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.

Status of This Memo

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Table of Contents

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 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.

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.

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:

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.

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:

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:

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:

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, DOI 10.17487/RFC2330, May 1998.
[RFC3432] Raisanen, V., Grotefeld, G. and A. Morton, "Network performance measurement with periodic streams", RFC 3432, DOI 10.17487/RFC3432, November 2002.
[RFC2681] Almes, G., Kalidindi, S. and M. Zekauskas, "A Round-trip Delay Metric for IPPM", RFC 2681, DOI 10.17487/RFC2681, September 1999.
[RFC6673] Morton, A., "Round-Trip Packet Loss Metrics", RFC 6673, DOI 10.17487/RFC6673, August 2012.
[RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, DOI 10.17487/RFC1035, November 1987.
[RFC5905] Mills, D., Martin, J., Burbank, J. and W. Kasch, "Network Time Protocol Version 4: Protocol and Algorithms Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010.
[RFC2679] Almes, G., Kalidindi, S. and M. Zekauskas, "A One-way Delay Metric for IPPM", RFC 2679, DOI 10.17487/RFC2679, September 1999.
[RFC2680] Almes, G., Kalidindi, S. and M. Zekauskas, "A One-way Packet Loss Metric for IPPM", RFC 2680, DOI 10.17487/RFC2680, September 1999.
[RFC3393] Demichelis, C. and P. Chimento, "IP Packet Delay Variation Metric for IP Performance Metrics (IPPM)", RFC 3393, DOI 10.17487/RFC3393, November 2002.
[RFC5481] Morton, A. and B. Claise, "Packet Delay Variation Applicability Statement", RFC 5481, DOI 10.17487/RFC5481, March 2009.
[RFC5835] Morton, A. and S. Van den Berghe, "Framework for Metric Composition", RFC 5835, DOI 10.17487/RFC5835, April 2010.

10.2. Informative References

[RFC4148] Stephan, E., "IP Performance Metrics (IPPM) Metrics Registry", BCP 108, RFC 4148, DOI 10.17487/RFC4148, August 2005.
[RFC6248] Morton, A., "RFC 4148 and the IP Performance Metrics (IPPM) Registry of Metrics Are Obsolete", RFC 6248, DOI 10.17487/RFC6248, 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
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