draft-ietf-opsawg-oam-overview-02.txt   draft-ietf-opsawg-oam-overview-03.txt 
Operations and Management Area Working Group T. Mizrahi Operations and Management Area Working Group T. Mizrahi
Internet Draft Marvell Internet Draft Marvell
Intended status: Informational N. Sprecher Intended status: Informational N. Sprecher
Expires: April 2011 Nokia Siemens Networks Expires: July 2011 Nokia Siemens Networks
E. Bellagamba E. Bellagamba
Ericsson Ericsson
Y. Weingarten Y. Weingarten
Nokia Siemens Networks Nokia Siemens Networks
October 7, 2010 January 24, 2011
An Overview of An Overview of
Operations, Administration, and Maintenance (OAM) Mechanisms Operations, Administration, and Maintenance (OAM) Mechanisms
draft-ietf-opsawg-oam-overview-02.txt draft-ietf-opsawg-oam-overview-03.txt
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Abstract Abstract
Operations, Administration, and Maintenance (OAM) is a general term Operations, Administration, and Maintenance (OAM) is a general term
that refers to a toolset that can be used for detecting and reporting that refers to a toolset that can be used for fault detection and
connection failures or measurement of connection performance localization, and for performance measurement. OAM mechanisms have
parameters. OAM mechanisms have been defined for various layers in been defined for various layers in the protocol stack, and are used
the protocol stack, and are used with a variety of protocols. with a variety of protocols.
This document presents an overview of the OAM mechanisms that have This document presents an overview of the OAM mechanisms that have
been defined and are currently being defined by the IETF, as well as been defined and are currently being defined by the IETF, as well as
a comparison to other OAM mechanisms that have been defined by the a comparison to other OAM mechanisms that have been defined by the
IEEE and ITU-T. IEEE and ITU-T.
Table of Contents Table of Contents
1. Introduction................................................4 1. Introduction................................................4
2. Conventions used in this document............................8 2. Conventions used in this document............................8
3. Basic Terminology...........................................8 3. Basic Terminology...........................................8
3.1. Abbreviations..........................................8 3.1. Abbreviations..........................................8
3.2. Terminology used in OAM Standards.......................9 3.2. Terminology used in OAM Standards.......................9
3.2.1. General Terms......................................9 3.2.1. General Terms......................................9
3.2.2. OAM Maintenance Entities and Communication Links...10 3.2.2. OAM Maintenance Entities and Communication Links...10
3.2.3. OAM Maintenance Points............................10 3.2.3. OAM Maintenance Points............................10
3.2.4. Link Failures.....................................11 3.2.4. Connectivity Verification and Continuity Checks....11
3.2.5. Connectivity Verification and Continuity Checks....11 3.2.5. Link Failures.....................................11
3.2.6. Summary of OAM Terms used in the Standards.........11 3.2.6. Summary of OAM Terms used in the Standards.........12
4. OAM Functions..............................................13 4. OAM Functions..............................................13
4.1. ICMP Ping.............................................13 4.1. ICMP Ping.............................................13
4.2. Bidirectional Forwarding Detection (BFD)...............13 4.2. Bidirectional Forwarding Detection (BFD)...............13
4.2.1. Overview.........................................13 4.2.1. Overview.........................................13
4.2.2. BFD Control.......................................13 4.2.2. BFD Control.......................................13
4.2.3. BFD Echo.........................................14 4.2.3. BFD Echo.........................................14
4.3. LSP Ping..............................................14 4.3. LSP Ping..............................................14
4.4. PWE3 Virtual Circuit Connectivity Verification (VCCV)...15 4.4. PWE3 Virtual Circuit Connectivity Verification (VCCV)...15
4.5. IP Performance Metrics (IPPM)..........................15 4.5. IP Performance Metrics (IPPM)..........................16
4.5.1. Overview.........................................15 4.5.1. Overview.........................................16
4.5.2. Control and Test Protocols........................16 4.5.2. Control and Test Protocols........................16
4.5.3. OWAMP............................................16 4.5.3. OWAMP............................................17
4.5.4. TWAMP............................................17 4.5.4. TWAMP............................................17
4.6. ITU-T Y.1711..........................................17 4.6. ITU-T Y.1711..........................................18
4.6.1. Overview.........................................17 4.6.1. Overview.........................................18
4.6.2. Connectivity Verification (CV)....................18 4.6.2. Connectivity Verification (CV)....................18
4.6.3. Fast Failure Detection (FFD)......................18 4.6.3. Fast Failure Detection (FFD)......................19
4.6.4. Forward Defect Indication (FDI)...................18 4.6.4. Forward Defect Indication (FDI)...................19
4.6.5. Backward Defect Indication (BDI)..................19 4.6.5. Backward Defect Indication (BDI)..................19
4.7. ITU-T Y.1731..........................................19 4.7. ITU-T Y.1731..........................................19
4.7.1. Overview.........................................19 4.7.1. Overview.........................................19
4.7.2. ETH-CC...........................................19 4.7.2. ETH-CC...........................................19
4.7.3. ETH-LB...........................................20 4.7.3. ETH-LB...........................................20
4.7.4. ETH-TST..........................................20 4.7.4. ETH-TST..........................................20
4.7.5. ETH-LT...........................................20 4.7.5. ETH-LT...........................................21
4.7.6. ETH-AIS..........................................20 4.7.6. ETH-AIS..........................................21
4.7.7. ETH-LCK..........................................20 4.7.7. ETH-LCK..........................................21
4.7.8. ETH-RDI..........................................21 4.7.8. ETH-RDI..........................................21
4.7.9. ETH-APS..........................................21 4.7.9. ETH-APS..........................................21
4.7.10. ETH-LM..........................................21 4.7.10. ETH-LM..........................................21
4.7.11. ETH-DM..........................................21 4.7.11. ETH-DM..........................................22
4.8. IEEE 802.1ag..........................................22 4.8. IEEE 802.1ag..........................................23
4.8.1. Overview.........................................22 4.8.1. Overview.........................................23
4.8.2. Continuity Check..................................22 4.8.2. Continuity Check..................................23
4.8.3. Loopback.........................................22 4.8.3. Loopback.........................................23
4.8.4. Linktrace........................................23 4.8.4. Linktrace........................................23
4.9. IEEE 802.3ah..........................................23 4.9. IEEE 802.3ah..........................................23
4.9.1. Overview.........................................23 4.9.1. Overview.........................................23
4.9.2. Remote Failure Indication.........................23 4.9.2. Remote Failure Indication.........................23
4.9.3. Remote Loopback...................................23 4.9.3. Remote Loopback...................................24
4.9.4. Link Monitoring...................................23 4.9.4. Link Monitoring...................................24
4.10. MPLS-TP OAM..........................................23 4.10. MPLS-TP OAM..........................................24
4.10.1. Overview........................................23 4.10.1. Overview........................................24
4.10.2. Generic Associated Channel.......................24 4.10.2. Generic Associated Channel.......................25
4.10.3. MPLS-TP OAM Toolset..............................24 4.10.3. MPLS-TP OAM Toolset..............................25
4.10.3.1. Continuity Check and Connectivity Verification25 4.10.3.1. Continuity Check and Connectivity Verification25
4.10.3.2. Diagnostic Tests............................25 4.10.3.2. Diagnostic Tests............................26
4.10.3.3. Route Tracing...............................25 4.10.3.3. Route Tracing...............................26
4.10.3.4. Lock Instruct...............................25 4.10.3.4. Lock Instruct...............................26
4.10.3.5. Lock Reporting..............................26 4.10.3.5. Lock Reporting..............................26
4.10.3.6. Alarm Reporting.............................26 4.10.3.6. Alarm Reporting.............................26
4.10.3.7. Remote Defect Indication....................26 4.10.3.7. Remote Defect Indication....................27
4.10.3.8. Client Failure Indication...................26 4.10.3.8. Client Failure Indication...................27
4.10.3.9. Packet Loss Measurement.....................26 4.10.3.9. Packet Loss Measurement.....................27
4.10.3.10. Packet Delay Measurement...................27 4.10.3.10. Packet Delay Measurement...................27
4.11. Summary of OAM Functions..............................27 4.11. Summary of OAM Functions..............................28
4.12. Summary of Continuity Check Mechanisms................29 4.12. Summary of Continuity Check Mechanisms................29
5. Security Considerations.....................................30 5. Security Considerations.....................................30
6. IANA Considerations........................................30 6. IANA Considerations........................................30
7. Acknowledgments............................................30 7. Acknowledgments............................................30
8. References.................................................30 8. References.................................................31
8.1. Normative References...................................30 8.1. Normative References...................................31
8.2. Informative References.................................32 8.2. Informative References.................................33
1. Introduction 1. Introduction
OAM is a general term that refers to a toolset that can be used for OAM is a general term that refers to a toolset that can be used for
detecting and reporting connection failures or measurement of detecting, isolating and reporting connection failures or measurement
connection performance parameters. The term OAM has been used over of connection performance parameters. The term OAM has been used over
the years in several different contexts, as discussed in [OAM Soup]. the years in several different contexts, as discussed in [OAM Soup].
In the context of this document OAM refers to Operations, In the context of this document OAM refers to Operations,
Administration, and Maintenance, i.e., this document refers to OAM in Administration, and Maintenance, i.e., this document refers to OAM in
the context of monitoring communication links. Other aspects the context of monitoring communication entities, e.g., nodes, paths,
associated with the OAM acronym, such as management, are not physical links, or logical links. Other aspects associated with the
described in this document. OAM acronym, such as management, are outside the scope of this
document.
OAM was originally used in the world of telephony, and has been OAM was originally used in the world of telephony, and has been
adopted in packet based networks. OAM mechanisms are used in various adopted in packet based networks. OAM mechanisms are used in various
layers in the protocol stack, and are applied to a variety of layers in the protocol stack, and are applied to a variety of
different protocols. different protocols.
The IETF has defined OAM for several protocols, and is currently The IETF has defined OAM for several protocols, and is currently
working on defining several new OAM protocols. A summary of these working on defining several new OAM protocols. A summary of these
protocols, old and new, is listed below: protocols, old and new, is listed below:
skipping to change at page 9, line 18 skipping to change at page 9, line 18
LSR Label Switching Router LSR Label Switching Router
MA Maintenance Association MA Maintenance Association
ME Maintenance Entity ME Maintenance Entity
MEG Maintenance Entity Group MEG Maintenance Entity Group
MEP Maintenance End Point MEP Maintenance End Point
MHF MIP Half Function
MIP Maintenance Intermediate Point MIP Maintenance Intermediate Point
MP Maintenance Point MP Maintenance Point
MPLS Multiprotocol Label Switching MPLS Multiprotocol Label Switching
MPLS-TP MPLS Transport Profile MPLS-TP MPLS Transport Profile
OAM Operations, Administration, and Maintenance OAM Operations, Administration, and Maintenance
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some of the OAM related terminology. some of the OAM related terminology.
This section presents a comparison of the terms used in various OAM This section presents a comparison of the terms used in various OAM
standards, without fully quoting the definition of each term. For a standards, without fully quoting the definition of each term. For a
formal definition of each term, refer to the references at the end of formal definition of each term, refer to the references at the end of
this document. The comparison focuses on three basic terms, and is this document. The comparison focuses on three basic terms, and is
summarized in section 3 ..2.6. summarized in section 3 ..2.6.
3.2.2. OAM Maintenance Entities and Communication Links 3.2.2. OAM Maintenance Entities and Communication Links
A Maintenance Entity (ME) can be either a point-to-point or a point- A Maintenance Entity (ME) is a point-to-point relationship between
to-multipoint relationship between two or more Maintenance Points two Maintenance Points (MP). The connectivity between these
(MP). The connectivity between these Maintenance Points is managed Maintenance Points is managed and monitored by the OAM protocol.
and monitored by the OAM protocol.
A pair of MPs engaged in an ME are connected by a communication Link. A pair of MPs engaged in an ME are connected by a communication Link.
Link in this context may refer to a physical connection, or to a The term "Link" in this context is a generic term that may refer to
logical path such as an MPLS LSP. The term Link is used throughout one of several types of connection, e.g. a single physical
this document to refer to the connection between the MPs that is connection, a set of physical connections, or a virtual link such as
monitored by an OAM protocol. an MPLS LSP. The term Link is used throughout this document to refer
to the connection between the MPs that is monitored by an OAM
protocol.
The term Maintenance Entity (ME) is defined in ITU-T standards (e.g. The term Maintenance Entity (ME) is defined in ITU-T standards (e.g.
[ITU-T Y.1731]). Various terms are used to refer to an ME. For [ITU-T Y.1731]). Various terms are used to refer to an ME. For
example, in MPLS terminology, an ME is simply referred to as an LSP. example, in MPLS LSP Ping ([LSP Ping]) terminology, an ME is simply
BFD does not explicitly use a term that is equivalent to ME, but referred to as an LSP. BFD does not explicitly use a term that is
rather uses the term "session", referring to the relationship between equivalent to ME, but rather uses the term "session", referring to
two nodes using a BFD protocol. the relationship between two nodes using a BFD protocol.
MPLS-TP has defined the terms ME and Maintenance Entity Group (MEG) MPLS-TP has defined the terms ME and Maintenance Entity Group (MEG)
in [MPLS-TP OAM FW], similar to the terms defined by ITU-T. in [MPLS-TP OAM FW], similar to the terms defined by ITU-T.
3.2.3. OAM Maintenance Points 3.2.3. OAM Maintenance Points
A Maintenance Point (MP) is a function that is defined at a node in A Maintenance Point (MP) is a functional entity that is defined at a
the network, and either initiates or reacts to OAM messages. A node in the network, and either initiates or reacts to OAM messages.
Maintenance End Point (MEP) is one of the end points of an ME, and A Maintenance End Point (MEP) is one of the end points of an ME, and
can initiate OAM messages and respond to them. A Maintenance can initiate OAM messages and respond to them. A Maintenance
Intermediate Point (MIP) is a point between two MEPs, that is able to Intermediate Point (MIP) is an intermediate point between two MEPs,
respond to OAM frames, but does not initiate them. that does not initiate OAM frames, but is able to respond to OAM
frames that are destined to it, and to forward others.
The terms MEP and MIP are defined in ITU-T standards (e.g. [ITU-T The terms MEP and MIP are defined in ITU-T standards (e.g. [ITU-T
Y.1731]). The term Maintenance Point is a general term for MEPs and Y.1731]). The term Maintenance Point is a general term for MEPs and
MIPs, and is used in [IEEE 802.1ag]. MIPs, and is used in [IEEE 802.1ag].
The 802.1ag defines a finer distinction between Up MPs and Down MPs.
An MP is a bridge interface, that is monitored by an OAM protocol
either in the direction facing the network, or in the direction
facing the bridge. A Down MP is an MP that receives OAM packets from,
and transmits them to the direction of the network. An Up MP receives
OAM packets from, and transmits them to the direction of the bridging
entity.
MPLS-TP has defined the terms MEP and MIP and their functional MPLS-TP has defined the terms MEP and MIP and their functional
characteristics in [MPLS-TP OAM FW], similar to the terms defined by characteristics in [MPLS-TP OAM FW], similar to the terms defined by
ITU-T. ITU-T.
3.2.4. Link Failures 3.2.4. Connectivity Verification and Continuity Checks
The terms Failure, Fault, and Defect are intermittently used in the
standards. In some standards, such as [IEEE 802.1ag], there is no
distinction between these terms, while in other standards each of
these terms refers to a different type of malfunction.
The ITU-T distinguishes between these terms in [ITU-T G.806]. The
term Fault refers to an inability to perform a required action, e.g.,
an unsuccessful attempt to deliver a packet. The term Defect refers
to an interruption in the normal operation, such as a consecutive
period of time where no packets are delivered successfully. The term
Failure refers to the termination of the required function. While a
Defect typically refers to a limited period of time, a failure refers
to a long period of time.
3.2.5. Connectivity Verification and Continuity Checks
Two distinct classes of failure management functions are used in OAM Two distinct classes of failure management functions are used in OAM
protocols, connectivity verification and continuity checks. The protocols, connectivity verification and continuity checks. The
distinction between these terms is defined in [MPLS-TP OAM], and is distinction between these terms is defined in [MPLS-TP OAM], and is
used similarly in this document. used similarly in this document.
Continuity checks are used to verify the liveness of a link, and are Continuity checks are used to verify the liveness of a link, and are
typically sent proactively, though they can be invoked on-demand as typically sent proactively, though they can be invoked on-demand as
well. well.
A connectivity verification function allows an MP to check whether it A connectivity verification function allows an MP to check whether it
is connected to a peer MP or not. A connectivity verification (CV) is connected to a peer MP or not. A connectivity verification (CV)
protocol typically uses a CV message, followed by a CV reply that is protocol typically uses a CV message, followed by a CV reply that is
sent back to the originator. A CV function can be applied proactively sent back to the originator. A CV function can be applied proactively
or on-demand. or on-demand.
Connectivity verification and continuity checks are considered Connectivity verification and continuity checks are considered
complementary mechanisms, and are often used in conjunction with each complementary mechanisms, and are often used in conjunction with each
other. other.
3.2.5. Link Failures
The terms Failure, Fault, and Defect are intermittently used in the
standards, referring to a malfunction that can be detected by a
connectivity or a continuity check. In some standards, such as [IEEE
802.1ag], there is no distinction between these terms, while in other
standards each of these terms refers to a different type of
malfunction.
The ITU-T distinguishes between these terms in [ITU-T G.806]. The
term Fault refers to an inability to perform a required action, e.g.,
an unsuccessful attempt to deliver a packet. The term Defect refers
to an interruption in the normal operation, such as a consecutive
period of time where no packets are delivered successfully. The term
Failure refers to the termination of the required function. While a
Defect typically refers to a limited period of time, a failure refers
to a long period of time.
3.2.6. Summary of OAM Terms used in the Standards 3.2.6. Summary of OAM Terms used in the Standards
Table 2 provides a comparison of the terminology used in different Table 2 provides a comparison of the terminology used in different
OAM standards. OAM standards.
+-----------+-------------+-----------+----------------------------+ +-----------+-------------+-----------+----------------------------+
| |Maintenance |Maintenance|Link Failure Terminology | | |Maintenance |Maintenance|Link Failure Terminology |
| |Point |Entity | | | |Point |Entity | |
| |Terminology |Terminology| | | |Terminology |Terminology| |
+-----------+-------------+-----------+----------------------------+ +-----------+-------------+-----------+----------------------------+
skipping to change at page 12, line 38 skipping to change at page 13, line 5
+ --------- + ----------- + --------- + -------------------------- + + --------- + ----------- + --------- + -------------------------- +
|ITU-T |-MEP | ME |-Fault, Defect, Failure: as | |ITU-T |-MEP | ME |-Fault, Defect, Failure: as |
|Y.1731 |-MIP | | defined in [ITU-T G.806] | |Y.1731 |-MIP | | defined in [ITU-T G.806] |
| | | | | | | | | |
+ --------- + ----------- + --------- + -------------------------- + + --------- + ----------- + --------- + -------------------------- +
|MPLS-TP |-End Point, |-LSP |-Fault, Defect, Failure: as | |MPLS-TP |-End Point, |-LSP |-Fault, Defect, Failure: as |
|OAM | MEP |-PW | defined in [ITU-T G.806] | |OAM | MEP |-PW | defined in [ITU-T G.806] |
| |-Intermediate|-Section | | | |-Intermediate|-Section | |
| | Point, MIP | | | | | Point, MIP | | |
+ --------- + ----------- + --------- + -------------------------- + + --------- + ----------- + --------- + -------------------------- +
|IEEE |-MEP | ME |-Failure | |IEEE |-MP (Down,Up)| ME |-Failure |
|802.1ag |-MIP | |-Fault | |802.1ag | -MEP | |-Fault |
| |-MP | |-Defect | | | -MIP | |-Defect |
| | -MHF | | |
+ --------- + ----------- + --------- + -------------------------- + + --------- + ----------- + --------- + -------------------------- +
|IEEE | DTE | Link |-Failure | |IEEE | DTE | Link |-Failure |
|802.3ah | | |-Fault | |802.3ah | | |-Fault |
+-----------+-------------+-----------+----------------------------+ +-----------+-------------+-----------+----------------------------+
Table 2 Summary of OAM Terms Table 2 Summary of OAM Terms
4. OAM Functions 4. OAM Functions
4.1. ICMP Ping 4.1. ICMP Ping
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Class (FEC) and also Maximum Transmission Unit (MTU) problems. The Class (FEC) and also Maximum Transmission Unit (MTU) problems. The
traceroute functionality may be used to isolate and localize the MPLS traceroute functionality may be used to isolate and localize the MPLS
faults, using the Time-to-live (TTL) indicator to incrementally faults, using the Time-to-live (TTL) indicator to incrementally
identify the sub-path of the LSP that is successfully traversed identify the sub-path of the LSP that is successfully traversed
before the faulty link or node. before the faulty link or node.
It should be noted that LSP Ping does support unique identification It should be noted that LSP Ping does support unique identification
of the LSP within an addressing domain. The identification is checked of the LSP within an addressing domain. The identification is checked
using the full FEC identification. LSP Ping is easily extensible to using the full FEC identification. LSP Ping is easily extensible to
include additional information needed to support new functionality, include additional information needed to support new functionality,
by use of Type-Length-Value (TLV) constructs. by use of Type-Length-Value (TLV) constructs. The usage of TLVs is
typically not easy to perform in hardware, and is thus typically
handled by the control plane.
LSP Ping supports both asynchronous, as well as, on-demand LSP Ping supports both asynchronous, as well as, on-demand
activation. In addition, extensions for LSP Ping are being defined activation. In addition, extensions for LSP Ping are being defined
for point-to-multipoint LSPs in [P2MP LSP Ping] and for MPLS Tunnels for point-to-multipoint LSPs in [P2MP LSP Ping] and for MPLS Tunnels
in [MPLS LSP Ping]. in [MPLS LSP Ping].
4.4. PWE3 Virtual Circuit Connectivity Verification (VCCV) 4.4. PWE3 Virtual Circuit Connectivity Verification (VCCV)
VCCV, as defined in [VCCV], provides end-to-end fault detection VCCV, as defined in [VCCV], provides end-to-end fault detection
and diagnostics for PWs (regardless of the underlying tunneling and diagnostics for PWs (regardless of the underlying tunneling
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The CV function is used to detect connectivity defects in an LSP. CV The CV function is used to detect connectivity defects in an LSP. CV
frames are sent proactively at a rate of 1 per second. Each frame frames are sent proactively at a rate of 1 per second. Each frame
contains the Trail-Termination Source Identifier (TTSI), indicating contains the Trail-Termination Source Identifier (TTSI), indicating
the identity of the transmitting LSR. the identity of the transmitting LSR.
The CV function can detect any of the following defect conditions. The CV function can detect any of the following defect conditions.
o Loss of Connectivity Verification (LOCV): A loss of connectivity o Loss of Connectivity Verification (LOCV): A loss of connectivity
is detected when no CV OAM packets are received in a period of 3 is detected when no CV OAM packets are received in a period of 3
consecutive transmission periods. consecutive transmission periods.
It should be noted that the LOCV defect is in fact loss of
continuity when using the terminology defined in 3 ..2.4.
o TTSI Mismatch: A TTSI mismatch is detected when a CV frame with an o TTSI Mismatch: A TTSI mismatch is detected when a CV frame with an
unexpected TTSI is received. unexpected TTSI is received.
o TTSI Mismerge: A TTSI mismerge is detected when the CV frames o TTSI Mismerge: A TTSI mismerge is detected when the CV frames
received in a given LSP contain some frame with an expected TTSI, received in a given LSP contain some frame with an expected TTSI,
and some frames with an unexpected TTSI. and some frames with an unexpected TTSI.
o Excess: An excess is detected when at least 5 CV frames are o Excess: An excess is detected when at least 5 CV frames are
received during a period of 3 consecutive transmission periods. received during a period of 3 consecutive transmission periods.
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failure detection and reporting, protection switching mechanisms failure detection and reporting, protection switching mechanisms
typically require faster detection. FFD is very similar to CV in typically require faster detection. FFD is very similar to CV in
terms of the packet format, and the possible defect conditions, but terms of the packet format, and the possible defect conditions, but
FFD allows a configurable transmission frequency. The default FFD allows a configurable transmission frequency. The default
transmission rate of FFD frames is 20 per second, i.e., every 50 ms, transmission rate of FFD frames is 20 per second, i.e., every 50 ms,
allowing fast detection for protection switching applications. allowing fast detection for protection switching applications.
4.6.4. Forward Defect Indication (FDI) 4.6.4. Forward Defect Indication (FDI)
The FDI function is used by an LSR to report a defect to affected The FDI function is used by an LSR to report a defect to affected
client layers, allowing them to suppress alarms about this defect. An client layers, allowing them to suppress alarms about this defect.
In MPLS-TP OAM this function is referred to as Client Failure
Indication.
FDI packets are sent at a rate of 1 per second. FDI packets are sent at a rate of 1 per second.
4.6.5. Backward Defect Indication (BDI) 4.6.5. Backward Defect Indication (BDI)
The BDI function is used to inform the LSR at an LSP trail The BDI function is used by an LSR to inform a peer LSR about a
termination source point about a defect condition in the forward defect condition on an LSP for which they are the end points of.
direction of an LSP. The LSR at the LSP trail termination sink point In MPLS-TP OAM this function is referred to as Remote Defect
transmits the BDI to the upstream LSR through the return path. BDI Indication.
packets are sent at the same transmission rate as FDI.
BDI packets are sent at the same transmission rate as FDI.
4.7. ITU-T Y.1731 4.7. ITU-T Y.1731
4.7.1. Overview 4.7.1. Overview
The [ITU-T Y.1731] defines a protocol for Ethernet OAM. It is The [ITU-T Y.1731] defines a protocol for Ethernet OAM. It is
presented in this document as a reference point. Y.1731 defines presented in this document as a reference point. Y.1731 defines
various OAM functions, including continuity and connectivity various OAM functions, including continuity and connectivity
verification, and functions for performance monitoring. verification, and functions for performance monitoring.
4.7.2. ETH-CC 4.7.2. ETH-CC
The Ethernet Continuity Check function is a proactive function that The Ethernet Continuity Check function is a proactive function that
allows a MEP to detect loss of continuity with any of the other MEPs allows a MEP to detect loss of continuity with any of the other MEPs
in the MEG. This function also allows detection of other defect in the MEG. This function also allows detection of other defect
conditions, such as unintended connectivity between two MEGs. The conditions, such as unintended connectivity between two MEGs (also
ETH-CC function is used for one of three possible applications: fault known as a mismerge). The ETH-CC function is used for one of three
management, performance monitoring (see 4.6.10.), and protection possible applications: fault management, performance monitoring (see
switching. 4.6.10.), and protection switching.
Continuity Check Messages (CCM) are transmitted periodically at a Continuity Check Messages (CCM) are transmitted periodically at a
constant rate. There are 7 possible transmission periods, from 3.33 constant rate. There are 7 possible transmission periods, from 3.33
ms to 10 min. When the ETH-CC function detects a defect, it reports ms to 10 min. When the ETH-CC function detects a defect, it reports
one of the following defect conditions: one of the following defect conditions:
o Loss of continuity (LOC): Occurs when at least when no CCM o Loss of continuity (LOC): Occurs when at least when no CCM
messages have been received from a peer MEP during a period of 3.5 messages have been received from a peer MEP during a period of 3.5
times the configured transmission period. times the configured transmission period.
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See 4.6.3. See 4.6.3.
4.8.4. Linktrace 4.8.4. Linktrace
See 4.6.5. See 4.6.5.
4.9. IEEE 802.3ah 4.9. IEEE 802.3ah
4.9.1. Overview 4.9.1. Overview
The [IEEE 802.3ah] defines an Ethernet link-layer OAM, for single-hop The [IEEE 802.3ah] defines Ethernet for the Last Mile (EFM). With
Ethernet links. The OAM functions in this standard are described respect to OAM, this standard was designed as an Ethernet link-layer
below. OAM, for single-hop Ethernet links, allowing to monitor remote
networking devices that are not managed by a centralized management
system. The OAM functions in this standard are described below.
4.9.2. Remote Failure Indication 4.9.2. Remote Failure Indication
This function allows a node to notify a peer about a defect in the This function allows a node to notify a peer about a defect in the
receive path. Some physical interfaces allow unidirectional traffic, receive path. Some physical interfaces allow unidirectional traffic,
where even if one direction of the link fails, the reverse direction where even if one direction of the link fails, the reverse direction
can still be used to convey the remote failure indication. can still be used to convey the remote failure indication.
4.9.3. Remote Loopback 4.9.3. Remote Loopback
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