--- 1/draft-ietf-ippm-active-passive-03.txt 2015-12-10 16:15:08.165225695 -0800 +++ 2/draft-ietf-ippm-active-passive-04.txt 2015-12-10 16:15:08.197226479 -0800 @@ -1,44 +1,45 @@ Network Working Group A. Morton Internet-Draft AT&T Labs -Intended status: Informational November 2, 2015 -Expires: May 5, 2016 +Intended status: Informational December 10, 2015 +Expires: June 12, 2016 Active and Passive Metrics and Methods (and everything in-between, or Hybrid) - draft-ietf-ippm-active-passive-03 + draft-ietf-ippm-active-passive-04 Abstract This memo provides clear definitions for Active and Passive performance assessment. The construction of Metrics and Methods can be described as Active or Passive. Some methods may use a subset of both active and passive attributes, and we refer to these as Hybrid - Methods. + Methods. This memo also describes multiple dimensions to help + evaluate new methods as they emerge. 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 May 5, 2016. + This Internet-Draft will expire on June 12, 2016. Copyright Notice Copyright (c) 2015 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 @@ -91,48 +92,48 @@ packet stream and observations of the stream. A Passive metric or method depends *solely* on observation of one or more existing packet streams. The streams only serve measurement when they are observed for that purpose, and are present whether measurements take place or not. As new techniques for assessment emerge it is helpful to have clear definitions of these notions. This memo provides more detailed definitions, defines a new category for combinations of traditional - active and passive techniques, and discusses means to evaluate new - techniques as they emerge. + active and passive techniques, and discusses dimensions to evaluate + new techniques as they emerge. This memo provides definitions for Active and Passive Metrics and Methods based on long usage in the Internet measurement community, and especially the Internet Engineering Task Force. This memo also - describes the comnination of fundamental Active and Passive + describes the combination of fundamental Active and Passive categories, which are called Hybrid Methods and Metrics. 1.1. 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]. 2. Purpose and Scope The scope of this memo is to define and describe Active and Passive versions of metrics and methods which are consistent with the long- time usage of these adjectives in the Internet measurement community and especially the Internet Engineering Task Force. Since the science of measurement is expanding, we provide a category for combinations of the traditional extremes, treating Active and Passive as a continuum and designating combinations of their attributes as Hybrid methods. Further, this memo's purpose includes describing multiple dimensions - in which to evaluate methods as they emerge. + to evaluate new methods as they emerge. 3. Terms and Definitions This section defines the key terms of the memo. Some definitions use the notion of "stream of interest" which is synonymous with "population of interest" defined in clause 6.1.1 of ITU-T Recommendation Y.1540 [Y.1540]. The definitions are consistent with [I-D.zheng-ippm-framework-passive]. 3.1. Performance Metric @@ -146,50 +147,51 @@ 3.2. Method of Measurement The procedure or set of operations having the object of determining a Measured Value or Measurement Result. 3.3. Observation Point See section 2 of [RFC7011] for this definition (a location in the network where packets can be observed), and related definitions. The comparable term defined in IETF literature on Active measurement is - Measurement Point, see section 4.1 of [RFC5835]. Two terms have come - into use describing similar actions at the identified point in the - network path. + Measurement Point, see section 4.1 of [RFC5835]. Both of these terms + have come into use describing similar actions at the identified point + in the network path. 3.4. Active Methods Active measurement methods have the following attributes: - 1. Commonly, the packet stream of interest is generated as the basis - of measurement. Sometimes, the adjective "synthetic" is used to - categorize Active measurement streams [Y.1731]. Accompanying - packet stream(s) may be generated to increase overall traffic - load, though the loading stream(s) may not be measured. + 1. Active methods generate packet streams. Commonly, the packet + stream of interest is generated as the basis of measurement. + Sometimes, the adjective "synthetic" is used to categorize Active + measurement streams [Y.1731]. Accompanying packet stream(s) may + be generated to increase overall traffic load, though the loading + stream(s) may not be measured. 2. The packets in the stream of interest have fields or field values (or are augmented or modified to include fields or field values) which are dedicated to measurement. Since measurement usually requires determining the corresponding packets at multiple measurement points, a sequence number is the most common information dedicated to measurement, and often combined with a timestamp. 3. The Source and Destination of the packet stream of interest are usually known a priori. 4. The characteristics of the packet stream of interest are known at the Source at least, and may be communicated to Destination as part of the method. Note that some packet characteristics will - normaly change during packet forwarding. Other changes along the - path are possible, see [I-D.morton-ippm-2330-stdform-typep]. + normally change during packet forwarding. Other changes along + the path are possible, see [I-D.morton-ippm-2330-stdform-typep]. When adding traffic to the network for measurement, Active Methods influence the quantities measured to some degree, and those performing tests should take steps to quantify the effect(s) and/or minimize such effects. 3.5. Active Metric An Active Metric incorporates one or more of the aspects of Active Methods in the metric definition. @@ -200,25 +202,25 @@ packet characteristics (Type-P) and Source and Destination IP addresses (with their implications on both stream treatment and interfaces associated with measurement points). 3.6. Passive Methods Passive measurement methods are o based solely on observations of undisturbed and unmodified packet stream of interest (in other words, the method of measurement MUST - NOT add, change, or remove fields, or change field values anywhere - along the path). + NOT add, change, or remove packets or fields, or change field + values anywhere along the path). o dependent on the existence of one or more packet streams to supply - the stream of interest + the stream of interest. o dependent on the presence of the packet stream of interest at one or more designated observation points. Some passive methods simply observe and collect information on all packets that pass Observation Point(s), while others filter the packets as a first step and only collect information on packets that match the filter criteria, and thereby narrow the stream of interest. It is common that passive methods are conducted at one or more @@ -356,21 +358,21 @@ a key dimension for Active measurement error analysis. (Comment: There is also the notion of time averages - a measurement stream may have significant effect while it is present, but the stream is only generated 0.1% of the time. On the other hand, observations alone have no effect on network performance. To keep these dimensions simple, we consider the stream effect only when it is present, but note that reactive networks defined in [RFC7312] may exhibit bias for some time beyond the life of a stream.) X-Axis: "a priori Stream Knowledge." The degree to which stream - characteristics are know a priori. There are methodological + characteristics are known a priori. There are methodological advantages of knowing the source stream characteristics, and having complete control of the stream characteristics. For example, knowing the number of packets in a stream allows more efficient operation of the measurement receiver, and so is an asset for active measurement methods. Passive methods (with no sample filter) have few clues available to anticipate what the protocol first packet observed will use or how many packets will comprise the flow, but once the standard protocol of a flow is known the possibilities narrow (for some compliant flows). Therefore this is a key dimension for Passive measurement error @@ -408,30 +410,30 @@ 1. effect on the performance of the stream of interest itself: for example, choosing a packet marking or DSCP resulting in domain treatment as a real-time stream (as opposed to default/best- effort marking. 2. effect on unmeasured streams that share the path and/or bottlenecks: for example, an extremely sparse measured stream of minimal size packets typically has little effect on other flows (and itself), while a stream designed to characterize path - capacity may effect all other flows passing through the capacity + capacity may affect all other flows passing through the capacity bottleneck (including itself). 3. effect on network conditions resulting in network adaptation: for example, a network monitoring load and congestion conditions might change routing, placing some flows to alternate paths to mitigate the congestion. We have combined 1 and 2 on the Y-axis, as examination of examples - indicates strong correlation of affects in this pair, and network + indicates strong correlation of effects in this pair, and network adaptation is not addressed. It is apparent that different methods of IP network measurement can produce different results, even when measuring the same path at the same time. The two dimensions of the graph help to understand how the results might change with the method chosen. For example, an Active Method to assess throughput adds some amount of traffic to the network which might result in lower throughput for all streams. However, a Passive Method to assess throughput can also err on the low side due to unknown limitations of the hosts providing traffic, @@ -508,21 +510,21 @@ A. This method processes a user traffic stream, B. and augments the stream of interest with frames having "fields which are dedicated to measurement". o Synthetic Loss Measurement (SLM) and Delay Measurement (DM) methods both inject dedicated measurement frames, so the "stream of interest is generated as the basis of measurement". We conclude that SLM and DM methods are Active Methods. - We also recognize the existance of alternate terminology used in OAM + We also recognize the existence of alternate terminology used in OAM at layers other than IP. Readers are encouraged to consult [RFC6374] for MPLS Loss and Delay measurement terminology, for example. 5. Security considerations When considering privacy of those involved in measurement or those whose traffic is measured, there is sensitive information communicated and observed at observation and measurement points described above. We refer the reader to the privacy considerations described in the Large Scale Measurement of Broadband Performance @@ -533,27 +535,28 @@ 6. IANA Considerations This memo makes no requests for IANA consideration. 7. Acknowledgements Thanks to Mike Ackermann for asking the right question, and for several suggestions on terminology. Brian Trammell provided key terms and references for the passive category, and suggested ways to expand the Hybrid description and types. Phil Eardley suggested some - hybrid scenaios for categorization as part of his review. Tiziano + hybrid scenarios for categorization as part of his review. Tiziano Ionta reviewed the draft and suggested the classification for the "coloring" method of measurement. Nalini Elkins identified several - areas for clarification following her review. Bill Jouris suggested - several editorial improvements. Tal Mizrahi, Joachim Fabini, Greg - Mirsky and Mike Ackermann raised many key considerations in their - WGLC reviews, based on their broad measurement experience. + areas for clarification following her review. Bill Jouris, Stenio + Fernandes, and Spencer Dawkins suggested several editorial + improvements. Tal Mizrahi, Joachim Fabini, Greg Mirsky and Mike + Ackermann raised many key considerations in their WGLC reviews, based + on their broad measurement experience. 8. References 8.1. Normative References [RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis, "Framework for IP Performance Metrics", RFC 2330, DOI 10.17487/RFC2330, May 1998, .