IP Performance Measurement (ippm) B. Trammell Internet-Draft ETH Zurich Intended status: Informational October 12, 2012 Expires: April 15, 2013 Hybrid Measurement using IPPM Metrics draft-trammell-ippm-hybrid-ps-00.txt Abstract Hybrid measurement is the combination of metrics derived from passive and active measurement to produce a measurement result. This document discusses use cases for hybrid measurement using metrics defined within the IPPM framework 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 15, 2013. Copyright Notice Copyright (c) 2012 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 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. Trammell Expires April 15, 2013 [Page 1] Internet-Draft Hybrid Measurement October 2012 1. Introduction Hybrid measurement is the combination of metrics derived from passive and active measurement to produce a measurement result. This combination can be either spatial or temporal. For example, one way delay to a given endpoint could be derived from passive measurements from a sample of remote endpoints with which traffic is frequently exchanged, and supplemented with active measurements from endpoints with less frequent traffic, to build a "delay map" to a certain point in the network. On the temporal side, loss or delay metrics could be passively measured and stored over time to provide a baseline against which actively-measured loss or delay metrics could be compared during troubleshooting, in order to determine whether a specific path or path segment is contributing to an observed performance problem. The IPPM working group has produced a framework [RFC2330] for and rich set of well-defined metrics (e.g. [RFC2679], [RFC2680]) for IP performance measurement using active methods, and protocols for measuring them. These metrics could form the basis of a platform for hybrid measurement, provided that passively-derived metrics were defined to compatible with the corresponding actively-derived metrics; or alternately, provided that methodologies for passive measurement can be defined for each of the existing active metrics to be used, such that those methodologies produce values for the metrics equivalent to the active methodology for the same metric parameters, given some assumptions about the packet stream to be observed to perform the passive measurement, and given tolerances for uncertainty in the results. 2. Problem Statement Complicating the definition of hybrid measurements is that passive measurement must make do with the traffic that is observable, while active measurement has some control over the traffic observed. Measurements for some set of parameters are not possible if no suitable traffic is observed, and the timing of the measurement cannot be controlled. Placement of the observation points for passive measurement along a path additionally introduces uncertainty in the results. For example, passive one-way delay measurement could be performed using two measurement points, one close to each endpoint, with synchronized clocks, comparing the observation times of packets via their hashes. This will not produce a value which is directly comparable to a Type-P-One-way-Delay measured as specified in section 3.6 of [RFC2679], because it will not account for the one- way-delay from the source to the source-side observation point, or from the destination-side observation point to the destination. Any specification of hybrid measurement using IPPM metrics must handle Trammell Expires April 15, 2013 [Page 2] Internet-Draft Hybrid Measurement October 2012 these complications. The proposed specification entails: o Definition of scenarios and requirements for hybrid measurement. o Selection of existing IPPM metrics to be used for the active side of hybrid measurements to meet these requirements. o Definition of equivalent passive measurement methodologies for each selected metric, specifically addressing the assumptions about the observed packet stream which must hold for the metric to be valid, and with a specific allowance for the measurement and/or estimation of uncertainty due to uncontrollable conditions or observation point placement. o Definition of metrics based on these passive methodologies, or modification of the definition of existing metrics to add passive methodologies. o Definition of methods for comparison between active and passive metrics allowing for estimated uncertainty. o Definition of methods for spatial and temporal composition of active and passive metrics together allowing for estimated uncertainty. 3. Scenarios and Requirements [EDITOR'S NOTE: This section will contain scenarios and requirements for hybrid measurement. Candidate scenarios include (1) use of passive measurement to measure delay, loss, etc. on paths on which traffic is frequently sent, supplemented with active measurement on low-traffic paths or during low-traffic times and (2) use of passive measurement to establish a long-term baseline against which active measurements can be compared to detect and isolate anomalies, as in the introduction.] 4. Selected IPPM Metrics [EDITOR'S NOTE: this section will contain information on the metrics selected for passive measurement, and initial discussion of passive measurement methodologies for them. Metric definition will presumably be left for a future document.] Trammell Expires April 15, 2013 [Page 3] Internet-Draft Hybrid Measurement October 2012 5. Security Considerations [EDITOR'S NOTE: this section will discuss general security considerations of using passive measurement for performance, both on the potential for attacks against the measurement system as well as the potential for privacy or security threats posed by the measurement system itself.] 6. IANA Considerations This document contains no considerations for IANA. 7. References 7.1. Normative References [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, "Framework for IP Performance Metrics", RFC 2330, May 1998. 7.2. Informative References [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. Author's Address Brian Trammell Swiss Federal Institute of Technology Zurich Gloriastrasse 35 8092 Zurich Switzerland Phone: +41 44 632 70 13 Email: trammell@tik.ee.ethz.ch Trammell Expires April 15, 2013 [Page 4]