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Versions: 00 01 02 03

Network Working Group                                         M. Bagnulo
Internet-Draft                                                      UC3M
Intended status: Standards Track                            T. Burbridge
Expires: April 24, 2014                                               BT
                                                             S. Crawford
                                                                SamKnows
                                                        J. Schoenwaelder
                                                               V. Bajpai
                                                       Jacobs University
                                                        October 21, 2013


                  Large MeAsurement Platform Protocol
                       draft-bagnulo-lmap-http-01

Abstract

   This documents specifies the LMAP protocol based on HTTP for the
   Control and Report in Large Scale Measurement Platforms.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on April 24, 2014.

Copyright Notice

   Copyright (c) 2013 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
   (http://trustee.ietf.org/license-info) 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.  Code Components extracted from this document must



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   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Overview . . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Naming Considerations  . . . . . . . . . . . . . . . . . . . .  5
   4.  Information model  . . . . . . . . . . . . . . . . . . . . . .  6
   5.  Example  . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
   6.  Transport protocol . . . . . . . . . . . . . . . . . . . . . . 13
     6.1.  Pre-configured information . . . . . . . . . . . . . . . . 13
     6.2.  Control Protocol . . . . . . . . . . . . . . . . . . . . . 13
       6.2.1.  Retrieving Instructions  . . . . . . . . . . . . . . . 13
       6.2.2.  Handling communication failures  . . . . . . . . . . . 16
       6.2.3.  Pushing Information from the Controller to the MA  . . 16
     6.3.  Report protocol  . . . . . . . . . . . . . . . . . . . . . 17
       6.3.1.  Handling communication failures  . . . . . . . . . . . 18
   7.  LMAP Data Model  . . . . . . . . . . . . . . . . . . . . . . . 18
   8.  Security considerations  . . . . . . . . . . . . . . . . . . . 18
   9.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 20
   10. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 21
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 21
     11.2. Informative References . . . . . . . . . . . . . . . . . . 21
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21























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1.  Introduction

   A Large MeAsurement Platform (LMAP) is an infrastructure deployed in
   the Internet that enables performing measurements from a very large
   number of vantage points.

   The main components of a LMAP are the following:
   o  The Measurement Agents (MAs): these are the processes that perform
      the measurements.  The measurements can be both active or passive
      measurements.  In the case of active measurements, we can
      distinguish two different roles, the Measurement Agent and the
      Measurement Peer.  The MA is the one that is instructed by the
      Controller to perform the measurements.  The Measurement Peer is
      the one that receives measurement packets and replies.
   o  The Controller: this is the element that controls the MAs.  In
      particular it provides configuration information and it instructs
      the MA to perform a set of measurements.
   o  The Collector: this is the repository where the MAs send the
      results of the measurements that they have performed.

   These and other terms used in this document are defined in
   [I-D.ietf-lmap-framework].  We only include the definition of the
   main elements in this document so it is self-contained and can be
   read without the need to consult other documents.  The reader is
   referred to the terminology draft for further details.

   In order for a LMAP to work, the following protocols are required:
   o  Measurement protocols: These are the protocols used between the MA
      and the Measurement Peer in active measurements.  These are the
      actual packets being used for the measurement operations.
   o  Control Protocol.  This is the protocol between the Controller and
      the MAs.  This protocol is used to convey both configuration
      information and measurement instructions from the Controller to
      the MA as well as logging information and capabilities information
      from the MA to the Controller.
   o  Report Protocol.  This is the protocol between the MAs and the
      Collector.  This protocol conveys information about the results of
      the measurements performed by the MA to the Collector.

   Both the Control protocol and the Report protocol have essentially
   two parts:a transport and a data model.  The data model represents
   the information about measurement instructions and configuration (in
   the Control protocol) and the information about measurement results
   (in the Report protocol) that is being exchanged between the parties.
   The transport is the underlying protocol used to exchange that
   information.  This document specifies the use of HTTP 1.1 RFC 2616
   [RFC2616] as a transport for the Control and the Report protocol.
   This document also defines the data model for the Control and Report



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   protocols.  The data model described in this document follows the
   information model described in
   [I-D.burbridge-lmap-information-model].  The Measurement protocols
   are out of the scope for this document.

   At this stage, the goal of this document is to explore different
   options that can be envisioned to use the HTTP protocol to exchange
   LMAP information and to foster discussion about which one to use (if
   any).  Because of that, the document contains several discussion
   paragraphs that explore different alternative approaches to perform
   the same function.


2.  Overview

   This section provides an overview of the architecture envisioned for
   a LMAP using HTTP as transport protocol.  As we described in the
   previous section, a LMAP is formed by a large number of MAs, one or
   more Controllers and one or more Collectors.  We assume that before
   the MAs are deployed, it is possible to pre-configure some
   information in them.  Typically this includes information about the
   MA itself (like its identifier), security information (like some
   certificates) and information about the Controller(s) available in
   the measurement platform.  Once that the MA is deployed it will
   perform the following operations:
   o  After the MA is deployed, it will obtain Instructions from one of
      the pre-configured Controllers.  These Instructions include
      information about the set of measurements to be performed, a
      schedule for the execution of the measurements as well as a set of
      report channels.  This information is downloaded by the MA from
      the Controller.  The MA will periodically check whether there are
      new Instructions available from the Controller.  This document
      specifies how the MA uses the HTTP protocol to retrieve
      information from the Controller.
   o  The MA will execute measurements either by passively listening to
      traffic or by actively sending and receiving measurement packets.
      How this is done is out of the scope of this document.
   o  After one or more measurements have been performed, the MA reports
      the results to the Collector.  The timing of these uploads is
      specified in the measurement Instruction i.e. each measurement
      specified in a measurement Instruction contains a report
      information, defining when the MA should report the results back
      to the Collector.  This document specifies how the MA uses the
      HTTP protocol to upload the measurement results to the Collector.
   o  In addition, the MA will periodically report back to the
      Controller information about its capabilities (like the number of
      interfaces it has, the corresponding IP addresses, the set of
      measurement methods it supports, etc) and also logging information



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      (whether some of the requested measurement tasks failed and
      related information).


3.  Naming Considerations

   In this section we define how the different elements of the LMAP
   architecture are identified and named.

   The Controller and the Collectors can be assumed to have both an IP
   address and a Fully Qualified Domain Name (FQDN).  It is natural to
   use these as identifiers for these elements.  In this document we
   will use FQDNs, but IP addresses can be used as well.

   The MAs on the other hand, are likely to be executed in devices
   located in the end user premises and are likely to be located behind
   a NAT box.  It is reasonable to assume they have neither a public IP
   address nor a FQDN.  We propose then that the MAs are identified
   using an Universally Unique IDentifier URN as defined in RFC 4122
   [RFC4122].  In particular each MA has a version 4 UUID, which is
   randomly or pseudo randomly generated.

   DISCUSSION:
      MA ID Configuration: Some open issues related to this are: a)
      whether the MA ID is configured before of after the MA is
      deployed, b) if configured after deployment whether the MA ID is
      generated locally and posted or fetched from the Controller and c)
      whether this is within the scope of this (or other) specification
      if any.  These issues seem also to be related to the nature of the
      MA platform (wether the MA is a software downloaded into a general
      purpose device or it is a special purpose hardware box).  Consider
      the case that the MA is located in a special purpose hardware box,
      then having the MA ID pre configure before deployment requires a
      per device customization that is expensive.  It would be more
      costly efficient to reuse an existent (hopefully) unique
      identifier available in the hardware (such as a MAC address) to
      serve as a one-time pre configured identifier to be used to fetch
      (or post a self generated) the MA ID from the Controller once the
      MA is deployed.  The requirement for such one-time identifier is
      that they must be unique (which is not always true for the MACs).
      About the local generation of the MA ID (as opposed to fetch it
      from the Controller), the generation process performed in the MA
      MUST be idempotent, i.e. if the MA was factory-reset then the
      server would still see it with the same MA ID when it came back
      up.  This is probably easier to achieve if it is generated in the
      Controller and then fetched by the MA.  Finally, it is not clear
      at this stage if this needs to be specified in this document or in
      the information model document or left open to the implementers.



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      Group identifiers.  In some cases, like the case of measurements
      in mobile devices, it may be important because of privacy
      considerations for the MA not to have a unique identifier.  It is
      possible then to assign "Group identifiers" to a set of devices
      that share relevant characteristics from the measurement
      perspective (e.g. devices from the same operator, with the same
      type of contract or other relevant feature).  In this case, the
      MAs within the same group would retrieve common measurement
      Instructions from the controller by presenting the same Group ID
      and would report results including the Group ID in the report.
      This would imply that it would not be possible for the platform to
      correlate specific measurement data with any given MA.  The
      downside of this is that some MAs may be over-represented while
      other under-represented in the measurement data and it would not
      be possible to detect this case (for instance a given MA may have
      reported 20 results while another one only one).  In order to deal
      with this issue, the MA behaviour must be programmed accordingly
      (e.g. the MA should not perform more than one measurement every
      given period of time).In addition, it should be noted that privacy
      is only achieved in a holistic way.  This means that really
      anonymity of the MA is incompatible with strong authentication.
      In particular, if a measurement platform's goal is to keep MAs
      anonymous, it cannot require any form of strong authentication
      (other than weak group authentication e.g. a password shared by a
      group), which has security implications.  In particular, the
      threat for report forgery (i.e. enabling an attacker to submit
      forged reports as discussed in the security considerations)
      increases.

   There are additional naming considerations related to:
   o  The measurements.  In order to enable a Controller to properly
      convey a measurement schedule, it must be possible for the
      Controller to specify a measurement to be performed while
      providing the needed input parameters.  While this is critical, it
      is out of the scope of this document.  There is a proposed
      registry for metrics/measurements in
      [I-D.bagnulo-ippm-new-registry-independent])
   o  The resources being exchanged, namely, the configuration
      information, the measurement Instructions and the reports.  These
      are being discussed in the upcoming sections.


4.  Information model

   The information model for LMAP is described
   [I-D.burbridge-lmap-information-model].  It contains basically two
   models one for the control information (i.e. the Instructions from
   the Controller to the MA) and a model for the Report information.  We



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   briefly describe their overall structure here.

   The control information (or Instruction) has the following five
   elements:
   o  The Agent Information element.  This contains pointers (URLs) to
      the other 4 elements which contain the actual control information.
      This servers a a level of indirection allowing the MA to have a
      root element from which retrieve all the other elements.
   o  The Set of Measurement Task Configurations: This element defines
      the measurements/test that the MA will perform without defining
      the schedule when they will be performed.
   o  The Set of Report Channels: This element defines the set of
      collectors as well as the reporting schedules for the reports.
   o  The Set of Measurement Schedules for Repeated Tasks: defines the
      schedules for the repeated measurements, by referencing the
      measurement tasks defined in the second element.
   o  The Set of Measurement Schedules for Isolated Tasks: defines the
      schedules for isolated measurements, again by referencing the
      measurement tasks defined in the second element.

   Summary of Report information model here.

   Summary of Status information model here.

   Summary of Logging information model here.

   Summary of Configuration information model here.


5.  Example

   Before describing the actual data models and the options for using
   the HTTP protocol for conveying control and report information, we
   will describe a simple example that hopefully will provide an
   overview of the proposed LMAP protocol.

   Consider a simple scenario with these elements: a Controller with
   FQDN controller.example.org, a Collector with FQDN
   collector.example.org and a MA.

   Suppose we want to instruct the MA to perform the following
   measurement and the following reports:
   o  A UDP latency test, without cross-traffic, that reports the 99th
      percentile mean of a burst of packets sent following a Poisson
      distribution that lasts for 30 seconds and with rate 5 packets per
      second.  The destination address is 192.0.2.1 and the destination
      and source port are 50000.  We want to repeat this test for 7 days
      every hour.  Report the results every hour.



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   Assume that both the Controller and the Collector are deployed.
   Before deploying the MA, the MA must be configured with a UUID.
   Let's suppose the UUID for this particular MA is f47ac10b-58cc-4372-
   a567-0e02b2c3d479.  In addition to its UUID, the MA must be
   configured with the certificate of the CA used to generate the
   certificates for the Controller (i.e. controller.example.org) and the
   collector (i.e. collector.example.org).  In addition, the URL for the
   Instruction information must be configured in the MA.  This URL is
   composed by the FQDN of the Controller plus a well-known path prefix
   (as defined in RFC 5785 [RFC5785]), namely /.well-known/lmap/ma-info.
   For this particular example, the URL for the Instruction is:
   http://controller.example.org/.well-known/lmap/ma-info/

   Once the MA is deployed, it uses the POST method to retrieve the
   Agent Information element of the Instruction from the controller as
   follows
      POST /.well-known/lmap/ma-info/ HTTP/1.1
      Host: controller.example.com
      Content-Type: application/lmap-maid+json
      Accept: application/lmap-config+json
      {
      "ma-id" : "f47ac10b-58cc-4372-a567-0e02b2c3d479",
      }

   The Controller then returns the Agent Information for this specific
   agent which contains basically the URLs for the remaining Control
   elements.  For this particular example, the Agent information
   returned looks like this:


   {
     "ma-id": "f47ac10b-58cc-4372-a567-0e02b2c3d479",
     "version": "1.0",
     "measurement-set": "http://controller.example.org
               /measurements/",
     "report-channel-set": "http://controller.example.org
               /channels/",
     "repeated-schedule-set": "http://controller.example.org
               /schedules/"
     "status-set": "http://controller.example.org
                       /status/"
     "logging-set": "http://controller.example.org
                           /logging/"
   }


   The Agent Information retrieved by the MA contains the URL for the
   remaining elements of the Instruction.  In order to retrieve them,



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   the MA executes the POST method on the retrieved URLs.  This approach
   containing one level of indirections allows that the different
   components (measurements, report channels and measurement schedules)
   are updated with a different frequency.  We expect that the report
   channels will be fairly static, the measurements updated a bit more
   frequently and the schedules to be updated frequently.  This would
   imply that the schedule resource will be retrieved frequently while
   the other two not so much.  In addition, the Agent Information
   retrieved contain the URLs to deliver both status and logging
   information.  The MA will execute the POST method for conveying this
   information to the Controller.

   The first thing that the MA does is to send its status information to
   the Controller. this contains information about the MA capabilities
   and local configuration, such as interfaces' information and
   supported measurement task.  For this particular example, the MA
   would execute the following method:

           POST /.well-known/lmap/ma-info/ HTTP/1.1
           Host: controller.example.com
       Content-Type: application/lmap-maid+json
       Accept: application/lmap-config+json
       {
         "ma-id" : "f47ac10b-58cc-4372-a567-0e02b2c3d479",
             "ma-interfaces: [
                   {"if-name" : eth0
                    "if-type" : ethernetCsmacd
                    "ip-adddress" :{
                           "protocol": v4
                           "address": 10.1.1.1
                           }
                    }]
              "supported-measurements":[
                    {"metric": UDP_Latency}]
       }


   At this point, the Controller has information about the interfaces in
   the MA and the supported measurement methods.  (Please keep in mind
   that this is kept very simple to facilitate the description, but in
   normal operation, it is likely that the configuration will contain
   much more information).

   The MA will next retrieve the set of Instructions from the
   Controller.  The POST for the Instructions will result in the
   following information:





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           {
               "name": "standard tests",
               "version": "1.0",
               "tests": [
                   {
                       "name": "latency",
                       "description": "UDP round trip latency",
                       "metric": "UDP_Latency",
                       "options": [
                           {
                               "environment": "No-cross-traffic",
                               "Output-type": "Xth-percentile-mean",
                               "X": "99",
                               "Scheduling": "Poisson",
                               "rate": "5",
                               "duration": "30.000",
                                                   "interface": "eth0"
                               "destination-ip": {
                                   "version": "4",
                                   "value": "192.0.2.1"
                               },
                               "destination-port": "50000",
                               "source-port": "50000"
                           }
                       ]
                   }
               ]
           }


   The values for "metric", "environment", "Output-type" and
   "scheduling" are defined in the registry specified in
   [I-D.bagnulo-ippm-new-registry-independent].  Many of the values
   under the 'options' field will be dependent on the metric itself, and
   they can therefore use their respective units, naming or values.

   The POST for the report channels retrieves the following:














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                {
                    "name": "internal channels",
                    "version": "1.0",
                    "description": "hourly report to main database collector",
                    "reports": {
                        "name": "hourly report",
                        "description": "hourly report to main database",
                        "collector": "http://collector.example.org/results/f47ac10b-58cc-4372-a567-0e02b2c3d479",
                        "timing": {
                            "timing_type": "calendar",
                            "timing-config": {
                                "minutes": ["22"],
                                "seconds": ["40"]
                            }
                        }
                    }
                }


   The POST for the schedule retrieves the following:

                   {
                       "name": "hourly measurements",
                       "version": "1.0",
                       "schedules": [
                           {
                               "name": "Hourly",
                               "tests": ["latency"],
                               "reports" :["hourly report"],
                               "timing": {
                                   "timing_type": "calendar",
                                   "timing-config": {
                                       "minutes": ["05"],
                                       "seconds": ["30"]
                                   }
                               }

                           }
                       ]
                   }


   At this point, the MA has obtained the information about the
   measurement it has been instructed to perform and it is now ready to
   do it.  It then sends the first batch of UDP packets for 30 seconds.
   Once that it has finished doing this, it calculates the 99th
   percentile mean of the round trip time, let's say that it was 10
   milliseconds.  Since there are no other measurements performed in the



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   next hour, it will report only this result to the Collector.  In
   order to do that, the MA will execute the POST method to the URL
   retrieved in the report channel resource (i.e.
   http://collector.example.org/results/ in this example) and it will
   send the following information:

                   {
                       "report-date": "utc-milliseconds",
                       "reporting-agent": "f47ac10b-58cc-4372-a567-0e02b2c3d479",
                       "results": {
                           "test-name": "latency",
                           "test-agent": "f47ac10b-58cc-4372-a567-0e02b2c3d479",
                           "test-parameters": {
                               "name": "latency",
                               "description": "UDP round trip latency",
                               "metric": "UDP_Latency",
                               "options": [
                                   {
                                       "environment": "No-cross-traffic",
                                       "Output-type": "Xth-percentile-mean",
                                       "X": "99",
                                       "Scheduling": "Poisson",
                                       "rate": "5",
                                       "duration": "30.000",
                                       "destination-ip": {
                                           "version": "4",
                                           "value": "192.0.2.1"
                                       },
                                       "source-IP-address": {
                                           "version": "4",
                                           "value": "198.151.100.34"
                                       },
                                       "destination-port": "50000",
                                       "source-port": "50000",
                                       "start-time": "utc-milliseconds",
                                       "end-time": "utc-milliseconds"
                                   }
                               ]
                           },
                           "test-results": {
                               "Xth-percentile-mean": "10"
                           }
                       }
                   }


   Finally, the MA will use the POST method to convey the logging
   information to the Controller.  We take the approach that only errors



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   are logged, so, in this example, the MA would post an empty log to
   the Controller showing that there were no errors.


6.  Transport protocol

6.1.  Pre-configured information

   As we mentioned earlier, the MAs contain pre-configured information
   before being deployed.  The pre-configured information is the
   following:
   o  The UUID for the MA.  This should be pre-configured so that the
      Controller is aware of the MA and can feed configuration
      information and measurement Instructions to it.
   o  Information about one or more Controllers.  The MA MUST have
      enough information to create the URL for the Instruction
      resources.  This includes the the FQDN of each of the Controller
      or the IP addresses of the Controller, as well as the well-known
      path prefix and its identifier.
   o  The certificate for the Certification authority that is used in
      the platform to generate the certificates for the Controller and
      the Collector.  See the Security considerations section below.
   o  The security related information for the MA (it can be a
      certificate for the MA and the corresponding private key, or
      simply a key/password depending on the security method used, see
      the security considerations section below).

6.2.  Control Protocol

   The Control protocol is used by the MA to retrieve Instruction
   information from the Controller.  In this section we describe how to
   use HTTP to transport Instructions.  The Instruction information is
   structured as defined in the LMAP Information model
   [I-D.burbridge-lmap-information-model] as described in the previous
   section.  The MA uses the Control protocol to retrieve all the
   resources described above, namely, the Agent information, the Set of
   Measurement Task Configurations, the Set of Report Channels, the Set
   of Measurement Schedules for Repeated Tasks and the Set of
   Measurement Schedules for Isolated Tasks.  The main difference from
   the HTTP perspective is that the MA MUST have the URL for the Agent
   Information resource pre-configured as described in the previous
   section, while the URLs for all the other resources are contained in
   the Agent Information resource itself.

6.2.1.  Retrieving Instructions

   In order to retrieve the Instruction resources from the Controller
   the MA can use either the GET or the POST method using the



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   corresponding URL.

6.2.1.1.  Using the GET method

   One way of using the GET method to retrieve configuration information
   is to explicitly name the configuration information resources and
   then apply the GET method.  The MA retrieves its Instruction when it
   is first connected to the network and periodically after that.  The
   frequency for the periodical retrieval is contained in the Agent
   Information (???).

   The URL for the Agent Information resource is formed as the FQDN of
   the Controller, a well-known path prefix and the MA UUID.  The well-
   known path prefix is /.well-known/lmap/ma-info.  The URL for the
   remaining resources that compose the Instruction are contained in the
   Agent Information.

   Agent Information retrieval: In order to retrieve the Agent
   information the MA uses the HTTP GET method follows:
      GET /.well-known/lmap/ma-info/ < ma-iid> HTTP/1.1
      Host: FQDN or IP of the Controller
      Accept: application/json (as per [RFC4627])
   The Agent Information should contain the Configuration Retrieval
   Schedule (i.e. how often the MA should retrieve configuration
   information) and also the Measurement Instruction Retrieval Schedule
   (i.e. how often the MA should retrieve the Measurement Instruction
   from the Controller).  COMMENT: this is missing from the Data Model

   The retrieval of the remaining resources of the Instruction using the
   GET method is analogous, only that the URL is extracted from the
   Agent Information file rather than constructed with pre-configured
   information.

   The format for the response should be described here

   Periodical Instruction retrieval: After having downloaded the initial
   Instruction information, the MA will periodically look for updated
   Instruction information.  The frequency with which the MA polls for
   the new Instructions from the Controller is contained in the last
   Agent Information downloaded.  In order to retrieve the Agent
   Information, the MA uses the GET method as follows:
      GET /.well-known/lmap/ma-info/ma-iid/ HTTP/1.1
      Host: FQDN or IP of the Controller
      Accept: application/json (as per [RFC4627])
      If-None-Match: the eTag of the last retrieved Agent Information
      (an alternative option here is to use If-Modified-Since, not sure
      which one is best)




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   For the other Instruction resources, the GET method is applied in the
   same way just that the URL used are the ones retrieved in the last
   Agent Information.

   The format for the response should be described here

   Alternatively, instead of explicitly naming the Instruction resources
   for each MA, it is possible to perform a query using the GET method
   as well.  In this case, the MA could perform a GET for the following
   URI http://controller.example.org/?ma=maid & q=ma-info (similar
   queries can be constructed for the other Instruction resources).  (I
   am not sure how to express in this case the condition that the MA
   wishes to retrieve the configuration if it is newer than the last one
   it downloaded.)

6.2.1.2.  Using the POST method

   An alternative to retrieve Instruction resources is to use the POST
   method to perform a query (similar to the query using GET).  In this
   case there is no explicit naming of the Instruction information of
   each MA, but a general Instruction resource and the POST method is
   used to convey a query for the Instruction information of a
   particular MA.  For the case of the Agent Information resource, this
   would look like as follows:
      POST /.well-known/lmap/ma-info/ma-iid/ HTTP/1.1
      Host: controller.example.com
      Content-Type: application/lmap-maid+json
      Accept: application/lmap-config+json
      {
      "ma-id" : "550e8400-e29b-11d4-a716-446655440000",
      }

   The reply for this query would contain the actual configuration
   information as follows:
      HTTP/1.1 200 OK
      Content-Length: xxx
      Content-Type: application/lmap-config+json
      {
      // whatever config goes here
      }

   In this case, the URLs contained in the Agent information can be
   generic and not MA specific, since the MA will use the POST method
   including its own identifier when retrieving the Instruction
   resources.

   The argument for this approach is that this is much more extensible
   since the POST can carry complex information and there is no need to



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   "press" arguments into the strict hierarchy of URIs.

   We need to describe how to use this to retrieve newer information in
   the periodic case.

6.2.2.  Handling communication failures

   The cases that the MA is unable to retrieve the Instructions are
   handled as follows:
   o  The MA will use a timeout for the communication of TIMEOUT
      seconds.  The value of TIMEOUT MUST be configurable via the
      aforementioned Configuration Information retrieval protocol.  The
      default value for the TIMEOUT is 3 seconds.  If after the timeout,
      the communication with the Controller has not been established,
      the MA will retry doing an exponential backoff and doing a round
      robin between the different Controllers it has available.
   o  If a HTTP error message (5xx) is received from the Controller as a
      response to the GET request, the MA will retry doing an
      exponential back-off and doing a round robin between the different
      Controllers it has available.  The 5xx error codes indicate that
      this Controller is currently incapable of performing the requested
      operation.

6.2.3.  Pushing Information from the Controller to the MA

   The previous sections described how the MA periodically polls the
   Controller to retrieve Instruction information.  The frequency of the
   downloads is configurable.  The question is whether this is enough or
   a mechanism for pushing Instruction information is needed.  Such
   method would enable to contact the MA in any moment and take actions
   like triggering a measurement right away or for instance to stop an
   ongoing measurement (e.g. because it is disturbing the network).  The
   need for such a mechanism is likely to depend on the use case of the
   platform.  Probably the ISP use case is more likely to require this
   feature than the regulator/benchmarking use case.  It is probably
   useful then to provide this as an optional feature.

   The main challenge in order to provide this feature is that the MAs
   are likely to be placed behind NATs, so it is not possible for the
   Controller to initiate a communication with the MA unless there is a
   binding in the NAT to forward the packets to the MA.  There are
   several options that can be considered to enable this communication:
   o  The MA can use one of the NAT control protocols, such as PCP or
      UPNP.  If this approach is used, the MA will create a binding in
      the NAT opening a hole.  After that, the MA should inform the
      Controller about which is the IP address and port available for
      communication.  It would be possible to re-use existing protocols
      to forward this information.  The problem with this is that the



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      NAT may not support these protocols or they may not be activated.
      In any case, a solution should try to use them in the case they
      are available.
   o  If it is not possible to use a NAT control protocol, then the MA
      can open a hole in the NAT by establishing a connection to the
      Controller and keeping it open.  This allows the Controller to
      push information to the MA through that connection.  One concern
      with this approach is that the MA is playing the role of the
      client and the Controller is playing the role of the server (the
      MA is initiating the TCP connection), but it would be the
      Controller who would use the PUT method towards the MA reversing
      the roles.  An alternative approach is that the MA has a long
      running GET pending which is answered by the server if the
      measurement Instruction changes (or the server times out, in which
      case the MA restarts the long running GET.  More discussion is
      needed about whether one of these options is acceptable or not.
      In addition, this would imply that the Controller should maintain
      as many open sessions as MAs it is managing, which imposes
      additional burden in the Controller.  There are security
      considerations as well, but these are covered in the Security
      Considerations section below.

6.3.  Report protocol

   The MA after performing the measurements reports the results to a
   collector.  There can be more than one collector within a LMAP
   framework.  Each collector is identified by its FQDN or IP address
   which is retrieved as part of the Agent information from a pre-
   configured controller as previously discussed.  The number of
   Collectors that the MA uploads the results to as well as the schedule
   when it does so is defined in the measurement Instruction previously
   downloaded from the Controller.  The MA themselves are identified by
   a UUID.

   There are two options that can be considered for the MA to upload
   reports to the Collector either to use the PUT method or to use the
   POST method.

   If the PUT method option is used, then the MA need to perform the PUT
   method using an explicit name for the report resource it is
   transferring to the Collector.  The name of the resource is contained
   in the Agent Information previously retrieved by the MA

   The other option is for the MA to use the POST method to upload the
   measurement reports to one or more Collectors.  In this case,, the
   POST message body can contain the identifier of the MA and additional
   information describing the report in addition to the report itself.




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   One argument to consider is that PUT is idempotent.  This means that
   if the network is bad at some point and the MA is not sure whether
   its request made it through, it can send it a second (or nth) time,
   and it is guaranteed that the request will have exactly the same
   effect as sending it for the first time.  POST does not by itself
   guarantee this.  This can be achieved by verifying the report data
   itself, and contrast it with data already stored int he Collector
   database.

6.3.1.  Handling communication failures

   The MA will use a timeout for the communication with the Collector of
   TIMEOUT seconds.  The value of TIMEOUT MUST be configurable via the
   aforementioned Configuration Information retrieval protocol.  The
   default value for the TIMEOUT is 3 seconds.

   If the MA is uploading the report to several Collectors and it
   manages to establish the communication before TIMEOUT seconds with at
   least one of them, but not with one or more of the other Collectors,
   then the MA gives up after TIMEOUT seconds and it MAY issue an alarm.
   The definition of how to do that operation is out of the scope of
   this document.

   If the MA is uploading the report to only one Collector, and it does
   not manages to establish a communication before TIMEOUT seconds, then
   it retry doing an exponential backoff and doing a round robin between
   the different Collectors it has available.

   Similarly, if an HTTP error message (5xx) is received from the
   Collector as a response to the PUT request, the MA will retry doing
   an exponential backoff and doing a round robin between the different
   Collectors it has available.  The 5xx error codes indicate that this
   Collector is currently incapable of performing the requested
   operation.

   In order to support this, the information model must express the
   difference between a report sent to multiple collectors and multiple
   collectors used for fallback.


7.  LMAP Data Model

   This section will contain the data model in json.


8.  Security considerations

   Large Measurement Platforms may result in a security hazard if they



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   are not properly secured.  This is so because they encompass a large
   number of MAs that can be managed and coordinated easily to generate
   traffic and they can potentially be used for generating DDoS attacks
   or other forms of security threats.

   From the perspective of the protocols described in this documents, we
   can identify the following threats:
   o  Hijacking: Probably the worst threat is that an attacker takes
      over the control of one or more MAs.  In this case the attacker
      would be able to instruct the MAs to generate traffic or to
      eavesdrop traffic in their location.  It is then critical that the
      MA is able to strongly authenticate the Controller.  An
      alternative way to achieve this attack is to alter the
      communication between the Controller and the MAs.  In order to
      prevent this form of attack, integrity protection of the
      communication between the Controller and the MAs is required.
   o  Polluting: Another type of attack is that an attacker is able to
      pollute the Collectors database by providing false results.  In
      this case, the attacker would attempt to impersonate one or more
      MAs and upload fake results in the Collector.  In order to prevent
      this, the authentication of the MAs with the Collector is needed.
      An alternative way to achieve this is for an attacker to alter the
      communication between the MA and the Collector.  In order to
      prevent this form of attack, integrity protection of the
      communication between the MA and the Collector is needed.
   o  Disclosure: Another threat is that an attacker may gather
      information about the MAs and their configuration and the
      Measurement schedules.  In order to do that, it would connect to
      the Controller and download the information about one or more MAs.
      This can be prevented by using MA authentication with the
      Controller.  An alternative mean to achieve this would be for the
      attacker to eavesdrop the communication between the MA and the
      Controller.  In order to prevent this, confidentiality in the
      communication between the MA and the Controller is required.
      Similarly, an attacker may wish to obtain measurement result
      information by eavesdropping the communication between the MA and
      the Collector.  In order to prevent this, confidentiality in the
      communication between the MA and the Collector is needed.

   In order to address all the identified threats, the HTTPS protocol
   must be used for LMAP (i.e. using HTTP over TLS).  HTTPS provides
   confidentiality, integrity protection and authentication, satisfying
   all the aforementioned needs.  Ideally, mutual authentication should
   be used.  In any case, server side authentication MUST be used.  In
   order to achieve that, both the Controller and the Collector MUST
   have certificates.  The certificate of the CA used to issue the
   certificates for the Controller and the Collector MUST be pre
   configured in the MAs, so they can properly authenticate them.  As



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   mentioned earlier, ideally, mutual authentication should be used.
   However, this implies that certificates for the MAs are needed.
   Certificate management for a large number of MAs may be expensive and
   cumbersome.  Moreover, the major threats identified are the ones
   related to hijacking of the MAs, which are prevented by
   authenticating the Controller.  MAs authentication is needed to
   prevent Polluting and Disclosure threats, which are less severe.  So,
   in this case, alternative (cheaper) methods for authenticating MAs
   can be considered.  The simplest method would be to simply use the MA
   UUID as a token to retrieve information.  Since the MA UUID is 128
   bit long, it is hard to guess.  It would be also possible to use a
   password and use the HTTP method for authentication.  It is not
   obvious that managing passwords for a large number of MAs is easier
   than managing certificates though.

   An additional security consideration is posed by the mechanism to
   push information from the Controller to the MAs.  If this method is
   used, it would be possible its abuse by an attacker to control the
   MAs.  This threat is prevented by the use of HTTPS.  If HTTPS is used
   in the established connection between the MA and the Controller, the
   only effect that a packet generated by an external attacker to the MA
   or the Controller would be to reset the HTTPS connection, requiring
   the connection to be re-established.

   It is required in this document that both the Controller and that the
   Collector are authenticated using digital certificates.  The current
   specification allows for the MA to have information about the
   certificate of the Certification authority used for generating the
   Controller and Collector certificates while the actual certificates
   are exchanged in band using TLS.  Another (more secure) option is to
   perform certificate pinning i.e. to configure in the MAs the actual
   certificates rather than the certification authority certificate.
   Another measure to increase the security would be to limit the
   domains that the FQDNs of the Controller and/or the Collector (e.g.
   only names in the exmaple.org domain).

   Large scale measurements can have privacy implications, especially in
   some scenarios like mobile devices performing measurements.  In this
   memo we have considered using Group IDs to the MA in order to avoid
   the possibility for the platform to track each individual MA that is
   feeding results.


9.  IANA Considerations

   Registration of the well-known URL





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10.  Acknowledgments


11.  References

11.1.  Normative References

   [RFC2616]  Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,
              Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext
              Transfer Protocol -- HTTP/1.1", RFC 2616, June 1999.

   [RFC4122]  Leach, P., Mealling, M., and R. Salz, "A Universally
              Unique IDentifier (UUID) URN Namespace", RFC 4122,
              July 2005.

   [RFC4627]  Crockford, D., "The application/json Media Type for
              JavaScript Object Notation (JSON)", RFC 4627, July 2006.

   [RFC5785]  Nottingham, M. and E. Hammer-Lahav, "Defining Well-Known
              Uniform Resource Identifiers (URIs)", RFC 5785,
              April 2010.

   [I-D.burbridge-lmap-information-model]
              Burbridge, T., Eardley, P., Bagnulo, M., and J.
              Schoenwaelder, "Information Model for Large-Scale
              Measurement Platforms (LMAP)",
              draft-burbridge-lmap-information-model-00 (work in
              progress), July 2013.

11.2.  Informative References

   [I-D.bagnulo-ippm-new-registry-independent]
              Bagnulo, M., Burbridge, T., Crawford, S., Eardley, P., and
              A. Morton, "A registry for commonly used metrics.
              Independent registries",
              draft-bagnulo-ippm-new-registry-independent-01 (work in
              progress), July 2013.

   [I-D.ietf-lmap-framework]
              Eardley, P., Morton, A., Bagnulo, M., Burbridge, T.,
              Aitken, P., and A. Akhter, "A framework for large-scale
              measurement platforms (LMAP)",
              draft-ietf-lmap-framework-00 (work in progress),
              October 2013.







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Authors' Addresses

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

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


   Trevor Burbridge
   British Telecom
   Adastral Park, Martlesham Heath
   IPswitch
   ENGLAND

   Email: trevor.burbridge@bt.com


   Sam Crawford
   SamKnows

   Email: sam@samknows.com


   Juergen Schoenwaelder
   Jacobs University

   Email: j.schoenwaelder@jacobs-university.de


   Vaibhav Bajpai
   Jacobs University

   Email: v.bajpai@jacobs-university.de













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