Network Working Group N. Sprecher
Internet-Draft Nokia Siemens Networks
Intended status: Informational L. Fang
Expires: March 30, 2012 Cisco
September 27, 2011
An Overview of the OAM Tool Set for MPLS based Transport Networks
draft-ietf-mpls-tp-oam-analysis-05.txt
Abstract
This document provides an overview of the OAM toolset for MPLS based
Transport Networks. The toolset consists of a comprehensive set of
fault management and performance monitoring capabilities (operating
in the data-plane) which are appropriate for transport networks as
required in [MPLS-TP OAM Reqs] and support the network and services
at different nested levels. This overview includes a brief recap of
MPLS-TP OAM requirements and functions, and of generic mechanisms
created in the MPLS data plane to allow the OAM packets run in-band
and share their fate with data packets. The protocol definitions for
each of the MPLS-TP OAM tools are defined in separate documents (RFCs
or Working Group drafts) which are referenced by this document.
This document is a product of a joint Internet Engineering Task Force
(IETF) / International Telecommunications Union Telecommunications
Standardization Sector (ITU-T) effort to include an MPLS Transport
Profile within the IETF MPLS and PWE3 architectures to support the
capabilities and functionalities of a packet transport network as
defined by the ITU-T.
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
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on March 30, 2012.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1. Scope . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Contributing Authors . . . . . . . . . . . . . . . . . . . 5
1.3. Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . 6
2. Basic OAM Infrastructure Functionality . . . . . . . . . . . . 6
3. MPLS-TP OAM Functions . . . . . . . . . . . . . . . . . . . . 8
3.1. Continuity Check and Connectivity Verification . . . . . . 8
3.1.1. Documents for CC-V tools . . . . . . . . . . . . . . . 8
3.2. Remote Defect Indication . . . . . . . . . . . . . . . . . 9
3.2.1. Documents for RDI . . . . . . . . . . . . . . . . . . 9
3.3. Route Tracing . . . . . . . . . . . . . . . . . . . . . . 9
3.3.1. Documents for Route Tracing . . . . . . . . . . . . . 9
3.4. Alarm Reporting . . . . . . . . . . . . . . . . . . . . . 9
3.4.1. Documents for Alarm Reporting . . . . . . . . . . . . 9
3.5. Lock Instruct . . . . . . . . . . . . . . . . . . . . . . 10
3.5.1. Documents for Lock Instruct . . . . . . . . . . . . . 10
3.6. Lock Reporting . . . . . . . . . . . . . . . . . . . . . . 10
3.6.1. Documents for Lock Reporting . . . . . . . . . . . . . 10
3.7. Diagnostic . . . . . . . . . . . . . . . . . . . . . . . . 10
3.7.1. Documents for Diagnostic Testing . . . . . . . . . . . 11
3.8. Client Failure Indication . . . . . . . . . . . . . . . . 11
3.8.1. Documents for CFI . . . . . . . . . . . . . . . . . . 11
3.9. Packet Loss Measurement . . . . . . . . . . . . . . . . . 11
3.9.1. Documents for Packet Loss Measurement . . . . . . . . 11
3.10. Packet Delay Measurement . . . . . . . . . . . . . . . . . 11
3.10.1. Documents for Delay Measurement . . . . . . . . . . . 12
4. MPLS-TP OAM documents guide . . . . . . . . . . . . . . . . . 12
5. OAM Toolset Applicability and Utilization . . . . . . . . . . 14
5.1. Connectivity Check and Connectivity Verification . . . . . 14
5.2. Diagnostic Tests and Lock Instruct . . . . . . . . . . . . 15
5.3. Lock Reporting . . . . . . . . . . . . . . . . . . . . . . 15
5.4. Alarm Reporting and Link down Indication . . . . . . . . . 16
5.5. Remote Defect Indication . . . . . . . . . . . . . . . . . 16
5.6. Packet Loss and Delay Measurement . . . . . . . . . . . . 17
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
7. Security Considerations . . . . . . . . . . . . . . . . . . . 18
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 19
9.1. Normative References . . . . . . . . . . . . . . . . . . . 19
9.2. Informative References . . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 21
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1. Introduction
1.1. Scope
OAM (Operations, Administration, and Maintenance) plays a significant
role in carrier networks, providing methods for fault management and
performance monitoring in both the transport and the service layers
in order to improve their ability to support services with guaranteed
and strict Service Level Agreements (SLAs) while reducing their
operational costs.
[MPLS-TP Reqs], in general, and [MPLS-TP OAM Reqs], in particular,
define a set of requirements for OAM functionality for MPLS-Transport
Profile (MPLS-TP) Segments, Label Switched Paths (LSPs) (network
infrastructure) and Pseudowires (PWs) (services).
The OAM solution, developed by the joint IETF and ITU-T MPLS-TP
project, has three objectives:
o The OAM toolset should be developed based on existing MPLS
architecture, technology, and toolsets.
o The OAM operational experience should be similar to that in other
transport networks.
o The OAM toolset developed for MPLS based transport networks needs
to be fully inter-operable with existing MPLS OAM tools as
documented in [MPLS-TP OAM Reqs].
The MPLS-TP OAM toolset is based on the following existing tools:
o LSP-Ping as defined in [LSP Ping].
o Bidirectional Forwarding Detection (BFD) as defined in [BASE BFD]
and refined in [MPLS BFD].
o ITU-T OAM for Ethernet toolset as defined in [Y.1731] this will be
used for functionality guidelines for the performance measurement
tools that are not currently supported in MPLS.
It should be noted that certain extensions and adjustments have been
specified relative to the existing MPLS tools, in order to conform to
the transport environment and the requirements of MPLS-TP. However,
compatibility with the existing tools has been maintained.
This document provides an overview of the MPLS-TP OAM toolset, which
consists of tools for MPLS-TP fault management and performance
monitoring. This overview includes a brief recap of MPLS-TP OAM
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requirements and functions, and of the generic mechanisms used to
support the MPLS-TP OAM operation.
The protocol definitions for each individual MPLS-TP OAM tool are
specified in separate RFCs (or Working Group documents while this
document is work in progress), which are referenced by this document.
In addition, the document includes a table that cross-references the
solution documents to the OAM functionality supported. Finally, the
document presents the applicability and utilization of each tool in
the MPLS-TP OAM toolset.
1.2. Contributing Authors
Elisa Bellagamba Ericsson
Yaacov Weingarten Nokia Siemens Networks
Dan Frost Cisco
Nabil Bitar Verizon
Raymond Zhang Alcatel Lucent
Lei Wang Telenor
Kam Lee Yap XO Communications
John Drake Juniper
Yaakov Stein RAD
Anamaria Fulignoli Ericsson
Italo Busi Alcatel Lucent
Huub van Helvoort Huawei
Thomas Nadeau Computer Associate
Henry Yu TW Telecom
Mach Chen Huawei
Manuel Paul Deutsche Telekom
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1.3. Acronyms
This draft uses the following acronyms:
ACH Associated Channel Header
AIS Alarm Indication Signal
BFD Bidirectional Forwarding Detection
CC-V Continuity Check and Connectivity Verification
FM Fault Management
G-ACh Generic Associated Channel
GAL G-ACh Label
GMPLS Generalized Multi-Protocol Label Switching
IANA Internet Assigned Names Authority
LDI Link Down Indication
LKR Lock Report
LM Loss Measurement
LOC Loss of Continuity
LSP Label Switched Path
MEP Maintenance Entity Group End Point
MEG Maintenance Entity Group
MIP Maintenance Entity Group Intermediate Point
MPLS MultiProtocol Label Switching
MPLS-TP Transport Profile for MPLS
OAM Operations, Administration, and Maintenance
PM Performance Monitoring
PW Pseudowire
RDI Remote Defect Indication
SLA Service Level Agreement
TLV Type, Length, Value
VCCV Virtual Circuit Connectivity Verification
2. Basic OAM Infrastructure Functionality
[MPLS-TP OAM Reqs] defines a set of requirements on OAM architecture
and general principles of operations, which are evaluated below:
[MPLS-TP OAM Reqs] requires that --
o OAM mechanisms in MPLS-TP are independent of the transmission
media and of the client service being emulated by the PW.
o MPLS-TP OAM must be able to support both an IP based and non-IP
based environment. If the network is IP based, i.e. IP routing
and forwarding are available, then the MPLS-TP OAM toolset should
rely on the IP routing and forwarding capabilities. On the other
hand, in environments where IP functionality is not available, the
OAM tools must still be able to operate independent of IP
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forwarding and routing.
o all OAM protocols support identification information, at least in
the form of IP addressing structure and be extensible to support
additional identification schemes.
o OAM packets and the user traffic are congruent (i.e. OAM packets
are transmitted in-band) and there is a need to differentiate OAM
packets from user-plane packets. Inherent in this requirement is
the principle that full operation of the MPLS-TP OAM must be
possible independently of the control or management plane used to
operate the network.
o a single OAM solution and consistent OAM capabilities for LSPs,
PWs, and Sections.
o MPLS-TP OAM supports point-to-point bidirectional PWs, point- to-
point co-routed bidirectional LSPs, point-to-point bidirectional
Sections, point-to-point associated bidirectional LSPs, point-to-
point unidirectional LSPs, and point-to-multipoint LSPs. In
addition, MPLS-TP OAM supports these LSPs and PWs when they span
either a single or multiple domains.
o OAM packets may be directed to an intermediate point of a LSP/PW.
The following document-set addresses the basic requirements listed
above:
o The [MPLS-TP OAM Frwk] document describes the architectural
framework for conformance to the basic requirements listed above.
It also defines the basic relationships between the MPLS
structures, e.g. LSP, PW, and the structures necessary for OAM
functionality, i.e. the Managed Entity Group, its End-points, and
Intermediate Points.
o The [MPLS G-ACH] document specifies the use of the MPLS-TP in-band
control channels. It generalizes the applicability of the
Pseudowire (PW) Associated Channel Header (ACH) to MPLS LSPs and
Section, by defining a Generic Associated Channel (G-ACh). The
G-ACh allows control packets to be multiplexed transparently over
LSPs and sections, similar to that of PW VCCV [PW VCCV]. The
Generic Association Label (GAL) is defined by assigning a reserved
MPLS label value and is used to identify the OAM control packets.
The value of the ACH Channel Type field indicates the specific
protocol carried on the associated control channel. Each MPLS-TP
OAM protocol has an IANA assigned channel type allocated to it.
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o The creation of G-ACh and GAL provided the necessary mechanisms to
allow OAM packets run in-band and share their fate with data
packets. It is expected that all of the OAM protocols will be
used in conjunction with this Generic Associated Channel.
o The [MPLS TP Idents] document addresses the need of MPLS-TP to
support different addressing spaces. This document describes
different formats for addresses that could be used to identify the
transport entities in the network and referenced by the different
OAM protocols.
3. MPLS-TP OAM Functions
The following sections discuss the OAM functions that are required in
[MPLS-TP OAM Reqs] and expanded upon in [MPLS-TP OAM Frwk].
3.1. Continuity Check and Connectivity Verification
Continuity Check and Connectivity Verification (CC-V) are OAM
operations generally used in tandem, and complement each other.
These functions are generally run proactively, but may also be used
on-demand for diagnoses of a specific condition. Proactively
[MPLS-TP OAM Reqs] states that the function should allow the MEPs to
monitor the liveliness and connectivity of a transport path (LSP, PW
or a section) between them. In on-demand mode, this function should
support monitoring between the MEPs and, in addition, between a MEP
and MIP. Note that as specified in sections 3.3 and 3.4 of [MPLS-TP
OAM Frwk], a MEP and a MIP can reside in an unspecified location
within a node, or in a particular interface on a specific side of the
forwarding engine.
The [MPLS-TP OAM Frwk] highlights the need for the CC-V messages to
include unique identification of the MEG that is being monitored and
the MEP that originated the message. The function, both proactively
and in on-demand mode, needs to be transmitted at regular
transmission rates pre-configured by the operator.
3.1.1. Documents for CC-V tools
[Pro CC-V] defines BFD extensions to support proactive CC-V
applications.
[Demand CV] provides LSP-Ping extensions that are used to implement
on-demand Connectivity Verification.
Both of these tools will be used within the framework of the basic
tools described above, in section 2.
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3.2. Remote Defect Indication
Remote Defect Indication (RDI) is used by a path end-point to report
that a defect is detected on a bi-directional connection to its peer
end-point. [MPLS-TP OAM Reqs] points out that this function may be
applied to a unidirectional LSP only if a return path exists.
[MPLS-TP OAM Frwk] points out that this function is associated with
the proactive CC-V function.
3.2.1. Documents for RDI
The [Pro CC-V] document includes an extension for BFD that would
include the RDI indication in the BFD format, and a specification of
how this indication is to be used.
3.3. Route Tracing
[MPLS-TP OAM Reqs] defines that there is a need for functionality
that would allow a path end-point to identify the intermediate (if
any) and end-points of the path (LSP, PW or a section). This
function would be used in on-demand mode. Normally, this path will
be used for bidirectional PW, LSP, and sections, however,
unidirectional paths may be supported only if a return path exists.
3.3.1. Documents for Route Tracing
The [Demand CV] document that specifies the LSP-Ping enhancements for
MPLS-TP on-demand Connectivity Verification includes information on
the use of LSP-Ping for route tracing of a MPLS-TP transport path.
3.4. Alarm Reporting
Alarm Reporting is a function used by an intermediate point of a path
(LSP or PW), that becomes aware of a fault on the path, to report to
the end-points of the path. [MPLS-TP OAM Frwk] states that this may
occur as a result of a defect condition discovered at a server layer.
The intermediate point generates an Alarm Indication Signal (AIS)
that continues until the fault is cleared. The consequent action of
this function is detailed in [MPLS-TP OAM Frwk].
3.4.1. Documents for Alarm Reporting
MPLS-TP defines a new protocol to address this functionality that is
documented in [Fault Mng]. This protocol uses all of the basic
mechanisms detailed in Section 2.
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3.5. Lock Instruct
The Lock Instruct function is an administrative control tool that
allows a path end-point to instruct its peer end-point to lock the
path (LSP, PW or section). The tool is necessary to support single-
side provisioning for administrative locking, according to . This
function is used on-demand.
3.5.1. Documents for Lock Instruct
The [LiLoopback] document describes the details of a new ACH based
protocol format for this functionality.
3.6. Lock Reporting
Lock reporting, defined in [MPLS-TP OAM Reqs], is similar to the
Alarm Reporting function described above. It is used by an
intermediate point to notify the end points of a transport path (LSP
or PW) that an administrative lock condition exists for this
transport path.
3.6.1. Documents for Lock Reporting
MPLS-TP defines a new protocol to address this functionality that is
documented in [Fault Mng]. This protocol uses all of the basic
mechanisms detailed in Section 2.
3.7. Diagnostic
The [MPLS-TP OAM Reqs] indicates that there is need to provide a OAM
function that would enable conducting different diagnostic tests on a
PW, LSP, or Section. The [MPLS-TP OAM Frwk] provides two types of
specific tests to be used through this functionality:
o Throughput Estimation - allowing the provider to verify the
bandwidth/throughput of a transport path. This is an out-of-
service tool, that uses special packets of varying sizes to test
the actual bandwidth and/or throughput of the path.
o Data-plane loopback - this out-of-service tool causes all traffic
that reaches the target node, either a MEP or MIP, to be looped
back to the originating MEP. For targeting MIPs, a co-routed bi-
directional path is required.
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3.7.1. Documents for Diagnostic Testing
The [LiLoopback] document describes the details of a new ACH based
protocol format for the Data-plane loopback functionality.
The tool for Throughput Estimation tool is under study.
3.8. Client Failure Indication
Client Failure Indication (CFI) is defined in [MPLS-TP OAM Reqs] to
allow the propagation information from one edge of the MPLS-TP
network to the other. The information concerns a defect to a client,
in the case that the client does not support alarm notification.
3.8.1. Documents for CFI
A new ACH-based protocol is described in [MPLS-TP CSF] that addresses
the functionality defined for client failure indication.
3.9. Packet Loss Measurement
Packet Loss Measurement is required, by [MPLS-TP OAM Reqs] to provide
a quantification of the packet loss ratio on a transport path. This
is the ratio of the number of user packets lost to the total number
of user packets during a defined time interval. To employ this
function, [MPLS-TP OAM Frwk] defines that the two end-points of the
transport path should exchange counters of messages transmitted and
received within a time period bounded by loss-measurement messages.
The framework warns that there may be small errors in the computation
that result from various issues.
3.9.1. Documents for Packet Loss Measurement
The [Loss-Delay] document describes the protocol formats and
procedures for using the tool. The tool logic is based on the
behavior of the parallel function described in [Y.1731].
3.10. Packet Delay Measurement
Packet Delay Measurement is a function that is used to measure one-
way or wo-way delay of a packet transmission between a pair of the
end-points of a path (PW, LSP, or Section), as described in [MPLS-TP
OAM Reqs]. Where:
o One-way packet delay is the time elapsed from the start of
transmission of the first bit of the packet by a source node until
the reception of the last bit of that packet by the destination
node.
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o Two-way packet delay is the time elapsed from the start of
transmission of the first bit of the packet by a source node until
the reception of the last bit of the loop-backed packet by the
same source node, when the loopback is performed at the packet's
destination node.
[MPLS-TP OAM Frwk] describes how the tool could be performed (both in
proactive and on-demand modes) for either one-way or two-way
measurement. However, it warns that the one-way delay option
requires precise time synchronization between the end-points.
3.10.1. Documents for Delay Measurement
The [Loss-Delay] document describes the protocol formats and
procedures for using the tool. The tool logic is based on the
behavior of the parallel function described in [Y.1731].
4. MPLS-TP OAM documents guide
The complete MPLS-TP OAM protocol suite is covered by a small set of
existing IETF documents. This set of documents may be expanded in
the future to cover additional OAM functionality. In order to allow
the reader to understand this set of documents, a cross-reference of
the existing documents (IETF RFCs or Internet drafts while this
document is work in progress) for the initial phase of the
specification of MPLS based transport networks is provided below.
Editor's note:
Only RFCs will be referenced in the final version of the document.
[MPLS G-ACH] provides a specification of the basic structure of
protocol messages for in-band data plane OAM in an MPLS environment.
[MPLS TP Idents] provides definitions of different formats that may
be used within OAM protocol messages to identify the network elements
of a MPLS based transport network.
The following table (Table 1) provides the summary of proactive
MPLS-TP OAM Fault Management toolset functions, associated tool/
protocol, and the corresponding IETF RFCs or Internet drafts where
they are defined.
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+------------------------+----------------------------+-------------+
| OAM Functions | OAM Tools/Protocols | RFCs / |
| | | Internet |
| | | Drafts |
+------------------------+----------------------------+-------------+
| Continuity Check and | Bidirectional Forwarding | [Pro CC-V] |
| Connectivity | Detection (BFD) | |
| Verification | | |
+------------------------+----------------------------+-------------+
| Remote Defect | Flag in Bidirectional | [Pro CC-V] |
| Indication (RDI) | Forwarding Detection (BFD) | |
| | message | |
+------------------------+----------------------------+-------------+
| Alarm Indication | G-ACh bases AIS message | [Fault Mng] |
| Signal (AIS) | | |
+------------------------+----------------------------+-------------+
| Link Down Indication | Flag in AIS message | [Fault Mng] |
| (LDI) | | |
+------------------------+----------------------------+-------------+
| Lock Reporting (LKR) | G-ACh bases LKR message | [Fault Mng] |
+------------------------+----------------------------+-------------+
| Client Signal Fail | G-ACh based CSF message | [MPLS-TP |
| (CSF) | | CSF] |
+------------------------+----------------------------+-------------+
Proactive Fault Management OAM Toolset
Table 1
The following table (Table 2) provides an overview of the on-demand
MPLS-TP OAM Fault Management toolset functions, associated tool/
protocol, and the corresponding IETF RFCs or Internet drafts where
they are defined.
+----------------------+-----------------------------+--------------+
| OAM Functions | OAM Tools/Protocols | RFCs / |
| | | Internet |
| | | Drafts |
+----------------------+-----------------------------+--------------+
| Connectivity | LSP Ping | [Demand CV] |
| Verification | | |
+----------------------+-----------------------------+--------------+
| Diagnostic: Loopback | (1) G-ACh based Loopback | [LiLoopback] |
| and Lock Instruct | and Lock Instruct, (2) LSP | |
| | Ping | |
+----------------------+-----------------------------+--------------+
| Lock Instruct(LI) | Flag in AIS message | [Fault Mng] |
+----------------------+-----------------------------+--------------+
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On Demand Fault Management OAM Toolset
Table 2
The following table (Table 3) provides the Performance Monitoring
Fuctions, asscociated tool/protocol definitions, and corresponding
RFCs or Internet Drafts.
+------------------+----------------------+-------------------------+
| OAM Functions | OAM Tools/Protocols | RFCs / Internet Drafts |
+------------------+----------------------+-------------------------+
| Packet Loss | G-ACh based LM & DM | [Loss-Delay] |
| Measurement (LM) | query messages | [TP-Loss-Delay-Profile] |
+------------------+----------------------+-------------------------+
| Packet Delay | G-ACh based LM & DM | [Loss-Delay] |
| Measurement (DM) | query messages | [TP-Loss-Delay-Profile] |
+------------------+----------------------+-------------------------+
| Throughput | derived from Loss | [Loss-Delay] |
| Measurement | Measurement | [TP-Loss-Delay-Profile] |
+------------------+----------------------+-------------------------+
| Delay Variation | derived from Delay | [Loss-Delay] |
| Measurement | Measurement | [TP-Loss-Delay-Profile] |
+------------------+----------------------+-------------------------+
Performance Monitoring OAM Toolset
Table 3
5. OAM Toolset Applicability and Utilization
The following subsections present the MPLS-TP OAM toolset from the
perspective of the specified protocols and identifies which of the
required functionality is supported by the particular protocol.
5.1. Connectivity Check and Connectivity Verification
Proactive Continuity Check and Connectivity Verification (CC-V)
functions are used to detect loss of continuity (LOC), and unintended
connectivity between two MEPs. Loss of connectivity, mis-merging,
mis-connectivity, or unexpected Maintenance Entity Group End Points
(MEPs) can be detected using the CC-V tools.
The CC-V tools are used to support MPLS-TP fault management,
performance management, and protection switching. Proactive CC-V
control packets are sent by the source MEP to sink MEP. The sink MEP
monitors the arrival of the CC-V control packets and detects the
defect. For bidirectional transport paths, the CC-V protocol is,
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usually, transmitted simutaneously in both directions.
The transmission interval of CC-V control packet can be configured.
For example:
o 3.3ms is the default interval for protection switching.
o 100ms is the default interval for performance monitoring.
o 1s is the default interval for fault management.
5.2. Diagnostic Tests and Lock Instruct
[LiLoopback] describes a protocol that provides a mechanism is
provided to Lock and unlock traffic (e.g. data and control traffic)
or specific OAM traffic at a specific LSR on the path of the MPLS-TP
LSP to allow loop back of the traffic to the source.
These diagnostic functions apply to associated bidirectional MPLS-TP
LSPs, including MPLS-TP LSPs, bi-directional RSVP-TE tunnels (which
is relevant for MPLS-TP dynamic control plane option with GMPLS), and
single segment and multi-segment pseudowires.
The Lock operation instruction is carried in an MPLS Loopback request
message sent from a MEP to a trail-end MEP of the LSP to request that
the LSP be taken out of service. In response, the Lock operation
reply is carried in a Loopback response message sent from the trail-
end MEP back to the originating MEP to report the result.
The loopback operations include:
o Lock: take an LSP out of service for maintenance.
o Unlock: Restore a previously locked LSP to service.
o Set_Full_Loopback and Set_OAM_Loopback
o Unset_Full_Loopback and Set_OAM_Loopback
Operators can use the loopback mode to test the connectivity or
performance (loss, delay, delay variation, and throughput) of given
LSP up to a specific node on the path of the LSP.
5.3. Lock Reporting
The Lock Report (LKR) function is used to communicate to the client
(sub-) layer MEPs the administrative locking of a server (sub-) layer
MEP, and consequential interruption of data traffic forwarding in the
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client (sub-) layer.
When operator is taking the LSP out of service for maintenance other
operational reason, using the LKR function can help to distinguish
the condition as administrative locking from defect condition.
The Lock Report function would also serve the purpose of alarm
suppression in the MPLS-TP network above the level of the Lock is
occurred. The receipt of an LKR message MAY be treated as the
equivalent of loss of continuity at the client layer.
5.4. Alarm Reporting and Link down Indication
Alarm Indication Signal (AIS) message serves the purpose of alarm
suppression upon the failure detection in the server (-sub) layer.
When the Link Down Indication (RDI) is set, the AIS message MAY be
used to trigger recovery mechanisms.
When a server MEP detects the failure, it asserts Loss of Continuity
(LOC) or signal fail which sets the flag up to generate OAM packet
with AIS message. The AIS message is forwarded to downstream sink
MEP in the client layer. This would enable the client layer to
suppress the generation of secondary alarms.
A Link Down Indication (LDI) flag is defined in the AIS message. The
LDI flag is set in the AIS message in response to detecting a fatal
failure in the server layer. Receipt of an AIS message with this
flag set MAY be interpreted by a MEP as an indication of signal fail
at the client layer.
Fault OAM messages are generated by intermediate nodes where an LSP
is switched, and propagated to the end points (MEPs).
From a practical point of view, when both proactive Continuity Check
functions and LDI are used, one may consider to run the proactive
Continuity Check functions at a slower rate (e.g. longer BFD hello
intervals), and reply on LDI to trigger fast protection switch over
upon failure detection in a given LSP.
5.5. Remote Defect Indication
Remote Defect Indication (RDI) function enables an End Point to
report to the other End Point that a fault or defect condition is
detected on the PW, LSP, or Section they are the End Points.
The RDI OAM function is supported by the use of Bidirectional
Forwarding Detection (BFD) Control Packets [cc-cv]. RDI is only used
for bidirectional connections and is associated with proactive CC-V
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activation.
When an end point (MEP) detects a signal failure condition, it sets
the flag up by setting the diagnostic field of the BFD control packet
to a particular value to indicate the failure condition on the
associated PW, LSP, or Section, and transmitting the BFD control
packet with the failure flag up to the other end point (its peer
MEP).
RDI function can be used to facilitate the protection switching by
synchronizing the two end points when unidirectional failure occurs
and is detected by one end.
5.6. Packet Loss and Delay Measurement
The packet loss and delay measurement toolset enables operators to
measure the quality of the packet transmission over a PW, LSP, or
Section.
The loss and delay protocols have the following characteristics and
capabilities:
o Support measurement of packet loss, delay and throughput over
Label Switched Paths (LSPs), pseudowires, and MPLS sections.
o The same LM and DM protocols can be used for both continuous/
proactive and selective/on-demand measurement.
o The LM and DM protocols use a simple query/response model for
bidirectional measurement that allows a single node - the querier
- to measure the loss or delay in both directions.
o The LM and DM protocols use query messages for unidirectional loss
and delay measurement. The measurement can either be carried out
at the downstream node(s) or at the querier if an out-of-band
return path is available.
o The LM and DM protocols do not require that the transmit and
receive interfaces be the same when performing bidirectional
measurement.
o The LM protocol supports both 32-bit and 64-bit counters although
for simplicity only 32-bit packet counters are currently included
in the MPLS-TP profile.
o The LM protocol supports measurement in terms of both packet
counts and octet counts although for simplicity only packet
counters are currently included in the MPLS-TP profile.
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o The LM protocol can be used to measure channel throughput as well
as packet loss.
o The DM protocol supports varying the measurement message size in
order to measure delays associated with different packet sizes.
6. IANA Considerations
This document makes no request of IANA.
The OAM tools and fucntions defined under G-ACh use IANA assigned
code points. the codes are defined in the corresponding IETF RFCs
Note to RFC Editor:
this section may be removed on publication as an RFC.
7. Security Considerations
This document does not by itself raise any particular security
considerations. Security considerations for each function in the OAM
toolset need to be documented in the document that specifies the
particular functionality.
The general security considerations are provided in [MPLS and GMPLS
Security Frwk] and [MPLS-TP Security Frwk].
8. Acknowledgements
The discussion on the needed OAM toolset took place, mainly, in the
MPLS Interoperability Design Team (the MEAD). A toolset was agreed
upon and was reported to the MPLS working group in Stockholm (July
2009) during the IETF (#75) meetings. This was also judged to be the
working group consensus.
The editors wish to thank the MPLS-TP Design Team members, from both
the IETF and ITU-T leadership teams, in formulating the
recommendations documented here. In particular, we would like to
thank Loa Andersson, Huub van Helvoort, and the Area Directors for
their suggestions and enhancements to the text.
9. References
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9.1. Normative References
[LSP Ping]
Kompella, K. and G. Swallow, "Detecting Multi-Protocol
Label Switched (MPLS) Data Plane Failures", RFC 4379,
February 2006.
[PW ACH] Bryant, S., Swallow, G., Martini, L., and D. McPherson,
"Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
Use over an MPLS PSN", RFC 4385, February 2006.
[BASE BFD]
Katz, D. and D. Ward, "Bidirectional Forwarding
Detection", RFC 5880, February 2009.
[MPLS BFD]
Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
"BFD For MPLS LSPs", RFC 5884, June 2008.
[PW VCCV] Nadeau, T. and C. Pignataro, "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007.
[MPLS TP Idents]
Bocci, M., Swallow, G., and E. Gray, "MPLS-TP
Identifiers", RFC 6370, September 2011.
[Pro CC-V]
Allan, D. and G. Swallow, "Proactive Connection
Verification, Continuity Check and Remote Defect
indication for MPLS Transport Profile",
ID draft-ietf-mpls-tp-cc-cv-rdi-06, August 2011.
[Demand CV]
Bahadur, N., Aggarwal, R., Boutros, S., and E. Gray, "MPLS
on-demand Connectivity Verification, Route Tracing and
Adjacency Verification",
ID draft-ietf-mpls-tp-on-demand-cv-06, August 2011.
[MPLS-TP OAM Reqs]
Vigoureux, M., Betts, M., and D. Ward, "Requirements for
OAM in MPLS Transport Networks", RFC 5860, April 2009.
[MPLS-TP OAM Frwk]
Busi, I., Niven-Jenkins, B., and D. Allan, "MPLS-TP OAM
Framework and Overview", RFC 6371, September 2011.
[MPLS-TP Reqs]
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Niven-Jenkins, B., Nadeau, T., and C. Pignataro,
"Requirements for the Transport Profile of MPLS",
RFC 5654, April 2009.
[MPLS G-ACH]
Bocci, M., Bryant, S., and M. Vigoureux, "MPLS Generic
Associated Channel", RFC 5586, June 2009.
[Fault Mng]
Swallow, G., Fulignoli, A., and M. Vigoureux, "MPLS Fault
Management OAM", ID draft-ietf-mpls-tp-fault-07,
September 2011.
[LiLoopback]
Boutros, S., Sivabalan, S., Aggarwal, R., Vigoureux, M.,
and X. Dai, "MPLS Transport Profile Lock Instruct and
Loopback Functions", ID draft-ietf-mpls-tp-li-lb-05,
September 2011.
[MPLS-TP CSF]
He, J., LI, H., and E. Bellagamba, "Indication of Client
Failure in MPLS-TP", ID draft-ietf-mpls-tp-csf-02,
September 2011.
[Loss-Delay]
Frost, D. and S. Bryant, "Packet Loss and Delay
Measurement for MPLS Networks", RFC 6374, September 2011.
[TP-Loss-Delay-Profile]
Frost, D. and S. Bryant, "A Packet Loss and Delay
Measurement Profile for MPLS-based Transport Networks",
RFC 6375, September 2011.
9.2. Informative References
[MPLS-TP Security Frwk]
Fang, L., Niven-Jenkins, B., and S. Mansfield, "MPLS-TP
Security Framework",
ID draft-ietf-mpls-tp-security-framework-01, May 2011.
[MPLS and GMPLS Security Frwk]
Fang, L., "Security Framework for MPLS and GMPLS
Networks", RFC 5920, July 2010.
[Y.1731] International Telecommunications Union - Standardization,
"OAM functions and mechanisms for Ethernet based
networks", ITU Y.1731, May 2006.
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Authors' Addresses
Nurit Sprecher
Nokia Siemens Networks
3 Hanagar St. Neve Ne'eman B
Hod Hasharon, 45241
Israel
Email: nurit.sprecher@nsn.com
Luyuan Fang
Cisco
111 Wood Avenue South
Iselin, NJ 08830
USA
Email: lufang@cisco.com
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