--- 1/draft-ietf-ippm-multimetrics-05.txt 2008-02-15 15:12:19.000000000 +0100 +++ 2/draft-ietf-ippm-multimetrics-06.txt 2008-02-15 15:12:19.000000000 +0100 @@ -1,21 +1,21 @@ Network Working Group E. Stephan Internet-Draft France Telecom Intended status: Informational L. Liang -Expires: May 21, 2008 University of Surrey +Expires: August 17, 2008 University of Surrey A. Morton AT&T Labs - November 18, 2007 + February 14, 2008 IP Performance Metrics (IPPM) for spatial and multicast - draft-ietf-ippm-multimetrics-05 + draft-ietf-ippm-multimetrics-06 Status 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 @@ -26,95 +26,97 @@ 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 May 21, 2008. + This Internet-Draft will expire on August 17, 2008. Copyright Notice - Copyright (C) The IETF Trust (2007). + Copyright (C) The IETF Trust (2008). Abstract The IETF IP Performance Metrics (IPPM) working group has standardized metrics for measuring end-to-end performance between two points. This memo defines two new categories of metrics that extend the coverage to multiple measurement points. It defines spatial metrics for measuring the performance of segments of a source to destination path, and metrics for measuring the performance between a source and many destinations in multiparty communications (e.g., a multicast tree). Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1. Path Digest Hosts . . . . . . . . . . . . . . . . . . . . 6 2.2. Multiparty metric . . . . . . . . . . . . . . . . . . . . 6 2.3. Spatial metric . . . . . . . . . . . . . . . . . . . . . . 6 2.4. One-to-group metric . . . . . . . . . . . . . . . . . . . 6 - 2.5. Points of interest . . . . . . . . . . . . . . . . . . . . 6 + 2.5. Points of interest . . . . . . . . . . . . . . . . . . . . 7 2.6. Reference point . . . . . . . . . . . . . . . . . . . . . 8 2.7. Vector . . . . . . . . . . . . . . . . . . . . . . . . . . 8 2.8. Matrix . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3. Motivations . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.1. Motivations for spatial metrics . . . . . . . . . . . . . 9 3.2. Motivations for One-to-group metrics . . . . . . . . . . . 10 3.3. Discussion on Group-to-one and Group-to-group metrics . . 11 4. Spatial vectors metrics definitions . . . . . . . . . . . . . 11 4.1. A Definition for Spatial One-way Delay Vector . . . . . . 12 4.2. A Definition for Spatial One-way Packet Loss Vector . . . 13 4.3. A Definition for Spatial One-way Ipdv Vector . . . . . . . 15 - 4.4. Spatial Methodology . . . . . . . . . . . . . . . . . . . 17 - 5. Spatial Segments metrics definitions . . . . . . . . . . . . . 19 + 4.4. Spatial Methodology . . . . . . . . . . . . . . . . . . . 16 + 5. Spatial Segments metrics definitions . . . . . . . . . . . . . 18 5.1. A Definition of a sample of One-way Delay of a segment - of the path . . . . . . . . . . . . . . . . . . . . . . . 19 + of the path . . . . . . . . . . . . . . . . . . . . . . . 18 5.2. A Definition of a sample of Packet Loss of a segment of the path . . . . . . . . . . . . . . . . . . . . . . . 20 - 5.3. A Definition of a sample of One-way Ipdv of a segment - of the path . . . . . . . . . . . . . . . . . . . . . . . 23 - 6. One-to-group metrics definitions . . . . . . . . . . . . . . . 23 - 6.1. A Definition for one-to-group One-way Delay . . . . . . . 23 - 6.2. A Definition for one-to-group One-way Packet Loss . . . . 24 - 6.3. A Definition for one-to-group One-way Ipdv . . . . . . . . 25 - 7. One-to-Group Sample Statistics . . . . . . . . . . . . . . . . 26 - 7.1. Discussion on the Impact of packet loss on statistics . . 29 - 7.2. General Metric Parameters . . . . . . . . . . . . . . . . 30 - 7.3. One-to-Group one-way Delay Statistics . . . . . . . . . . 31 - 7.4. One-to-Group one-way Loss Statistics . . . . . . . . . . . 33 - 7.5. One-to-Group one-way Delay Variation Statistics . . . . . 35 - 8. Measurement Methods: Scaleability and Reporting . . . . . . . 35 - 8.1. Computation methods . . . . . . . . . . . . . . . . . . . 36 - 8.2. Measurement . . . . . . . . . . . . . . . . . . . . . . . 37 - 8.3. Effect of Time and Space Aggregation Order on Stats . . . 37 - 9. Manageability Considerations . . . . . . . . . . . . . . . . . 39 - 9.1. Reporting spatial metric . . . . . . . . . . . . . . . . . 39 - 9.2. Reporting One-to-group metric . . . . . . . . . . . . . . 40 - 9.3. Metric identification . . . . . . . . . . . . . . . . . . 41 - 9.4. Reporting data model . . . . . . . . . . . . . . . . . . . 41 - 10. Open issues . . . . . . . . . . . . . . . . . . . . . . . . . 44 - 11. Security Considerations . . . . . . . . . . . . . . . . . . . 45 - 11.1. Spatial metrics . . . . . . . . . . . . . . . . . . . . . 45 - 11.2. one-to-group metric . . . . . . . . . . . . . . . . . . . 45 - 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 45 - 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 46 - 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 51 - 14.1. Normative References . . . . . . . . . . . . . . . . . . . 51 - 14.2. Informative References . . . . . . . . . . . . . . . . . . 51 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 52 - Intellectual Property and Copyright Statements . . . . . . . . . . 54 + 5.3. A Definition of a sample of ipdv of a segment using + the previous packet selection function . . . . . . . . . . 22 + 5.4. A Definition of a sample of ipdv of a segment using + the minimum delay selection function . . . . . . . . . . . 24 + 6. One-to-group metrics definitions . . . . . . . . . . . . . . . 25 + 6.1. A Definition for One-to-group One-way Delay . . . . . . . 26 + 6.2. A Definition for One-to-group One-way Packet Loss . . . . 26 + 6.3. A Definition for One-to-group One-way Ipdv . . . . . . . . 27 + 7. One-to-Group Sample Statistics . . . . . . . . . . . . . . . . 28 + 7.1. Discussion on the Impact of packet loss on statistics . . 31 + 7.2. General Metric Parameters . . . . . . . . . . . . . . . . 32 + 7.3. One-to-Group one-way Delay Statistics . . . . . . . . . . 33 + 7.4. One-to-Group one-way Loss Statistics . . . . . . . . . . . 36 + 7.5. One-to-Group one-way Delay Variation Statistics . . . . . 38 + 8. Measurement Methods: Scalability and Reporting . . . . . . . . 38 + 8.1. Computation methods . . . . . . . . . . . . . . . . . . . 39 + 8.2. Measurement . . . . . . . . . . . . . . . . . . . . . . . 40 + 8.3. Effect of Time and Space Aggregation Order on Stats . . . 40 + 9. Manageability Considerations . . . . . . . . . . . . . . . . . 42 + 9.1. Reporting spatial metric . . . . . . . . . . . . . . . . . 42 + 9.2. Reporting One-to-group metric . . . . . . . . . . . . . . 43 + 9.3. Metric identification . . . . . . . . . . . . . . . . . . 44 + 9.4. Reporting data model . . . . . . . . . . . . . . . . . . . 44 + 10. Open issues . . . . . . . . . . . . . . . . . . . . . . . . . 47 + 11. Security Considerations . . . . . . . . . . . . . . . . . . . 47 + 11.1. Spatial metrics . . . . . . . . . . . . . . . . . . . . . 48 + 11.2. one-to-group metric . . . . . . . . . . . . . . . . . . . 48 + 12. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 48 + 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 48 + 14. References . . . . . . . . . . . . . . . . . . . . . . . . . . 54 + 14.1. Normative References . . . . . . . . . . . . . . . . . . . 54 + 14.2. Informative References . . . . . . . . . . . . . . . . . . 55 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 55 + Intellectual Property and Copyright Statements . . . . . . . . . . 57 1. Introduction The IP Performance Metrics (IPPM) WG has defined a framework for metric definitions and end-to-end, or source to destination measurements: o A general framework for defining performance metrics, described in the Framework for IP Performance Metrics [RFC2330]; @@ -162,32 +164,37 @@ be introduced to divide an end-to-end Type-P-One-way-Packet-Loss [RFC2680] in a spatial sequence of packet loss metrics. o Using the Type-P-Spatial-One-way-Delay-Vector metric, a 'vector', called Type-P-Spatial-One-way-ipdv-Vector, will be introduced to divide an end-to-end Type-P-One-way-ipdv in a spatial sequence of ipdv metrics. o Using the Type-P-Spatial-One-way-Delay-Vector metric, a 'sample', called Type-P-Segment-One-way-Delay-Stream, will be introduced to - collect a nested set of one-way delay metrics between the source, - intermediate points of interest, and the destination; + collect one-way delay metrics over time between two points of + interest of the path; o Using the Type-P-Spatial-Packet-Loss-Vector metric, a 'sample', called Type-P-Segment-Packet-Loss-Stream, will be introduced to - collect a nested set of packet loss metrics between the source, - intermediate points of interest, and the destination; + collect packet loss metrics over time between two points of + interest of the path; - o Using the Type-P-Spatial-ipdv-Vector metric, a 'sample', called - Type-P-Segment-ipdv-Stream, will be introduced to collect a nested - set of ipdv metrics between the source, intermediate points of - interest, and the destination; + o Using the Type-P-Spatial-One-way-Delay-Vector metric, a 'sample', + called Type-P-Segment-ipdv-prev-Stream, will be introduced to + compute ipdv metrics over time between two points of interest of + the path using the previous packet selection function; + + o Using the Type-P-Spatial-One-way-Delay-Vector metric, a 'sample', + called Type-P-Segment-ipdv-min-Stream, will be introduced to + compute ipdv metrics over time between two points of interest of + the path using the shortest delay selection function; Note that all these metrics are based on observations of packets dedicated to testing, a process which is called Active measurement. Purely passive spatial measurement (for example, a spatial metric based on the observation of user traffic) is beyond the scope of this document and the current IPPM charter. Next, this memo defines one-to-group metrics. o Using one test packet sent from one sender to a group of @@ -230,41 +237,41 @@ where ha is the source and < hb, hc, ..., hn > are the destinations, then measurements may be conducted between < ha, hb>, < ha, hc>, ..., . 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 (measurement - collection points) involved is neither the source nor the destination + collection points) involved is neither the source nor a destination of the measured packet. 2.4. One-to-group metric A metric is said to be one-to-group if the measured packet is sent by one source and (potentially) received by several destinations. Thus, the topology of the communication group can be viewed as a centre- distributed or server-client topology with the source as the centre/ server in the topology. 2.5. Points of interest Points of interest are the hosts* (as per RFC2330 definition, that includes routing nodes) that are measurement collection points, a sub-set of the set of hosts involved in the delivery of the packets (in addition to the source itself). Note that the points of interest are a possibly arbitrary sub-set of all the hosts involved in the path. - Points of interest of One-to-group metrics are the intended + Points of interest of one-to-group metrics are the intended destination hosts for packets from the source (in addition to the source itself). Src Recv `. ,-. `. ,' `...... 1 `. ; : `. ; : ; :... 2 | | @@ -309,42 +316,42 @@ calculations will be carried out. A centre/server in the multimetrics measurement that is controlled by a network operator is a good example of a reference point, where measurement data can be collected for further processing. However, the actual measurements have to be carried out at all points of interest. 2.7. Vector 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 times. For instance, if One-way delay + of a network at different times. 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 sending time. Given the vector V as an example, the element dT1 is distinct from all others as the singleton at receiver 1 in response to a packet sent from the source at time T1. The complete Vector gives information over the dimension of space. 2.8. Matrix Several vectors form a Matrix, which contains results observed in a - sampling interval at different places in 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 in simple point-to- - point measurement. + sampling interval at different places in a network at different + times. 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 in simple + point-to-point measurement. The relation among Singleton, Vector and Matrix can be shown in the following Figure 3. Point of Singleton interest / Samples ,----. ^ / / R1.....| / R1dT1 R1dT2 R1dT3 ... R3dTk \ / \ | | | ; R2........| | R2dT1 R2dT2 R2dT3 ... R3dTk | @@ -380,21 +387,21 @@ o Traffic engineering and troubleshooting applications benefit from spatial views of one-way delay and ipdv consumption, and identification of the location of the lost of packets. o Monitoring the performance of a multicast tree composed of MPLS point-to-multipoint and inter-domain communication require spatial decomposition of the one-way delay, ipdv, and packet loss. o Composition of metrics [I-D.ietf-ippm-spatial-composition] is needed to help measurement systems reach large scale coverage. - Spatial measure typically give the individual performance of an + Spatial measures typically give the individual performance of an intra domain segment and provide an elementary piece of information needed to estimate interdomain performance based on composition of metrics. 3.2. Motivations for One-to-group metrics While the node-to-node based spatial measures can provide very useful data in the view of each connection, we also need measures to present the performance of a multiparty communication topology. A simple one-way metric cannot completely describe the multiparty situation. @@ -413,21 +420,21 @@ 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 performance requirements for - multiparty communications. + multiparty communications and overlay multicast. To understand the packet transfer performance between one source and any one receiver in the multiparty communication group, we need to collect instantaneous end-to-end metrics, or singletons. It will give a very detailed insight into each branch of the multicast tree in terms of end-to-end absolute performance. This detail can provide clear and helpful information for engineers to identify the sub-path with problems in a complex multiparty routing tree. The one-to-group metrics described in this memo introduce the @@ -435,21 +442,21 @@ the performance delivered to a group of users who are receiving packets 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. If applied to one-to-one communications, the one-to-group metrics 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 + 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, it is difficult to define @@ -472,257 +479,257 @@ Spatial vectors metrics are based on the decomposition of standard end-to-end metrics defined by the IPPM WG in [RFC2679], [RFC2680], [RFC3393] and [RFC3432]. Definitions are coupled with the corresponding end-to-end metrics. Methodology specificities are common to all the vectors defined and are consequently discussed in a common section. 4.1. A Definition for Spatial One-way Delay Vector - 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. + This section is coupled with the definition of Type-P-One-way-Delay + of the section 3 of [RFC2679]. When a parameter of this definitionis + 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 o Src*, the IP address of the sender. o Dst*, the IP address of the receiver. - o i, An integer if the list <1,2,...,n> which ordered the hosts in - the path. + o i, An integer in the ordered list <1,2,...,n> of hosts in the + path. o Hi, A host* of the path digest. o T*, a time, the sending (or initial observation) time for a measured packet. - o dT* a delay, the one-way delay for a measured packet. + o dT*, a delay, the one-way delay for a measured packet. o a list of delay. o P*, the specification of the packet type. o , hosts path digest. 4.1.3. Metric Units - A sequence of times. + The value of Type-P-Spatial-One-way-Delay-Vector is 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 . Given the sequence of values 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 as the sequence of values . 4.1.5. Discussion Following are specific issues which may occur: - o the delay looks to decrease: dTi > DTi+1. This seem typically du - to some clock synchronisation issue. This point is discussed in - the section 3.7.1. "Errors or uncertainties related to Clocks" of - of [RFC2679]. 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 delay looks to decrease: dTi > DTi+1. This may occur despite + it does not make sense per definition: - 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'; + * This is frequently due to some clock synchronization issue. + This point is discussed in the section 3.7.1. "Errors or + uncertainties related to Clocks" of [RFC2679]. Consequently, + times of a measure at different hosts do not guaranty the + ordering of the hosts on the path of a measure. + + * During some change of routes the order of 2 hosts may change on + the main path; + + * The location of the point of interest in the device influences + the result. If the packet is not observed directly on the + input interface the delay includes buffering time and + consequently an uncertainty due to the difference between 'wire + time' and 'host time' 4.2. A Definition for Spatial One-way Packet Loss Vector This section is coupled with the definition of Type-P-One-way-Packet- Loss. Then when a parameter from the section 2 of [RFC2680] is first used in this section, it will be tagged with a trailing asterisk. Sections 2.5 to 2.8 of [RFC2680] give requirements and applicability - statements for end-to-end one-way-Packet-Loss measurements. They are + statements for end-to-end one-way packet loss measurements. They are applicable to each point of interest Hi involved in the measure. Spatial packet loss measurement SHOULD be respectful of them, especially those related to methodology, clock, uncertainties and reporting. Following we define the spatial metric, then we adapt some of the points above and introduce points specific to spatial measurement. 4.2.1. Metric Name Type-P-Spatial-One-way-Packet-Loss-Vector 4.2.2. Metric Parameters - + Src*, the IP address of the sender. + o Src*, the IP address of the sender. - + Dst*, the IP address of the receiver. + o Dst*, the IP address of the receiver. - + i, An integer which ordered the hosts in the path. + o i, an integer which ordered the hosts in the path. - + Hi, exchange points of the path digest. + o Hi, points of interests of the path digest. - + T*, a time, the sending (or initial observation) time for - a measured packet. + o T*, a time, the sending time for a measured packet. - + dT1,..., dTn, dT, a list of delay. + o , a list of delay. - + P*, the specification of the packet type. + o P*, the specification of the packet type. - + , hosts path digest. + o , hosts path digest. - + B1, B2, ..., Bi, ..., Bn, a list of Boolean values. + o , a list of Boolean values. 4.2.3. Metric Units - A sequence of Boolean values. + The value of Type-P-Spatial-One-way-Packet-Loss-Vector is a sequence + of Boolean values. 4.2.4. Definition Given a Type-P packet sent by the sender Src at time T to the receiver Dst in the path . Given the sequence of - times the packet passes , - - Type-P-One-way-Packet-Lost-Vector metric is defined as the sequence - of values such that for each Hi of the path, a - value of Bi of 0 means that dTi is a finite value, and a value of 1 - means that dTi is undefined. + times the packet passes in , + we define Type-P-One-way-Packet-Lost-Vector metric as the sequence of + values such that for each Hi of the path, a value + of 0 for Li means that dTi is a finite value, and a value of 1 means + that dTi is undefined. 4.2.5. Discussion Following are specific issues which may occur: - o the result includes the sequence 1,0. This case means that the - packet was seen by a host but not by it successor on the path; + o The result includes the sequence 1,0. This may occur under + specific situations: - The location of the point of interest in the device influences the - result: + * During some change of routes a packet may be seen by a host but + not by it successor on the main path; - o Even if the packet is received by a host, it may be not observed - by the point of interest located after a buffer; + * A packet may not be observed in a host due to some buffer or + CPU overflow in the point of interest; 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. + In the following we adapt some of them and introduce points specific + 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. + o Src*, the IP address of the sender. - + Dst*, the IP address of the receiver. + o Dst*, the IP address of the receiver. - + i, An integer which ordered the hosts in the path. + o i, An integer in the ordered list <1,2,...,n> of hosts in the + path. - + Hi, exchange points of the path digest. + o Hi, A host* of the path digest. - + T1*, the time the first packet was sent. + o T1*, a time, the sending time for a first measured packet. - + T2*, the time the second packet was sent. + o T2*, a time, the sending time for a second measured packet. - + P, the specification of the packet type. + o dT*, a delay, the one-way delay for a measured packet. - + P1, the first packet sent at time T1. + o P*, the specification of the packets type. - + P2, the second packet sent at time T2. + o P1, the first packet sent at time T1. - + , host path digest. + o P2, the second packet sent at time T2. - + , - the Type-P-Spatial-One-way-Delay-Vector for packet sent at - time T1; + o , hosts path digest. - + , - the Type-P-Spatial-One-way-Delay-Vector for packet sent at - time T2; + o , the Type-P-Spatial-One-way- + Delay-Vector for packet sent at time T1. - + L*, a packet length in bits. The packets of a Type P - packet stream from which the - Type-P-Spatial-One-way-Delay-Vector metric is taken MUST - all be of the same length. + o , the Type-P-Spatial-One-way- + Delay-Vector for packet sent at time T2. + + o L*, a packet length in bits. The packets of a Type P packet + stream from which the Type-P-Spatial-One-way-Delay-Vector metric + is taken MUST all be of the same length. 4.3.3. Metric Units - A sequence of times. + The value of Type-P-Spatial-One-way-ipdv-Vector is a sequence of + times. 4.3.4. Definition - Given the Type-P packet having the size L and sent by the sender Src - at wire-time (first bit) T1 to the receiver Dst in the path . - - Given the Type-P packet having the size L and sent by the sender Src - at wire-time (first bit) T2 to the receiver Dst in the same path. - - Given the Type-P-Spatial-One-way-Delay-Vector of the packet P1. + Given P1 the Type-P packet sent by the sender Src at wire-time (first + bit) T1 to the receiver Dst and + its Type-P-Spatial-One-way-Delay-Vector over the path . - Given the Type-P-Spatial-One-way-Delay-Vector of the packet P2. + Given P2 the Type-P packet sent by the sender Src at wire-time (first + bit) T2 to the receiver Dst and + its Type-P-Spatial-One-way-Delay-Vector over the same path. Type-P-Spatial-One-way-ipdv-Vector metric is defined as the sequence - of values - Such that for each Hi of the path , dT2.i-dT1.i is - either a real number if the packets P1 and P2 passes Hi at wire-time - (last bit) dT1.i, respectively dT2.i, or undefined if at least one of - them never passes Hi. T2-T1 is the inter-packet emission interval - and dT2-dT1 is ddT* the Type-P-One-way-ipdv at T1,T2*. + of values such that for each Hi of the path , dT2.i-dT1.i + is either a real number if the packets P1 and P2 passe Hi at wire- + time (last bit) dT1.i, respectively dT2.i, or undefined if at least + one of them never passes Hi. T2-T1 is the inter-packet emission + interval and dT2-dT1 is ddT* the Type-P-One-way-ipdv at T1,T2*. 4.4. Spatial Methodology Methodology, reporting and uncertainties points specified in section - 3 of [RFC2679][RFC2679] applies to each point of interest Hi - measuring a element of a spatial delay vector. + 3 of [RFC2679] applies to each point of interest Hi measuring a + element of a spatial delay vector. Methodology, reporting and uncertainties points specified in section - 2 of [RFC2680][RFC2680] applies to each point of interest Hi - measuring a element of a spatial packet loss vector. + 2 of [RFC2680] applies to each point of interest Hi measuring a + element of a spatial packet loss vector. Sections 3.5 to 3.7 of [RFC3393] give requirements and applicability statements for end-to-end One-way ipdv measurements. They are applicable to each point of interest Hi involved in the measure. Spatial One-way ipdv measurement SHOULD be respectful of methodology, clock, uncertainties and reporting aspects given in this section. Generally, for a given Type-P of length L, in a given Hi, the - methodology for spatial vector metrics would proceed as follows: + methodology for spatial vector metrics may proceed as follows: o At each Hi, points of interest prepare to capture the packet sent a time T, take a timestamp Ti', determine the internal delay correction dTi' (See section 3.7.1. "Errors or uncertainties related to Clocks" of [RFC2679]), o Each Hi extracts the path ordering information from the packet (e.g. time-to-live); o Each Hi compute the wiretime from Src to Hi: Ti = Ti' - dTi'. @@ -723,418 +730,566 @@ related to Clocks" of [RFC2679]), o Each Hi extracts the path ordering information from the packet (e.g. time-to-live); o Each Hi compute the wiretime from Src to Hi: Ti = Ti' - dTi'. This arrival time is undefined (infinite) if the packet is not detected after the 'loss threshold' duration; o Each Hi extracts the timestamp T from the packet; + o Each Hi computes the one-way-delay from Src to Hi: dTi = Ti - T; - o The reference point gathers the result and time-to-live of each Hi - and order them according to the path to build the Type-P-Spatial- - One-way-Delay-Vector metric over the path - . + o The reference point gathers the result of each Hi and order them + according to the path ordering information received to build the + type-P spatial one-way vector (e.g. Type-P-Spatial-One-way-Delay- + Vector metric ) over the path at time T. 4.4.1. Loss threshold Loss threshold is the centrality of any methodology because it determines the presence the packet in the measurement process of the point of interest and consequently determines any ground truth metric result. It determines the presence of an effective delay, and bias the measure of ipdv, of packet loss and of the statistics. This is consistent for end-to-end but impacts spatial measure: - depending on the consistency of the Loss threshold among the points + depending on the consistency of the loss threshold among the points of interest, a packet may be considered loss a one host but present in another one, or may be observed by the last host (last hop) of the path but considered lost by Dst. The analysis of such results is not - deterministic: has the path change? Does the packet arrive at + deterministic: Has the path change? Does the packet arrive at destination or was it lost during the last mile? The same applies, of course, for one-way-delay measures: a delay measured may be infinite at one host but a real value in another one, or may be measured as a real value by the last host of the path but observed as - infinite by Dst. The Loss threshold should be set up with the same - value in each host of the path and in the destination. The Loss + infinite by Dst. The loss threshold should be set up with the same + value in each host of the path and in the destination. The loss threshold must be systematically reported to permit careful introspection and to avoid the introduction of any contradiction in the statistic computation process. 4.4.2. Host Path Digest - The methodology given above adds the order of the points of interest - over the path to [RFC2679] one's. - - A perfect Host Path Digest (hum! of cource from the measurement point - of view only, that is, corresponding to the real path the test packet - experimented) may include several times several hosts: + The methodology given above relies on the order of the points of + interest over the path to [RFC2679] one's. - o coresponds to a loop in the path; + A test packets may cross several times the same host resulting in the + repetition of one or several hosts in the Path Digest. - o coresponds to a loop in the path which - may occurs during rerouting phases; + As an example. This occurs typically during rerouting phases which + introduce temporary micro loops. During such an event the host path + digest for a packet crossing Ha and Hb may include the pattern meaning that Ha ended the computation of the new path + before Hb and that the initial path wath from Ha to Hb and that the + new path is from Hb to Ha. - These cases MUST be identified before statistics computation to avoid - corrupted results' production. This applies especially to the - measure of segments which are build from results of a measure of a - vector metric. + Consequently, duplication of hosts in the Path Digest of a vectors + MUST be identified before statistics computation to avoid corrupted + results' production. 5. Spatial Segments metrics definitions - This section defines samples to measure a sequence of delays, a - sequence of lost and a sequence of ipdv between 2 hosts of the path, - a segment. Singletons are taken from segments of vectors defined - above. + This section defines samples to measure the performance of a segment + of a path over time. Definitions rely on matrix of the spatial + vector metrics defined above. + + Firstly it defines a sample of one-way delay, Type-P-Segment-One-way- + Delay-Stream, and a sample of packet loss, Type-P-segment-Packet- + loss-Stream. + + Then it defines 2 different samples of ipdv. The first metric, Type- + P-Segment-One-way-ipdv-prev-Stream, uses the previous packet as the + selection function. The second metric, Type-P-Segment-One-way-ipdv- + min-Stream, uses the minimum delay as the selection. 5.1. A Definition of a sample of One-way Delay of a segment of the path - This metric defines a sample of One-way delays between a pair of - hosts of a path. + This metric defines a sample of One-way delays over time between a + pair of hosts of a path. + + As its semantic is very close to the metric Type-P-Packet-loss-Stream + defined in section 4 of [RFC2679], sections 4.5 to 4.8 of [RFC2679] + are part of the current definition. 5.1.1. Metric Name Type-P-Segment-One-way-Delay-Stream 5.1.2. Metric Parameters - + Src*, the IP address of the sender. + o Src*, the IP address of the sender. - + Dst*, the IP address of the receiver. + o Dst*, the IP address of the receiver. - + P*, the specification of the packet type; + o P*, the specification of the packet type. - + i, An integer which orders exchange points in the path. + o i, an integer in the ordered list <1,2,...,n> of hosts in the + path. - + k, An integer which orders the packets sent. + o k, an integer which orders the packets sent. - + Hi, a host of the path digest; + o a and b, 2 integers where b > a. - + , host path digest. + o Hi, a host* of the path digest. - + Ha, a host of the path digest different from Dst and Hb; + o , hosts path digest. - + Hb, a host of the path digest different from Src and Ha. - Hb order in the path must greater that Ha; + o , a list of times. - + , a list of time ordered by k; +5.1.3. Metric Units - + dT1,..., dTn a list of delay; + The value of a Type-P-Segment-One-way-Delay-Stream is a pair of -5.1.3. Metric Units + list of times ; - A sequence of delay + sequence of delays. 5.1.4. Definition - Given 2 hosts Ha and Hb of the path , given - a flow of packets of Type-P sent from Src to Dst at the times T1, - T2... Tn. At each of these times, we obtain a Type-P-Spatial-One- - way-Delay-Vector . 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.a is the delay - between Src and Ha. dTk.b is the delay between Src and Hb. 'dTk.b - - dTk.a' is the one-way delay experienced by the packet sent by Src at - the time Tk when going from Ha to Hb. + Given 2 hosts, Ha and Hb, of the path , given the matrix of Type-P-Spatial-One-way-Delay-Vector for the + packets sent from Src to Dst at times : -5.1.5. Discussion + ; - Following are specific issues which may occur: + ; - o When a is Src is the measure of the first hop. + ... - o When b is Dst is the measure of the last hop. + . + + We define the sample Type-P-segment-One-way-Delay-Stream as the + sequence such that for + each time Tk, 'dTk.ab' is either the real number 'dTk.b - dTk.a' if + the packet send a time Tk passes Ha and Hb or undefined if this + packet never passes Ha or (inclusive) never passes Hb. + +5.1.5. Discussion + + Following are specific issues which may occur: o the delay looks to decrease: dTi > DTi+1: - * This is typically du to clock synchronisation issue. this point - is discussed in the section 3.7.1. "Errors or uncertainties - related to Clocks" of of [RFC2679]; + * This is typically due to clock synchronization issue. this + point is discussed in the section 3.7.1. "Errors or + uncertainties related to Clocks" of of [RFC2679]; * This may occurs too when the clock resolution of one probe is bigger than the minimum delay of a path. As an example this happen when measuring the delay of a path which is 500 km long with one probe synchronized using NTP having a clock resolution of 8ms. - o The location of the point of interest in the device influences the - result. 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'; + The metric can not be performed on < T1 , T2, ..., Tm-1, Tm> in the + following cases: - o dTk.b may be observed and not dTk.a. + o Ha or Hb disappears from the path due to some change of routes; + + o The order of Ha and Hb changes in the path; 5.2. A Definition of a sample of Packet Loss of a segment of the path - This metric defines a sample of Packet lost between a pair of hosts - of a path. + This metric defines a sample of packet lost over time between a pair + of hosts of a path. As its semantic is very close to the metric + Type-P-Packet-loss-Stream defined in section 3 of [RFC2680], sections + 3.5 to 3.8 of [RFC2680] are part of the current definition. 5.2.1. Metric Name Type-P-segment-Packet-loss-Stream 5.2.2. Metric Parameters - + Src*, the IP address of the sender. - - + Dst*, the IP address of the receiver. + o Src*, the IP address of the sender. - + P*, the specification of the packet type. + o Dst*, the IP address of the receiver. - + k, An integer which orders the packets sent. + o P*, the specification of the packet type. - + n, An integer which orders the hosts on the path. + o k, an integer which orders the packets sent. - + , hosts path digest. + o n, an integer which orders the hosts on the path. - + Ha, a host of the path digest different from Dst and Hb; + o a and b, 2 integers where b > a. - + Hb, a host of the path digest different from Src and Ha. - Hb order in the path must greater that Ha; + o , hosts path digest. - + Hi, exchange points of the path digest. + o Hi, exchange points of the path digest. - + a list of bits. + o , a list of times. - + a list of integers. + o a list of boolean values. 5.2.3. Metric Units - A sequence of integers + The value of a Type-P-segment-Packet-loss-Stream is a pair of + + The list of times ; + + a sequence of booleans. 5.2.4. Definition - Given 2 hosts Ha and Hb of the path , given - a flow of packets of Type-P sent from Src to Dst at the times T1, - T2... Tn. At each of these times, we obtain a Type-P-Spatial- - Packet-Lost-Vector . We define the value of - the sample Type-P-segment-Packet-Lost-Stream between Ha and Hb as the - sequence made up of the integer such that for each - Tk: + Given 2 hosts, Ha and Hb, of the path , given the matrix of Type-P-Spatial-Packet-loss-Vector for the + packets sent from Src to Dst at times : - o a value of Lk of 0 means that Bk.a has a value of 0 (observed) and - that Bk.b have a value of 0 (observed); - o a value of Lk of 1 means that Bk.a has a value of 0 (observed) and - that Bk.b have a value of 1 (not observed); + , - o a value of Lk of 2 means that Bk.a has a value of 1 (not observed) - and that Bk.b have a value of 0 (observed); + , - o a value of Lk of 3 means that Bk.a has a value of 1 (not observed) - and that Bk.b have a value of 1 (not observed). + ..., -5.2.5. Discussion + . - The semantic of a Type-P-segment-Packet-loss-Stream is similar to the - one of Type-P-Packet-loss-Stream: + We define the value of the sample Type-P-segment-Packet-Lost-Stream + from Ha to Hb as the sequence of booleans such that for each Tk: - o a value of 0 means that the packet was observed by Ha (similar to - 'send by Src') and not observed by Hb ( similar to 'not received - by Dst'); + o A value of Lk of 0 means that Ha and Hb observed the packet sent + at time Tk (Lk.a and Lk.b have a value of 0); - 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'). + o A value of Lk of 1 means that Ha observed the packet sent at time + Tk (Lk.a has a value of 0) and that Hb did not observed the packet + sent at time Tk (Lk.b have a value of 1); + o The value of Lk is undefined when Neither Ha or Hb observe the + packet; - This definition of Type-P-segment-Packet-loss-Stream is similar to - the Type-P-Packet-loss-Stream defined in [RFC2680] excepted that in a - Type-P-segment-Packet-loss-Stream the rules of the point of interests - Ha and Hb are symetrical: The asumption that a set of packets are - going from Ha to Hb does not apply to Type-P-segment-Packet-loss- - Stream because as the host path digest is dynamic each packet has its - own host path digest. +5.2.5. Discussion - Making the asumption that the host path digest of a Type-P-spatial- - Packet-loss-vector does not change and that the set of (Hk, Hk+1) - tuples is mostly stable over time lead to unusable results and to the - introduction of mistakes in the metrics aggregation processes. The - right approach consists in carefully scrutening the path ordering - information to build sample with elements of vectors sharing the same - properties in term of Ha and Hb and 'Ha to Hb'. So a measure of - Type-P-spatial-Packet-loss-vector differs from a Type-P-Packet-loss - one in that it produces different samples of packet loss over time. + Unlike Type-P-Packet-loss-Stream, Type-P-Segment-Packet-loss-Stream + relies on the stability of the host path digest. The metric can not + be performed on < T1 , T2, ..., Tm-1, Tm> in the following cases: - The semantic of a Type-P-segment-Packet-loss-Stream defines 2 new - results: + o Ha or Hb disappears from the path due to some change of routes; - o A value of Lk of 2 (1,0) corresponds to a mistake in the ordering - of Ha and Hb over the path coming either from the configuration - (asumption on the path) or from the processing of the vectors: bad - scrutening of the path ordering information, or some other mistake - in the measure or the reporting. It is not in the scope of this - document to go in further details which are mostly implementation - dependent. This value MUST not be used to compute packet lost - statistics. + o the order of Ha and Hb changes in the path; - o A value of Lk of 3 (1,1) corresponds to a lost of the packet in - upper segment of the path. + o Lk.a or Lk.b is undefined; -5.3. A Definition of a sample of One-way Ipdv of a segment of the path + o Lk.a has the value 1 (not observed) and Lk.b has the value 0 + (observed); - This metric defines a sample of ipdv between a pair of hosts of a - path. + o L has the value 0 (the packet was received by Dst) and Lk.ab has + the value 1 (the packet was lost between Ha and Hb). - Editor note: work in progress +5.3. A Definition of a sample of ipdv of a segment using the previous + packet selection function + + This metric defines a sample of ipdv [RFC3393] over time between a + pair of hosts using the previous packet as the selection function. 5.3.1. Metric Name - Type-P-Segment-Ipdv-Stream + Type-P-Segment-One-way-ipdv-prev-Stream 5.3.2. Metric Parameters + o Src*, the IP address of the sender. + + o Dst*, the IP address of the receiver. + + o P*, the specification of the packet type. + + o k, an integer which orders the packets sent. + + o n, an integer which orders the hosts on the path. + + o a and b, 2 integers where b > a. + + o , the hosts path digest. + + o , a list of times. + + o , a + Type-P-Spatial-One-way-Delay-Vector. + 5.3.3. Metric Units + The value of a Type-P-Segment-One-way-ipdv-prev-Stream is a pair of: + + The list of ; + + A list of pairs of interval of times and delays; + 5.3.4. Definition + Given 2 hosts, Ha and Hb, of the path , given the matrix of Type-P-Spatial-One-way-Delay-Vector for the + packets sent from Src to Dst at times : + + , + + , + + ... + + . + + We define the Type-P-Segment-One-way-ipdv-prev-Stream as the sequence + of pair of packet intervals and delay variations <(dT2_1.a , dT2.ab - + dT1.ab) ,..., (dTk_k-1.a, dTk.ab - dTk-1.ab), ..., (dTm_m-1.a, dTm.ab + - dTm-1.ab)> such that for each Tk: + + o dTk_k-1.a is either undefined if the delay dTk.a or the delay + dTk-1.a is undefined, or the interval of time, 'dTk.a - dTk-1.a', + between the 2 packets at Ha; + + o dTk_k-1.ab, is either undefined if one of the delays dTk.b, dTk.a, + dTk-1.b or dTk-1.a is undefined, or , (dTk.b - dTk.a) - (dTk-1.b - + dTk-1.a), the delay variation from Ha to Hb between the 2 packets + sent at time Tk and Tk-1. + 5.3.5. Discussion + This metric belongs to the family of inter packet delay variation + metrics (IPDV in upper case) which results can be extremely sensitive + to the inter-packet interval. + + The inter-packet interval of a end-to-end IPDV metric is under the + control of the ingress point of interest which corresponds exactly to + the Source of the packet. Unlikely, the inter-packet interval of a + segment IPDV metric is not under the control the ingress point of + interest of the measure, Ha. However, the interval will vary if + there is delay variation between the Source and Ha. Therefore, the + actual inter-packet interval must be known at Ha in order to fully + comprehend the delay variation between Ha and Hb. + +5.4. A Definition of a sample of ipdv of a segment using the minimum + delay selection function + + This metric defines a sample of ipdv [RFC3393] over time between a + pair of hosts of a path using the shortest delay as the selection + function. + +5.4.1. Metric Name + + Type-P-Segment-One-way-ipdv-min-Stream + +5.4.2. Metric Parameters + + o Src*, the IP address of the sender. + + o Dst*, the IP address of the receiver. + + o P*, the specification of the packet type. + + o k, an integer which orders the packets sent. + + o i, an integer which identifies a packet sent. + + o n, an integer which orders the hosts on the path. + + o a and b, 2 integers where b > a. + + o , the hosts path digest. + + o , a list of times. + + o , a + Type-P-Spatial-One-way-Delay-Vector. + +5.4.3. Metric Units + + The value of a Type-P-Segment-One-way-ipdv-min-Stream is a pair of: + + The list of ; + A list of times; + +5.4.4. Definition + + Given 2 hosts, Ha and Hb, of the path , given the matrix of Type-P-Spatial-One-way-Delay-Vector for the + packets sent from Src to Dst at times : + + , + + , + + ... + + . + + We define the Type-P-Segment-One-way-ipdv-min-Stream as the sequence + of times such that: + + min(dTi.ab) is the minimum value of the tuples (dTk.b - dTk.a); + + for each time Tk, dTk.ab is undefined if dTk.a or (inclusive) + dTk.b is undefined, or the real number (dTk.b - dTk.a). + +5.4.5. Discussion + + This metric belongs to the family of packet delay variation metrics + (PDV). PDV distributions are less sensitive to inter-packet interval + variations than IPDV results. + + In principle, the PDV distribution reflects the variation over many + different inter-packet intervals, from the smallest inter-packet + interval, up to the length of the evaluation interval, Tm - T1. + Therefore, when delay variation occurs and disturbs the packet + spacing observed at Ha, the PDV results will likely compare favorably + to a PDV measurement where the source is Ha and the destination is + Hb. + 6. One-to-group metrics definitions -6.1. A Definition for one-to-group One-way Delay + This metric defines metrics to measure the performance between a + source and a group of receivers. + +6.1. A Definition for One-to-group One-way Delay + + This metric defines a metric to measure one-way delay between a + source and a group of receivers. 6.1.1. Metric Name - Type-P-one-to-group-One-way-Delay-Vector + Type-P-One-to-group-One-way-Delay-Vector 6.1.2. Metric Parameters o Src, the IP address of a host acting as the source. o Recv1,..., RecvN, the IP addresses of the N hosts acting as receivers. o T, a time. o dT1,...,dTn a list of time. o P, the specification of the packet type. - o Gr, the multicast group address (optional). The parameter Gr is - the multicast group address if the measured packets are - transmitted by multicast. This parameter is to identify the + o Gr, the receiving group identifier. The parameter Gr is the + multicast group address if the measured packets are transmitted + over IP multicast. This parameter is to differentiate the measured traffic from other unicast and multicast traffic. It is - set to be optional in the metric to avoid losing any generality, - i.e. to make the metric also applicable to unicast measurement - where there is only one receivers. + optional in the metric to avoid losing any generality, i.e. to + make the metric also applicable to unicast measurement where there + is only one receiver. 6.1.3. Metric Units - The value of a Type-P-one-to-group-One-way-Delay-Vector is a set of - singletons metrics Type-P-One-way-Delay [RFC2679]. + The value of a Type-P-One-to-group-One-way-Delay-Vector is a set of + Type-P-One-way-Delay singletons [RFC2679]. 6.1.4. Definition Given a Type P packet sent by the source Src at Time T, given the N hosts { Recv1,...,RecvN } which receive the packet at the time { - T+dT1,...,T+dTn }, a Type-P-one-to-group-One-way-Delay-Vector is + T+dT1,...,T+dTn }, a Type-P-One-to-group-One-way-Delay-Vector is defined as the set of the Type-P-One-way-Delay singleton between Src and each receiver with value of { dT1, dT2,...,dTn }. -6.2. A Definition for one-to-group One-way Packet Loss +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 + Type-P-One-to-group-One-way-Packet-Loss-Vector 6.2.2. Metric Parameters o Src, the IP address of a host acting as the source. o Recv1,..., RecvN, the IP addresses of the N hosts acting as receivers. o T, a time. o T1,...,Tn a list of time. o P, the specification of the packet type. - o Gr, the multicast group address (optional). + o Gr, the receiving group identifier. 6.2.3. Metric Units - The value of a Type-P-one-to-group-One-way-Packet-Loss-Vector is a - set of singletons metrics Type-P-One-way-Packet-Loss [RFC2680]. + The value of a Type-P-One-to-group-One-way-Packet-Loss-Vector is a + set of Type-P-One-way-Packet-Loss singletons [RFC2680]. 6.2.4. Definition Given a Type P packet sent by the source Src at T and the N hosts, Recv1,...,RecvN, which should receive the packet at T1,...,Tn, a - Type-P-one-to-group-One-way-Packet-Loss-Vector is defined as a set of + Type-P-One-to-group-One-way-Packet-Loss-Vector is defined as a set of the Type-P-One-way-Packet-Loss singleton between Src and each of the receivers {,,..., }. -6.3. A Definition for one-to-group One-way Ipdv +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 IP address of a host acting as the source. + o Src, the IP address of a host acting as the source. - + Recv1,..., RecvN, the IP addresses of the N hosts acting as + o Recv1,..., RecvN, the IP addresses of the N hosts acting as receivers. - + T1, a time. + o T1, a time. - + T2, a time. + o T2, a time. - + ddT1,...,ddTn, a list of time. + o ddT1, ...,ddTn, a list of time. - + P, the specification of the packet type. + o P, the specification of the packet type. - + F, a selection function defining unambiguously the two - packets from the stream selected for the metric. + o F, a selection function defining unambiguously the two packets + from the stream selected for the metric. - + Gr, the multicast group address (optional) + o Gr, the receiving group identifier. 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]. + Type-P-One-way-ipdv singletons [RFC3393]. 6.3.4. Definition - Given a Type P packet stream, Type-P-one-to-group-One-way-ipdv-Vector + 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 selected by the selection function F, as - the difference between the value of the Type-P-one-to-group-One-way- + the difference between the value of the Type-P-One-to-group-One-way- Delay-Vector from Src to { Recv1,..., RecvN } at time T1 and the - value of the Type-P-one-to-group- One-way-Delay-Vector from Src to { + value of the Type-P-One-to-group-One-way-Delay-Vector from Src to { Recv1,...,RecvN } at time T2. T1 is the wire-time at which Src sent the first bit of the first packet, and T2 is the wire-time at which Src sent the first bit of the second packet. This metric is derived - from the Type-P-one-to- group-One-way-Delay-Vector metric. + from the Type-P-One-to-group-One-way-Delay-Vector metric. - Therefore, for a set of real number {ddT1,...,ddTn},Type-P-one- to- + Therefore, for a set of real number {ddT1,...,ddTn},Type-P-One-to- group-One-way-ipdv-Vector from Src to { Recv1,...,RecvN } at T1, T2 is {ddT1,...,ddTn} means that Src sent two packets, the first at wire-time T1 (first bit), and the second at wire-time T2 (first bit) and the packets were received by { Recv1,...,RecvN } at wire-time {dT1+T1,...,dTn+T1}(last bit of the first packet), and at wire-time {dT'1+T2,...,dT'n+T2} (last bit of the second packet), and that {dT'1-dT1,...,dT'n-dTn} ={ddT1,...,ddTn}. 7. One-to-Group Sample Statistics The defined one-to-group metrics above can all be directly achieved - from the relevant unicast one-way metrics. They managed to collect - all unicast measurement results of one-way metrics together in one - profile and sort them by receivers and packets in a multicast group. - They can provide sufficient information regarding the network - performance in terms of each receiver and guide engineers to identify - potential problem happened on each branch of a multicast routing - tree. However, these metrics can not be directly used to - conveniently present the performance in terms of a group and neither - to identify the relative performance situation. + from the relevant unicast one-way metrics. They collect all unicast + measurement results of one-way metrics together in one profile and + sort them by receivers and packets in a receiving group. They + provide sufficient information regarding the network performance in + terms of each receiver and guide engineers to identify potential + problem happened on each branch of a multicast routing tree. + + However, these metrics cannot be directly used to conveniently + present the performance in terms of a group and neither to identify + the relative performance situation. From the performance point of view, the multiparty communication services not only require the absolute performance support but also the relative performance. The relative performance means the difference between absolute performance of all users. Directly using the one-way metrics cannot present the relative performance situation. However, if we use the variations of all users one-way parameters, we can have new metrics to measure the difference of the absolute performance and hence provide the threshold value of relative performance that a multiparty service might demand. A very @@ -1152,63 +1307,63 @@ and report the group performance and relative performance to save the report transmission bandwidth. Statistics have been defined for One- way metrics in corresponding RFCs. They provide the foundation of definition 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 the time dimension while the later one can have statistics over both time and space dimensions. This space dimension is introduced by the Matrix concept as - illustrated in Figure 9. For a Matrix M each row is a set of One-way + illustrated in Figure 4. For a Matrix M each row is a set of One-way singletons spreading over the time dimension and each column is another set of 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 9: Matrix M (n*m) + Figure 4: Matrix M (n*m) - In Matrix M, each element is a One-way delay singleton. Each column + In Matrix M, each element is a one-way delay singleton. Each column is a delay vector 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 row is a set of One-way delays observed during a sampling interval at one of the points of interest. It presents the delay performance at a receiver over the time dimension. Therefore, one can either calculate statistics by rows over the space dimension or by 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 + 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 @@ -1286,72 +1441,72 @@ 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 Src, the IP address of a host; - o G, the Group IP address + o G, the receiving group identifier; - o N, the number of Receivers (Recv1, Recv2, ... RecvN) + o N, the number of Receivers (Recv1, Recv2, ... RecvN); - o T, a time (start of test interval) + o T, a time (start of test interval); - o Tf, a time (end of test interval) + o Tf, a time (end of test interval); o K, the number of packets sent from the source during the test - interval - + interval; o J[n], the number of packets received at a particular Receiver, n, - where 1<=n<=N + where 1<=n<=N; - o lambda, a rate in reciprocal seconds (for Poisson Streams) + o lambda, a rate in reciprocal seconds (for Poisson Streams); o incT, the nominal duration of inter-packet interval, first bit to - first bit (for Periodic Streams) + 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) + Periodic Streams); o TstampSrc, the wire time of the packet as measured at MP(Src) (the - Source Measurement Point) + 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 + 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 + is not truncated; - o dT, shorthand notation for a one-way delay singleton value + o dT, shorthand notation for a one-way delay singleton value; 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 + Receivers; o DV, shorthand notation for a one-way delay variation singleton - value + 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 . | . | . | @@ -1350,21 +1505,21 @@ 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 + Figure 5: One-to-Group 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). @@ -1394,39 +1549,39 @@ 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 + Figure 6: 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 + Figure 7: 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). @@ -1451,21 +1606,21 @@ 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 + Figure 8: 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). @@ -1476,21 +1631,21 @@ Type-P-One-to-Group-Loss-Ratio = K,N --- 1 \ = --- * > L(k,n) K*N / --- k,n = 1 - Figure 14 + Figure 9 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- @@ -1500,21 +1655,21 @@ 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 + Figure 10: 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 @@ -1536,31 +1691,31 @@ k=1 = ----------------------------- / K \ | --- | | \ | K - Min | > Ln(k) | | / | | --- | \ k=1 / N - Figure 16: Type-P-Comp-Loss-Ratio-Receiver-n + Figure 11: 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 +8. Measurement Methods: Scalability 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 @@ -1651,21 +1806,21 @@ . | . | n RnS1 RnS2 RnS3 ... RnSk / S1M S2M S3M ... SnM Stats over space \------------- ------------/ \/ Stat over space and time - Figure 17: Impact of space aggregation on multimetrics Stat + Figure 12: Impact of space aggregation on multimetrics Stat 2 methods are available to compute statistics on the resulting matrix: o metric is computed over time and then over space; o metric is computed over space and then over time. They differ only by the order of the time and of the space aggregation. View as a matrix this order is neutral as does not impact the result, but the impact on a measurement deployment is @@ -1701,24 +1856,24 @@ Note: In some specific cases one may need sample of singletons over space. To address this need it is suggested firstly to limit the number of test and the number of test packets per seconds. Then reducing the size of the sample over time to one packet give sample of singleton over space.. 8.3.1. Impact on group stats 2 methods are available to compute group statistics: - o method1: Figure 10 andFigure 13 illustrate the method chosen: the + o method1: Figure 5 andFigure 8 illustrate the method chosen: the one-to-one statistic is computed per interval of time before the computation of the mean over the group of receivers; - o method2: Figure 17 presents the second one, metric is computed + o method2: Figure 12 presents the second one, metric is computed over space and then over time. 8.3.2. Impact on spatial stats 2 methods are available to compute spatial statistics: o method 1: spatial segment metrics and statistics are preferably computed over time by each points of interest; o method 2: Vectors metrics are intrinsically instantaneous space @@ -1822,30 +1977,20 @@ As explained in section 8, the measurement method will have impact on the analysis of the measurement result. Therefore, it should be reported. 9.3. Metric identification IANA assigns each metric defined by the IPPM WG with a unique identifier as per [RFC4148] in the IANA-IPPM-METRICS-REGISTRY-MIB. - To avoid misunderstanding and to address specific reporting - constraints, section [passive_metrics] of this memo gives distinct - names to passive metrics and Section 13 requests a distinct metric - identifier for each metrics the memo defines. - - As it is crucial for composition of metrics to know the methodology - used (e.g. generation method, detection method...), the report of a - metric result used in composition of metrics MUST always include its - metric identifier. - 9.4. Reporting data model This section presents the elements of the datamodel and the usage of the information reported for real network performance analysis. It is out of the scope of this section to define how the information is reported. The data model is build with pieces of information introduced and explained in one-way delay definitions [RFC2679], in packet loss definitions [RFC2680] and in IPDV definitions[RFC3393][RFC3432]. It @@ -2040,173 +2183,194 @@ 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 + ietfSpatialOneWayDelayVector 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 - Spatial-Packet-Loss-Vector OBJECT-IDENTITY + ietfSpatialPacketLossVector OBJECT-IDENTITY STATUS current DESCRIPTION "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-ipdv-Vector OBJECT-IDENTITY + ietfSpatialOneWayIpdvVector OBJECT-IDENTITY + STATUS current DESCRIPTION "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-Segment-One-way-Delay-Stream OBJECT-IDENTITY + ietfSpatialSegmentOnewayDelayStream 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 + ietfSpatialSegmentPacketLossStream 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 + + ietfSpatialSegmentOneWayIpdvPrevStream OBJECT-IDENTITY STATUS current DESCRIPTION - "Type-P-Spatial-Segment-ipdv-Stream" - + "Type-P-Spatial-Segment-ipdv-prev-Stream" REFERENCE "Reference "RFCyyyy, section 5.3." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn + ietfSpatialSegmentOneWayIpdvMinStream OBJECT-IDENTITY + + STATUS current + + DESCRIPTION + + "Type-P-Spatial-Segment-ipdv-minStream" + + REFERENCE + + "Reference "RFCyyyy, section 5.4." + + -- RFC Ed.: replace yyyy with actual RFC number & remove this + note + + := { ianaIppmMetrics nn } -- IANA assigns nn + -- One-to-group metrics - one-to-group-One-way-Delay-Vector OBJECT-IDENTITY + ietfOneToGroupOneWayDelayVector OBJECT-IDENTITY STATUS current DESCRIPTION "Type-P-one-to-group-One-way-Delay-Vector" REFERENCE - "Reference "RFCyyyy, section 5.1." + "Reference "RFCyyyy, section 6.1." -- 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 - + ietfOneToGroupOneWayPktLossVector OBJECT-IDENTITY STATUS current DESCRIPTION "Type-P-one-to-group-One-way-Packet-Loss-Vector" REFERENCE - "Reference "RFCyyyy, section 5.2." + "Reference "RFCyyyy, section 6.2." + -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn - one-to-group-One-way-ipdv-Vector OBJECT-IDENTITY + ietfOneToGroupOneWayIpdvVector OBJECT-IDENTITY STATUS current DESCRIPTION "Type-P-one-to-group-One-way-ipdv-Vector" REFERENCE - "Reference "RFCyyyy, section 5.3." + "Reference "RFCyyyy, section 6.3." -- RFC Ed.: replace yyyy with actual RFC number & remove this note := { ianaIppmMetrics nn } -- IANA assigns nn - One-to-Group-Mean-Delay OBJECT-IDENTITY + -- One to group statistics + + -- + + ietfOneToGroupMeanDelay OBJECT-IDENTITY STATUS current DESCRIPTION "Type-P-One-to-Group-Mean-Delay" REFERENCE "Reference "RFCyyyy, section 6.3.3." @@ -2203,67 +2367,66 @@ 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 + ietfOneToGroupRangeMeanDelay 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 + ietfOneToGroupMaxMeanDelay 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 + ietfOneToGroupLossRatio 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 -- @@ -2261,21 +2424,22 @@ "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 + ietfOneToGroupLossRatioRange OBJECT-IDENTITY + STATUS current DESCRIPTION "Type-P-One-to-Group-Loss-Ratio-Range" REFERENCE "Reference "RFCyyyy, section 6.4.2." @@ -2366,21 +2531,21 @@ 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). + Copyright (C) The IETF Trust (2008). 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. This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF