Internet Engineering Task Force (IETF) P. Eardley
Request for Comments: 7594 BT
Category: Informational A. Morton
ISSN: 2070-1721 AT&T Labs
M. Bagnulo
UC3M
T. Burbridge
BT
P. Aitken
Brocade
A. Akhter
Consultant
August
September 2015
A Framework for Large-Scale Measurement of Broadband Performance (LMAP)
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. This document
presents an overall framework for large-scale measurements. It also
defines terminology for LMAP (Large-Scale Measurement of Broadband
Performance).
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7594.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Outline of an LMAP-Based Measurement System . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 9
4. Constraints . . . . . . . . . . . . . . . . . . . . . . . . . 12
4.1. The Measurement System Is Under the Direction of a Single
Organisation . . . . . . . . . . . . . . . . . . . . . . 13
4.2. Each MA May Only Have a Single Controller at Any Point in
Time . . . . . . . . . . . . . . . . . . . . . . . . . . 13
5. Protocol Model . . . . . . . . . . . . . . . . . . . . . . . 13
5.1. Bootstrapping Process . . . . . . . . . . . . . . . . . . 14
5.2. Control Protocol . . . . . . . . . . . . . . . . . . . . 15
5.2.1. Configuration . . . . . . . . . . . . . . . . . . . . 15
5.2.2. Instruction . . . . . . . . . . . . . . . . . . . . . 16
5.2.3. Capabilities, Failure, and Logging Information . . . 20
5.3. Operation of Measurement Tasks . . . . . . . . . . . . . 22
5.3.1. Starting and Stopping Measurement Tasks . . . . . . . 22
5.3.2. Overlapping Measurement Tasks . . . . . . . . . . . . 24
5.4. Report Protocol . . . . . . . . . . . . . . . . . . . . . 24
5.4.1. Reporting of the Subscriber's Service Parameters . . 26
5.5. Operation of LMAP over the Underlying Packet Transfer
Mechanism . . . . . . . . . . . . . . . . . . . . . . . . 26
5.6. Items beyond the Scope of the Initial LMAP Work . . . . . 27
5.6.1. End-User-Controlled Measurement System . . . . . . . 28
6. Deployment Considerations . . . . . . . . . . . . . . . . . . 29
6.1. Controller and the Measurement System . . . . . . . . . . 29
6.2. Measurement Agent . . . . . . . . . . . . . . . . . . . . 30
6.2.1. Measurement Agent on a Networked Device . . . . . . . 30
6.2.2. Measurement Agent Embedded in a Site Gateway . . . . 30 31
6.2.3. Measurement Agent Embedded behind a Site NAT or
Firewall . . . . . . . . . . . . . . . . . . . . . . 31
6.2.4. Multihomed Measurement Agent . . . . . . . . . . . . 31
6.2.5. Measurement Agent Embedded in an ISP Network . . . . 32
6.3. Measurement Peer . . . . . . . . . . . . . . . . . . . . 32
6.4. Deployment Examples . . . . . . . . . . . . . . . . . . . 33
7. Security Considerations . . . . . . . . . . . . . . . . . . . 36
8. Privacy Considerations . . . . . . . . . . . . . . . . . . . 38
8.1. Categories of Entities with Information of Interest . . . 38
8.2. Examples of Sensitive Information . . . . . . . . . . . . 39
8.3. Different Privacy Issues Raised by Different Sorts of
Measurement Methods . . . . . . . . . . . . . . . . . . . 40
8.4. Privacy Analysis of the Communication Models . . . . . . 41
8.4.1. MA Bootstrapping . . . . . . . . . . . . . . . . . . 41
8.4.2. Controller <-> Measurement Agent . . . . . . . . . . 42
8.4.3. Collector <-> Measurement Agent . . . . . . . . . . . 43
8.4.4. Measurement Peer <-> Measurement Agent . . . . . . . 43
8.4.5. Measurement Agent . . . . . . . . . . . . . . . . . . 45
8.4.6. Storage and Reporting of Measurement Results . . . . 46
8.5. Threats . . . . . . . . . . . . . . . . . . . . . . . . . 46
8.5.1. Surveillance . . . . . . . . . . . . . . . . . . . . 46
8.5.2. Stored Data Compromise . . . . . . . . . . . . . . . 47
8.5.3. Correlation and Identification . . . . . . . . . . . 47
8.5.4. Secondary Use and Disclosure . . . . . . . . . . . . 48
8.6. Mitigations . . . . . . . . . . . . . . . . . . . . . . . 48
8.6.1. Data Minimisation . . . . . . . . . . . . . . . . . . 48
8.6.2. Anonymity . . . . . . . . . . . . . . . . . . . . . . 49
8.6.3. Pseudonymity . . . . . . . . . . . . . . . . . . . . 50
8.6.4. Other Mitigations . . . . . . . . . . . . . . . . . . 50
9. Informative References . . . . . . . . . . . . . . . . . . . 51
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 53 54
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 54
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 Measurement Agents (MAs). These MAs could be software-
based
software-based agents on PCs, embedded agents in consumer devices
(such as TVs or gaming consoles), embedded in service-provider-controlled service-provider-
controlled devices such as set-top boxes and home gateways, or simply
dedicated probes. MAs may also be embedded on a device that is part
of an ISP's network, such as a DSLAM (Digital Subscriber Line Access
Multiplexer), router, Carrier Grade NAT (Network Address Translator),
or ISP Gateway. It is expected that a measurement system could
easily encompass a few hundred thousand or even millions of such MAs.
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 in [RFC7536]. The LMAP
framework should be useful for these, as well as other use cases,
such as to help end users run diagnostic checks like a network speed
test.
The LMAP framework has three basic elements: Measurement Agents,
Controllers, and Collectors.
Measurement Agents (MAs) initiate the actual measurements, which are
called Measurement Tasks in the LMAP terminology. In principle,
there are no restrictions on the type of device in which the MA
function resides.
The Controller instructs one or more MAs and communicates the set of
Measurement Tasks an MA should perform and when. For example, it may
instruct an MA at a home gateway: "Measure the 'UDP latency' with
www.example.org; repeat every hour at xx.05". The Controller also
manages an MA by instructing it on 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. The communications between these three
LMAP functions are structured according to a Control Protocol and a
Report Protocol.
The desirable features for design goals are the following large-scale Measurement Systems that we
are designing for are: System
features:
o Standardised - in terms of the Measurement Tasks that they
perform, the components, the data models, and the protocols for
transferring information between the components. Amongst other
things, standardisation enables meaningful comparisons of
measurements made of the same metric Metric at different times and
places, and provides the operator of a Measurement System with
criteria for evaluation of the different solutions that can be
used for various purposes including buying decisions (such as
buying the various components from different vendors). Today's
systems are proprietary in some or all of these aspects.
o Large-scale - [RFC7536] envisages Measurement Agents in every home
gateway and edge device such as set-top boxes and tablet
computers, and located throughout the Internet as well [RFC7398].
It is expected that a Measurement System could easily encompass a
few hundred thousand or even millions of 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 Measurement Agents
from different vendors that are in wired and wireless networks,
can execute different sorts of Measurement Tasks, are on devices
with IPv4 or IPv6 addresses, and so on.
o Privacy Respecting - the protocols and procedures should respect
the sensitive information of all those involved in measurements.
2. Outline of an LMAP-Based Measurement System
In this section, we provide an overview of the whole Measurement
System. New LMAP-specific terms are capitalised; Section 3 provides
a terminology section with a compilation of all the LMAP terms and
their definitions. Section 4 onwards considers the LMAP components
in more detail.
Other LMAP specifications will define an Information Model, the
associated Data Models, and select/extend one or more protocols for
the secure communication: firstly, a Control Protocol, for a
Controller to instruct Measurement Agents regarding which performance
metrics
Metrics to measure, when to measure them, and how/when to report the
measurement results to a Collector; secondly, a Report Protocol, for
a Measurement Agent to report the results to the Collector.
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 initial LMAP work.
The MA performs Measurement Tasks. One possibility is that the MA
observes existing traffic. Another possibility is for the MA to
generate (or receive) traffic specially created for the purpose and
measure some metric Metric associated with its transfer. Figure 1 includes
both possibilities (in practice, it may be more usual for an MA to do
one) whilst Section 6.4 shows some examples of possible arrangements
of the components.
The MAs are pieces of code that can be executed in specialised
hardware (hardware probe) or on a general-purpose device (like a PC
or mobile phone). A device with a Measurement Agent may have
multiple physical interfaces (Wi-Fi, Ethernet, DSL (Digital
Subscriber Line); and non-physical interfaces such as PPPoE (Point-
to-Point
(Point-to-Point Protocol over Ethernet) or IPsec) and the Measurement
Tasks may specify any one of these.
The Controller manages an MA through use of the Control Protocol,
which transfers the Instruction to the MA. This describes the
Measurement Tasks the MA should perform and when. For example the
Controller may instruct an MA at a home gateway: "Count the number of
TCP SYN packets observed in a 1 minute interval; repeat every hour at
xx.05 + Unif[0,180] seconds". The Measurement Schedule determines
when the Measurement Tasks are executed. The Controller also manages
an MA by instructing it on 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."
The Report Schedule determines when the Reports are uploaded to the
Collector. The Measurement Schedule and Report Schedule can define
one-off (non-recurring) actions (for example, "Do measurement now",
"Report as soon as possible"), as well as recurring ones.
The Collector accepts a Report from an MA with the Measurement
Results from its Measurement Tasks. It then provides the Results to
a repository.
A Measurement Method defines how to measure a Metric of interest. It
is very useful to standardise Measurement Methods, 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 [IPPM-REG] so that a Metric and its
associated Measurement Method can be referred to simply by its
identifier in the registry. The registry will hopefully be
referenced by other standards organisations. The Measurement Methods
may be defined by the IETF, locally, or by some other standards body.
Broadly speaking there are two types of Measurement Methods. In both
types, a Measurement Agent measures a particular Observed Traffic
Flow. It may involve a single MA simply observing existing traffic
-- for example, the Measurement Agent could count bytes or calculate
the average loss for a particular flow. On the other hand, a
Measurement Method may observe traffic created specifically for the
purpose of measurement. This requires multiple network entities,
which perform different roles. For example, to measure the round
trip delay one possible Measurement Method would consist of an MA
sending an ICMP (Internet Control Message Protocol) ECHO request
("ping") to a responder in the Internet. In LMAP terms, the
responder is termed a Measurement Peer (MP), meaning that it helps
the MA but is not managed by the Controller. Other Measurement
Methods involve a second MA, with the Controller instructing the MAs
in a coordinated manner. Traffic generated specifically as part of
the Measurement Method is termed Measurement Traffic; in the ping
example, it is the ICMP ECHO Requests and Replies. The protocols
used for the Measurement Traffic are out of the scope of initial LMAP
work and fall within the scope of other IETF WGs such as IPPM (IP
Performance Metrics).
A Measurement Task is the action performed by a particular MA at a
particular time, as the specific instance of its role in a
Measurement Method. LMAP is mainly concerned with Measurement Tasks,
for instance in terms of its Information Model and Protocols.
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 to assess Metrics, 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 IETF
work, although it is certainly facilitated by the IETF's work.
Both control and report messages are transferred over a secure
Channel. A Control Channel is between the Controller and an MA; the
Control Protocol delivers Instruction Messages to the MA and
Capabilities, Failure, and Logging Information in the reverse
direction. A Report Channel is between an MA and Collector, and the
Report Protocol delivers Reports to the Collector.
Finally, we introduce several components that are outside the scope
of initial LMAP work that 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. As shown in Figure 1, these components are: the
bootstrapper, Subscriber parameter database, data analysis tools, and
Results repository.
The MA needs to be bootstrapped with initial details about its
Controller, including authentication credentials. The LMAP work
considers the Bootstrap process, since it affects the Information
Model. However, LMAP 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 (Simple Network Management Protocol),
NETCONF (Network Configuration Protocol), or (for Home Gateways) CPE
WAN Management Protocol (CWMP) from the Auto Configuration Server
(ACS) (as specified in TR-069 [TR-069]).
A Subscriber parameter database contains information about the line,
such as the customer's broadband contract (perhaps 2, 40, or 80
Mb/s), the line technology (DSL or fibre), the time zone in which 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 80 Mb/s contract may overwhelm a 2 Mb/s
line.
A Results repository records all Measurement Results in an equivalent
form, for example an SQL (Structured Query Language) database, so
that they can easily be accessed by the data analysis tools.
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 data analysis tools also need to understand the Subscriber's
service information, for example, the broadband contract.
+--------+ +-----------+ +-----------+ ^
|End user| | | Observed | End user | |
| |<-----|-----------|---Traffic--->| | |
| | | | Flow | | |
| | | | | | Non-LMAP
| | | | Measurement | | Scope
| | | |<--Traffic--->| | |
+--------+ | | +-----------+ |
................|...........|.................................V
<MP> |Measurement| <MP> ^
|Agent: | |
|LMAP | |
+----------->|interface | |
| +-----------+ |
| ^ | LMAP
| Instruction | | Report Scope
| (over Control | | (over Report Channel) |
| Channel) | +-----------------------+ |
| | | |
| | | |
| | v |
| +------------+ +------------+ |
| | Controller | | Collector | |
| +------------+ +------------+ v
| ^ ^ | ^
| | | | |
| | +--------+ | |
| | | v |
+------------+ +----------+ +--------+ +----------+ |
|Bootstrapper| |Subscriber|--->| data |<---| Results | Non-
+------------+ |parameter | |analysis| |repository| LMAP
|database | | tools | +----------+ Scope
+----------+ +--------+ |
|
v
MP: Measurement Peer
Figure 1: Schematic of main elements of an LMAP-based Measurement
System (showing the elements in and out of the scope of initial LMAP
work)
3. Terminology
This section defines terminology for LMAP. Please note that defined
terms are capitalised throughout.
Bootstrap: A process that integrates a Measurement Agent into a
Measurement System.
Capabilities: Information about the performance measurement
capabilities of the MA, in particular the Measurement Method roles
and measurement protocol roles that it can perform, and the device
hosting the MA, for example its interface type and speed, but not
dynamic information.
Channel: A bidirectional logical connection that is defined by a
specific Controller and MA, or Collector and MA, plus associated
security.
Collector: A function that receives a Report from an MA.
Configuration: A process for informing the MA about its MA-ID,
(optional) Group-ID, and Control Channel.
Controller: A function that provides a Measurement Agent with its
Instruction.
Control Channel: A Channel between a Controller and an MA over which
Instruction Messages and Capabilities, Failure, and Logging
Information are sent.
Control Protocol: The protocol delivering Instruction(s) from a
Controller to a Measurement Agent. It also delivers Capabilities,
Failure, and Logging Information from the Measurement Agent to the
Controller. It can also be used to update the MA's Configuration.
It runs over the Control Channel.
Cycle-ID: 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 for a Metric 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 [RFC3444].
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 take
action or execute an Instruction, whether concerning Measurement
Tasks or Reporting.
Group-ID: An identifier of a group of MAs.
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
[RFC3444].
Input Parameter: A parameter whose value is left open by the Metric
and its 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 Task.
Instruction: The description of Measurement Tasks for an MA to
perform and the details of the Report for it to send. It is the
collective description of the Measurement Task configurations, the
configuration of the Measurement Schedules, the configuration of the
Report Channel(s), the configuration of Report Schedule(s), and the
details of any Suppression.
Instruction Message: The message that carries an Instruction from a
Controller to a Measurement Agent.
Logging Information: Information about the operation of the
Measurement Agent, which may be useful for debugging.
Measurement Agent (MA): The function that receives Instruction
Messages from a Controller and operates the Instruction by executing
Measurement Tasks (using protocols outside the scope of the initial
LMAP work and perhaps in concert with one or more other Measurement
Agents or Measurement Peers) and (if part of the Instruction) by
reporting Measurement Results to a Collector or Collectors.
Measurement Agent Identifier (MA-ID): a Universally Unique IDentifier
[RFC4122] that identifies a particular MA and is configured as part
of the Bootstrapping process.
Measurement Method: The process for assessing the value of a Metric;
the process of measuring some performance or reliability parameter Metric
associated with the transfer of traffic.
Measurement Peer (MP): The function that assists a Measurement Agent
with Measurement Tasks and does not have an interface to the
Controller or Collector.
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 System: The set of LMAP-defined and related components
that are operated by a single organisation, for the purpose of
measuring performance aspects of the network.
Measurement Task: The action performed by a particular Measurement
Agent that consists of the single assessment of a Metric through
operation of a Measurement Method role at a particular time, with all
of the role's Input Parameters set to specific values.
Measurement Traffic: the packet(s) generated by some types of
Measurement Method that involve measuring some parameter associated
with the transfer of the packet(s).
Metric: The quantity related to the performance and reliability of
the network that we'd like to know the value of.
Observed Traffic Flow: In RFC 7011 [RFC7011], a Traffic Flow (or
Flow) is defined as "a set of packets or frames passing an
Observation Point in the network during a certain time interval. All
packets belonging to a particular Flow have a set of common
properties," such as packet header fields, characteristics, and
treatments. A Flow measured by the LMAP system is termed an Observed
Traffic Flow. Its properties are summarised and tabulated in
Measurement Results (as opposed to raw capture and export).
Report: The set of 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 Channel between a Collector and an MA over which
Report messages are sent.
Report Protocol: The protocol delivering Report(s) from a Measurement
Agent to a Collector. It runs over the Report Channel.
Report Schedule: The schedule for sending Reports to a Collector.
Subscriber: An entity (associated with one or more users) that is
engaged in a subscription with a service provider.
Suppression: The temporary cessation of Measurement Tasks.
4. Constraints
The LMAP framework makes some important assumptions, which constrain
the scope of the initial LMAP work.
4.1. The 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 for any impact that its
measurements have on a user's quality of experience and privacy.
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
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
An MA is instructed by one Controller and is in one Measurement
System. The constraint avoids different Controllers giving an 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 MAs before deployment to ensure that the end-user
experience is not impacted (due to CPU, memory, or broadband-product
constraints). However, a Measurement System may have several
Controllers.
5. 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 address?
2. What messages are being transmitted and what do they mean?
3. What are the important, but not obvious [sic], 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 Instruction Messages from a
Controller to an MA (amongst other things).
o the actual Measurement Tasks, which measure some performance or
reliability parameter(s) Metric(s) associated with the transfer of packets.
o a Report Protocol, which delivers Reports containing the
Measurement Results from an MA to a Collector.
The figures show the various LMAP messages and use the following
conventions:
o (optional): indicated by round brackets
o [potentially repeated]: indicated by square brackets
The protocol model is closely related to the Information Model
[LMAP-INFO], which is the abstract definition of the information
carried by the protocol. (If there is any difference between this
document and the Information Model, the latter is definitive.) The
purpose of both is to provide a protocol and device-independent view,
which can be implemented via specific protocols. LMAP defines 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.
5.1. Bootstrapping Process
The primary purpose of bootstrapping Bootstrapping is to enable an MA to be
integrated into a Measurement System. The MA retrieves information
about itself (like its identity in the Measurement System) and about
the Controller, the Controller learns information about the MA, and
they learn about security information to communicate (such as
certificates and credentials).
Whilst this memo considers the Bootstrapping process, it is beyond
the scope of initial LMAP work to define a Bootstrap mechanism, as it
depends on the type of device and access.
As a result of the Bootstrapping process, the MA learns the following
information ([LMAP-INFO] defines the consequent list of information
elements):
o its identifier, either its MA-ID or a device identifier such as
one of its Media Access Controls (MACs) Control (MAC) addresses or both.
o (optionally) a Group-ID, shared by several MAs and could be useful
for privacy reasons. For instance, reporting the Group-ID and not
the MA-ID could hinder tracking of a mobile device.
o the Control Channel, which is defined by:
* the address that identifies the Control Channel, such as the
Controller's FQDN (Fully Qualified Domain Name) [RFC1035]).
* security information (for example, to enable the MA to decrypt
the Instruction Message and encrypt messages sent to the
Controller).
The details of the Bootstrapping process are device/access specific.
For example, the information could be in the firmware, manually
configured, or transferred via a protocol like that described in
TR-069 [TR-069]. There may be a multi-stage process where the MA
contacts a 'hard-coded' address, which replies with the bootstrapping Bootstrapping
information.
The MA must learn its MA-ID before getting an Instruction, either
during Bootstrapping or via Configuration (Section 5.2.1).
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 (Section 5.2.2). The Measurement Agent then acts
on the Instruction autonomously. The Control Protocol also enables
the MA to inform the Controller about its Capabilities and any
Failure and Logging Information (Section 5.2.3). Finally, the
Control Protocol allows the Controller to update the MA's
Configuration.
5.2.1. Configuration
Configuration allows the Controller to update the MA about some or
all of the information that it obtained during the Bootstrapping
process: the MA-ID, the (optional) Group-ID, and the Control Channel.
Figure 2 outlines the Configuration process. The Measurement System
might use Configuration for several reasons. For example, the
Bootstrapping process could 'hard code' the MA with details of an
initial Controller, and then the initial Controller could configure
the MA with details about the Controller that sends Instruction
Messages. (Note that an MA only has one Control Channel, so it is
associated with only one Controller, at any moment.)
Note that an implementation may choose to combine Configuration
information and an Instruction Message into a single message.
+-----------------+ +-------------+
| | | Measurement |
| Controller |===================================| Agent |
+-----------------+ +-------------+
Configuration information: ->
(MA-ID),
(Group-ID),
(Control Channel)
<- Response(details)
MA: Measurement Agent
Figure 2: Outline of Configuration
5.2.2. Instruction
The Instruction is the description of the Measurement Tasks for a
Measurement Agent to do and the details of the Measurement Reports
for it to send. Figure 3 outlines the Instruction process. In order
to update the Instruction, the Controller uses the Control Protocol
to send an Instruction Message over the Control Channel.
+-----------------+ +-------------+
| | | Measurement |
| Controller |===================================| Agent |
+-----------------+ +-------------+
Instruction: ->
[(Measurement Task configuration
URI of Metric(
[Input Parameter],
(role)
(interface),
(Cycle-ID)
(measurement point)),
(Report Channel),
(Schedule),
(Suppression information)]
<- Response(details)
Figure 3: Outline of Instruction
The Instruction defines the following information ([LMAP-INFO]
defines the consequent list of information elements):
o the Measurement Task configurations, each of which needs:
* the Metric, specified as a URI to a registry entry; it includes
the specification of a Measurement Method. The registry could
be defined by a standards organisation or locally by the
operator of the Measurement System. Note that, at the time of
writing, the IETF is working on such a registry specification
[IPPM-REG].
* the Measurement Method role. For some Measurement Methods,
different parties play different roles; for example, an iperf
sender and receiver (see Section 6.4). Each Metric and its
associated Measurement Method will describe all measurement
roles involved in the process.
* a boolean flag (suppress or do-not-suppress) indicating if such
a Measurement Task is impacted by a Suppression message (see
Section 5.2.2.1). Thus, the flag is an Input Parameter.
* any Input Parameters that need to be set for the Metric and the
Measurement Method. For example, the address of a Measurement
Peer (or other Measurement Agent) that may be involved in a
Measurement Task, or traffic filters associated with the
Observed Traffic Flow.
* the interface to use (if not defined, then the default
interface is used), if the device with the MA has multiple
interfaces.
* optionally, a Cycle-ID.
* optionally, the measurement point designation [RFC7398] of the
MA and, if applicable, of the MP or other MA. This can be
useful for reporting.
o configuration of the Schedules, each of which needs:
* the timing of when the Measurement Tasks are to be performed or
the Measurement Reports are to be sent. Possible types of
timing are periodic, calendar-based periodic, one-off
immediate, and one-off at a future time.
o configuration of the Report Channel(s), each of which needs:
* the address of the Collector, for instance its URL.
* security for this Report Channel, for example, the X.509
certificate.
o Suppression information, if any (see Section 5.2.2.1).
A single Instruction Message may contain some or all of the above
parts. The finest level of granularity possible in an Instruction
Message is determined by the implementation and operation of the
Control Protocol. For example, a single Instruction Message may add
or update an individual Measurement Schedule -- or it may only update
the complete set of Measurement Schedules; a single Instruction
Message may update both Measurement Schedules and Measurement Task
configurations -- or only one at a time; and so on. However,
Suppression information always replaces (rather than adds to) any
previous Suppression information.
The MA informs the Controller that it has successfully understood the
Instruction Message, or that it cannot take action on the Instruction
-- for example, if it doesn't include a parameter that is mandatory
for the requested Metric and Measurement Method, or if it is missing
details of the target Collector.
The Instruction Message instructs 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.
5.2.2.1. Suppression
The Instruction may include Suppression information. The main
motivation for Suppression is to enable the Measurement System to
eliminate Measurement Traffic, because there is some unexpected
network issue, for example. There may be other circumstances when
Suppression is useful, for example, to eliminate inessential
Reporting traffic (even if there is no Measurement Traffic).
Figure 4 outlines the Suppression process.
The Suppression information may include any of the following optional
fields:
o a set of Measurement Tasks to suppress; the others are not
suppressed. For example, this could be useful if a particular
Measurement Task is overloading a Measurement Peer with
Measurement Traffic.
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 Measurement
Tasks and the other with less critical ones that create a lot of
Measurement Traffic, in which case it may only want to suppress
the second.
o a set of Reporting Schedules to suppress; the others are not
suppressed. This can be particularly useful in the case of a
Measurement Method that doesn't generate Measurement Traffic; it
may need to continue observing traffic flows but temporarily
suppress Reports due to the network footprint of the Reports.
o if all the previous fields are included then the MA suppresses the
union -- in other words, it suppresses the set of Measurement
Tasks, the set of Measurement Schedules, and the set of Reporting
Schedules.
o if the Suppression information includes neither a set of
Measurement Tasks nor a set of Measurement Schedules, then the MA
does not begin new Measurement Tasks that have the boolean flag
set to suppress; however, the MA does begin new Measurement Tasks
that have the flag set to do-not-suppress.
o a start time, at which Suppression begins. If absent, then
Suppression begins immediately.
o an end time, at which Suppression ends. If absent, then
Suppression continues until the MA receives an Un-suppress
message.
o a demand that the MA immediately end on-going Measurement Task(s)
that are tagged for Suppression. (Most likely it is appropriate
to delete the associated partial Measurement Result(s).) This
could be useful in the case of a network emergency so that the
operator can eliminate all inessential traffic as rapidly as
possible. If absent, the MA completes on-going Measurement Tasks.
An Un-suppress message instructs the MA to no longer suppress,
meaning that the MA once again begins new Measurement Tasks,
according to its Measurement Schedule.
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 an MA (instead,
some kind of management action is suggested).
+-----------------+ +-------------+
| | | Measurement |
| Controller |==============================| Agent |
+-----------------+ +-------------+
Suppress:
[(Measurement Task), ->
(Measurement Schedule),
(start time),
(end time),
(on-going suppressed?)]
Un-suppress ->
Figure 4: Outline of Suppression
5.2.3. Capabilities, Failure, and Logging Information
The Control Protocol also enables the MA to inform the Controller
about various information, such as its Capabilities and any Failures.
Figure 5 outlines the process for Capabilities, Failure, and Logging
Information. It is also possible to use a device-specific mechanism,
which is beyond the scope of the initial LMAP work.
Capabilities are information about the MA that the Controller needs
to know in order to correctly instruct the MA, such as:
o the Measurement Method (roles) that the MA supports.
o the measurement protocol types and roles that the MA supports.
o the interfaces that the MA has.
o the version of the MA.
o the version of the hardware, firmware, or software of the device
with the MA.
o its Instruction (this could be useful if the Controller thinks
something has gone wrong and wants to check what Instruction the
MA is using).
o but not dynamic information like the currently unused CPU, memory,
or battery life of the device with the MA.
Failure Information concerns why the MA has been unable to execute a
Measurement Task or deliver a Report, for example:
o the Measurement Task failed to run properly because the MA
(unexpectedly) has no spare CPU cycles.
o the MA failed to record the Measurement Results because it
(unexpectedly) is out of spare memory.
o a Report failed to deliver Measurement Results because the
Collector (unexpectedly) is not responding.
o but not if a Measurement Task correctly doesn't start. For
example, the first step of some Measurement Methods is for the MA
to check that there is no cross-traffic.
Logging Information concerns how the MA is operating and may help
debugging, for example:
o the last time the MA ran a Measurement Task.
o the last time the MA sent a Measurement Report.
o the last time the MA received an Instruction Message.
o whether the MA is currently suppressing Measurement Tasks.
Capabilities, Failure, and Logging Information are sent by the MA,
either in response to a request from the Controller (for example, if
the Controller forgets what the MA can do or otherwise wants to
resynchronise what it knows about the MA), or on its own initiative
(for example, when the MA first communicates with a Controller or if
it becomes capable of a new Measurement Method). Another example of
the latter case is if the device with the MA re-boots, then the MA
should notify its Controller in case its Instruction needs to be
updated; 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.
+-----------------+ +-------------+
| | | Measurement |
| Controller |==================================| Agent |
+-----------------+ +-------------+
(Request Capabilities),
(Request Failure Information),
(Request Logging Information),
(Request Instruction) ->
<- (Capabilities),
(Failure Information),
(Logging Information),
(Instruction)
Figure 5: Outline of Capabilities, Failure, and Logging Information
5.3. Operation of Measurement Tasks
This LMAP framework is neutral to what the actual Measurement Task
is. It does not define Metrics and Measurement Methods; these are
defined elsewhere.
The MA carries out the Measurement Tasks as instructed, unless it
gets an updated Instruction. The MA acts autonomously, in terms of
operation of the Measurement Tasks and reporting of the Results; it
doesn't do a 'safety check' with the Controller to ask whether it
should still continue with the requested Measurement Tasks.
The MA may operate Measurement Tasks sequentially or in parallel (see
Section 5.3.2).
5.3.1. Starting and Stopping Measurement Tasks
This LMAP framework does not define a generic start and stop process,
since the correct approach depends on the particular Measurement
Task; the details are defined as part of each Measurement Method.
This section provides some general hints. The MA does not inform the
Controller about Measurement Tasks starting and stopping.
Before beginning a Measurement Task, the MA may want to run a pre-
check.
pre-check. (The pre-check could be defined as a separate, preceding
Task or as the first part of a larger Task.)
For Measurement Tasks that observe existing traffic, action could
include:
o checking that there is traffic of interest.
o checking that the device with the MA has enough resources to
execute the Measurement Task reliably. Note that the designer of
the Measurement System should ensure that the device's resources
are normally sufficient to comfortably operate the Measurement
Tasks.
For Measurement Tasks that generate Measurement Traffic, a pre-check
could include:
o the MA checking that there is no cross-traffic. In other words, a
check that the end-user isn't already sending traffic.
o the MA checking with the Measurement Peer (or other Measurement
Agent) involved in the Measurement Task that it can handle a new
Measurement Task. For example, the Measurement Peer may already
be handling many Measurement Tasks with other MAs.
o sending traffic that probes the path to check it isn't overloaded.
o checking that the device with the MA has enough resources to
execute the Measurement Task reliably.
Similar checks may continue during the Measurement Task, in
particular for a Measurement Task that is long-running and/or creates
a lot of Measurement Traffic. If, for example, the check detects
that the end-user has started sending traffic, then the Measurement
Task can be abandoned. A Measurement Task could also be abandoned in
response to a "suppress" message (see Section 5.2.2.1). 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 (Two-Way Active Measurement Protocol) Stop-Sessions
command [RFC5357].
The Controller may want an MA to run the same Measurement Task
indefinitely (for example, "run the 'upload speed' Measurement Task
once an hour until further notice"). To prevent the MA continuously
generating traffic after a Controller has permanently failed (or
communications with the Controller have failed), the MA can be
configured with a time limit; if the MA doesn't hear from the
Controller for this length of time, then it stops operating
Measurement Tasks.
5.3.2. Overlapping Measurement Tasks
An MA may start a new Measurement Task before another Measurement
Task has completed. This may be intentional (the way that the
Measurement System has designed the Measurement Schedules), but it
could also be unintentional -- for instance, if a Measurement Task
has a 'wait for X' step that pauses for an unexpectedly long time.
This document makes no assumptions about the impact of one
Measurement Task on another.
The operator of the Measurement System can handle (or not)
overlapping Measurement Tasks in any way they choose -- it is a
policy or implementation issue and not the concern of LMAP. Some
possible approaches are: to configure the MA to not begin the second
Measurement Task; to start the second Measurement Task as usual; for
the action to be an Input Parameter of the Measurement Task; and so
on.
It may be important for the Measurement Report to include the fact
that the Measurement Tasks overlapped.
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, along with
the context in which they were obtained. Figure 6 outlines the
Report process.
+-----------------+ +-------------+
| | | Measurement |
| Collector |==================================| Agent |
+-----------------+ +-------------+
<- Report:
[MA-ID &/or Group-ID],
[Measurement Result],
[details of Measurement Task],
(Cycle-ID)
ACK ->
MA: Measurement Agent
Figure 6: Outline of the Report
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. In general, the time is simply the MA's best estimate
and there is no guarantee on the accuracy or granularity of the
information. It is possible that some specific analysis of a
particular Measurement Method's Results will impose timing
requirements.
o the details of the Measurement Task (to avoid the Collector having
to ask the Controller for this information later), for example,
the interface used for the measurements.
o the Cycle-ID, if one was included in the Instruction.
o perhaps the Subscriber's service parameters (see Section 5.4.1).
o the measurement point designation of the MA and, if applicable,
the MP or other MA, if the information was included in the
Instruction. This numbering system is defined in [RFC7398] and
allows a Measurement Report to describe the path measured
abstractly (for example, "from a measurement agent at a home
gateway to a measurement peer at a DSLAM"). Also, the MA can
anonymise results by including measurement point designations
instead of IP addresses (Section 8.6.2).
The MA sends Reports as defined by the Instruction. The Instruction
may tell the MA to report the same Results to more than one
Collector, or to report a different subset of Results to different
Collectors. Also, 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 an MA to:
o label, or perhaps not include, Measurement Results impacted by,
for instance, cross-traffic or a Measurement Peer (or other
Measurement Agent) being busy.
o label Measurement Results obtained by a Measurement Task that
overlapped with another.
o not report the Measurement Results if the MA believes that they
are invalid.
o detail when Suppression started and ended.
As discussed in Section 6.1, data analysis of the Results should
carefully consider potential bias from any Measurement Results that
are not reported, or from Measurement Results that are reported but
may be invalid.
5.4.1. Reporting of the Subscriber's Service Parameters
The Subscriber's service parameters are information about his/her
broadband contract, line rate and so on. Such information is likely
to be needed to help analyse the Measurement Results, for example to
help decide whether the measured download speed is reasonable.
The information could be transferred directly from the Subscriber
parameter database to the data analysis tools. If the Subscriber's
service parameters are available to the MAs, they could be reported
with the Measurement Results in the Report Protocol. How (and if)
the MA knows such information is likely to depend on the device type.
The MA could either include the information in a Measurement Report
or separately.
5.5. Operation of LMAP over the Underlying Packet Transfer Mechanism
The above sections have described LMAP's protocol model. Other
specifications will define the actual Control and Report Protocols,
possibly operating over an existing protocol, such as REST-style
[REST] HTTP(S). It is also possible that a different choice is made
for the Control and Report Protocols, for example NETCONF-YANG
[RFC6241] and IPFIX (Internet Protocol Flow Information Export)
[RFC7011], respectively.
From an LMAP perspective, the Controller needs to know that the MA
has received the Instruction Message, or at least that it needs to be
re-sent as it may have failed to be delivered. Similarly the MA
needs to know about the delivery of Capabilities, Failure, and
Logging Information to the Controller and Reports to the Collector.
How this is done depends on the design of the Control and Report
Protocols and the underlying packet transfer mechanism.
For the Control Protocol, the underlying packet transfer mechanism
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 an MA behind a
NAT or firewall (as is typical for an MA on an end-user's device)
so that it can initiate the communications. It also seems
attractive for an MA on a mobile device, where the Controller
might not know how to reach the MA. A pull mechanism is likely to
require that the MA 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 packet transfer mechanism
could be:
o a 'push' protocol (that is, from the MA to the Collector)
o perhaps supplemented by the ability for the Collector to 'pull'
Measurement Results from an MA.
5.6. Items beyond the Scope of the Initial LMAP Work
There are several potential interactions between LMAP elements that
are beyond the scope of the initial LMAP work, which are as follows:
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; or if the Collector unexpectedly does not hear from an
MA, then the Measurement System may want to trigger the
Controller to send a fresh Instruction Message to the MA.
3. It does not define coordination between different Measurement
Systems. For example, it does not define the interaction of an
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 initial LMAP work. 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 Measurement Traffic of one
MA is treated by the other MA just like any other end-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 that this
is a policy issue and would be dealt with through a code of
conduct for instance.
5. It does not define how to analyse Measurement Results, including
how to interpret missing Results.
6. It does not specifically define a end-user-controlled Measurement
System, see Section 5.6.1.
5.6.1. End-User-Controlled Measurement System
This framework 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 end-user-
controlled Measurement System. There are at least two ways this
could happen (they have various pros and cons):
1. an end-user could somehow request the ISP-run (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.
2. an end-user 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 end-user-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. A Measurement Peer (or other MA involved in a
Measurement Task) 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 end-user to initiate
the Measurement Task(s). The mechanism is outside the scope of the
initial LMAP work, 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
privacy in Section 8.
6. Deployment Considerations
6.1. Controller and the Measurement System
The Controller should understand both the MA's LMAP Capabilities (for
example, what Metrics and Measurement Methods it can perform) and the
MA's other capabilities like processing power and memory. This
allows the Controller to ensure that the Measurement Schedule of
Measurement 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. 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. Some Tasks may be complementary. For
example, one Task may be followed by a traceroute Task to the same
destination address, in order to learn the network path that was
measured.
The Controller should ensure that the Measurement Tasks do not have
an adverse effect on the end user. Tasks, especially those that
generate a substantial amount of Measurement Traffic, will often
include a pre-check that the user isn't already sending traffic
(Section 5.3.1). Another consideration is whether Measurement
Traffic will impact a Subscriber's bill or traffic cap.
A Measurement System may have multiple Controllers (but note the
overriding principle that a single MA be 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 (for
example, home gateways, tablets) or locations (for example, Ipswich,
Edinburgh, Paris), for load balancing or to cope with failure of one
Controller.
The measurement system also needs to consider carefully how to
interpret missing Results. The correct interpretation depends on why
the Results are missing (perhaps related to measurement Suppression
or delayed Report submission) and potentially on the specifics of the
Measurement Task and Measurement Schedule. For example, an Observed
Traffic Flow may be empty, but the Measurement Report may still be
sent according to the Report Schedule.
6.2. Measurement Agent
The MA should be cautious about resuming Measurement Tasks if it
reboots or has been offline for some time, as its Instruction may be
stale. In the former case, it also needs to ensure that its clock
has reset correctly, so that it interprets the Schedule correctly.
If the MA runs out of storage space for Measurement Results or can't
contact the Controller, then the appropriate action is specific to
the device and Measurement System.
The Measurement Agent could take a number of forms. For example, an
MA could be a dedicated probe or software on a PC; it could also be
embedded into an appliance or even embedded into a gateway. A single
site (for example, home, branch office, etc.) that is participating
in a measurement could make use of one or multiple Measurement Agents
or Measurement Peers in a single measurement.
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.
6.2.1. Measurement Agent on a Networked Device
An MA may be embedded on a device that is directly connected to the
network, such as an MA on a smartphone. Other examples include an MA
downloaded and installed on a subscriber's laptop computer or tablet
when the network service is provided on wired or other wireless radio
technologies, such as Wi-Fi.
6.2.2. Measurement Agent Embedded in a Site Gateway
One of the better places the Measurement Agent could be deployed is
embedded within the site gateway (for example, a home router or the
edge router of a branch office in a managed service environment).
All site-to-ISP traffic would traverse through the gateway. So,
Measurement Methods that measure user traffic could easily be
performed. Similarly, due to this user traffic visibility, a
Measurement Method that generates Measurement Traffic could ensure it
does not 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 with Instructions. However, a Measurement Agent on
a site gateway (whether end-user or service-provider owned) will
generally not be directly available for over-the-top providers, the
regulator, end users, or enterprises.
6.2.3. Measurement Agent Embedded behind a Site NAT or 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 or firewall pin holing is configured. Configuring port
forwarding could use protocols such as the Port Control Protocol
[RFC6887], the CPE WAN Management Protocol [TR-069], or Universal
Plug and Play [UPnP]. To open a pin hole in the firewall, the
Measurement Agent could send keepalives towards the Controller (and
perhaps use these also as a network reachability test).
6.2.4. Multihomed Measurement Agent
If the device with the Measurement Agent is single homed, then there
is no confusion about what interface to measure. Similarly, if the
MA is at the gateway and the gateway only has a single WAN-side and a
single LAN-side interface, there is little confusion -- for
Measurement Methods that generate Measurement Traffic, the location
of the other MA or Measurement Peer determines whether the WAN or LAN
is measured.
However, the device with the Measurement Agent may be multihomed.
For example, a home or campus may be connected to multiple broadband
ISPs, such as a wired and wireless broadband provider, perhaps for
redundancy or load sharing. It may also be helpful to think of dual
stack IPv4 and IPv6 broadband devices as multihomed. More generally,
Section 3.2 of [RFC7368] describes dual-stack and multihoming
topologies that might be encountered in a home network, [RFC6419]
provides the current practices of multi-interfaces hosts, and the
Multiple Interfaces (mif) working group covers cases where hosts are
either directly attached (for example, physical or virtual) or
indirectly (for example, multiple default routers, etc.) to multiple
networks. In these cases, there needs to be clarity on which network
connectivity option is being measured.
One possibility is to have a Measurement Agent per interface. Then
the Controller's choice of MA determines which interface is measured.
However, if an MA can measure any of the interfaces, then the
Controller defines in the Instruction which interface the MA should
use for a Measurement Task. If the choice of interface is not
defined, then the MA uses the default one. Explicit definition is
preferred if the Measurement System wants to measure the performance
of a particular network, whereas using the default is better if the
Measurement System wants to include the impact of the MA's interface
selection algorithm. In any case, the Measurement Result should
include the network that was measured.
6.2.5. Measurement Agent Embedded in an ISP Network
An MA may be embedded on a device that is part of an ISP's network,
such as a router or switch. Usually the network devices with an
embedded MA will be strategically located, such as a Carrier-Grade
NAT or ISP Gateway. [RFC7398] gives many examples where an MA might
be located within a network to provide an intermediate measurement
point on the end-to-end path. Other examples include a network
device whose primary role is to host MA functions and the necessary
measurement protocol.
6.3. Measurement Peer
A Measurement Peer participates in some Measurement Methods. 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; or if the MA
monitors existing traffic, then the existing end points are
Measurement Peers.
A device may participate in some Measurement Methods as a Measurement
Agent and in others as a Measurement Peer.
Measurement Schedules should account for limited resources in a
Measurement Peer when instructing an MA to execute measurements with
a Measurement Peer. In some measurement protocols, such as [RFC4656]
and [RFC5357], the Measurement Peer can reject a measurement session
or refuse a control connection prior to setting up a measurement
session and so protect itself from resource exhaustion. This is a
valuable capability because the MP may be used by more than one
organisation.
6.4. Deployment Examples
In this section, we describe some deployment scenarios that are
feasible within the LMAP framework defined in this document.
A very simple example of a Measurement Peer (MP) is a web server from
which the MA downloads a web page (such as www.example.com) in order
to perform a speed test. The web server is an MP and from its
perspective the MA is just another client; the MP doesn't have a
specific function for assisting measurements. This is described in
Figure 7.
^
+------------------+ web traffic +----------------+ non-LMAP
| web client |<------------>| web server | Scope
| | +----------------+ |
...|..................|....................................V...
|MA:LMAP interface | <MP> ^
+------------------+ |
^ | |
Instruction | | Report |
| +-----------------+ |
| | |
| v LMAP
+------------+ +------------+ Scope
| Controller | | Collector | |
+------------+ +------------+ V
MA: Measurement Agent
MP: Measurement Peer
Figure 7: LMAP deployment example, with Web server as Measurement
Peer
Another example of an MP is a TWAMP Server and TWAMP Session-
Reflector.
Session-Reflector. This form of MP is deployed to assist the MAs
that perform TWAMP tests, where the MA is co-located with the TWAMP
Control-Client and Session-Sender. Another example, which was
described in Section 2, has a ping server as the Measurement Peer.
A further example is the case of a traceroute-like measurement. In
this case, for each packet sent, the router where the TTL expires is
performing the MP function. So for a given Measurement Task, there
is one MA involved and several MPs, one per hop.
In Figure 8, we depict the case of an OWAMP (One-Way Active
Measurement Protocol) Server and Session-Receiver acting as an MP.
In this case, the OWAMP Server conveys results back to the OWAMP
Fetch-Client, thus the MP conducts both control-plane and data-plane
communications with its OWAMP counterparts co-located with the MA.
+------------------+ OWAMP +-----------------+ ^
| OWAMP |<--control--->| | |
| control-client |-test-traffic>| OWAMP server & | non-LMAP
| fetch-client & |<----fetch----| session-receiver| Scope
| session-sender | | | |
| | +-----------------+ |
...|..................|.....................................v...
|MA:LMAP interface | <MP> ^
+------------------+ |
^ | |
Instruction | | Report |
| +-----------------+ |
| | |
| v LMAP
+------------+ +------------+ Scope
| Controller | | Collector | |
+------------+ +------------+ v
MA: Measurement Agent
MP: Measurement Peer
Figure 8: LMAP deployment example, with OWAMP server as Measurement
Peer
However, it is also possible to use two Measurement Agents when
performing one-way Measurement Tasks, as described in Figure 9. Both
MAs are instructed by the Controller: MA-1 to send the traffic and
MA-2 to measure the received traffic and send Reports to the
Collector. Note that the Measurement Task at MA-2 can listen for
traffic from MA-1 and respond multiple times without having to be
rescheduled.
+----------------+ +-------------------+ ^
| | | | non-LMAP
| iperf -u sender|-UDP traffic->| iperf -u receiver | Scope
| | | | v
...|................|..............|...................|........
| MA-1: | | MA-2: | ^
| LMAP interface | | LMAP interface | |
+----------------+ +-------------------+ |
^ ^ | |
Instruction | Instruction{Report} | | Report |
{Task, | +-------------------+ | |
Schedule} | | | |
| | v LMAP
+------------+ +------------+ Scope
| Controller | | Collector | |
+------------+ +------------+ v
MA: Measurement Agent
Figure 9: Schematic of LMAP-based Measurement System, with two
Measurement Agents cooperating to measure UDP traffic
Next, we consider Measurement Methods that meter the Observed Traffic
Flow. Traffic generated in one point in the network is flowing
towards a given destination and the traffic is observed in some point
along the path. One way to implement this is that the endpoints
generating and receiving the traffic are not instructed by the
Controller; hence they are MPs. The MA is located along the path
with a monitor function that measures the traffic. The MA is
instructed by the Controller to monitor that particular traffic and
to send the Report to the Collector. It is depicted in Figure 10.
+--------+ +------------------+ +--------+ ^
|End user| | monitor | Observed |End user| |
| |<--|------------------|--Traffic-->| | non-LMAP
| | | | Flow | | Scope
+--------+ | | +--------+ |
...|..................|............................v..
............|..................|............................v..
<MP> |MA:LMAP interface | <MP> ^
+------------------+ |
^ | |
Instruction | | Report |
| +-----------------+ |
| | |
| v LMAP
+------------+ +------------+ Scope
| Controller | | Collector | |
+------------+ +------------+ v
MA: Measurement Agent
MP: Measurement Peer
Figure 10: LMAP deployment example, with a Measurement Agent
monitoring traffic
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. Much of the general advice
contained in Section 6 of [RFC4656] is applicable here.
The process to upgrade the firmware in an MA is outside the scope of
the initial LMAP work, just as is the protocol to Bootstrap the MAs.
However, systems that provide remote upgrades must secure authorised
access and integrity of the process.
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 denial-of-service (DoS) attacks at targets, create a
platform for pervasive monitoring [RFC7258], 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). The
Instruction Messages also need to be encrypted to maintain
confidentiality, as the information might be useful to an attacker.
Reporting by the MA must be encrypted to maintain confidentiality, so
that only the authorised Collector can decrypt the results to prevent
the leakage of confidential or private information. Reporting must
also be authenticated (to ensure that it comes from a trusted MA and
that the MA reports to a genuine Collector) and not vulnerable to
tampering (which can be ensured through integrity and replay checks).
It must not be possible to fool an MA into injecting falsified data
and the results must also be held and processed securely after
collection and analysis. See Section 8.5.2 for additional
considerations on stored data compromise, and Section 8.6 on
potential mitigations for compromise.
Since Collectors will be contacted repeatedly by MAs using the Report
Protocol to convey their recent results, a successful attack to
exhaust the communication resources would prevent a critical
operation: reporting. Therefore, all LMAP Collectors should
implement technical mechanisms to:
o limit the number of reporting connections from a single MA
(simultaneous and established in some time period).
o limit the transmission rate from a single MA.
o limit the memory/storage consumed by a single MA's reports.
o efficiently reject reporting connections from unknown sources.
o separate resources if multiple authentication strengths are used,
where the resources should be separated according to each class of
strength.
A corrupted MA could report falsified information to the Collector.
Whether this can be effectively mitigated depends on the platform on
which the MA is deployed. However, where the MA is deployed on a
customer-controlled device, then the reported data is to some degree
inherently untrustworthy. Further, a sophisticated party could
distort some Measurement Methods, perhaps by dropping or delaying
packets for example. This suggests that the network operator should
be cautious about relying on Measurement Results for action such as
refunding fees if a service level agreement is not met.
As part of the protocol design, it will be decided how LMAP operates
over the underlying protocol (Section 5.5). The choice raises
various security issues, such as how to operate through a NAT and how
to protect the Controller and Collector from DoS attacks.
The security mechanisms described above may not be strictly necessary
if the network's design ensures the LMAP components and their
communications are already secured, for example potentially if they
are all part of an ISP's dedicated management network.
Finally, there are three other issues related to security: privacy
(considered in Section 8), availability, and "gaming the system".
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. Normally,
this potential issue is handled by a code of conduct. It is outside
the scope of the initial LMAP work to consider the issue.
8. Privacy Considerations
The LMAP work considers privacy 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 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.
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 that 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 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 discuss
data protection by 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 example, 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 that may be
measured or stored in a Measurement System, and that is to be kept
private by default in the LMAP core protocols.
Examples of Subscriber or authorised Internet user sensitive
information:
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 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 that could be
correlated with other pieces collected by an attacker (as discussed
in Section 8.5 on Threats).
8.3. Different Privacy Issues Raised by Different Sorts of Measurement
Methods
Measurement Methods raise different privacy issues depending on
whether they measure traffic created specifically for that purpose or
whether they measure user traffic.
Measurement Tasks conducted on user traffic store sensitive
information, 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). Such Measurement Tasks could reveal all the
websites a Subscriber visits and the applications and/or services
they use. This issue is not specific to LMAP. For instance, IPFIX
has discussed similar issues (see Section 11.8 of [RFC7011]), but
mitigations described in the sections below were considered beyond
their scope.
In contrast to Measurement Tasks conducted on user traffic, other
Measurement Tasks use traffic which is created specifically for the
purpose of measurement. Even if a user host generates Measurement
Traffic, there is limited sensitive information about the Subscriber
present and stored in the Measurement System:
o IP address in use (and possibly sub-IP addresses and names)
o Status as a study volunteer and Schedule of Measurement Tasks
On the other hand, for a service provider, the sensitive information
like Measurement Results is the same for all Measurement Tasks.
From the Subscriber perspective, both types of Measurement Tasks
potentially expose the description of Internet access service and
specific service parameters, such as the Subscriber rate and type of
access.
8.4. Privacy Analysis of the Communication Models
This section examines each of the protocol exchanges described at a
high level in Section 5 and some example Measurement Tasks, and it
identifies specific sensitive information that must be secured during
communication for each case. With the protocol-related sensitive
information identified, we 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.
Although the specification of mechanisms for bootstrapping Bootstrapping the MA are
beyond the scope of the initial LMAP work, designers should recognise
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 Metrics with
associated Measurement Methods (for example, to 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 the MA's identifier (MA-ID)
o the address that identifies the Control Channel, such as the
Controller's FQDN
o Security information for the Control Channel
During the Bootstrap process for an MA located at a single
Subscriber's service demarcation point, the MA receives an MA-ID,
which is a persistent pseudonym for the Subscriber. 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 that 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.
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 an 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 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
A Measurement Method involving Measurement Traffic raises potential
privacy issues, although the specification of the mechanisms is
beyond the scope of the initial LMAP work. The high-level
communications model below illustrates the various exchanges to
execute such a Measurement Method 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
Measurement Method. It may involve sending Measurement Traffic from
the Measurement Peer to MA, MA to Measurement Peer, or both.
Similarly, a second (or more) MAs may be involved. (Note: For
simplicity, Figure 11 and the description don't show the non-LMAP
functionality that is associated with the transfer of the Measurement
Traffic and is located at the devices with the MA and MP.)
_________________ _________________
| | | |
|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 ->
Measurement Traffic <> Measurement Traffic
(may/may not be encrypted) (may/may not be encrypted)
<- (Stop Measurement Task)
Measurement Results ->
(if applicable)
<- ACK, Close
Figure 11: Interactions between Measurement Peer and Measurement
Agent
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 Measurement Traffic
(usually a set of timestamps).
The Measurement Peer may be able to use traffic analysis (perhaps
combined with traffic injection) to obtain interesting insights about
the Subscriber. As a simple example, if the Measurement Task
includes a pre-check that the end user isn't already sending traffic,
the Measurement Peer may be able to deduce when the Subscriber is
away on holiday.
If the 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. Measurement Agent
Some Measurement Methods only involve a single Measurement Agent
observing existing traffic. They raise potential privacy issues,
although the specification of the mechanisms is beyond the scope of
the initial LMAP work.
The high-level communications model shown in Figure 12 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 measurement of DNS Response Time, which
most frequently uses UDP transport. (Note: For simplicity, Figure 12
and its description don't do not show the non-LMAP functionality that is
associated with the transfer (export) of the observed Measurement
Traffic and is
located at beyond the measurement devices located with the MA.)
_________________ ____________
| | | |
| DNS Server |=========== NAT ? ==========*=======| User client|
|_________________| ^ |____________|
______|_______
| |
| Measurement |
| Agent |
|______________|
<- Name Resolution Required
(MA+MP IPAddrs,
Desired Domain Name)
Return Record ->
MA: Measurement Agent
MP: Measurement Peer
Figure 12: LMAP deployment example, with Measurement Agent monitoring
DNS response time
In this particular example, the MA monitors DNS messages in order to
measure the DNS response time. The Measurement Agent may be embedded
in the user host, or it may be located in another device capable of
observing user traffic. The MA learns the IP addresses of
measurement devices and the intent to communicate with or access the
services of a particular domain name, and perhaps also information on
key points in a service provider's network, such as the address of
one of its DNS servers.
In principle, any of the user sensitive information of interest
(listed above) can be collected and stored in the monitoring scenario
and so must be secured.
It would also be possible for a Measurement Agent to source the DNS
query itself, and then there are not many privacy concerns.
8.4.6. Storage and Reporting of Measurement Results
Although the mechanisms for communicating results (beyond the initial
Collector) are beyond the scope of the initial LMAP work, 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". DoS and other attacks described in the
Security section represent threats as well, and these attacks are
more effective when sensitive information protections have been
compromised.
8.5.1. Surveillance
Section 5.1.1 of [RFC6973] describes surveillance as the "observation
or monitoring of an individual's communications or activities."
Hence, all Measurement Methods that measure user traffic are a form
of surveillance, with inherent risks.
Measurement Methods that avoid periods of user transmission
indirectly produce a record of times when a subscriber or authorised
user has used their network access service.
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
timestamped, 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, as 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 initial LMAP work, though this
communications channel will certainly need protection as will the
mass storage itself.
The LMAP Controller may have direct access to storage of Subscriber
information (for example, location, billing, service parameters,
etc.) and other information that the controlling organisation
considers private and again needs protection.
Note that there is tension between the desire to store all raw
results in the LMAP Collector (for reproduction and custom analysis)
and the need to protect the privacy of measurement participants.
Many of the mitigations described in Section 8.6 are most efficient
when deployed at the MA, therefore minimising the risks associated
with stored results.
8.5.3. Correlation and Identification
Sections 5.2.1 and 5.2.2 of [RFC6973] describe correlation as
combining various pieces of information to obtain desired
characteristics of an individual, and identification as using this
combination to infer identity.
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 Measurement Tasks were deferred or sent a name resolution for
www.example.com at 2300 UTC.
If a user's access with another system already gave away sensitive
information, correlation is clearly easier and can result in
re-identification, even when an LMAP system conserves sensitive
information to great extent.
8.5.4. Secondary Use and Disclosure
Sections 5.2.3 and 5.2.4 of [RFC6973] describe secondary use as
unauthorised utilisation of an individual's information for a purpose
the individual did not intend, and disclosure as when such
information is revealed causing another's notions of the individual
to change or confidentiality to be violated.
Measurement Methods that measure user traffic are a form of secondary
use, and the Subscribers' permission should be obtained beforehand.
It may be necessary to obtain the measured ISP's permission to
conduct measurements (for example, when required by the terms and
conditions of the service agreement) and notification is considered
good measurement practice.
For Measurement Methods that measure Measurement Traffic the
Measurement Results provide some limited information about the
Subscriber or ISP and could result in secondary uses. For example,
the use of the Results in unauthorised marketing campaigns would
qualify as secondary use. Secondary use may break national laws and
regulations, and may violate an individual's expectations or desires.
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.
LMAP Results can be useful for general reporting about performance
and for specific troubleshooting. They need different levels of
information detail, as explained in the paragraphs below.
For general results, reporting, the results can be aggregated into large
categories (for example, the month of March, all US 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.
For troubleshooting, so that a network operator or end user can
identify a performance issue or failure, potentially all the network
information (for example, IP addresses, equipment IDs, location),
Measurement Schedules, service configurations, 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. This level of
detail is greater than needed for general performance monitoring.
As regards Measurement Methods that measure user traffic, we note
that a user may give temporary permission (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. The Collector
may perform pre-storage minimisation and other mitigations
(Section 8.6.4) to help preserve privacy.
For MAs with access to the sensitive information of users (for
example, 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.
8.6.2. Anonymity
Section 6.1.1 of [RFC6973] describes an "anonymity set" as a way in
which anonymity is achieved: "there must exist a set of individuals
that appear to have the same attribute(s) as the individual."
Experimental methods for anonymisation of user-identifiable data (and
so particularly applicable to Measurement Methods that measure user
traffic) have been identified in [RFC6235]. However, the findings of
several of the same authors is that "there is increasing evidence
that anonymization applied to network trace or flow data on its own
is insufficient for many data protection applications as in [Bur10]."
Essentially, the details of such Measurement Methods 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.
The techniques in [RFC6235] could be applied more successfully in
Measurement Methods that generate Measurement Traffic, 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
[RFC7398]. For example, all measurements from a 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".
Another anonymisation technique is for the MA to include its Group-ID
instead of its MA-ID in its Measurement Reports, with several MAs
sharing the same Group-ID.
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
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 depersonalised 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) may be 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.
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 always good practice to limit the time that
personal information is stored.
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
is responsible (legally) for maintaining data protections described
in the Subscriber's agreement and agreements with other
organisations.
Finally, it is recommended that each entity described in Section 8.1,
(for example, individuals, ISPs, regulators, others) assess the risks
of LMAP data collection by conducting audits of their data protection
methods.
9. Informative References
[Bur10] Burkhart, M., Schatzmann, D., Trammell, B., and E. Boschi,
"The Role of Network Trace anonymisation Under Attack",
January 2010.
[IPPM-REG] Bagnulo, M., Claise, B., Eardley, P., Morton, A., and A.
Akhter, "Registry for Performance Metrics", Work in
Progress draft-ietf-ippm-metric-registry-03,
Progress, draft-ietf-ippm-metric-registry-04, July 2015.
[LMAP-INFO]
Burbridge, T., Eardley, P., Bagnulo, M., and J.
Schoenwaelder, "Information Model for Large-Scale
Measurement Platforms (LMAP)", Work in Progress draft-
ietf-lmap-information-model-06, Progress,
draft-ietf-lmap-information-model-06, July 2015.
[REST] Wikipedia, "Representational state transfer", July 2015,
<https://en.wikipedia.org/w/index.php?title=Representation
al_state_transfer&oldid=673799183>.
<https://en.wikipedia.org/w/index.php?
title=Representational_state_transfer&oldid=673799183>.
[RFC1035] Mockapetris, P., "Domain names - implementation and
specification", STD 13, RFC 1035, DOI 10.17487/RFC1035,
November 1987, <http://www.rfc-editor.org/info/rfc1035>.
[RFC3444] Pras, A. and J. Schoenwaelder, "On the Difference between
Information Models and Data Models", RFC 3444,
DOI 10.17487/RFC3444, January 2003,
<http://www.rfc-editor.org/info/rfc3444>.
[RFC4101] Rescorla, E. and IAB, "Writing Protocol Models", RFC 4101,
DOI 10.17487/RFC4101, June 2005,
<http://www.rfc-editor.org/info/rfc4101>.
[RFC4122] Leach, P., Mealling, M., and R. Salz, "A Universally
Unique IDentifier (UUID) URN Namespace", RFC 4122,
DOI 10.17487/RFC4122, July 2005,
<http://www.rfc-editor.org/info/rfc4122>.
[RFC4656] Shalunov, S., Teitelbaum, B., Karp, A., Boote, J., and M.
Zekauskas, "A One-way Active Measurement Protocol
(OWAMP)", RFC 4656, DOI 10.17487/RFC4656, September 2006,
<http://www.rfc-editor.org/info/rfc4656>.
[RFC5357] Hedayat, K., Krzanowski, R., Morton, A., Yum, K., and J.
Babiarz, "A Two-Way Active Measurement Protocol (TWAMP)",
RFC 5357, DOI 10.17487/RFC5357, October 2008,
<http://www.rfc-editor.org/info/rfc5357>.
[RFC6235] Boschi, E. and B. Trammell, "IP Flow Anonymization
Support", RFC 6235, DOI 10.17487/RFC6235, May 2011,
<http://www.rfc-editor.org/info/rfc6235>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<http://www.rfc-editor.org/info/rfc6241>.
[RFC6419] Wasserman, M. and P. Seite, "Current Practices for
Multiple-Interface Hosts", RFC 6419, DOI 10.17487/RFC6419,
November 2011, <http://www.rfc-editor.org/info/rfc6419>.
[RFC6887] Wing, D., Ed., Cheshire, S., Boucadair, M., Penno, R., and
P. Selkirk, "Port Control Protocol (PCP)", RFC 6887,
DOI 10.17487/RFC6887, April 2013,
<http://www.rfc-editor.org/info/rfc6887>.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973,
DOI 10.17487/RFC6973, July 2013,
<http://www.rfc-editor.org/info/rfc6973>.
[RFC7011] Claise, B., Ed., Trammell, B., Ed., and P. Aitken,
"Specification of the IP Flow Information Export (IPFIX)
Protocol for the Exchange of Flow Information", STD 77,
RFC 7011, DOI 10.17487/RFC7011, September 2013,
<http://www.rfc-editor.org/info/rfc7011>.
[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258,
May 2014, <http://www.rfc-editor.org/info/rfc7258>.
[RFC7368] Chown, T., Ed., Arkko, J., Brandt, A., Troan, O., and J.
Weil, "IPv6 Home Networking Architecture Principles",
RFC 7368, DOI 10.17487/RFC7368, October 2014,
<http://www.rfc-editor.org/info/rfc7368>.
[RFC7398] Bagnulo, M., Burbridge, T., Crawford, S., Eardley, P., and
A. Morton, "A Reference Path and Measurement Points for
Large-Scale Measurement of Broadband Performance",
RFC 7398, DOI 10.17487/RFC7398, February 2015,
<http://www.rfc-editor.org/info/rfc7398>.
[RFC7536] Linsner, M., Eardley, P., Burbridge, T., and F. Sorensen,
"Large-Scale Broadband Measurement Use Cases", RFC 7536,
DOI 10.17487/RFC7536, May 2015,
<http://www.rfc-editor.org/info/rfc7536>.
[TR-069] The Broadband Forum, "CPE WAN Management Protocol", TR-069
Amendment 5, November 2013,
<https://www.broadband-forum.org/technical/download/TR-
069_Amendment-5.pdf>.
<https://www.broadband-forum.org/technical/download/
TR-069_Amendment-5.pdf>.
[UPnP] UPnP Forum, "UPnP Device Architecture 2.0", February 2015,
<http://www.iso.org/iso/home/store/catalogue_ics/
catalogue_detail_ics.htm?csnumber=57195>.
Acknowledgments
This document originated as a merger of three individual drafts:
"Terminology for Large MeAsurement Platforms (LMAP)" (July 2013), "A
Framework and Inventory for a Large Scale Measurement System" (July
2013), and "A framework for large-scale measurements" (July 2013).
Thanks to Juergen Schoenwaelder for his detailed review of the
terminology. Thanks to Charles Cook for a very detailed review of an
early draft of this document. Thanks to Barbara Stark and Ken Ko for
many helpful comments about later draft versions.
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, Dan Romascanu, Dave Thorne, Frode Soerensen,
Greg Mirsky, Guangqing Deng, Jason Weil, Jean-Francois Tremblay,
Jerome Benoit, Joachim Fabini, Juergen Schoenwaelder, Jukka Manner,
Ken Ko, Lingli Deng, Mach Chen, Matt Mathis, Marc Ibrahim, Michael
Bugenhagen, Michael Faath, Nalini Elkins, Radia Perlman, Rolf Winter,
Sam Crawford, Sharam Hakimi, Steve Miller, Ted Lemon, Timothy Carey,
Vaibhav Bajpai, Vero Zheng, and William Lupton.
Philip Eardley, Trevor Burbridge and Marcelo Bagnulo worked in part
on the Leone research project, which received funding from the
European Union Seventh Framework Programme under grant agreement
number 317647.
Authors' Addresses
Philip Eardley
BT
Adastral Park, Martlesham Heath
Ipswich
England
Email: philip.eardley@bt.com
Al Morton
AT&T Labs
200 Laurel Avenue South
Middletown, NJ
United States
Email: acmorton@att.com
Marcelo Bagnulo
Universidad Carlos III de Madrid
Av. Universidad 30
Leganes, Madrid 28911
Spain
Phone: 34 91 6249500
Email: marcelo@it.uc3m.es
URI: http://www.it.uc3m.es
Trevor Burbridge
BT
Adastral Park, Martlesham Heath
Ipswich
England
Email: trevor.burbridge@bt.com
Paul Aitken
Brocade Communications Systems, Inc.
19a Canning Street, Level 3
Edinburgh, Scotland EH3 8EG
United Kingdom
Email: paitken@brocade.com
Aamer Akhter
Consultant
118 Timber Hitch
Cary, NC
United States
Email: aakhter@gmail.com