One document matched: draft-ietf-mpls-tp-oam-requirements-02.xml
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<rfc category="std" docName="draft-ietf-mpls-tp-oam-requirements-02"
ipr="trust200902">
<front>
<title abbrev="OAM Requirements for MPLS-TP">Requirements for OAM in MPLS
Transport Networks</title>
<author fullname="Martin Vigoureux" initials="M." role="editor"
surname="Vigoureux">
<organization>Alcatel-Lucent</organization>
<address>
<postal>
<street>Route de Villejust</street>
<city>Nozay</city>
<region></region>
<code>91620</code>
<country>France</country>
</postal>
<email>martin.vigoureux@alcatel-lucent.com</email>
</address>
</author>
<author fullname="David Ward" initials="D." role="editor" surname="Ward">
<organization>Cisco Systems, Inc.</organization>
<address>
<postal>
<street>170 W. Tasman Dr.</street>
<city>San Jose</city>
<region>CA</region>
<code>95134</code>
<country>USA</country>
</postal>
<email>dward@cisco.com</email>
</address>
</author>
<author fullname="Malcolm Betts" initials="M." role="editor"
surname="Betts">
<organization>Huawei</organization>
<address>
<postal>
<street></street>
<city></city>
<region></region>
<code></code>
<country></country>
</postal>
<email>malcolm.betts@huawei.com</email>
</address>
</author>
<date day="28" month="June" year="2009" />
<area>Routing</area>
<workgroup>MPLS Working Group</workgroup>
<keyword>MPLS-TP</keyword>
<keyword>OAM</keyword>
<abstract>
<t>This document lists the requirements for the Operations,
Administration and Maintenance functionality of MPLS Transport Profile.
These requirements apply to pseudowires, Label Switched Paths, and
Sections. Architectural and functional requirements are covered in this
document.</t>
</abstract>
<?rfc needLines="0"?>
</front>
<middle>
<section title="Introduction">
<t>In the context of MPLS Transport Profile (MPLS-TP, see <xref
target="I-D.ietf-mpls-tp-framework"></xref> and <xref
target="I-D.ietf-mpls-tp-requirements"></xref>), the rationales for
Operations, Administration and Maintenance (OAM) mechanisms are twofold
as they can serve:</t>
<t><list style="symbols">
<t>as a network-oriented mechanism (used by a transport network
operator) to monitor his network infrastructure and to implement
internal mechanisms in order to enhance the general behaviour and
the level of performance of his network (e.g., protection mechanism
in case of node or link failure). For example, fault localization is
typically associated with this use case.</t>
<t>as a service-oriented mechanism (used by a transport service
provider) to monitor services offered to end customers in order to
be able to react rapidly in case of a problem and to be able to
verify some of the Service Level Agreements (SLAs) parameters (e.g.,
using performance monitoring) negotiated with the end customers.
Note that a transport service could be provided over several
networks or administrative domains that may not all be owned and
managed by the same transport service provider.</t>
</list></t>
<t>More generally, OAM is an important and fundamental functionality in
transport networks as it contributes to:</t>
<t><list style="symbols">
<t>the reduction of operational complexity and costs, by allowing
for efficient and automatic detection, localisation, handling, and
diagnosis of defects, and by minimizing service interruptions and
operational repair times.</t>
<t>the enhancement of network availability, by ensuring that
defects, for example resulting in misdirected customer traffic, and
faults, are detected, diagnosed and dealt with before a customer
reports the problem.</t>
<t>meet service and performance objectives, as the OAM functionality
allows for SLA verification in a multi-maintenance domain
environment and allows for the determination of service degradation
due, for example, to packet delay or packet loss.</t>
</list></t>
<t>This document lists the requirements for the OAM functionality of
MPLS-TP. These requirements apply to pseudowires (PWs), Label Switched
Paths (LSPs), and Sections.</t>
<t>These requirements are derived from the set of requirements specified
by ITU-T and published in the ITU-T Supplement Y.Sup4 <xref
target="Y.Sup4"></xref>.</t>
<t>By covering transport specificities, these requirements complement
those identified in RFC 4377 <xref target="RFC4377"></xref>.</t>
<t>Note that the OAM functionalities identified in this document may be
used for fault management, performance monitoring and/or protection
switching applications. For example, connectivity verification can be
used for fault management application by detecting failure conditions,
but may also be used for performance monitoring application through its
contribution to the evaluation of performance metrics (e.g.,
unavailability time). Nevertheless, it is outside the scope of this
document to specify which functionality should be used for which
application.</t>
<section title="Requirements Language and Terminology">
<t>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 <xref
target="RFC2119"></xref>.</t>
<t>In this document we refer to the inability of a function to perform
a required action, as a fault. This does not include an inability due
to preventive maintenance, lack of external resources, or planned
actions. See also ITU-T G.806 <xref target="G.806"></xref>.</t>
<t>In this document we refer to the situation in which the density of
anomalies has reached a level where the ability to perform a required
function has been interrupted, as a defect. See also ITU-T G.806 <xref
target="G.806"></xref>.</t>
<t>In this document we refer to a Label Edge Router (LER), for a given
LSP or Section, and to a PW Terminating Provider Edge (T-PE), for a
given PW, as an End Point. Further, we refer to a Label Switching
Router (LSR), for a given LSP, and to a PW Switching Provider Edge
(S-PE), for a given PW, as an Intermediate Point. This document does
not make a distinction between End Points (e.g., source and
destination) as it can be inferred from the context of the
sentences.</t>
<t>In this document we use the term "node" as a general reference to
End Points and Intermediate Points.</t>
<t>In this document we refer to both segment and concatenated segments
as segments (see <xref target="I-D.ietf-mpls-tp-requirements"></xref>
for definitions relating to the term "segment" as well as for other
definitions relating to MPLS-TP).</t>
</section>
</section>
<section title="OAM Requirements">
<t>This section lists the requirements by which the OAM functionality of
MPLS-TP should abide. Note that some requirements for this application
of MPLS are similar to some of those listed in RFC 4377 <xref
target="RFC4377"></xref>.</t>
<t>The requirements listed below may be met by one or more OAM
protocols; the definition or selection of these protocols is outside the
scope of this document.</t>
<section title="Architectural Requirements">
<section title="Scope of OAM">
<t>The protocol solutions developed to meet the requirements
identified in this document MUST be applicable to point-to-point
bidirectional PWs, point-to-point bidirectional LSPs, and
point-to-point bidirectional Sections and SHOULD additionaly be
applicable to unidirectional point-to-point and point-to-multipoint
LSPs.</t>
<t>The service emulated by a single segment or a multi-segment PW
may span multiple domains. An LSP may also span multiple domains. It
MUST be possible to operate OAM functions on a per domain basis.
More generally, the protocol solutions MUST be applicable end-to-end
and to segments.</t>
<t>Since LSPs may be stacked, the protocol solutions MUST be
applicable on any LSP, regardless of the label stack depth.
Furthermore it MUST be possible to estimate OAM fault and
performance metrics of a single PW or LSP segment or of an aggregate
of PWs or LSPs segments.</t>
</section>
<section title="Independence">
<t>The protocol solutions SHOULD be independent of the underlying
tunnelling or point-to-point technology or transmission media.</t>
<t>The protocol solutions SHOULD be independent of the service a PW
may emulate.</t>
<t>Any OAM function operated on a PW, LSP or Section SHOULD be
independent of the OAM function(s) operated on a different PW, LSP
or Section. In other words, only the OAM functions operated on e.g.,
a given LSP should be used to achieve the OAM objectives for that
LSP. Note that independence should not be understood here in terms
of isolation as there can be interactions between OAM functions
operated on e.g., an LSP, and on another LSP or a PW.</t>
<t>Likewise, any OAM function applied to segment(s) of a PW or LSP
SHOULD be independent of the OAM function(s) operated on the
end-to-end PW or LSP. It SHOULD also be possible to distinguish an
OAM packet running over a segment of a PW or LSP from another OAM
packet running on the end-to-end PW or LSP. Furthermore, any OAM
function applied to segment(s) of a PW or LSP SHOULD be independent
of the OAM function(s) applied to other segment(s) of the same PW or
LSP. Finally, the protocol solutions MUST support the capability to
be concurrently and independently operated end-to-end and on
segments.</t>
<t>OAM functions MUST operate and be configurable even in the
absence of a control plane. Conversely, it SHOULD be possible to
enable/disable the capability to operate OAM functions as part of
connectivity management and it SHOULD also be possible to
enable/disable the capability to operate OAM functions after
connectivity has been established. In the latter case, the customer
MUST NOT perceive service degradation as a result of OAM
enabling/disabling. Ideally OAM enabling/disabling should take place
without introducing any customer impairments (e.g., no customer
packet losses). Procedures aimed to prevent any traffic impairment
MUST be defined for the enabling/disabling of OAM functions. Means
for configuring OAM functions and for connectivity management are
outside the scope of this document.</t>
</section>
<section anchor="ARF" title="Addressing, Routing and Forwarding">
<t>The OAM functionality may be deployed in a variety of
environments.<list style="symbols">
<t>In some environments (e.g., IP/MPLS environments), IP routing
and forwarding capabilities are inherently present in the
forwarding plane. In this case, it MUST be possible to operate
the OAM functions by relying on IP routing and forwarding
capabilities.</t>
<t>In some environments (e.g., MPLS-TP environments), IP routing
and forwarding capabilities may not necessarily be present in
the user plane. In this case, it MUST be possible to operate the
OAM functions without relying on IP routing and forwarding
capabilities.</t>
</list></t>
<t>In cases where OAM messages need to incorporate identification
information (e.g., source and/or destination nodes), the protocol
solution(s) MUST at least support an IP addressing structure and
MUST also be extensible to support additional identification
schemes.</t>
</section>
<section title="Interoperability and Interworking">
<t>It is REQUIRED that OAM interoperability is achieved across the
environments described in <xref target="ARF"></xref>. It is also
REQUIRED that the two first requirements of <xref
target="ARF"></xref> still hold and MUST still be met when
interoperability is achieved.</t>
<t>When MPLS-TP is run with IP routing and forwarding capabilities,
it MUST be possible to operate any of the existing IP/MPLS and PW
OAM protocols (e.g., LSP-Ping <xref target="RFC4379"></xref>,
MPLS-BFD <xref target="I-D.ietf-bfd-mpls"></xref>, VCCV <xref
target="RFC5085"></xref> and VCCV-BFD <xref
target="I-D.ietf-pwe3-vccv-bfd"></xref>).</t>
</section>
<section title="Data Plane">
<t>OAM functions operate in the data plane. OAM packets MUST run
in-band; that is, OAM packets for a specific PW, LSP or Section MUST
follow the exact same data path as user traffic of that PW, LSP or
Section. This is often referred to as fate sharing.</t>
<t>It MUST be possible to discriminate user traffic from OAM
packets. This includes a means to differentiate OAM packets from
user traffic as well as the capability to apply specific treatment
to OAM packets, at the nodes targeted by these OAM packets.</t>
<t>As part of the design of OAM protocol solution(s) for MPLS-TP, a
mechanism, for enabling the encapsulation and differentiation of OAM
messages on a PW, LSP or Section, MUST be provided. Such mechanism
SHOULD also support the encapsulation and differentiation of
existing IP/MPLS and PW OAM messages.</t>
</section>
</section>
<section title="Functional Requirements">
<t>Hereafter are listed the required functionalities composing the
MPLS-TP OAM toolset. The list may not be exhaustive and as such the
OAM mechanisms developed in support of the identified requirements
SHALL be extensible and thus SHALL NOT preclude the definition of
additional OAM functionalities, in the future.</t>
<t>The design of OAM mechanisms for MPLS-TP, MUST allow for the
ability to support experimental OAM functions. These functions MUST be
disabled by default.</t>
<t>The use of any OAM function MUST be optional and it MUST be
possible to choose which OAM function(s) to use and on which PW, LSP
or Section to apply it(them) to.</t>
<t>It is RECOMMENDED that the protocol solution, meeting one or more
functional requirement(s), be the same for PWs, LSPs and Sections.</t>
<t>It is RECOMMENDED that the protocol solution, meeting one or more
functional requirement(s), effectively provides a fully featured
function; that is, a function which is applicable to all the cases
identified for that functionality. In that context, protocol
solution(s) MUST state their applicability.</t>
<t>Unless otherwise stated, the OAM functionalities MUST NOT rely on
user traffic; that is, only OAM messages MUST be used to achieve the
objectives.</t>
<section title="General Requirements">
<t>If a defect or fault occurs on a PW, LSP or Section, mechanisms
MUST be provided to detect it, diagnose it, localize it, and notify
the appropriate nodes. Mechanisms SHOULD exist such that corrective
actions can be taken.</t>
<t>Furthermore, mechanisms MUST be available for a service provider
to be informed of a fault or defect affecting the service(s) it
provides, even if the fault or defect is located outside of his
domain.</t>
<t>The protocol solution(s) developed to meet these requirements may
rely on information exchange. Information exchange between various
nodes involved in the operation of an OAM function SHOULD be
reliable such that, for example, defects or faults are properly
detected or that state changes are effectively known by the
appropriate nodes.</t>
</section>
<section title="Continuity Checks">
<t>The MPLS-TP OAM toolset MUST provide functionality to enable the
verification of the continuity of a PW, LSP or Section.</t>
<t>This function SHOULD be performed between End Points of PWs, LSPs
and Sections.</t>
<t>This function SHOULD be performed pro-actively.</t>
</section>
<section title="Connectivity Verifications">
<t>The MPLS-TP OAM toolset MUST provide functionality to enable the
verification of the connectivity of a PW, LSP or Section.</t>
<t>This function SHOULD be performed between End Points and
Intermediate Points of PWs and LSPs, and between End Points of PWs,
LSPs and Sections.</t>
<t>This function SHOULD be performed on-demand. This function SHOULD
be performed pro-actively only between End Points of PWs, LSPs and
Sections.</t>
</section>
<section title="Diagnostic">
<t>The MPLS-TP OAM toolset MAY provide functionality to enable the
conduction of diagnostic tests on a PW, LSP or Section. An example
of such diagnotic test would consist in looping the traffic at an
Intermediate Point, back to the End Point it originates from.
Another example of such diagnotic test would consist in estimating
the bandwidth of e.g., an LSP.</t>
<t>This function SHOULD be performed on-demand.</t>
<t>This function SHOULD be performed between End Points and
Intermediate Points of PWs and LSPs, and between End Points of PWs,
LSPs and Sections.</t>
</section>
<section title="Route Tracing">
<t>The MPLS-TP OAM toolset MUST provide functionality to enable an
End Point to discover the Intermediate (if any) and End Point(s)
along a PW, LSP or Section, and more generaly to trace the route of
a PW, LSP or Section. The information collected MUST include
identifiers related to the nodes and interfaces composing that
route.</t>
<t>This function SHOULD be performed on-demand.</t>
<t>This function SHOULD be performed between End Points and
Intermediate Points of PWs and LSPs, and between End Points of PWs,
LSPs and Sections.</t>
</section>
<section title="Lock Instruct">
<t>The MPLS-TP OAM toolset MUST provide functionality to enable an
End Point of a PW, LSP or Section to instruct its associated End
Point(s) to lock the PW, LSP or Section. Note that lock corresponds
to an administrative status in which forwarding traffic on and from
the PW, LSP or Section is disabled.</t>
<t>This function SHOULD be performed on-demand.</t>
<t>This function SHOULD be performed between End Points of PWs, LSPs
and Sections.</t>
</section>
<section title="Lock Reporting">
<t>The MPLS-TP OAM toolset MUST provide functionality to enable an
Intermediate Point of a PW or LSP to report, to an End Point of that
same PW or LSP, an external lock condition affecting that PW or
LSP.</t>
<t>This function SHOULD be performed pro-actively.</t>
<t>This function SHOULD be performed between Intermediate Points and
End Points of PWs and LSPs.</t>
</section>
<section title="Alarm Reporting">
<t>The MPLS-TP OAM toolset MUST provide functionality to enable an
Intermediate Point of a PW or LSP to report, to an End Point of that
same PW or LSP, a fault or defect condition affecting that PW or
LSP.</t>
<t>This function SHOULD be performed pro-actively.</t>
<t>This function SHOULD be performed between Intermediate Points and
End Points of PWs and LSPs.</t>
</section>
<section title="Remote Defect Indication">
<t>The MPLS-TP OAM toolset MUST provide functionality to enable an
End Point to report, to its associated End Point, a fault or defect
condition that it detects on a PW, LSP or Section for which they are
the End Points.</t>
<t>This function SHOULD be performed pro-actively.</t>
<t>This function SHOULD be performed between End Points of PWs, LSPs
and Sections.</t>
</section>
<section title="Client Failure Indication">
<t>The MPLS-TP OAM toolset MUST provide functionality to enable the
propagation, across an MPLS-TP network, of information pertaining to
a client defect of fault condition detected at an End Point of a PW
or LSP, if the client layer OAM mechanisms do not provide an alarm
notification/propagation mechanism.</t>
<t>This function SHOULD be performed pro-actively.</t>
<t>This function SHOULD be performed between End Points of PWs and
LSPs.</t>
</section>
<section title="Packet Loss">
<t>The MPLS-TP OAM toolset MUST provide functionality to enable the
quantification of packet loss ratio over a PW, LSP or Section.</t>
<t>Note that packet loss ratio is the ratio of the user packets not
delivered to the total number of user packets transmitted during a
defined time interval. The number of user packets not delivered is
the difference between the number of user packets transmitted by an
End Point and the number of user packets received at an End
Point.</t>
<t>This function MAY either be performed pro-actively or
on-demand.</t>
<t>This function SHOULD be performed between End Points of PWs, LSPs
and Sections.</t>
<t>It SHOULD be possible to rely on user-plane traffic to achieve
that functionality.</t>
</section>
<section title="Delay Measurement">
<t>The MPLS-TP OAM toolset MUST provide functionality to enable the
quantification of the one-way, and if appropriate, the two-way,
delay of a PW, LSP or Section.<list style="symbols">
<t>One-way delay is the time elapsed from the start of
transmission of the first bit of a packet by an End Point until
the reception of the last bit of that packet by the other End
Point.</t>
<t>Two-way delay is the time elapsed from the start of
transmission of the first bit of a packet by a End Point until
the reception of the last bit of that packet by the same End
Point, when loopback is performed at the other End Point.</t>
</list></t>
<t>This function SHOULD be performed on-demand and MAY be perform
pro-actively.</t>
<t>This function SHOULD be performed between End Points of PWs, LSPs
and Sections.</t>
<t>It SHOULD be possible to rely on user-plane traffic to achieve
that functionality.</t>
</section>
</section>
</section>
<section title="Congestion Considerations">
<t>A mechanism (e.g., rate limiting) MUST be provided to prevent OAM
packets from causing congestion in the PSN.</t>
</section>
<section title="Security Considerations">
<t>This document, as itself, does not imply any security consideration
but OAM, as such, is subject to several security considerations. OAM
messages can reveal sensitive information such as passwords, performance
data and details about e.g., the network topology.</t>
<t>The nature of OAM therefore suggests having some form of
authentication, authorization and encryption in place. This will prevent
unauthorized access to MPLS-TP equipment and it will prevent third
parties from learning about sensitive information about the transport
network.</t>
<t>In general, mechanisms SHOULD be provided to ensure that OAM
functions cannot be accessed unauthorized.</t>
<t>Further, OAM messages MAY be authenticated to prove their origin and
to make sure that they are destined for the receiving node.</t>
<t>An OAM packet received over a PW, LSP or Section MUST NOT be
forwarded beyond the End Point of that PW, LSP or Section, so as to
avoid that the OAM packet leaves the current administrative domain.</t>
</section>
<section title="IANA Considerations">
<t>There are no IANA actions required by this draft.</t>
</section>
<section title="Acknowledgements">
<t>The editors gratefully acknowledge the contributions of Matthew
Bocci, Italo Busi, Thomas Dietz, Huub van Helvoort, Wataru Imajuku, Marc
Lasserre, Lieven Levrau, Han Li, Julien Meuric, Philippe Niger, Benjamin
Niven-Jenkins, Jing Ruiquan, Nurit Sprecher, Yuji Tochio, Satoshi Ueno
and Yaacov Weingarten.</t>
<t>The authors would like to thank all members of the teams (the Joint
Working Team, the MPLS Interoperability Design Team in IETF and the
MPLS-TP Ad Hoc Group in ITU-T) involved in the definition and
specification of MPLS-TP.</t>
</section>
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<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119"?>
<reference anchor="G.806">
<front>
<title>Characteristics of transport equipment - Description
methodology and generic functionality</title>
<author>
<organization>ITU-T Recommendation G.806</organization>
</author>
<date year="2009" />
</front>
</reference>
<?rfc include="reference.RFC.4379"?>
<?rfc include="reference.RFC.5085"?>
</references>
<references title="Informative References">
<?rfc include="reference.I-D.ietf-mpls-tp-framework"?>
<?rfc include="reference.I-D.ietf-mpls-tp-requirements"?>
<reference anchor="Y.Sup4">
<front>
<title>ITU-T Y.1300-series: Supplement on transport requirements for
T-MPLS OAM and considerations for the application of IETF MPLS
technology</title>
<author>
<organization>ITU-T Supplement Y.Sup4</organization>
</author>
<date year="2008" />
</front>
</reference>
<?rfc include="reference.RFC.4377"?>
<?rfc include="reference.I-D.ietf-bfd-mpls"?>
<?rfc include="reference.I-D.ietf-pwe3-vccv-bfd"?>
</references>
</back>
</rfc>
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