only for delaysand~~selects a test~~ipdv vector, not ordered for one-to-group; o Losses_serie: apply only forpackets~~rate that will~~loss vector,not~~impact~~ordered for one-to-group; o Result_status_serie; o Observation_duration:the~~network performance. 7.3. effect~~difference between the timeof~~Time~~the last singletonand~~Space Aggregation Order on Group Stats This section presents~~the~~impact~~timeof the~~aggregation order on~~first singleton. o Following isthe~~scalability~~context information (measure, pointsof~~the reporting~~interests) that should be available to compute samples : * Loss threshold; * Systematic error: constant delay between wire timeandtimestamping; * Calibration error: maximal uncertainty; A spatial or a one-to-group sample is a collectionofsingletons givingtheperformance fromthe~~computation. It makes the hypothesis that receivers are managed remotly and not co-located. 2 methods are~~sender to a single point of interest. Following is the information that should beavailablefor each sampleto compute~~group~~statistics:~~Figure 8and (Figure 11) illustrate the method method choosen:~~o Packet_type; o Packet_length; o Src_host,the~~one-to-one statistic is computed per interval~~senderof~~time before~~the~~computation~~packet; o Dst_host, the receiverof the~~mean over~~packet; o Start_time,the~~group~~sending timeof~~receivers [method1]; Figure 15 presents~~the~~second one, metric is computed over space~~first packet; o Delays_serie: apply only for delaysand~~then over time [method2]. They differ~~ipdv samples; o Losses_serie: applyonly~~by~~for packets loss samples; o Result_status_serie; o Observation_duration:the~~order of~~difference betweenthe time~~and~~of the~~space aggregation. View as a matrix this order is neutral as it does not impact the result, but~~last singleton ofthe~~impact on a measurement deployement is critical. Recv 1 R1S1 R1S1 R1S1 ... R1Sk \ | 2 R2S1 R2S2 R2S3 ... R2Sk | | 3 R3S1 R3S2 R3S3 ... R3Sk >~~lastsample~~over space . | . | . | n RnS1 RnS2 RnS3 ... RnSk / S1M S2M S3M ... SnM Stats over space \------------- ------------/ \/ Group Stat over space~~and~~time Figure 15: Impact of space aggregation on Group Stat In both cases~~the~~volume~~timeof~~data to report is proportional to~~the~~number~~first singletonof~~probes. But there is a major difference between these 2 methods: method2: In space and time aggregation mode~~the~~volume of data to collect~~first sample. o Followingis~~proportionnal to~~the~~number of test packets received; Each received packet RiSi triggers out a block~~context information (measure, pointsof~~data~~interests)that~~must~~shouldbe~~reported~~availableto~~a common place for computing the stat over space; method1: In~~compute statistics : * Loss threshold; * Systematic error: constant delay between wiretime and~~space aggregation mode the volume of data to collect~~timestamping; * Calibration error: maximal uncertainty; Followingis~~proportionnal to~~the~~period~~informationof~~aggregation, so it does not depend on~~each statistic that should be reported: o Result; o Start_time; o Duration; o Result_status; o Singleton_number,the number of~~packet received; Method 2 property has severe drawbacks in terms~~singletons the statistic is computed on; 10. Open issues Do we define min, max, avgof~~security~~for each segment metrics ? having the maximum loss metric value could be interesting. Say, the segment between router Aand~~dimensionning: The increasing~~B always contributes loss metric valueof"1" means it could bethe~~rate~~potential problem segment. Uploading dTiof~~the test packets may result in~~each Hi consumea~~sort~~lotof~~DoS toward the computation points; The dimensioning~~bandwidth. Computing statistics (min, max and avg)of~~a measurement system is quite impossible to validate. The time agregation interval provides~~dTi locally in each Hi reducethe~~reporting side with a control of various collecting aspects such as~~bandwidthconsumption. 11. Security Considerations Spatialand~~computation and storage capacities. So this draft defines~~one-to-groupmetrics~~based~~are definedon~~method 1. Note: In some specific cases one may need sample of singletons over space. To adress this need it is suggested firstly to limit the number of test and~~the~~number~~topof~~test packets per seconds. Then reducing the size~~end-to-end metrics. Security considerations discussed in One-way delay metrics definitionsof~~the sample over time to one~~[RFC2679] , inpacket~~give sample of singleton over space.. 7.4. effect of Time~~loss metrics definitions of[RFC2680]and~~Space Aggregation Order on~~in IPDV metrics definitions of[RFC3393] and [RFC3432] apply to multimetrics. 11.1.Spatial~~Stats TBD 8. Open issues 9. Security Considerations Active measurement: (TODO: security considerations~~metrics Malicious generationof~~owd pl, jitter rfcs applies (editor notes: add references). 9.1. passive measurement The~~packets with spoofing addresses may corrupt the results without any possibility to detect the spoofing. Maliciousgeneration of packets which match systematically the hash functionused to detect the packetsmay lead to a DoS attack toward the~~collector.~~point of reference. 11.2. one-to-group metricThe~~generation~~reportingof~~packets with spoofing addresses~~measurement results from a huge number of probesmay~~corrupt~~overloadthe~~results without any possibility to detect~~networkthe~~spoofing. 9.2. one-to-group metric~~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 implicitly more packets will to be routed than send and selects a test packets rate accordingly. Collecting statistics from a huge number of probes may overload any combination of the networkwherethe measurement controller is attach to, measurement controller network interfaces and measurement controller computation capacities. one-to-group~~metrics: 10.~~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. 12.Acknowledgments Lei would like to acknowledgeProf.Zhili Sun from CCSR, University of Surrey, for his instruction and helpful comments on this work.~~11.~~13.IANA Considerations Metrics defined in this memo Metrics defined in this memo are designed to be registered in the IANA IPPM METRICS REGISTRY as described in initial version of the registry [RFC4148] : IANA is asked to register the following metrics in the IANA-IPPM- METRICS-REGISTRY-MIB : Spatial-One-way-Delay-Vector OBJECT-IDENTITY STATUS current DESCRIPTION "Type-P-Spatial-One-way-Delay-Vector" REFERENCE "Reference "RFCyyyy, section 4.1." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn~~subpath-One-way-Delay-Stream~~Spatial-Packet-Loss-VectorOBJECT-IDENTITY STATUS current DESCRIPTION~~"Type-P-subpath-One-way-Delay-Stream"~~"Type-P-Spatial-Packet-Loss-Vector"REFERENCE "Reference "RFCyyyy, section 4.2." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn~~Spatial-One-way-Packet-Loss-Vector~~Spatial-One-way-ipdv-VectorOBJECT-IDENTITY STATUS current DESCRIPTION~~"Type-P-Spatial-One-way-Packet-Loss-Vector"~~"Type-P-Spatial-One-way-ipdv-Vector"REFERENCE "Reference "RFCyyyy, section 4.3." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn~~Spatial-One-way-Jitter-Vector~~Spatial-Segment-One-way-Delay-Stream OBJECT-IDENTITY STATUS current DESCRIPTION "Type-P-Spatial-Segment-One-way-Delay-Stream" REFERENCE "Reference "RFCyyyy, section 5.1." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { 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-StreamOBJECT-IDENTITY STATUS current DESCRIPTION~~"Type-P-Spatial-One-way-Jitter-Vector"~~"Type-P-Passive-Segment-One-way-Delay-Stream"REFERENCE "Reference "RFCyyyy, section~~4.4."~~5.4.1."-- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nnPassive-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 metricsone-to-group-One-way-Delay-Vector OBJECT-IDENTITY STATUS current DESCRIPTION "Type-P-one-to-group-One-way-Delay-Vector" REFERENCE "Reference "RFCyyyy, section 5.1." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn one-to-group-One-way-Packet-Loss-Vector OBJECT-IDENTITY STATUS current DESCRIPTION "Type-P-one-to-group-One-way-Packet-Loss-Vector" REFERENCE "Reference "RFCyyyy, section 5.2." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn~~one-to-group-One-way-Jitter-Vector~~one-to-group-One-way-ipdv-VectorOBJECT-IDENTITY STATUS current DESCRIPTION~~"Type-P-one-to-group-One-way-Jitter-Vector"~~"Type-P-one-to-group-One-way-ipdv-Vector"REFERENCE "Reference "RFCyyyy, section 5.3." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn One-to-Group-Mean-Delay OBJECT-IDENTITY STATUS current DESCRIPTION "Type-P-One-to-Group-Mean-Delay" REFERENCE "Reference "RFCyyyy, section 6.3.3." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn One-to-Group-Range-Mean-Delay OBJECT-IDENTITY STATUS current DESCRIPTION "Type-P-One-to-Group-Range-Mean-Delay" REFERENCE "Reference "RFCyyyy, section 6.3.4." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn One-to-Group-Max-Mean-Delay OBJECT-IDENTITY STATUS current DESCRIPTION "Type-P-One-to-Group-Max-Mean-Delay" REFERENCE "Reference "RFCyyyy, section 6.3.5." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn One-to-Group-Loss-Ratio OBJECT-IDENTITY STATUS current DESCRIPTION "Type-P-One-to-Group-Loss-Ratio" REFERENCE "Reference "RFCyyyy, section 6.4.1." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn -- One-to-Group-Loss-Ratio-Range OBJECT-IDENTITY STATUS current DESCRIPTION "Type-P-One-to-Group-Loss-Ratio-Range" REFERENCE "Reference "RFCyyyy, section 6.4.2." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn --~~12.~~14.References~~12.1.~~14.1.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.~~12.2.~~14.2.Informative References [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. [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. [RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M. Zekauskas, "A One-way Active Measurement Protocol (OWAMP)", RFC 4656, September 2006. [RFC4737] Morton, A., Ciavattone, L., Ramachandran, G., Shalunov, S., and J. Perser, "Packet Reordering Metrics", RFC 4737, November 2006. 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-ftgroup.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 Full Copyright Statement Copyright (C) The IETF Trust (2007). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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