Terminology for Large-Scale Measurement of Broadband Performance (LMAP) Platforms
draft-eardley-lmap-terminology-00
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| Document | Type | Active Internet-Draft (individual) | |
|---|---|---|---|
| Authors | Philip Eardley , Al Morton , Marcelo Bagnulo , Trevor Burbridge | ||
| Last updated | 2013-04-12 | ||
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draft-eardley-lmap-terminology-00
Network Working Group P. Eardley
Internet-Draft BT
Intended status: Standards Track A. Morton
Expires: October 14, 2013 AT&T Labs
M. Bagnulo
UC3M
T. Burbridge
BT
April 12, 2013
Terminology for Large-Scale Measurement of Broadband Performance (LMAP)
Platforms
draft-eardley-lmap-terminology-00
Abstract
This documents defines terminology for Large Scale Measurement
Platforms.
Status of This Memo
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
3. LMAP Terminology . . . . . . . . . . . . . . . . . . . . . . 4
4. Commentary and notes . . . . . . . . . . . . . . . . . . . . 6
5. Security considerations . . . . . . . . . . . . . . . . . . . 8
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 8
8. Informative References . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 9
1. Introduction
This document defines terminology for LMAP (in Section 3). Since
'raw' terminology is reader-unfriendly, Section 2 provides an initial
idea of the terminology by explaining how LMAP works whilst using the
terms. Section 4 provides some commentary on the terminology,
including a comparison with that in [RFC2330].
Please note that defined terms are capitalized.
2. Summary
A Measurement Task is an act that yields a single Measurement Result.
An Active Measurement Task involves a Measurement Agent injecting
test packet(s) into the network destined for another Measurement
Agent and measuring some performance or reliability parameter
associated with the transfer. The generic version of the Measurement
Task is the Measurement Method; in other words the Measurement Task
is the instantiation of the Measurement Method at a specific time and
place.
For example, a Measurement Method might be the injection of a UDP
packet by one Measurement Agent destined for another Measurement
Agent, which immediately reflects the UDP packet back to the first
Measurement Agent, which measures the round trip latency. The
associated Measurement Task might be: the injection of a UDP packet
by the Measurement Agent at 138.246.23.109 destined for the
Measurement Agent at 138.145.75.32 at UTC 13:01 and 58.6 seconds on
2013-06-15, with the second Measurement Agent immediately reflecting
the UDP packet back to the source, which measures the associated
round trip latency (using a second timestamp associated with
arrival).
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A Metric is a parameter of interest that is related to the
performance and reliability of the Internet. For example, "UDP
latency". Typically the value of a Metric is assessed as simply the
average of several Measurement Results. However a Derived Metric
consists of some combination of various Measurement Results. For
example, the delay variation of a path can be assessed by subtracting
two values of one-way delay [RFC3393], or the bulk transport capacity
might be assessed by combining several different parameters as
suggested in [I-D.mathis-ippm-model-based-metrics].
How and when to perform the Measurement Task and report the
Measurement Result is defined by the Instruction, which the
Controller sends to the Measurement Agent. Whilst the Instruction
may define a single Measurement Task, more typically it defines a
series of Measurement Tasks, all based on the same Measurement Method
and carried out at regular times according to a Measurement Schedule.
The Measurement Result of the former is likely to be reported
immediately, whilst Measurement Results of the latter will be sent at
regular time intervals, as defined by the Report Schedule. The
Instruction consists of:
o The Measurement Method: typically this is defined by a reference
in a well-known registry (for example, 'how to measure UDP
latency')
o The configuration of parameters left open by the Measurement
Method (for example, the addresses of the two Measurement Agents)
o The Measurement Schedule (for example, start at 0400 UTC, repeat
every 500 ms, end at 0403 UTC)
o Any environmental constraints (for example, do not perform the
Measurement Task if there is cross-traffic)
o The above bullets effectively define a series of Measurement Tasks
o The definition of the Report. Typically the Report includes every
single Measurement Result (since the last Report), but it may
instead be a statistic (such as their average). Typically the
Report also includes other relevant information, for example an
'echo' of the Measurement Method, configuration parameters and
schedule.
o The configuration of parameters associated with the Report (for
example, the address of the Collector to which the Report is sent)
o The Report Schedule (for example, send once a day at 01:00 hours)
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The Control Protocol and Report Protocol define the delivery of the
Instruction and the Report (respectively); they consist of a Data
Model (the semantics and structure of the information, in a
particular language such as JSON or YANG) and a transport protocol
(such as HTTP or NETCONF).
3. LMAP Terminology
Active Measurement Method (Task): A type of Measurement Method (Task)
that involves two Measurement Agents, where one Measurement Agent
injects test packet(s) into the network destined for another
Measurement Agent and which involves one of the Measurement Agents
measuring some performance or reliability parameter associated with
the transfer of the packet(s).
Collector: A function that receives a Report from a Complete
Measurement Agent. Colloquially, a Collector is a physical device
that performs this function.
Complete Measurement Agent (Complete-MA): A type of Measurement Agent
that additionally includes functionality that receives an Instruction
from a Controller and reports Results to a Collector
Controller: A function that provides a Complete-MA with an
Instruction. Colloquially, a Controller is a physical device that
performs this function.
Control Protocol: The definition of how the Instruction is delivered
from a Controller to a Complete-MA; a Data Model plus a transport
protocol.
Data Model: The implementation of an Information Model in a
particular data modelling language.
Derived Metric: A Metric that is a combination of other Metrics, and/
or a combination of the same Metric measured over different parts of
the network, or at different times.
Information Model: The abstract definition of either the Instruction
or the Report; the semantics of the fields and their arrangement (the
order they appear in and any hierarchy).
Instruction: The description of Measurement Tasks to perform and the
details of the Report to send; a specific instance of the Data Model.
The Instruction is sent by a Controller to a Complete-MA.
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Measurement Agent (MA): The function that performs a Measurement
Task. Colloquially, a Measurement Agent is a physical device that
performs this function.
Measurement Method: The process for assessing the value of a Metric;
the process of measuring some performance or reliability parameter;
the generalisation of a Measurement Task.
Measurement Result: The output of a single Measurement Task (the
value obtained for the parameter of interest, or metric)
Measurement Schedule: the schedule for performing a series of
Measurement Tasks
Measurement Task: The act that yields a single Measurement Result;
the act consisting of the (single) operation of the Measurement
Method at a particular time and with all its parameters set to
specific values
Metric: The quantity related to the performance and reliability of
the Internet that we'd like to know the value of, and that is
carefully specified.
Passive Measurement Method (Task): A Measurement Method (Task) in
which a Measurement Agent observes existing traffic at a specific
measurement point, but does not inject test packet(s).
Remote Measurement Agent (Remote-MA): A type of Measurement Agent
that does not receive an Instruction from a Controller and does not
send a Report to a Collector; it may receive control messages and
test packet(s) from a Complete-MA and may reply to the Complete-MA,
as defined by the Measurement Method.
Report: The Measurement Results and other associated information (as
defined by the Instruction); a specific instance of the Data Model.
The Report is sent by a Complete-MA to a Collector
Report Protocol: The definition of how the Report is delivered from a
Complete-MA to a Collector; a Data Model plus a transport protocol.
Report Schedule: the schedule for sending a series of Reports to a
Collector.
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4. Commentary and notes
To avoid confusion the word 'Measurement' is only used as an
adjective.
It is worth explaining how the terms defined here compare with those
in [RFC2330], "Framework for IP Performance Metrics". The definition
of Metric is taken from RFC2330. The definition of Measurement
Method is (we believe) equivalent in RFC2330's terms to a measurement
methodology for a singleton metric. A set of Measurement Tasks
defined by a Measurement Schedule relates to RFC2330's concept of a
sample metric.
If a Measurement Method is used multiple times under identical or
similar conditions, it should result in a consistent value for the
Metric.
A Measurement Method may be a more specific version of another
Measurement Method. For example,
[I-D.bagnulo-ippm-new-registry-independent] defines UDP latency as a
round trip delay [RFC2681] with the packet type set to UDP.
A registry, as proposed in
[I-D.bagnulo-ippm-new-registry-independent], would be a registry of
Measurement Methods and their associated Metrics. A Passive
Measurement Method (Task) involves only one MA, which therefore must
be a Complete-MA; for example, it measures the mix of applications.
An Active Measurement Method (Task) involves another MA (typically a
Remote-MA). It is possible that some Active Measurement Methods
(Tasks) involve more than two MAs; for example, to measure 'latency
under load' test traffic may be sent between two MAs whilst a third
MA generates the load (cross-traffic). In these circumstances the
definition of Active Measurement Method (Task) may need a small
adjustment. This is for later study.
The WG makes the assumption that a Complete-MA receives Instruction
from only a single Controller at any point in time (however it may
Report to more than one Collector).
By definition a Remote-MA does not interact with a Controller or
Collector. A Remote-MA will typically respond to the test packet(s)
from the Complete-MA. For example, it may echo a UDP packet, or
measure the amount of loss of the test packets and then send the
Measurement Results to the Complete-MA.
The MA is implemented either in specialised hardware or as code on
general purpose devices like a PC, tablet or smartphone. Note that a
Remote-MA may not have specific LMAP or IPPM functionality. For
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example, to assess DNS response time a Complete-MA sends DNS requests
to a standard DNS server.
A Controller can send an Instruction for immediate action, containing
a one-off Measurement Task. This is in addition to the more typical
scenario of a series of Measurement Tasks carried out on a regular
schedule, with the Measurement Results reported periodically.
It may be sensible for an Instruction to be able to refer to more
than one Measurement Method. This is for further study.
The right set of Information Models is for further study - for
example, perhaps there should be three Information Models, with one
containing all the scheduling information. Also, note that different
fields of the Information Models may be relevant for different
Measurement Methods.
The Control Protocol defines the Data Model and so effectively
defines the Instruction. The Instruction includes: the Measurement
Method; values for the parameters that the Measurement Method leaves
open (configuration); when to perform the Measurement Tasks (the
Measurement Schedule); any environmental conditions (such as "don't
perform the Measurement Task if there is end user traffic present");
the Report Protocol, which includes its Data Model; when to send a
Report (the Report Schedule); where to send the Report (the address
of the Collector) and values for any other parameters that the Report
Protocol leaves open (configuration). This is for discussion.
Typically the Report includes every single Measurement Result, but it
may instead be a statistic (such as their average). The latter may
be useful when the bandwidth between the MA and Collector is severely
constrained and/or the full set of Measurement Results provides
little extra information.
The Report includes: the Measurement Results (or statistic based on
them); the details of the Measurement Tasks (essentially a copy of
much of the Instruction, for example the Measurement Method, the
configuration parameters and the time at which each Measurement
Result was obtained); and other relevant information known by the
Complete-MA (such as the line's speed, the version of the MA, and the
amount of cross-traffic during the measurement). Again this is very
much for discussion.
A proposal for a Control Protocol based on HTTP is currently under
development. There are already Internet drafts describing a Control
Protocol based on NETCONF and a Report Protocol based on IPFIX.
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The Broadband Forum defines a Management Server [http://
datatracker.ietf.org/liaison/1243/]: "Manages and configures a
physical device or network element. Examples include a TR-069 ACS
(Auto-Configuration Server), or an EMS (Element Management System)."
At the moment we assume that the Broadband Forum will specify this
function and so assume it is out of scope of LMAP. Such an
initialisation function seems essential for a large-scale measurement
system. There must be some automated way to associate a complete-MA
to its Controller and Collector, including authentication
credentials, to re-arrange such associations over time, and to pull
the plug on rogue MAs.
5. Security considerations
There are no security considerations needed in a memo that only
defines terminology.
6. IANA Considerations
There are no IANA considerations in this memo.
7. Acknowledgments
8. 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-00 (work in progress), January 2013.
[RFC2330] Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
"Framework for IP Performance Metrics", RFC 2330, May
1998.
[I-D.mathis-ippm-model-based-metrics]
Mathis, M. and A. Morton, "Model Based Internet
Performance Metrics", draft-mathis-ippm-model-based-
metrics-01 (work in progress), February 2013.
[RFC2681] Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
Delay Metric for IPPM", RFC 2681, September 1999.
[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation
Metric for IP Performance Metrics (IPPM)", RFC 3393,
November 2002.
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Authors' Addresses
Phil Eardley
British Telecom
Adastral Park, Martlesham Heath
IPswitch
ENGLAND
Email: philip.eardley@bt.com
Al Morton
AT&T Labs
200 Laurel Avenue South
Middletown, NJ
USA
Email: acmorton@att.com
Marcelo Bagnulo
Universidad Carlos III de Madrid
Av. Universidad 30
Leganes, Madrid 28911
SPAIN
Phone: 34 91 6249500
Email: marcelo@it.uc3m.es
URI: http://www.it.uc3m.es
Trevor Burbridge
British Telecom
Adastral Park, Martlesham Heath
IPswitch
ENGLAND
Email: trevor.burbridge@bt.com
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