Network Working Group                                         M. Bagnulo
Internet-Draft                                                      UC3M
Intended status: Informational                              T. Burbridge
Expires: November 29, December 21, 2014                                            BT
                                                             S. Crawford
                                                                SamKnows
                                                              P. Eardley
                                                                      BT
                                                               A. Morton
                                                               AT&T Labs
                                                            May 28,
                                                           June 19, 2014

            A Reference Path and Measurement Points for LMAP
                      draft-ietf-ippm-lmap-path-03
                      draft-ietf-ippm-lmap-path-04

Abstract

   This document defines a reference path for Large-scale Measurement of
   Broadband Access Performance (LMAP) and measurement points for
   commonly used performance metrics.  The methods for measurement point
   location may be applicable to similar measurement projects using the
   extensions described here.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on November 29, December 21, 2014.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Purpose and Scope . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Terms and Definitions . . . . . . . . . . . . . . . . . . . .   3   4
     3.1.  Reference Path  . . . . . . . . . . . . . . . . . . . . .   3   4
     3.2.  Subscriber  . . . . . . . . . . . . . . . . . . . . . . .   4
     3.3.  Dedicated Component (Links or Nodes)  . . . . . . . . . .   4
     3.4.  Shared Component (Links or Nodes) . . . . . . . . . . . .   4
     3.5.  Resource Transition Point . . . . . . . . . . . . . . . .   4
     3.6.  Managed and Un-Managed Sub-paths  . . . . . . . . . . . .   4   5
   4.  Reference Path  . . . . . . . . . . . . . . . . . . . . . . .   5
   5.  Measurement Points  . . . . . . . . . . . . . . . . . . . . .   6
   6.  Translation Between Reference Path and Various Technologies .  10
   7.  Example Resource Transition . . . . . . . . . . . . . . . . .  11
   8.  Security considerations . . . . . . . . . . . . . . . . . . .  12
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  13
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  13
     11.2.  Informative References . . . . . . . . . . . . . . . . .  13
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

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 (section 5 of
   [RFC2330]).  There are a limited number of additional terms needing
   definition here, and they will be defined in this memo.

   The reference path is usually needed when attempting to communicate
   precisely about the components that comprise the path, often 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,
   section 4 of [RFC5835] (which may also figure in the LMAP work
   effort).  Section 4.1 of [RFC5835] defines the term "measurement
   point".

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

   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 meta-data 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",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   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 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 as well.

   The connection between the reference path and specific network
   technologies (with differing underlying architectures) is within the
   scope of this method, 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 adequately described in terms of
   scope or coverage.  This should serve many measurement uses,
   including:

   diagnostic

   diagnostic:  where the same metric may be measured over many
      different path scopes

   comparison

   comparison:  where the same metric may be measured on equivalent
      portions of different network infrastructures

3.  Terms and Definitions

   This section defines key terms and concepts for the purposes of this
   memo.

3.1.  Reference Path

   A reference path is a serial combination of routers, switches, links,
   radios, and processing elements that comprise all the network
   elements traversed by each packet between the source and destination
   hosts.  The reference path is intended to be equally applicable to
   all networking technologies, therefore the components are generically
   defined, but their functions should have a clear counterpart or be
   obviously omitted in any network technology.

3.2.  Subscriber

   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 un-subscribe services, and to register a user or a list
   of users authorized to enjoy these services.  [Q1741] Both the
   subscriber and service provider are allowed to set the limits
   relative to the use that associated users make of subscribed
   services.

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

   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.  Managed and Un-Managed Sub-paths

   Service providers are responsible for the portion of the path they
   manage.  However, most paths involve a sub-path which 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 are designated as un-managed sub-paths.
   The Service demarcation point always divides managed and un-managed
   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

   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 (and ownership
      may shift to the service provider), and this should be noted as
      part of the path description.

   o  Service Demarcation point - This is the point where service
      managed by the serivce 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., LTE UE).  Ownership may not 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 a third-party
      will certify standards compliance.

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

   o  GRA GW - 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 GW.

   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 Service Demarc. and the Intra IP Access points
   must use the same address space and be separated by the shared and
   dedicated access link infrastructure, such that a test between these
   points produces a useful assessment of access performance.

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
   which 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 point.

   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 1

   When communicating the results of measurements using the measurement
   point designations described here, the measuring organization SHOULD
   supply a diagram similar to Figure 1 (and the technology-specific
   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.  Organizations with
   similar technologies and architectures are encouraged to coordinate
   on local numbering and diagrams, when possible.

   The measurement point numbering system, mpXnn, has two independent
   parts:

   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
           Demarc.).

       C.  In most networks, measurement point numbers SHOULD
           monotonically increase from point nearest the Subscriber's
           device to the opposite network boundary on the path (see
           below).

       D.  When a Detination host is part of the path, 00 SHOULD be used
           for a measurement point at the Destination host and at the
           the Destination's Service Demarcation point.  Measurement
           point numbers SHOULD monotonically increase from 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 Demarcs.

       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
           DSLAM within a network.

       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).  Sub-networks or domains
           within a network are useful locations for measurement points.

   In order to define the measurement points and the scope of
   measurements without ambiguity, the operator of the measurement
   system SHOULD indicate on a diagram (similar to those in this
   document): the reference path, the numbers (mpXnn) of the measurement
   points, and the definition of any measurement point other than 00 and
   90 (with sufficient detail to clearly define its location).

   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.

   Notes:

   o  Some use the terminology "on-net" and "off-net" 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 (To Be Specified Elsewhere).  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, then 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, then 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 first transit network is shown, with point
      mp200 and the last transit network GW with mpX90.

6.  Translation Between Reference Path and Various Technologies

   This section and those that follow are intended to provide a more
   exact mapping between particular network technologies and the
   reference path.

   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

   |_____________UE______________|___RAN+Core____|___GGSN__|
   |_____Un-managed sub-path_____|____Managed sub-path_____|

    GRA = Globally Routable Address, GW = Gateway, UE = User Equipment,
       RAN = Radio Access Network, GGSN = Gateway GPRS Support Node.

   We next provide a few examples an example of DSL access.  Consider first the case where:

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

   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 though the WiFi
      access.

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

   This case would map into the defined reference measurement points as
   follows:

   Subsc. -- Private -- Private -- Service-- Intra IP -- GRA -- Transit
   device     Net #1     Net #2    Demarc.    Access     GW     GRA GW
   mp000                            mp100      mp150    mp190    mp200
   |--UE--|------------CPE/NAT--------|------|-BRAS-|------|
                                      |------DSL Network---|
   |_______Un-managed sub-path________|__Managed sub-path__|

      GRA = Globally Routable Address, GW = Gateway, BRAS = Broadband
                            Remote Acess Server

   Consider next the another access network case where:

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

   o  There is a Carrier Grade NAT (CGN) located deep into 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 though the WiFi
      access.

   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
   follows:

   Subsc. -- Private ------------- Service-- Intra IP -- GRA -- Transit
   device     Net #1               Demarc.    Access     GW     GRA GW
   mp000                            mp100      mp150    mp190    mp200
   |--UE--|------------CPE/NAT--------|------|-CGN-|------|
                                      |-----DSL
                                      |--Access Network---|
   |_______Un-managed sub-path________|_Managed sub-path__|

               GRA = Globally Routable Address, GW = Gateway

7.  Example Resource Transition

   This section gives an example of Shared and Dedicated portions with
   the reference path.  This example shows two Resource Transition
   Points.

   Consider the case where:

   o  The CPE is 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 though the WiFi access.

   o  The Wi-Fi subnetwork (Private Net#1) shares unlicensed radio
      channel resources with other W-Fi 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 Carrier Grade NAT (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
   world.

   This case would map into the defined reference measurement points as
   follows:

   Subsc. -- Private -- Private -- Access -- Intra IP -- GRA -- Transit
   device     Net #1     Net #2    Demarc.    Access     GW     GRA GW
   mp000                            mp100      mp150    mp190    mp200
   |--UE--|------------CPE/NAT--------|------|-CGN-|------|
          |   Wi-Fi  |  1000Base-T    |-----DSL    |--Access Network---|

          |-Shared--|RT|------Dedicated------| RT  |-----Shared------...
   |_______Un-managed sub-path________|_Managed sub-path__|

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

8.  Security considerations

   Specification of a Reference Path and identification of measurement
   points on the path represent agreements among interested parties, and
   they present no threat to the readers of this memo or to the Internet
   itself.

   When considering privacy of those involved in measurement or those
   whose traffic is measured, there is 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 [I-D.ietf-lmap-framework],
   which covers active and passive measurement techniques and supporting
   material on measurement context.

9.  IANA Considerations

   This memo makes no requests for IANA consideration.

10.  Acknowledgements

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

11.  References

11.1.  Normative References

   [RFC2330]  Paxson, V., Almes, G., Mahdavi, J., and M. Mathis,
              "Framework for IP Performance Metrics", RFC 2330, May
              1998.

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

   [RFC3432]  Raisanen, V., Grotefeld, G., and A. Morton, "Network
              performance measurement with periodic streams", RFC 3432,
              November 2002.

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

11.2.  Informative References

   [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-05
              framework-06 (work in progress), May June 2014.

   [SK]       Crawford, Sam., "Test Methodology White Paper", SamKnows
              Whitebox Briefing Note
              http://www.samknows.com/broadband/index.php, July 2011.

   [Q1741]    Q.1741.7, , "IMT-2000 references to Release 9 of GSM-
              evolved UMTS core network",
              http://www.itu.int/rec/T-REC-Q.1741.7/en, November 2011.

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
   BT
   Adastral Park, Martlesham Heath
   Ipswich
   ENGLAND

   Email: trevor.burbridge@bt.com

   Sam Crawford
   SamKnows

   Email: sam@samknows.com

   Phil Eardley
   BT
   Adastral Park, Martlesham Heath
   Ipswich
   ENGLAND

   Email: philip.eardley@bt.com

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

   Email: acmorton@att.com