A framework for large-scale measurement platforms (LMAP)
draft-ietf-lmap-framework-03
The information below is for an old version of the document.
| Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 7594.
|
|
|---|---|---|---|
| Authors | Philip Eardley , Al Morton , Marcelo Bagnulo , Trevor Burbridge , Paul Aitken, Aamer Akhter | ||
| Last updated | 2014-02-24 (Latest revision 2014-01-21) | ||
| Replaces | draft-folks-lmap-framework | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
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| Responsible AD | Benoît Claise | ||
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draft-ietf-lmap-framework-03
Network Working Group P. Eardley
Internet-Draft BT
Intended status: Informational A. Morton
Expires: July 25, 2014 AT&T Labs
M. Bagnulo
UC3M
T. Burbridge
BT
P. Aitken
A. Akhter
Cisco Systems
January 21, 2014
A framework for large-scale measurement platforms (LMAP)
draft-ietf-lmap-framework-03
Abstract
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).
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on July 25, 2014.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
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This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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publication of this document. Please review these documents
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Outline of an LMAP-based measurement system . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 8
4. Constraints . . . . . . . . . . . . . . . . . . . . . . . . . 11
4.1. Measurement system is under the direction of a single
organisation . . . . . . . . . . . . . . . . . . . . . . 11
4.2. Each MA may only have a single Controller at any point in
time . . . . . . . . . . . . . . . . . . . . . . . . . . 12
5. LMAP Protocol Model . . . . . . . . . . . . . . . . . . . . . 12
5.1. Bootstrapping process . . . . . . . . . . . . . . . . . . 13
5.2. Control Protocol . . . . . . . . . . . . . . . . . . . . 15
5.2.1. Measurement Suppression . . . . . . . . . . . . . . . 18
5.3. Starting and stopping Measurement Tasks . . . . . . . . . 19
5.4. Report Protocol . . . . . . . . . . . . . . . . . . . . . 20
5.5. Operation of LMAP over the underlying transport protocol 22
5.6. Items beyond the scope of the LMAP Protocol Model . . . . 23
5.6.1. Enduser-controlled measurement system . . . . . . . . 24
6. Deployment considerations . . . . . . . . . . . . . . . . . . 24
6.1. Controller . . . . . . . . . . . . . . . . . . . . . . . 24
6.2. Measurement Agent . . . . . . . . . . . . . . . . . . . . 25
6.2.1. Measurement Agent embedded in site gateway . . . . . 26
6.2.2. Measurement Agent embedded behind site NAT /Firewall 26
6.2.3. Measurement Agent in a multi-homed site . . . . . . . 27
6.3. Measurement Peer . . . . . . . . . . . . . . . . . . . . 27
7. Security considerations . . . . . . . . . . . . . . . . . . . 27
8. Privacy Considerations for LMAP . . . . . . . . . . . . . . . 28
8.1. Categories of Entities with Information of Interest . . . 29
8.2. Examples of Sensitive Information . . . . . . . . . . . . 29
8.3. Key Distinction Between Active and Passive Measurement
Tasks . . . . . . . . . . . . . . . . . . . . . . . . . . 30
8.4. Privacy analysis of the Communications Models . . . . . . 31
8.4.1. MA Bootstrapping . . . . . . . . . . . . . . . . . . 31
8.4.2. Controller <-> Measurement Agent . . . . . . . . . . 32
8.4.3. Collector <-> Measurement Agent . . . . . . . . . . . 33
8.4.4. Measurement Peer <-> Measurement Agent . . . . . . . 33
8.4.5. Passive Measurement Agent . . . . . . . . . . . . . . 34
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8.4.6. Storage and Reporting of Measurement Results . . . . 35
8.5. Threats . . . . . . . . . . . . . . . . . . . . . . . . . 35
8.5.1. Surveillance . . . . . . . . . . . . . . . . . . . . 36
8.5.2. Stored Data Compromise . . . . . . . . . . . . . . . 36
8.5.3. Correlation and Identification . . . . . . . . . . . 36
8.5.4. Secondary Use and Disclosure . . . . . . . . . . . . 37
8.6. Mitigations . . . . . . . . . . . . . . . . . . . . . . . 37
8.6.1. Data Minimisation . . . . . . . . . . . . . . . . . . 37
8.6.2. Anonymity . . . . . . . . . . . . . . . . . . . . . . 38
8.6.3. Pseudonymity . . . . . . . . . . . . . . . . . . . . 39
8.6.4. Other Mitigations . . . . . . . . . . . . . . . . . . 39
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 40
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 40
11. History . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
11.1. From -00 to -01 . . . . . . . . . . . . . . . . . . . . 41
11.2. From -01 to -02 . . . . . . . . . . . . . . . . . . . . 41
11.3. From -02 to -03 . . . . . . . . . . . . . . . . . . . . 42
12. Informative References . . . . . . . . . . . . . . . . . . . 42
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 44
1. Introduction
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:
o Operators: to help plan their network and identify faults
o Regulators: to benchmark several network operators and support
public policy development
Further details of the use cases can be found at
[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.
The LMAP framework has four basic elements: Measurement Agents,
Measurement Peers, Controllers and Collectors.
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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.).
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.
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.
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.
The desirable features for a large-scale measurement systems we are
designing for are:
o 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.
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o Large-scale - [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).
o 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.
2. Outline of an LMAP-based measurement system
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.
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.
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 [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.
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.
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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.
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.
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").
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.
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.
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).
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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.
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.
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.
The operator's OAM (Operations, Administration, and Maintenance) uses
the results from the tools.
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^
|
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)
3. Terminology
This section defines terminology for LMAP. Please note that defined
terms are capitalized.
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.
Active Measurement Traffic: the packet(s) generated by the
Measurement Agent and/or the Measurement Peer, as part of an Active
Measurement Task.
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Bootstrap: A process that initialises a Measurement Agent with the
information necessary to be integrated into a measurement system.
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.
Channel: an Instruction Channel, Report Channel or MA-to-Controller
Channel
Collector: A function that receives a Report from a Measurement
Agent.
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.
Controller: A function that provides a Measurement Agent with
Instruction(s).
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.
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.
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.
Data Model: The implementation of an Information Model in a
particular data modelling language.
Environmental Constraint: A parameter that is measured as part of the
Measurement Task, its value determining whether the rest of the
Measurement Task proceeds.
Failure Information: Information about the MA's failure to action or
execute an Instruction, whether concerning Measurement Tasks or
Reporting.
Group-ID: (optional) An identifier of a group of MAs.
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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.
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.
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.
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.
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.
Measurement Agent Identifier (MA-ID): a UUID [RFC4122], which is
configured as part of the Bootstrapping and included in a
Capabilities message, Failure Information message and optionally in a
Report.
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 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.
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 Measurement Tasks.
Measurement Suppression: a type of Instruction that temporarily stops
(suppresses) Active 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.
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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.
Passive Measurement Method (Task): A Measurement Method (Task) in
which a Measurement Agent observes existing traffic but does not
inject Active Measurement Traffic.
Report: The Measurement Results and other associated information (as
defined by the Instruction). The Report is sent by a Measurement
Agent to a Collector.
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.
Report Protocol: The protocol delivering Report(s) from a Measurement
Agent to a Collector.
Report Schedule: the schedule for sending one or more Reports to a
Collector.
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. [Q1741]
Both the Subscriber and service provider are allowed to set the
limits relative to the use that associated users make of subscribed
services.
4. Constraints
The LMAP framework makes some important assumptions, which constrain
the scope of the work to be done.
4.1. Measurement system is under the direction of a single organisation
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.
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
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organisation constitutes a single LMAP domain which may span
ownership or other administrative boundaries.
4.2. Each MA may only have a single Controller at any point in time
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).
An operator may have several Controllers, perhaps with a Controller
for different types of MA (home gateways, tablets) or location
(Ipswich, Edinburgh).
5. LMAP Protocol Model
A protocol model [RFC4101] presents an architectural model for how
the protocol operates and needs to answer three basic questions:
1. What problem is the protocol trying to achieve?
2. What messages are being transmitted and what do they mean?
3. What are the important, but unobvious, features of the protocol?
An LMAP system goes through the following phases:
o a bootstrapping process before the MA can take part in the other
three phases
o 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
o 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.
o a Report Protocol, which delivers a Report from the MA to a
Collector. The Report contains the Measurement Results.
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In the diagrams the following convention is used:
o (optional): indicated by round brackets
o [potentially repeated]: indicated by square brackets
The protocol model is closely related to the Information Model
[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.
The diagrams show the various LMAP messages and Section 5.5 considers
how they could be mapped onto an underlying transport protocol.
5.1. Bootstrapping process
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).
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+--------------+
| 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
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) [RFC1035].
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.
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-
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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.
The MA may tell the Controller its Capabilities, in particular the
Measurement Methods it can perform.
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.
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.
5.2. Control Protocol
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.
+-----------------+ +-------------+
| | | Measurement |
| Controller |===================================| Agent |
+-----------------+ +-------------+
(Capabilities request) ->
<- Capabilities
ACK ->
Instruction:
[(Measurement Task (Input Parameters)), ->
(Measurement Schedule),
(Report Channel(s))]
<- ACK
<- Failure Information:
[reason]
ACK ->
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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.
A single Instruction message contains one, two, three or all four of
the following elements:
o configuration of all the Measurement Tasks, each of which needs:
* the Measurement Method, specified as a URN to a registry entry.
The registry could be defined by the IETF
[I-D.bagnulo-ippm-new-registry-independent], locally by the
operator of the measurement system or perhaps by another
standards organisation.
* any Input Parameters that need to be set for the Measurement
Method, such as the address of the Measurement Peer
* if the device with the MA has multiple interfaces, then the
interface to use
* optionally, a Cycle-ID
* a name for this Measurement Task configuration
o configuration of all the Report Channels, each of which needs:
* the address of the Collector, for instance its URL
* the timing of when to report Measurement Results, for example
every hour or immediately
* security for sending the Report, for example the X.509
certificate
* a name for this Report Channel
o the set of periodic Measurement Schedules, each of which needs:
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* the name of one or several Measurement Task configurations
* the timing of when the Measurement Tasks are to be performed.
Possible types of timing are periodic and calendar-based
periodic
* the name of a Report Channel or Channels on which to report the
Measurement Results
* a name for this Measurement Schedule
o 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.
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.
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.
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.
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.
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
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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.
In the Figure, ACK means that the message has been delivered
successfully.
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.
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.
5.2.1. Measurement Suppression
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:
o 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.
o 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.
o a start time, at which suppression begins
o an end time, at which suppression ends.
It is not standardised what the impact of Suppression is on:
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o 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
o on-going Active Measurement Tasks; see Section 5.3
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).
+-----------------+ +-------------+
| | | Measurement |
| Controller |===================================| Agent |
+-----------------+ +-------------+
Suppress:
[(Measurement Task), ->
(Measurement Schedule),
start time, end time]
<- ACK
Un-suppress ->
<- ACK
5.3. Starting and stopping Measurement Tasks
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.
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.
Many Active Measurement Tasks begin with a pre-check before the test
traffic is sent. Action could include:
o the MA checking that there is no cross-traffic; in other words, a
check that the user isn't already sending traffic;
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o 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);
o the first part of the Measurement Task consisting of traffic that
probes the path to make sure it isn't overloaded.
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:
o For 'upload' tests, the MA not sending traffic
o For 'download' tests, the MA closing the TCP connection or sending
a TWAMP Stop control message [RFC5357].
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).
{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.}
5.4. Report Protocol
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.
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+-----------------+ +-------------+
| | | Measurement |
| Collector |===================================| Agent |
+-----------------+ +-------------+
<- Report:
[MA-ID &/or Group-ID,
Measurement Results,
details of Measurement Task]
ACK ->
The Report contains:
o the MA-ID or a Group-ID (to anonymise results)
o the actual Measurement Results, including the time they were
measured
o the details of the Measurement Task (to avoid the Collector having
to ask the Controller for this information later)
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).
Optionally, a Report is not sent when there are no Measurement
Results.
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:
o labelling, or perhaps not including, Measurement Results impacted
by, for instance, cross-traffic or the Measurement Peer being busy
o not reporting the Measurement Results if the MA believes that they
are invalid
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o detailing when suppression started and ended
o filtering outlier Results
o calculating some statistic like average (beyond that defined by
the Measurement Task itself)
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.
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.
5.5. Operation of LMAP over the underlying transport protocol
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.
For the Control Protocol, the underlying transport protocol could be:
o a 'push' protocol (that is, from the Controller to the MA)
o a multicast protocol (from the Controller to a group of MAs)
o 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.
o 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.
For the Report Protocol, the underlying transport protocol could be:
o a 'push' protocol (that is, from the MA to the Collector)
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o perhaps supplemented by the ability for the Collector to 'pull'
Measurement Results from a MA.
5.6. Items beyond the scope of the LMAP Protocol Model
There are several potential interactions between LMAP elements that
are out of scope of definition by the LMAP WG:
1. 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.
2. 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.
3. 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.
* 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.
4. 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.
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5. It does not define how to analyse Measurement Results, including
how to interpret missing Results.
6. It does not specifically define a enduser-controlled measurement
system, see sub-section 5.6.1.
5.6.1. Enduser-controlled measurement system
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):
1. 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.
2. 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.
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.
6. Deployment considerations
6.1. Controller
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
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Tasks and the Reporting Schedule are sensible for each MA that it
Instructs.
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.
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.
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.
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.
6.2. Measurement Agent
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.
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.
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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.
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.
6.2.1. Measurement Agent embedded in site gateway
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.
6.2.2. Measurement Agent embedded behind site NAT /Firewall
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
[RFC6887] to control the NAT/firewall if the gateway supports this
kind of control.
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6.2.3. Measurement Agent in a multi-homed site
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 ([RFC5533]) but the network measured should be included in
the Measurement Result. Section 3.2 of [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.).
[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.
6.3. Measurement Peer
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.
A device may participate in some Measurement Tasks as a Measurement
Agent and in others as a Measurement Peer.
7. Security considerations
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.
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
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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).
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.
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.
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.
8. Privacy Considerations for LMAP
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.
This section provides a set of privacy considerations for LMAP. This
section benefits greatly from the timely publication of [RFC6973].
Privacy and security (Section 7) are related. In some jurisdictions
privacy is called data protection.
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.
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8.1. Categories of Entities with Information of Interest
LMAP protocols need to protect the sensitive information of the
following entities, including individuals and organisations who
participate in measurement and collection of results.
o 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.
o 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.
o 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.
o Other LMAP system operators: Organisations who operate measurement
systems or participate in measurements in some way.
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.
8.2. Examples of Sensitive Information
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.
Examples of Subscriber or authorised Internet user sensitive
information:
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o Sub-IP layer addresses and names (MAC address, base station ID,
SSID)
o IP address in use
o Personal Identification (real name)
o Location (street address, city)
o Subscribed service parameters
o Contents of traffic (activity, DNS queries, destinations,
equipment types, account info for other services, etc.)
o Status as a study volunteer and Schedule of (Active) Measurement
Tasks
Examples of Internet Service Provider sensitive information:
o Measurement device identification (equipment ID and IP address)
o Measurement Instructions (choice of measurements)
o Measurement Results (some may be shared, others may be private)
o Measurement Schedule (exact times)
o Network topology (locations, connectivity, redundancy)
o Subscriber billing information, and any of the above Subscriber
information known to the provider.
o Authentication credentials (such as certificates)
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).
8.3. Key Distinction Between Active and Passive Measurement Tasks
Passive and Active Measurement Tasks raise different privacy issues.
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
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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.
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:
o IP address in use (and possibly sub-IP addresses and names)
o Status as a study volunteer and Schedule of Active Measurement
Tasks
On the other hand, for a service provider the sensitive information
like Measurement Results is the same for Passive and Active
Measurement Tasks.
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.
8.4. Privacy analysis of the Communications Models
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.
From the privacy perspective, all entities participating in LMAP
protocols can be considered "observers" according to the definition
in [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.
8.4.1. MA Bootstrapping
Section 5.1 provides the communication model for the Bootstrapping
process.
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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.
The Bootstrapping process provides sensitive information about the
LMAP system and the organisation that operates it, such as
o Initial Controller IP address or FQDN
o Assigned Controller IP address or FQDN
o Security certificates and credentials
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.
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.
8.4.2. Controller <-> Measurement Agent
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.
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
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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.
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).
8.4.3. Collector <-> Measurement Agent
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.
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.
8.4.4. Measurement Peer <-> Measurement Agent
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.
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.
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.
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_________________ _________________
| | | |
|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
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).
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.
8.4.5. Passive Measurement Agent
Although the specification of the mechanisms for a Passive
Measurement Task is beyond the scope of LMAP, it raises potential
privacy issues.
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
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is for passive measurement of DNS Response Time, which most
frequently uses UDP transport.
_________________ ____________
| | | |
| DNS Server |=========== NAT ? ==========*=======| User client|
|_________________| ^ |____________|
______|_______
| |
| Measurement |
| Agent |
|______________|
<- Name Resolution Req
(MA+MP IPAddrs,
Desired Domain Name)
Return Record ->
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.
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.
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.
8.4.6. Storage and Reporting of Measurement Results
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.
8.5. Threats
This section indicates how each of the threats described in [RFC6973]
apply to the LMAP entities and their communication and storage of
"information of interest".
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8.5.1. Surveillance
Section 5.1.1 of [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.
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.
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.
Either of the above pieces of information could be useful in
correlation and identification, described below.
8.5.2. Stored Data Compromise
Section 5.1.2 of [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.
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.
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.
8.5.3. Correlation and Identification
Sections 5.2.1 and 5.2.2 of [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.
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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.
8.5.4. Secondary Use and Disclosure
Sections 5.2.3 and 5.2.4 of [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.
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.
8.6. Mitigations
This section examines the mitigations listed in section 6 of
[RFC6973] and their applicability to LMAP systems. Note that each
section in [RFC6973] identifies the threat categories that each
technique mitigates.
8.6.1. Data Minimisation
Section 6.1 of [RFC6973] encourages collecting and storing the
minimal information needed to perform a task.
There are two levels of information needed for LMAP results to be
useful for a specific task: troubleshooting and general results
reporting.
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.
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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.
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.
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.
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.
8.6.2. Anonymity
Section 6.1.1 of [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".
Experimental methods for anonymisation of user identifiable data
applicable to Passive Measurement Methods have been identified in
[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 [Bur10]."
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.
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The methods in [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 [RFC6973]) for
inclusion with the shared and anonymised results, then fingerprinting
those records to ascertain the anonymisation process.
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 [RFC6973] based on the reference path measurement points in
[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".
8.6.3. Pseudonymity
Section 6.1.2 of [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.
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.
8.6.4. Other Mitigations
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.
Sections 6.2 and 6.3 of [RFC6973] describe User Participation and
Security, respectively.
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.
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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.
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.
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.
9. IANA Considerations
There are no IANA considerations in this memo.
10. Acknowledgments
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.
Thanks to Juergen Schoenwaelder for his detailed review of the
terminology. Thanks to Charles Cook for a very detailed review of
-02.
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 Soerensen, 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.
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.
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11. History
First WG version, copy of draft-folks-lmap-framework-00.
11.1. From -00 to -01
o new sub-section of possible use of Group-IDs for privacy
o tweak to definition of Control protocol
o fix typo in figure in S5.4
11.2. From -01 to -02
o change to INFORMATIONAL track (previous version had typo'd
Standards track)
o new definitions for Capabilities Information and Failure
Information
o 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
o add hint that after a re-boot should pause random time before re-
register (to avoid mass calling event)
o delete the open issue "what happens if a Controller fails" (normal
methods can handle)
o add some extra words about multiple Tasks in one Schedule
o clarify that new Schedule replaces (rather than adds to) and old
one. Similarly for new configuration of Measurement Tasks or
Report Channels.
o clarify suppression is temporary stop; send a new Schedule to
permanently stop Tasks
o alter suppression so it is ACKed
o add un-suppress message
o expand the text on error reporting, to mention Reporting failures
(as well as failures to action or execute Measurement Task &
Schedule)
o add some text about how to have Tasks running indefinitely
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o add that optionally a Report is not sent when there are no
Measurement Results
o add that a Measurement Task may create more than one Measurement
Result
o clarify /amend /expand that Reports include the "raw" Measurement
Results - any pre-processing is left for lmap2.0
o add some cautionary words about what if the Collector unexpectedly
doesn't hear from a MA
o add some extra words about the potential impact of Measurement
Tasks
o clarified various aspects of the privacy section
o updated references
o minor tweaks
11.3. From -02 to -03
o alignment with the Information Model
[I-D.burbridge-lmap-information-model] as this is agreed as a WG
document
o One-off and periodic Measurement Schedules are kept separate, so
that they can be updated independently
o Measurement Suppression in a separate sub-section. Can now
optionally include particular Measurement Tasks &/or Schedules to
suppress, and start/stop time
o for clarity, concept of Channel split into Control, Report and MA-
to-Controller Channels
o numerous editorial changes, mainly arising from a very detailed
review by Charles Cook
o
12. Informative References
[Bur10] Burkhart, M., Schatzmann, D., Trammell, B., and E. Boschi,
"The Role of Network Trace anonymisation Under Attack",
January 2010.
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[Q1741] Q.1741.7, , "IMT-2000 references to Release 9 of GSM-
evolved UMTS core network",
http://www.itu.int/rec/T-REC-Q.1741.7/en, November 2011.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, November 1987.
[RFC4101] Rescorla, E. and IAB, "Writing Protocol Models", RFC 4101,
June 2005.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122, July
2005.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, October 2008.
[I-D.ietf-lmap-use-cases]
Linsner, M., Eardley, P., Burbridge, T., and F. Sorensen,
"Large-Scale Broadband Measurement Use Cases", draft-ietf-
lmap-use-cases-01 (work in progress), December 2013.
[I-D.bagnulo-ippm-new-registry-independent]
Bagnulo, M., Burbridge, T., Crawford, S., Eardley, P., and
A. Morton, "A registry for commonly used metrics.
Independent registries", draft-bagnulo-ippm-new-registry-
independent-01 (work in progress), July 2013.
[I-D.ietf-homenet-arch]
Chown, T., Arkko, J., Brandt, A., Troan, O., and J. Weil,
"IPv6 Home Networking Architecture Principles", draft-
ietf-homenet-arch-11 (work in progress), October 2013.
[RFC6419] Wasserman, M. and P. Seite, "Current Practices for
Multiple-Interface Hosts", RFC 6419, November 2011.
[RFC6887] Wing, D., Cheshire, S., Boucadair, M., Penno, R., and P.
Selkirk, "Port Control Protocol (PCP)", RFC 6887, April
2013.
[RFC5533] Nordmark, E. and M. Bagnulo, "Shim6: Level 3 Multihoming
Shim Protocol for IPv6", RFC 5533, June 2009.
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[I-D.burbridge-lmap-information-model]
Burbridge, T., Eardley, P., Bagnulo, M., and J.
Schoenwaelder, "Information Model for Large-Scale
Measurement Platforms (LMAP)", draft-burbridge-lmap-
information-model-01 (work in progress), October 2013.
[RFC6235] Boschi, E. and B. Trammell, "IP Flow Anonymization
Support", RFC 6235, May 2011.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973, July
2013.
[I-D.ietf-ippm-lmap-path]
Bagnulo, M., Burbridge, T., Crawford, S., Eardley, P., and
A. Morton, "A Reference Path and Measurement Points for
LMAP", draft-ietf-ippm-lmap-path-01 (work in progress),
September 2013.
Authors' Addresses
Philip Eardley
British Telecom
Adastral Park, Martlesham Heath
Ipswich
ENGLAND
Email: philip.eardley@bt.com
Al Morton
AT&T Labs
200 Laurel Avenue South
Middletown, NJ
USA
Email: acmorton@att.com
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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
Ipswich
ENGLAND
Email: trevor.burbridge@bt.com
Paul Aitken
Cisco Systems, Inc.
96 Commercial Street
Edinburgh, Scotland EH6 6LX
UK
Email: paitken@cisco.com
Aamer Akhter
Cisco Systems, Inc.
7025 Kit Creek Road
RTP, NC 27709
USA
Email: aakhter@cisco.com
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