Large-Scale Measurement of Broadband Performance: Use Cases, Architecture and Protocol Requirements

Versions: 00                                                            
LMAP                                                      H. Schulzrinne
Internet-Draft                                               W. Johnston
Intended status: Informational                                 J. Miller
Expires: March 25, 2013                                              FCC
                                                      September 21, 2012

     Large-Scale Measurement of Broadband Performance:  Use Cases,
                 Architecture and Protocol Requirements


   Measuring broadband performance on a large scale is important for
   network diagnostics by providers and users, as well for as public
   policy.  To conduct such measurements, user networks gather data,
   either on their own initiative or instructed by a measurement
   controller, and then upload the measurement results to a designated
   measurement server.  This document describes a logical architecture
   and summarizes key requirements for protocols to connect the
   components.  The system is designed to support residential and small-
   enterprise networks, using either wired or wireless networks.  The
   architecture supports an extensible set of active and passive
   measurements, but the details of the metrics themselves are beyond
   the scope of this document.

Status of this Memo

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Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Use Cases  . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   3.  Architecture Overview  . . . . . . . . . . . . . . . . . . . .  8
     3.1.  Measurement client . . . . . . . . . . . . . . . . . . . .  8
     3.2.  Measurement server . . . . . . . . . . . . . . . . . . . .  8
     3.3.  Measurement controller . . . . . . . . . . . . . . . . . .  8
     3.4.  Data collector . . . . . . . . . . . . . . . . . . . . . .  8
     3.5.  Network parameter server . . . . . . . . . . . . . . . . .  9
   4.  Protocols  . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   5.  Initiation of Measurements . . . . . . . . . . . . . . . . . . 12
   6.  Requirements . . . . . . . . . . . . . . . . . . . . . . . . . 13
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 16
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 17
   9.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 19
     10.2. Informative References . . . . . . . . . . . . . . . . . . 19
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 20

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1.  Introduction

   Measuring actual network performance is crucial to managing consumer
   and enterprise networks, but, when performed at scale, it also allows
   third parties to gain insight into the actual performance of such
   networks, facilitating consumer choice and allowing to evaluate the
   state of broadband performance in a country, among other public
   policy goals.  A number of network performance metrics have been
   defined, such as [2], but there is no overall architecture and set of
   protocols that facilitates gathering such measurements in a
   coordinated way, at scales drawing on thousands or millions of nodes.

   Large-scale measurement efforts (e.g., [3]) use proprietary, custom-
   designed mechanisms to coordinate the measurement clients.  They
   require that the organization running the measurements deploy
   thousands of dedicated hardware components or rely on end-system
   software modules that are subject to exogeneous factors, such as home
   networks, that may distort the results.  Thus, this document proposes
   an overall architecture, with emphasis on the functional and security
   requirements for the protocols connecting the elements of the
   architecture, that will make it possible to build measurement
   capabilities into home and enterprise edge routers, personal
   computers, mobile devices and other edge devices.

   Any usage and implementation will likely impose a number of
   additional operational requirements and a statistical sampling
   methodology.  For example, the Measurement Broadband America project
   [3] within the US Federal Communications Commission (FCC) has
   established specific operational guidelines on data validity and
   commits to specific requirements for open access to measurement data,
   software tools and documentation of measurement methodology and
   statistical approaches.  While crucial for deployment, these are
   beyond the scope of this protocol requirements document.  Also, as is
   customary for IETF-managed protocols, this document does not mandate
   a specific hardware or operating system platform for implementation.

   We suggest that the IETF IP Performance Metrics (IPPM) working group
   take on defining any additional performance metrics as needed.  Such
   an effort should be undertaken as a collaborative effort with the
   Broadband Forum (BBF) [4]; other SDOs may also take on aspects of
   this problem area.

   In some applications, such as data gathering by local regulatory
   entities, extensive logging at various levels, from packet arrival
   times to events, will be used to assure all parties of the validity
   of the data gathered.  However, logging is beyond the scope of this

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   Both active and passive measurement techniques have been widely
   accepted in practice.  In active measurements, the end systems emits
   traffic and observes a performance metric, or has another end point
   do so.  Examples of active measurements include round-trip delay [2],
   one-way delay [5] and throughput [6] metrics, service availability,
   as well as a range of measurements that try to emulate application
   behavior, such as VoIP, HTTP retrievals or media streaming.  Passive
   measurements observe existing user traffic flows.  We note that there
   is some overlap between NetFlow [7] measurements and passive
   measurements described here.  The delineation between the two and
   possible re-use of functionality are left to further discussion.

   For both active and passive measurements, a measurement client sends
   or observes traffic, respectively.  For active measurements, the
   measurement client may need a measurement server as serve as
   recipient of the measurement traffic.  (In some cases, such as
   measurements modeling user access to network services, such as web
   page retrieval performance, the measurement traffic is exchanged with
   a production server, such as a web server, but this requires careful
   design to avoid overloading that server with measurement traffic.)
   Since we are interested in large-scale measurements, we assume that a
   measurement controller provides the measurement client with
   information on what to measure and when to perform the measurements.
   Finally, in some cases, a measurement data collector gathers data,
   typically samples rather than aggregate data, collected by the
   measurement clients for later analysis.  The data models and file
   formats for supporting the exchange of the test parameters as well as
   test results require standardization.

   As noted above, it appears likely that metrics will evolve and new
   ones will be added over time.  Components of the platform may be
   designed and operated by different, independent entities, or, at
   minimum, data gathered by the platform may be used by different
   parties for different purposes.  For example, a regulator or ISP
   might contract with third parties to manage various components of a
   measurement effort, and all data communications must securely support
   the delegation and authentication of rights and responsibilities to
   perform any operational parameter supported by the measurement
   architecture.  Thus, it will be important to agree to on a set of
   metrics and associated metric-specific protocol parameters.  For
   example, the TCP throughput metric defined in [6] depends on the TCP
   congestion avoidance algorithm.  Each measurement run generates one
   or more data samples, e.g., a set of throughput values.  The
   controller needs to convey those parameters to the measurement client
   and the data collector needs to be able to determine unambiguously
   which parameters were used for a specific set of data samples.

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",

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   document are to be interpreted as described in [1].  Although RFC
   2119 was written with protocols in mind, the key words are used in
   this document to indicate the strength of a requirement.

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2.  Use Cases

   Large-scale, automated measurements are helpful in a number of use
   cases.  We illustrate the scope with three examples:

   Provider network measurements:  Internet service providers have an
      interest in knowing how well their networks are performing, as
      viewed from their customers' perspective.  Such performance
      information allows them to identify bottlenecks and observe the
      impact of changes in user behavior, e.g., the emergence of new
      network applications or time-of-day patterns.  Here, the provider
      is not interested in the performance of an individual edge network
      or device, but rather wants to get a statistically-valid sample of
      performance across their network.  Service providers may be
      interested in both the end device performance, i.e., the
      performance as seen by edge devices in home and enterprise
      networks, as well as the edge performance, i.e., as seen by the
      network device directly attached to their network, such as a cable
      modem, DSL modem or enterprise edge router.  To reduce the network
      load, providers are unlikely to gather measurements from all
      clients all the time, but rather sample randomly across both time
      and their user population.  The measurement controller directs the
      measurement client what measurements are to be performed, what
      measurement servers to use, when to measure and at which data
      collector it should deposit the measurement data.

   User network diagnostics:  End users may want to determine whether
      their network is performing according to the specifications (e.g.,
      service level agreements) offered by the Internet service
      provider, or they may want to diagnose whether components of their
      network path are impaired.  End users may perform measurements on
      their own, using the measurement infrastructure they provide or
      infrastructure offered by a third party, or they may work directly
      with their network or application provider to diagnose a specific
      performance problem.  Depending on the circumstances, measurements
      may occur at specific pre-defined intervals, or may be triggered
      manually.  A system administrator may perform such measurements on
      behalf of the user.

   Multi-provider network measurements:  As an extension of the first
      use case, multiple network providers and third parties, such as a
      regulatory body, may collaborate to gather network performance
      data on a one-time or recurring basis, using a subset of customers
      of the service providers.  The form of collaboration is beyond the
      scope of this paper, however it should be understood that a data
      collection platform must serve multiple stakeholder interests.

   In the description above, the network provider can either be a

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   commercial or not-for-profit entity distinct from the network edge
   users, or it can be the information technology department in a local
   area network.  Particularly for the user diagnostics use case, it may
   be helpful for the measurement client to obtain parameters of their
   connectivity, such as the nominal uplink and downlink speed.  In
   other cases, only the entity performing the data analysis may need to
   know the nominal performance parameters.

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3.  Architecture Overview

   We define a measurement platform to consist of one or more
   measurement clients, measurement controllers and data collection
   servers.  Based on the use cases above, we summarize their functions

3.1.  Measurement client

   The measurement client is the reference point for measurements.  For
   active measurements, it sends measurement traffic to the measurement
   server or other network elements.  For passive measurements, it
   observes network performance metrics.  Client measurement
   functionality must be implementable in a variety of user contexts and
   provide for communications within different network segments, such as
   the access link between a broadband subscribers modem and an ISP
   network, as well as consumer electronic device communicating to
   measurement server features in a wireless LAN device.

3.2.  Measurement server

   The measurement server is only needed for active measurements that
   require two network nodes.  The measurement server typically operates
   as a traffic source or sink.  To allow scaling, different clients
   within a measurement platform may use different measurement servers.
   Clients may also select, for example, the closest measurement server
   if the influence of wide-area connectivity on measurement results is
   to be minimized.

3.3.  Measurement controller

   The measurement controller provides the measurement client with
   instructions on when and how to conduct what measurements, i.e., the
   measurement schedule.  For example, it might instruct the client to
   conduct a particular kind of throughput measurement every ten
   minutes, and to deposit the throughput samples into a particular data
   collector.  Measurement controllers may be capable of accepting
   inputs from other controllers, scaling up the scope of the
   measurement system.  As one example, an ISP operating a testing
   platform for its own network may accept test requests from an
   external controller as part of a nationwide testing program that it
   is participating in.

3.4.  Data collector

   The data collector collects time-stamped measurement samples from
   measurement clients.  It generally makes these measurement samples
   available only to authorized users.  The data collector may store

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   measurement samples in a database or as files and may make them
   available via download or SQL query.  Access control, internal data
   storage and access methods to data are beyond the scope of this

   We logically separate the data collector from the measurement server
   for both functional and performance reasons.  In general, data
   collected should not be transferred to the collector while a
   measurement is in progress.  Also, a measurement client on a mobile
   host may decide to delay transferring measurement data until a low-
   cost or high-speed connection to the server becomes available.

3.5.  Network parameter server

   In some of the use cases, it is necessary for the analysis to compare
   the measured against the nominal network performance, or correlate
   measured parameters with the type and key parameters of the userOs
   network connection.  For example, for evaluating network delay
   measurements, it is helpful to know what kind of access technology
   (e.g., FTTP, DSL, cable, cellular data or satellite) and nominal
   speed the network connection offers.

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4.  Protocols

   With the description of the elements above and the relationships
   between them, a set of protocols needs to be defined.  The key
   functions of the protocols are described briefly below.

   Measurement client to measurement server:  Each metric will have its
      own set of measurement protocols, and these are beyond the scope
      of this document.  For example, a VoIP metric may use a defined
      set of UDP packets to estimate performance.

   Measurement client to measurement controller:  The measurement client
      queries the measurement controller to obtain an updated
      measurement schedule.  The measurement schedule returned by the
      controller indicates the type of measurements the measurement
      client should perform, the measurement servers and on what
      schedule to conduct the measurements.  For example, it might
      indicate to run a VoIP emulation test every day for ten minutes to
      a specific server, spanning a one-week measurement campaign.  The
      collector also indicates one or more addresses of data collectors
      to the client.

   Measurement controller to measurement controller:  A measurement
      controller can request that another controller undertake a
      specific testing program and could indicate specific tests,
      schedules and sample parameters appropriate to the intended
      objectives.  Other data could include the identity and identity
      verification of the requester, a specific test identifier, e.g.
      Nationwide Test XX, and information necessary for the data
      collector so that data is accessible to authorized parties.

   Measurement client to data collector:  The measurement client will
      typically perform one or more measurements, and then, during the
      pause between measurements, transmit the collected samples to the
      data collector.  The samples must be tagged with identifying
      information, such as when they were collected, edge device
      information (e.g., the mobile device or cable modem) and which
      measurement host was used.  For mobile measurements, the sample
      data is likely to contain location data, possibly of reduced
      spatial resolution to protect user privacy.

   Measurement client to network parameter server:  The measurement
      client may query the network parameter server, typically located
      in the service providers network, for information about its
      nominal service parameters, based on its network address, link
      layer address, or hardware identifiers such as the IMEI for mobile
      nodes.  The data returned may include information such as nominal
      uplink and downlink speeds, data quotas and physical and data link

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      layer technology.  (Data quotas may be important for deciding
      which data-intensive measurements a client wishes to run.)

      While basic network connection information is unlikely to change
      rapidly, it may change at unpredictable instants.  For example, a
      network provider may upgrade the connection speed of subsets of
      their customers, customers may change their subscription or
      provider may adjust the monthly data transfer quota.

      We assume that the measurement server, controller and data
      collector cooperate in configuring appropriate parameters.  For
      example, the controller needs to be able to determine which
      measurement servers and data collectors are currently available
      and the client is authorized to use.  Discovery of suitable data
      collectors is considered beyond the scope of this effort.

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5.  Initiation of Measurements

   Either the client or the measurement controller could in principle
   initiate measurements.  For periodic measurements or one-off user-
   triggered diagnostics, it is sufficient for the end system to contact
   the controller, e.g., periodically every week.  Client-initiated
   measurements have a number of advantages.  In particular, they make
   it less likely that measurement hosts can be abused to generate
   denial-of-service traffic.  They also avoid problems allowing inbound
   requests through network address translators (NATs) and firewalls.

   However, there may be cases where the network provider wishes to
   initiate a one-time measurement or change the measurement parameters
   before the client next contacts the controller.  For such cases, a
   publish-subscribe mechanism may be considered, where the measurement
   client subscribes to measurement schedule updates with the
   measurement controller.

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6.  Requirements

   We distinguish requirements for the different component by a prefix:
   Requirements labeled A-* describe the overall platform architecture,
   M-* indicate requirements primarily affecting the measurement client,
   C-* those for the controller, D-* for the data collector and N-* for
   the functions necessary to obtain network parameter.  In many cases,
   a single requirement governs more than one entity or protocol, so the
   labeling should be considered rough.

   A-1:  The architecture MUST allow for one-time measurements initiated
      by end users, sampled measurements initiated by network providers
      and measurements by one or more third parties.

   A-2:  Measurement clients and servers MUST support an extensible set
      of performance metrics.

   A-3:  Measurement clients, measurement servers and data collectors
      MAY be operated by different administrative entities, including
      entities other than the Internet service provider.

   A-4:  Measurement clients MUST be able perform both active and
      passive measurements.

   A-6:  All entities MUST be able to authenticate the entities they
      communicate with.

   A-7:  Each measurement sample MUST be unambiguously associated with
      the measurement parameters, either by reference or by value.

   A-8:  To ensure availability and scaling, implementations MUST be
      able to implement multiple measurement controllers, measurement
      servers and data collectors with appropriate load balancing and

   M-1:  The architecture MUST allow a single measurement client to
      participate in one or more independent measurement platforms.

   M-2:  A measurement client SHOULD be able to automatically switch
      from a non-responsive to an alternate measurement server.

   M-3:  A measurement client MUST be able to register with the data
      collection platform automatically, announcing its availability and
      relevant system parameters.  (For example, a cable or DSL modem
      may indicate its make and model number.)

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   M-4:  A measurement client MUST be able to declare what kind of
      measurements it can perform, e.g., by enumerating a set of
      measurement identifiers.

   C-1:  The measurement system MUST support measurements that are
      scheduled according to a pre-defined calendar.

   C-2:  The measurement controller MUST be able to specify the interval
      on how often it wishes to be contacted for updated measurement

   C-3:  A measurement client SHOULD be able to automatically discover
      controllers provided by their Internet service provider.

   C-4:  A measurement client MUST be able to authenticate and authorize
      the measurement controller.

   C-5:  The data exchange between the client and controller MUST allow
      for optional encryption and integrity protection.

   D-1:  The protocol messages for measurement samples MUST allow new
      measurement types and parameters.

   D-2:  It MUST be possible to protect the integrity and
      confidentiality of the measurement data exchanged between the
      measurement client and the data collector.

   D-3:  The data exchange protocol between measurement server and data
      collector SHOULD allow the definition of common data elements,
      e.g., for network addresses and timestamps.

   D-4:  The measurement client SHOULD be able to automatically fail
      over to alternate data collectors.

   D-5:  Clients MUST be able to either send data immediate or delay
      sending measurement data to the collector, e.g., to use a low-
      traffic period or a low-cost network.

   D-6:  Clients MUST be able to interleave data samples from different
      measurement metrics to the data collector.

   D-7:  The data collector SHOULD be able to ascertain whether the
      measurement client clock is at least approximately synchronized to
      its own.

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   D-8:  The data exchange between measurement client and data collector
      MUST be subject to flow and congestion control.

   D-9:  The measurement client MUST be able to ascertain that it is
      initiating a session with the desired data collector rather than
      an impostor.

   N-1:  Measurement clients SHOULD be able to obtain nominal network
      service parameters in a machine-readable format, such as
      advertised speed and typical latency.  (This may not be necessary
      in all measurement use cases.)

   N-2:  The set of network parameters MUST be extensible in a backward-
      compatible manner.

   N-3:  The measurement client SHOULD be able to determine the network
      parameter server without manual configuration.

   N-4:  The protocol between measurement client and network parameter
      server SHOULD support a variety of client identifiers, such as
      network addresses, link-layer addresses, AAA identifiers or
      hardware identifiers.

   N-5:  The data exchanged between the network parameter server and the
      measurement client SHOULD ensure its confidentiality and

   N-6:  The protocol SHOULD support suitable authentication
      functionality to restrict access to network parameters to
      authorized nodes.  Authorized nodes may include third parties,
      such as data collectors.

   N-7:  The entity querying the network parameter server MUST be able
      to assure itself that it is communicating with an authentic

   N-8:  Clients of the network parameter server SHOULD be able to be
      automatically informed of changes in parameters.

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7.  Security Considerations

   The large-scale measurement architecture has to prevent third
   parties' use of the measurement clients in bot-nets or for other
   nefarious or malicious purposes.  A malicious third party could cause
   a measurement client to initiate probe traffic to victim hosts rather
   than measurement servers.  We rely on user-initiated requests,
   secured with transport-layer security and server certificates, to
   ensure that only user-authorized entities issue control commands.
   Users may also authenticate themselves via local shared secrets.  We
   note that there are similarities in approach with M2M data
   communications and we suggest that reference of ongoing work on the
   M2M signaling gateway framework or other models may be useful.

   Measurements may also inadvertently expose information that the owner
   of the measurement client considers privacy-sensitive.  Privacy
   considerations may differ depending on whether the measurement
   client, measurement server or data collector are operated by the same
   entity or not, and what trust relationships these entities have with
   each other.  It must be possible to protect the confidentiality of
   the measurement data exchanged between the measurement client and the
   data collector.  For mobile measurements, location information is
   likely to be crucial to interpreting measurement results.  A
   measurement client may want to substitute rough location [8] to
   reduce the ability of a third party to track its movements and

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8.  IANA Considerations

   This document does not request any IANA actions.

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9.  Acknowledgements

   The document is based on discussion within the FCC Measuring
   Broadband America project.

   DISCLAIMER: The opinions expressed are those of the author and do not
   necessarily represent the views of the Federal Communications
   Commission or the United States Government

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10.  References

10.1.  Normative References

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

10.2.  Informative References

   [2]  Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip Delay
        Metric for IPPM", RFC 2681, September 1999.

   [3]  Federal Communications Commission, "Measuring Broadband
        America", September 2012.

   [4]  Broadband Forum, "Liaison Statement: New Project - Broadband
        Access Service Attributes and Performance Measures",
        August 2012.

   [5]  Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way Delay
        Metric for IPPM", RFC 2679, September 1999.

   [6]  Mathis, M. and M. Allman, "A Framework for Defining Empirical
        Bulk Transfer Capacity Metrics", RFC 3148, July 2001.

   [7]  Claise, B., "Cisco Systems NetFlow Services Export Version 9",
        RFC 3954, October 2004.

   [8]  Barnes, R. and M. Lepinski, "Using Imprecise Location for
        Emergency Context Resolution", Internet
        draft draft-ietf-ecrit-rough-loc-05, July 2012.

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Authors' Addresses

   Henning Schulzrinne
   Federal Communications Commission - See Disclaimer
   445 12th Street SW
   Washington, DC  20554

   Phone: +1 202 418 1544

   Walter Johnston
   Federal Communications - See Disclaimer
   445 12th Street SW
   Washington, DC  20554

   Phone: +1 202 418 0807

   James Miller
   Federal Communications Commission - See Disclaimer
   445 12th Street SW
   Washington, DC  20554

   Phone: +1 202 418 7351

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