One document matched: draft-ietf-ippm-lmap-path-00.xml
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<rfc category="std" docName="draft-ietf-ippm-lmap-path-00" ipr="trust200902"
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<front>
<title abbrev="LMAP Reference Path">A Reference Path and Measurement
Points for LMAP</title>
<author fullname="Marcelo Bagnulo" initials="M." surname="Bagnulo">
<organization abbrev="UC3M">Universidad Carlos III de
Madrid</organization>
<address>
<postal>
<street>Av. Universidad 30</street>
<city>Leganes</city>
<region>Madrid</region>
<code>28911</code>
<country>SPAIN</country>
</postal>
<phone>34 91 6249500</phone>
<email>marcelo@it.uc3m.es</email>
<uri>http://www.it.uc3m.es</uri>
</address>
</author>
<author fullname="Trevor Burbridge" initials="T." surname="Burbridge">
<organization abbrev="BT">British Telecom</organization>
<address>
<postal>
<street>Adastral Park, Martlesham Heath</street>
<city>IPswitch</city>
<country>ENGLAND</country>
</postal>
<email>trevor.burbridge@bt.com</email>
</address>
</author>
<author fullname="Sam Crawford" initials="S." surname="Crawford">
<organization abbrev="SamKnows">SamKnows</organization>
<address>
<email>sam@samknows.com</email>
</address>
</author>
<author fullname="Phil Eardley" initials="P." surname="Eardley">
<organization abbrev="BT">British Telecom</organization>
<address>
<postal>
<street>Adastral Park, Martlesham Heath</street>
<city>IPswitch</city>
<country>ENGLAND</country>
</postal>
<email>philip.eardley@bt.com</email>
</address>
</author>
<author fullname="Al Morton" initials="A." surname="Morton">
<organization abbrev="AT&T Labs">AT&T Labs</organization>
<address>
<postal>
<street>200 Laurel Avenue South</street>
<city>Middletown, NJ</city>
<country>USA</country>
</postal>
<email>acmorton@att.com</email>
</address>
</author>
<date day="8" month="July" year="2013"/>
<abstract>
<t>This document defines a reference path for Large-scale Measurement of
Broadband Access Performance (LMAP) and measurement points for commonly
used performance metrics.</t>
</abstract>
</front>
<middle>
<section title="Introduction">
<t>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 <xref target="RFC2330"/>). There are a
limited number of additional terms needing definition here, and they
will be defined in this memo.</t>
<t>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 <xref
target="RFC3432"/>, and as part of the updated framework for composition
and aggregation, section 4 of <xref target="RFC5835"/> (which may also
figure in the LMAP work effort). Section 4.1 of <xref target="RFC5835"/>
defines the term "measurement point".</t>
<t>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?</t>
<t>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.</t>
</section>
<section title="Purpose and Scope">
<t>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.</t>
<t>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.</t>
<t>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).</t>
</section>
<section title="Terms and Definitions">
<t>This section defines key terms and concepts for the purposes of this
memo.</t>
<section title="Reference Path">
<t>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.</t>
</section>
<section title="Subscriber">
<t>An entity possessing one or more hosts participating in an Internet
access service.</t>
</section>
<section title="Dedicated Component (Links or Nodes)">
<t>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.</t>
</section>
<section title="Shared Component (Links or Nodes) ">
<t>A component on the Reference Path is designated a Shared component
when the traffic associated with multiple Subscribers is served by
common resources.</t>
</section>
<section title="Resource Transition Point">
<t>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.</t>
</section>
</section>
<section title="Reference Path">
<t>This section defines a reference path for Internet Access.</t>
<t><figure align="center">
<artwork><![CDATA[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
]]></artwork>
<postamble>GRA = Globally Routable Address, GW = Gateway</postamble>
</figure></t>
<t>The following are descriptions of reference path components that may
not be clear from their name alone.</t>
<t><list style="symbols">
<t>Subsc. (Subscriber) device - This is a host that normally
originates and terminates communications conducted over the IP
packet transfer service.</t>
<t>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.</t>
<t>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 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.</t>
<t>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.</t>
<t>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.</t>
<t>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.</t>
</list>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.</t>
<t>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.</t>
</section>
<section title="Measurement Points">
<t>A key aspect of measurement points, beyond the definition in section
4.1 of <xref target="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.</t>
<t>In general, measurement points cannot always be located exactly where
desired. However, the definition in <xref target="RFC5835"/> and the
discussion in section 5.1 of <xref target="RFC3432"/> indicate that
allowances can be made: for example, deterministic errors that can be
quantified are ideal.</t>
<t>The Figure below illustrates the assignment of measurement points to
selected components of the reference path.</t>
<t><figure align="center">
<artwork><![CDATA[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
]]></artwork>
<postamble>GRA = Globally Routable Address, GW = Gateway</postamble>
</figure></t>
<t>The numbering for measurement points (mpNNN) allows for considerable
local use of unallocated numbers.</t>
<t>Notes:</t>
<t><list style="symbols">
<t>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".</t>
<t>Widely deployed broadband access measurements have used
pass-through devices<xref target="SK"/> (at the subscriber's
location) directly connected to the service demarcation point: this
would be located at mp100.</t>
<t>The networking technology used at all measurement points must be
indicated, especially the interface standard and configured
speed.</t>
<t>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.</t>
<t>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.</t>
<t>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.</t>
<t>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.</t>
<t>Measurement points at Transit GRA GWs are numbered mpX00 and
mpX90, where X is the lowest positive integer not already used in
the path.</t>
</list></t>
</section>
<section title="Translation Between Ref. Path and Tech. X ">
<t>This section and those that follow are intended to provide a more
exact mapping between particular network technologies and the reference
path.</t>
<t>We provide an example for 3G Cellular access below.</t>
<figure align="center">
<artwork><![CDATA[Subscriber -- Private -- Access Srvc ----------- GRA --- Transit ...
device Net #1 Demarc. GW GRA GW
mp000 mp100 mp190 mp200
|_____________UE______________|___RAN+Core____|___GGSN__|
]]></artwork>
<postamble>GRA = Globally Routable Address, GW = Gateway, UE = User
Equipment, RAN = Radio Access Network, GGSN = Gateway GPRS Support
Node.</postamble>
</figure>
<t/>
<t>We next provide a few examples of DSL access. Consider first the case
where: <list style="symbols">
<t>The Customer Premises Equipment (CPE) is a NAT device that is
configured with a public IP address.</t>
<t>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.</t>
</list> We believe this is a fairly common configuration in some parts
of the world and fairly simple as well.</t>
<t>This case would map into the defined reference measurement points as
follows:</t>
<t><figure align="center">
<artwork><![CDATA[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--|
]]></artwork>
<postamble>GRA = Globally Routable Address, GW = Gateway</postamble>
</figure></t>
<t>Consider next the case where: <list style="symbols">
<t>The Customer Premises Equipment (CPE) is a NAT device that is
configured with a private IP address.</t>
<t>There is a Carrier Grade NAT (CGN) located deep into the Access
ISP network.</t>
<t>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.</t>
</list> We believe is becoming a fairly common configuration in some
parts of the world.</t>
<t>This case would map into the defined reference measurement points as
follows:</t>
<t><figure align="center">
<artwork><![CDATA[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--|
]]></artwork>
<postamble>GRA = Globally Routable Address, GW = Gateway</postamble>
</figure></t>
</section>
<section title="Security considerations">
<t>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.</t>
</section>
<section title="IANA Considerations">
<t>TBD</t>
</section>
<section title="Acknowledgements">
<t>Thanks to Matt Mathis for review and comments.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include='reference.RFC.2330'?>
<?rfc include='reference.RFC.3432'?>
<?rfc include='reference.RFC.2681'?>
<?rfc include='reference.RFC.6673'?>
<?rfc include='reference.RFC.1035'?>
<?rfc include='reference.RFC.5905'?>
<?rfc include='reference.RFC.2679'?>
<?rfc include='reference.RFC.2680'?>
<?rfc include='reference.RFC.3393'?>
<?rfc include='reference.RFC.5481'?>
<?rfc include='reference.RFC.5835'?>
</references>
<references title="Informative References">
<?rfc include='reference.RFC.4148'?>
<?rfc include='reference.RFC.6248'?>
<reference anchor="SK">
<front>
<title>Test Methodology White Paper</title>
<author fullname="S, Crawford" initials="Sam" surname="Crawford">
<!---->
<organization abbrev="Boeing">Boeing Computer
Services</organization>
</author>
<date month="July" year="2011"/>
</front>
<seriesInfo name="SamKnows Whitebox Briefing Note"
value="http://www.samknows.com/broadband/index.php"/>
</reference>
</references>
</back>
</rfc>
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