Network Working Group M. Bagnulo
Internet-Draft UC3M
Intended status: Informational T. Burbridge
Expires: February 6, 2015 BT
S. Crawford
SamKnows
P. Eardley
BT
A. Morton
AT&T Labs
August 5, 2014
A Reference Path and Measurement Points for LMAP
draft-ietf-ippm-lmap-path-05
Abstract
This document defines a reference path for Large-scale Measurement of
Broadband Access Performance (LMAP) and measurement points for
commonly used performance metrics. Other similar measurement
projects may also be able to use the extensions described here for
measurement point location.
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 February 6, 2015.
Copyright Notice
Copyright (c) 2014 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
Bagnulo, et al. Expires February 6, 2015 [Page 1]
Internet-Draft LMAP Reference Path August 2014
(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
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 . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Purpose and Scope . . . . . . . . . . . . . . . . . . . . . . 3
3. Terms and Definitions . . . . . . . . . . . . . . . . . . . . 4
3.1. Reference Path . . . . . . . . . . . . . . . . . . . . . 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 . . . . . . . . . . . . . . . . 5
3.6. Managed and Un-Managed Sub-paths . . . . . . . . . . . . 5
4. Reference Path . . . . . . . . . . . . . . . . . . . . . . . 5
5. Measurement Points . . . . . . . . . . . . . . . . . . . . . 6
6. Translation Between Reference Path and Various Technologies . 10
7. Example Resource Transition . . . . . . . . . . . . . . . . . 12
8. Security considerations . . . . . . . . . . . . . . . . . . . 13
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 13
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 13
11.1. Normative References . . . . . . . . . . . . . . . . . . 13
11.2. Informative References . . . . . . . . . . . . . . . . . 14
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 14
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,
Bagnulo, et al. Expires February 6, 2015 [Page 2]
Internet-Draft LMAP Reference Path August 2014
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: where the same metric would be measured on different
sub-paths bounded by measurement points (see Section 4.10
of[RFC5835]), for example to isolate the sub-path contributing the
majority of impairment levels observed on a path.
Bagnulo, et al. Expires February 6, 2015 [Page 3]
Internet-Draft LMAP Reference Path August 2014
comparison: where the same metric may be measured on equivalent
portions of different network infrastructures, for example to
compare the performance of wired and wireless home network
technologies.
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 to 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.
Bagnulo, et al. Expires February 6, 2015 [Page 4]
Internet-Draft LMAP Reference Path August 2014
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 service 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
Bagnulo, et al. Expires February 6, 2015 [Page 5]
Internet-Draft LMAP Reference Path August 2014
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 does not necessarily
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 Intra IP Access points must use the same
address space as the Service Demarcation point, and the Intra IP
Access points must be selected such that a test between these points
produces a useful assessment of access performance (e.g., includes
both shared and dedicated access link infrastructure).
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.
Bagnulo, et al. Expires February 6, 2015 [Page 6]
Internet-Draft LMAP Reference Path August 2014
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
Each measurement point on a specific reference path MUST be assigned
a unique number. To facilitate interpretation of the results, the
measuring organisation (and whoever it shares results with) MUST have
an unambiguous understanding of what path or point was measured. In
order to achieve this, a set of numbering recommendations follow.
When communicating the results of measurements, the measuring
organization SHOULD supply a diagram similar to Figure 1 (with the
technology-specific information in 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.
Ideally, the consumer of measurement results would know the location
of a measurement point on the reference path from the measurement
point number alone, and the recommendations below provide a way to
accomplish this goal. Although the initial numbering may be fully
compliant with this system, network growth, consolidation, and re-
arrangement, or circumstances such as ownership changes, could cause
gaps in network numbers or non-monotonic measurement point number
assignments along the path over time. These are examples of
reasonable causes for numbering deviations which must be identified
on the reference path diagram, as required above.
Bagnulo, et al. Expires February 6, 2015 [Page 7]
Internet-Draft LMAP Reference Path August 2014
Whilst the numbering of a measurement point is in the context of a
particular path, for simplicity the measuring organisation SHOULD use
the same numbering for a device (playing the same role) on all the
measurement paths through it. Similarly, whilst the measurement
point numbering is in the context of a particular measuring
organisation, organizations with similar technologies and
architectures are encouraged to coordinate on local numbering and
diagrams.
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 Destination host is part of the path, 00 SHOULD be
used for a measurement point at the Destination host and at
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
Bagnulo, et al. Expires February 6, 2015 [Page 8]
Internet-Draft LMAP Reference Path August 2014
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.
When supplying a diagram of the reference path and measurement
points, the operator of the measurement system MUST indicate: the
reference path, the numbers (mpXnn) of the measurement points, and
the technology-specific definition of any measurement point other
than X00 and X90 with sufficient detail to clearly define its
location (similar to the technology-specific examples in Section 6 of
this document).
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).
Bagnulo, et al. Expires February 6, 2015 [Page 9]
Internet-Draft LMAP Reference Path August 2014
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 example
mappings between particular network technologies and the reference
path.
We provide an example for 3G Cellular access below.
Bagnulo, et al. Expires February 6, 2015 [Page 10]
Internet-Draft LMAP Reference Path August 2014
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 an example of DSL access. Consider 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 Access Server
Consider next 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 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
Bagnulo, et al. Expires February 6, 2015 [Page 11]
Internet-Draft LMAP Reference Path August 2014
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-|------|
|--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.
Bagnulo, et al. Expires February 6, 2015 [Page 12]
Internet-Draft LMAP Reference Path August 2014
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 |--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.
Bagnulo, et al. Expires February 6, 2015 [Page 13]
Internet-Draft LMAP Reference Path August 2014
[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-07 (work in progress), 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
Bagnulo, et al. Expires February 6, 2015 [Page 14]
Internet-Draft LMAP Reference Path August 2014
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
Bagnulo, et al. Expires February 6, 2015 [Page 15]