One document matched: draft-ietf-lmap-framework-03.xml
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<front>
<title abbrev="LMAP Framework">A framework for large-scale measurement
platforms (LMAP)</title>
<author fullname="Philip Eardley" initials="P." surname="Eardley">
<organization abbrev="BT">British Telecom</organization>
<address>
<postal>
<street>Adastral Park, Martlesham Heath</street>
<city>Ipswich</city>
<country>ENGLAND</country>
</postal>
<email>philip.eardley@bt.com</email>
</address>
</author>
<author fullname="Al Morton" initials="A." surname="Morton">
<organization abbrev="AT&T Labs">AT&T Labs</organization>
<address>
<postal>
<street>200 Laurel Avenue South</street>
<city>Middletown, NJ</city>
<country>USA</country>
</postal>
<email>acmorton@att.com</email>
</address>
</author>
<author fullname="Marcelo Bagnulo" initials="M." surname="Bagnulo">
<organization abbrev="UC3M">Universidad Carlos III de
Madrid</organization>
<address>
<postal>
<street>Av. Universidad 30</street>
<city>Leganes</city>
<region>Madrid</region>
<code>28911</code>
<country>SPAIN</country>
</postal>
<phone>34 91 6249500</phone>
<email>marcelo@it.uc3m.es</email>
<uri>http://www.it.uc3m.es</uri>
</address>
</author>
<author fullname="Trevor Burbridge" initials="T." surname="Burbridge">
<organization abbrev="BT">British Telecom</organization>
<address>
<postal>
<street>Adastral Park, Martlesham Heath</street>
<city>Ipswich</city>
<country>ENGLAND</country>
</postal>
<email>trevor.burbridge@bt.com</email>
</address>
</author>
<author fullname="Paul Aitken" initials="P." surname="Aitken">
<organization abbrev="Cisco Systems">Cisco Systems, Inc.</organization>
<address>
<postal>
<street>96 Commercial Street</street>
<city>Edinburgh</city>
<region>Scotland</region>
<code>EH6 6LX</code>
<country>UK</country>
</postal>
<email>paitken@cisco.com</email>
</address>
</author>
<author fullname="Aamer Akhter" initials="A." surname="Akhter">
<organization abbrev="Cisco Systems">Cisco Systems, Inc.</organization>
<address>
<postal>
<street>7025 Kit Creek Road</street>
<city>RTP</city>
<region>NC</region>
<code>27709</code>
<country>USA</country>
</postal>
<email>aakhter@cisco.com</email>
</address>
</author>
<date day="21" month="January" year="2014"/>
<abstract>
<t>Measuring broadband service on a large scale requires a description
of the logical architecture and standardisation of the key protocols
that coordinate interactions between the components. The document
presents an overall framework for large-scale measurements. It also
defines terminology for LMAP (large-scale measurement platforms).</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>There is a desire to be able to coordinate the execution of broadband
measurements and the collection of measurement results across a large
scale set of diverse devices. These devices could be software based
agents on PCs, embedded agents in consumer devices (e.g. blu-ray
players), service provider controlled devices such as set-top players
and home gateways, or simply dedicated probes. It is expected that such
a system could easily comprise 100k devices. Such a scale presents
unique problems in coordination, execution and measurement result
collection. Several use cases have been proposed for large- scale
measurements including:</t>
<t><list style="symbols">
<t>Operators: to help plan their network and identify faults</t>
<t>Regulators: to benchmark several network operators and support
public policy development</t>
</list>Further details of the use cases can be found at <xref
target="I-D.ietf-lmap-use-cases"/>. The LMAP framework should be useful
for these, as well as other use cases that the LMAP WG doesn't
concentrate on, such as to help end users run diagnostic checks like a
network speed test.</t>
<t>The LMAP framework has four basic elements: Measurement Agents,
Measurement Peers, Controllers and Collectors.</t>
<t>Measurement Agents (MAs) perform Measurement Tasks, perhaps in
conjunction with Measurement Peers. They are pieces of code that can be
executed in specialized hardware (hardware probe) or on a
general-purpose device (like a PC or mobile phone). A device with a
Measurement Agent may have multiple interfaces (WiFi, Ethernet, DSL,
fibre, etc.) and the Measurement Tasks may specify any one of these.
Measurement Tasks may be Active (the MA or Measurement Peer generates
Active Measurement Traffic), Passive (the MA observes user traffic), or
some hybrid form of the two. For Active Measurement Tasks, the MA (or
Measurement Peer) generates Active Measurement Traffic and measures some
metric associated with its transfer over the path to (or from) a
Measurement Peer. For example, one Active Measurement Task could be to
measure the UDP latency between the MA and a given Measurement Peer. MAs
may also conduct Passive Measurement Tasks through the observation of
traffic. The Measurement Tasks themselves may be on IPv4, IPv6, and on
various services (DNS, HTTP, XMPP, FTP, VoIP, etc.).</t>
<t>The Controller manages one or more MAs by instructing it which
Measurement Tasks it should perform and when. For example it may
instruct a MA at a home gateway: “Measure the ‘UDP
latency’ with the Measurement Peer mp.example.org; repeat every
hour at xx.05”. The Controller also manages a MA by instructing it
how to report the Measurement Results, for example: “Report
results once a day in a batch at 4am”. We refer to these as the
Measurement Schedule and Report Schedule.</t>
<t>The Collector accepts Reports from the MAs with the Results from
their Measurement Tasks. Therefore the MA is a device that gets
Instructions from the Controller, initiates the Measurement Tasks, and
reports to the Collector.</t>
<t>There are additional elements that are part of a measurement system,
but that are out of the scope for LMAP. We provide a detailed discussion
of all the elements in the rest of the document.</t>
<t>The desirable features for a large-scale measurement systems we are
designing for are:</t>
<t><list style="symbols">
<t>Standardised - in terms of the Measurement Tasks that they
perform, the components, the data models and protocols for
transferring information between the components. Amongst other
things, standardisation enables meaningful comparisons of
measurements made of the same metric at different times and places,
and enables the operator of a measurement system to buy the various
components from different vendors. Today's systems are proprietary
in some or all of these aspects.</t>
<t>Large-scale - <xref target="I-D.ietf-lmap-use-cases"/> envisages
Measurement Agents in every home gateway and edge device such as
set-top-boxes and tablet computers. It is expected that a
measurement system could easily encompass a few hundred thousand
Measurement Agents. Existing systems have up to a few thousand MAs
(without judging how much further they could scale).</t>
<t>Diversity - a measurement system should handle different types of
Measurement Agent - for example Measurement Agents may come from
different vendors, be in wired and wireless networks and be on
devices with IPv4 or IPv6 addresses.</t>
</list></t>
</section>
<section title="Outline of an LMAP-based measurement system">
<t>Figure 1 shows the main components of a measurement system, and the
interactions of those components. Some of the components are outside the
scope of LMAP. In this section we provide an overview of the whole
measurement system and we introduce the main terms needed for the LMAP
framework. The new terms are capitalized. In the next section we provide
a terminology section with a compilation of all the LMAP terms and their
definition. The subsequent sections study the LMAP components in more
detail.</t>
<t>A Measurement Task measures some performance or reliability Metric of
interest. An Active Measurement Task involves either a Measurement Agent
(MA) injecting Active Measurement Traffic into the network destined for
a Measurement Peer, and/or a Measurement Peer sending Active Measurement
Traffic to a MA; one of them measures some parameter associated with the
transfer of the packet(s). A Passive Measurement Task involves only a
MA, which simply observes existing traffic - for example, it could
simply count bytes or it might calculate the average loss for a
particular flow.</t>
<t>It is very useful to standardise Measurement Methods (a Measurement
Method is a generalisation of a Measurement Task), so that it is
meaningful to compare measurements of the same Metric made at different
times and places. It is also useful to define a registry for
commonly-used Metrics <xref
target="I-D.bagnulo-ippm-new-registry-independent"/> so that a
Measurement Method can be referred to simply by its identifier in the
registry. The Measurement Methods and registry will hopefully be
referenced by other standards organisations.</t>
<t>In order for a Measurement Agent and a Measurement Peer to execute an
Active Measurement Task, they exchange Active Measurement Traffic. The
protocols used for the Active Measurement Traffic is out of the scope of
the LMAP WG and falls within the scope of other IETF WGs such as
IPPM.</t>
<t>For Measurement Results to be truly comparable, as might be required
by a regulator, not only do the same Measurement Methods need to be used
but also the set of Measurement Tasks should follow a similar
Measurement Schedule and be of similar number. The details of such a
characterisation plan are beyond the scope of work in IETF although
certainly facilitated by IETF's work.</t>
<t>The next components we consider are the Measurement Agent (MA),
Controller and Collector. The main work of the LMAP working group is to
define the Control Protocol between the Controller and MA, and the
Report Protocol between the MA and Collector. Section 4 onwards
considers the LMAP components in more detail; here we introduce
them.</t>
<t>The Controller manages a MA by instructing it which Measurement Tasks
it should perform and when. For example it may instruct a MA at a home
gateway: “Run the ‘download speed test’ with the
Measurement Peer at the end user's first IP point in the network; if the
end user is active then delay the test and re-try 1 minute later, with
up to 3 re-tries; repeat every hour at xx.05 + Unif[0,180]
seconds”. The Controller also manages a MA by instructing it how
to report the Measurement Results, for example: “Report results
once a day in a batch at 4am + Unif[0,180] seconds; if the end user is
active then delay the report 5 minutes”. These are called the
Measurement and Report Schedule. As well as periodic Measurement Tasks,
a Controller can initiate a one-off (non-recurring) Measurement Task
("Do measurement now", "Report as soon as possible").</t>
<t>The Collector accepts a Report from a MA with the results from its
Measurement Tasks. It may also do some post-processing on the results,
for instance to eliminate outliers, as they can severely impact the
aggregated results.</t>
<t>Finally we introduce several components that are out of scope of the
LMAP WG and will be provided through existing protocols or applications.
They affect how the measurement system uses the Measurement Results and
how it decides what set of Measurement Tasks to perform.</t>
<t>The MA needs to be bootstrapped with initial details about its
Controller, including authentication credentials. The LMAP WG considers
the bootstrap process, since it affects the Information Model. However,
it does not define a bootstrap protocol, since it is likely to be
technology specific and could be defined by the Broadband Forum,
CableLabs or IEEE depending on the device. Possible protocols are SNMP,
NETCONF or (for Home Gateways) CPE WAN Management Protocol (CWMP) from
the Auto Configuration Server (ACS) (as specified in TR-069).</t>
<t>A Subscriber parameter database contains information about the line,
such as the customer's broadband contract (perhaps 2, 40 or 80Mb/s), the
line technology (DSL or fibre), the time zone where the MA is located,
and the type of home gateway and MA. These parameters are already
gathered and stored by existing operations systems. They may affect the
choice of what Measurement Tasks to run and how to interpret the
Measurement Results. For example, a download test suitable for a line
with an 80Mb/s contract may overwhelm a 2Mb/s line.</t>
<t>A results repository records all Measurement Results in an equivalent
form, for example an SQL database, so that they can easily be accessed
by the data analysis tools. The data analysis tools also need to
understand the Subscriber's service information, for example the
broadband contract.</t>
<t>The data analysis tools receive the results from the Collector or via
the Results repository. They might visualise the data or identify which
component or link is likely to be the cause of a fault or degradation.
This information could help the Controller decide what follow-up
Measurement Task to perform in order to diagnose a fault.</t>
<t>The operator's OAM (Operations, Administration, and Maintenance) uses
the results from the tools.</t>
<t/>
<figure>
<artwork><![CDATA[ ^
|
Active IPPM
+---------------+ Measurement +-------------+ Scope
+------->| Measurement |<------------>| Measurement | v
| | Agent | Traffic | Peer | ^
| +---------------+ +-------------+ |
| ^ | |
| Instruction | | Report |
| | +-----------------+ |
| | | |
| | v LMAP
| +------------+ +------------+ Scope
| | Controller | | Collector | |
| +------------+ +------------+ v
| ^ ^ | ^
| | | | |
| | +----------+ | |
| | | v |
+------------+ +----------+ +--------+ +----------+ |
|Bootstrapper| |Subscriber|--->| data |<---|repository| Out
+------------+ |parameter | |analysis| +----------+ of
|database | | tools | Scope
+----------+ +--------+ |
|
v
Figure 1: Schematic of main elements of an LMAP-based
measurement system
(showing the elements in and out of the scope of the LMAP WG)
]]></artwork>
</figure>
</section>
<section title="Terminology">
<t>This section defines terminology for LMAP. Please note that defined
terms are capitalized.</t>
<t>Active Measurement Method (Task): A type of Measurement Method (Task)
that involves a Measurement Agent and a Measurement Peer (or possibly
Peers), where either the Measurement Agent or the Measurement Peer
injects Active Measurement Traffic into the network destined for the
other, and which involves one of them measuring some performance or
reliability parameter associated with the transfer of the traffic.</t>
<t>Active Measurement Traffic: the packet(s) generated by the
Measurement Agent and/or the Measurement Peer, as part of an Active
Measurement Task.</t>
<t>Bootstrap: A process that initialises a Measurement Agent with the
information necessary to be integrated into a measurement system.</t>
<t>Capabilities: Information about the Measurement Methods that the MA
can perform and the device hosting the MA, for example its interface
type and speed and its IP address.</t>
<t>Channel: an Instruction Channel, Report Channel or MA-to-Controller
Channel</t>
<t>Collector: A function that receives a Report from a Measurement
Agent.</t>
<t>Composite 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.</t>
<t>Controller: A function that provides a Measurement Agent with
Instruction(s).</t>
<t>Control Channel: a communications channel between a Controller and a
MA, which is defined by a specific Controller, MA and associated
security, and over which Instructions are sent.</t>
<t>Control Protocol: The protocol delivering Instruction(s) from a
Controller to a Measurement Agent. It also delivers Failure Information
and Capabilities Information from the Measurement Agent to the
Controller.</t>
<t>Cycle-ID: (optional) A tag that is sent by the Controller in an
Instruction and echoed by the MA in its Report. The same Cycle-ID is
used by several MAs that use the same Measurement Method with the same
Input Parameters. Hence the Cycle-ID allows the Collector to easily
identify Measurement Results that should be comparable.</t>
<t>Data Model: The implementation of an Information Model in a
particular data modelling language.</t>
<t>Environmental Constraint: A parameter that is measured as part of the
Measurement Task, its value determining whether the rest of the
Measurement Task proceeds.</t>
<t>Failure Information: Information about the MA's failure to action or
execute an Instruction, whether concerning Measurement Tasks or
Reporting.</t>
<t>Group-ID: (optional) An identifier of a group of MAs.</t>
<t>Information Model: The protocol-neutral definition of the semantics
of the Instructions, the Report, the status of the different elements of
the measurement system as well of the events in the system.</t>
<t>Input Parameter: A parameter whose value is left open by the
Measurement Method and is set to a specific value in a Measurement Task.
Altering the value of an Input Parameter does not change the fundamental
nature of the Measurement Method.</t>
<t>Instruction: The description of Measurement Tasks to perform and the
details of the Report to send. The Instruction is sent by a Controller
to a Measurement Agent.</t>
<t>MA-to-Controller Channel: a communications channel between a MA and a
Controller, which is defined by a specific Controller, MA and associated
security, and over which Capabilities and Failure Information is
sent.</t>
<t>Measurement Agent (MA): The function that receives Instructions from
a Controller, performs Measurement Tasks (perhaps in concert with a
Measurement Peer) and reports Measurement Results to a Collector.</t>
<t>Measurement Agent Identifier (MA-ID): a UUID <xref
target="RFC4122"/>, which is configured as part of the Bootstrapping and
included in a Capabilities message, Failure Information message and
optionally in a Report.</t>
<t>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.</t>
<t>Measurement Peer: The function that receives control messages and
Active Measurement Traffic from a Measurement Agent and may reply to the
Measurement Agent as defined by the Active Measurement Method.</t>
<t>Measurement Result: The output of a single Measurement Task (the
value obtained for the parameter of interest or Metric).</t>
<t>Measurement Schedule: the schedule for performing Measurement
Tasks.</t>
<t>Measurement Suppression: a type of Instruction that temporarily stops
(suppresses) Active Measurement Tasks.</t>
<t>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.</t>
<t>Metric: The quantity related to the performance and reliability of
the network that we'd like to know the value of, and that is carefully
specified.</t>
<t>Passive Measurement Method (Task): A Measurement Method (Task) in
which a Measurement Agent observes existing traffic but does not inject
Active Measurement Traffic.</t>
<t>Report: The Measurement Results and other associated information (as
defined by the Instruction). The Report is sent by a Measurement Agent
to a Collector.</t>
<t>Report Channel: a communications channel between a MA and a
Collector, which is defined by a specific MA, Collector, Report Schedule
and associated security, and over which Reports are sent.</t>
<t>Report Protocol: The protocol delivering Report(s) from a Measurement
Agent to a Collector.</t>
<t>Report Schedule: the schedule for sending one or more Reports to a
Collector.</t>
<t>Subscriber: An entity (associated with one or more users) that is
engaged in a subscription with a service provider. The Subscriber is
allowed to subscribe and un-subscribe services, and to register a user
or a list of users authorized to enjoy these services. <xref
target="Q1741"/> Both the Subscriber and service provider are allowed to
set the limits relative to the use that associated users make of
subscribed services.</t>
<t/>
</section>
<section title="Constraints">
<t>The LMAP framework makes some important assumptions, which constrain
the scope of the work to be done.</t>
<section title="Measurement system is under the direction of a single organisation">
<t>In the LMAP framework, the measurement system is under the
direction of a single organisation that is responsible both for the
data and the quality of experience delivered to its users. Clear
responsibility is critical given that a misbehaving large-scale
measurement system could potentially harm user experience, user
privacy and network security.</t>
<t>However, the components of an LMAP measurement system can be
deployed in administrative domains that are not owned by the measuring
organisation. Thus, the system of functions deployed by a single
organisation constitutes a single LMAP domain which may span ownership
or other administrative boundaries.</t>
</section>
<section title="Each MA may only have a single Controller at any point in time">
<t>A MA is instructed by one Controller and is in one measurement
system. The constraint avoids different Controllers giving a MA
conflicting instructions and so means that the MA does not have to
manage contention between multiple Measurement (or Report) Schedules.
This simplifies the design of MAs (critical for a large-scale
infrastructure) and allows a Measurement Schedule to be tested on
specific types of MA before deployment to ensure that the end user
experience is not impacted (due to CPU, memory or broadband-product
constraints).</t>
<t>An operator may have several Controllers, perhaps with a Controller
for different types of MA (home gateways, tablets) or location
(Ipswich, Edinburgh).</t>
</section>
</section>
<section title="LMAP Protocol Model">
<t>A protocol model <xref target="RFC4101"/> presents an architectural
model for how the protocol operates and needs to answer three basic
questions:</t>
<t><list style="numbers">
<t>What problem is the protocol trying to achieve?</t>
<t>What messages are being transmitted and what do they mean?</t>
<t>What are the important, but unobvious, features of the
protocol?</t>
</list></t>
<t>An LMAP system goes through the following phases:</t>
<t><list style="symbols">
<t>a bootstrapping process before the MA can take part in the other
three phases</t>
<t>a Control Protocol, which delivers an Instruction from a
Controller to a MA, detailing what Measurement Tasks the MA should
perform and when, and how it should report the Measurement
Results</t>
<t>the actual Measurement Tasks are performed. An Active Measurement
Task involves sending Active Measurement Traffic between the
Measurement Agent and a Measurement Peer, whilst a Passive
Measurement Task involves (only) the Measurement Agent observing
existing user traffic. The LMAP WG does not define Measurement
Methods, however the IPPM WG does.</t>
<t>a Report Protocol, which delivers a Report from the MA to a
Collector. The Report contains the Measurement Results.</t>
</list></t>
<t>In the diagrams the following convention is used:</t>
<t><list style="symbols">
<t>(optional): indicated by round brackets</t>
<t>[potentially repeated]: indicated by square brackets</t>
</list></t>
<t>The protocol model is closely related to the Information Model <xref
target="I-D.burbridge-lmap-information-model"/>, which is the abstract
definition of the information carried by the protocol model. The purpose
of both is to provide a protocol and device independent view, which can
be implemented via specific protocols. The LMAP WG will define a
specific Control Protocol and Report Protocol, but others could be
defined by other standards bodies or be proprietary. However it is
important that they all implement the same Information Model and
protocol model, in order to ease the definition, operation and
interoperability of large-scale measurement systems.</t>
<t>The diagrams show the various LMAP messages and Section 5.5 considers
how they could be mapped onto an underlying transport protocol.</t>
<section title="Bootstrapping process">
<t>The primary purpose of bootstrapping is to enable the MA and
Controller to be integrated into a measurement system. In order to do
that, the MA needs to retrieve information about itself (like its
identity in the measurement system), about the Controller, as well as
security information (such as certificates and credentials).<figure>
<artwork><![CDATA[ +--------------+
| Measurement |
| Agent |
+--------------+
(initial Controller details:
address or FQDN, ->
security credentials)
+-----------------+
| initial |
| Controller |
+-----------------+
<- (register)
Controller details:
address or FQDN, ->
security credentials
+-----------------+
| |
| Controller |
+-----------------+
<- register
MA-ID, (Group-ID), ->
Control Channel,
(Suppression Channel),
MA-to-Controller Channel
]]></artwork>
</figure></t>
<t/>
<t>The MA knows how to contact a Controller through some device
/access specific mechanism. For example, this could be in the
firmware, downloaded, manually configured or via a protocol like
TR-069. The Controller could either be the one that will send it
Instructions or else an initial Controller (whose details may be
statically configured). The role of an initial Controller is simply to
inform the MA how to contact its actual Controller, for example its
FQDN (Fully Qualified Domain Name) <xref target="RFC1035"/>.</t>
<t>The MA learns its identifier (MA-ID). It may also be told a
Group-ID and whether to include the MA-ID as well as the Group-ID in
its Reports. A Group-ID would be shared by several MAs and could be
useful for privacy reasons, for instance to hinder tracking of a
mobile device.</t>
<t>The MA is also told about the Control Channel over which it will
receive Instructions from the Controller, in particular the associated
security information, for example to enable the MA to decrypt the
Instruction. Optionally any Suppression messages can be sent over a
different Channel. The MA is also informed about the MA-to-Controller
Channel, over which the MA can tell the Controller about its
Capabilities and any Failure Information. This consists of the address
of the Controller, for instance its URL, and security details for
MA-to-Controller messages.</t>
<t/>
<t>The MA may tell the Controller its Capabilities, in particular the
Measurement Methods it can perform.</t>
<t>If the device with the MA re-boots, then the MA needs to
re-register, so that it can receive a new Instruction. To avoid a
"mass calling event" after a widespread power restoration affecting
many MAs, it is sensible for an MA to pause for a random delay
(perhaps in the range of one minute or so) before re-registering.</t>
<t>Whilst the LMAP WG considers the bootstrapping process, it is out
of scope to define a bootstrap mechanism, as it depends on the type of
device and access.</t>
<t/>
</section>
<section title="Control Protocol">
<t>The primary purpose of the Control Protocol is to allow the
Controller to configure a Measurement Agent with an Instruction about
what Measurement Tasks to do, when to do them, and how to report the
Measurement Results. The Measurement Agent then acts on the
Instruction autonomously.</t>
<t><figure>
<artwork><![CDATA[+-----------------+ +-------------+
| | | Measurement |
| Controller |===================================| Agent |
+-----------------+ +-------------+
(Capabilities request) ->
<- Capabilities
ACK ->
Instruction:
[(Measurement Task (Input Parameters)), ->
(Measurement Schedule),
(Report Channel(s))]
<- ACK
<- Failure Information:
[reason]
ACK ->
]]></artwork>
</figure></t>
<t>The Controller needs to know the Capabilities of the MA, and in
particular what Measurement Methods it supports, so that it can
correctly instruct the MA. It is possible that the Controller knows
the MA's Capabilities via some mechanism beyond the scope of LMAP,
such as a device-specific protocol. In LMAP, the MA can inform the
Controller about its Capabilities. This message could be sent in
several circumstances: when the MA first communicates with a
Controller; when the MA becomes capable of a new Measurement Method;
when requested by the Controller (for example, if the Controller
forgets what the MA can do or otherwise wants to resynchronize what it
knows about the MA). Note that Capabilities do not include dynamic
information like the MA's currently unused CPU, memory or battery
life.</t>
<t>A single Instruction message contains one, two, three or all four
of the following elements:</t>
<t><list style="symbols">
<t>configuration of all the Measurement Tasks, each of which
needs:<list style="symbols">
<t>the Measurement Method, specified as a URN to a registry
entry. The registry could be defined by the IETF <xref
target="I-D.bagnulo-ippm-new-registry-independent"/>, locally
by the operator of the measurement system or perhaps by
another standards organisation.</t>
<t>any Input Parameters that need to be set for the
Measurement Method, such as the address of the Measurement
Peer</t>
<t>if the device with the MA has multiple interfaces, then the
interface to use</t>
<t>optionally, a Cycle-ID</t>
<t>a name for this Measurement Task configuration</t>
</list></t>
<t>configuration of all the Report Channels, each of which
needs:<list style="symbols">
<t>the address of the Collector, for instance its URL</t>
<t>the timing of when to report Measurement Results, for
example every hour or immediately</t>
<t>security for sending the Report, for example the X.509
certificate</t>
<t>a name for this Report Channel</t>
</list></t>
<t>the set of periodic Measurement Schedules, each of which
needs:<list style="symbols">
<t>the name of one or several Measurement Task
configurations</t>
<t>the timing of when the Measurement Tasks are to be
performed. Possible types of timing are periodic and
calendar-based periodic</t>
<t>the name of a Report Channel or Channels on which to report
the Measurement Results</t>
<t>a name for this Measurement Schedule</t>
</list></t>
<t>the set of one-off Measurement Schedules, each of which needs
the same items as for a periodic Measurement Schedule, except that
the possible types of timing are one-off immediate and one-off at
a future time.</t>
</list></t>
<t>A single Instruction message contains one, two, three or all four
of the above elements. This allows the different elements to be
updated independently at different times and intervals, for example it
is likely that the periodic Measurement Schedule will be updated more
often than the other elements.</t>
<t>Note that an Instruction message replaces (rather than adds to)
those elements that it includes. For example, if the message includes
(only) a periodic Measurement Schedule, then that replaces the old
periodic Measurement Schedule but does not alter the configuration of
the Measurement Tasks and Report Channels.</t>
<t>Periodic Measurement Schedules contain the name of one or several
Measurement Task configurations that are to be carried out on a
recurring basis, whilst one-off Measurement Schedules contain
non-recurring Measurement Tasks. One-off and periodic Measurement
Schedules are kept separate so that the Controller can instruct the MA
to perform an ad hoc Measurement Task (for instance to help isolate a
fault) without having to re-notify the MA about the periodic
Measurement Schedule.</t>
<t>Note that the Instruction informs the MA; the Control Protocol does
not allow the MA to negotiate, as this would add complexity to the MA,
Controller and Control Protocol for little benefit.</t>
<t>The MA can inform the Controller about a Failure. There are two
broad categories of failure: (1) the MA cannot action the Instruction
(for example, it doesn't include a parameter that is mandatory for the
requested Measurement Method; or it is missing details of the target
Collector). (2) the MA cannot execute the Measurement Task or deliver
the Report (for example, the MA unexpectedly has no spare CPU cycles;
or the Collector is not responding). Note that it is not considered a
failure if a Measurement Task (correctly) doesn't start; for example
if the MA detects cross-traffic, this is reported to the Collector in
the normal manner. Note also that the MA does not inform the
Controller about normal operation of its Measurement Tasks and
Reports.</t>
<t>In the Figure, ACK means that the message has been delivered
successfully.</t>
<t/>
<t>Finally, note that the MA doesn't do a 'safety check' with the
Controller (that it should still continue with the requested
Measurement Tasks) - nor does it inform the Controller about
Measurement Tasks starting and stopping. It simply carries out the
Measurement Tasks as instructed, unless it gets an updated
Instruction.</t>
<t>The LMAP WG will define a Control Protocol and its associated Data
Model that implements the Protocol & Information Model. This may
be a simple instruction-response protocol.</t>
<section title="Measurement Suppression">
<t>Measurement Suppression is used if the measurement system wants
to eliminate inessential traffic, because there is some unexpected
network issue for example. The Controller instructs the MA to
temporarily not begin new Active Measurement Tasks. By default,
suppression applies to all Active Measurement Tasks, starts
immediately and continues until an un-suppress message is received.
Optionally the suppress message may include:</t>
<t><list style="symbols">
<t>a set of Active Measurement Tasks to suppress; the others are
not suppressed. For example, a particular Measurement Task may
be overloading a Measurement Peer.</t>
<t>a set of Measurement Schedules to suppress; the others are
not suppressed. For example, suppose the measurement system has
defined two Schedules, one with the most critical Active
Measurement Tasks and the other with less critical ones that
create a lot of traffic, then it may only want to suppress the
second.</t>
<t>a start time, at which suppression begins</t>
<t>an end time, at which suppression ends.</t>
</list></t>
<t>It is not standardised what the impact of Suppression is on:</t>
<t><list style="symbols">
<t>Passive Measurement Tasks; since they do not create any
Active Measurement Traffic there is no need to suppress them,
however it may be simpler for an implementation to do so</t>
<t>on-going Active Measurement Tasks; see Section 5.3</t>
</list>Note that Suppression is not intended to permanently stop a
Measurement Task (instead, the Controller should send a new
Measurement Schedule), nor to permanently disable a MA (instead,
some kind of management action is suggested).</t>
<t/>
<t/>
<figure>
<artwork><![CDATA[+-----------------+ +-------------+
| | | Measurement |
| Controller |===================================| Agent |
+-----------------+ +-------------+
Suppress:
[(Measurement Task), ->
(Measurement Schedule),
start time, end time]
<- ACK
Un-suppress ->
<- ACK
]]></artwork>
</figure>
</section>
</section>
<section title="Starting and stopping Measurement Tasks">
<t>The LMAP WG is neutral to what the actual Measurement Task is. The
WG does not define a generic start and stop process, since the correct
approach depend on the particular Measurement Task; the details are
defined as part of each Measurement Method, and hence potentially by
the IPPM WG. This section provides some general hints.</t>
<t>Once the MA gets its Measurement and Report Schedules from its
Controller then it acts autonomously, in terms of operation of the
Measurement Tasks and reporting of the result. One implication is that
the MA initiates Measurement Tasks. As an example, for the common case
where the MA is on a home gateway, the MA initiates a ‘download
speed test’ by asking a Measurement Peer to send the file.</t>
<t/>
<t>Many Active Measurement Tasks begin with a pre-check before the
test traffic is sent. Action could include:</t>
<t><list style="symbols">
<t>the MA checking that there is no cross-traffic; in other words,
a check that the user isn’t already sending traffic;</t>
<t>the MA checking with the Measurement Peer that it can handle a
new Measurement Task (in case the Measurement Peer is already
handling many Measurement Tasks with other MAs);</t>
<t>the first part of the Measurement Task consisting of traffic
that probes the path to make sure it isn’t overloaded.</t>
</list>It is possible that similar checks continue during the
Measurement Task, especially one that is long-running and/or creates a
lot of Active Measurement Traffic, which may be abandoned whilst
in-progress. A Measurement Task could also be abandoned in response to
a "suppress" message (see Section 5.2.1). Action could include:</t>
<t><list style="symbols">
<t>For ‘upload’ tests, the MA not sending traffic</t>
<t>For ‘download’ tests, the MA closing the TCP
connection or sending a TWAMP Stop control message <xref
target="RFC5357"/>.</t>
</list></t>
<t>The Controller may want a MA to run the same Measurement Task
indefinitely (for example, "run the 'upload speed' Measurement Task
once an hour until further notice"). To avoid the MA generating
traffic forever after a Controller has permanently failed, it is
suggested that the Measurement Schedule includes a time limit ("run
the 'upload speed' Measurement Task once an hour for the next 30
days") and that the Measurement Schedule is updated regularly (say,
every 10 days).</t>
<t>{Comment: It is possible that the set of measurement schedules
implies overlapping Measurement Tasks. It is not clear the best thing
to do. Our current suggestion is to leave this to the protocol
document.}</t>
</section>
<section title="Report Protocol">
<t>The primary purpose of the Report Protocol is to allow a
Measurement Agent to report its Measurement Results to a Collector,
and the context in which they were obtained.</t>
<t><figure>
<artwork><![CDATA[+-----------------+ +-------------+
| | | Measurement |
| Collector |===================================| Agent |
+-----------------+ +-------------+
<- Report:
[MA-ID &/or Group-ID,
Measurement Results,
details of Measurement Task]
ACK ->
]]></artwork>
</figure></t>
<t>The Report contains:<list style="symbols">
<t>the MA-ID or a Group-ID (to anonymise results)</t>
<t>the actual Measurement Results, including the time they were
measured</t>
<t>the details of the Measurement Task (to avoid the Collector
having to ask the Controller for this information later)</t>
</list></t>
<t>The MA sends Reports as defined by the Report Channel in the
Controller's Instruction. It is possible that the Instruction tells
the MA to report the same Results to more than one Collector, or to
report a different subset of Results to different Collectors. It is
also possible that a Measurement Task may create two (or more)
Measurement Results, which could be reported differently (for example,
one Result could be reported periodically, whilst the second Result
could be an alarm that is created as soon as the measured value of the
Metric crosses a threshold and that is reported immediately).</t>
<t>Optionally, a Report is not sent when there are no Measurement
Results.</t>
<t>In the initial LMAP Information Model and Report Protocol, for
simplicity we assume that all Measurement Results are reported as-is,
but allow extensibility so that a measurement system (or perhaps a
second phase of LMAP) could allow a MA to pre-process Measurement
Results before it reports them. Potential examples of pre-processing
by the MA are:</t>
<t><list style="symbols">
<t>labelling, or perhaps not including, Measurement Results
impacted by, for instance, cross-traffic or the Measurement Peer
being busy</t>
<t>not reporting the Measurement Results if the MA believes that
they are invalid</t>
<t>detailing when suppression started and ended</t>
<t>filtering outlier Results</t>
<t>calculating some statistic like average (beyond that defined by
the Measurement Task itself)</t>
</list></t>
<t>The measurement system may define what happens if a Collector
unexpectedly does not hear from a MA, for example the Controller could
send a fresh Report Schedule to the MA.</t>
<t>The LMAP WG will define a Report Protocol and its associated Data
Model that implements the Information Model and protocol model. This
may be a simple instruction-response protocol.</t>
</section>
<section title="Operation of LMAP over the underlying transport protocol">
<t>The above sections have described LMAP's protocol model. The LMAP
working group will also specify how it operates over an existing
protocol, to be selected, for example REST-style HTTP(S). It is also
possible that a different choice is made for the Control and Report
Protocols, for example NETCONF-YANG and IPFIX respectively. It is even
possible that a different choice could be made for Suppression and for
other Instruction messages.</t>
<t>For the Control Protocol, the underlying transport protocol could
be:</t>
<t><list style="symbols">
<t>a 'push' protocol (that is, from the Controller to the MA)</t>
<t>a multicast protocol (from the Controller to a group of
MAs)</t>
<t>a 'pull' protocol. The MA periodically checks with Controller
if the Instruction has changed and pulls a new Instruction if
necessary. A pull protocol seems attractive for a MA behind a NAT
(as is typical for a MA on an end-user's device), so that it can
initiate the communications. A pull mechanism is likely to require
the MA to be configured with how frequently it should check in
with the Controller, and perhaps what it should do if the
Controller is unreachable after a certain number of attempts.</t>
<t>a hybrid protocol. In addition to a pull protocol, the
Controller can also push an alert to the MA that it should
immediately pull a new Instruction.</t>
</list>For the Report Protocol, the underlying transport protocol
could be:</t>
<t><list style="symbols">
<t>a 'push' protocol (that is, from the MA to the Collector)</t>
<t>perhaps supplemented by the ability for the Collector to 'pull'
Measurement Results from a MA.</t>
</list></t>
</section>
<section title="Items beyond the scope of the LMAP Protocol Model">
<t>There are several potential interactions between LMAP elements that
are out of scope of definition by the LMAP WG:</t>
<t><list style="numbers">
<t>It does not define a coordination process between MAs. Whilst a
measurement system may define coordinated Measurement Schedules
across its various MAs, there is no direct coordination between
MAs.</t>
<t>It does not define interactions between the Collector and
Controller. It is quite likely that there will be such
interactions, optionally intermediated by the data analysis tools.
For example if there is an "interesting" Measurement Result then
the measurement system may want to trigger extra Measurement Tasks
that explore the potential cause in more detail.</t>
<t>It does not define coordination between different measurement
systems. For example, it does not define the interaction of a MA
in one measurement system with a Controller or Collector in a
different measurement system. Whilst it is likely that the Control
and Report Protocols could be re-used or adapted for this
scenario, any form of coordination between different organisations
involves difficult commercial and technical issues and so, given
the novelty of large-scale measurement efforts, any form of
inter-organisation coordination is outside the scope of the LMAP
WG. Note that a single MA is instructed by a single Controller and
is only in one measurement system.<list style="symbols">
<t>An interesting scenario is where a home contains two
independent MAs, for example one controlled by a regulator and
one controlled by an ISP. Then the Active Measurement Traffic
of one MA is treated by the other MA just like any other user
traffic.</t>
</list></t>
<t>It does not consider how to prevent a malicious party "gaming
the system". For example, where a regulator is running a
measurement system in order to benchmark operators, a malicious
operator could try to identify the broadband lines that the
regulator was measuring and prioritise that traffic. It is assumed
this is a policy issue and would be dealt with through a code of
conduct for instance.</t>
<t>It does not define how to analyse Measurement Results,
including how to interpret missing Results.</t>
<t>It does not specifically define a enduser-controlled
measurement system, see sub-section 5.6.1.</t>
</list></t>
<section title="Enduser-controlled measurement system">
<t>The WG concentrates on the cases where an ISP or a regulator runs
the measurement system. However, we expect that LMAP functionality
will also be used in the context of an enduser-controlled
measurement system. There are at least two ways this could happen
(they have various pros and cons):</t>
<t><list style="numbers">
<t>an enduser could somehow request the ISP- (or regulator-) run
measurement system to test his/her line. The ISP (or regulator)
Controller would then send an Instruction to the MA in the usual
LMAP way. Note that a user can’t directly initiate a
Measurement Task on an ISP- (or regulator-) controlled MA.</t>
<t>an enduser could deploy their own measurement system, with
their own MA, Controller and Collector. For example, the user
could implement all three functions onto the same enduser-owned
end device, perhaps by downloading the functions from the ISP or
regulator. Then the LMAP Control and Report Protocols do not
need to be used, but using LMAP's Information Model would still
be beneficial. The Measurement Peer could be in the home gateway
or outside the home network; in the latter case the Measurement
Peer is highly likely to be run by a different organisation,
which raises extra privacy considerations.</t>
</list></t>
<t>In both cases there will be some way for the user to initiate the
Measurement Task(s). The mechanism is out-of-scope of the LMAP WG,
but could include the user clicking a button on a GUI or sending a
text message. Presumably the user will also be able to see the
Measurement Results, perhaps summarised on a webpage. It is
suggested that these interfaces conform to the LMAP guidance on the
privacy in Section 8.</t>
<t/>
</section>
</section>
</section>
<section title="Deployment considerations">
<t/>
<section title="Controller">
<t>The Controller should understand both the MA's LMAP Capabilities
(for instance what Measurement Methods it can perform) and about the
MA's other capabilities like processing power and memory. This allows
the Controller to make sure that the Measurement Schedule of
Measurement Tasks and the Reporting Schedule are sensible for each MA
that it Instructs.</t>
<t>An Instruction is likely to include several Measurement Tasks.
Typically these run at different times, but it is also possible for
them to run at the same time, if the Controller is sure that one Task
will not affect the Results of another Task.</t>
<t>The Controller should ensure that the Active Measurement Tasks do
not have an adverse effect on the end user. Typically Tasks,
especially those that generate a substantial amount of traffic, will
include a pre-check that the user isn’t already sending traffic
(Section 5.3). Another consideration is whether Active Measurement
Traffic will impact a Subscriber's bill or traffic cap.</t>
<t>The different elements of the Instruction can be updated
independently. For example, the Measurement Tasks could be configured
with different Input Parameters whilst keeping the same Measurement
Schedule. In general this should not create any issues, since
Measurement Methods should be defined so their fundamental nature does
not change for a new value of Input Parameter. There could be a
problem if, for example, a Measurement Task involving a 1kB file
upload could be changed into a 1GB file upload.</t>
<t>A measurement system may have multiple Controllers (but note the
overriding principle that a single MA is instructed by a single
Controller at any point in time (Section 4.2)). For example, there
could be different Controllers for different types of MA (home
gateways, tablets) or locations (Ipswich, Edinburgh), for load
balancing or to cope with failure of one Controller. One possibility
is that Bootstrapping involves an initial Controller, whose role is
simply to inform the MA how to contact its actual Controller.</t>
<t/>
</section>
<section title="Measurement Agent">
<t>The Measurement Agent could take a number of forms: a dedicated
probe, software on a PC, embedded into an appliance, or even embedded
into a gateway. A single site (home, branch office etc.) that is
participating in a measurement could make use of one or multiple
Measurement Agents in a single measurement. If the site is multi homed
there might be a Measurement Agent per interface.</t>
<t>The Measurement Agent could be deployed in a variety of locations.
Not all deployment locations are available to every kind of
Measurement Agent. There are also a variety of limitations and
trade-offs depending on the final placement. The next sections outline
some of the locations a Measurement Agent may be deployed. This is not
an exhaustive list and combinations may also apply.</t>
<t/>
<t>If the Instruction includes several Measurement Tasks, these could
be scheduled to run at different times or possibly at the same time -
some Tasks may be compatible, in that they do not affect each other's
Results, whilst with others great care would need to be taken.</t>
<t>The measurement system also needs to consider carefully how to
interpret missing Results; for example, if the missing Results are
ignored and the lack of a Report is caused by its broadband being
broken, then the estimate of overall performance, averaged across all
MAs, would be too optimistic.</t>
<t/>
<section title="Measurement Agent embedded in site gateway">
<t>A Measurement Agent embedded with the site gateway, for example a
home router or the edge router of a branch office in a managed
service environment, is one of better places the Measurement Agent
could be deployed. All site-to-ISP traffic would traverse through
the gateway and passive measurements could easily be performed.
Similarly, due to this user traffic visibility, an Active
Measurements Task could be rescheduled so as not to compete with
user traffic. Generally NAT and firewall services are built into the
gateway, allowing the Measurement Agent the option to offer its
Controller facing management interface outside of the NAT/firewall.
This placement of the management interface allows the Controller to
unilaterally contact the Measurement Agent for instructions.
However, if the site gateway is owned and operated by the service
provider, the Measurement Agent will generally not be directly
available for over the top providers, the regulator, end users or
enterprises.</t>
<t/>
</section>
<section title="Measurement Agent embedded behind site NAT /Firewall">
<t>The Measurement Agent could also be embedded behind a NAT, a
firewall, or both. In this case the Controller may not be able to
unilaterally contact the Measurement Agent unless either static port
forwarding configuration or firewall pin holing is configured, and
might not always be possible. It would require user intervention or
pre-provisioning by the operator via a mechanisms such as TR-069.
The Measurement Agent may originate a session towards the Controller
and maintain the session for bidirectional communications. This
would alleviate the need to have user intervention on the gateway,
but would reduce the overall saleability of the Controller as it
would have to maintain a higher number of active sessions. That
said, sending keepalives to prop open the firewall could serve a
dual purpose in testing network reachability for the Measurement
Agent. An alternative would be to use a protocol such as UPnP or PCP
<xref target="RFC6887"/> to control the NAT/firewall if the gateway
supports this kind of control.</t>
</section>
<section title="Measurement Agent in a multi-homed site">
<t>A broadband site may be multi-homed. For example, the site may be
connected to multiple broadband ISPs, perhaps for redundancy or
load- sharing, or have both wired and wireless broadband
connectivity. It may also be helpful to think of dual stack IPv4 and
IPv6 broadband devices as multi-homed. In these cases, there needs
to be clarity on which network connectivity option is being
measured. Sometimes this is easily resolved by the location of the
MA itself. For example, if the MA is built into the gateway (and the
gateway only has a single WAN side interface), there is little
confusion or choice. However, for multi-homed gateways or devices
behind the gateway(s) of multi-homed sites it would be preferable to
explicitly select the network to measure (<xref target="RFC5533"/>)
but the network measured should be included in the Measurement
Result. Section 3.2 of <xref target="I-D.ietf-homenet-arch"/>
describes dual-stack and multi-homing topologies that might be
encountered in a home network (which is generally a broadband
connected site). The Multiple Interfaces (mif) working group covers
cases where hosts are either directly attached to multiple networks
(physical or virtual) or indirectly (multiple default routers,
etc.). <xref target="RFC6419"/> provides the current practices of
multi-interfaces hosts today. As one aim is for a MA is to measure
the end user's quality of experience, it is important to understand
the current practices.</t>
<t/>
</section>
</section>
<section title="Measurement Peer">
<t>A Measurement Peer participates in Active Measurement Tasks. It may
have specific functionality to enable it to participate in a
particular Measurement Method. On the other hand, other Measurement
Methods may require no special functionality, for example if the
Measurement Agent sends a ping to example.com then the server at
example.com plays the role of a Measurement Peer.</t>
<t>A device may participate in some Measurement Tasks as a Measurement
Agent and in others as a Measurement Peer.</t>
<t/>
</section>
</section>
<section title="Security considerations">
<t/>
<t>The security of the LMAP framework should protect the interests of
the measurement operator(s), the network user(s) and other actors who
could be impacted by a compromised measurement deployment. The
measurement system must secure the various components of the system from
unauthorised access or corruption.</t>
<t>We assume that each Measurement Agent (MA) will receive its
Instructions from a single organisation, which operates the Controller.
These Instructions must be authenticated (to ensure that they come from
the trusted Controller), checked for integrity (to ensure no-one has
tampered with them) and not vulnerable to replay attacks. If a malicious
party can gain control of the MA they can use it to launch DoS attacks
at targets, reduce the end user's quality of experience and corrupt the
Measurement Results that are reported to the Collector. By altering the
Measurement Tasks and/or the address that Results are reported to, they
can also compromise the confidentiality of the network user and the MA
environment (such as information about the location of devices or their
traffic).</t>
<t>Reporting by the MA must also be secured to maintain confidentiality.
The results must be encrypted such that only the authorised Collector
can decrypt the results to prevent the leakage of confidential or
private information. In addition it must be authenticated that the
results have come from the expected MA and that they have not been
tampered with. It must not be possible to fool a MA into injecting
falsified data into the measurement platform or to corrupt the results
of a real MA. The results must also be held and processed securely after
collection and analysis.</t>
<t>Availability should also be considered. While the loss of some MAs
may not be considered critical, the unavailability of the Collector
could mean that valuable business data or data critical to a regulatory
process is lost. Similarly, the unavailability of a Controller could
mean that the MAs do not operate a correct Measurement Schedule.</t>
<t>A malicious party could "game the system". For example, where a
regulator is running a measurement system in order to benchmark
operators, an operator could try to identify the broadband lines that
the regulator was measuring and prioritise that traffic. This potential
issue is currently handled by a code of conduct. It is outside the scope
of the LMAP WG to consider the issue.</t>
<t/>
</section>
<section title="Privacy Considerations for LMAP">
<t>The LMAP Working Group will consider privacy as a core requirement
and will ensure that by default the Control and Report Protocols operate
in a privacy-sensitive manner and that privacy features are
well-defined.</t>
<t>This section provides a set of privacy considerations for LMAP. This
section benefits greatly from the timely publication of <xref
target="RFC6973"/>. Privacy and security (Section 7) are related. In
some jurisdictions privacy is called data protection.</t>
<t>We begin with a set of assumptions related to protecting the
sensitive information of individuals and organisations participating in
LMAP-orchestrated measurement and data collection.</t>
<section title="Categories of Entities with Information of Interest">
<t>LMAP protocols need to protect the sensitive information of the
following entities, including individuals and organisations who
participate in measurement and collection of results.<list
style="symbols">
<t>Individual Internet users: Persons who utilise Internet access
services for communications tasks, according to the terms of
service of a service agreement. Such persons may be a service
Subscriber, or have been given permission by the Subscriber to use
the service.</t>
<t>Internet service providers: Organisations who offer Internet
access service subscriptions, and thus have access to sensitive
information of individuals who choose to use the service. These
organisations desire to protect their Subscribers and their own
sensitive information which may be stored in the process of
performing Measurement Tasks and collecting and Results.</t>
<t>Regulators: Public authorities responsible for exercising
supervision of the electronic communications sector, and which may
have access to sensitive information of individuals who
participate in a measurement campaign. Similarly, regulators
desire to protect the participants and their own sensitive
information.</t>
<t>Other LMAP system operators: Organisations who operate
measurement systems or participate in measurements in some
way.</t>
</list></t>
<t>Although privacy is a protection extended to individuals, we
include discussion of ISPs and other LMAP system operators in this
section. These organisations have sensitive information involved in
the LMAP system, and many of the same dangers and mitigations are
applicable. Further, the ISPs store information on their Subscribers
beyond that used in the LMAP system (for instance billing
information), and there should be a benefit in considering all the
needs and potential solutions coherently.</t>
</section>
<section title="Examples of Sensitive Information">
<t>This section gives examples of sensitive information which may be
measured or stored in a measurement system, and which is to be kept
private by default in the LMAP core protocols.</t>
<t>Examples of Subscriber or authorised Internet user sensitive
information:</t>
<t><list style="symbols">
<t>Sub-IP layer addresses and names (MAC address, base station ID,
SSID)</t>
<t>IP address in use</t>
<t>Personal Identification (real name)</t>
<t>Location (street address, city)</t>
<t>Subscribed service parameters</t>
<t>Contents of traffic (activity, DNS queries, destinations,
equipment types, account info for other services, etc.)</t>
<t>Status as a study volunteer and Schedule of (Active)
Measurement Tasks</t>
</list></t>
<t>Examples of Internet Service Provider sensitive information:<list
style="symbols">
<t>Measurement device identification (equipment ID and IP
address)</t>
<t>Measurement Instructions (choice of measurements)</t>
<t>Measurement Results (some may be shared, others may be
private)</t>
<t>Measurement Schedule (exact times)</t>
<t>Network topology (locations, connectivity, redundancy)</t>
<t>Subscriber billing information, and any of the above Subscriber
information known to the provider.</t>
<t>Authentication credentials (such as certificates)</t>
</list></t>
<t>Other organisations will have some combination of the lists above.
The LMAP system would not typically expose all of the information
above, but could expose a combination of items which could be
correlated with other pieces collected by an attacker (as discussed in
the section on Threats below).</t>
</section>
<section title="Key Distinction Between Active and Passive Measurement Tasks">
<t>Passive and Active Measurement Tasks raise different privacy
issues.</t>
<t>Passive Measurement Tasks are conducted on a user's traffic, such
that sensitive information is present and stored in the measurement
system (however briefly this storage may be). We note that some
authorities make a distinction on time of storage, and information
that is kept only temporarily to perform a communications function is
not subject to regulation (for example, active queue management, deep
packet inspection). Passive Measurement Tasks could reveal all the
websites a Subscriber visits and the applications and/or services they
use.</t>
<t>Active Measurement Tasks are conducted on traffic which is created
specifically for the purpose. Even if a user host generates Active
Measurement Traffic, there is significantly limited sensitive
information about the Subscriber present and stored in the measurement
system compared to the passive case, as follows:<list style="symbols">
<t>IP address in use (and possibly sub-IP addresses and names)</t>
<t>Status as a study volunteer and Schedule of Active Measurement
Tasks</t>
</list></t>
<t>On the other hand, for a service provider the sensitive information
like Measurement Results is the same for Passive and Active
Measurement Tasks.</t>
<t>From the Subscriber perspective, both Active and Passive
Measurement Tasks potentially expose the description of Internet
access service and specific service parameters, such as subscribed
rate and type of access.</t>
</section>
<section title="Privacy analysis of the Communications Models">
<t>This section examines each of the protocol exchanges described at a
high level in Section 5 and some example Measurement Tasks, and
identifies specific sensitive information which must be secured during
communication for each case. With the protocol-related sensitive
information identified, we have can better consider the threats
described in the following section.</t>
<t>From the privacy perspective, all entities participating in LMAP
protocols can be considered "observers" according to the definition in
<xref target="RFC6973"/>. Their stored information potentially poses a
threat to privacy, especially if one or more of these functional
entities has been compromised. Likewise, all devices on the paths used
for control, reporting, and measurement are also observers.</t>
<t/>
<section title="MA Bootstrapping">
<t>Section 5.1 provides the communication model for the
Bootstrapping process.</t>
<t>Although the specification of mechanisms for Bootstrapping the MA
are beyond the LMAP scope, designers should recognize that the
Bootstrapping process is extremely powerful and could cause an MA to
join a new or different LMAP system with a different Controller and
Collector, or simply install new Measurement Methods (for example to
passively record DNS queries). A Bootstrap attack could result in a
breach of the LMAP system with significant sensitive information
exposure depending on the capabilities of the MA, so sufficient
security protections are warranted.</t>
<t>The Bootstrapping process provides sensitive information about
the LMAP system and the organisation that operates it, such as <list
style="symbols">
<t>Initial Controller IP address or FQDN</t>
<t>Assigned Controller IP address or FQDN</t>
<t>Security certificates and credentials</t>
</list></t>
<t>During the Bootstrap process, the MA receives its MA-ID which is
a persistent pseudonym for the Subscriber in the case that the MA is
located at a service demarcation point. Thus, the MA-ID is
considered sensitive information, because it could provide the link
between Subscriber identification and Measurements Results.</t>
<t>Also, the Bootstrap process could assign a Group-ID to the MA.
The specific definition of information represented in a Group-ID is
to be determined, but several examples are envisaged including use
as a pseudonym for a set of Subscribers, a class of service, an
access technology, or other important categories. Assignment of a
Group-ID enables anonymisation sets to be formed on the basis of
service type/grade/rates. Thus, the mapping between Group-ID and
MA-ID is considered sensitive information.</t>
</section>
<section title="Controller <-> Measurement Agent">
<t>The high-level communication model for interactions between the
LMAP Controller and Measurement Agent is illustrated in Section 5.2.
The primary purpose of this exchange is to authenticate and task a
Measurement Agent with Measurement Instructions, which the
Measurement Agent then acts on autonomously.</t>
<t>Primarily IP addresses and pseudonyms (MA-ID, Group-ID) are
exchanged with a capability request, then measurement-related
information of interest such as the parameters, schedule, metrics,
and IP addresses of measurement devices. Thus, the measurement
Instruction contains sensitive information which must be secured.
For example, the fact that an ISP is running additional measurements
beyond the set reported externally is sensitive information, as are
the additional Measurements Tasks themselves. The Measurement
Schedule is also sensitive, because an attacker intending to bias
the results without being detected can use this information to great
advantage.</t>
<t>An organisation operating the Controller having no service
relationship with a user who hosts the Measurement Agent *could*
gain real-name mapping to a public IP address through user
participation in an LMAP system (this applies to the Measurement
Collection protocol, as well).</t>
</section>
<section title="Collector <-> Measurement Agent">
<t>The high-level communication model for interactions between the
Measurement Agent and Collector is illustrated in Section 5.4. The
primary purpose of this exchange is to authenticate and collect
Measurement Results from a MA, which the MA has measured
autonomously and stored.</t>
<t>The Measurement Results are the additional sensitive information
included in the Collector-MA exchange. Organisations collecting LMAP
measurements have the responsibility for data control. Thus, the
Results and other information communicated in the Collector protocol
must be secured.</t>
</section>
<section title="Measurement Peer <-> Measurement Agent ">
<t>Although the specification of the mechanisms for an Active
Measurement Task is beyond the scope of LMAP, it raises potential
privacy issues. The high-level communications model below
illustrates the various exchanges to execute Active Measurement
Tasks and store the Results.</t>
<t>We note the potential for additional observers in the figures
below by indicating the possible presence of a NAT, which has
additional significance to the protocols and direction of
initiation.</t>
<t>The various messages are optional, depending on the nature of the
Active Measurement Task. It may involve sending Active Measurement
Traffic from the Measurement Peer to MA, MA to Measurement Peer, or
both. <figure>
<artwork><![CDATA[ _________________ _________________
| | | |
|Measurement Peer |=========== NAT ? ==========|Measurement Agent|
|_________________| |_________________|
<- (Key Negotiation &
Encryption Setup)
(Encrypted Channel ->
Established)
(Announce capabilities ->
& status)
<- (Select capabilities)
ACK ->
<- (Measurement Request
(MA+MP IPAddrs,set of
Metrics, Schedule))
ACK ->
Active Measurement Traffic <> Active Measurement Traffic
(may/may not be encrypted) (may/may not be encrypted)
<- (Stop Measurement Task)
Measurement Results ->
(if applicable)
<- ACK, Close
]]></artwork>
</figure>This exchange primarily exposes the IP addresses of
measurement devices and the inference of measurement participation
from such traffic. There may be sensitive information on key points
in a service provider's network included. There may also be access
to measurement-related information of interest such as the Metrics,
Schedule, and intermediate results carried in the Active Measurement
Traffic (usually a set of timestamps).</t>
<t>If the Active Measurement Traffic is unencrypted, as found in
many systems today, then both timing and limited results are open to
on-path observers.</t>
</section>
<section title="Passive Measurement Agent ">
<t>Although the specification of the mechanisms for a Passive
Measurement Task is beyond the scope of LMAP, it raises potential
privacy issues. </t>
<t>The high-level communications model below illustrates the
collection of user information of interest with the Measurement
Agent performing the monitoring and storage of the Results. This
particular exchange is for passive measurement of DNS Response Time,
which most frequently uses UDP transport.</t>
<t><figure>
<artwork><![CDATA[ _________________ ____________
| | | |
| DNS Server |=========== NAT ? ==========*=======| User client|
|_________________| ^ |____________|
______|_______
| |
| Measurement |
| Agent |
|______________|
<- Name Resolution Req
(MA+MP IPAddrs,
Desired Domain Name)
Return Record ->
]]></artwork>
</figure></t>
<t>This exchange primarily exposes the IP addresses of measurement
devices and the intent to communicate with or access the services of
"Domain Name". There may be information on key points in a service
provider's network, such as the address of one of its DNS servers.
The Measurement Agent may be embedded in the user host, or it may be
located in another device capable of observing user traffic.</t>
<t>In principle, any of the user sensitive information of interest
(listed above) can be collected and stored in the passive monitoring
scenario and so must be secured.</t>
<t>It would also be possible for a Measurement Agent to source the
DNS query itself. But then, as with any active measurement task,
there are few privacy concerns.</t>
<t/>
</section>
<section title="Storage and Reporting of Measurement Results">
<t>Although the mechanisms for communicating results (beyond the
initial Collector) are beyond the LMAP scope, there are potential
privacy issues related to a single organisation's storage and
reporting of Measurement Results. Both storage and reporting
functions can help to preserve privacy by implementing the
mitigations described below.</t>
</section>
</section>
<section title="Threats">
<t>This section indicates how each of the threats described in <xref
target="RFC6973"/> apply to the LMAP entities and their communication
and storage of "information of interest".</t>
<section title="Surveillance">
<t>Section 5.1.1 of <xref target="RFC6973"/> describes Surveillance
as the "observation or monitoring of and individual's communications
or activities." Hence all Passive Measurement Tasks are a form of
surveillance, with inherent risks.</t>
<t>Active Measurement Methods which avoid periods of user
transmission indirectly produce a record of times when a subscriber
or authorised user has used their network access service.</t>
<t>Active Measurement Methods may also utilise and store a
Subscriber's currently assigned IP address when conducting
measurements that are relevant to a specific Subscriber. Since the
Measurement Results are time-stamped, they could provide a record of
IP address assignments over time.</t>
<t>Either of the above pieces of information could be useful in
correlation and identification, described below.</t>
</section>
<section title="Stored Data Compromise">
<t>Section 5.1.2 of <xref target="RFC6973"/> describes Stored Data
Compromise as resulting from inadequate measures to secure stored
data from unauthorised or inappropriate access. For LMAP systems
this includes deleting or modifying collected measurement records,
as well as data theft.</t>
<t>The primary LMAP entity subject to compromise is the repository,
which stores the Measurement Results; extensive security and privacy
threat mitigations are warranted. The Collector and MA also store
sensitive information temporarily, and need protection. The
communications between the local storage of the Collector and the
repository is beyond the scope of the LMAP work at this time, though
this communications channel will certainly need protection as well
as the mass storage itself.</t>
<t>The LMAP Controller may have direct access to storage of
Subscriber information (location, billing, service parameters, etc.)
and other information which the controlling organisation considers
private, and again needs protection.</t>
<t/>
</section>
<section title="Correlation and Identification">
<t>Sections 5.2.1 and 5.2.2 of <xref target="RFC6973"/> describes
Correlation as combining various pieces of information to obtain
desired characteristics of an individual, and Identification as
using this process to infer identity.</t>
<t>The main risk is that the LMAP system could unwittingly provide a
key piece of the correlation chain, starting with an unknown
Subscriber's IP address and another piece of information. For
example, a Subscriber utilised Internet access from 2000 to 2310
UTC, because the Active Measurement Tasks were deferred, or sent a
name resolution for www.example.com at 2300 UTC.</t>
</section>
<section title="Secondary Use and Disclosure">
<t>Sections 5.2.3 and 5.2.4 of <xref target="RFC6973"/> describes
Secondary Use as unauthorised utilisation of an individual's
information for a purpose the individual did not intend, and
Disclosure is when such information is revealed causing other's
notions of the individual to change, or confidentiality to be
violated.</t>
<t>Passive Measurement Tasks are a form of Secondary Use, and the
Subscribers' permission and the measured ISP's permission should be
obtained beforehand. Although user traffic is only indirectly
involved, the Measurement Results from Active Measurement Tasks
provide some limited information about the Subscriber/ISP and could
be used for Secondary Uses. For example, the use of the Results in
unauthorised marketing campaigns would qualify as Secondary Use.</t>
</section>
</section>
<section title="Mitigations">
<t>This section examines the mitigations listed in section 6 of <xref
target="RFC6973"/> and their applicability to LMAP systems. Note that
each section in <xref target="RFC6973"/> identifies the threat
categories that each technique mitigates.</t>
<section title="Data Minimisation">
<t>Section 6.1 of <xref target="RFC6973"/> encourages collecting and
storing the minimal information needed to perform a task.</t>
<t>There are two levels of information needed for LMAP results to be
useful for a specific task: troubleshooting and general results
reporting.</t>
<t>For general results, the results can be aggregated into large
categories (the month of March, all subscribers West of the
Mississippi River). In this case, all individual identifications
(including IP address of the MA) can be excluded, and only relevant
results are provided. However, this implies a filtering process to
reduce the information fields, because greater detail was needed to
conduct the Measurement Tasks in the first place.</t>
<t>For troubleshooting, so that a network operator or end user can
identify a performance issue or failure, potentially all the network
information (IP addresses, equipment IDs, location), Measurement
Schedule, service configuration, Measurement Results, and other
information may assist in the process. This includes the information
needed to conduct the Measurements Tasks, and represents a need
where the maximum relevant information is desirable, therefore the
greatest protections should be applied.</t>
<t>We note that a user may give temporary permission for Passive
Measurement Tasks to enable detailed troubleshooting, but withhold
permission for them in general. Here the greatest breadth of
sensitive information is potentially exposed, and the maximum
privacy protection must be provided.</t>
<t>For MAs with access to the sensitive information of users (e.g.,
within a home or a personal host/handset), it is desirable for the
results collection to minimise the data reported, but also to
balance this desire with the needs of troubleshooting when a service
subscription exists between the user and organisation operating the
measurements.</t>
<t>For passive measurements where the MA reports flow information to
the Collector, the Collector may perform pre-storage minimisation
and other mitigations (below) to help preserve privacy.</t>
</section>
<section title="Anonymity">
<t>Section 6.1.1 of <xref target="RFC6973"/> describes a way in
which anonymity is achieved: "there must exist a set of individuals
that appear to have the same attributes as the individual", defined
as an "anonymity set".</t>
<t>Experimental methods for anonymisation of user identifiable data
applicable to Passive Measurement Methods have been identified in
<xref target="RFC6235"/>. However, the findings of several of the
same authors is that "there is increasing evidence that
anonymisation applied to network trace or flow data on its own is
insufficient for many data protection applications as in <xref
target="Bur10"/>."</t>
<t>Essentially, the details of passive measurement tasks can only be
accessed by closed organisations, and unknown injection attacks are
always less expensive than the protections from them. However, some
forms of summary may protect the user's sensitive information
sufficiently well, and so each Metric must be evaluated in the light
of privacy.</t>
<t>The methods in <xref target="RFC6235"/> could be applied more
successfully in Active Measurement Methods, where there are
protections from injection attack. The successful attack would
require breaking the integrity protection of the LMAP Reporting
Protocol and injecting Measurement Results (known fingerprint, see
section 3.2 of <xref target="RFC6973"/>) for inclusion with the
shared and anonymised results, then fingerprinting those records to
ascertain the anonymisation process.</t>
<t>Beside anonymisation of measured Results for a specific user or
provider, the value of sensitive information can be further diluted
by summarising the results over many individuals or areas served by
the provider. There is an opportunity enabled by forming anonymity
sets <xref target="RFC6973"/> based on the reference path
measurement points in <xref target="I-D.ietf-ippm-lmap-path"/>. For
example, all measurements from the Subscriber device can be
identified as "mp000", instead of using the IP address or other
device information. The same anonymisation applies to the Internet
Service Provider, where their Internet gateway would be referred to
as "mp190".</t>
</section>
<section title="Pseudonymity">
<t>Section 6.1.2 of <xref target="RFC6973"/> indicates that
pseudonyms, or nicknames, are a possible mitigation to revealing
one's true identity, since there is no requirement to use real names
in almost all protocols.</t>
<t>A pseudonym for a measurement device's IP address could be an
LMAP-unique equipment ID. However, this would likely be a permanent
handle for the device, and long-term use weakens a pseudonym's power
to obscure identity.</t>
</section>
<section title="Other Mitigations">
<t>Data can be de-personalised by blurring it, for example by adding
synthetic data, data-swapping, or perturbing the values in ways that
can be reversed or corrected.</t>
<t>Sections 6.2 and 6.3 of <xref target="RFC6973"/> describe User
Participation and Security, respectively.</t>
<t>Where LMAP measurements involve devices on the Subscriber's
premises or Subscriber-owned equipment, it is essential to secure
the Subscriber's permission with regard to the specific information
that will be collected. The informed consent of the Subscriber (and,
if different, the end user) is needed, including the specific
purpose of the measurements. The approval process could involve
showing the Subscriber their measured information and results before
instituting periodic collection, or before all instances of
collection, with the option to cancel collection temporarily or
permanently.</t>
<t>It should also be clear who is legally responsible for data
protection (privacy); in some jurisdictions this role is called the
'data controller'. It is good practice to time limit the storage of
personal information.</t>
<t>Although the details of verification would be impenetrable to
most subscribers, the MA could be architected as an "app" with open
source-code, pre-download and embedded terms of use and agreement on
measurements, and protection from code modifications usually
provided by the app-stores. Further, the app itself could provide
data reduction and temporary storage mitigations as appropriate and
certified through code review.</t>
<t>LMAP protocols, devices, and the information they store clearly
need to be secure from unauthorised access. This is the hand-off
between privacy and security considerations (Section 7). The Data
Controller has the (legal) responsibility to maintain data
protections described in the Subscriber's agreement and agreements
with other organisations.</t>
<t/>
</section>
</section>
</section>
<section title="IANA Considerations">
<t>There are no IANA considerations in this memo.</t>
</section>
<section title="Acknowledgments">
<t>This document is a merger of three individual drafts:
draft-eardley-lmap-terminology-02, draft-akhter-lmap-framework-00, and
draft-eardley-lmap-framework-02.</t>
<t>Thanks to Juergen Schoenwaelder for his detailed review of the
terminology. Thanks to Charles Cook for a very detailed review of
-02.</t>
<t>Thanks to numerous people for much discussion, directly and on the
LMAP list (apologies to those unintentionally omitted): Alan Clark,
Alissa Cooper, Andrea Soppera, Barbara Stark, Benoit Claise, Brian
Trammell, Charles Cook, Dave Thorne, Frode Sørensen, Greg Mirsky,
Guangqing Deng, Jason Weil, Jean-Francois Tremblay, Jerome Benoit,
Joachim Fabini, Juergen Schoenwaelder, Jukka Manner, Ken Ko, Michael
Bugenhagen, Rolf Winter, Sam Crawford, Sharam Hakimi, Steve Miller, Ted
Lemon, Timothy Carey, Vaibhav Bajpai, William Lupton.</t>
<t>Philip Eardley, Trevor Burbridge and Marcelo Bagnulo work in part on
the Leone research project, which receives funding from the European
Union Seventh Framework Programme [FP7/2007-2013] under grant agreement
number 317647.</t>
<t/>
<t/>
</section>
<section title="History">
<t>First WG version, copy of draft-folks-lmap-framework-00.</t>
<t/>
<section title="From -00 to -01">
<t><list style="symbols">
<t>new sub-section of possible use of Group-IDs for privacy</t>
<t>tweak to definition of Control protocol</t>
<t>fix typo in figure in S5.4</t>
</list></t>
</section>
<section title="From -01 to -02">
<t><list style="symbols">
<t>change to INFORMATIONAL track (previous version had typo'd
Standards track)</t>
<t>new definitions for Capabilities Information and Failure
Information</t>
<t>clarify that diagrams show LMAP-level information flows.
Underlying protocol could do other interactions, eg to get through
NAT or for Collector to pull a Report</t>
<t>add hint that after a re-boot should pause random time before
re-register (to avoid mass calling event)</t>
<t>delete the open issue "what happens if a Controller fails"
(normal methods can handle)</t>
<t>add some extra words about multiple Tasks in one Schedule</t>
<t>clarify that new Schedule replaces (rather than adds to) and
old one. Similarly for new configuration of Measurement Tasks or
Report Channels.</t>
<t>clarify suppression is temporary stop; send a new Schedule to
permanently stop Tasks</t>
<t>alter suppression so it is ACKed</t>
<t>add un-suppress message</t>
<t>expand the text on error reporting, to mention Reporting
failures (as well as failures to action or execute Measurement
Task & Schedule)</t>
<t>add some text about how to have Tasks running indefinitely</t>
<t>add that optionally a Report is not sent when there are no
Measurement Results</t>
<t>add that a Measurement Task may create more than one
Measurement Result</t>
<t>clarify /amend /expand that Reports include the "raw"
Measurement Results - any pre-processing is left for lmap2.0</t>
<t>add some cautionary words about what if the Collector
unexpectedly doesn't hear from a MA</t>
<t>add some extra words about the potential impact of Measurement
Tasks</t>
<t>clarified various aspects of the privacy section</t>
<t>updated references</t>
<t>minor tweaks</t>
</list></t>
</section>
<section title="From -02 to -03">
<t><list style="symbols">
<t>alignment with the Information Model <xref
target="I-D.burbridge-lmap-information-model"/> as this is agreed
as a WG document</t>
<t>One-off and periodic Measurement Schedules are kept separate,
so that they can be updated independently</t>
<t>Measurement Suppression in a separate sub-section. Can now
optionally include particular Measurement Tasks &/or Schedules
to suppress, and start/stop time</t>
<t>for clarity, concept of Channel split into Control, Report and
MA-to-Controller Channels</t>
<t>numerous editorial changes, mainly arising from a very detailed
review by Charles Cook</t>
<t/>
</list></t>
</section>
</section>
</middle>
<back>
<references title="Informative References">
<reference anchor="Bur10">
<front>
<title>The Role of Network Trace anonymisation Under Attack</title>
<author initials="M" surname="Burkhart">
<organization>Burkhart</organization>
</author>
<author initials="D" surname="Schatzmann">
<organization/>
</author>
<author initials="B" surname="Trammell">
<organization/>
</author>
<author initials="E" surname="Boschi">
<organization>ACM Computer Communications Review, vol. 40, no. 1,
pp. 6-11</organization>
</author>
<date month="January" year="2010"/>
</front>
</reference>
<reference anchor="Q1741">
<front>
<title>IMT-2000 references to Release 9 of GSM-evolved UMTS core
network</title>
<author fullname="ITU-T Recommendation" initials=""
surname="Q.1741.7">
<!---->
<organization abbrev="Boeing">Boeing Computer
Services</organization>
</author>
<date month="November" year="2011"/>
</front>
<seriesInfo name="" value="http://www.itu.int/rec/T-REC-Q.1741.7/en"/>
</reference>
<?rfc include='reference.RFC.1035'?>
<?rfc include='reference.RFC.4101'?>
<?rfc include='reference.RFC.4122'?>
<?rfc include='reference.RFC.5357'?>
<?rfc include='reference.I-D.ietf-lmap-use-cases'?>
<?rfc include='reference.I-D.bagnulo-ippm-new-registry-independent'?>
<?rfc include='reference.I-D.ietf-homenet-arch'?>
<?rfc include='reference.RFC.6419'?>
<?rfc include='reference.RFC.6887'?>
<?rfc include='reference.RFC.5533'?>
<?rfc include='reference.I-D.burbridge-lmap-information-model'?>
<?rfc include='reference.RFC.6235'?>
<?rfc include='reference.RFC.6973'?>
<?rfc include='reference.I-D.ietf-ippm-lmap-path'?>
</references>
</back>
</rfc>
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