Internet DRAFT - draft-eardley-lmap-framework
draft-eardley-lmap-framework
Network Working Group P. Eardley
Internet-Draft T. Burbridge
Intended status: Informational BT
Expires: January 16, 2014 A. Morton
AT&T Labs
July 15, 2013
A framework for large-scale measurements
draft-eardley-lmap-framework-02
Abstract
Measuring broadband service on a large scale requires standardisation
of the logical architecture and a description of the key protocols
that coordinate interactions between the components. The document
presents an overall framework for large-scale measurements and
discusses which elements could be standardised in the IETF. It is
intended to assist the work of the LMAP working group.
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on January 16, 2014.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Outline of framework . . . . . . . . . . . . . . . . . . . . . 4
3. Constraints . . . . . . . . . . . . . . . . . . . . . . . . . 6
3.1. Measurement system is under the direction of a single
organisation . . . . . . . . . . . . . . . . . . . . . . . 6
3.2. Each MA may only have a single Controller at any point
in time . . . . . . . . . . . . . . . . . . . . . . . . . 7
3.3. A Measurement Agent acts autonomously . . . . . . . . . . 7
4. Work items for LMAP WG . . . . . . . . . . . . . . . . . . . . 8
4.1. Information Model . . . . . . . . . . . . . . . . . . . . 9
4.2. Control Protocol . . . . . . . . . . . . . . . . . . . . . 10
4.3. Report Protocol . . . . . . . . . . . . . . . . . . . . . 10
5. Related work required but out of scope of LMAP . . . . . . . . 10
5.1. Standard measurement tests . . . . . . . . . . . . . . . . 10
5.2. Characterisation plan . . . . . . . . . . . . . . . . . . 11
5.3. Other elements . . . . . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12
7. Security Considerations . . . . . . . . . . . . . . . . . . . 12
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13
9. Changes . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.1. from -00 to -01 . . . . . . . . . . . . . . . . . . . . . 13
10. Informative References . . . . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 14
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1. Introduction
The Large-Scale Measurement of Broadband Performance (LMAP) working
group standardizes the LMAP measurement system for performance
measurements of broadband access devices such as home and enterprise
edge routers, personal computers, mobile devices, set top box,
whether wired or wireless. Measuring portions of the Internet on a
large scale is essential for accurate characterizations of
performance over time and geography.
[use-cases] discusses several use cases have been proposed for large-
scale measurements:
o Operators: to help plan their network and identify faults
o End Users: to run diagnostic checks, such as a network speed test
o Regulators: to benchmark several network operators and support
public policy development
The LMAP framework should be useful for all these.
The goal is to have the measurements (made using the same metrics and
mechanisms) for a large number of points on the Internet, and to have
the results collected and stored in the same form.
There are existing measurement systems. However, they typically lack
some of the desirable features for a large-scale measurement system:
o Standardised - in terms of the tests that they perform, the
components, the data models and protocols for transferring
information between the components. For example so that it is
meaningful to compare measurements made of the same metric at
different times and places. For example so that the operator of a
measurement system can buy the various components from different
vendors. Today's systems are proprietary in some or all of these
aspects.
o Extensible - it should be easy to add or modify tests, for example
an improved test methodology or to measure a performance metric
not previously considered important (e.g., bufferbloat).
o Large-scale - [use-cases] envisages Measurement Agents in every
home gateway and edge device such as set-top-boxes and tablet
computers. Existing systems have up to a few thousand Measurement
Agents (without judging how much further they could scale).
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o Diversity - a measurement system should handle different types of
Measurement Agent - for example Measurement Agents may come from
different vendors, be in wired and wireless networks and be on
devices with IPv4 or IPv6 addresses.
2. Outline of framework
The LMAP framework for large-scale measurements has four elements:
o Measurement Agent (MA)
o Measurement Peer
o Controller
o Collector
In addition there are some components that are outside LMAP but
useful within the context of a large scale measurement system:
o Initialiser
o Subscriber Parameter Database
o Results Database
o Data Analysis Tools
o Operator's OAM (Operations Administration and Management)
a large-scale measurement system essentially has three sets of
communications:
o several measurement protocols between a Measurement Agent and a
Measurement Peer
o a Control Protocol between a Controller and a MA
o a Report Protocol between a MA and a Collector.
A Measurement Agent and a Measurement Peer jointly perform an active
measurement test, by generating test traffic and measuring some
metric associated with its transfer over the path from one to the
other; for example the time taken to transfer a 'test file'. A MA
may also conduct passive testing through the observation of traffic
(i.e. without the involvement of a Measurement Peer); for example an
end user's mix of applications.
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The MA interacts with the Controller and Collector, and a Measurement
Peer only takes part in active tests (and does not interact with the
Controller and Collector).
The MA functions are implemented either in specialised hardware or as
code on general purpose devices like a PC, tablet or smartphone. The
Measurement Peer may be an LMAP device or a normal, non-LMAP device
(for example if the MA measures the time for a DNS response or a
webpage download from www.example.com).
The Controller manages a MA by instructing it which tests it should
perform and when. For example it may instruct a MA at a home
gateway: "Run the 'download speed test' with the test server at the
end user's first IP point in the network; if the end user is active
then delay the test and re-try 1 minute later, with up to 3 re-tries;
repeat every hour at xx.05 + Unif[0,180] seconds". The Controller
also manages a MA by instructing it how to report the test 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". As well as regular tests, a Controller can initiate a
one-off test ("Do test now", "Report as soon as possible"). These
are called the Test and Report Schedule.
The Collector accepts a Report from a MA with the results from its
tests. It may also do some processing on the results - for instance
to eliminate outliers, as they can severely impact the aggregated
results.
Therefore the MA is a LMAP-specific device that initiates the test,
gets instructions from the Controller and reports to the Collector.
It is possible that communications between two Collectors, two
Controllers and a Controller and Collector may be useful in some use
cases, perhaps to help a measurement system scale. Work on such a
protocol is out of scope of LMAP (?)
The Initialiser, Subscriber Parameter Database, Results Database,
Data Analysis Tools and OAM are out of scope of LMAP. They may be
provided through existing protocols or applications and are likely to
be part of a complete large-scale measurement system. See Section 5
for further discussion.
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+------------+ +-----------+ +-----------+
| | Instruction | | test traffic | |
| Controller | --------------> |Measurement| ............. |Measurement|
| | |Agent (MA) | | Peer |
+------------+ +-----------+ +-----------+
|
| Report
|
V
+-------------+
| Collector |
+-------------+
Figure 1: Schematic of main elements of LMAP framework
3. Constraints
3.1. Measurement system is under the direction of a single organisation
In the LMAP framework (as defined in the WG's charter) the
measurement system is under the direction of a single organisation
that is responsible both for the data and the quality of experience
delivered to its users. Clear responsibility is critical given that
a misbehaving large-scale measurement system could potentially harm
user experience, user privacy and network security.
However, the components of an LMAP measurement system can be deployed
in administrative domains that are not owned by the measuring
organisation. Thus, the system of functions deployed by a single
organisation constitutes a single LMAP domain which may span
ownership or other administrative boundaries.
Note that different LMAP measurement systems may overlap, in the
sense that the active measurement packets of one measurement system
appear along with normal user traffic to another measurement system.
For instance, imagine an operator with an MA on the home gateway and
an end user with an MA on their laptop. Rather than making separate
measurements, an organisation might share its measurement data, or a
suitably anonymised version of it, with another organisation.
However, any form of coordination between different organisation
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 LMAP.
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3.2. Each MA may only have a single Controller at any point in time
The constraint avoids different Controllers giving a MA conflicting
instructions and so means that the MA does not have to manage
contention between multiple Test (or Report) Schedules. This
simplifies the design of MAs (critical for a large-scale
infrastructure) and allows a Test Schedule to be tested on specific
types of MA before deployment to ensure that the home user experience
is not impacted (due to CPU, memory or broadband-product
constraints).
An operator may have several Controllers, perhaps with a Controller
for different types of MA (home gateways, tablets) or location
(Ipswich, Edinburgh).
To avoid problems with NAT and firewalls, it is likely that the MA
'pulls' the configuration from its Controller, as identified by the
Initialiser.
o Open issue: Should there be negotiation between a Controller and
its MA, or should the Controller simply instruct the MA by sending
its Test and Report Schedules?
* The argument for negotiation is that occasionally the MA may be
updated with enhanced with versions of existing tests. It is
easier for the Controller to learn the MAs capabilities
directly from the MA than from a management system. It avoids
any mis-synchronisation.
* The argument against negotiation is that it makes the
Controller-MA protocol more complicated, increases the MAs
resource requirements and increases the complexity of the
Controller when it decides how to schedule tests across
numerous MAs or when it deploys a new Test Schedule to
potentially millions of MAs.
o Open issue: what happens if a Controller fails, how is the MA is
homed onto a new one?
3.3. A Measurement Agent acts autonomously
Once the MA gets its Test and Report Schedules from its Controller
then it acts autonomously, in terms of operation of the tests and
reporting of the result.
Firstly, this means that the MA initiates Measurement Tasks. For the
typical case where the MA is on a home gateway or edge device, this
means that the MA initiates a 'download speed test' by asking a
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Measurement Peer to send the file. The main rationale is that, for a
test that should be performed when there is no user traffic on the
link, the MA knows whether the end user is active and therefore
whether to start the test or delay it. Having the Schedule on the MA
also avoids it having to check frequently with the Controller.
Further, if the MA is behind a NAT then the Measurement Peer
naturally learns its public-facing IP address.
Secondly, it is useful for the MA and perhaps the Measurement Peer to
make some 'admission control' checks at the initiation of the
Measurement Task to ensure that desired test conditions are present.
The exchange of initialization packets between the MA and Measurement
Peer ensures basic connectivity between them. Also, the MA may delay
Measurement Task may if the associated subscriber is active, or the
Measurement Peer may reject a testing request if it is overloaded.
It has also been suggested that, in extremis, the Controller may want
the ability to send a Measurement Suppression message to an MA, which
causes the Measurement Tasks to be temporarily stopped.
Last, it is easier to secure the reporting process, for example with
a unique certificate for each MA-Collector pair, so that the
Collector is confident the results really do originate from the MA.
All measurement results are sent from the MA.
4. Work items for LMAP WG
This Section considers the work that the LMAP working group needs to
tackle. Section 5 considers other work that needs doing that would
be beyond the scope of the LMAP WG.
The main work items are:
o Information Model, the abstract definition of the information
carried from the Controller to the MA and the information carried
from the MA to the Collector.
o Control protocol and the associated data model: The definition of
how instructions are delivered from a Controller to a MA; this
includes a Data Model consistent with the Information Model plus a
transport protocol.
o Report protocol and the associated data model: The definition of
how the Report is delivered from a MA to a Collector; this
includes a Data Model consistent with the Information Model plus a
transport protocol.
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4.1. Information Model
The Information Model provides a protocol and device independent view
of the information carried from the Controller to the MA and the
information carried from the MA to the Collector. It can be
implemented via a Control Protocol and Report Protocol, as defined by
the LMAP WG. It is also possible that other Control and Report
Protocols could be defined by other standards bodies or proprietary,
however it is important that they all implement the same Information
Model, in order to ease the definition, operation and
interoperability of large-scale measurement systems.
The Information Model also includes information that is pre-
configured on the MA in order that it can start communicating with a
Controller.
An initial proposal for the Information Model is in
[information-model].
The Information Model is divided into two main parts, each of which
may be broken down into sub-parts:
o information about the Instruction: Information that is received by
the MA from the Controller pertaining to the measurement and
reporting configuration. This includes:
* what measurements to do: the Measurement Task could be defined
by reference to a registry entry, along with any parameters
that need to be set (such as the address of the Measurement
Peer) and any Environmental Constraint (such as, delay the test
if the end user is active)
* when to do them: the Measurement Schedule details the timings
of regular tests, one-off tests, and if regularly tests should
be temporarily suppressed
* how to report the Measurement Results: via Reporting
Channel(s), each of which defines a target Collector and Report
Schedule
o information about the Report: Information transmitted from the MA
to the Collector including measurement results and the context in
which they were conducted. This includes:
* the MAs identifier, or perhaps a Group-ID to anonymise results
* the actual Measurement Results, including the time they were
measured
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* the details of the Measurement Task (to avoid the Collector
having to ask the Controller for this information later)
It is important to consider how to divide the Information Model into
(sub-)parts, so that each (sub-)part can be updated independently at
different times and regularities, as discussed in [information-model]
4.2. Control Protocol
The Control protocol and its associated data model define how
instructions are delivered from a Controller to a MA; this includes a
Data Model consistent with the Information Model plus a transport
protocol. This may be a simple instruction - response protocol, and
LMAP will specify how it operates over an existing protocol (to be
selected, perhaps REST-style HTTP(s) or NETCONF).
4.3. Report Protocol
The Report protocol and the associated data model: The definition of
how the Report is delivered from a MA to a Collector; this includes a
Data Model consistent with the Information Model plus a transport
protocol (to be selected, perhaps REST-style HTTP(s) or IPFIX).
5. Related work required but out of scope of LMAP
This section considers the items that need to be agreed between
deployers of large-scale measurement systems, but that are out of
scope of the LMAP WG (Section 4 considers items within its scope).
5.1. Standard measurement tests
Standardised methods are needed for each metric that is measured. A
registry for commonly-used metrics [registry] is also required, so
that a test can be defined simply by its identifier in the registry.
The methods and registry would hopefully also be referenced by other
standards organisations.
o Such activities are in scope of the IPPM working group (possibly
re-chartered) and not LMAP.
A new (or revised) test may need to be uploaded to MAs. How this is
done is out of scope of the IETF; it could be as a firmware upgrade
for a home hub, or new app for a PC, etc and may be device-specific.
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5.2. Characterisation plan
Each organisation operating an LMAP system and collecting
measurements for comparison purposes needs to conduct the same
measurements according to the same sampling plan (ie size and
schedule) and make the results available in the same format. The
scope of comparison determines the set of organisations needing to
agree on the common characterisation plan; for example those falling
within the same regulatory environment in a particular country or
region. Such agreements are certainly facilitated by IETF's work,
but the details of the plan are beyond the scope of work in IETF.
5.3. Other elements
Other elements may be useful within the context of a large scale
measurement system and worthy of standardisation, but are outside the
scope of the LMAP WG: Initialiser, Subscriber Parameter Database,
Results Database, Data Analysis Tools and operator's OAM.
An Initialiser configures a MA with details about its Controller,
including authentication credentials. A bootstrap protocol is likely
to be technology specific and so for different types of device could
be defined by the Broadband Forum, DOCSIS or IEEE. Possible
protocols are SNMP, NETCONF or (for Home Gateways) CPE WAN Management
Protocol (CWMP) from the Auto Configuration Server (ACS) (as
specified in TR-069).
A Subscriber Parameter Database contains information about the line,
for example the customer's broadband contract (2, 40 or 80Mb/s), the
line technology (DSL or fibre), the time zone where the MA is
located, and the type of home gateway and MA. These are all factors
which may affect the choice of what Measurement Tasks to run and how
to interpret the Measurement Results. For example, a download test
suitable for a line with an 80Mb/s contract may overwhelm a 2Mb/s
line. Another example is if the Controller wants to run a one-off
test to diagnose a fault, then it should understand what problem the
customer is experiencing and what tests have already been run. The
subscribers' service parameters are already gathered and stored by
existing operations systems.
A Results Database records all measurements in an equivalent form,
for example an SQL database [schulzrinne], so that they can be easily
accessed by the Data Analysis Tools whilst the LMAP system
implementor can choose local solutions for each component. The Data
Analysis Tools also need to understand subscriber service
information, for example the broadband contract.
The Data Analysis Tools receive the results from the Collector or via
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the Results Database. They might visualise the data or identify
which component or link is likely to be the cause of a fault or
degradation.
The operator's OAM (Operations, Administration and Management) uses
the results from the tools.
6. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
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.
We assume that each Measurement Agent will receive test
configuration, scheduling and reporting instructions from a single
organisation (operator of 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 be prevented from replay. If a malicious party can
gain control of the Measurement Agent they can use the MA
capabilities to launch DoS attacks at targets, reduce the network
user experience and corrupt the measurement results that are reported
to the Collector. By altering the tests that are operated and/or the
Collector address 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 reporting of the MA must also be secured to maintain
confidentiality. The results must be encrypted such that only the
authorised Collector can decrypt the results to prevent the leakage
of confidential or private information. In addition it must be
authenticated that the results have come from the expected MA and
that they have not been tampered with. It must not be possible to
spoof an MA to inject falsified data into the measurement platform or
to corrupt the results of a real MA.
Availability should also be considered. While the loss of some MAs
may not be considered critical, the unavailability of the Collector
could mean that valuable business data or data critical to a
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regulatory process is lost. Similarly, the unavailability of a
Controller could mean that the MAs continue to operate an incorrect
test schedule or fail to initiate.
A malicious party could "game the system". For example, where a
regulator is running a measurement system in order to benchmark
operators, an operator could try to identify the broadband lines that
the regulator was measuring and prioritise that traffic. This
potential issue is currently handled by a code of conduct. It is
outside the scope of the LMAP WG to consider the issue.
Concerning privacy and data protection, the role of the LMAP
framework should be to ensure that only authorised data is collected
and that this data is returned securely to the framework operator.
Data should be stored securely and onward sharing of data to other
parties should be controlled according to local data protection
regulations. Depending upon the ownership/placement of the MA, local
data protection laws, the tests being operated and existing user
agreements, it is possible that additional consent may need to be
secured from parties such as the home broadband user. Having the
measurement system under the direction of a single organisation
clarifies the responsibility for data protection.
The next versions of [lmap-yang] and [lmap-ipfix] will also include
further consideration of security.
8. Acknowledgements
Thanks to numerous people for much discussion, directly and on the
LMAP list. This document tries to capture the current conclusions.
Philip Eardley and Trevor Burbridge work in part on the Leone
research project, which receives funding from the European Union
Seventh Framework Programme [FP7/2007-2013] under grant agreement
number 317647.
9. Changes
9.1. from -00 to -01
aligned with terminology in draft-eardley-lmap-terminology
introduced aspects mentioned in the LMAP WG charter
introduced aspects from the Information model in
draft-burbridge-lamp-information-model
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10. Informative References
[RFC6241] "Network Configuration Protocol (NETCONF)",
<http://tools.ietf.org/html/rfc6241>.
[information-model]
Burbridge, T., Eardley, P., Bagnulo, M., and J.
Schoenwaelder, "Information Model for Large-Scale
Measurement Platforms (LMAP)", <http://tools.ietf.org/
html/draft-burbridge-lmap-information-model>.
[lmap-ipfix]
"An LMAP application for IPFIX",
<http://tools.ietf.org/html/draft-bagnulo-lmap-ipfix>.
[lmap-netconf]
"Considerations on using NETCONF with LMAP Measurement
Agents",
<http://tools.ietf.org/html/draft-schoenw-lmap-netconf>.
[lmap-yang]
"A YANG Data Model for LMAP Measurement Agents",
<http://tools.ietf.org/html/draft-schoenw-lmap-yang>.
[registry]
"A registry for commonly used metrics. Independent
registries", <http://tools.ietf.org/html/
draft-bagnulo-ippm-new-registry-independent>.
[schulzrinne]
"Large-Scale Measurement of Broadband Performance: Use
Cases, Architecture and Protocol Requirements", <http://
tools.ietf.org/html/draft-schulzrinne-lmap-requirements>.
[use-cases]
"Large-Scale Broadband Measurement Use Cases",
<http://tools.ietf.org/html/draft-linsner-lmap-use-cases>.
[yang-api]
"YANG-API Protocol", <http://tools.ietf.org/html/rfc6241>.
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Authors' Addresses
Philip Eardley
British Telecom
Adastral Park, Martlesham Heath
Ipswich
ENGLAND
Email: philip.eardley@bt.com
Trevor Burbridge
British Telecom
Adastral Park, Martlesham Heath
Ipswich
ENGLAND
Email: trevor.burbridge@bt.com
Al Morton
AT&T Labs
200 Laurel Avenue South
Middletown, NJ
USA
Email: acmorton@att.com
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