LMAP Use Cases: Large-Scale Broadband Measurement Use Cases
What large-scale measurements of broadband performance are for, and how the probes might be built.
Linsner, M., Eardley, P., Burbridge, T., and F. Sorensen, "Large-Scale Broadband Measurement Use Cases", RFC 7536, DOI 10.17487/RFC7536, May 2015, <https://www.rfc-editor.org/info/rfc7536>.
@misc{rfc7536,
series = {Request for Comments},
number = 7536,
howpublished = {RFC 7536},
publisher = {RFC Editor},
doi = {10.17487/RFC7536},
url = {https://www.rfc-editor.org/info/rfc7536},
author = {M. Linsner and P. Eardley and T. Burbridge and F. Sorensen},
title = {{Large-Scale Broadband Measurement Use Cases}},
pagetotal = 17,
year = 2015,
month = may,
} RFC text
Contents
Internet Engineering Task Force (IETF) M. Linsner
Request for Comments: 7536 Cisco Systems
Category: Informational P. Eardley
ISSN: 2070-1721 T. Burbridge
BT
F. Sorensen
Nkom
May 2015
Large-Scale Broadband Measurement Use Cases
Abstract
Measuring broadband performance on a large scale is important for
network diagnostics by providers and users, as well as for public
policy. Understanding the various scenarios and users of measuring
broadband performance is essential to development of the Large-scale
Measurement of Broadband Performance (LMAP) framework, information
model, and protocol. This document details two use cases that can
assist in developing that framework. The details of the measurement
metrics themselves are beyond the scope of this document.
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/rfc7536.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction ....................................................3
2. Use Cases .......................................................3
2.1. Internet Service Provider (ISP) Use Case ...................3
2.2. Regulator Use Case .........................................4
3. Details of ISP Use Case .........................................5
3.1. Understanding the Quality Experienced by Customers .........5
3.2. Understanding the Impact and Operation of New Devices
and Technology .............................................6
3.3. Design and Planning ........................................6
3.4. Monitoring Service Level Agreements ........................7
3.5. Identifying, Isolating, and Fixing Network Problems ........7
4. Details of Regulator Use Case ...................................8
4.1. Providing Transparent Performance Information ..............8
4.2. Measuring Broadband Deployment .............................9
4.3. Monitoring Traffic Management Practices ...................10
5. Implementation Options .........................................10
6. Conclusions ....................................................12
7. Security Considerations ........................................13
8. Informative References .........................................15
Contributors ......................................................17
Authors' Addresses ................................................17
1. Introduction
This document describes two use cases for the Large-scale Measurement
of Broadband Performance (LMAP). The use cases contained in this
document are (1) the Internet Service Provider Use Case and (2) the
Regulator Use Case. In the first, a network operator wants to
understand the performance of the network and the quality experienced
by customers, while in the second, a regulator wants to provide
information on the performance of the ISPs in their jurisdiction.
There are other use cases that are not the focus of the initial LMAP
work (for example, end users would like to use measurements to help
identify problems in their home network and to monitor the
performance of their broadband provider); it is expected that the
same mechanisms are applicable.
Large-scale measurements raise several security concerns, including
privacy issues. These are summarized in Section 7 and considered in
further detail in [Framework].
2. Use Cases
From the LMAP perspective, there is no difference between fixed
service and mobile (cellular) service used for Internet access.
Hence, like measurements will take place on both fixed and mobile
networks. Fixed services include technologies like Digital
Subscriber Line (DSL), Cable, and Carrier Ethernet. Mobile services
include all those advertised as 2G, 3G, 4G, and Long Term Evolution
(LTE). A metric defined to measure end-to-end services will execute
similarly on all access technologies. Other metrics may be access
technology specific. The LMAP architecture covers both IPv4 and IPv6
networks.
2.1. Internet Service Provider (ISP) Use Case
A network operator needs to understand the performance of their
networks, the performance of the suppliers (downstream and upstream
networks), the performance of Internet access services, and the
impact that such performance has on the experience of their
customers. Largely, the processes that ISPs operate (which are based
on network measurement) include:
o Identifying, isolating, and fixing problems, which may be in the
network, with the service provider, or in the end-user equipment.
Such problems may be common to a point in the network topology
(e.g., a single exchange), common to a vendor or equipment type
(e.g., line card or home gateway), or unique to a single user line
(e.g., copper access). Part of this process may also be helping
users understand whether the problem exists in their home network
or with a third-party application service instead of with their
broadband (BB) product.
o Design and planning. Through monitoring the end-user experience,
the ISP can design and plan their network to ensure specified
levels of user experience. Services may be moved closer to end
users, services upgraded, the impact of QoS assessed, or more
capacity deployed at certain locations. Service Level Agreements
(SLAs) may be defined at network or product boundaries.
o Understanding the quality experienced by customers. The network
operator would like to gain better insight into the end-to-end
performance experienced by its customers. "End-to-end" could, for
instance, incorporate home and enterprise networks, and the impact
of peering, caching, and Content Delivery Networks (CDNs).
o Understanding the impact and operation of new devices and
technology. As a new product is deployed, or a new technology
introduced into the network, it is essential that its operation
and its impact are measured. This also helps to quantify the
advantage that the new technology is bringing and support the
business case for larger roll-out.
2.2. Regulator Use Case
A regulator may want to evaluate the performance of the Internet
access services offered by operators.
While each jurisdiction responds to distinct consumer, industry, and
regulatory concerns, much commonality exists in the need to produce
datasets that can be used to compare multiple Internet access service
providers, diverse technical solutions, geographic and regional
distributions, and marketed and provisioned levels and combinations
of broadband Internet access services.
Regulators may want to publish performance measures of different ISPs
as background information for end users. They may also want to track
the growth of high-speed broadband deployment, or to monitor the
traffic management practices of Internet providers.
A regulator's role in the development and enforcement of broadband
Internet access service policies requires that the measurement
approaches meet a high level of verifiability, accuracy, and
provider-independence to support valid and meaningful comparisons of
Internet access service performance. Standards can help regulators'
shared needs for scalable, cost-effective, scientifically robust
solutions to the measurement and collection of broadband Internet
access service performance information.
3. Details of ISP Use Case
3.1. Understanding the Quality Experienced by Customers
Operators want to understand the quality of experience (QoE) of their
broadband customers. The understanding can be gained through a
"panel", i.e., measurement probes deployed to several customers. A
probe is a device or piece of software that makes measurements and
reports the results, under the control of the measurement system.
Implementation options are discussed in Section 5. The panel needs
to include a representative sample of the operator's technologies and
broadband speeds. For instance, it might encompass speeds ranging
from below 8 Mbps to over 100 Mbps. The operator would like the
end-to-end view of the service, rather than just the access portion.
This involves relating the pure network parameters to something like
a 'mean opinion score' [MOS], which will be service dependent (for
instance, web-browsing QoE is largely determined by latency above a
few Mbps).
An operator will also want compound metrics such as "reliability",
which might involve packet loss, DNS failures, retraining of the
line, video streaming under-runs, etc.
The operator really wants to understand the end-to-end service
experience. However, the home network (Ethernet, Wi-Fi, powerline)
is highly variable and outside its control. To date, operators (and
regulators) have instead measured performance from the home gateway.
However, mobile operators clearly must include the wireless link in
the measurement.
Active measurements are the most obvious approach, i.e., special
measurement traffic is sent by -- and to -- the probe. In order not
to degrade the service of the customer, the measurement data should
only be sent when the user is silent, and it shouldn't reduce the
customer's data allowance. The other approach is passive
measurements on the customer's ordinary traffic; the advantage is
that it measures what the customer actually does, but it creates
extra variability (different traffic mixes give different results)
and, in particular, it raises privacy concerns. [RFC6973] discusses
privacy considerations for Internet protocols in general, while
[Framework] discusses them specifically for large-scale measurement
systems.
From an operator's viewpoint, understanding customer experience
enables it to offer better services. Also, simple metrics can be
more easily understood by senior managers who make investment
decisions and by sales and marketing.
3.2. Understanding the Impact and Operation of New Devices and
Technology
Another type of measurement is to test new capabilities before they
are rolled out. For example, the operator may want to:
o Check whether a customer can be upgraded to a new broadband
option.
o Understand the impact of IPv6 before it is made available to
customers. Questions such as these could be assessed: Will v6
packets get through? What will the latency be to major websites?
What transition mechanisms will be most appropriate?
o Check whether a new capability can be signaled using TCP options
(how often it will be blocked by a middlebox -- along the lines of
the experiments described in [Extend-TCP]).
o Investigate a QoS mechanism (e.g., checking whether Diffserv
markings are respected on some path).
3.3. Design and Planning
Operators can use large-scale measurements to help with their network
planning -- proactive activities to improve the network.
For example, by probing from several different vantage points the
operator can see that a particular group of customers has performance
below that expected during peak hours, which should help with
capacity planning. Naturally, operators already have tools to help
with this -- a network element reports its individual utilization
(and perhaps other parameters). However, making measurements across
a path rather than at a point may make it easier to understand the
network. There may also be parameters like bufferbloat that aren't
currently reported by equipment and/or that are intrinsically path
metrics.
With information gained from measurement results, capacity planning
and network design can be more effective. Such planning typically
uses simulations to emulate the measured performance of the current
network and understand the likely impact of new capacity and
potential changes to the topology. Simulations, informed by data
from a limited panel of probes, can help quantify the advantage that
a new technology brings and support the business case for larger
roll-out.
It may also be possible to use probes to run stress tests for risk
analysis. For example, an operator could run a carefully controlled
and limited experiment in which probing is used to assess the
potential impact if some new application becomes popular.
3.4. Monitoring Service Level Agreements
Another example is that the operator may want to monitor performance
where there is a Service Level Agreement (SLA). This could be with
its own customers; in particular, enterprises may have an SLA. The
operator can proactively spot when the service is degrading near the
point of the SLA limit and get information that will enable more
informed conversations with the customer at contract renewal.
An operator may also want to monitor the performance of its
suppliers, to check whether they meet their SLA or to compare two
suppliers if it is dual-sourcing. This could include its transit
operator, CDNs, peering, video source, or local network provider for
a global operator in countries where it doesn't have its own network.
A virtual operator may monitor the whole underlying network.
Through a better understanding of its own network and its suppliers,
the operator should be able to focus investment more effectively --
in the right place at the right time with the right technology.
3.5. Identifying, Isolating, and Fixing Network Problems
Operators can use large-scale measurements to help identify a fault
more rapidly and decide how to solve it.
Operators already have Test and Diagnostic tools, where a network
element reports some problem or failure to a management system.
However, many issues are not caused by a point failure but something
wider and so will trigger too many alarms, while other issues will
cause degradation rather than failure and so not trigger any alarm.
Large-scale measurements can help provide a more nuanced view that
helps network management to identify and fix problems more rapidly
and accurately. The network management tools may use simulations to
emulate the network and so help identify a fault and assess possible
solutions.
An operator can obtain useful information without measuring the
performance on every broadband line. By measuring a subset, the
operator can identify problems that affect a group of customers. For
example, the issue could be at a shared point in the network topology
(such as an exchange), or common to a vendor, or equipment type; for
instance, [IETF85-Plenary] describes a case where a particular home
gateway upgrade had caused a (mistaken!) drop in line rate.
A more extensive deployment of the measurement capability to every
broadband line would enable an operator to identify issues unique to
a single customer. Overall, large-scale measurements can help an
operator fix the fault more rapidly and/or allow the affected
customers to be informed of what's happening. More accurate
information enables the operator to reassure customers and take more
rapid and effective action to cure the problem.
Often, customers experience poor broadband due to problems in the
home network -- the ISP's network is fine. For example, they may
have moved too far away from their wireless access point.
Anecdotally, a large fraction of customer calls about fixed BB
problems are due to in-home wireless issues. These issues are
expensive and frustrating for an operator, as they are extremely hard
to diagnose and solve. The operator would like to narrow down
whether the problem is in the home (a problem with the home network,
edge device, or home gateway), in the operator's network, or with an
application service. The operator would like two capabilities:
firstly, self-help tools that customers use to improve their own
service or understand its performance better -- for example, to
reposition their devices for better Wi-Fi coverage; and secondly,
on-demand tests that the operator can run instantly, so that the call
center person answering the phone (or e-chat) could trigger a test
and get the result while the customer is still in an online session.
4. Details of Regulator Use Case
4.1. Providing Transparent Performance Information
Some regulators publish information about the quality of the various
Internet access services provided in their national market. Quality
information about service offers could include speed, delay, and
jitter. Such information can be published to facilitate end users'
choice of service provider and offer. Regulators may check the
accuracy of the marketing claims of Internet service providers and
may also encourage ISPs to all use the same metrics in their service
level contracts. The goal of these transparency mechanisms is to
promote competition for end users and potentially also help content,
application, service, and device providers develop their Internet
offerings.
The published information needs to be:
o Accurate - the measurement results must be correct and not
influenced by errors or side effects. The results should be
reproducible and consistent over time.
o Comparable - common metrics should be used across different ISPs
and service offerings, and over time, so that measurement results
can be compared.
o Meaningful - the metrics used for measurements need to reflect
what end users value about their broadband Internet access
service.
o Reliable - the number and distribution of measurement agents, and
the statistical processing of the raw measurement data, need to be
appropriate.
In practical terms, the regulators may measure network performance
from users towards multiple content and application providers,
including dedicated test measurement servers. Measurement probes are
distributed to a 'panel' of selected end users. The panel covers all
the operators and packages in the market, spread over urban,
suburban, and rural areas, and often includes both fixed and mobile
Internet access. Periodic tests running on the probes can, for
example, measure actual speed at peak and off-peak hours, but can
also measure other detailed quality metrics like delay and jitter.
Collected data goes afterwards through statistical analysis, deriving
estimates for the whole population. Summary information, such as a
service quality index, is published regularly, perhaps alongside more
detailed information.
The regulator can also facilitate end users to monitor the
performance of their own broadband Internet access service. They
might use this information to check that the performance meets that
specified in their contract or to understand whether their current
subscription is the most appropriate.
4.2. Measuring Broadband Deployment
Regulators may also want to monitor the improvement over time of
actual broadband Internet access performance in a specific country or
a region. The motivation is often to evaluate the effect of the
stimulated growth over time, when government has set a strategic goal
for high-speed broadband deployment, whether in absolute terms or
benchmarked against other countries. An example of such an
initiative is [DAE]. The actual measurements can be made in the same
way as described in Section 4.1.
4.3. Monitoring Traffic Management Practices
A regulator may want to monitor traffic management practices or
compare the performance of Internet access service with specialized
services offered in parallel to, but separate from, Internet access
service (for example, IPTV). A regulator could monitor for
departures from application agnosticism such as blocking or
throttling of traffic from specific applications, or preferential
treatment of specific applications. A measurement system could send,
or passively monitor, application-specific traffic and then measure
in detail the transfer of the different packets. While it is
relatively easy to measure port blocking, how to detect other types
of differentiated treatment is a research topic in itself. The
"Glasnost: Enabling End Users to Detect Traffic Differentiation"
paper [M-Labs_NSDI-2010] and follow-on tool "Glasnost" [Glasnost]
provide an example of work in this area.
A regulator could also monitor the performance of the broadband
service over time, to try and detect if the specialized service is
provided at the expense of the Internet access service. Comparison
between ISPs or between different countries may also be relevant for
this kind of evaluation.
The motivation for a regulator monitoring such traffic management
practices is that regulatory approaches related to net neutrality and
the open Internet have been introduced in some jurisdictions.
Examples of such efforts are the Internet policy as outlined by the
Body of European Regulators for Electronic Communications guidelines
for quality of service [BEREC-Guidelines] and the US FCC's
"Preserving the Open Internet" Report and Order [FCC-R&O]. Although
legal challenges can change the status of policy, the take-away for
LMAP purposes is that policy-makers are looking for measurement
solutions to assist them in discovering biased treatment of traffic
flows. The exact definitions and requirements vary from one
jurisdiction to another.
5. Implementation Options
There are several ways of implementing a measurement system. The
choice may be influenced by the details of the particular use case
and what the most important criteria are for the regulator, ISP, or
third party operating the measurement system.
One type of probe is a special hardware device that is connected
directly to the home gateway. The devices are deployed to a
carefully selected panel of end users, and they perform measurements
according to a defined schedule. The schedule can run throughout the
day, to allow continuous assessment of the network. Careful design
ensures that measurements do not detrimentally impact the home user
experience or corrupt the results by testing when the user is also
using the broadband line. The system is therefore tightly controlled
by the operator of the measurement system. One advantage of this
approach is that it is possible to get reliable benchmarks for the
performance of a network with only a few devices. One disadvantage
is that it would be expensive to deploy hardware devices on a mass
scale sufficient to understand the performance of the network at the
granularity of a single broadband user.
Another type of probe involves implementing the measurement
capability as a webpage or an "app" that end users are encouraged to
download onto their mobile phone or computing device. Measurements
are triggered by the end user; for example, the user interface may
have a button to "test my broadband now." One advantage of this
approach is that the performance is measured to the end user, rather
than to the home gateway, and so includes the home network. Another
difference is that the system is much more loosely controlled, as the
panel of end users and the schedule of tests are determined by the
end users themselves rather than the measurement system. While this
approach makes it easier to make measurements on a large scale, it is
harder to get comparable benchmarks, as the measurements are affected
by the home network; also, the population is self-selecting and so
potentially biased towards those who think they have a problem. This
could be alleviated by encouraging widespread downloading of the app
and careful post-processing of the results to reduce biases.
There are several other possibilities. For example, as a variant on
the first approach, the measurement capability could be implemented
as software embedded in the home gateway, which would make it more
viable to have the capability on every user line. As a variant on
the second approach, the end user could initiate measurements in
response to a request from the measurement system.
The operator of the measurement system should be careful to ensure
that measurements do not detrimentally impact users. Potential
issues include the following:
* Measurement traffic generated on a particular user's line may
impact that end user's quality of experience. The danger is
greater for measurements that generate a lot of traffic over a
lengthy period.
* The measurement traffic may impact that particular user's bill or
traffic cap.
* The measurement traffic from several end users may, in
combination, congest a shared link.
* The traffic associated with the control and reporting of
measurements may overload the network. The danger is greater
where the traffic associated with many end users is synchronized.
6. Conclusions
Large-scale measurements of broadband performance are useful for both
network operators and regulators. Network operators would like to
use measurements to help them better understand the quality
experienced by their customers, identify problems in the network, and
design network improvements. Regulators would like to use
measurements to help promote competition between network operators,
stimulate the growth of broadband access, and monitor 'net
neutrality'. There are other use cases that are not the focus of the
initial LMAP charter (although it is expected that the mechanisms
developed would be readily applied); for example, end users would
like to use measurements to help identify problems in their home
network and to monitor the performance of their broadband provider.
From consideration of the various use cases, several common themes
emerge, while there are also some detailed differences. These
characteristics guide the development of LMAP's framework,
information model, and protocol.
A measurement capability is needed across a wide number of
heterogeneous environments. Tests may be needed in the home network,
in the ISP's network, or beyond; they may be measuring a fixed or
wireless network; they may measure just the access network or across
several networks.
There is a role for both standardized and non-standardized
measurements. For example, a regulator would like to publish
standardized performance metrics for all network operators, while an
ISP may need their own tests to understand some feature special to
their network. Most use cases need active measurements, which create
and measure specific test traffic, but some need passive measurements
of the end user's traffic.
Regardless of the tests being operated, there needs to be a way to
demand or schedule the tests. Most use cases need a regular schedule
of measurements, but sometimes ad hoc testing is needed -- for
example, for troubleshooting. It needs to be ensured that
measurements do not affect the user experience and are not affected
by user traffic (unless desired). In addition, there needs to be a
common way to collect the results. Standardization of this control
and reporting functionality allows the operator of a measurement
system to buy the various components from different vendors.
After the measurement results are collected, they need to be
understood and analyzed. Often, it is sufficient to measure only a
small subset of end users, but per-line fault diagnosis requires the
ability to test every individual line. Analysis requires accurate
definition and understanding of where the test points are, as well as
contextual information about the topology, line, product, and the
subscriber's contract. The actual analysis of results is beyond the
scope of LMAP, as is the key challenge of how to integrate the
measurement system into a network operator's existing tools for
diagnostics and network planning.
Finally, the test data, along with any associated network, product,
or subscriber contract data, is commercial or private information and
needs to be protected.
7. Security Considerations
Large-scale measurements raise several potential security, privacy
(data protection) [RFC6973], and business sensitivity issues:
1. A malicious party may try to gain control of probes to launch DoS
(Denial of Service) attacks at a target. A DoS attack could be
targeted at a particular end user or set of end users, a certain
network, or a specific service provider.
2. A malicious party may try to gain control of probes to create a
platform for pervasive monitoring [RFC7258] or for more targeted
monitoring. [RFC7258] summarizes the threats as follows: "An
attack may change the content of the communication, record the
content or external characteristics of the communication, or
through correlation with other communication events, reveal
information the parties did not intend to be revealed." For
example, a malicious party could distribute to the probes a new
measurement test that recorded (and later reported) information of
maleficent interest. Similar concerns also arise if the
measurement results are intercepted or corrupted.
* From the end user's perspective, the concerns include a
malicious party monitoring the traffic they send and receive,
who they communicate with, the websites they visit, and such
information about their behavior as when they are at home and
the location of their devices. Some of the concerns may be
greater when the probe is on the end user's device rather than
on their home gateway.
* From the network operator's perspective, the concerns include
the leakage of commercially sensitive information about the
design and operation of their network, their customers, and
suppliers. Some threats are indirect; for example, the
attacker could reconnoiter potential weaknesses, such as open
ports and paths through the network, which enabled it to launch
an attack later.
* From the regulator's perspective, the concerns include
distortion of the measurement tests or alteration of the
measurement results. Also, a malicious network operator could
try to identify the broadband lines that the regulator was
measuring and prioritize that traffic ("game the system").
3. Another potential issue is a measurement system that does not
obtain the end user's informed consent, fails to specify a
specific purpose in the consent, or uses the collected information
for secondary uses beyond those specified.
4. Another potential issue is a measurement system that does not
indicate who is responsible for the collection and processing of
personal data and who is responsible for fulfilling the rights of
users. The responsible party (often termed the "data controller")
should, as good practice, consider such issues as defining:
o the purpose for which the data is collected and used,
o how the data is stored, accessed, and processed,
o how long the data is retained, and
o how the end user can view, update, and even delete their
personal data.
If anonymized personal data is shared with a third party, the data
controller should consider the possibility that the third party
can de-anonymize it by combining it with other information.
These security and privacy issues will need to be considered
carefully by any measurement system. In the context of LMAP,
[Framework] considers them further, along with some potential
mitigations. Other LMAP documents will specify one or more protocols
that enable the measurement system to instruct a probe about what
measurements to make and that enable the probe to report the
measurement results. Those documents will need to discuss solutions
to the security and privacy issues. However, the protocol documents
will not consider the actual usage of the measurement information.
Many use cases can be envisaged, and earlier in this document we
described some likely ones for the network operator and regulator.
8. Informative References
[IETF85-Plenary]
Crawford, S., "Large-Scale Active Measurement of Broadband
Networks", 'example' from slide 18, November 2012,
<http://www.ietf.org/proceedings/85/slides/
slides-85-iesg-opsandtech-7.pdf>.
[Extend-TCP]
Honda, M., Nishida, Y., Raiciu, C., Greenhalgh, A.,
Handley, M., and H. Tokuda, "Is it Still Possible to
Extend TCP?", Proceedings of IETF 82, November 2011,
<http://www.ietf.org/proceedings/82/slides/IRTF-1.pdf>.
[Framework]
Eardley, P., Morton, A., Bagnulo, M., Burbridge, T.,
Aitken, P., and A. Akhter, "A framework for Large-Scale
Measurement of Broadband Performance (LMAP)", Work in
Progress, draft-ietf-lmap-framework-14, April 2015.
[RFC6973] Cooper, A., Tschofenig, H., Aboba, B., Peterson, J.,
Morris, J., Hansen, M., and R. Smith, "Privacy
Considerations for Internet Protocols", RFC 6973,
July 2013, <http://www.rfc-editor.org/info/rfc6973>.
[RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an
Attack", BCP 188, RFC 7258, May 2014,
<http://www.rfc-editor.org/info/rfc7258>.
[FCC-R&O] United States Federal Communications Commission,
"Preserving the Open Internet; Broadband Industries
Practices: Report and Order", FCC 10-201, December 2010,
<http://hraunfoss.fcc.gov/edocs_public/attachmatch/
FCC-10-201A1.pdf>.
[BEREC-Guidelines]
Body of European Regulators for Electronic Communications,
"BEREC Guidelines for quality of service in the scope of
net neutrality", <http://berec.europa.eu/eng/
document_register/subject_matter/berec/download/0/
1101-berec-guidelines-for-quality-of-service-_0.pdf>.
[M-Labs_NSDI-2010]
M-Lab, "Glasnost: Enabling End Users to Detect Traffic
Differentiation", <http://www.measurementlab.net/
download/AMIfv945ljiJXzG-fgUrZSTu2hs1xRl5Oh-
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Contributors
The information in this document is partially derived from text
written by the following contributors:
James Miller jamesmilleresquire@gmail.com
Rachel Huang rachel.huang@huawei.com
Authors' Addresses
Marc Linsner
Cisco Systems, Inc.
Marco Island, FL
United States
EMail: mlinsner@cisco.com
Philip Eardley
BT
B54 Room 77, Adastral Park, Martlesham
Ipswich, IP5 3RE
United Kingdom
EMail: philip.eardley@bt.com
Trevor Burbridge
BT
B54 Room 70, Adastral Park, Martlesham
Ipswich, IP5 3RE
United Kingdom
EMail: trevor.burbridge@bt.com
Frode Sorensen
Norwegian Communications Authority (Nkom)
Lillesand
Norway
EMail: frode.sorensen@nkom.no
ISO Plain Language
On this page
§1Two Uses for Large-Scale Measurements
The document describes two use cases for the Large-scale Measurement of Broadband Performance, called LMAP. In the first, an internet service provider wants to understand the performance of its own network and the quality experienced by its customers. In the second, a regulator wants to provide information on the performance of the providers in its jurisdiction. Other use cases exist that are not the focus of the initial work, such as end users who want measurements to help identify a problem in their home network or to monitor their provider, and the same mechanisms are expected to apply to them.
From the point of view of the measurement work, there is no difference between a fixed service and a mobile one used for internet access, so measurements will be taken on both. Fixed services include DSL, cable and carrier Ethernet; mobile services include everything sold as 2G, 3G, 4G and Long Term Evolution. A metric defined to measure an end-to-end service will behave the same way on all access technologies, while other metrics may be specific to one. The architecture covers both IPv4 and IPv6 networks.
The document sets out who wants broadband performance measurements and why. A provider wants to know what its customers actually experience and where problems lie. A regulator wants numbers it can compare between providers and publish. Other groups, including customers themselves, are expected to use the same machinery later.
§2The Internet Service Provider Use Case
A network operator needs to understand the performance of its own networks, of its suppliers both downstream and upstream, of its internet access services, and the effect of that performance on what customers experience. The processes it already runs, which are based on network measurement, include identifying, isolating and fixing problems, which may be in the operator's network, with the service provider, or in the customer's own equipment. Such problems may be common to a point in the topology, such as a single exchange, common to a vendor or equipment type such as a line card or home gateway, or unique to one user line such as copper access. Part of this work is helping users understand whether a problem is in their own home network or with a third-party application service rather than with the broadband product.
Design and planning is the second process. By monitoring the end-user experience, the operator can design and plan its network to keep the service at a specified level: services may be moved closer to users, upgraded, the effect of quality of service assessed, or more capacity deployed in particular places, and service level agreements may be defined at network or product boundaries. The third process is understanding the quality customers experience, which means the end-to-end view rather than the access portion alone, incorporating the home and enterprise networks and the effect of peering, caching and content delivery networks. The fourth is understanding the impact and operation of new devices and technology: as a new product is deployed or a new technology introduced, its operation and its impact have to be measured, which also quantifies what the new technology brings and supports the case for a wider rollout.
A provider runs four kinds of measurement work. It looks for faults, which often come from a shared point such as an exchange or from one kind of equipment rather than from one line. It plans the network by watching what customers experience. It tries to understand the whole path from the home to the far end, not just the access network. And it measures new products and technologies as it rolls them out, to show what they are worth.
§3How an Operator Measures
The understanding of customer quality is gained through a panel of measurement probes deployed to several customers. A probe is a device or piece of software that makes measurements and reports the results under the control of the measurement system. The panel must include a representative sample of the operator's technologies and broadband speeds, for instance from below 8 Mbps to over 100 Mbps, and the operator wants the end-to-end view of the service rather than the access portion alone. That means relating the network parameters to something like a mean opinion score, which is service dependent, since web browsing quality is largely determined by latency once the speed is above a few Mbps. Compound metrics such as reliability may involve packet loss, DNS failures, retraining of the line and video streaming under-runs.
The operator really wants the end-to-end service experience, but the home network, whether Ethernet, Wi-Fi or powerline, is highly variable and outside its control. So far operators and regulators have measured from the home gateway instead, although a mobile operator clearly has to include the wireless link in the measurement. Active measurement is the most obvious approach, in which special measurement traffic is sent by and to the probe. To avoid degrading the service, that traffic should only be sent when the user is quiet, and it should not eat into the customer's data allowance. The alternative is passive measurement of the customer's ordinary traffic, which measures what the customer actually does but adds variability, because different traffic mixes give different results, and raises privacy concerns.
Several other operator tasks use the same machinery. New capabilities can be tested before rollout: whether a customer can be upgraded to a new broadband option, what the impact of IPv6 will be before it is offered, with questions such as whether IPv6 packets get through and what the latency to major websites will be, whether a new capability can be signalled using TCP options and how often a middlebox blocks it, and whether a quality of service mechanism works, for instance by checking that Differentiated Services markings are respected on a path. For planning, probing from several vantage points can show that a group of customers is below the expected performance at peak hours, which helps capacity planning, and there are parameters such as bufferbloat that equipment does not report and that are path metrics anyway. For service level agreements, the operator can spot the service degrading near the limit and be better informed when the contract is renewed, and can check the same for its suppliers, whether transit, content delivery networks, peering, a video source, or a local provider in a country where it has no network of its own. For faults, measurement gives a more nuanced view than alarms, since many issues are wide rather than point failures and so trigger too many alarms, while others degrade the service without triggering any at all. Measuring a subset of lines is enough to find problems that affect a group of customers, such as a shared exchange or a particular vendor, while measuring every line is what it takes to find problems unique to one customer. The operator also wants to narrow down whether a problem is in the home, in its own network, or with an application service, which means giving customers self-help tools, for example to reposition a device for better coverage, and giving the call centre the ability to run an on-demand test and get the result while the customer is still on the line.
The operator puts probes at a sample of customers, chosen to cover every technology and speed it sells, and reads the results as a picture of the whole service from the home to the far end. Active tests send special traffic, which has to wait until the customer is not using the line and must not use up their allowance. Passive tests watch the customer's own traffic, which is truer but noisier and raises privacy questions. The same measurements answer questions about new technology, about capacity at peak hours, about whether a service level agreement is about to be breached, and about where a fault lies.
§4The Regulator Use Case
A regulator may want to evaluate the performance of the internet access services offered by operators. Each jurisdiction has its own concerns, but there is much in common: the need to produce datasets that compare providers, technical solutions, geographic and regional distributions, and the levels and combinations of broadband service that are marketed and provisioned. Regulators may publish performance measures as background information for end users, track the growth of high-speed broadband deployment, or monitor the traffic management practices of providers.
Because a regulator's role covers the development and enforcement of broadband policy, the measurement approach has to meet a high level of verifiability, accuracy and provider-independence, so that comparisons of service performance are valid and meaningful. The published information has to be accurate, meaning correct and not influenced by errors or side effects, and reproducible and consistent over time; comparable, meaning common metrics across providers, offerings and time; meaningful, meaning the metrics reflect what end users value about their service; and reliable, meaning the number and distribution of measurement agents and the statistical processing of the raw data are appropriate.
In practice, regulators measure from users towards several content and application providers, including dedicated test servers. Probes are distributed to a panel of selected end users covering all the operators and packages in the market, spread over urban, suburban and rural areas, and often including both fixed and mobile access. Periodic tests can measure actual speed at peak and off-peak hours and other quality metrics such as delay and jitter. The collected data then goes through statistical analysis, deriving estimates for the whole population, and summary information such as a service quality index is published regularly. Regulators may also let end users monitor their own service, to check it against their contract or to decide whether their subscription is the right one.
Measuring broadband deployment is the same activity done over time to see whether a country or region is improving against a strategic goal. Monitoring traffic management practices is the third area: a regulator may look for departures from application neutrality, such as blocking or throttling of particular applications, or preferential treatment of them, by sending or passively watching application-specific traffic and measuring in detail how the packets are carried. Detecting port blocking is relatively easy; detecting other kinds of differentiated treatment is a research topic in its own right, and the Glasnost paper and tool are an example of work in this area. A regulator may also compare the broadband service over time to see whether a specialised service is being provided at the expense of internet access, and compare providers or countries. The motivation is that regulatory approaches on net neutrality and the open internet have been introduced in some jurisdictions, and although legal challenges can change the status of a policy, the point for measurement is that policy-makers are looking for measurement solutions that help them find biased treatment of traffic flows.
A regulator publishes comparable numbers so that customers can choose between providers and so that the regulator can check what providers claim. The numbers have to be accurate, comparable between providers, meaningful to customers, and based on enough probes to be reliable. The same machinery shows whether broadband is improving over time, and whether a provider is treating some applications differently from others, which is what net neutrality rules are about.
- AccurateThe results must be correct, free of errors and side effects, and reproducible over time.
- ComparableThe same metrics must be used across providers, offerings and time.
- MeaningfulThe metrics must reflect what end users value about their service.
- ReliableThe number and spread of the agents, and the statistics applied to the data, must be right.
§5Ways to Build a Measurement System
One type of probe is a dedicated hardware device connected directly to the home gateway, deployed to a carefully selected panel of end users and running measurements on a defined schedule that can run throughout the day. Careful design ensures that measurements do not harm the user's experience and do not corrupt the results by testing while the user is on the line, so the system is tightly controlled by whoever runs it. The advantage is reliable benchmarks from only a few devices; the disadvantage is that deploying hardware at a scale fine enough to understand one broadband line would be expensive.
The other type puts the measurement capability in a webpage or application that end users are encouraged to download onto their phone or computer, with measurements triggered by the user, for example by pressing a button to test the broadband now. The performance is then measured to the end user rather than to the home gateway, so it includes the home network. The system is much more loosely controlled, because the panel and the schedule are set by the users rather than by the measurement system, which makes it easier to measure at a large scale but harder to get comparable benchmarks, since the results are affected by the home network, and because the population selects itself and may be biased towards those who think they have a problem. Encouraging wide use of the application and careful post-processing can reduce that bias. Other options are a variant on the first, with the measurement code built into the home gateway, which makes it viable on every line, and a variant on the second, where the user starts a measurement in response to a request from the measurement system.
Whoever runs the system has to make sure the measurements do not harm users. The traffic generated on a line may affect that user's quality of experience, and the danger is greater for measurements that generate a lot of traffic over a long period. The traffic may count against the user's bill or traffic cap. Traffic from several users may combine to congest a shared link. And the control and reporting traffic may overload the network, which is more likely where the traffic of many users is synchronised.
There are two main designs. Dedicated hardware at the gateway gives reliable, controlled results but costs money and does not scale to every line. An application on the user's own phone measures the whole path including the home network and scales cheaply, but the results vary with the user's own equipment and the people who volunteer are not a random sample. Whichever is used, the measurement traffic has to be kept from spoiling the user's service, their allowance, or a shared link.
| Aspect | Hardware probe at the home gateway | Application on the user's own device |
|---|---|---|
| Where the measurement ends | At the home gateway | At the end user, so the home network is included |
| Who sets the schedule | The measurement system | The end user |
| Quality of the results | Reliable and comparable | Varies with the home network, and the panel is self-selecting |
| Cost and reach | Reliable benchmarks from a few devices, but expensive at scale | Cheap and easy to scale, but harder to get comparable numbers |
- Quality of experienceLong or heavy measurement traffic on the line affects what the user sees.
- The bill or traffic capMeasurement traffic counts against what the user has paid for.
- A shared linkTraffic from several users can add up and congest a link they all use.
- Synchronised reportingControl and reporting traffic from many users at once can overload the network.
§7Security and Privacy Considerations
Large-scale measurement raises several security, privacy and business sensitivity issues. A malicious party may try to take control of probes to launch denial of service attacks, targeted at one user or group of users, at a network, or at a service provider. A malicious party may also take control of probes to create a platform for pervasive or targeted monitoring, for example by distributing a new measurement test that records and reports information of its own interest, and the same concerns arise if results are intercepted or corrupted.
Each party sees a different risk. For the end user, the concerns are a malicious party watching the traffic they send and receive, who they talk to, the sites they visit, and their behaviour and the location of their devices, and some of these are greater when the probe is on the user's own device rather than on the home gateway. For the network operator, the concerns are the leakage of commercially sensitive information about the design and operation of the network, its customers and its suppliers, including indirect ones such as an attacker reconnoitring weaknesses such as open ports and paths through the network. For the regulator, the concerns are distortion of the tests or alteration of the results, and a malicious operator identifying the lines being measured and prioritising that traffic.
There is also the matter of consent and of who is responsible. A measurement system that does not obtain the end user's informed consent, does not specify a particular purpose for it, or uses the information for secondary purposes is a problem. So is a system that does not make clear who is responsible for collecting and processing personal data and for fulfilling the rights of users. The responsible party, often called the data controller, should as good practice define the purpose for which the data is collected and used, how it is stored, accessed and processed, how long it is retained, and how an end user can view, update and even delete their personal data. If anonymised personal data is shared with a third party, the data controller should consider that the third party may be able to de-anonymise it by combining it with other information. These questions are considered further in the LMAP framework document, and the protocol documents that will instruct probes and collect their results will have to address them.
Running probes at people's homes creates real risks. Someone could take over a probe and use it to attack others or to watch what people do online. The operator risks leaking the design of its network, and the regulator risks results being distorted by an operator that knows which lines are being measured. On top of that, the people whose homes host the probes must agree to it, the purpose must be clear, and someone must be accountable for keeping the data and for letting people see and delete it.