Network Working Group E. Stephan Internet Draft France Telecom R&D Document: draft-stephan-ippm-spatial-metrics-00.txt Category: Informational Sept 12, 2002 IPPM spatial metrics measurement Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026 [1] except that the right to produce derivative works is not granted. 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. Abstract The IETF IP Performance Metrics (IPPM) working group has standardized metrics for measuring end to end performance. Measurements system scope is often limited to administrative boundaries. This memo defines spatial metrics both for measuring end-to-end network performance using aggregation of sequence of network measures and for measuring the performance of segment of an IP path trajectory. It distinguishes clearly the decomposition of one end-to-end measure result in a sequence of per hop results from the aggregation of a sequence of per hop measure results in an end-to-end result. Table of Contents 1. Introduction................................................2 2. Terminology.................................................3 2.1. Spatial metric..............................................3 Stephan Informational - Expires March 2003 [Page 1] Internet Draft spatial metrics September 2002 2.2. Asynchronous spatial metrics................................3 2.3. Trajectory..................................................3 3. Motivation..................................................3 3.1. Instantaneous end to end measure decomposition..............3 3.2. End-to-end measures aggregation.............................4 4. Metrics for end-to-end measure decomposition................4 4.1. Spatial one way delay.......................................4 4.2. One way delay Trajectory metric.............................5 4.3. Aggregated One way delay metric.............................6 5. Metrics for end-to-end measures aggregation.................7 5.1. Asynchronous One way delay Trajectory metric................7 5.2. Asynchronous Aggregated One way delay metric................7 6. Spatial Packet loss metrics.................................8 7. Spatial ipdv metrics........................................8 8. Security Considerations.....................................8 8.1. Privacy.....................................................8 8.2. Measurement aspects.........................................8 9. Issues......................................................9 10. Acknowledgments.............................................9 11. Author's Addresses..........................................9 1. Introduction The metrics specified derivate from those standardized by IPPM Working Group. There are built on notions introduced and discussed in the IPPM Framework document, RFC 2330 [2]. The reader should be familiar with these documents. The IPPM Framework consists in 4 major components: + A general framework for defining performance metrics, described in the Framework for IP Performance Metrics, RFC 2330; + A set of standardized metrics, which conform to this framework. The IPPM Metrics for Measuring Connectivity, RFC 2678 [3]. The One- way Delay Metric for IPPM, RFC 2679 [4]. The One-way Packet Loss Metric for IPPM, RFC 2680 [5]. The Round-trip Delay Metric for IPPM, RFC 2681 [6]; + Emerging metrics which are being specified in respect of this framework; + A Reporting MIB to exchange the results of the measures. It is an interface between a system of measure and the administrative entities interested in these results. This proxy controls the access to the results. These entities use the results to compute statistics and aggregated metrics. The structure of the memo is as follows: Stephan Informational - Expires March 2003 [Page 2] Internet Draft spatial metrics September 2002 + A 'singleton' analytic metric, called Type-P-spatial-one-way- delay, will be introduced to measure the one-way delay between 2 consecutive hosts of an IP path. + Using this singleton metric, a 'sample', called Type-P-one-way- delay-trajectory, will be introduced to measure the sequence of Type-P-spatial-one-way-delay of the successive pair of hosts of the path. + Using this sample the end to end metric, called Type-P- aggregated-one-way-delay, is defined to measure the end to end delay. + Using the Type-P-one-way-delay metric, the Type-P-spatial-one- way-delay metric, the Type-P-aggregated-one-way-delay metric and the Type-P-asynchronous-aggregated-one-way-delay metric, a 'sample', called Type-P-asynchronous-one-way-delay-trajectory, will be introduced to measure the sequence of delays of a sequence of clouds of an IP path. + Using this sample the end to end metric, called Type-P- asynchronous-aggregated-one-way-delay, is defined to measure the end to end delay. 2. Terminology 2.1. Spatial metric A metric is spatial if one of the hosts involved is neither the sender nor the destination of the measurement packet. 2.2. Asynchronous spatial metrics A spatial metric is named asynchronous if its definition involves different measurement packets. 2.3. Trajectory A trajectory is a sequence of hosts of an IP path. All the hosts of the path may not be present in the sequence. 3. Motivation 3.1. Instantaneous end to end measure decomposition There is a need to standardize spatial metrics to permit the decomposition of standard end-to-end measures. + for locating delay consumption in a IP path; Stephan Informational - Expires March 2003 [Page 3] Internet Draft spatial metrics September 2002 + for locating the loss of packets on an IP path; + for trajectory discovery; + for troubleshooting the network; + for designing and engineering the networks; + for measuring the performance of a multicast network; + for controlling the performance of the inter domain services. These metrics have to be standardized to permit their results to be collected in the IPPM REPORTING MIB. 3.2. End-to-end measures aggregation The IPPM WG has designed metrics for measuring end-to-end performance. There is not currently standard IP measurement packets to perform inter domain end-to-end measures. They may only be performed using aggregation of sequence of intra domain measure results. To permit interdomain end-to-end measure results aggregations there is a need to standardize spatial metrics + for delay aggregation; + for packet loss aggregation; + for jitter aggregation. These metrics have to be standardized to permit their results to be collected in the IPPM REPORTING MIB. 4. Metrics for end-to-end measure decomposition 4.1. Spatial one way delay 4.1.1. Metric Name Type-P-spatial-one-way-delay 4.1.2. Metric Parameters + H0, the address of the sender. + Hn, the address of the receiver. + I, An integer which ordered the hosts in the path. Stephan Informational - Expires March 2003 [Page 4] Internet Draft spatial metrics September 2002 + Hi, exchange points of the path digest. + T0, a time. + T1,..., Tn a list of time. + dT1,..., dTn a list of time. + P, the specification of the packet type. + a path digest. 4.1.3. Metric Units The unit is the same as the singleton Type-P-One-way-Delay defined in [4]. The value of a Type-P-spatial-One-way-Delay is either a real number, or an undefined (informally, infinite) number of seconds. 4.1.4. Definition Given a Type P packet sent by the source H0 at T0 to Hn in the path , given the sequence of time of arrival of the packets in , a Type-P-spatial-one-way-delay metric is defined for a hop of the path as following: For a real number dTi, the Type-P-spatial-one-way-delay from Hi to Hi+1 at Ti is dTi means that Hi saw the first bit of a Type-P packet to Hi+1 at wire-time Ti and that Hi+1 saw the last bit of that packet at wire-time Ti+dTi. 4.2. One way delay Trajectory metric 4.2.1. Metric Name Type-P-one-way-delay-trajectory 4.2.2. Metric Parameters + H0, the address of the sender. + Hn, the address of the receiver. + I, An integer which ordered the hosts in the path. + Hi, exchange points of the path digest. + T0, a time. + dT1,..., dTn a list of time. Stephan Informational - Expires March 2003 [Page 5] Internet Draft spatial metrics September 2002 + P, the specification of the packet type. + a path digest. 4.2.3. Metric Units A sequence of time. 4.2.4. Definition Given a Type-P packet sent by the source H0 at T0 to Hn in the path , given the sequence of time of arrival of the packet in , a Type-P-one-way-delay-trajectory metric is defined as the sequence of the Type-P-spatial-one-way-delay values 4.3. Aggregated One way delay metric 4.3.1. Metric Name Type-P-aggregated-one-way-delay 4.3.2. Metric Parameters + H0, the address of the sender. + Hn, the address of the receiver. + T0, a time. + dT1,..., dTn a list of time. + P, the specification of the packet type. + a trajectory. 4.3.3. Metric Units A time. 4.3.4. Definition Given a Type-P-one-way-delay-trajectory metric value of the trajectory performed using a single measurement packet of type P sent at the time T0 by H0, a Type-P- aggregated-one-way-delay metric is defined as the sum of each term of the Type-P-one-way-delay-trajectory. Stephan Informational - Expires March 2003 [Page 6] Internet Draft spatial metrics September 2002 4.3.5. Discussion A Type-P-aggregated-one-way-delay measure is performed during a Type- P-one-way-delay measure. As they measure the performance of the same measurement packet the result of a Type-P-aggregated-one-way-delay measure should be identical to the result of the Type-P-one-way-delay measure. Practically these results will differ. 5. Metrics for end-to-end measures aggregation 5.1. Asynchronous One way delay Trajectory metric 5.1.1. Metric Name Type-P-asynchronous-one-way-delay-trajectory 5.1.2. Metric Parameters + H0...Hn, the addresses of the hosts + I, An integer which ordered the hosts in the path. + Hi, exchange points of the path digest. + P, the specification of the packet type. 5.1.3. Metric Units A sequence of time. 5.1.4. Definition Given the hops , ... , given the Type-P- one-way-delay Ti from Hi to Hi+1 or the Type-P-spatial-one-way-delay Ti from Hi to Hi+1 or the Type-P-aggregated-one-way-delay Ti from Hi to Hi+1 or the Type-P-asynchronous-aggregated-one-way-delay Ti from Hi to Hi+1, a Type-P-asynchronous-one-way-delay-trajectory metric is defined as the sequence of the values . 5.2. Asynchronous Aggregated One way delay metric 5.2.1. Metric Name Type-P-asynchronous-aggregated-one-way-delay 5.2.2. Metric Parameters Stephan Informational - Expires March 2003 [Page 7] Internet Draft spatial metrics September 2002 + T1,..., Tn a list of time. 5.2.3. Metric Units A time. 5.2.4. Definition Given a Type-P-asynchronous-one-way-delay-trajectory metric value, a Type-P-asynchronous-aggregated-one-way-delay metric is defined as the sum of each term of the Type-P- asynchronous-one-way-delay-trajectory. 6. Spatial Packet loss metrics TO BE SPECIFIED 7. Spatial ipdv metrics TO BE SPECIFIED 8. Security Considerations Since this draft proposes sample metrics based on the One-way Delay singleton metric defined in RFC2679 and RFC2680 it inherits the security considerations mentioned in this RFC. 8.1. Privacy The privacy concerns of network measurement are intrinsically limited by the active measurements. Unlike passive measurements, there can be no release of existing user data. 8.2. Measurement aspects Conducting Internet measurements raises both security and privacy concerns. This memo does not specify an implementation of the metrics, so it does not directly affect the security of the Internet nor of applications which run on the Internet. However, implementations of these metrics must be mindful of security and privacy concerns. There are two types of security concerns: potential harm caused by the measurements, and potential harm to the measurements. The measurements could cause harm because they are active, and inject packets into the network. The measurement parameters MUST be Stephan Informational - Expires March 2003 [Page 8] Internet Draft spatial metrics September 2002 carefully selected so that the measurements inject trivial amounts of additional traffic into the networks they measure. If they inject "too much" traffic, they can skew the results of the measurement, and in extreme cases cause congestion and denial of service. The measurements themselves could be harmed by routers giving measurement traffic a different priority than "normal" traffic, or by an attacker injecting artificial measurement traffic. If routers can recognize measurement traffic and treat it separately, the measurements will not reflect actual user traffic. If an attacker injects artificial traffic that is accepted as legitimate, the loss rate will be artificially lowered. Therefore, the measurement methodologies SHOULD include appropriate techniques to reduce the probability measurement traffic can be distinguished from "normal" traffic. Authentication techniques, such as digital signatures, may be used where appropriate to guard against injected traffic attacks. 9. Issues Complete the terminology section. Define the trajectory packet loss metrics and corresponding statistics. Define the trajectory ipdv metrics. 10. Acknowledgments 11. Author's Addresses Emile STEPHAN France Telecom R & D 2 avenue Pierre Marzin F-22307 Lannion cedex Phone: (+ 33) 2 96 05 11 11 Email: emile.stephan@francetelecom.com Full Copyright Statement "Copyright (C) The Internet Society (2001). All Rights Reserved. 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