A framework for large-scale measurements
draft-eardley-lmap-framework-01
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draft-eardley-lmap-framework-01
Network Working Group P. Eardley
Internet-Draft T. Burbridge
Intended status: Informational BT
Expires: August 29, 2013 A. Morton
AT&T
February 25, 2013
A framework for large-scale measurements
draft-eardley-lmap-framework-01
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 discussions about the potential creation 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 August 29, 2013.
Copyright Notice
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to this document. Code Components extracted from this document must
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described in the Simplified BSD License.
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 required in LMAP . . . . . . . . . . . . . . . . . . . . 8
4.1. Defining the Test and Report Schedules . . . . . . . . . . 8
4.2. Defining the Report . . . . . . . . . . . . . . . . . . . 9
5. Related work required but out of scope of LMAP . . . . . . . . 9
5.1. Standard measurement tests . . . . . . . . . . . . . . . . 10
5.2. Characterisation plan . . . . . . . . . . . . . . . . . . 10
5.3. Other elements . . . . . . . . . . . . . . . . . . . . . . 10
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Security Considerations . . . . . . . . . . . . . . . . . . . 11
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 12
9. Informative References . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13
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1. Introduction
[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
The LMAP framework should be useful for all these.
The key requirement is for large scale. A measurement system might
have at least ~100k Measurement Agents.
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. 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 (eg 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).
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.
This section forms the problem statement / aim of the proposed LMAP
working group, in the context of the constraints and scope given
below.
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2. Outline of framework
The LMAP framework for large-scale measurements has three elements:
o Measurement Agent (MA)
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)
Two Measurement Agents (MAs) jointly perform an active measurement
test, by generating test traffic and measuring some metric associated
with its transfer over the path from one MA to the other; for example
the time taken to transfer a 'test file'. Some tests may involve
more than two MAs; for example, to measure 'latency under load'. A
single MA may also conduct passive testing through the observation of
traffic (ie without the involvement of a second MA); for example an
end user's mix of applications.
The MA functions are implemented either in specialised hardware or as
code on general purpose devices like a PC, tablet or smartphone.
o Comment: It may be useful to distinguish two types of MA - a
'complete MA' that interacts with the Controller and Collector,
and a 'remote MA' that only takes part in active tests (and does
not interact with the Controller and Collector). This is for
further study.
o Comment: A 'complete MA' may want to run a test against a normal,
non-LMAP device, for example 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
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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.
o Comment: 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. It is for further study whether such communications should
be in or out of scope of LMAP.
o Comment: 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.
An Initialiser configures a MA with details about its Controller,
including authentication credentials. 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 Test Schedule. 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.
A Results Database records all measurements in an equivalent form,
for example an SQL database [schulzrinne], so that they can be easily
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accessed by the Data Analysis Tools whilst the LMAP system
implementor can choose local solutions for each component.
The Data Analysis Tools receive the results from the Collector or via
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.
+------------+ +-----------+ +-----------+
| | Test & Report | | test traffic | (remote) |
| Controller | --------------> |Measurement| ............. |Measurement|
| | Schedule |Agent (MA) | |Agent (MA) |
+------------+ +-----------+ +-----------+
|
| 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
Explanation: In the LMAP framework the measurement system is under
the direction of a single organisation that is responsible both for
the data and the quality of experience delivered to its users. Clear
responsibility is critical given that a misbehaving large-scale
measurement system could potentially harm user privacy and network
security.
Given the novelty of large-scale measurement efforts, the expectation
is that inter-organization coordination is an out-of-band
consideration. There could be scenarios where measurement data, or a
suitably anonymised version of it, is shared between organisations,
via their Data Analysis Tools for instance. Consideration 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
Explanation: 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, 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 MA's 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 MA's
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 tests. 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
remote MA to send the file. The main rationale is that, for a test
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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 remote MA naturally learns its
public-facing IP address.
Secondly, 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 required in LMAP
This Section considers the work that the prospective LMAP working
group would tackle. Section 5 considers other work that needs doing
that would be beyond the scope of the LMAP WG.
4.1. Defining the Test and Report Schedules
The Test and Report Schedules contain the instructions sent by the
Controller to the MA. The Schedules could be combined into a single
Schedule, this is for further study.
The Test Schedule would include things like:
o Which tests to operate and (if applicable) to which remote MAs
o The testing schedule
o Any test or environmental parameters
o How to react to the presence of user or other test traffic (if not
inherent in the test design)
The Report Schedule would include things like:
o How often to report results (e.g. time or volume of data)
o Where to report results
o What to do if reporting fails
Defining Test and Report Schedule(s) is in scope of LMAP:
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o Information model: the abstract definition of the Schedule
o Data model: which instantiates the information model in a
particular language. It could be done using an existing IETF data
modeling language, for example YANG as sketched in [lmap-yang].
o Protocol: how the Test and Report Schedule(s) are delivered from
the Controller to the MA. Possibilities would include NETCONF
[RFC6241] as discussed in [lmap-netconf] or a RESTful interface
[yang-api].
4.2. Defining the Report
The Report contain the measurement results sent by the Controller to
the MA. The Report includes things like:
o The results of the test (typically at least all the singleton
measurements, including the time they were measured)
o The MA's identifier
o The test and its parameters (essentially an 'echo' of the Test
Schedule with the parameters actually used, which avoids the
Collector having to ask the Controller).
Defining the Report is in scope of LMAP:
o Information model: the abstract definition of the Report
o Data model: which instantiates the information model in a
particular language. It could be done using an existing IETF data
modeling language, for example IPFIX, as sketched in [lmap-ipfix]
or
o Protocol: how the Report is delivered from the MA to the
Collector. Possibilities would include IPFIX, as sketched in
[lmap-ipfix] or a RESTful interface.
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 prospective LMAP WG (Section 4 considers items within
its scope).
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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.
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
The other elements discussed in Section 2 may also benefit from
standardisation: Initialiser, Subscriber Parameter Database, Results
Database, Data Analysis Tools and operator's OAM.
The Initialiser-MA protocol is likely to be technology specific and
so for different types of device could be defined by the Broadband
Forum, DOCSIS or IEEE. The Data Analysis Tools and operator's OAM
are also beyond the scope of the IETF. For the Subscriber Parameter
Database and Results Database, it is possible that there could be
work to define a data model - it is suggested that this is for later
study and should be out of the initial scope of IETF work.
6. IANA Considerations
This document makes no request of IANA.
Note to RFC Editor: this section may be removed on publication as an
RFC.
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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
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.
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.
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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. Informative References
[RFC6241] "Network Configuration Protocol (NETCONF)",
<http://tools.ietf.org/html/rfc6241>.
[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]
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"YANG-API Protocol", <http://tools.ietf.org/html/rfc6241>.
Authors' Addresses
Philip Eardley
BT
Trevor Burbridge
BT
Al Morton
AT&T
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