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RFC 7398

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Internet Engineering Task Force (IETF)                        M. Bagnulo
Request for Comments: 7398                                          UC3M
Category: Informational                                     T. Burbridge
ISSN: 2070-1721                                                       BT
                                                             S. Crawford
                                                              P. Eardley
                                                               A. Morton
                                                               AT&T Labs
                                                           February 2015

              A Reference Path and Measurement Points for
            Large-Scale Measurement of Broadband Performance


   This document defines a reference path for Large-scale Measurement of
   Broadband Access Performance (LMAP) and measurement points for
   commonly used performance metrics.  Other similar measurement
   projects may also be able to use the extensions described here for
   measurement point location.  The purpose is to create an efficient
   way to describe the location of the measurement point(s) used to
   conduct a particular measurement.

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

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
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  Purpose and Scope . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Terms and Definitions . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Reference Path  . . . . . . . . . . . . . . . . . . . . .   4
     3.2.  Subscriber  . . . . . . . . . . . . . . . . . . . . . . .   5
     3.3.  Dedicated Component (Links or Nodes)  . . . . . . . . . .   5
     3.4.  Shared Component (Links or Nodes) . . . . . . . . . . . .   5
     3.5.  Resource Transition Point . . . . . . . . . . . . . . . .   5
     3.6.  Service Demarcation Point . . . . . . . . . . . . . . . .   5
     3.7.  Managed and Unmanaged Sub-paths . . . . . . . . . . . . .   6
   4.  Reference Path  . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Measurement Points  . . . . . . . . . . . . . . . . . . . . .   7
   6.  Examples of Reference Paths with Various Technologies . . . .  11
   7.  Example of Reference Path with Resource Transition  . . . . .  13
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  15
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  16
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  17
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   This document defines a reference path for Large-scale Measurement of
   Broadband Access Performance (LMAP) or similar measurement projects.
   The series of IP Performance Metrics (IPPM) RFCs have developed terms
   that are generally useful for path description (see Section 5 of
   [RFC2330]).  There are a limited number of additional terms defined
   in this memo.

   The reference path (see Section 3.1 and Figure 1 of [Y.1541],
   including the accompanying discussion) is usually needed when
   attempting to communicate precisely about the components that
   comprise the path, and is often expressed in terms of their number
   (hops) and geographic location.  This memo takes the path definition
   further by establishing a set of measurement points along the path
   and ascribing a unique designation to each point.  This topic has
   been previously developed in Section 5.1 of [RFC3432] and as part of
   the updated framework for composition and aggregation in Section 4 of
   [RFC5835].  Section 4.1 of [RFC5835] defines the term "measurement

   Measurement points and the paths they inhabit are often described in
   general terms, like "end-to-end", "user-to-user", or "access".  These
   terms alone are insufficient for the scientific method, since we need
   to clarify issues such as: What is an end?  Where is a user located?
   Is the home network included?

   As an illustrative example, consider a measurement agent in an LMAP
   system.  When it reports its measurement results, rather than
   detailing its IP address and that of its measurement peer, it may
   prefer to describe the measured path segment abstractly (perhaps for
   privacy reasons), e.g., 'from a measurement agent at a home gateway
   to a measurement peer at a DSLAM.'  This memo provides the definition
   for such abstract 'measurement points' and, therefore, the portion of
   'reference path' between them.

   The motivation for this memo is to provide an unambiguous framework
   to describe measurement coverage or scope of the reference path.
   This is an essential part of the metadata to describe measurement
   results.  Measurements conducted over different path scopes are not a
   valid basis for performance comparisons.  We note that additional
   measurement context information may be necessary to support a valid
   comparison of results.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Purpose and Scope

   The scope of this memo is to define a reference path for LMAP
   activities with a sufficient level of detail to determine the
   location of different measurement points along a path without
   ambiguity.  These conventions are likely to be useful in other
   measurement projects and to describe the applicable measurement scope
   for some metrics.

   The connection between the reference path and specific network
   technologies (with differing underlying architectures) is within the
   scope of this memo, and examples are provided.  Both wired and
   wireless technologies are in scope.

   The purpose is to create an efficient way to describe the location of
   the measurement point(s) used to conduct a particular measurement so
   that the measurement result will be adequately described in terms of
   scope or coverage.  This should serve many measurement uses,

   o  diagnostic, where the same metric would be measured on different
      sub-paths bounded by measurement points (see Section 4.10 of
      [RFC5835]), for example, to isolate the sub-path contributing the
      majority of impairment levels observed on a path.

   o  comparison, where the same metric may be measured on equivalent
      portions of different network infrastructures, for example, to
      compare the performance of wired and wireless home network

3.  Terms and Definitions

   This section defines key terms and concepts for this memo.

3.1.  Reference Path

   A reference path is a serial combination of hosts, routers, switches,
   links, radios, and processing elements that comprise all the network
   elements traversed by each packet in a flow between the source and
   destination hosts.  A reference path also indicates the various
   boundaries present, such as administrative boundaries.  A reference
   path is intended to be equally applicable to all IP and link-layer

   networking technologies.  Therefore, the components are generically
   defined, but their functions should have a clear counterpart or be
   obviously omitted in any network architecture.

3.2.  Subscriber

   A subscriber is an entity (associated with one or more users) that is
   engaged in a subscription with a service provider.  The subscriber is
   allowed to subscribe and unsubscribe to services and to register a
   user or a list of users authorized to enjoy these services.  [Q.1741]

   Both the subscriber and service provider are allowed to set the
   limits relative to the use that associated users make of subscribed

3.3.  Dedicated Component (Links or Nodes)

   All resources of a dedicated component (typically a link or node on
   the reference path) are allocated to serving the traffic of an
   individual subscriber.  Resources include transmission time-slots,
   queue space, processing for encapsulation and address/port
   translation, and others.  A dedicated component can affect the
   performance of the reference path or the performance of any sub-path
   where the component is involved.

3.4.  Shared Component (Links or Nodes)

   A component on the reference path is designated a "shared component"
   when the traffic associated with multiple subscribers is served by
   common resources.

3.5.  Resource Transition Point

   This is a point between dedicated and shared components on a
   reference path that may be a point of significance and is identified
   as a transition between two types of resources.

3.6.  Service Demarcation Point

   This is the point where a service managed by the service provider
   begins (or ends) and varies by technology.  For example, this point
   is usually defined as the Ethernet interface on a residential gateway
   or modem where the scope of a packet transfer service begins and
   ends.  In the case of a WiFi service, this would be an air interface
   within the intended service boundary (e.g., walls of the coffee
   shop).  The demarcation point may be within an integrated endpoint
   using an air interface (e.g., Long-Term Evolution User Equipment (LTE
   UE)).  Ownership does not necessarily affect the demarcation point; a

   subscriber may own all equipment on their premises, but it is likely
   that the service provider will certify such equipment for connection
   to their network or that a third-party will certify standards

3.7.  Managed and Unmanaged Sub-paths

   Service providers are responsible for the portion of the path they
   manage.  However, most paths involve a sub-path that is beyond the
   management of the subscriber's service provider.  This means that
   private networks, wireless networks using unlicensed frequencies, and
   the networks of other service providers are designated as unmanaged
   sub-paths.  The service demarcation point always divides managed and
   unmanaged sub-paths.

4.  Reference Path

   This section defines a reference path for Internet communication.

Subsc. -- Private -- Private -- Service-- Intra IP -- GRA -- Transit ...
device     Net #1     Net #2    Demarc.    Access     GW     GRA GW

... Transit -- GRA -- Service -- Private -- Private -- Destination
    GRA GW     GW     Demarc.    Net #n     Net #n+1   Host

                GRA = Globally Routable Address
                 GW = Gateway

                         Figure 1: Reference Path

   The following are descriptions of reference path components that may
   not be clear from their name alone.

   o  Subsc.  (Subscriber) device - This is a host that normally
      originates and terminates communications conducted over the IP
      packet transfer service.

   o  Private Net #x - This is a network of devices owned and operated
      by the Internet service subscriber.  In some configurations, one
      or more private networks and the device that provides the service
      demarcation point are collapsed in a single device (ownership may
      shift to the service provider); this should be noted as part of
      the path description.

   o  Intra IP Access - This is the first point in the access
      architecture, beyond the service demarcation, where a globally
      routable IP address is exposed and used for routing.  In
      architectures that use tunneling, this point may be equivalent to
      the Globally Routable Address Gateway (GRA GW).  This point could
      also collapse to the device providing the service demarcation, in
      principle.  Only one Intra IP Access point is shown, but they can
      be identified in any access network.

   o  GRA GW - This is the point of interconnection between a service
      provider's administrative domain and the rest of the Internet,
      where routing will depend on the GRAs in the IP header.

   o  Transit GRA GW - If one or more networks intervene between the
      service provider's access networks of the subscriber and of the
      destination host, then such networks are designated "transit" and
      are bounded by two transit GRA GWs.

   Use of multiple IP address families in the measurement path must be
   noted, as the conversions between IPv4 and IPv6 certainly influence
   the visibility of a GRA for each family.

   In the case that a private address space is used throughout an access
   architecture, then the Intra IP Access points must use the same
   address space as the service demarcation point, and the Intra IP
   Access points must be selected such that a test between these points
   produces a useful assessment of access performance (e.g., includes
   both shared and dedicated access link infrastructure).

5.  Measurement Points

   A key aspect of measurement points, beyond the definition in
   Section 4.1 of [RFC5835], is that the innermost IP header and higher-
   layer information must be accessible through some means.  This is
   essential to measure IP metrics.  There may be tunnels and/or other
   layers that encapsulate the innermost IP header, even adding another
   IP header of their own.

   In general, measurement points cannot always be located exactly where
   desired.  However, the definition in [RFC5835] and the discussion in
   Section 5.1 of [RFC3432] indicate that allowances can be made; for
   example, it is nearly ideal when there are deterministic errors that
   can be quantified between desired and actual measurement points.

   The figure below illustrates the assignment of measurement points to
   selected components of the reference path.

Subsc. -- Private -- Private -- Service-- Intra IP -- GRA -- Transit ...
device     Net #1     Net #2    Demarc.    Access     GW     GRA GW
mp000                            mp100      mp150    mp190    mp200

... Transit -- GRA -- Service -- Private -- Private -- Destination
    GRA GW     GW     Demarc.    Net #n     Net #n+1   Host
    mpX90     mp890   mp800                            mp900

                GRA = Globally Routable Address
                 GW = Gateway

       Figure 2: Reference Path with Measurement Point Designations

   Each measurement point on a specific reference path MUST be assigned
   a unique number.  To facilitate interpretation of the results, the
   measuring organization (and whoever it shares results with) MUST have
   an unambiguous understanding of what path or point was measured.  In
   order to achieve this, a set of numbering recommendations follow.

   When communicating the results of measurements, the measuring
   organization SHOULD supply a diagram similar to Figure 2 (with the
   technology-specific information in examples that follow) and MUST
   supply it when additional measurement point numbers have been defined
   and used (with sufficient detail to identify measurement locations in
   the path).

   Ideally, the consumer of measurement results would know the location
   of a measurement point on the reference path from the measurement
   point number alone; the recommendations below provide a way to
   accomplish this goal.  Although the initial numbering may be fully
   compliant with this system, changing circumstances could, over time,
   lead to gaps in network numbers or non-monotonic measurement point
   number assignments along the path.  Such circumstances could include
   growth, consolidation, re-arrangement, and change of ownership of the
   network.  These are examples of reasonable causes for numbering
   deviations that must be identified on the reference path diagram, as
   required above.

   While the numbering of a measurement point is in the context of a
   particular path, for simplicity, the measuring organization SHOULD
   use the same numbering for a device (playing the same role) on all
   the measurement paths through it.  Similarly, whilst the measurement
   point numbering is in the context of a particular measuring
   organization, organizations with similar technologies and

   architectures are encouraged to coordinate on local numbering and

   The measurement point numbering system, mpXnn, has two independent

   1.  The X in mpXnn indicates the network number.  The network with
       the subscriber's device is network 0.  The network of a different
       organization (administrative or ownership domains) SHOULD be
       assigned a different number.  Each successive network number
       SHOULD be one greater than the previous network's number.  Two
       circumstances make it necessary to designate X=9 in the
       destination host's network and X=8 for the service provider
       network at the destination:

       A.  The number of transit networks is unknown.

       B.  The number of transit networks varies over time.

   2.  The nn in mpXnn indicates the measurement point and is locally
       assigned by network X.  The following conventions are suggested:

       A.  00 SHOULD be used for a measurement point at the subscriber's
           device and at the service demarcation point or GW nearest to
           the subscriber's device for transit networks.

       B.  90 SHOULD be used for a measurement point at the GW of a
           network (opposite from the subscriber's device or service

       C.  In most networks, measurement point numbers SHOULD
           monotonically increase from the point nearest the
           subscriber's device to the opposite network boundary on the
           path (but see item D for an exception).

       D.  When a destination host is part of the path, 00 SHOULD be
           used for a measurement point at the destination host and at
           the destination's service demarcation point.  Measurement
           point numbers SHOULD monotonically increase from the point
           nearest the destination's host to the opposite network
           boundary on the path ONLY in these networks.  This
           directional numbering reversal allows consistent 00
           designation for end hosts and service demarcation.

       E.  50 MAY be used for an intermediate measurement point of
           significance, such as a Network Address Translator (NAT).

       F.  20 MAY be used for a traffic aggregation point, such as a
           Digital Subscriber Line Access Multiplexer (DSLAM) within a

       G.  Any other measurement points SHOULD be assigned unused
           integers between 01 and 99.  The assignment SHOULD be stable
           for at least the duration of a particular measurement study
           and SHOULD avoid numbers that have been assigned to other
           locations within network X (unless the assignment is
           considered sufficiently stale).  Subnetworks or domains
           within a network are useful locations for measurement points.

   When supplying a diagram of the reference path and measurement
   points, the operator of the measurement system MUST indicate the
   reference path, the numbers (mpXnn) of the measurement points, and
   the technology-specific definition of any measurement point other
   than X00 and X90 with sufficient detail to clearly define its
   location (similar to the technology-specific examples in Section 6 of
   this document).

   If the number of intermediate networks (between the source and
   destination) is not known or is unstable, then this SHOULD be
   indicated on the diagram, and results from measurement points within
   those networks need to be treated with caution.


   o  The terminology "on-net" and "off-net" is sometimes used when
      referring to the subscriber's Internet Service Provider (ISP)
      measurement coverage.  With respect to the reference path, tests
      between mp100 and mp190 are "on-net".

   o  Widely deployed broadband Internet access measurements have used
      pass-through devices [SK] (at the subscriber's location) directly
      connected to the service demarcation point; this would be located
      at mp100.

   o  The networking technology must be indicated for the measurement
      points used, especially the interface standard and configured
      speed (because the measurement connectivity itself can be a
      limiting factor for the results).

   o  If it can be shown that a link connecting to a measurement point
      has reliably deterministic performance or negligible impairments,
      then the remote end of the connecting link is an equivalent point
      for some methods of measurement (although those methods should
      describe this possibility in detail, it is not in scope to provide
      such methods here).  In any case, the presence of a link and
      claimed equivalent measurement point must be reported.

   o  Some access network architectures may have an additional traffic
      aggregation device between mp100 and mp150.  Use of a measurement
      point at this location would require a local number and diagram.

   o  A Carrier Grade NAT (CGN) deployed in the service provider's
      access network would be positioned between mp100 and mp190, and
      the egress side of the CGN may be designated mp150.  mp150 is
      generally an intermediate measurement point in the same address
      space as mp190.

   o  In the case that private address space is used in an access
      architecture, mp100 may need to use the same address space as its
      "on-net" measurement point counterpart so that a test between
      these points produces a useful assessment of network performance.
      Tests between mp000 and mp100 could use a different private
      address space, and when the globally routable side of a CGN is at
      mp150, the private address side of the CGN could be designated
      mp149 for tests with mp100.

   o  Measurement points at transit GRA GWs are numbered mpX00 and
      mpX90, where X is the lowest positive integer not already used in
      the path.  The GW of the first transit network is shown with point
      mp200 and the last transit network GW with mpX90.

6.  Examples of Reference Paths with Various Technologies

   This section and those that follow are intended to provide example
   mappings between particular network technologies and the reference

   We provide an example for 3G cellular access below.

   Subscriber -- Private ---  Service ------------- GRA --- Transit ...
   device         Net #1      Demarc.                GW     GRA GW
   mp000                       mp100                mp190    mp200

   |_____Unmanaged sub-path_____|____Managed sub-path_____|

      GRA = Globally Routable Address
       GW = Gateway
       UE = User Equipment
      RAN = Radio Access Network
     GGSN = Gateway General Packet Radio Service (GPRS) Support Node

        Figure 3: Example of Reference Path with 3G Cellular Access

   Next, we provide an example of DSL access.  Consider the case where:

   o  The Customer Premises Equipment (CPE) has a NAT device that is
      configured with a public IP address.

   o  The CPE consists of a wired residential GW and modem internally
      connected (via Private Net #2) to an embedded home router and WiFi
      access point (Private Net #1).  All subscriber devices (UE) attach
      to the CPE through the WiFi access. mp100 is on the modem side of
      Private Net #2.

   We believe this is a fairly common configuration in some parts of the
   world and is fairly simple as well.

   This case would map into the defined reference measurement points as

Subsc. -- Private -- Private -- Service-- Intra IP -- GRA -- Transit ...
device     Net #1     Net #2    Demarc.    Access     GW     GRA GW
mp000                            mp100      mp150    mp190    mp200
                                   |------DSL Network---|
|________Unmanaged sub-path________|__Managed sub-path__|

                GRA = Globally Routable Address
                 GW = Gateway
               BRAS = Broadband Remote Access Server

            Figure 4: Example of Reference Path with DSL Access

   Consider another access network case where:

   o  The CPE is a NAT device that is configured with a private IP

   o  There is a CGN located deep in the access ISP network.

   o  The CPE is a home router that has also an incorporated a WiFi
      access point and this is the only networking device in the home
      network, all endpoints attach directly to the CPE through the WiFi

   We believe this is becoming a fairly common configuration in some
   parts of the world.

   This case would map into the defined reference measurement points as

Subsc. -- Private ------------- Service-- Intra IP -- GRA -- Transit ...
device     Net #1               Demarc.    Access     GW     GRA GW
mp000                            mp100      mp150    mp190    mp200
                                   |--Access Network---|
|________Unmanaged sub-path________|_Managed sub-path__|

                GRA = Globally Routable Address
                 GW = Gateway
                CGN = Carrier Grade NAT

               Figure 5: Example of Reference Path with CGN

7.  Example of Reference Path with Resource Transition

   This section gives an example of shared and dedicated portions with
   the reference path.  This example shows two resource transition

   Consider the case where:

   o  The CPE consists of a wired residential GW and modem (Private Net
      #2) connected to a WiFi access point (Private Net #1).  The
      subscriber device (UE) attaches to the CPE through the WiFi

   o  The WiFi subnetwork (Private Net #1) shares unlicensed radio
      channel resources with other WiFi access networks (and potentially
      other sources of interference); thus, this is a shared portion of
      the path.

   o  The wired subnetwork (Private Net #2) and a portion of the service
      provider's network are dedicated resources (for a single
      subscriber); thus, there is a resource transition point between
      Private Net #1 and Private Net #2.

   o  Subscriber traffic shares common resources with other subscribers
      upon reaching the CGN; thus, there is a resource transition point
      and further network components are designated as shared resources.

   We believe this is a fairly common configuration in parts of the

   This case would map into the defined reference measurement points as

Subsc. -- Private -- Private -- Access -- Intra IP -- GRA -- Transit ...
device     Net #1     Net #2    Demarc.    Access     GW     GRA GW
mp000                            mp100      mp150    mp190    mp200
       |   WiFi   |  1000Base-T    |--Access Network---|

       |-Shared--|RT|------Dedicated------| RT  |-----Shared------...
|_______Unmanaged sub-path________|_Managed sub-path__|

                GRA = Globally Routable Address
                 GW = Gateway
                 RT = Resource Transition Point

     Figure 6: Example of Reference Path with Two Reference Transition

8.  Security Considerations

   Specification of a reference path and identification of measurement
   points on the path represent agreements among interested parties.
   They present no threat to the implementors of this memo, or to the
   Internet resulting from implementation of the guidelines provided

   Attacks at end hosts or identified measurement points are possible.
   However, there is no requirement to include IP addresses of hosts or
   other network devices in a reference path with measurement points
   that is compliant with this memo.  As a result, the path diagrams
   with measurement point designation numbers do not aid such attacks.

   Most network operators' diagrams of reference paths will bear a close
   resemblance to similar diagrams in relevant standards or other
   publicly available documents.  However, when an operator must include

   atypical network details in their diagram, e.g., to explain why a
   longer latency measurement is expected, then the diagram reveals some
   topological details and should be marked as confidential and shared
   with others under a specific agreement.

   When considering privacy of those involved in measurement or those
   whose traffic is measured, there may be sensitive information
   communicated to recipients of the network diagrams illustrating paths
   and measurement points described above.  We refer the reader to the
   privacy considerations described in the Large Scale Measurement of
   Broadband Performance (LMAP) Framework [LMAP-FRAMEWORK], which covers
   active and passive measurement techniques and supporting material on
   measurement context.  For example, the value of sensitive information
   can be further diluted by summarizing measurement results over many
   individuals or areas served by the provider.  There is an opportunity
   enabled by forming anonymity sets described in [RFC6973] based on the
   reference path and measurement points in this memo.  For example, all
   measurements from the subscriber device can be identified as "mp000",
   instead of using the IP address or other device information.  The
   same anonymization applies to the Internet service provider, where
   their Internet gateway would be referred to as "mp190".

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997,

   [RFC2330]  Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
              "Framework for IP Performance Metrics", RFC 2330, May
              1998, <http://www.rfc-editor.org/info/rfc2330>.

   [RFC3432]  Raisanen, V., Grotefeld, G., and A. Morton, "Network
              performance measurement with periodic streams", RFC 3432,
              November 2002, <http://www.rfc-editor.org/info/rfc3432>.

   [RFC5835]  Morton, A. and S. Van den Berghe, "Framework for Metric
              Composition", RFC 5835, April 2010,

9.2.  Informative References

              Eardley, P., Morton, A., Bagnulo, M., Burbridge, T.,
              Aitken, P., and A. Akhter, "A framework for large-scale
              measurement platforms (LMAP)", Work in Progress,
              draft-ietf-lmap-framework-10, January 2015.

   [Q.1741]   International Telecommunications Union, "IMT-2000
              references to Release 9 of GSM-evolved UMTS core network",
              ITU-T Recommendation Q.1741.7, November 2011,

   [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>.

   [SK]       Crawford, S., "Test Methodology White Paper", SamKnows
              Whitebox Briefing Note , July 2011,

   [Y.1541]   International Telecommunications Union, "Network
              performance objectives for IP-based services", ITU-T
              Recommendation Y.1541, November 2011,


   Thanks to Matt Mathis, Charles Cook, Dan Romascanu, Lingli Deng, and
   Spencer Dawkins for review and comments.

Authors' Addresses

   Marcelo Bagnulo
   Universidad Carlos III de Madrid
   Av. Universidad 30
   Leganes, Madrid  28911

   Phone: 34 91 6249500
   EMail: marcelo@it.uc3m.es
   URI:   http://www.it.uc3m.es

   Trevor Burbridge
   Adastral Park, Martlesham Heath
   United Kingdom

   EMail: trevor.burbridge@bt.com

   Sam Crawford

   EMail: sam@samknows.com

   Philip Eardley
   Adastral Park, Martlesham Heath
   United Kingdom

   EMail: philip.eardley@bt.com

   Al Morton
   AT&T Labs
   200 Laurel Avenue South
   Middletown, NJ
   United States

   EMail: acmorton@att.com