Network Working Group L. Zheng Internet-Draft S. Aldrin Intended status: Informational Huawei Technologies Expires: April 21, 2014 October 18, 2013 Gap Analysis of IPPM Passive Measurements draft-zheng-ippm-passive-gap-analysis-00.txt Abstract This document performs a gap analysis of the current state of IPPM WG and ongoing work, in terms of passive measurements, according to the new charter of the IPPM WG. Requirements Language The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in RFC 2119 [RFC2119]. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. 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." This Internet-Draft will expire on April 21, 2014. Copyright Notice Copyright (c) 2013 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect Zheng & Aldrin Expires April 21, 2014 [Page 1] Internet-Draft Gap Analysis of IPPM Passive Measurement October 2013 to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Passive Measurements VS Active Measurements . . . . . . . . . 2 3. Gap Analysis for Passive Measurements . . . . . . . . . . . . 3 3.1. Framework for IP Performance Metrics . . . . . . . . . . 3 3.2. IP Performance Metrics . . . . . . . . . . . . . . . . . 4 3.3. Registry . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Future Work for Passive Measurement . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 5 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 8.1. Normative References . . . . . . . . . . . . . . . . . . 6 8.2. Informative References . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction The IPPM working group has been recently re-chartered. According to the new charter, passive measurement and hybrid measurement methods are now included. This document performs a gap analysis of the current status of work in the IPPM WG in terms of passive measurements. Section 2 of the document gives a brief introduction of passive measurement. Section 3 summarizes the current status of the IPPM, and gives an analysis on what is missing or was not considered, for passive measurements, in terms of framework of metrics, measurement of metrics, registry, etc. Section 4 lists the future work required for passive measurements based on the gap analysis. The analysis for hybrid measurements is out of the scope of this document. 2. Passive Measurements VS Active Measurements Passive and active measurements are two common approaches for monitoring the network. The passive approach measures real traffic and does not increase the traffic on the network for the measurements. This makes it attractive for in-service monitoring, network trouble-shooting and fault location. Since the passive approach may require viewing packets on the network, there can be privacy or security issues. The active approach relies on the capability to inject test packets into the network, but as such it creates extra traffic. The benefit of active measurements is that Zheng & Aldrin Expires April 21, 2014 [Page 2] Internet-Draft Gap Analysis of IPPM Passive Measurement October 2013 they can be run from virtually anywhere in the network. One difficulty, though, is that the discrete nature of active probing limits the resolution of the measurements. There is also evidence of limitations of probe-based packet loss measurement in low-loss environments. Both passive and active measurements have their strengths and should be regarded as complementary. 3. Gap Analysis for Passive Measurements This section gives an analysis on what is missing for passive measurements in relation to IPPM, in terms of framework of metrics, measurement of metrics and registry. 3.1. Framework for IP Performance Metrics The IETF IP Performance Metrics (IPPM) working group first created a framework for metric development in [RFC2330], which enabled development of many fundamental metrics. [RFC2330] has been updated once by [RFC5835], which describes a detailed framework for composing and aggregating metrics originally defined in [RFC2330]. The ongoing work [I-D.ietf-ippm-2330-update] proposes to update the IPPM Framework with advanced considerations for measurement methodology and testing. It describes new stream parameters for both network characterization and support of application design using IPPM metrics. All the previous work done for IP performance metrics framework and the ongoing update for the framework has the assumption, which is not explicitly stated, that the measurement method of the metrics is active measurement. The result of this is, while many of the current framework aspects are still applicable to passive measurement, some of them are not applicable. In one example, section 11 of [RFC2330] introduces a separation between three distinct notions: singletons, samples, and statistics, which are not applicable to passive measurements, since the test packet is not required for passive measurements, nor is the sampling. Zheng & Aldrin Expires April 21, 2014 [Page 3] Internet-Draft Gap Analysis of IPPM Passive Measurement October 2013 But there are certainly equivalent concepts in passive measurements. For example, consider using TCP traffic to determine the two-way delay between two hosts. A singleton would be the timing of a single sequence number - acknowledgement pairing, a sample would be a collection of these, and the statistical metric would take the minimum, over a short time interval (in order to reduce or eliminate think-time and delayed-ACK effects). In another example, the concept of a packet of type "P", while still applicable in principle, will have to be specified differently. An updated or new passive framework document is needed, while equivalent concepts need to be carried over as much as possible with passive-friendly definitions. 3.2. IP Performance Metrics The IPPM WG has defined more than 30 metrics, the most recently published document that defines metrics is [RFC6049]. The commonly used metrics include IPPM Metrics for Measuring Connectivity [RFC2678], One-way Delay Metrics[RFC2679], One-way Packet Loss Metrics [RFC2680], Round-trip Delay Metrics [RFC2681], One-way Loss Pattern Sample Metrics[RFC3357], IP Packet Delay Variation Metric [RFC3393], IPPM Metrics for periodic streams [RFC3432] etc. All the existing metrics defined follow the framework for IP performance metrics [RFC2330] , which has the implicit assumption that the measurement method of the metrics is active measurement. Passive methodologies for existing [RFC2330] based active metrics need to be defined, which would require loosening some of the constraints as well as changes to the guidelines. For example, the measurement methodologies for One-way Delay Metrics [RFC2679] and One-way Packet Loss Metrics [RFC2680] call for, amongst other things, selection of the Src and Dst addresses at the Src host. This will be difficult to achieve for passive measurement. Careful examination and thorough analysis needs to be made, in order to decide, which aspects of current metrics need to be redefined for passive measurements, and which aspects could be reused by passive measurements as is. 3.3. Registry [RFC4148] defines an initial registry of the metrics defined in the IPPM WG and the rules to manage the registry. However, [RFC4148] was obsoleted by [RFC6248] because it was "not believed to be feasible or even useful to register every possible combination of Type P, metric parameters, and Stream parameters using the current structure of the IPPM Metrics Registry". This led to the [RFC4148] registry having "very few users, if any". Zheng & Aldrin Expires April 21, 2014 [Page 4] Internet-Draft Gap Analysis of IPPM Passive Measurement October 2013 The ongoing work [I-D.bagnulo-ippm-new-registry-independent] and [I-D.bagnulo-ippm-new-registry] creates, a registry for commonly used metrics, defines the rules for assignments in the new registry and performs initial allocations, respectively. [I-D.bagnulo-ippm-new-registry-independent] proposes one particular registry structure with independent registries for each of the fields involved, while [I-D.bagnulo-ippm-new-registry] explores an alternative structure with a single registry with multiple sub- registries. The metrics for passive measurement should be taken into consideration for both registry structure designs. 4. Future Work for Passive Measurement Based on the above gap analysis, it could be concluded that the following new work needs to be done in the IPPM working group: 1. Framework for metrics: An passive-friendly updated framework document is needed for passive measurement. 2. Metrics: Careful examination on currently defined metrics, particularly the measurement aspects, needs to be made by the working group. Some metrics need to be updated for passive measurement, some metrics may be reused by passive measurements as is. New metrics may also need to be defined for passive measurement. 3. Registry: The passive measurement should be taken into consideration for the ongoing registry structure design work. 5. Security Considerations This document does not bring new security issue to IPPM. 6. IANA Considerations This document makes no request to IANA. 7. Acknowledgements The authors would like to thank Brain Trammell, Paul Coverdale for their valuable comments. 8. References Zheng & Aldrin Expires April 21, 2014 [Page 5] Internet-Draft Gap Analysis of IPPM Passive Measurement October 2013 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 8.2. Informative References [I-D.bagnulo-ippm-new-registry-independent] Bagnulo, M., Burbridge, T., Crawford, S., Eardley, P., and A. Morton, "A registry for commonly used metrics. Independent registries", draft-bagnulo-ippm-new-registry- independent-01 (work in progress), July 2013. [I-D.bagnulo-ippm-new-registry] Bagnulo, M., Burbridge, T., Crawford, S., Eardley, P., and A. Morton, "A registry for commonly used metrics", draft- bagnulo-ippm-new-registry-01 (work in progress), July 2013. [I-D.ietf-ippm-2330-update] Fabini, J. and A. Morton, "Advanced Stream and Sampling Framework for IPPM", draft-ietf-ippm-2330-update-01 (work in progress), October 2013. [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, "Framework for IP Performance Metrics", RFC 2330, May 1998. [RFC2678] Mahdavi, J. and V. Paxson, "IPPM Metrics for Measuring Connectivity", RFC 2678, September 1999. [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. [RFC2681] Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip Delay Metric for IPPM", RFC 2681, September 1999. [RFC3357] Koodli, R. and R. Ravikanth, "One-way Loss Pattern Sample Metrics", RFC 3357, August 2002. [RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation Metric for IP Performance Metrics (IPPM)", RFC 3393, November 2002. Zheng & Aldrin Expires April 21, 2014 [Page 6] Internet-Draft Gap Analysis of IPPM Passive Measurement October 2013 [RFC3432] Raisanen, V., Grotefeld, G., and A. Morton, "Network performance measurement with periodic streams", RFC 3432, November 2002. [RFC4148] Stephan, E., "IP Performance Metrics (IPPM) Metrics Registry", BCP 108, RFC 4148, August 2005. [RFC5835] Morton, A. and S. Van den Berghe, "Framework for Metric Composition", RFC 5835, April 2010. [RFC6049] Morton, A. and E. Stephan, "Spatial Composition of Metrics", RFC 6049, January 2011. [RFC6248] Morton, A., "RFC 4148 and the IP Performance Metrics (IPPM) Registry of Metrics Are Obsolete", RFC 6248, April 2011. Authors' Addresses Lianshu Zheng Huawei Technologies China Email: vero.zheng@huawei.com Sam K. Aldrin Huawei Technologies Email: aldrin.ietf@gmail.com Zheng & Aldrin Expires April 21, 2014 [Page 7]