A Reference Path and Measurement Points for LMAP
draft-morton-ippm-lmap-path-00

Network Working Group                                         M. Bagnulo
Internet-Draft                                                      UC3M
Intended status: Standards Track                            T. Burbridge
Expires: August 4, 2013                                               BT
                                                             S. Crawford
                                                                SamKnows
                                                              P. Eardley
                                                                      BT
                                                               A. Morton
                                                               AT&T Labs
                                                        January 31, 2013

            A Reference Path and Measurement Points for LMAP
                     draft-morton-ippm-lmap-path-00

Abstract

   This document defines a reference path for Large-scale Measurement of
   Broadband Access Performance (LMAP) and measurement points for
   commonly used performance metrics.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . . . 3
   2.  Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . . 3
   3.  Terms and Definitions . . . . . . . . . . . . . . . . . . . . . 4
     3.1.  Reference Path  . . . . . . . . . . . . . . . . . . . . . . 4
   4.  Reference Path  . . . . . . . . . . . . . . . . . . . . . . . . 4
   5.  Measurement Points  . . . . . . . . . . . . . . . . . . . . . . 5
   6.  Translation Between Ref. Path and Tech. X . . . . . . . . . . . 6
   7.  Security considerations . . . . . . . . . . . . . . . . . . . . 8
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . . . 8
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . . . 8
     10.1. Normative References  . . . . . . . . . . . . . . . . . . . 8
     10.2. Informative References  . . . . . . . . . . . . . . . . . . 9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . . . 9

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1.  Introduction

   This document defines a reference path for Large-scale Measurement of
   Broadband Access Performance (LMAP).  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 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 metadata to describe measurement
   results.  Measurements conducted over different path scopes are not a
   valid basis for performance comparisons.

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 without ambiguity.

   The bridge between the reference path and specific network
   technologies (with differing underlying architectures) is within the
   scope of this effort.  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 this regard.
   This should serve many measurement uses, including diagnostic (where
   the same metric may be measured over many different path scopes) and

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   comparative (where the same metric may be measured on different
   network infrastructures).

3.  Terms and Definitions

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.

4.  Reference Path

   This section defines a reference path for Internet Access.

    Subsc. -- Private -- Private -- Access -- 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 Access Service Subscriber.  In some
      configurations, one or more private networks and the device that
      provides the Access 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  Access (Service) Demarcation point - this varies by technology but
      is usually defined as the Ethernet interface on a residential
      gateway or modem where the scope of access 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

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      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 access network, or a third-party will certify standards
      compliance.
   o  Intra IP Access - This is the first point in the access
      architecture beyond the Access 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 Access Service Demarc., in principle.  Only one
      Intra IP Access point is shown, but they can be identified in any
      access or transit network.
   o  GRA GW - the point of interconnection between the access
      administrative domain and the rest of the Internet, where routing
      will depend on the GRAs in the IP header.
   o  Transit GRA GW - Networks that intervene between the Subscriber's
      Access network and the Destination Host's network are designated
      "transit" and involve two 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 Access 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, deterministic errors that can be quantified are ideal.

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

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    Subsc. -- Private -- Private -- Access -- 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

   The numbering for measurement points (mpNNN) allows for considerable
   local use of unallocated numbers.

   Notes:

   o  Some use the terminology "on-net" and "off-net" when referring to
      Internet Service Provider (ISP) measurement coverage.  With
      respect to the reference path, tests between mp100 and mp190 are
      "on-net".
   o  Widely deployed broadband 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 used at all measurement points must be
      indicated, especially the interface standard and configured speed.
   o  A Carrier Grade NAT (CGN) deployed in the Subscriber's access
      network would be positioned between mp100 and mp190, and the
      egress side of the CGN will typically be designated mp150.
   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.

6.  Translation Between Ref. Path and Tech. X

   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.

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

    |_____________UE______________|___RAN+Core____|___GGSN__|

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

   We next provide a few examples of DSL access.  Consider first the
   case where:
   o  The Customer Premises Equipment (CPE) is 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 -- Access -- Intra IP -- GRA -- Transit
    device     Net #1     Net #2    Demarc.    Access     GW     GRA GW
    mp000                            mp100      mp150    mp190    mp200
    |--UE--|------------CPE/NAT---------------------|----Access--|
                                                         Network

               GRA = Globally Routable Address, GW = Gateway

   Consider next the 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 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 is becoming a fairly common configuration in some parts of
   the world.

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

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    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--|

               GRA = Globally Routable Address, GW = Gateway

7.  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.

8.  IANA Considerations

   TBD

9.  Acknowledgements

   TBD

10.  References

10.1.  Normative References

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

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

   [RFC2681]  Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip
              Delay Metric for IPPM", RFC 2681, September 1999.

   [RFC6673]  Morton, A., "Round-Trip Packet Loss Metrics", RFC 6673,
              August 2012.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

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   [RFC5905]  Mills, D., Martin, J., Burbank, J., and W. Kasch, "Network
              Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, June 2010.

   [RFC2679]  Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
              Delay Metric for IPPM", RFC 2679, September 1999.

   [RFC2680]  Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way
              Packet Loss Metric for IPPM", RFC 2680, September 1999.

   [RFC3393]  Demichelis, C. and P. Chimento, "IP Packet Delay Variation
              Metric for IP Performance Metrics (IPPM)", RFC 3393,
              November 2002.

   [RFC5481]  Morton, A. and B. Claise, "Packet Delay Variation
              Applicability Statement", RFC 5481, March 2009.

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

10.2.  Informative References

   [RFC4148]  Stephan, E., "IP Performance Metrics (IPPM) Metrics
              Registry", BCP 108, RFC 4148, August 2005.

   [RFC6248]  Morton, A., "RFC 4148 and the IP Performance Metrics
              (IPPM) Registry of Metrics Are Obsolete", RFC 6248,
              April 2011.

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

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   Trevor Burbridge
   British Telecom
   Adastral Park, Martlesham Heath
   IPswitch
   ENGLAND

   Email: trevor.burbridge@bt.com

   Sam Crawford
   SamKnows

   Email: sam@samknows.com

   Phil Eardley
   British Telecom
   Adastral Park, Martlesham Heath
   IPswitch
   ENGLAND

   Email: philip.eardley@bt.com

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

   Email: acmorton@att.com

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