Network Working Group                                       I. Learmonth
Internet-Draft                                               Tor Project
Intended status: Informational                              May 16, 2019
Expires: November 17, 2019

       Guidelines for Performing Safe Measurement on the Internet


   Researchers from industry and academia will often use Internet
   measurements as a part of their work.  While these measurements can
   give insight into the functioning and usage of the Internet, they can
   come at the cost of user privacy.  This document describes guidelines
   for ensuring that such measurements can be carried out safely.


   Comments are solicited and should be addressed to the research
   group's mailing list at and/or the author(s).

   The sources for this draft are at:

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on November 17, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   ( in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.

1.  Introduction

   When performing research using the Internet, as opposed to an
   isolated testbed or simulation platform, means that you research co-
   exists in a space with other users.  This document outlines
   guidelines for academic and industry researchers that might use the
   Internet as part of scientific experiementation.

1.1.  Scope of this document

   Following the guidelines contained within this document is not a
   substitute for any institutional ethics review process you may have,
   although these guidelines could help to inform that process.
   Similarly, these guidelines are not legal advice and local laws must
   also be considered before starting any experiment that could have
   adverse impacts on user privacy.

1.2.  Active and passive measurements

   Internet measurement studies can be broadly categorized into two
   groups: active measurements and passive measurements.  Active
   measurements generate traffic.  Performance measurements such as TCP
   throughput testing [RFC6349] or functional measurements such as the
   feature-dependent connectivity failure tests performed by
   [PATHspider] both fall into this category.  Performing passive
   measurements requires existing traffic.  Passive measurements can
   help to inform new developments in Internet protocols but can also
   carry risk.

   The type of measurement is not truly binary and many studies will
   include both active and passive components.  Each of the
   considerations in this document must be carefully considered for
   their applicability regardless of the type of measurement.

2.  Consent

   Ideally, informed consent would be collected from all users of a
   shared network before measurements were performed on them.  In cases
   where it is practical to do so, this should be done.

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   For consent to be informed, all possible risks must be presented to
   the users.  The considerations in this document can be used to
   provide a starting point although other risks may be present
   depending on the nature of the measurements to be performed.

2.1.  Proxy Consent

   In cases where it is not practical to collect informed consent from
   all users of a shared network, it may be possible to obtain proxy
   consent.  Proxy consent may be given by a network operator or
   employer that would be more familiar with the expectations of users
   of a network than the researcher.

2.2.  Implied consent

   In larger scale measurements, even proxy consent collection may not
   be practical.  In this case, implied consent may be presumed from
   users for some measurements.  Consider that users of a network will
   have certain expectations of privacy and those expectations may not
   align with the privacy guarantees offered by the technologies they
   are using.  As a thought experiment, consider how users might respond
   if you asked for their informed consent for the measurements you'd
   like to perform.

   For example, the operator of a web server that is exposed to the
   Internet hosting a popular website would have the expectation that it
   may be included in surveys that look at supported protocols or
   extensions but would not expect that attempts be made to degrade the
   service with large numbers of simultaneous connections.

   If practical, attempt to obtain informed consent or proxy consent
   from a sample of users to better understand the expectations of other

3.  Safety Considerations

3.1.  Use a testbed

   Wherever possible, use a testbed.  An isolated network means that
   there are no other users sharing the infrastructure you are using for
   your experiments.

   When measuring performance, competing traffic can have negative
   effects on the performance of your test traffic and so the testbed
   approach can also produce more accurate and repeatable results than
   experiments using the public Internet.

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   WAN link conditions can be emulated through artificial delays and/or
   packet loss using a tool like [netem].  Competing traffic can also be
   emulated using traffic generators.

3.2.  Only record your own traffic

   When performing measurements be sure to only capture traffic that you
   have generated.  Traffic may be identified by IP ranges or by some
   token that is unlikely to be used by other users.

   Again, this can help to improve the accuracy and repeatability of
   your experiment.  [RFC2544], for performance benchmarking, requires
   that any frames received that were not part of the test traffic are
   discarded and not counted in the results.

3.3.  Be respectful of other's infrastructure

   If your experiment is designed to trigger a response from
   infrastructure that is not your own, consider what the negative
   consequences of that may be.  At the very least your experiment will
   consume bandwidth that may have to be paid for.

   In more extreme circumstances, you could cause traffic to be
   generated that causes legal trouble for the owner of that
   infrastructure.  The Internet is a global network crossing many legal
   jurisdictions and so what may be legal for you is not necessarily
   legal for everyone.

   If you are sending a lot of traffic quickly, or otherwise generally
   deviate from typical client behaviour, a network may identify this as
   an attack which means that you will not be collecting results that
   are representative of what a typical client would see.

3.3.1.  Maintain a "Do Not Scan" list

   When performing active measurements on a shared network, maintain a
   list of hosts that you will never scan regardless of whether they
   appear in your target lists.  When developing tools for performing
   active measurement, or traffic generation for use in a larger
   measurement system, ensure that the tool will support the use of a
   "Do Not Scan" list.

   If complaints are made that request you do not generate traffic
   towards a host or network, you must add that host or network to your
   "Do Not Scan" list, even if no explanation is given or the request is

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   You may ask the requester for their reasoning if it would be useful
   to your experiment.  This can also be an oppertunity to explain your
   research and offer to share any results that may be of interest.  If
   you plan to share the reasoning when publishing your measurement
   results, e.g. in an academic paper, you must seek consent for this
   from the requester.

   Be aware that in publishing your measurement results, it may be
   possible to infer your "Do Not Scan" list from those results.  For
   example, if you measured a well-known list of popular websites then
   it would be possible to correlate the results with that list to
   determine which are missing.

3.4.  Only collect data that is safe to make public

   When deciding on the data to collect, assume that any data collected
   might become public.  There are many ways that this could happen,
   through operation security mistakes or compulsion by a judicial

3.5.  Minimization

   For all data collected, consider whether or not it is really needed.

3.6.  Aggregation

   When collecting data, consider if the granularity can be limited by
   using bins or adding noise.  XXX: Differential privacy.

3.7.  Source Aggregation

   Do this at the source, definitely do it before you write to disk.

   [Tor.2017-04-001] presents a case-study on the in-memory statistics
   in the software used by the Tor network, as an example.

4.  Risk Analysis

   The benefits should outweigh the risks.  Consider auxiliary data
   (e.g. third-party data sets) when assessing the risks.

5.  Security Considerations

   Take reasonable security precautions, e.g. about who has access to
   your data sets or experimental systems.

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6.  IANA Considerations

   This document has no actions for IANA.

7.  Acknowledgements

   Many of these considerations are based on those from the
   [TorSafetyBoard] adapted and generalised to be applied to Internet

   Other considerations are taken from the Menlo Report [MenloReport]
   and its companion document [MenloReportCompanion].

8.  Informative References

              Dittrich, D. and E. Kenneally, "The Menlo Report: Ethical
              Principles Guiding Information and Communication
              Technology Research", August 2012,

              Bailey, M., Dittrich, D., and E. Kenneally, "Applying
              Ethical Principles to Information and Communication
              Technology Research", October 2013,

   [netem]    Stephen, H., "Network emulation with NetEm", April 2005.

              Learmonth, I., Trammell, B., Kuehlewind, M., and G.
              Fairhurst, "PATHspider: A tool for active measurement of
              path transparency", DOI 10.1145/2959424.2959441, July

   [RFC2544]  Bradner, S. and J. McQuaid, "Benchmarking Methodology for
              Network Interconnect Devices", RFC 2544,
              DOI 10.17487/RFC2544, March 1999,

   [RFC6349]  Constantine, B., Forget, G., Geib, R., and R. Schrage,
              "Framework for TCP Throughput Testing", RFC 6349,
              DOI 10.17487/RFC6349, August 2011,

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              Herm, K., "Privacy analysis of Tor's in-memory
              statistics", Tor Tech Report 2017-04-001, April 2017,

              Tor Project, "Tor Research Safety Board",

Author's Address

   Iain R. Learmonth
   Tor Project


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