Internet DRAFT - draft-morton-ippm-lmap-path
draft-morton-ippm-lmap-path
Network Working Group M. Bagnulo
Internet-Draft UC3M
Intended status: Standards Track T. Burbridge
Expires: August 28, 2013 BT
S. Crawford
SamKnows
P. Eardley
BT
A. Morton
AT&T Labs
February 24, 2013
A Reference Path and Measurement Points for LMAP
draft-morton-ippm-lmap-path-01
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 . . . . . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . 7
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 . . . . . . . . . . . . . . . . . . . . . . . . 10
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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 If it can be shown that a link connecting to a measurement point
has reliably deterministic or negilgible performance, 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 such a link must be reported.
o Many access network architectures have a traffic aggregation point
(e.g., CMTS or DSLAM) between mp100 and mp150. We designate this
point mp120, but it won't currently fit in the figure.
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 In the case that a private address space is used in an access
architecture, then mp100 may need to use the same address space as
its remote measurement point counterpart, so that a test between
these points produces a useful assessment of network performance.
Tests between mp000 and mp100 could use private address space, and
when the egress side of a CGN is at mp150, then the private
address side of the CGN could be designated mp149 for tests with
mp100.
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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.
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--------|-------|BRAS-|------|
|----Access Network--|
GRA = Globally Routable Address, GW = Gateway
Consider next the case where:
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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:
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-|------|
|---Access Network--|
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
Thanks to Matt Mathis for review and comments.
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.
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[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.
[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.
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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
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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