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Keywords: [--------], MPLS-TP, OAM
Internet Engineering Task Force (IETF) M. Vigoureux, Ed.
Request for Comments: 5860 Alcatel-Lucent
Category: Standards Track D. Ward, Ed.
ISSN: 2070-1721 Juniper Networks
M. Betts, Ed.
M. C. Betts Consulting Ltd.
May 2010
Requirements for Operations, Administration, and Maintenance (OAM)
in MPLS Transport Networks
Abstract
This document lists architectural and functional requirements for the
Operations, Administration, and Maintenance of MPLS Transport
Profile. These requirements apply to pseudowires, Label Switched
Paths, and Sections.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5860.
Copyright Notice
Copyright (c) 2010 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
(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.
Vigoureux, et al. Standards Track [Page 1]
RFC 5860 OAM Requirements for MPLS-TP May 2010
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Scope of This Document . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language and Terminology . . . . . . . . . . 4
2. OAM Requirements . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Architectural Requirements . . . . . . . . . . . . . . . . 6
2.1.1. Scope of OAM . . . . . . . . . . . . . . . . . . . . . 6
2.1.2. Independence . . . . . . . . . . . . . . . . . . . . . 6
2.1.3. Data Plane . . . . . . . . . . . . . . . . . . . . . . 7
2.1.4. OAM and IP Capabilities . . . . . . . . . . . . . . . 7
2.1.5. Interoperability and Interworking . . . . . . . . . . 8
2.1.6. Configuration . . . . . . . . . . . . . . . . . . . . 8
2.2. Functional Requirements . . . . . . . . . . . . . . . . . 9
2.2.1. General Requirements . . . . . . . . . . . . . . . . . 9
2.2.2. Continuity Checks . . . . . . . . . . . . . . . . . . 10
2.2.3. Connectivity Verifications . . . . . . . . . . . . . . 10
2.2.4. Route Tracing . . . . . . . . . . . . . . . . . . . . 11
2.2.5. Diagnostic Tests . . . . . . . . . . . . . . . . . . . 11
2.2.6. Lock Instruct . . . . . . . . . . . . . . . . . . . . 11
2.2.7. Lock Reporting . . . . . . . . . . . . . . . . . . . . 12
2.2.8. Alarm Reporting . . . . . . . . . . . . . . . . . . . 12
2.2.9. Remote Defect Indication . . . . . . . . . . . . . . . 13
2.2.10. Client Failure Indication . . . . . . . . . . . . . . 13
2.2.11. Packet Loss Measurement . . . . . . . . . . . . . . . 13
2.2.12. Packet Delay Measurement . . . . . . . . . . . . . . . 14
3. Congestion Considerations . . . . . . . . . . . . . . . . . . 15
4. Security Considerations . . . . . . . . . . . . . . . . . . . 15
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
6.1. Normative References . . . . . . . . . . . . . . . . . . . 16
6.2. Informative References . . . . . . . . . . . . . . . . . . 16
Vigoureux, et al. Standards Track [Page 2]
RFC 5860 OAM Requirements for MPLS-TP May 2010
1. Introduction
In the context of MPLS Transport Profile (MPLS-TP, see [9] and [1]),
the rationales for Operations, Administration, and Maintenance (OAM)
are twofold as it can serve:
o as a network-oriented functionality, used by a transport network
operator to monitor his network infrastructure and to implement
internal mechanisms in order to enhance the general behavior and
the level of performance of his network (e.g., protection
mechanism in case of node or link failure). As an example, fault
localization is typically associated with this use case.
o as a service-oriented functionality, 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 Agreement (SLA) 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.
More generally, OAM is an important and fundamental functionality in
transport networks as it contributes to:
o the reduction of operational complexity and costs, by allowing for
efficient and automatic detection, localization, and handling and
diagnosis of defects, as well as by minimizing service
interruptions and operational repair times.
o the enhancement of network availability, by ensuring that defects
(for example, those resulting in misdirected customer traffic) and
faults are detected, diagnosed, and dealt with before a customer
reports the problem.
o meeting 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.
1.1. Scope of This Document
This document lists architectural and functional requirements for the
OAM functionality of MPLS-TP. These requirements apply to
pseudowires (PWs), Label Switched Paths (LSPs), and Sections.
These requirements are derived from the set of requirements specified
by ITU-T and published in the ITU-T Supplement Y.Sup4 [10].
Vigoureux, et al. Standards Track [Page 3]
RFC 5860 OAM Requirements for MPLS-TP May 2010
By covering transport specificities, these requirements complement
those identified in RFC 4377 [11]; yet, some requirements may be
similar.
This document only lists architectural and functional OAM
requirements. It does not detail the implications of their
applicability to the various types (e.g., point-to-point, point-to-
multipoint, unidirectional, bidirectional, etc.) of PWs, LSPs, and
Sections. Furthermore, this document does not provide requirements
on how the protocol solution(s) should behave to achieve the
functional objectives. Please see [12] for further information.
Note that the OAM functions 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 by detecting failure conditions, but may
also be used for performance monitoring 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 function should be used for which application.
Note also that it is anticipated that implementers may wish to
implement OAM message handling in hardware. Although not a
requirement, this fact could be taken as a design consideration.
1.2. Requirements Language and Terminology
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 [2].
Although this document is not a protocol specification, the use of
this language clarifies the instructions to protocol designers
producing solutions that satisfy the requirements set out in this
document.
In this document, we:
o 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 [3].
o 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 [3].
Vigoureux, et al. Standards Track [Page 4]
RFC 5860 OAM Requirements for MPLS-TP May 2010
o refer to OAM actions that are carried out continuously or at least
over long periods of time, permitting proactive reporting of fault
and/or performance results as proactive OAM.
o refer to OAM actions that are initiated via manual intervention
for a limited time to carry out troubleshooting as on-demand OAM.
o 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.
o use the term "node" as a general reference to End Points and
Intermediate Points.
o refer to both segment and concatenated segments as segments (see
[1] for definitions relating to the term "segment" as well as for
other definitions relating to MPLS-TP).
o refer to both single segment PWs and multi-segment PWs as PWs.
o refer to both bidirectional associated LSPs and bidirectional co-
routed LSPs as bidirectional LSPs.
2. OAM Requirements
This section lists the requirements by which the OAM functionality of
MPLS-TP should abide.
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.
RFC 5654 [1] states (Requirement #2) that the MPLS-TP design, SHOULD
as far as reasonably possible, reuse existing MPLS standards. This
general requirement applies to MPLS-TP OAM. MPLS-TP OAM is defined
in this document through a set of functional requirements. These
requirements will be met by protocol solutions defined in other
documents. The way in which those protocols are operated and the way
in which a network operator can control and use the MPLS-TP OAM
functions SHOULD be as similar as possible to the mechanisms and
techniques used to operate OAM in other transport technologies.
Vigoureux, et al. Standards Track [Page 5]
RFC 5860 OAM Requirements for MPLS-TP May 2010
2.1. Architectural Requirements
2.1.1. Scope of OAM
The protocol solution(s) developed to meet the requirements
identified in this document MUST at least be applicable to point-to-
point bidirectional PWs, point-to-point co-routed bidirectional LSPs,
and point-to-point bidirectional Sections. Section 2.2 provides
additional information with regard to the applicability to point-to-
point associated bidirectional LSPs, point-to-point unidirectional
LSPs, and point-to-multipoint LSPs.
The service emulated by a PW may span multiple domains. An LSP may
also span multiple domains. The protocol solution(s) MUST be
applicable to end-to-end and to segments. More generally, it MUST be
possible to operate OAM functions on a per-domain basis and across
multiple domains.
Since LSPs may be stacked, the protocol solution(s) 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 PW or LSP segments.
2.1.2. Independence
The protocol solution(s) SHOULD be independent of the underlying
tunneling or point-to-point technology or transmission media.
The protocol solution(s) SHOULD be independent of the service a PW
may emulate.
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 a
given LSP (for example) should be used to achieve the OAM objectives
for that LSP.
The protocol solution(s) MUST support the capability to be
concurrently and independently operated end-to-end and on segments.
Therefore, 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.
Vigoureux, et al. Standards Track [Page 6]
RFC 5860 OAM Requirements for MPLS-TP May 2010
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.
Note: Independence should not be understood in terms of isolation
as there can be interactions between OAM functions operated, for
example, on two different LSPs.
2.1.3. Data Plane
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.
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 processing these OAM packets.
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.
2.1.4. OAM and IP Capabilities
There are environments where IP capabilities are present in the data
plane. IP/MPLS environments are examples of such environments.
There are also environments where IP capabilities may not be present
in the data plane. MPLS-TP environments are examples of environments
where IP capabilities might or might not be present.
Note: Presence or absence of IP capabilities is deployment
scenario dependent.
It MUST be possible to deploy the OAM functionality in any of these
environments. As a result, it MUST be possible to operate OAM
functions with or without relying on IP capabilities, and it MUST be
possible to choose to make use of IP capabilities when these are
present.
Furthermore, the mechanism required for enabling the encapsulation
and differentiation of OAM messages (see Section 2.1.3) MUST support
the capability to differentiate OAM messages of an OAM function
Vigoureux, et al. Standards Track [Page 7]
RFC 5860 OAM Requirements for MPLS-TP May 2010
operated by relying on IP capabilities (e.g., using encapsulation in
an IP header) from OAM messages of an OAM function operated without
relying on any IP capability.
Note that IP capabilities include the capability to form a standard
IP header, to encapsulate a payload in an IP header, to parse and
analyze the fields of an IP header, and to take actions based on the
content of these fields.
For certain functions, OAM messages need to incorporate
identification information (e.g., of source and/or destination
nodes). The protocol solution(s) MUST at least support
identification information in the form of an IP addressing structure
and MUST also be extensible to support additional identification
schemes.
2.1.5. Interoperability and Interworking
It is REQUIRED that OAM interoperability is achieved between distinct
domains materializing the environments described in Section 2.1.4.
It is also REQUIRED that the first two requirements of Section 2.1.4
still hold and MUST still be met when interoperability is achieved.
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 [4], MPLS-BFD [13], VCCV [5], and VCCV-BFD
[14]).
2.1.6. Configuration
OAM functions MUST operate and be configurable even in the absence of
a control plane. Conversely, it SHOULD be possible to configure as
well as enable/disable the capability to operate OAM functions as
part of connectivity management, and it SHOULD also be possible to
configure as well as 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.
Vigoureux, et al. Standards Track [Page 8]
RFC 5860 OAM Requirements for MPLS-TP May 2010
2.2. Functional Requirements
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.
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.
The use of any OAM function MUST be optional and it MUST be possible
to select the set of OAM function(s) to use on any PW, LSP, or
Section.
It is RECOMMENDED that any protocol solution, meeting one or more
functional requirement(s), be the same for PWs, LSPs, and Sections.
It is RECOMMENDED that any protocol solution, meeting one or more
functional requirement(s), effectively provides a fully featured
function; that is, a function that is applicable to all the cases
identified for that functionality. In that context, protocol
solution(s) MUST state their applicability.
Unless otherwise stated, the OAM functionalities MUST NOT rely on
user traffic; that is, only OAM messages MUST be used to achieve the
objectives.
For the on-demand OAM functions, the result of which may vary
depending on packet size, it SHOULD be possible to perform these
functions using different packet sizes.
2.2.1. General Requirements
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.
Furthermore, mechanisms MUST be available for a service provider to
be aware of a fault or defect affecting the service(s) he provides,
even if the fault or defect is located outside of his domain.
Vigoureux, et al. Standards Track [Page 9]
RFC 5860 OAM Requirements for MPLS-TP May 2010
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.
2.2.2. Continuity Checks
The MPLS-TP OAM toolset MUST provide a function to enable an End
Point to monitor the liveness of a PW, LSP, or Section.
This function SHOULD be performed between End Points of PWs, LSPs,
and Sections.
This function SHOULD be performed proactively.
The protocol solution(s) developed to perform this function MUST also
apply to point-to-point associated bidirectional LSPs, point-to-point
unidirectional LSPs, and point-to-multipoint LSPs.
2.2.3. Connectivity Verifications
The MPLS-TP OAM toolset MUST provide a function to enable an End
Point to determine whether or not it is connected to specific End
Point(s) by means of the expected PW, LSP, or Section.
This function SHOULD be performed proactively between End Points of
PWs, LSPs, and Sections.
This function SHOULD be performed on-demand between End Points and
Intermediate Points of PWs and LSPs, and between End Points of PWs,
LSPs, and Sections.
The protocol solution(s) developed to perform this function
proactively MUST also apply to point-to-point associated
bidirectional LSPs, point-to-point unidirectional LSPs, and point-to-
multipoint LSPs.
The protocol solution(s) developed to perform this function on-demand
MAY also apply to point-to-point associated bidirectional LSPs, to
point-to-point unidirectional LSPs, and point-to-multipoint LSPs in
case a return path exists.
Vigoureux, et al. Standards Track [Page 10]
RFC 5860 OAM Requirements for MPLS-TP May 2010
2.2.4. Route Tracing
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 generally 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.
This function SHOULD be performed on-demand.
This function SHOULD be performed between End Points and Intermediate
Points of PWs and LSPs, and between End Points of PWs, LSPs, and
Sections.
The protocol solution(s) developed to perform this function MAY also
apply to point-to-point associated bidirectional LSPs, to point-to-
point unidirectional LSPs, and point-to-multipoint LSPs in case a
return path exists.
2.2.5. Diagnostic Tests
The MPLS-TP OAM toolset MUST provide a function to enable conducting
diagnostic tests on a PW, LSP, or Section. An example of such a
diagnostic test consists of performing a loop-back function at a node
such that all OAM and data traffic are looped back to the originating
End Point. Another example of such diagnostic test consists in
estimating the bandwidth of, e.g., an LSP.
This function SHOULD be performed on-demand.
This function SHOULD be performed between End Points and Intermediate
Points of PWs and LSPs, and between End Points of PWs, LSPs, and
Sections.
The protocol solution(s) developed to perform this function MAY also
apply to point-to-point associated bidirectional LSPs, to point-to-
point unidirectional LSPs and point-to-multipoint LSPs, in case a
return path exists.
2.2.6. Lock Instruct
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 it is expected that only test
traffic, if any, and OAM (dedicated to the PW, LSP, or Section) can
be mapped on that PW, LSP, or Section.
Vigoureux, et al. Standards Track [Page 11]
RFC 5860 OAM Requirements for MPLS-TP May 2010
This function SHOULD be performed on-demand.
This function SHOULD be performed between End Points of PWs, LSPs,
and Sections.
The protocol solution(s) developed to perform this function MUST also
apply to point-to-point associated bidirectional LSPs, point-to-point
unidirectional LSPs, and point-to-multipoint LSPs.
2.2.7. Lock Reporting
Based on the tunneling capabilities of MPLS, there are cases where
Intermediate Point(s) of a PW or of an LSP coincide with End Point(s)
of another LSP on which the former is mapped/tunneled. Further, it
may happen that the tunnel LSP is out of service as a result of a
lock action on that tunnel LSP. By means outside of the scope of
this document, the Intermediate Point(s) of the PW or LSP may be
aware of this condition. The MPLS-TP OAM toolset MUST provide a
function to enable an Intermediate Point of a PW or LSP to report, to
an End Point of that same PW or LSP, a lock condition indirectly
affecting that PW or LSP.
This function SHOULD be performed proactively.
This function SHOULD be performed between Intermediate Points and End
Points of PWs and LSPs.
The protocol solution(s) developed to perform this function MUST also
apply to point-to-point associated bidirectional LSPs, point-to-point
unidirectional LSPs, and point-to-multipoint LSPs.
2.2.8. Alarm Reporting
Based on the tunneling capabilities of MPLS, there are cases where
Intermediate Point(s) of a PW or of an LSP coincide with End Point(s)
of another LSP on which the former is mapped/tunneled. Further, it
may happen that the tunnel LSP be out of service as a result of a
fault on that tunnel LSP. By means outside of the scope of this
document, the Intermediate Point(s) of the PW or LSP may be aware of
this condition. 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 indirectly
affecting that PW or LSP.
This function SHOULD be performed proactively.
This function SHOULD be performed between Intermediate Points and End
Points of PWs and LSPs.
Vigoureux, et al. Standards Track [Page 12]
RFC 5860 OAM Requirements for MPLS-TP May 2010
The protocol solution(s) developed to perform this function MUST also
apply to point-to-point associated bidirectional LSPs, point-to-point
unidirectional LSPs, and point-to-multipoint LSPs.
2.2.9. Remote Defect Indication
The MPLS-TP OAM toolset MUST provide a function 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.
This function SHOULD be performed proactively.
This function SHOULD be performed between End Points of PWs, LSPs,
and Sections.
The protocol solution(s) developed to perform this function MUST also
apply to point-to-point associated bidirectional LSPs and MAY also
apply to point-to-point unidirectional LSPs and point-to-multipoint
LSPs in case a return path exists.
2.2.10. Client Failure Indication
The MPLS-TP OAM toolset MUST provide a function to enable the
propagation, from edge to edge of an MPLS-TP network, of information
pertaining to a client (i.e., external to the MPLS-TP network) defect
or fault condition detected at an End Point of a PW or LSP, if the
client layer OAM functionality does not provide an alarm
notification/propagation functionality.
This function SHOULD be performed proactively.
This function SHOULD be performed between End Points of PWs and LSPs.
The protocol solution(s) developed to perform this function MUST also
apply to point-to-point associated bidirectional LSPs, point-to-point
unidirectional LSPs, and point-to-multipoint LSPs.
2.2.11. Packet Loss Measurement
The MPLS-TP OAM toolset MUST provide a function to enable the
quantification of packet loss ratio over a PW, LSP, or Section.
The loss of a packet is defined in RFC2680 [6] (see Section 2.4).
This definition is used here.
Vigoureux, et al. Standards Track [Page 13]
RFC 5860 OAM Requirements for MPLS-TP May 2010
Packet-loss ratio is defined here to be the ratio of the number of
user packets lost to the total number of user packets sent during a
defined time interval.
This function MAY either be performed proactively or on-demand.
This function SHOULD be performed between End Points of PWs, LSPs,
and Sections.
It SHOULD be possible to rely on user traffic to perform this
functionality.
The protocol solution(s) developed to perform this function MUST also
apply to point-to-point associated bidirectional LSPs, point-to-point
unidirectional LSPs, and point-to-multipoint LSPs.
2.2.12. Packet Delay Measurement
The MPLS-TP OAM toolset MUST provide a function to enable the
quantification of the one-way, and if appropriate, the two-way, delay
of a PW, LSP, or Section.
o The one-way delay is defined in [7] to be 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.
o The two-way delay is defined in [8] to be 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
same End Point.
Two-way delay may be quantified using data traffic loopback at the
remote End Point of the PW, LSP, or Section (see Section 2.2.5).
Accurate quantification of one-way delay may require clock
synchronization, the means for which are outside the scope of this
document.
This function SHOULD be performed on-demand and MAY be performed
proactively.
This function SHOULD be performed between End Points of PWs, LSPs,
and Sections.
Vigoureux, et al. Standards Track [Page 14]
RFC 5860 OAM Requirements for MPLS-TP May 2010
The protocol solution(s) developed to perform this function MUST also
apply to point-to-point associated bidirectional LSPs, point-to-point
unidirectional LSPs, and point-to-multipoint LSPs, but only to enable
the quantification of the one-way delay.
3. Congestion Considerations
A mechanism (e.g., rate limiting) MUST be provided to prevent OAM
packets from causing congestion in the Packet Switched Network.
4. Security Considerations
This document, in 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.
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.
OAM systems (network management stations) SHOULD be designed such
that OAM functions cannot be accessed without authorization.
OAM protocol solutions MUST include the facility for OAM messages to
authenticated to prove their origin and to make sure that they are
destined for the receiving node. The use of such facilities MUST be
configurable.
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.
5. Acknowledgements
The editors gratefully acknowledge the contributions of Matthew
Bocci, Italo Busi, Thomas Dietz, Annamaria Fulignoli, Huub van
Helvoort, Enrique Hernandez-Valencia, Wataru Imajuku, Kam Lam, Marc
Lasserre, Lieven Levrau, Han Li, Julien Meuric, Philippe Niger,
Benjamin Niven-Jenkins, Jing Ruiquan, Nurit Sprecher, Yuji Tochio,
Satoshi Ueno, and Yaacov Weingarten.
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.
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RFC 5860 OAM Requirements for MPLS-TP May 2010
6. References
6.1. Normative References
[1] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and
S. Ueno, "Requirements of an MPLS Transport Profile", RFC 5654,
September 2009.
[2] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[3] ITU-T Recommendation G.806, "Characteristics of transport
equipment - Description methodology and generic functionality",
2009.
[4] Kompella, K. and G. Swallow, "Detecting Multi-Protocol Label
Switched (MPLS) Data Plane Failures", RFC 4379, February 2006.
[5] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007.
[6] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way Packet
Loss Metric for IPPM", RFC 2680, September 1999.
[7] Almes, G., Kalidindi, S., and M. Zekauskas, "A One-way Delay
Metric for IPPM", RFC 2679, September 1999.
[8] Almes, G., Kalidindi, S., and M. Zekauskas, "A Round-trip Delay
Metric for IPPM", RFC 2681, September 1999.
6.2. Informative References
[9] Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau, L.,
and L. Berger, "A Framework for MPLS in Transport Networks",
Work in Progress, May 2010.
[10] ITU-T Supplement Y.Sup4, "ITU-T Y.1300-series: Supplement on
transport requirements for T-MPLS OAM and considerations for
the application of IETF MPLS technology", 2008.
[11] Nadeau, T., Morrow, M., Swallow, G., Allan, D., and S.
Matsushima, "Operations and Management (OAM) Requirements for
Multi-Protocol Label Switched (MPLS) Networks", RFC 4377,
February 2006.
[12] Busi, I., Ed., Niven-Jenkins, B., Ed., and D. Allan, Ed.,
"MPLS-TP OAM Framework", Work in Progress, April 2010.
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RFC 5860 OAM Requirements for MPLS-TP May 2010
[13] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow, "BFD
For MPLS LSPs", Work in Progress, June 2008.
[14] Nadeau, T., Ed. and C. Pignataro, Ed., "Bidirectional
Forwarding Detection (BFD) for the Pseudowire Virtual Circuit
Connectivity Verification (VCCV)", Work in Progress, July 2009.
Authors' Addresses
Martin Vigoureux (editor)
Alcatel-Lucent
Route de Villejust
Nozay 91620
France
EMail: martin.vigoureux@alcatel-lucent.com
David Ward (editor)
Juniper Networks
EMail: dward@juniper.net
Malcolm Betts (editor)
M. C. Betts Consulting Ltd.
EMail: malcolm.betts@rogers.com
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