draft-ietf-mpls-tp-oam-framework-09.txt   draft-ietf-mpls-tp-oam-framework-10.txt 
MPLS Working Group I. Busi (Ed) MPLS Working Group I. Busi (Ed)
Internet Draft Alcatel-Lucent Internet Draft Alcatel-Lucent
Intended status: Informational D. Allan (Ed) Intended status: Informational D. Allan (Ed)
Ericsson Ericsson
Expires: April 7, 2011 October 7, 2010 Expires: June 16, 2011 December 16, 2010
Operations, Administration and Maintenance Framework for MPLS- Operations, Administration and Maintenance Framework for MPLS-
based Transport Networks based Transport Networks
draft-ietf-mpls-tp-oam-framework-09.txt draft-ietf-mpls-tp-oam-framework-10.txt
Abstract Abstract
The Transport Profile of Multi-Protocol Label Switching The Transport Profile of Multi-Protocol Label Switching
(MPLS-TP) is a packet-based transport technology based on the (MPLS-TP) is a packet-based transport technology based on the
MPLS Traffic Engineering (MPLS-TE) and Pseudowire (PW) data MPLS Traffic Engineering (MPLS-TE) and Pseudowire (PW) data
plane architectures. plane architectures.
This document describes a framework to support a comprehensive This document describes a framework to support a comprehensive
set of Operations, Administration and Maintenance (OAM) set of Operations, Administration and Maintenance (OAM)
skipping to change at page 2, line 11 skipping to change at page 2, line 11
documents at any time. It is inappropriate to use Internet- documents at any time. It is inappropriate to use Internet-
Drafts as reference material or to cite them other than as "work Drafts as reference material or to cite them other than as "work
in progress". in progress".
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on April 7, 2011. This Internet-Draft will expire on June 16, 2011.
Copyright Notice Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction..................................................5 1. Introduction..................................................5
1.1. Contributing Authors.....................................6 1.1. Contributing Authors.....................................6
2. Conventions used in this document.............................6 2. Conventions used in this document.............................7
2.1. Terminology..............................................6 2.1. Terminology..............................................7
2.2. Definitions..............................................7 2.2. Definitions..............................................8
3. Functional Components........................................10 3. Functional Components........................................12
3.1. Maintenance Entity and Maintenance Entity Group.........10 3.1. Maintenance Entity and Maintenance Entity Group.........12
3.2. Nested MEGs: SPMEs and Tandem Connection Monitoring.....12 3.2. Nested MEGs: SPMEs and Tandem Connection Monitoring.....14
3.3. MEG End Points (MEPs)...................................14 3.3. MEG End Points (MEPs)...................................16
3.4. MEG Intermediate Points (MIPs)..........................17 3.4. MEG Intermediate Points (MIPs)..........................19
3.5. Server MEPs.............................................18 3.5. Server MEPs.............................................21
3.6. Configuration Considerations............................19 3.6. Configuration Considerations............................22
3.7. P2MP considerations.....................................20 3.7. P2MP considerations.....................................22
3.8. Further considerations of enhanced segment monitoring...21 3.8. Further considerations of enhanced segment monitoring...23
4. Reference Model..............................................21 4. Reference Model..............................................25
4.1. MPLS-TP Section Monitoring (SME)........................23 4.1. MPLS-TP Section Monitoring (SMEG).......................27
4.2. MPLS-TP LSP End-to-End Monitoring (LME).................24 4.2. MPLS-TP LSP End-to-End Monitoring Group (LMEG)..........28
4.3. MPLS-TP PW Monitoring (PME).............................25 4.3. MPLS-TP PW Monitoring (PMEG)............................28
4.4. MPLS-TP LSP SPME Monitoring (LSME)......................25 4.4. MPLS-TP LSP SPME Monitoring (LSMEG).....................29
4.5. MPLS-TP MS-PW SPME Monitoring (PSME)....................27 4.5. MPLS-TP MS-PW SPME Monitoring (PSMEG)...................30
4.6. Fate sharing considerations for multilink...............28 4.6. Fate sharing considerations for multilink...............32
5. OAM Functions for proactive monitoring.......................29 5. OAM Functions for proactive monitoring.......................32
5.1. Continuity Check and Connectivity Verification..........30 5.1. Continuity Check and Connectivity Verification..........33
5.1.1. Defects identified by CC-V.........................32 5.1.1. Defects identified by CC-V.........................36
5.1.2. Consequent action..................................34 5.1.2. Consequent action..................................37
5.1.3. Configuration considerations.......................35 5.1.3. Configuration considerations.......................38
5.2. Remote Defect Indication................................36 5.2. Remote Defect Indication................................40
5.2.1. Configuration considerations.......................37 5.2.1. Configuration considerations.......................40
5.3. Alarm Reporting.........................................37 5.3. Alarm Reporting.........................................41
5.4. Lock Reporting..........................................39 5.4. Lock Reporting..........................................42
5.5. Packet Loss Measurement.................................40 5.5. Packet Loss Measurement.................................44
5.5.1. Configuration considerations.......................41 5.5.1. Configuration considerations.......................45
5.5.2. Sampling skew......................................41 5.5.2. Sampling skew......................................45
5.5.3. Multilink issues...................................41 5.5.3. Multilink issues...................................45
5.6. Packet Delay Measurement................................42 5.6. Packet Delay Measurement................................46
5.6.1. Configuration considerations.......................42 5.6.1. Configuration considerations.......................46
5.7. Client Failure Indication...............................42 5.7. Client Failure Indication...............................47
5.7.1. Configuration considerations.......................43 5.7.1. Configuration considerations.......................47
6. OAM Functions for on-demand monitoring.......................43 6. OAM Functions for on-demand monitoring.......................48
6.1. Connectivity Verification...............................44 6.1. Connectivity Verification...............................48
6.1.1. Configuration considerations.......................45 6.1.1. Configuration considerations.......................49
6.2. Packet Loss Measurement.................................45 6.2. Packet Loss Measurement.................................50
6.2.1. Configuration considerations.......................46 6.2.1. Configuration considerations.......................50
6.2.2. Sampling skew......................................46 6.2.2. Sampling skew......................................51
6.2.3. Multilink issues...................................46 6.2.3. Multilink issues...................................51
6.3. Diagnostic Tests........................................47 6.3. Diagnostic Tests........................................51
6.3.1. Throughput Estimation.............................47 6.3.1. Throughput Estimation.............................51
6.3.2. Data plane Loopback...............................48 6.3.2. Data plane Loopback...............................52
6.4. Route Tracing..........................................49 6.4. Route Tracing..........................................54
6.4.1. Configuration considerations......................50 6.4.1. Configuration considerations......................54
6.5. Packet Delay Measurement...............................50 6.5. Packet Delay Measurement...............................54
6.5.1. Configuration considerations......................51 6.5.1. Configuration considerations......................55
7. OAM Functions for administration control....................51 7. OAM Functions for administration control....................55
7.1. Lock Instruct..........................................51 7.1. Lock Instruct..........................................55
7.1.1. Locking a transport path..........................51 7.1.1. Locking a transport path..........................56
7.1.2. Unlocking a transport path........................52 7.1.2. Unlocking a transport path........................56
8. Security Considerations.....................................52 8. Security Considerations.....................................57
9. IANA Considerations.........................................53 9. IANA Considerations.........................................58
10. Acknowledgments............................................53 10. Acknowledgments............................................58
11. References.................................................54 11. References.................................................59
11.1. Normative References..................................54 11.1. Normative References..................................59
11.2. Informative References................................55 11.2. Informative References................................60
Editors' Note: Editors' Note:
This Informational Internet-Draft is aimed at achieving IETF This Informational Internet-Draft is aimed at achieving IETF
Consensus before publication as an RFC and will be subject to an Consensus before publication as an RFC and will be subject to an
IETF Last Call. IETF Last Call.
[RFC Editor, please remove this note before publication as an [RFC Editor, please remove this note before publication as an
RFC and insert the correct Streams Boilerplate to indicate that RFC and insert the correct Streams Boilerplate to indicate that
the published RFC has IETF Consensus.] the published RFC has IETF Consensus.]
skipping to change at page 5, line 31 skipping to change at page 5, line 31
[2] and RFC 5659 [4]. [2] and RFC 5659 [4].
MPLS-TP supports a comprehensive set of Operations, MPLS-TP supports a comprehensive set of Operations,
Administration and Maintenance (OAM) procedures for fault, Administration and Maintenance (OAM) procedures for fault,
performance and protection-switching management that do not rely performance and protection-switching management that do not rely
on the presence of a control plane. on the presence of a control plane.
In line with [14], existing MPLS OAM mechanisms will be used In line with [14], existing MPLS OAM mechanisms will be used
wherever possible and extensions or new OAM mechanisms will be wherever possible and extensions or new OAM mechanisms will be
defined only where existing mechanisms are not sufficient to defined only where existing mechanisms are not sufficient to
meet the requirements. Extensions do not deprecate support for meet the requirements. Some extensions discussed in this
framework may end up as aspirational capabilities and may be
determined to be not tractably realizable in some
implementations. Extensions do not deprecate support for
existing MPLS OAM capabilities. existing MPLS OAM capabilities.
The MPLS-TP OAM framework defined in this document provides a The MPLS-TP OAM framework defined in this document provides a
comprehensive set of OAM procedures that satisfy the MPLS-TP OAM protocol neutral description of the required OAM functions and
requirements of RFC 5860 [11]. In this regard, it defines of the data plane OAM architecture to support a comprehensive
similar OAM functionality as for existing SONET/SDH and OTN OAM set of OAM procedures that satisfy the MPLS-TP OAM requirements
mechanisms (e.g. [18]). of RFC 5860 [11]. In this regard, it defines similar OAM
functionality as for existing SONET/SDH and OTN OAM mechanisms
(e.g. [18]).
The MPLS-TP OAM framework is applicable to sections, LSPs and The MPLS-TP OAM framework is applicable to sections, Label
(MS-)PWs and supports co-routed and associated bidirectional p2p Switched Paths (LSPs), Multi-Segment Pseudowires (MS-)PWs and
transport paths as well as unidirectional p2p and p2mp transport Sub Path Maintenance Entities (SPMEs). It supports co-routed and
paths. associated bidirectional p2p transport paths as well as
unidirectional p2p and p2mp transport paths.
OAM packets that instrument a particular direction of a
transport path are subject to the same forwarding treatment
(i.e. fate share) as the data traffic and in some cases, where
Explicitly TC-encoded-PSC LSPs (E-LSPs) are employed, may be
required to have common Per-hop Behavior (PHB) scheduling class
(PSC) E2E with the class of traffic monitored. In case of
Label-Only-Inferred-PSC LSP (L-LSP), only one class of traffic
needs to be monitored and therefore the OAM packets have common
PSC with the monitored traffic class.
OAM packets can be distinguished from the data traffic using the
GAL and ACH constructs of RFC 5586 [7] for LSP, SPME and Section
or the ACH construct of RFC 5085 [3]and RFC 5586 [7] for
(MS-)PW.
This framework makes certain assumptions as to the utility and
frequency of different classes of measurement that naturally
suggest different functions are implemented as distinct OAM
flows or messages. This is dictated by the combination of the
class of problem being detected and the need for timeliness of
network response to the problem. For example fault detection is
expected to operate on an entirely different time base than
performance monitoring which is also expected to operate on an
entirely different time base than in band management
transactions.
Section 3 describes the functional component that generates and
processes OAM packets.
Section 4 describes the reference models for applying OAM
functions to Sections, LSP, MS-PW and their SPMEs.
Sections 5, 6 and 7 provide a protocol-neutral description of
the OAM functions, defined in RFC 5860 [11], aimed at clarifying
how the OAM protocol solutions will behave to achieve their
functional objectives.
This document is a product of a joint Internet Engineering Task This document is a product of a joint Internet Engineering Task
Force (IETF) / International Telecommunication Union Force (IETF) / International Telecommunication Union
Telecommunication Standardization Sector (ITU-T) effort to Telecommunication Standardization Sector (ITU-T) effort to
include an MPLS Transport Profile within the IETF MPLS and PWE3 include an MPLS Transport Profile within the IETF MPLS and PWE3
architectures to support the capabilities and functionalities of architectures to support the capabilities and functionalities of
a packet transport network as defined by the ITU-T. a packet transport network as defined by the ITU-T.
1.1. Contributing Authors 1.1. Contributing Authors
Dave Allan, Italo Busi, Ben Niven-Jenkins, Annamaria Fulignoli, Dave Allan, Italo Busi, Ben Niven-Jenkins, Annamaria Fulignoli,
Enrique Hernandez-Valencia, Lieven Levrau, Vincenzo Sestito, Enrique Hernandez-Valencia, Lieven Levrau, Vincenzo Sestito,
Nurit Sprecher, Huub van Helvoort, Martin Vigoureux, Yaacov Nurit Sprecher, Huub van Helvoort, Martin Vigoureux, Yaacov
Weingarten, Rolf Winter Weingarten, Rolf Winter
2. Conventions used in this document 2. Conventions used in this document
2.1. Terminology 2.1. Terminology
AC Attachment Circuit AC Attachment Circuit
AIS Alarm indication signal AIS Alarm indication signal
CV Connectivity Verification CC Continuity Check
DBN Domain Border Node CC-V Continuity Check and Connectivity Verification
LER Label Edge Router CV Connectivity Verification
LKR Lock Report DBN Domain Border Node
LM Loss Measurement E-LSP Explicitly TC-encoded-PSC LSP
LME LSP Maintenance Entity ICC ITU Carrier Code
LMEG LSP ME Group LER Label Edge Router
LSP Label Switched Path LKR Lock Report
LSR Label Switching Router L-LSP Label-Only-Inferred-PSC LSP
LSME LSP SPME ME LM Loss Measurement
LME LSP Maintenance Entity
LMEG LSP ME Group
LSP Label Switched Path
LSR Label Switching Router
LSME LSP SPME ME
LSMEG LSP SPME ME Group LSMEG LSP SPME ME Group
ME Maintenance Entity ME Maintenance Entity
MEG Maintenance Entity Group MEG Maintenance Entity Group
MEP Maintenance Entity Group End Point MEP Maintenance Entity Group End Point
MIP Maintenance Entity Group Intermediate Point MIP Maintenance Entity Group Intermediate Point
NMS Network Management System
PHB Per-hop Behavior PE Provider Edge
PM Performance Monitoring PHB Per-hop Behavior
PME PW Maintenance Entity
PMEG PW ME Group PM Performance Monitoring
PSME PW SPME ME PME PW Maintenance Entity
PMEG PW ME Group
PSC PHB Scheduling Class
PSME PW SPME ME
PSMEG PW SPME ME Group PSMEG PW SPME ME Group
PW Pseudowire PW Pseudowire
SLA Service Level Agreement SLA Service Level Agreement
SME Section Maintenance Entity Group SME Section Maintenance Entity
SPME Sub-path Maintenance Element SMEG Section ME Group
SPME Sub-path Maintenance Element
S-PE Switching Provider Edge
TC Traffic Class
T-PE Terminating Provider Edge
2.2. Definitions 2.2. Definitions
This document uses the terms defined in RFC 5654 [5]. This document uses the terms defined in RFC 5654 [5].
This document uses the term 'Per-hop Behavior' as defined in RFC This document uses the term 'Per-hop Behavior' as defined in RFC
2474 [15]. 2474 [15].
This document uses the term LSP to indicate either a service LSP This document uses the term LSP to indicate either a service LSP
or a transport LSP (as defined in RFC 5921 [8]). or a transport LSP (as defined in RFC 5921 [8]).
This document uses the term Sub Path Maintenance Entity (SPME) This document uses the term Sub Path Maintenance Element (SPME)
as defined in RFC 5921 [8]. as defined in RFC 5921 [8].
Where appropriate, the following definitions are aligned with Where appropriate, the following definitions are aligned with
ITU-T recommendation Y.1731 [20] in order to have a common, ITU-T recommendation Y.1731 [20] in order to have a common,
unambiguous terminology. They do not however intend to imply a unambiguous terminology. They do not however intend to imply a
certain implementation but rather serve as a framework to certain implementation but rather serve as a framework to
describe the necessary OAM functions for MPLS-TP. describe the necessary OAM functions for MPLS-TP.
Adaptation function: The adaptation function is the interface Adaptation function: The adaptation function is the interface
between the client (sub)-layer and the server (sub-)layer. between the client (sub)-layer and the server (sub-)layer.
Branch Node: A node along a point-to-multipoint transport path
that is connected to more than one downstream node.
Bud Node: A node along a point-to-multipoint transport path that
is at the same time a branch node and a leaf node for this
transport path.
Data plane loopback: An out-of-service test where a transport Data plane loopback: An out-of-service test where a transport
path at either an intermediate or terminating node is placed path at either an intermediate or terminating node is placed
into a data plane loopback state, such that all traffic into a data plane loopback state, such that all traffic
(including both payload and OAM) received on the looped back (including both payload and OAM) received on the looped back
interface is sent on the reverse direction of the transport interface is sent on the reverse direction of the transport
path. path.
Note - The only way to send an OAM packet to a node that has been put Note - The only way to send an OAM packet to a node that has been put
into data plane loopback mode is via TTL expiry, irrespective of into data plane loopback mode is via TTL expiry, irrespective of
whether the node is hosting MIPs or MEPs. whether the node is hosting MIPs or MEPs.
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node may be present on the edge of two domains or may be node may be present on the edge of two domains or may be
connected by a link to the DBN at the edge of another OAM connected by a link to the DBN at the edge of another OAM
domain. domain.
Down MEP: A MEP that receives OAM packets from, and transmits Down MEP: A MEP that receives OAM packets from, and transmits
them towards, the direction of a server layer. them towards, the direction of a server layer.
In-Service: The administrative status of a transport path when In-Service: The administrative status of a transport path when
it is unlocked. it is unlocked.
Interface: An interface is the attachment point to a server
(sub-)layer e.g., MPLS-TP section or MPLS-TP tunnel.
Intermediate Node: An intermediate node transits traffic for an Intermediate Node: An intermediate node transits traffic for an
LSP or a PW. An intermediate node may originate OAM flows LSP or a PW. An intermediate node may originate OAM flows
directed to downstream intermediate nodes or MEPs. directed to downstream intermediate nodes or MEPs.
Loopback: See data plane loopback and OAM loopback definitions. Loopback: See data plane loopback and OAM loopback definitions.
Maintenance Entity (ME): Some portion of a transport path that Maintenance Entity (ME): Some portion of a transport path that
requires management bounded by two points (called MEPs), and the requires management bounded by two points (called MEPs), and the
relationship between those points to which maintenance and relationship between those points to which maintenance and
monitoring operations apply (details in section 3.1). monitoring operations apply (details in section 3.1).
Maintenance Entity Group (MEG): The set of one or more Maintenance Entity Group (MEG): The set of one or more
maintenance entities that maintain and monitor a section or a maintenance entities that maintain and monitor a section or a
transport path in an OAM domain. transport path in an OAM domain.
MEP: A MEG end point (MEP) is capable of initiating (MEP Source) MEP: A MEG end point (MEP) is capable of initiating (Source MEP)
and terminating (MEP Sink) OAM messages for fault management and and terminating (sink MEP) OAM messages for fault management and
performance monitoring. MEPs define the boundaries of an ME performance monitoring. MEPs define the boundaries of an ME
(details in section 3.3). (details in section 3.3).
MEP Source: A MEP acts as MEP source for an OAM message when it
originates and inserts the message into the transport path for
its associated MEG.
MEP Sink: A MEP acts as a MEP sink for an OAM message when it
terminates and processes the messages received from its
associated MEG.
MIP: A MEG intermediate point (MIP) terminates and processes OAM MIP: A MEG intermediate point (MIP) terminates and processes OAM
messages that are sent to this particular MIP and may generate messages that are sent to this particular MIP and may generate
OAM messages in reaction to received OAM messages. It never OAM messages in reaction to received OAM messages. It never
generates unsolicited OAM messages itself. A MIP resides within generates unsolicited OAM messages itself. A MIP resides within
a MEG between MEPs (details in section 3.3). a MEG between MEPs (details in section 3.3).
MPLS-TP Section: As defined in [8], it is a link that can be MPLS-TP Section: As defined in [8], it is a link that can be
traversed by one or more MPLS-TP LSPs. traversed by one or more MPLS-TP LSPs.
OAM domain: A domain, as defined in [5], whose entities are OAM domain: A domain, as defined in [5], whose entities are
grouped for the purpose of keeping the OAM confined within that grouped for the purpose of keeping the OAM confined within that
domain. An OAM domain contains zero or more MEGs. domain. An OAM domain contains zero or more MEGs.
Note - within the rest of this document the term "domain" is Note - within the rest of this document the term "domain" is
used to indicate an "OAM domain" used to indicate an "OAM domain"
OAM flow: Is the set of all OAM messages originating with a OAM flow: Is the set of all OAM messages originating with a
specific MEP source that instrument one direction of a MEG (or specific source MEP that instrument one direction of a MEG (or
possibly both in the special case of dataplane loopback). possibly both in the special case of dataplane loopback).
OAM information element: An atomic piece of information OAM information element: An atomic piece of information
exchanged between MEPs and/or MIPs in MEG used by an OAM exchanged between MEPs and/or MIPs in MEG used by an OAM
application. application.
OAM loopback: The capability of a node to be directed by a OAM loopback: The capability of a node to be directed by a
received OAM message to generate a reply back to the sender. OAM received OAM message to generate a reply back to the sender. OAM
loopback can work in-service and can support different OAM loopback can work in-service and can support different OAM
functions (e.g., bidirectional on-demand connectivity functions (e.g., bidirectional on-demand connectivity
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OAM loopback: The capability of a node to be directed by a OAM loopback: The capability of a node to be directed by a
received OAM message to generate a reply back to the sender. OAM received OAM message to generate a reply back to the sender. OAM
loopback can work in-service and can support different OAM loopback can work in-service and can support different OAM
functions (e.g., bidirectional on-demand connectivity functions (e.g., bidirectional on-demand connectivity
verification). verification).
OAM Message: One or more OAM information elements that when OAM Message: One or more OAM information elements that when
exchanged between MEPs or between MEPs and MIPs performs some exchanged between MEPs or between MEPs and MIPs performs some
OAM functionality (e.g. connectivity verification) OAM functionality (e.g. connectivity verification)
OAM Packet: A packet that carries one or more OAM messages (i.e. OAM Packet: A packet that carries one or more OAM messages (i.e.
OAM information elements). OAM information elements).
Originating MEP: A MEP that originates an OAM transaction
message (toward a target MIP/MEP) and expects a reply, either
in-band or out-of-band, from that target MIP/MEP. The
originating source MEP function always generates the OAM request
packets in-band while the originating sink MEP function expects
and processes only OAM reply packets that are sent in-band by
the target MIP/MEP.
Out-of-Service: The administrative status of a transport path Out-of-Service: The administrative status of a transport path
when it is locked. When a path is in a locked condition, it is when it is locked. When a path is in a locked condition, it is
blocked from carrying client traffic. blocked from carrying client traffic.
Path Segment: It is either a segment or a concatenated segment, Path Segment: It is either a segment or a concatenated segment,
as defined in RFC 5654 [5]. as defined in RFC 5654 [5].
Signal Degrade: A condition declared by a MEP when the data Signal Degrade: A condition declared by a MEP when the data
forwarding capability associated with a transport path has forwarding capability associated with a transport path has
deteriorated, as determined by performance monitoring (PM). See also deteriorated, as determined by performance monitoring (PM). See also
ITU-T recommendation G.806 [13]. ITU-T recommendation G.806 [13].
Signal Fail: A condition declared by a MEP when the data Signal Fail: A condition declared by a MEP when the data
forwarding capability associated with a transport path has forwarding capability associated with a transport path has
failed, e.g. loss of continuity. See also ITU-T recommendation failed, e.g. loss of continuity. See also ITU-T recommendation
G.806 [13]. G.806 [13].
Sink MEP: A MEP acts as a sink MEP for an OAM message when it
terminates and processes the messages received from its
associated MEG.
Source MEP: A MEP acts as source MEP for an OAM message when it
originates and inserts the message into the transport path for
its associated MEG.
Tandem Connection: A tandem connection is an arbitrary part of a Tandem Connection: A tandem connection is an arbitrary part of a
transport path that can be monitored (via OAM) independent of transport path that can be monitored (via OAM) independent of
the end-to-end monitoring (OAM). The tandem connection may also the end-to-end monitoring (OAM). The tandem connection may also
include the forwarding engine(s) of the node(s) at the include the forwarding engine(s) of the node(s) at the
boundaries of the tandem connection. Tandem connections may be boundaries of the tandem connection. Tandem connections may be
nested but cannot overlap. See also ITU-T recommendation G.805 nested but cannot overlap. See also ITU-T recommendation G.805
[19]. [19].
Target MEP/MIP: A MEP or a MIP that is targeted by OAM
transaction messages and that replies to the originating MEP
that initiated the OAM transactions. The Target MEP or MIP can
reply either in-band or out-of-band. The target sink MEP
function always receives the OAM request packets in-band while
the target source MEP function only generates the OAM reply
packets that are sent in-band.
Up MEP: A MEP that transmits OAM packets towards, and receives Up MEP: A MEP that transmits OAM packets towards, and receives
them from, the direction of the forwarding engine. them from, the direction of the forwarding engine.
3. Functional Components 3. Functional Components
MPLS-TP is a packet-based transport technology based on the MPLS MPLS-TP is a packet-based transport technology based on the MPLS
and PW data plane architectures ([1], [2] and [4]) and is and PW data plane architectures ([1], [2] and [4]) and is
capable of transporting service traffic where the capable of transporting service traffic where the
characteristics of information transfer between the transport characteristics of information transfer between the transport
path endpoints can be demonstrated to comply with certain path endpoints can be demonstrated to comply with certain
performance and quality guarantees. performance and quality guarantees.
In order to describe the required OAM functionality, this In order to describe the required OAM functionality, this
document introduces a set of functional components. document introduces a set of functional components.
3.1. Maintenance Entity and Maintenance Entity Group 3.1. Maintenance Entity and Maintenance Entity Group
MPLS-TP OAM operates in the context of Maintenance Entities MPLS-TP OAM operates in the context of Maintenance Entities
(MEs) that define a relationship between two points of a (MEs) that define a relationship between two points of a
transport path to which maintenance and monitoring operations transport path to which maintenance and monitoring operations
apply. The collection of one or more MEs that belongs to the apply. The two points that define a maintenance entity are
same transport path and that are maintained and monitored as a called Maintenance Entity Group (MEG) End Points (MEPs). The
group are known as a maintenance entity group (MEG). The two collection of one or more MEs that belongs to the same transport
points that define a maintenance entity are called Maintenance path and that are maintained and monitored as a group are known
Entity Group (MEG) End Points (MEPs). In between these two as a maintenance entity group (MEG). In between MEPs, there are
points zero or more intermediate points, called Maintenance zero or more intermediate points, called Maintenance Entity
Entity Group Intermediate Points (MIPs). MEPs and MIPs are Group Intermediate Points (MIPs). MEPs and MIPs are associated
associated with the MEG and can be shared by more than one ME in with the MEG and can be shared by more than one ME in a MEG.
a MEG.
An abstract reference model for an ME is illustrated in Figure 1 An abstract reference model for an ME is illustrated in Figure 1
below: below:
+-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+
|A|----|B|----|C|----|D| |A|----|B|----|C|----|D|
+-+ +-+ +-+ +-+ +-+ +-+ +-+ +-+
Figure 1 ME Abstract Reference Model Figure 1 ME Abstract Reference Model
The instantiation of this abstract model to different MPLS-TP The instantiation of this abstract model to different MPLS-TP
entities is described in section 4. In Figure 1, nodes A and D entities is described in section 4. In Figure 1, nodes A and D
can be LERs for an LSP or the T-PEs for a MS-PW, nodes B and C can be LERs for an LSP or the Terminating Provider Edges (T-PEs)
are LSRs for a LSP or S-PEs for a MS-PW. MEPs reside in nodes A for a MS-PW, nodes B and C are LSRs for a LSP or Switching PEs
and D while MIPs reside in nodes B and C and may reside in A and (S-PEs) for a MS-PW. MEPs reside in nodes A and D while MIPs
D. The links connecting adjacent nodes can be physical links, reside in nodes B and C and may reside in A and D. The links
(sub-)layer LSPs/SPMEs, or server layer paths. connecting adjacent nodes can be physical links, (sub-)layer
LSPs/SPMEs, or server layer paths.
This functional model defines the relationships between all OAM This functional model defines the relationships between all OAM
entities from a maintenance perspective and it allows each entities from a maintenance perspective and it allows each
Maintenance Entity to monitor and manage the (sub-)layer network Maintenance Entity to provide monitoring and management for the
under its responsibility and to localize problems efficiently. (sub-)layer network under its responsibility and efficient
localization of problems.
An MPLS-TP Maintenance Entity Group may be defined to monitor An MPLS-TP Maintenance Entity Group may be defined to monitor
the transport path for fault and/or performance management. the transport path for fault and/or performance management.
The MEPs that form a MEG bound the scope of an OAM flow to the The MEPs that form a MEG bound the scope of an OAM flow to the
MEG (i.e. within the domain of the transport path that is being MEG (i.e. within the domain of the transport path that is being
monitored and managed). There are two exceptions to this: monitored and managed). There are two exceptions to this:
1) A misbranching fault may cause OAM packets to be delivered to 1) A misbranching fault may cause OAM packets to be delivered to
a MEP that is not in the MEG of origin. a MEP that is not in the MEG of origin.
skipping to change at page 11, line 35 skipping to change at page 13, line 35
and the originating MEP. and the originating MEP.
In case of unidirectional point-to-point transport paths, a In case of unidirectional point-to-point transport paths, a
single unidirectional Maintenance Entity is defined to monitor single unidirectional Maintenance Entity is defined to monitor
it. it.
In case of associated bi-directional point-to-point transport In case of associated bi-directional point-to-point transport
paths, two independent unidirectional Maintenance Entities are paths, two independent unidirectional Maintenance Entities are
defined to independently monitor each direction. This has defined to independently monitor each direction. This has
implications for transactions that terminate at or query a MIP, implications for transactions that terminate at or query a MIP,
as a return path from MIP to source MEP does not necessarily as a return path from MIP to originating MEP does not
exist in the MEG. necessarily exist in the MEG.
In case of co-routed bi-directional point-to-point transport In case of co-routed bi-directional point-to-point transport
paths, a single bidirectional Maintenance Entity is defined to paths, a single bidirectional Maintenance Entity is defined to
monitor both directions congruently. monitor both directions congruently.
In case of unidirectional point-to-multipoint transport paths, a In case of unidirectional point-to-multipoint transport paths, a
single unidirectional Maintenance entity for each leaf is single unidirectional Maintenance entity for each leaf is
defined to monitor the transport path from the root to that defined to monitor the transport path from the root to that
leaf. leaf.
skipping to change at page 12, line 22 skipping to change at page 14, line 22
+-+ +-+\ +-+ +-+ +-+ +-+\ +-+ +-+
\--|F| \--|F|
+-+ +-+
Figure 2 Reference Model for p2mp MEG Figure 2 Reference Model for p2mp MEG
In case of p2mp transport paths, the OAM measurements are In case of p2mp transport paths, the OAM measurements are
independent for each ME (A-D, A-E and A-F): independent for each ME (A-D, A-E and A-F):
o Fault conditions - some faults may impact more than one ME o Fault conditions - some faults may impact more than one ME
depending from where the failure is located; depending from where the failure is located;
o Packet loss - packet dropping may impact more than one ME o Packet loss - packet dropping may impact more than one ME
depending from where the packets are lost; depending from where the packets are lost;
o Packet delay - will be unique per ME. o Packet delay - will be unique per ME.
Each leaf (i.e. D, E and F) terminates OAM flows to monitor the Each leaf (i.e. D, E and F) terminates OAM flows to monitor the
ME between itself and the root while the root (i.e. A) generates ME between itself and the root while the root (i.e. A) generates
OAM messages common to all the MEs of the p2mp MEG. All nodes OAM messages common to all the MEs of the p2mp MEG. All nodes
may implement a MIP in the corresponding MEG. may implement a MIP in the corresponding MEG.
3.2. Nested MEGs: SPMEs and Tandem Connection Monitoring 3.2. Nested MEGs: SPMEs and Tandem Connection Monitoring
In order to verify and maintain performance and quality In order to verify and maintain performance and quality
guarantees, there is a need to not only apply OAM functionality guarantees, there is a need to not only apply OAM functionality
on a transport path granularity (e.g. LSP or MS-PW), but also on on a transport path granularity (e.g. LSP or MS-PW), but also on
arbitrary parts of transport paths, defined as Tandem arbitrary parts of transport paths, defined as Tandem
Connections, between any two arbitrary points along a transport Connections, between any two arbitrary points along a transport
path. path.
Sub-path Maintenance Elements (SPMEs), as defined in [8], are Sub-path Maintenance Elements (SPMEs), as defined in [8], are
instantiated to provide monitoring of a portion of a set of co- hierarchical LSPs instantiated to provide monitoring of a
routed transport paths (LSPs or MS-PWs). The operational aspects portion of a set of transport paths (LSPs or MS-PWs) that are
of instantiating SPMEs are out of scope of this memo. co-routed within the OAM domain. The operational aspects of
instantiating SPMEs are out of scope of this memo.
SPMEs can also be employed to meet the requirement to provide SPMEs can also be employed to meet the requirement to provide
tandem connection monitoring (TCM). tandem connection monitoring (TCM), as defined by ITU-T
Recommendation G.805 [19].
TCM for a given path segment of a transport path is implemented TCM for a given path segment of a transport path is implemented
by creating an SPME that has a 1:1 association with the path by creating an SPME that has a 1:1 association with the path
segment of the transport path that is to be monitored. segment of the transport path that is to be monitored.
In the TCM case, this means that the SPME used to provide TCM In the TCM case, this means that the SPME used to provide TCM
can carry one and only one transport path thus allowing direct can carry one and only one transport path thus allowing direct
correlation between all fault management and performance correlation between all fault management and performance
monitoring information gathered for the SPME and the monitored monitoring information gathered for the SPME and the monitored
path segment of the end-to-end transport path. The SPME is path segment of the end-to-end transport path.
monitored using normal LSP monitoring.
There are a number of implications to this approach: There are a number of implications to this approach:
1) The SPME would use the uniform model [22] of TC code point 1) The SPME would use the uniform model [22] of Traffic Class
copying between sub-layers for diffserv such that the E2E (TC) code point copying between sub-layers for diffserv such
markings and PHB treatment for the transport path was that the E2E markings and PHB treatment for the transport
preserved by the SPMEs. path was preserved by the SPMEs.
2) The SPME normally would use the short-pipe model for TTL 2) The SPME normally would use the short-pipe model for TTL
handling [6] such that MIP addressing for the E2E entity handling [6] (no TTL copying between sub-layer) such that the
would be not be impacted by the presence of the SPME, but it TTL distance to the MIPs for the E2E entity would be not be
should be possible for an operator to specify use of the impacted by the presence of the SPME, but it should be
uniform model. possible for an operator to specify use of the uniform model.
3) PM statistics need to be adjusted for the encapsulation
overhead of the additional SPME sub-layer.
Note that points 1 and 2 above assume that the TTL copying mode Note that points 1 and 2 above assume that the TTL copying mode
and TC copying modes are independently configurable for an LSP. and TC copying modes are independently configurable for an LSP.
There are specific issues with the use of the uniform model of There are specific issues with the use of the uniform model of
TTL copying for an SPME: TTL copying for an SPME:
1. As any MIP in the SPME sub-layer is not part of the transport path 1. A MIP in the SPME sub-layer is not part of the transport path MEG,
MEG, hence only an out of band return path for OAM originating in hence only an out of band return path for OAM originating in the
the transport path MEG that addressed an SPME MIP might be transport path MEG that addressed an SPME MIP might be available.
available.
2. The instantiation of a lower level MEG or protection switching 2. The instantiation of a lower level MEG or protection switching
actions within a lower level MEG may change the TTL distances to actions within a lower level MEG may change the TTL distances to
MIPs in the higher level MEGs. MIPs in the higher level MEGs.
The endpoints of the SPME are MEPs and limit the scope of an OAM The endpoints of the SPME are MEPs and limit the scope of an OAM
flow within the MEG that the MEPs belong to (i.e. within the flow within the MEG that the MEPs belong to (i.e. within the
domain of the SPME that is being monitored and managed). domain of the SPME that is being monitored and managed).
When considering SPMEs, it is important to consider that the When considering SPMEs, it is important to consider that the
following properties apply to all MPLS-TP MEGs: following properties apply to all MPLS-TP MEGs (regardless of
whether they instrument LSPs, SPMEs or MS-PWs):
o They can be nested but not overlapped, e.g. a MEG may cover a o They can be nested but not overlapped, e.g. a MEG may cover a
segment or a concatenated segment of another MEG, and may path segment of another MEG, and may also include the
also include the forwarding engine(s) of the node(s) at the forwarding engine(s) of the node(s) at the edge(s) of the
edge(s) of the segment or concatenated segment. However when path segment. However when MEGs are nested, the MEPs and MIPs
MEGs are nested, the MEPs and MIPs in the nested MEG are no in the nested MEG are no longer part of the encompassing MEG.
longer part of the encompassing MEG.
o It is possible that MEPs of nested MEGs reside on a single o It is possible that MEPs of nested MEGs reside on a single
node but again implemented in such a way that they do not node but again implemented in such a way that they do not
overlap. overlap.
o Each OAM flow is associated with a single MEG o Each OAM flow is associated with a single MEG
o OAM packets that instrument a particular direction of a
transport path are subject to the same forwarding treatment
(i.e. fate share) as the data traffic and in some cases may
be required to have common queuing discipline E2E with the
class of traffic monitored. OAM packets can be distinguished
from the data traffic using the GAL and ACH constructs [7]
for LSP and Section or the ACH construct [3]and [7] for
(MS-)PW.
o When a SPME is instantiated after the transport path has been o When a SPME is instantiated after the transport path has been
instantiated the TTL addressing of the MIPs will change for instantiated the TTL distance to the MIPs will change for the
the pipe model of TTL copying, and will change for the pipe model of TTL copying, and will change for the uniform
uniform model if the SPME is not co-routed with the original model if the SPME is not co-routed with the original path.
path.
3.3. MEG End Points (MEPs) 3.3. MEG End Points (MEPs)
MEG End Points (MEPs) are the source and sink points of a MEG. MEG End Points (MEPs) are the source and sink points of a MEG.
In the context of an MPLS-TP LSP, only LERs can implement MEPs In the context of an MPLS-TP LSP, only LERs can implement MEPs
while in the context of an SPME LSRs for the MPLS-TP LSP can be while in the context of an SPME, any LSR of the MPLS-TP LSP can
LERs for SPMEs that contribute to the overall monitoring be an LER of SPMEs that contributes to the overall monitoring
infrastructure for the transport path. Regarding PWs, only T-PEs infrastructure of the transport path. Regarding PWs, only T-PEs
can implement MEPs while for SPMEs supporting one or more PWs can implement MEPs while for SPMEs supporting one or more PWs
both T-PEs and S-PEs can implement SPME MEPs. Any MPLS-TP LSR both T-PEs and S-PEs can implement SPME MEPs. Any MPLS-TP LSR
can implement a MEP for an MPLS-TP Section. can implement a MEP for an MPLS-TP Section.
MEPs are responsible for activating and controlling all of the MEPs are responsible for originating all of the proactive and
proactive and on-demand monitoring OAM functionality for the on-demand monitoring OAM functionality for the MEG. There is a
MEG. There is a separate class of notifications (such as Lock separate class of notifications (such as Lock report (LKR) and
report (LKR) and Alarm indication signal (AIS)) that are Alarm indication signal (AIS)) that are originated by
originated by intermediate nodes and triggered by server layer intermediate nodes and triggered by server layer events. A MEP
events. A MEP is capable of originating and terminating OAM is capable of originating and terminating OAM messages for fault
messages for fault management and performance monitoring. These management and performance monitoring. These OAM messages are
OAM messages are encapsulated into an OAM packet using the G-ACh encapsulated into an OAM packet using the G-ACh with an
with an appropriate channel type as defined in RFC 5586 [7]. A appropriate channel type as defined in RFC 5586 [7]. A MEP
MEP terminates all the OAM packets it receives from the MEG it terminates all the OAM packets it receives from the MEG it
belongs to and silently discards those that do not (note in the belongs to and silently discards those that do not (note in the
particular case of Connectivity Verification (CV) processing a particular case of Connectivity Verification (CV) processing a
CV message from an incorrect MEG will result in a mis- CV message from an incorrect MEG will result in a mis-
connectivity defect and there are further actions taken). The connectivity defect and there are further actions taken). The
MEG the OAM packet belongs to is inferred from the MPLS or PW MEG the OAM packet belongs to is inferred from the MPLS or PW
label or, in case of an MPLS-TP section, the MEG is inferred label or, in case of an MPLS-TP section, the MEG is inferred
from the port on which an OAM packet was received with the GAL from the port on which an OAM packet was received with the GAL
at the top of the label stack. at the top of the label stack.
OAM packets may require the use of an available "out-of-band" OAM packets may require the use of an available "out-of-band"
return path (as defined in [8]). In such cases sufficient return path (as defined in [8]). In such cases sufficient
information is required in the originating transaction such that information is required in the originating transaction such that
the OAM reply packet can be constructed (e.g. IP address). the OAM reply packet can be constructed (e.g. IP address).
Each OAM solution will further detail its applicability as a Each OAM solution document will further detail the applicability
pro-active or on-demand mechanism as well as its usage when: of the tools it defines as a pro-active or on-demand mechanism
as well as its usage when:
o The "in-band" return path exists and it is used; o The "in-band" return path exists and it is used;
o An "out-of-band" return path exists and it is used; o An "out-of-band" return path exists and it is used;
o Any return path does not exist or is not used. o Any return path does not exist or is not used.
Once a MEG is configured, the operator can configure which Once a MEG is configured, the operator can configure which
proactive OAM functions to use on the MEG but the MEPs are proactive OAM functions to use on the MEG but the MEPs are
always enabled. A node at the edge of a MEG always supports a always enabled. A node at the edge of a MEG always supports a
skipping to change at page 15, line 42 skipping to change at page 17, line 34
MEPs terminate all OAM packets received from the associated MEG. MEPs terminate all OAM packets received from the associated MEG.
As the MEP corresponds to the termination of the forwarding path As the MEP corresponds to the termination of the forwarding path
for a MEG at the given (sub-)layer, OAM packets never leak for a MEG at the given (sub-)layer, OAM packets never leak
outside of a MEG in a properly configured fault-free outside of a MEG in a properly configured fault-free
implementation. implementation.
A MEP of an MPLS-TP transport path coincides with transport path A MEP of an MPLS-TP transport path coincides with transport path
termination and monitors it for failures or performance termination and monitors it for failures or performance
degradation (e.g. based on packet counts) in an end-to-end degradation (e.g. based on packet counts) in an end-to-end
scope. Note that both MEP source and MEP sink coincide with scope. Note that both source MEP and sink MEP coincide with
transport paths' source and sink terminations. transport paths' source and sink terminations.
The MEPs of an SPME are not necessarily coincident with the The MEPs of an SPME are not necessarily coincident with the
termination of the MPLS-TP transport path. They are used to termination of the MPLS-TP transport path. They are used to
monitor a path segment of the transport path for failures or monitor a path segment of the transport path for failures or
performance degradation (e.g. based on packet counts) only performance degradation (e.g. based on packet counts) only
within the boundary of the MEG for the SPME. within the boundary of the MEG for the SPME.
An MPLS-TP MEP sink passes a fault indication to its client An MPLS-TP sink MEP passes a fault indication to its client
(sub-)layer network as a consequent action of fault detection. (sub-)layer network as a consequent action of fault detection.
When the client layer is not MPLS TP, the consequent actions in
the client layer (e.g., ignore or generate client layer specific
OAM notifications) are outside the scope of this document.
A node at the edge of a MEG can either support per-node MEP or A node at the edge of a MEG can either support per-node MEP or
per-interface MEP(s). A per-node MEP resides in an unspecified per-interface MEP(s). A per-node MEP resides in an unspecified
location within the node while a per-interface MEP resides on a location within the node while a per-interface MEP resides on a
specific side of the forwarding engine. In particular a per- specific side of the forwarding engine. In particular a per-
interface MEP is called "Up MEP" or "Down MEP" depending on its interface MEP is called "Up MEP" or "Down MEP" depending on its
location as upstream or downstream relative to the forwarding location relative to the forwarding engine. An "Up MEP"
engine. transmits OAM packets towards, and receives them from, the
direction of the forwarding engine, while a "Down MEP" receives
OAM packets from, and transmits them towards, the direction of a
server layer.
Conceptually these "per interface" MIP locations can be mapped
to the MPLS architecture by associating the MIP points with
FTN/ILM/NHLFE processing, such that the MIP positioning within a
node logically bookends the NHLFE processing step of how a
packet is handled by an LSR/LER (either prior to or post label
processing and packet forwarding). A nodal MIP makes no
representation as to where in a nodes packet handling process a
MIP is located.
Source node Up MEP Destination node Up MEP Source node Up MEP Destination node Up MEP
------------------------ ------------------------ ------------------------ ------------------------
| | | | | | | |
|----- -----| |----- -----| |----- -----| |----- -----|
| MEP | | | | | | MEP | | MEP | | | | | | MEP |
| | ---- | | | | ---- | | | | ---- | | | | ---- | |
| In |->-| FW |->-| Out |->- ->-| In |->-| FW |->-| Out | | In |->-| FW |->-| Out |->- ->-| In |->-| FW |->-| Out |
| i/f | ---- | i/f | | i/f | ---- | i/f | | i/f | ---- | i/f | | i/f | ---- | i/f |
|----- -----| |----- -----| |----- -----| |----- -----|
skipping to change at page 17, line 7 skipping to change at page 19, line 11
Source MEP in a source node (case 1), an Up Sink MEP in a Source MEP in a source node (case 1), an Up Sink MEP in a
destination node (case 2), a Down Source MEP in a source node destination node (case 2), a Down Source MEP in a source node
(case 3) and a Down Sink MEP in a destination node (case 4). (case 3) and a Down Sink MEP in a destination node (case 4).
The usage of per-interface Up MEPs extends the coverage of the The usage of per-interface Up MEPs extends the coverage of the
ME for both fault and performance monitoring closer to the edge ME for both fault and performance monitoring closer to the edge
of the domain and allows the isolation of failures or of the domain and allows the isolation of failures or
performance degradation to being within a node or either the performance degradation to being within a node or either the
link or interfaces. link or interfaces.
Each OAM solution will further detail the implications when used Each OAM solution document will further detail the implications
with per-interface or per-node MEPs, if necessary. of the tools it defines when used with per-interface or per-node
MEPs, if necessary.
It may occur that the Up MEPs of an SPME are set on both sides It may occur that multiple MEPs for the same MEG are on the same
of the forwarding engine such that the MEG is entirely internal node, and are all Up MEPs, each on one side of the forwarding
to the node. engine, such that the MEG is entirely internal to the node.
It should be noted that a ME may span nodes that implement per It should be noted that a ME may span nodes that implement per
node MEPs and per-interface MEPs. This guarantees backward node MEPs and per-interface MEPs. This guarantees backward
compatibility with most of the existing LSRs that can implement compatibility with most of the existing LSRs that can implement
only a per-node MEP as in current implementations label only a per-node MEP as in current implementations label
operations are largely performed on the ingress interface, hence operations are largely performed on the ingress interface, hence
the exposure of the GAL as top label will occur at the ingress the exposure of the GAL as top label will occur at the ingress
interface. interface.
Note that a MEP can only exist at the beginning and end of a Note that a MEP can only exist at the beginning and end of a
skipping to change at page 17, line 42 skipping to change at page 19, line 47
A MEG Intermediate Point (MIP) is a function located at a point A MEG Intermediate Point (MIP) is a function located at a point
between the MEPs of a MEG for a PW, LSP or SPME. between the MEPs of a MEG for a PW, LSP or SPME.
A MIP is capable of reacting to some OAM packets and forwarding all A MIP is capable of reacting to some OAM packets and forwarding all
the other OAM packets while ensuring fate sharing with data plane the other OAM packets while ensuring fate sharing with data plane
packets. However, a MIP does not initiate unsolicited OAM packets, packets. However, a MIP does not initiate unsolicited OAM packets,
but may be addressed by OAM packets initiated by one of the MEPs of but may be addressed by OAM packets initiated by one of the MEPs of
the MEG. A MIP can generate OAM packets only in response to OAM the MEG. A MIP can generate OAM packets only in response to OAM
packets that it receives from the MEG it belongs to. The OAM messages packets that it receives from the MEG it belongs to. The OAM messages
generated by the MIP are sent in the direction of the source MEP and generated by the MIP are sent to the originating MEP.
not forwarded to the sink MEP.
An intermediate node within a MEG can either: An intermediate node within a MEG can either:
o Support per-node MIP (i.e. a single MIP per node in an o Support per-node MIP (i.e. a single MIP per node in an
unspecified location within the node); unspecified location within the node);
o Support per-interface MIP (i.e. two or more MIPs per node on o Support per-interface MIP (i.e. two or more MIPs per node on
both sides of the forwarding engine). both sides of the forwarding engine).
Intermediate node Intermediate node
------------------------ ------------------------
| | | |
|----- -----| |----- -----|
| MIP | | MIP | | MIP | | MIP |
| | ---- | | | | ---- | |
->-| In |->-| FW |->-| Out |->- ->-| In |->-| FW |->-| Out |->-
| i/f | ---- | i/f | | i/f | ---- | i/f |
|----- -----| |----- -----|
skipping to change at page 18, line 34 skipping to change at page 20, line 37
When sending an OAM packet to a MIP, the source MEP should set When sending an OAM packet to a MIP, the source MEP should set
the TTL field to indicate the number of hops necessary to reach the TTL field to indicate the number of hops necessary to reach
the node where the MIP resides. the node where the MIP resides.
The source MEP should also include Target MIP information in the The source MEP should also include Target MIP information in the
OAM packets sent to a MIP to allow proper identification of the OAM packets sent to a MIP to allow proper identification of the
MIP within the node. The MEG the OAM packet is associated with MIP within the node. The MEG the OAM packet is associated with
is inferred from the MPLS label. is inferred from the MPLS label.
The use of TTL expiry to deliver OAM packets to a specific MIP
is not a fully reliable delivery mechanism because the TTL
distance of a MIP from a MEP can change. Any MPLS-TP node
silently discards any OAM packet received with an expired TTL
and that it is not addressed to any of its MIPs or MEPs. An
MPLS-TP node that does not support OAM is also expected to
silently discard any received OAM packet.
Messages directed to a MIP may not necessarily carry specific
MIP identification information beyond that of TTL distance. In
this case a MIP would promiscuously respond to all MEP queries
with the correct MEG. This capability could be used for
discovery functions (e.g., route tracing as defined in section
6.4) or when it is desirable to leave to the originating MEP the
job of correlating TTL and MIP identifiers and noting changes or
irregularities (via comparison with information previously
extracted from the network).
MIPs are associated to the MEG they belong to and their identity
is unique within the MEG. However, their identity is not
necessarily unique to the MEG: e.g. all nodal MIPs in a node can
have a common identity.
A node at the edge of a MEG can also support per-interface Up A node at the edge of a MEG can also support per-interface Up
MEPs and per-interface MIPs on either side of the forwarding MEPs and per-interface MIPs on either side of the forwarding
engine. engine.
Once a MEG is configured, the operator can enable/disable the Once a MEG is configured, the operator can enable/disable the
MIPs on the nodes within the MEG. All the intermediate nodes and MIPs on the nodes within the MEG. All the intermediate nodes and
possibly the end nodes host MIP(s). Local policy allows them to possibly the end nodes host MIP(s). Local policy allows them to
be enabled per function and per MEG. The local policy is be enabled per function and per MEG. The local policy is
controlled by the management system, which may delegate it to controlled by the management system, which may delegate it to
the control plane. the control plane. A disabled MIP silently discards any received
OAM packets.
3.5. Server MEPs 3.5. Server MEPs
A server MEP is a MEP of a MEG that is either: A server MEP is a MEP of a MEG that is either:
o Defined in a layer network that is "below", which is to say o Defined in a layer network that is "below", which is to say
encapsulates and transports the MPLS-TP layer network being encapsulates and transports the MPLS-TP layer network being
referenced, or referenced, or
o Defined in a sub-layer of the MPLS-TP layer network that is o Defined in a sub-layer of the MPLS-TP layer network that is
"below" which is to say encapsulates and transports the "below" which is to say encapsulates and transports the
sub-layer being referenced. sub-layer being referenced.
A server MEP can coincide with a MIP or a MEP in the client A server MEP can coincide with a MIP or a MEP in the client
(MPLS-TP) (sub-)layer network. (MPLS-TP) (sub-)layer network.
A server MEP also provides server layer OAM indications to the A server MEP also provides server layer OAM indications to the
client/server adaptation function between the client (MPLS-TP) client/server adaptation function between the client (MPLS-TP)
(sub-)layer network and the server (sub-)layer network. The (sub-)layer network and the server (sub-)layer network. The
adaptation function maintains state on the mapping of MPLS-TP adaptation function maintains state on the mapping of MPLS-TP
transport paths that are setup over that server (sub-)layer's transport paths that are setup over that server (sub-)layer's
transport path. transport path.
For example, a server MEP can be either: For example, a server MEP can be either:
o A termination point of a physical link (e.g. 802.3), an SDH o A termination point of a physical link (e.g. 802.3), an SDH
VC or OTN ODU, for the MPLS-TP Section layer network, defined VC or OTN ODU, for the MPLS-TP Section layer network, defined
in section 4.1; in section 4.1;
o An MPLS-TP Section MEP for MPLS-TP LSPs, defined in section o An MPLS-TP Section MEP for MPLS-TP LSPs, defined in section
4.2; 4.2;
o An MPLS-TP LSP MEP for MPLS-TP PWs, defined in section 4.3; o An MPLS-TP LSP MEP for MPLS-TP PWs, defined in section 4.3;
o An MPLS-TP SPME MEP used for LSP path segment monitoring, as o An MPLS-TP SPME MEP used for LSP path segment monitoring, as
defined in section 4.4, for MPLS-TP LSPs or higher-level defined in section 4.4, for MPLS-TP LSPs or higher-level
SPMEs providing LSP path segment monitoring; SPMEs providing LSP path segment monitoring;
o An MPLS-TP SPME MEP used for PW path segment monitoring, as o An MPLS-TP SPME MEP used for PW path segment monitoring, as
defined in section 4.5, for MPLS-TP PWs or higher-level SPMEs defined in section 4.5, for MPLS-TP PWs or higher-level SPMEs
providing PW path segment monitoring. providing PW path segment monitoring.
The server MEP can run appropriate OAM functions for fault detection The server MEP can run appropriate OAM functions for fault detection
within the server (sub-)layer network, and provides a fault within the server (sub-)layer network, and provides a fault
indication to its client MPLS-TP layer network via the client/server indication to its client MPLS-TP layer network via the client/server
adaptation function. When the server layer is not MPLS-TP, server MEP adaptation function. When the server layer is not MPLS-TP, server MEP
OAM functions are outside the scope of this document. OAM functions are outside the scope of this document.
3.6. Configuration Considerations 3.6. Configuration Considerations
When a control plane is not present, the management plane configures When a control plane is not present, the management plane configures
skipping to change at page 20, line 45 skipping to change at page 23, line 25
distance. The OAM message must contain sufficient distance. The OAM message must contain sufficient
information to identify the target MIP and therefore is information to identify the target MIP and therefore is
processed only by the target MIP. processed only by the target MIP.
o In order to send an OAM packet to M leaves (i.e., a subset o In order to send an OAM packet to M leaves (i.e., a subset
of all the leaves), the source MEP sends M different OAM of all the leaves), the source MEP sends M different OAM
packets targeted to each individual leaf in the group of M packets targeted to each individual leaf in the group of M
leaves. Aggregated or sub setting mechanisms are outside leaves. Aggregated or sub setting mechanisms are outside
the scope of this document. the scope of this document.
P2MP paths are unidirectional; therefore any return path to a A bud node with a Down MEP or a per-node MEP will both terminate
source MEP for on-demand transactions will be out-of-band. A and relay OAM packets. Similar to how fault coverage is
mechanism to scope the set of MEPs or MIPs expected to respond maximized by the explicit utilization of Up MEPs, the same is
to a given "on-demand" transaction is useful as it relieves the true for MEPs on a bud node.
source MEP of the requirement to filter and discard undesired
responses as normally TTL exhaustion will address all MIPs at a P2MP paths are unidirectional; therefore any return path to an
given distance from the source, and failure to exhaust TTL will originating MEP for on-demand transactions will be out-of-band.
address all MEPs. A mechanism to target "on-demand" transactions to a single MEP
or MIP is required as it relieves the originating MEP of an
arbitrarily large processing load and of the requirement to
filter and discard undesired responses as normally TTL
exhaustion will address all MIPs at a given distance from the
source, and failure to exhaust TTL will address all MEPs.
3.8. Further considerations of enhanced segment monitoring 3.8. Further considerations of enhanced segment monitoring
Segment monitoring in transport network should meet the Segment monitoring, like any in-service monitoring, in a
following network objectives: transport network should meet the following network objectives:
1. The monitoring and maintenance of existing transport paths has to 1. The monitoring and maintenance of existing transport paths has to
be conducted in service without traffic disruption. be conducted in service without traffic disruption.
2. The monitored or managed transport path condition has to be 2. Segment monitoring must not modify the forwarding of the segment
exactly the same irrespective of any configurations necessary for portion of the transport path.
maintenance.
SPMEs defined in section 3.2 meet the above two objectives, when SPMEs defined in section 3.2 meet the above two objectives, when
they are pre-configured or pre-instantiated as exemplified in they are pre-configured or pre-instantiated as exemplified in
section 3.6. However, pre-design and pre-configuration of all section 3.6. However, pre-design and pre-configuration of all
the considered patterns of SPME are not sometimes preferable in the considered patterns of SPME are not sometimes preferable in
real operation due to the burden of design works, a number of real operation due to the burden of design works, a number of
header consumptions, bandwidth consumption and so on. header consumptions, bandwidth consumption and so on.
When SPMEs are configured or instantiated after the transport When SPMEs are configured or instantiated after the transport
path has been created, network objective (1) can be met, but path has been created, network objective (1) can be met:
network objective (2) cannot be met due to new assignment of application and removal of SPME to a faultless monitored
MPLS labels. transport entity can be performed in such a way as not to
introduce any loss of traffic, e.g., by using non-disruptive
"make before break" technique.
However, network objective (2) cannot be met due to new
assignment of MPLS labels. As a consequence, generally speaking,
the results of SPME monitoring are not necessarily correlated
with the behaviour of traffic in the monitored entity when it
does not use SPME. For example, application of SPME to a
problematic/faulty monitoring entity might "fix" the problem
encountered by the latter - for as long as SPME is applied. And
vice versa, application of SPME to a faultless monitored entity
may result in making it faulty - again, as long as SPME is
applied.
Support for a more sophisticated segment monitoring mechanism Support for a more sophisticated segment monitoring mechanism
(temporal and hitless segment monitoring) to efficiently meet (temporal and hitless segment monitoring) to efficiently meet
the two network objectives may be necessary. the two network objectives may be necessary.
One possible option to instantiate non-intrusive segment
monitoring without the use of SPMEs would require the MIPs
selected as monitoring endpoints to implement enhanced
functionality and state for the monitored transport path.
For example the MIPs need to be configured with the TTL distance
to the peer or with the address of the peer, when out-of-band
return paths are used.
A further issue that would need to be considered is events that
result in changing the TTL distance to the peer monitoring
entity such as protection events that may temporarily invalidate
OAM information gleaned from the use of this technique.
Further considerations on this technique are outside the scope
of this document.
4. Reference Model 4. Reference Model
The reference model for the MPLS-TP framework builds upon the The reference model for the MPLS-TP framework builds upon the
concept of a MEG, and its associated MEPs and MIPs, to support concept of a MEG, and its associated MEPs and MIPs, to support
the functional requirements specified in RFC 5860 [11]. the functional requirements specified in RFC 5860 [11].
The following MPLS-TP MEGs are specified in this document: The following MPLS-TP MEGs are specified in this document:
o A Section Maintenance Entity Group (SME), allowing monitoring o A Section Maintenance Entity Group (SMEG), allowing
and management of MPLS-TP Sections (between MPLS LSRs). monitoring and management of MPLS-TP Sections (between MPLS
LSRs).
o An LSP Maintenance Entity Group (LME), allowing monitoring o An LSP Maintenance Entity Group (LMEG), allowing monitoring
and management of an end-to-end LSP (between LERs). and management of an end-to-end LSP (between LERs).
o A PW Maintenance Entity Group (PME), allowing monitoring and o A PW Maintenance Entity Group (PMEG), allowing monitoring and
management of an end-to-end SS/MS-PWs (between T-PEs). management of an end-to-end SS/MS-PWs (between T-PEs).
o An LSP SPME ME Group (LSMEG), allowing monitoring and o An LSP SPME ME Group (LSMEG), allowing monitoring and
management of an SPME (between a given pair of LERs and/or management of an SPME (between a given pair of LERs and/or
LSRs along an LSP). LSRs along an LSP).
o A PW SPME ME Group (PSMEG), allowing monitoring and o A PW SPME ME Group (PSMEG), allowing monitoring and
management of an SPME (between a given pair of T-PEs and/or management of an SPME (between a given pair of T-PEs and/or
S-PEs along an (MS-)PW). S-PEs along an (MS-)PW).
The MEGs specified in this MPLS-TP framework are compliant with The MEGs specified in this MPLS-TP OAM framework are compliant
the architecture framework for MPLS-TP MS-PWs [4] and LSPs [1]. with the architecture framework for MPLS-TP [8] that includes
both MS-PWs [4] and LSPs [1].
Hierarchical LSPs are also supported in the form of SPMEs. In Hierarchical LSPs are also supported in the form of SPMEs. In
this case, each LSP in the hierarchy is a different sub-layer this case, each LSP in the hierarchy is a different sub-layer
network that can be monitored, independently from higher and network that can be monitored, independently from higher and
lower level LSPs in the hierarchy, on an end-to-end basis (from lower level LSPs in the hierarchy, on an end-to-end basis (from
LER to LER) by a SPME. It is possible to monitor a portion of a LER to LER) by a SPME. It is possible to monitor a portion of a
hierarchical LSP by instantiating a hierarchical SPME between hierarchical LSP by instantiating a hierarchical SPME between
any LERs/LSRs along the hierarchical LSP. any LERs/LSRs along the hierarchical LSP.
Native |<------------------ MS-PW1Z ---------------->| Native Native |<------------------ MS-PW1Z ---------------->| Native
Layer | | Layer Layer | | Layer
Service | |<LSP13>| |<-LSP3X->| |<LSPXZ>| | Service Service | |<LSP13>| |<-LSP3X->| |<LSPXZ>| | Service
(AC1) V V LSP V V LSP V V LSP V V (AC2) (AC1) V V V V V V V V (AC2)
+----+ +-+ +----+ +----+ +-+ +----+ +----+ +---+ +----+ +----+ +---+ +----+
+----+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +----+ +----+ |T-PE| |LSR| |S-PE| |S-PE| |LSR| |T-PE| +----+
| | | |=======| |=========| |=======| | | | | | | |=======| |=========| |=======| | | |
| CE1|--|.......PW13......|...PW3X..|......PWXZ.......|---|CE2 | | CE1|--|.......PW13......|...PW3X..|......PWXZ.......|---|CE2 |
| | | |=======| |=========| |=======| | | | | | | |=======| |=========| |=======| | | |
+----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ | 1 | | 2 | | 3 | | X | | Y | | Z | +----+
+----+ +-+ +----+ +----+ +-+ +----+ +----+ +---+ +----+ +----+ +---+ +----+
. . . . . . . .
| | | | | | | |
|<--- Domain 1 -->| |<--- Domain Z -->| |<--- Domain 1 -->| |<--- Domain Z -->|
^----------------- PW1Z PME -----------------^ ^----------------- PW1Z PME -----------------^
^--- PW13 PSME ---^ ^--- PWXZ PSME ---^ ^--- PW13 PSMEG---^ ^--- PWXZ PSMEG---^
^-------^ ^-------^ ^-------^ ^-------^
LSP13 LME LSPXZ LME LSP13 LMEG LSPXZ LMEG
^--^ ^--^ ^---------^ ^--^ ^--^ ^--^ ^--^ ^---------^ ^--^ ^--^
Sec12 Sec23 Sec3X SecXY SecYZ Sec12 Sec23 Sec3X SecXY SecYZ
SME SME SME SME SME SMEG SMEG SMEG SMEG SMEG
TPE1: Terminating Provider Edge 1 SPE2: Switching Provider Edge ^---^ ME
3 ^ MEP
TPEX: Terminating Provider Edge X SPEZ: Switching Provider Edge ==== LSP
Z .... PW
^---^ ME ^ MEP ==== LSP .... PW T-PE1: Terminating Provider Edge 1
LSR: Label Switching Router 2
S-PE3: Switching Provider Edge 3
T-PEX: Terminating Provider Edge X
LSRY: Label Switching Router Y
S-PEZ: Switching Provider Edge Z
Figure 5 Reference Model for the MPLS-TP OAM Framework Figure 5 Reference Model for the MPLS-TP OAM Framework
Figure 5 depicts a high-level reference model for the MPLS-TP Figure 5 depicts a high-level reference model for the MPLS-TP
OAM framework. The figure depicts portions of two MPLS-TP OAM framework. The figure depicts portions of two MPLS-TP
enabled network domains, Domain 1 and Domain Z. In Domain 1, enabled network domains, Domain 1 and Domain Z. In Domain 1,
LSR1 is adjacent to LSR2 via the MPLS-TP Section Sec12 and LSR2 LSR1 is adjacent to LSR2 via the MPLS-TP Section Sec12 and LSR2
is adjacent to LSR3 via the MPLS-TP Section Sec23. Similarly, in is adjacent to LSR3 via the MPLS-TP Section Sec23. Similarly, in
Domain Z, LSRX is adjacent to LSRY via the MPLS-TP Section SecXY Domain Z, LSRX is adjacent to LSRY via the MPLS-TP Section SecXY
and LSRY is adjacent to LSRZ via the MPLS-TP Section SecYZ. In and LSRY is adjacent to LSRZ via the MPLS-TP Section SecYZ. In
addition, LSR3 is adjacent to LSRX via the MPLS-TP Section 3X. addition, LSR3 is adjacent to LSRX via the MPLS-TP Section 3X.
Figure 5 also shows a bi-directional MS-PW (PW1Z) between AC1 on Figure 5 also shows a bi-directional MS-PW (PW1Z) between AC1 on
TPE1 and AC2 on TPEZ. The MS-PW consists of three bi-directional T-PE1 and AC2 on T-PEZ. The MS-PW consists of three
PW path segments: 1) PW13 path segment between T-PE1 and S-PE3 bi-directional PW path segments: 1) PW13 path segment between T-
via the bi-directional LSP13 LSP, 2) PW3X path segment between PE1 and S-PE3 via the bi-directional LSP13 LSP, 2) PW3X path
S-PE3 and S-PEX, via the bi-directional LSP3X LSP, and 3) PWXZ segment between S-PE3 and S-PEX, via the bi-directional LSP3X
path segment between S-PEX and T-PEZ via the bi-directional LSP, and 3) PWXZ path segment between S-PEX and T-PEZ via the
LSPXZ LSP. bi-directional LSPXZ LSP.
The MPLS-TP OAM procedures that apply to a MEG are expected to The MPLS-TP OAM procedures that apply to a MEG are expected to
operate independently from procedures on other MEGs. Yet, this operate independently from procedures on other MEGs. Yet, this
does not preclude that multiple MEGs may be affected does not preclude that multiple MEGs may be affected
simultaneously by the same network condition, for example, a simultaneously by the same network condition, for example, a
fiber cut event. fiber cut event.
Note that there are no constrains imposed by this OAM framework Note that there are no constrains imposed by this OAM framework
on the number, or type (p2p, p2mp, LSP or PW), of MEGs that may on the number, or type (p2p, p2mp, LSP or PW), of MEGs that may
be instantiated on a particular node. In particular, when be instantiated on a particular node. In particular, when
looking at Figure 5, it should be possible to configure one or looking at Figure 5, it should be possible to configure one or
more MEPs on the same node if that node is the endpoint of one more MEPs on the same node if that node is the endpoint of one
or more MEGs. or more MEGs.
Figure 5 does not describe a PW3X PSME because typically SPMEs Figure 5 does not describe a PW3X PSMEG because typically SPMEs
are used to monitor an OAM domain (like PW13 and PWXZ PSMEs) are used to monitor an OAM domain (like PW13 and PWXZ PSMEGs)
rather than the segment between two OAM domains. However the OAM rather than the segment between two OAM domains. However the OAM
framework does not pose any constraints on the way SPMEs are framework does not pose any constraints on the way SPMEs are
instantiated as long as they are not overlapping. instantiated as long as they are not overlapping.
The subsections below define the MEGs specified in this MPLS-TP The subsections below define the MEGs specified in this MPLS-TP
OAM architecture framework document. Unless otherwise stated, OAM architecture framework document. Unless otherwise stated,
all references to domains, LSRs, MPLS-TP Sections, LSPs, all references to domains, LSRs, MPLS-TP Sections, LSPs,
pseudowires and MEGs in this section are made in relation to pseudowires and MEGs in this section are made in relation to
those shown in Figure 5. those shown in Figure 5.
4.1. MPLS-TP Section Monitoring (SME) 4.1. MPLS-TP Section Monitoring (SMEG)
An MPLS-TP Section ME (SME) is an MPLS-TP maintenance entity An MPLS-TP Section MEG (SMEG) is an MPLS-TP maintenance entity
intended to monitor an MPLS-TP Section as defined in RFC 5654 intended to monitor an MPLS-TP Section as defined in RFC 5654
[5]. An SME may be configured on any MPLS-TP section. SME OAM [5]. An SMEG may be configured on any MPLS-TP section. SMEG OAM
packets must fate share with the user data packets sent over the packets must fate share with the user data packets sent over the
monitored MPLS-TP Section. monitored MPLS-TP Section.
An SME is intended to be deployed for applications where it is An SMEG is intended to be deployed for applications where it is
preferable to monitor the link between topologically adjacent preferable to monitor the link between topologically adjacent
(next hop in this layer network) MPLS-TP LSRs rather than (next hop in this layer network) MPLS-TP LSRs rather than
monitoring the individual LSP or PW path segments traversing the monitoring the individual LSP or PW path segments traversing the
MPLS-TP Section and the server layer technology does not provide MPLS-TP Section and the server layer technology does not provide
adequate OAM capabilities. adequate OAM capabilities.
Figure 5 shows five Section MEs configured in the network Figure 5 shows five Section MEGs configured in the network
between AC1 and AC2: between AC1 and AC2:
1. Sec12 ME associated with the MPLS-TP Section between LSR 1 1. Sec12 MEG associated with the MPLS-TP Section between LSR 1
and LSR 2, and LSR 2,
2. Sec23 ME associated with the MPLS-TP Section between LSR 2 2. Sec23 MEG associated with the MPLS-TP Section between LSR 2
and LSR 3, and LSR 3,
3. Sec3X ME associated with the MPLS-TP Section between LSR 3 3. Sec3X MEG associated with the MPLS-TP Section between LSR 3
and LSR X, and LSR X,
4. SecXY ME associated with the MPLS-TP Section between LSR X 4. SecXY MEG associated with the MPLS-TP Section between LSR X
and LSR Y, and and LSR Y, and
5. SecYZ ME associated with the MPLS-TP Section between LSR Y 5. SecYZ MEG associated with the MPLS-TP Section between LSR Y
and LSR Z. and LSR Z.
4.2. MPLS-TP LSP End-to-End Monitoring (LME) 4.2. MPLS-TP LSP End-to-End Monitoring Group (LMEG)
An MPLS-TP LSP ME (LME) is an MPLS-TP maintenance entity An MPLS-TP LSP MEG (LMEG) is an MPLS-TP maintenance entity group
intended to monitor an end-to-end LSP between two LERs. An LME intended to monitor an end-to-end LSP between its LERs. An LMEG
may be configured on any MPLS LSP. LME OAM packets must fate may be configured on any MPLS LSP. LMEG OAM packets must fate
share with user data packets sent over the monitored MPLS-TP share with user data packets sent over the monitored MPLS-TP
LSP. LSP.
An LME is intended to be deployed in scenarios where it is An LMEG is intended to be deployed in scenarios where it is
desirable to monitor an entire LSP between its LERs, rather desirable to monitor an entire LSP between its LERs, rather
than, say, monitoring individual PWs. than, say, monitoring individual PWs.
Figure 5 depicts two LMEs configured in the network between AC1 Figure 5 depicts two LMEGs configured in the network between AC1
and AC2: 1) the LSP13 LME between LER 1 and LER 3, and 2) the and AC2: 1) the LSP13 LMEG between LER 1 and LER 3, and 2) the
LSPXZ LME between LER X and LER Y. Note that the presence of a LSPXZ LMEG between LER X and LER Y. Note that the presence of a
LSP3X LME in such a configuration is optional, hence, not LSP3X LMEG in such a configuration is optional, hence, not
precluded by this framework. For instance, the SPs may prefer to precluded by this framework. For instance, the SPs may prefer to
monitor the MPLS-TP Section between the two LSRs rather than the monitor the MPLS-TP Section between the two LSRs rather than the
individual LSPs. individual LSPs.
4.3. MPLS-TP PW Monitoring (PME) 4.3. MPLS-TP PW Monitoring (PMEG)
An MPLS-TP PW ME (PME) is an MPLS-TP maintenance entity intended An MPLS-TP PW MEG (PMEG) is an MPLS-TP maintenance entity
to monitor a SS-PW or MS-PW between a pair of T-PEs. A PME can intended to monitor a SS-PW or MS-PW between its T-PEs. A PMEG
be configured on any SS-PW or MS-PW. PME OAM packets must fate can be configured on any SS-PW or MS-PW. PMEG OAM packets must
share with the user data packets sent over the monitored PW. fate share with the user data packets sent over the monitored
PW.
A PME is intended to be deployed in scenarios where it is A PMEG is intended to be deployed in scenarios where it is
desirable to monitor an entire PW between a pair of MPLS-TP desirable to monitor an entire PW between a pair of MPLS-TP
enabled T-PEs rather than monitoring the LSP aggregating enabled T-PEs rather than monitoring the LSP aggregating
multiple PWs between PEs. multiple PWs between PEs.
|<----------------- MS-PW1Z ----------------->| Figure 5 depicts a MS-PW (MS-PW1Z) consisting of three path
| | segments: PW13, PW3X and PWXZ and its associated end-to-end PMEG
| |<LSP13>| |<-LSP3X->| |<LSPXZ>| | (PW1Z PMEG).
V V LSP V V LSP V V LSP V V
+----+ +-+ +----+ +----+ +-+ +----+
+---+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +---+
| |AC1| |=======| |=========| |=======| |AC2| |
|CE1|---|.......PW13......|...PW3X..|.......PWXZ......|---|CE2|
| | | |=======| |=========| |=======| | | |
+---+ | 1 | |2| | 3 | | X | |Y| | Z | +---+
+----+ +-+ +----+ +----+ +-+ +----+
^-------------------PW1Z PME------------------^
Figure 6 MPLS-TP PW ME (PME)
Figure 6 depicts a MS-PW (MS-PW1Z) consisting of three path
segments: PW13, PW3X and PWXZ and its associated end-to-end PME
(PW1Z PME).
4.4. MPLS-TP LSP SPME Monitoring (LSME) 4.4. MPLS-TP LSP SPME Monitoring (LSMEG)
An MPLS-TP LSP SPME ME (LSME) is an MPLS-TP SPME with associated An MPLS-TP LSP SPME MEG (LSMEG) is an MPLS-TP SPME with an
maintenance entity intended to monitor an arbitrary part of an associated maintenance entity group intended to monitor an
LSP between the pair of MEPs instantiated for the SPME arbitrary part of an LSP between the MEPs instantiated for the
independent from the end-to-end monitoring (LME). An LSME can SPME independent from the end-to-end monitoring (LMEG). An LSMEG
monitor an LSP segment or concatenated segment and it may also can monitor an LSP path segment and it may also include the
include the forwarding engine(s) of the node(s) at the edge(s) forwarding engine(s) of the node(s) at the edge(s) of the path
of the segment or concatenated segment. segment.
When SPME is established between non-adjacent LSRs, the edges of When SPME is established between non-adjacent LSRs, the edges of
the SPME becomes adjacent at the LSP sub-layer network and any the SPME becomes adjacent at the LSP sub-layer network and any
LSR that were previously in between becomes an LSR for the SPME. LSR that were previously in between becomes an LSR for the SPME.
Multiple hierarchical LSMEs can be configured on any LSP. LSME Multiple hierarchical LSMEGs can be configured on any LSP. LSMEG
OAM packets must fate share with the user data packets sent over OAM packets must fate share with the user data packets sent over
the monitored LSP path segment. the monitored LSP path segment.
A LSME can be defined between the following entities: A LSME can be defined between the following entities:
o The end node and any intermediate node of a given LSP. o The LER and LSR of a given LSP.
o Any two intermediate nodes of a given LSP. o Any two LSRs of a given LSP.
An LSME is intended to be deployed in scenarios where it is An LSMEG is intended to be deployed in scenarios where it is
preferable to monitor the behavior of a part of an LSP or set of preferable to monitor the behavior of a part of an LSP or set of
LSPs rather than the entire LSP itself, for example when there LSPs rather than the entire LSP itself, for example when there
is a need to monitor a part of an LSP that extends beyond the is a need to monitor a part of an LSP that extends beyond the
administrative boundaries of an MPLS-TP enabled administrative administrative boundaries of an MPLS-TP enabled administrative
domain. domain.
|<-------------------- PW1Z ------------------->| |<-------------------- PW1Z ------------------->|
| | | |
| |<-------------LSP1Z LSP------------->| | | |<-------------LSP1Z LSP------------->| |
| |<-LSP13->| |<LSP3X>| |<-LSPXZ->| | | |<-LSP13->| |<LSP3X>| |<-LSPXZ->| |
V V S-LSP V V S-LSP V V S-LSP V V V V V V V V V V
+----+ +-+ +----+ +----+ +-+ +----+ +----+ +---+ +----+ +----+ +---+ +----+
+----+ | PE1| | | |DBN3| |DBNX| | | | PEZ| +----+ +----+ | PE | |LSR| |DBN | |DBN | |LSR| | PE | +----+
| |AC1| |=====================================| |AC2| | | |AC1| |=====================================| |AC2| |
----+ | <span class="insert">PE</span> | <span class="insert">|LSR| |DBN</span> | <span class="insert">|DBN</span> | <span class="insert">|LSR|</span> | <span class="insert">PE</span> | +----+
| CE1|---|.....................PW1Z......................|---|CE2 | | CE1|---|.....................PW1Z......................|---|CE2 |
| | | |=====================================| | | | | | | |=====================================| | | |
+----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+ +----+ | 1 | | 2 | | 3 | | X | | Y | | Z | +----+
+----+ +-+ +----+ +----+ +-+ +----+ +----+ +---+ +----+ +----+ +---+ +----+
. . . . . . . .
| | | | | | | |
|<---- Domain 1 --->| |<---- Domain Z --->| |<---- Domain 1 --->| |<---- Domain Z --->|
^---------^ ^---------^ ^---------^ ^---------^
LSP13 LSME LSPXZ LSME LSP13 LSMEG LSPXZ LSMEG
^-------------------------------------^ ^-------------------------------------^
LSP1Z LME LSP1Z LMEG
DBN: Domain Border Node DBN: Domain Border Node
Figure 7 MPLS-TP LSP SPME ME (LSME) Figure 6 MPLS-TP LSP SPME MEG (LSMEG)
Figure 7 depicts a variation of the reference model in Figure 5 Figure 6 depicts a variation of the reference model in Figure 5
where there is an end-to-end LSP (LSP1Z) between PE1 and PEZ. where there is an end-to-end LSP (LSP1Z) between PE1 and PEZ.
LSP1Z consists of, at least, three LSP Concatenated Segments: LSP1Z consists of, at least, three LSP Concatenated Segments:
LSP13, LSP3X and LSPXZ. In this scenario there are two separate LSP13, LSP3X and LSPXZ. In this scenario there are two separate
LSMEs configured to monitor the LSP1Z: 1) a LSME monitoring the LSMEGs configured to monitor the LSP1Z: 1) a LSMEG monitoring
LSP13 Concatenated Segment on Domain 1 (LSP13 LSME), and 2) a the LSP13 Concatenated Segment on Domain 1 (LSP13 LSMEG), and 2)
LSME monitoring the LSPXZ Concatenated Segment on Domain Z a LSMEG monitoring the LSPXZ Concatenated Segment on Domain Z
(LSPXZ LSME). (LSPXZ LSMEG).
It is worth noticing that LSMEs can coexist with the LME It is worth noticing that LSMEGs can coexist with the LMEG
monitoring the end-to-end LSP and that LSME MEPs and LME MEPs monitoring the end-to-end LSP and that LSMEG MEPs and LMEG MEPs
can be coincident in the same node (e.g. PE1 node supports both can be coincident in the same node (e.g. PE1 node supports both
the LSP1Z LME MEP and the LSP13 LSME MEP). the LSP1Z LMEG MEP and the LSP13 LSMEG MEP).
4.5. MPLS-TP MS-PW SPME Monitoring (PSME) 4.5. MPLS-TP MS-PW SPME Monitoring (PSMEG)
An MPLS-TP MS-PW SPME Monitoring ME (PSME) is an MPLS-TP SPME An MPLS-TP MS-PW SPME Monitoring MEG (PSMEG) is an MPLS-TP SPME
with associated maintenance entity intended to monitor an with an associated maintenance entity group intended to monitor
arbitrary part of an MS-PW between the pair of MEPs instantiated an arbitrary part of an MS-PW between the MEPs instantiated for
form the SPME independently from the end-to-end monitoring the SPME independently of the end-to-end monitoring (PMEG). A
(PME). A PSME can monitor a PW segment or concatenated segment PSMEG can monitor a PW path segment and it may also include the
and it may also include the forwarding engine(s) of the node(s) forwarding engine(s) of the node(s) at the edge(s) of the path
at the edge(s) of the segment or concatenated segment. A PSME is segment. A PSMEG is no different than an SPME, it is simply
no different than an SPME, it is simply named as such to discuss named as such to discuss SPMEs specifically in a PW context.
SPMEs specifically in a PW context.
When SPME is established between non-adjacent S-PEs, the edges When SPME is established between non-adjacent S-PEs, the edges
of the SPME becomes adjacent at the MS-PW sub-layer network and of the SPME becomes adjacent at the MS-PW sub-layer network and
any S-PEs that were previously in between becomes an LSR for the any S-PEs that were previously in between becomes an LSR for the
SPME. SPME.
S-PE placement is typically dictated by considerations other S-PE placement is typically dictated by considerations other
than OAM. S-PEs will frequently reside at operational boundaries than OAM. S-PEs will frequently reside at operational boundaries
such as the transition from distributed (CP) to centralized such as the transition from distributed control plane (CP) to
(NMS) control or at a routing area boundary. As such the centralized Network Management System (NMS) control or at a
architecture would appear not to have the flexibility that routing area boundary. As such the architecture would appear not
arbitrary placement of SPME segments would imply. Support for an to have the flexibility that arbitrary placement of SPME
arbitrary placement of PSME would require the definition of segments would imply. Support for an arbitrary placement of
additional PW sub-layering. PSMEG would require the definition of additional PW
Multiple hierarchical PSMEs can be configured on any MS-PW. PSME sub-layering.
OAM packets fate share with the user data packets sent over the Multiple hierarchical PSMEGs can be configured on any MS-PW.
monitored PW path Segment. PSMEG OAM packets fate share with the user data packets sent
over the monitored PW path Segment.
A PSME does not add hierarchical components to the MPLS architecture, A PSMEG does not add hierarchical components to the MPLS
it defines the role of existing components for the purposes of architecture, it defines the role of existing components for the
discussing OAM functionality. purposes of discussing OAM functionality.
A PSME can be defined between the following entities: A PSME can be defined between the following entities:
o T-PE and any S-PE of a given MS-PW o T-PE and any S-PE of a given MS-PW
o Any two S-PEs of a given MS-PW. o Any two S-PEs of a given MS-PW.
Note that, in line with the SPME description in section 3.2, when a Note that, in line with the SPME description in section 3.2, when a
PW SPME is instantiated after the MS-PW has been instantiated, the PW SPME is instantiated after the MS-PW has been instantiated, the
TTL addressing of the MIPs may change and MIPs in the nested MEG are TTL distance of the MIPs may change and MIPs in the nested MEG are no
no longer part of the encompassing MEG. This means that the S-PE longer part of the encompassing MEG. This means that the S-PE nodes
nodes hosting these MIPs are no longer S-PEs but P nodes at the SPME hosting these MIPs are no longer S-PEs but P nodes at the SPME LSP
LSP level. The consequences are that the S-PEs hosting the PSME MEPs level. The consequences are that the S-PEs hosting the PSMEG MEPs
become adjacent S-PEs. This is no different than the operation of become adjacent S-PEs. This is no different than the operation of
SPMEs in general. SPMEs in general.
A PSME is intended to be deployed in scenarios where it is A PSMEG is intended to be deployed in scenarios where it is
preferable to monitor the behavior of a part of a MS-PW rather preferable to monitor the behavior of a part of a MS-PW rather
than the entire end-to-end PW itself, for example to monitor an than the entire end-to-end PW itself, for example to monitor an
MS-PW path segment within a given network domain of an inter- MS-PW path segment within a given network domain of an inter-
domain MS-PW. domain MS-PW.
|<----------------- MS-PW1Z ------------------>| Figure 5 depicts a MS-PW (MS-PW1Z) consisting of three path
| | segments: PW13, PW3X and PWXZ with two separate PSMEGs: 1) a
| |<LSP13>| |<-LSP3X-->| |<LSPXZ>| | PSMEG monitoring the PW13 MS-PW path segment on Domain 1 (PW13
V V LSP V V LSP V V LSP V V PSMEG), and 2) a PSMEG monitoring the PWXZ MS-PW path segment on
+----+ +-+ +----+ +----+ +-+ +----+ Domain Z with (PWXZ PSMEG).
+---+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +---+
| |AC1| |=======| |==========| |=======| |AC2| |
|CE1|---|.......PW13......|...PW3X...|.......PWXZ......|---|CE2|
| | | |=======| |==========| |=======| | | |
+---+ | 1 | |2| | 3 | | X | |Y| | Z | +---+
+----+ +-+ +----+ +----+ +-+ +----+
^--- PW13 PSME ---^ ^--- PWXZ PSME ----^
^-------------------PW1Z PME-------------------^
Figure 8 MPLS-TP MS-PW SPME Monitoring (PSME)
Figure 8 depicts the same MS-PW (MS-PW1Z) between AC1 and AC2 as
in Figure 6. In this scenario there are two separate PSMEs
configured to monitor MS-PW1Z: 1) a PSME monitoring the PW13
MS-PW path segment on Domain 1 (PW13 PSME), and 2) a PSME
monitoring the PWXZ MS-PW path segment on Domain Z with (PWXZ
PSME).
It is worth noticing that PSMEs can coexist with the PME It is worth noticing that PSMEGs can coexist with the PMEG
monitoring the end-to-end MS-PW and that PSME MEPs and PME MEPs monitoring the end-to-end MS-PW and that PSMEG MEPs and PMEG
can be coincident in the same node (e.g. TPE1 node supports both MEPs can be coincident in the same node (e.g. T-PE1 node
the PW1Z PME MEP and the PW13 PSME MEP). supports both the PW1Z PMEG MEP and the PW13 PSMEG MEP).
4.6. Fate sharing considerations for multilink 4.6. Fate sharing considerations for multilink
Multilink techniques are in use today and are expected to Multilink techniques are in use today and are expected to
continue to be used in future deployments. These techniques continue to be used in future deployments. These techniques
include Ethernet Link Aggregations [21], the use of Link include Ethernet Link Aggregations [21], the use of Link
Bundling for MPLS [17] where the option to spread traffic over Bundling for MPLS [17] where the option to spread traffic over
component links is supported and enabled. While the use of Link component links is supported and enabled. While the use of Link
Bundling can be controlled at the MPLS-TP layer, use of Link Bundling can be controlled at the MPLS-TP layer, use of Link
Aggregation (or any server layer specific multilink) is not Aggregation (or any server layer specific multilink) is not
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2. The operational characteristics of in-band measurement 2. The operational characteristics of in-band measurement
transactions (e.g., CV, Loss Measurement (LM) etc.) are transactions (e.g., CV, Loss Measurement (LM) etc.) are
configured at the MEPs. configured at the MEPs.
3. Server layer events are reported by OAM messages originating 3. Server layer events are reported by OAM messages originating
at intermediate nodes. at intermediate nodes.
4. The measurements resulting from proactive monitoring are 4. The measurements resulting from proactive monitoring are
typically reported outside of the MEG (e.g. to a management typically reported outside of the MEG (e.g. to a management
system) as notifications events such as faults or loss system) as notifications events such as faults or indications
measurement indication of excessive impairment of information of performance degradations (such as excessive packet loss).
transfer capability.
5. The measurements resulting from proactive monitoring may be 5. The measurements resulting from proactive monitoring may be
periodically harvested by an EMS/NMS. periodically harvested by an NMS.
For statically provisioned transport paths the above information For statically provisioned transport paths the above information
is statically configured; for dynamically established transport is statically configured; for dynamically established transport
paths the configuration information is signaled via the control paths the configuration information is signaled via the control
plane or configured via the management plane. plane or configured via the management plane.
The operator may enable/disable some of the consequent actions The operator may enable/disable some of the consequent actions
defined in section 5.1.1.4. defined in section 5.1.1.4.
5.1. Continuity Check and Connectivity Verification 5.1. Continuity Check and Connectivity Verification
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2.2.2 of RFC 5860 [11], are used to detect a loss of continuity 2.2.2 of RFC 5860 [11], are used to detect a loss of continuity
defect (LOC) between two MEPs in a MEG. defect (LOC) between two MEPs in a MEG.
Proactive Connectivity Verification functions, as required in Proactive Connectivity Verification functions, as required in
section 2.2.3 of RFC 5860 [11], are used to detect an unexpected section 2.2.3 of RFC 5860 [11], are used to detect an unexpected
connectivity defect between two MEGs (e.g. mismerging or connectivity defect between two MEGs (e.g. mismerging or
misconnection), as well as unexpected connectivity within the misconnection), as well as unexpected connectivity within the
MEG with an unexpected MEP. MEG with an unexpected MEP.
Both functions are based on the (proactive) generation of OAM Both functions are based on the (proactive) generation of OAM
packets by the source MEP that are processed by the sink MEP. As packets by the source MEP that are processed by the peer sink
a consequence these two functions are grouped together into MEP(s). As a consequence these two functions are grouped
Continuity Check and Connectivity Verification (CC-V) OAM together into Continuity Check and Connectivity Verification
packets. (CC-V) OAM packets.
In order to perform pro-active Connectivity Verification, each In order to perform pro-active Connectivity Verification, each
CC-V OAM packet also includes a globally unique Source MEP CC-V OAM packet also includes a globally unique Source MEP
identifier. When used to perform only pro-active Continuity identifier. When used to perform only pro-active Continuity
Check, the CC-V OAM packet will not include any globally unique Check, the CC-V OAM packet will not include any globally unique
Source MEP identifier. Different formats of MEP identifiers are Source MEP identifier. Different formats of MEP identifiers are
defined in [10] to address different environments. When MPLS-TP defined in [10] to address different environments. When MPLS-TP
is deployed in transport network environments where IP is deployed in transport network environments where IP
addressing is not used in the forwarding plane, the ICC-based addressing is not used in the forwarding plane, the ITU Carrier
format for MEP identification is used. When MPLS-TP is deployed Code (ICC)-based format for MEP identification is used. When
in an IP-based environment, the IP-based MEP identification is MPLS-TP is deployed in an IP-based environment, the IP-based MEP
used. identification is used.
As a consequence, it is not possible to detect misconnections As a consequence, it is not possible to detect misconnections
between two MEGs monitored only for continuity as neither the between two MEGs monitored only for continuity as neither the
OAM message type nor OAM message content provides sufficient OAM message type nor OAM message content provides sufficient
information to disambiguate an invalid source. To expand: information to disambiguate an invalid source. To expand:
o For CC leaking into a CC monitored MEG - undetectable o For CC leaking into a CC monitored MEG - undetectable
o For CV leaking into a CC monitored MEG - presence of o For CV leaking into a CC monitored MEG - presence of
additional Source MEP identifier allows detecting the fault additional Source MEP identifier allows detecting the fault
o For CC leaking into a CV monitored MEG - lack of additional o For CC leaking into a CV monitored MEG - lack of additional
Source MEP identifier allows detecting the fault. Source MEP identifier allows detecting the fault.
o For CV leaking into a CV monitored MEG - different Source MEP o For CV leaking into a CV monitored MEG - different Source MEP
identifier permits fault to be identified. identifier permits fault to be identified.
CC-V OAM packets are transmitted at a regular, operator CC-V OAM packets are transmitted at a regular, operator
configurable, rate. The default CC-V transmission periods are configurable, rate. The default CC-V transmission periods are
application dependent (see section 5.1.3). application dependent (see section 5.1.3).
Proactive CC-V OAM packets are transmitted with the "minimum Proactive CC-V OAM packets are transmitted with the "minimum
loss probability PHB" within the transport path (LSP, PW) they loss probability PHB" within the transport path (LSP, PW) they
are monitoring. This PHB is configurable on network operator's are monitoring. For E-LSPs, this PHB is configurable on network
basis. PHBs can be translated at the network borders by the same operator's basis while for L-LSPs this is determined as per RFC
function that translates it for user data traffic. The 3270 [22]. PHBs can be translated at the network borders by the
same function that translates it for user data traffic. The
implication is that CC-V fate shares with much of the forwarding implication is that CC-V fate shares with much of the forwarding
implementation, but not all aspects of PHB processing are implementation, but not all aspects of PHB processing are
exercised. Either on-demand tools are used for finer grained exercised. Either on-demand tools are used for finer grained
fault finding or an implementation may utilize a CC-V flow per fault finding or an implementation may utilize a CC-V flow per
PHB with the entire E-LSP fate sharing with any individual PHB. PHB to ensure a CC-V flow fate shares with each individual PHB.
In a co-routed or associated, bidirectional point-to-point In a co-routed or associated, bidirectional point-to-point
transport path, when a MEP is enabled to generate pro-active transport path, when a MEP is enabled to generate pro-active
CC-V OAM packets with a configured transmission rate, it also CC-V OAM packets with a configured transmission rate, it also
expects to receive pro-active CC-V OAM packets from its peer MEP expects to receive pro-active CC-V OAM packets from its peer MEP
at the same transmission rate as a common SLA applies to all at the same transmission rate as a common SLA applies to all
components of the transport path. In a unidirectional transport components of the transport path. In a unidirectional transport
path (either point-to-point or point-to-multipoint), only the path (either point-to-point or point-to-multipoint), the source
source MEP is enabled to generate CC-V OAM packets and only the MEP is enabled only to generate CC-V OAM packets while each sink
sink MEP is configured to expect these packets at the configured MEP is configured to expect these packets at the configured
rate. rate.
MIPs, as well as intermediate nodes not supporting MPLS-TP OAM, MIPs, as well as intermediate nodes not supporting MPLS-TP OAM,
are transparent to the pro-active CC-V information and forward are transparent to the pro-active CC-V information and forward
these pro-active CC-V OAM packets as regular data packets. these pro-active CC-V OAM packets as regular data packets.
During path setup and tear down, situations arise where CC-V During path setup and tear down, situations arise where CC-V
checks would give rise to alarms, as the path is not fully checks would give rise to alarms, as the path is not fully
instantiated. In order to avoid these spurious alarms the instantiated. In order to avoid these spurious alarms the
following procedures are recommended. At initialization, the MEP following procedures are recommended. At initialization, the
source function (generating pro-active CC-V packets) should be source MEP function (generating pro-active CC-V packets) should
enabled prior to the corresponding MEP sink function (detecting be enabled prior to the corresponding sink MEP function
continuity and connectivity defects). When disabling the CC-V (detecting continuity and connectivity defects). When disabling
proactive functionality, the MEP sink function should be the CC-V proactive functionality, the sink MEP function should
disabled prior to the corresponding MEP source function. be disabled prior to the corresponding source MEP function.
It should be noted that different encapsulations are possible It should be noted that different encapsulations are possible
for CC-V packets and therefore it is possible that in case of for CC-V packets and therefore it is possible that in case of
mis-configurations or mis-connectivity, CC-V packets are mis-configurations or mis-connectivity, CC-V packets are
received with an unexpected encapsulation. received with an unexpected encapsulation.
There are practical limitations to detecting unexpected There are practical limitations to detecting unexpected
encapsulation. It is possible that there are mis-configuration encapsulation. It is possible that there are mis-configuration
or mis-connectivity scenarios where OAM packets can alias as or mis-connectivity scenarios where OAM packets can alias as
payload, e.g., when a transport path can carry an arbitrary payload, e.g., when a transport path can carry an arbitrary
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the described defect cases, the sink MEP should notify the the described defect cases, the sink MEP should notify the
equipment fault management process of the detected defect. equipment fault management process of the detected defect.
5.1.1.1. Loss Of Continuity defect 5.1.1.1. Loss Of Continuity defect
When proactive CC-V is enabled, a sink MEP detects a loss of When proactive CC-V is enabled, a sink MEP detects a loss of
continuity (LOC) defect when it fails to receive pro-active CC-V continuity (LOC) defect when it fails to receive pro-active CC-V
OAM packets from the source MEP. OAM packets from the source MEP.
o Entry criteria: If no pro-active CC-V OAM packets from the o Entry criteria: If no pro-active CC-V OAM packets from the
source MEP (and in the case of CV, this includes the source MEP (and in the case of CV, this includes the
requirement to have the expected globally unique Source MEP requirement to have the expected globally unique Source MEP
identifier) are received within the interval equal to 3.5 identifier) are received within the interval equal to 3.5
times the receiving MEP's configured CC-V reception period. times the receiving MEP's configured CC-V reception period.
o Exit criteria: A pro-active CC-V OAM packet from the source o Exit criteria: A pro-active CC-V OAM packet from the source
MEP (and again in the case of CV, with the expected globally MEP (and again in the case of CV, with the expected globally
unique Source MEP identifier) is received. unique Source MEP identifier) is received.
5.1.1.2. Mis-connectivity defect 5.1.1.2. Mis-connectivity defect
When a pro-active CC-V OAM packet is received, a sink MEP When a pro-active CC-V OAM packet is received, a sink MEP
identifies a mis-connectivity defect (e.g. mismerge, identifies a mis-connectivity defect (e.g. mismerge,
misconnection or unintended looping) when the received packet misconnection or unintended looping) when the received packet
carries an unexpected globally unique Source MEP identifier. carries an unexpected globally unique Source MEP identifier.
o Entry criteria: The sink MEP receives a pro-active CC-V OAM o Entry criteria: The sink MEP receives a pro-active CC-V OAM
packet with an unexpected globally unique Source MEP packet with an unexpected globally unique Source MEP
identifier or receives a CC or CC/CV OAM packet with an identifier or with an unexpected encapsulation.
unexpected encapsulation.
o Exit criteria: The sink MEP does not receive any pro-active o Exit criteria: The sink MEP does not receive any pro-active
CC-V OAM packet with an unexpected globally unique Source MEP CC-V OAM packet with an unexpected globally unique Source MEP
identifier for an interval equal at least to 3.5 times the identifier for an interval equal at least to 3.5 times the
longest transmission period of the pro-active CC-V OAM longest transmission period of the pro-active CC-V OAM
packets received with an unexpected globally unique Source packets received with an unexpected globally unique Source
MEP identifier since this defect has been raised. This MEP identifier since this defect has been raised. This
requires the OAM message to self identify the CC-V requires the OAM message to self identify the CC-V
periodicity as not all MEPs can be expected to have knowledge periodicity as not all MEPs can be expected to have knowledge
of all MEGs. of all MEGs.
5.1.1.3. Period Misconfiguration defect 5.1.1.3. Period Misconfiguration defect
If pro-active CC-V OAM packets are received with the expected If pro-active CC-V OAM packets are received with the expected
globally unique Source MEP identifier but with a transmission globally unique Source MEP identifier but with a transmission
period different than the locally configured reception period, period different than the locally configured reception period,
then a CV period mis-configuration defect is detected. then a CV period mis-configuration defect is detected.
o Entry criteria: A MEP receives a CC-V pro-active packet with o Entry criteria: A MEP receives a CC-V pro-active packet with
the expected globally unique Source MEP identifier but with a the expected globally unique Source MEP identifier but with a
Period field value different than its own CC-V configured Period field value different than its own CC-V configured
transmission period. transmission period.
o Exit criteria: The sink MEP does not receive any pro-active o Exit criteria: The sink MEP does not receive any pro-active
CC-V OAM packet with the expected globally unique Source MEP CC-V OAM packet with the expected globally unique Source MEP
identifier and an incorrect transmission period for an identifier and an incorrect transmission period for an
interval equal at least to 3.5 times the longest transmission interval equal at least to 3.5 times the longest transmission
period of the pro-active CC-V OAM packets received with the period of the pro-active CC-V OAM packets received with the
expected globally unique Source MEP identifier and an expected globally unique Source MEP identifier and an
incorrect transmission period since this defect has been incorrect transmission period since this defect has been
raised. raised.
5.1.1.4. Unexpected encapsulation defect 5.1.1.4. Unexpected encapsulation defect
If pro-active CC-V OAM packets are received with the expected If pro-active CC-V OAM packets are received with the expected
globally unique Source MEP identifier but with an unexpected globally unique Source MEP identifier but with an unexpected
encapsulation, then a CV unexpected encapsulation defect is encapsulation, then a CV unexpected encapsulation defect is
detected. detected.
It should be noted that there are practical limitations to It should be noted that there are practical limitations to
detecting unexpected encapsulation (see section 5.1.1). detecting unexpected encapsulation (see section 5.1.1).
o Entry criteria: A MEP receives a CC-V pro-active packet with o Entry criteria: A MEP receives a CC-V pro-active packet with
the expected globally unique Source MEP identifier but with the expected globally unique Source MEP identifier but with
an unexpected encapsulation. an unexpected encapsulation.
o Exit criteria: The sink MEP does not receive any pro-active o Exit criteria: The sink MEP does not receive any pro-active
CC-V OAM packet with the expected globally unique Source MEP CC-V OAM packet with the expected globally unique Source MEP
identifier and an unexpected encapsulation for an interval identifier and an unexpected encapsulation for an interval
equal at least to 3.5 times the longest transmission period equal at least to 3.5 times the longest transmission period
of the pro-active CC-V OAM packets received with the expected of the pro-active CC-V OAM packets received with the expected
globally unique Source MEP identifier and an unexpected globally unique Source MEP identifier and an unexpected
encapsulation since this defect has been raised. encapsulation since this defect has been raised.
5.1.2. Consequent action 5.1.2. Consequent action
A sink MEP that detects any of the defect conditions defined in A sink MEP that detects any of the defect conditions defined in
section 5.1.1 declares a defect condition and performs the section 5.1.1 declares a defect condition and performs the
following consequent actions. following consequent actions.
If a MEP detects an unexpected globally unique Source MEP If a MEP detects a mis-connectivity defect, it blocks all the
Identifier, it blocks all the traffic (including also the user traffic (including also the user data packets) that it receives
data packets) that it receives from the misconnected transport from the misconnected transport path.
path.
If a MEP detects LOC defect that is not caused by a period If a MEP detects LOC defect that is not caused by a period
mis-configuration, it should block all the traffic (including mis-configuration, it should block all the traffic (including
also the user data packets) that it receives from the transport also the user data packets) that it receives from the transport
path, if this consequent action has been enabled by the path, if this consequent action has been enabled by the
operator. operator.
It is worth noticing that the OAM requirements document [11] It is worth noticing that the OAM requirements document [11]
recommends that CC-V proactive monitoring be enabled on every recommends that CC-V proactive monitoring be enabled on every
MEG in order to reliably detect connectivity defects. However, MEG in order to reliably detect connectivity defects. However,
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a consequent wrong traffic delivering. For these reasons, the a consequent wrong traffic delivering. For these reasons, the
traffic block consequent action is applied even when a LOC traffic block consequent action is applied even when a LOC
condition occurs. This block consequent action can be disabled condition occurs. This block consequent action can be disabled
through configuration. This deactivation of the block action may through configuration. This deactivation of the block action may
be used for activating or deactivating the monitoring when it is be used for activating or deactivating the monitoring when it is
not possible to synchronize the function activation of the two not possible to synchronize the function activation of the two
peer MEPs. peer MEPs.
If a MEP detects a LOC defect (section 5.1.1.1), a If a MEP detects a LOC defect (section 5.1.1.1), a
mis-connectivity defect (section 5.1.1.2) it declares a signal mis-connectivity defect (section 5.1.1.2) it declares a signal
fail condition at the transport path level. fail condition of the ME.
It is a matter if local policy if a MEP that detects a period It is a matter if local policy if a MEP that detects a period
misconfiguration defect (section 5.1.1.3) declares a signal fail misconfiguration defect (section 5.1.1.3) declares a signal fail
condition at the transport path level. condition of the ME.
The detection of an unexpected encapsulation defect does not The detection of an unexpected encapsulation defect does not
have any consequent action: it is just a warning for the network have any consequent action: it is just a warning for the network
operator. An implementation able to detect an unexpected operator. An implementation able to detect an unexpected
encapsulation but not able to verify the source MEP ID may encapsulation but not able to verify the source MEP ID may
choose to declare a mis-connectivity defect. choose to declare a mis-connectivity defect.
5.1.3. Configuration considerations 5.1.3. Configuration considerations
At all MEPs inside a MEG, the following configuration At all MEPs inside a MEG, the following configuration
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5.1.3. Configuration considerations 5.1.3. Configuration considerations
At all MEPs inside a MEG, the following configuration At all MEPs inside a MEG, the following configuration
information needs to be configured when a proactive CC-V information needs to be configured when a proactive CC-V
function is enabled: function is enabled:
o MEG ID; the MEG identifier to which the MEP belongs; o MEG ID; the MEG identifier to which the MEP belongs;
o MEP-ID; the MEP's own identity inside the MEG; o MEP-ID; the MEP's own identity inside the MEG;
o list of the other MEPs in the MEG. For a point-to-point MEG o list of the other MEPs in the MEG. For a point-to-point MEG
the list would consist of the single MEP ID from which the the list would consist of the single MEP ID from which the
OAM packets are expected. In case of the root MEP of a p2mp OAM packets are expected. In case of the root MEP of a p2mp
MEG, the list is composed by all the leaf MEP IDs inside the MEG, the list is composed by all the leaf MEP IDs inside the
MEG. In case of the leaf MEP of a p2mp MEG, the list is MEG. In case of the leaf MEP of a p2mp MEG, the list is
composed by the root MEP ID (i.e. each leaf needs to know the composed by the root MEP ID (i.e. each leaf needs to know the
root MEP ID from which it expect to receive the CC-V OAM root MEP ID from which it expect to receive the CC-V OAM
packets). packets).
o PHB; it identifies the per-hop behavior of CC-V packet. o PHB for E-LSPs; it identifies the per-hop behavior of CC-V
Proactive CC-V packets are transmitted with the "minimum loss packet. Proactive CC-V packets are transmitted with the
probability PHB" previously configured within a single "minimum loss probability PHB" previously configured within a
network operator. This PHB is configurable on network single network operator. This PHB is configurable on network
operator's basis. PHBs can be translated at the network operator's basis. PHBs can be translated at the network
borders. borders.
o transmission rate; the default CC-V transmission periods are o transmission rate; the default CC-V transmission periods are
application dependent (depending on whether they are used to application dependent (depending on whether they are used to
support fault management, performance monitoring, or support fault management, performance monitoring, or
protection switching applications): protection switching applications):
o Fault Management: default transmission period is 1s (i.e. o Fault Management: default transmission period is 1s (i.e.
transmission rate of 1 packet/second). transmission rate of 1 packet/second).
o Performance Monitoring: default transmission period is o Performance Monitoring: default transmission period is
100ms (i.e. transmission rate of 10 packets/second). 100ms (i.e. transmission rate of 10 packets/second).
Performance monitoring is only relevant when the Performance monitoring is only relevant when the
transport path is defect free. CC-V contributes to the transport path is defect free. CC-V contributes to the
accuracy of PM statistics by permitting the defect free accuracy of PM statistics by permitting the defect free
periods to be properly distinguished. periods to be properly distinguished.
o Protection Switching: default transmission period is o Protection Switching: default transmission period is
3.33ms (i.e. transmission rate of 300 packets/second), in 3.33ms (i.e. transmission rate of 300 packets/second).
order to achieve sub-50ms the CC-V defect entry criteria CC-V defect entry criteria can resolve in less than 12ms,
should resolve in less than 10msec, and complete a and a protection switch can complete within a subsequent
protection switch within a subsequent period of 50 msec. period of 50 ms.
It is also possible to lengthen the transmission period It is also possible to lengthen the transmission period
to 10ms (i.e. transmission rate of 100 packets/second): to 10ms (i.e. transmission rate of 100 packets/second):
in this case the CC-V defect entry criteria is reached in this case the CC-V defect entry criteria is reached
later (i.e. 30msec). later (i.e. 35ms).
It should be possible for the operator to configure these It should be possible for the operator to configure these
transmission rates for all applications, to satisfy his internal transmission rates for all applications, to satisfy his internal
requirements. requirements.
Note that the reception period is the same as the configured Note that the reception period is the same as the configured
transmission rate. transmission rate.
For statically provisioned transport paths the above parameters For management provisioned transport paths the above parameters
are statically configured; for dynamically established transport are statically configured; for dynamically signalled transport
paths the configuration information are signaled via the control paths the configuration information are distributed via the
plane. control plane.
The operator should be able to enable/disable some of the The operator should be able to enable/disable some of the
consequent actions. Which consequent action can be consequent actions. Which consequent action can be
enabled/disabled are described in section 5.1.1.4. enabled/disabled are described in section 5.1.1.4.
5.2. Remote Defect Indication 5.2. Remote Defect Indication
The Remote Defect Indication (RDI) function, as required in The Remote Defect Indication (RDI) function, as required in
section 2.2.9 of RFC 5860 [11], is an indicator that is section 2.2.9 of RFC 5860 [11], is an indicator that is
transmitted by a sink MEP to communicate to its source MEP that transmitted by a sink MEP to communicate to its source MEP that
a signal fail condition exists. RDI is only used for all a signal fail condition exists. In case of co-routed and
co-routed and associated bidirectional transport paths and is associated bidirectional transport paths, RDI is associated with
associated with proactive CC-V. The RDI indicator can be piggy- proactive CC-V and the RDI indicator can be piggy-backed onto
backed onto the CC-V packet. the CC-V packet. In case of unidirectional transport paths, the
RDI indicator can be sent only using an out-of-band return path
if it exists and its usage is enabled by policy actions.
When a MEP detects a signal fail condition (e.g. in case of a When a MEP detects a signal fail condition (e.g. in case of a
continuity or connectivity defect), it should begin transmitting continuity or connectivity defect), it should begin transmitting
an RDI indicator to its peer MEP. When incorporated into CC-V, an RDI indicator to its peer MEP. When incorporated into CC-V,
the RDI information will be included in all pro-active CC-V the RDI information will be included in all pro-active CC-V
packets that it generates for the duration of the signal fail packets that it generates for the duration of the signal fail
condition's existence. condition's existence.
A MEP that receives packets from a peer MEP with the RDI A MEP that receives packets from a peer MEP with the RDI
information should determine that its peer MEP has encountered a information should determine that its peer MEP has encountered a
defect condition associated with a signal fail. defect condition associated with a signal fail condition.
MIPs as well as intermediate nodes not supporting MPLS-TP OAM MIPs as well as intermediate nodes not supporting MPLS-TP OAM
are transparent to the RDI indicator and forward OAM packets are transparent to the RDI indicator and forward OAM packets
that include the RDI indicator as regular data packets, i.e. the that include the RDI indicator as regular data packets, i.e. the
MIP should not perform any actions nor examine the indicator. MIP should not perform any actions nor examine the indicator.
When the signal fail defect condition clears, the MEP should When the signal fail condition clears, the MEP should stop
stop transmitting the RDI indicator to its peer MEP. When transmitting the RDI indicator to its peer MEP. When
incorporated into CC-V, the RDI indicator will be cleared from incorporated into CC-V, the RDI indicator will be cleared from
subsequent transmission of pro-active CC-V packets. A MEP subsequent transmission of pro-active CC-V packets. A MEP
should clear the RDI defect upon reception of an RDI indicator should clear the RDI defect upon reception of an RDI indicator
cleared. cleared.
5.2.1. Configuration considerations 5.2.1. Configuration considerations
In order to support RDI indication, the indication may be a In order to support RDI indication, the indication may be a
unique OAM message or an OAM information element embedded in a unique OAM message or an OAM information element embedded in a
CV message; the RDI transmission rate and PHB of the OAM packets CV message. The in-band RDI transmission rate and PHB of the OAM
carrying RDI should be the same as that configured for CC-V. packets carrying RDI should be the same as that configured for
CC-V. Methods of the out-of-band return paths will dictate how
out-of-band RDI indications are transmitted.
5.3. Alarm Reporting 5.3. Alarm Reporting
The Alarm Reporting function, as required in section 2.2.8 of The Alarm Reporting function, as required in section 2.2.8 of
RFC 5860 [11], relies upon an Alarm Indication Signal (AIS) RFC 5860 [11], relies upon an Alarm Indication Signal (AIS)
message to suppress alarms following detection of defect message to suppress alarms following detection of defect
conditions at the server (sub-)layer. conditions at the server (sub-)layer.
When a server MEP asserts signal fail, it notifies that to the When a server MEP asserts a signal fail condition, it notifies
co-located MPLS-TP client/server adaptation function which then that to the co-located MPLS-TP client/server adaptation function
generates packets with AIS information in the downstream which then generates OAM packets with AIS information in the
direction to allow the suppression of secondary alarms at the downstream direction to allow the suppression of secondary
MPLS-TP MEP in the client (sub-)layer. alarms at the MPLS-TP MEP in the client (sub-)layer.
The generation of packets with AIS information starts The generation of packets with AIS information starts
immediately when the server MEP asserts signal fail. These immediately when the server MEP asserts a signal fail condition.
periodic packets, with AIS information, continue to be These periodic OAM packets, with AIS information, continue to be
transmitted until the signal fail condition is cleared. It is transmitted until the signal fail condition is cleared.
assumed that to avoid spurious alarm generation a MEP detecting
loss of continuity will wait for a hold off interval prior to
asserting an alarm to the management system.
Upon receiving a packet with AIS information an MPLS-TP MEP It is assumed that to avoid spurious alarm generation a MEP
enters an AIS defect condition and suppresses loss of continuity detecting a loss of continuity defect (see section 5.1.1.1) will
alarms associated with its peer MEP but does not block traffic wait for a hold off interval prior to asserting an alarm to the
received from the transport path. A MEP resumes loss of management system. Therefore, upon receiving an OAM packet with
continuity alarm generation upon detecting loss of continuity AIS information an MPLS-TP MEP enters an AIS defect condition
defect conditions in the absence of AIS condition. and suppresses loss of continuity alarms associated with its
peer MEP but does not block traffic received from the transport
path. A MEP resumes loss of continuity alarm generation upon
detecting loss of continuity defect conditions in the absence of
AIS condition.
MIPs, as well as intermediate nodes, do not process AIS MIPs, as well as intermediate nodes, do not process AIS
information and forward these AIS OAM packets as regular data information and forward these AIS OAM packets as regular data
packets. packets.
For example, let's consider a fiber cut between LSR 1 and LSR 2 For example, let's consider a fiber cut between LSR 1 and LSR 2
in the reference network of Figure 5. Assuming that all of the in the reference network of Figure 5. Assuming that all of the
MEGs described in Figure 5 have pro-active CC-V enabled, a LOC MEGs described in Figure 5 have pro-active CC-V enabled, a LOC
defect is detected by the MEPs of Sec12 SME, LSP13 LME, PW1 PSME defect is detected by the MEPs of Sec12 SMEG LSP13 LMEG, PW1
and PW1Z PME, however in a transport network only the alarm PSMEG and PW1Z PMEG, however in a transport network only the
associated to the fiber cut needs to be reported to an NMS while alarm associated to the fiber cut needs to be reported to an NMS
all secondary alarms should be suppressed (i.e. not reported to while all secondary alarms should be suppressed (i.e. not
the NMS or reported as secondary alarms). reported to the NMS or reported as secondary alarms).
If the fiber cut is detected by the MEP in the physical layer If the fiber cut is detected by the MEP in the physical layer
(in LSR2), LSR2 can generate the proper alarm in the physical (in LSR2), LSR2 can generate the proper alarm in the physical
layer and suppress the secondary alarm associated with the LOC layer and suppress the secondary alarm associated with the LOC
defect detected on Sec12 SME. As both MEPs reside within the defect detected on Sec12 SMEG. As both MEPs reside within the
same node, this process does not involve any external protocol same node, this process does not involve any external protocol
exchange. Otherwise, if the physical layer has not enough OAM exchange. Otherwise, if the physical layer has not enough OAM
capabilities to detect the fiber cut, the MEP of Sec12 SME in capabilities to detect the fiber cut, the MEP of Sec12 SMEG in
LSR2 will report a LOC alarm. LSR2 will report a LOC alarm.
In both cases, the MEP of Sec12 SME in LSR 2 notifies the In both cases, the MEP of Sec12 SMEG in LSR 2 notifies the
adaptation function for LSP13 LME that then generates AIS adaptation function for LSP13 LMEG that then generates AIS
packets on the LSP13 LME in order to allow its MEP in LSR3 to packets on the LSP13 LMEG in order to allow its MEP in LSR3 to
suppress the LOC alarm. LSR3 can also suppress the secondary suppress the LOC alarm. LSR3 can also suppress the secondary
alarm on PW13 PSME because the MEP of PW13 PSME resides within alarm on PW13 PSMEG because the MEP of PW13 PSMEG resides within
the same node as the MEP of LSP13 LME. The MEP of PW13 PSME in the same node as the MEP of LSP13 LMEG. The MEP of PW13 PSMEG in
LSR3 also notifies the adaptation function for PW1Z PME that LSR3 also notifies the adaptation function for PW1Z PMEG that
then generates AIS packets on PW1Z PME in order to allow its MEP then generates AIS packets on PW1Z PMEG in order to allow its
in LSRZ to suppress the LOC alarm. MEP in LSRZ to suppress the LOC alarm.
The generation of AIS packets for each MEG in the MPLS-TP client The generation of AIS packets for each MEG in the MPLS-TP client
(sub-)layer is configurable (i.e. the operator can (sub-)layer is configurable (i.e. the operator can
enable/disable the AIS generation). enable/disable the AIS generation).
AIS packets are transmitted with the "minimum loss probability AIS packets are transmitted with the "minimum loss probability
PHB" within a single network operator. This PHB is configurable PHB" within a single network operator. For E-LSPs, this PHB is
on network operator's basis. configurable on network operator's basis, while for L-LSPs, this
is determined as per RFC 3270 [22].
AIS condition is cleared if no AIS message has been received in AIS condition is cleared if no AIS message has been received in
3.5 times the AIS transmission period. 3.5 times the AIS transmission period.
5.4. Lock Reporting 5.4. Lock Reporting
The Lock Reporting function, as required in section 2.2.7 of RFC The Lock Reporting function, as required in section 2.2.7 of RFC
5860 [11], relies upon a Locked Report (LKR) message used to 5860 [11], relies upon a Locked Report (LKR) message used to
suppress alarms following administrative locking action in the suppress alarms following administrative locking action in the
server (sub-)layer. server (sub-)layer.
When a server MEP is locked, the MPLS-TP client (sub-)layer When a server MEP is locked, the MPLS-TP client (sub-)layer
adaptation function generates packets with LKR information in adaptation function generates packets with LKR information to
both directions to allow the suppression of secondary alarms at allow the suppression of secondary alarms at the MEPs in the
the MEPs in the client (sub-)layer. Again it is assumed that client (sub-)layer. Again it is assumed that there is a hold off
there is a hold off for any loss of continuity alarms in the for any loss of continuity alarms in the client layer MEPs
client layer MEPs downstream of the node originating the locked downstream of the node originating the locked report. In case of
report. client (sub-)layer co-routed bidirectional transport paths, the
LKR information is sent on both directions. In case of client
(sub-)layer unidirectional transport paths, the LKR information
is sent only in the downstream direction. As a consequence, in
case of client (sub-)layer point-to-multipoint transport paths,
the LKR information is sent only to the MEPs that are downstream
to the server (sub-)layer that has been administratively locked.
Client (sub-)layer associated bidirectional transport paths
behave like co-routed bidirectional transport paths if the
server (sub-)layer that has been administratively locked is used
by both directions; otherwise they behave like unidirectional
transport paths.
The generation of packets with LKR information starts The generation of packets with LKR information starts
immediately when the server MEP is locked. These periodic immediately when the server MEP is locked. These periodic
packets, with LKR information, continue to be transmitted until packets, with LKR information, continue to be transmitted until
the locked condition is cleared. the locked condition is cleared.
Upon receiving a packet with LKR information an MPLS-TP MEP Upon receiving a packet with LKR information an MPLS-TP MEP
enters an LKR defect condition and suppresses loss of continuity enters an LKR defect condition and suppresses loss of continuity
alarm associated with its peer MEP but does not block traffic alarm associated with its peer MEP but does not block traffic
received from the transport path. A MEP resumes loss of received from the transport path. A MEP resumes loss of
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MIPs, as well as intermediate nodes, do not process the LKR MIPs, as well as intermediate nodes, do not process the LKR
information and forward these LKR OAM packets as regular data information and forward these LKR OAM packets as regular data
packets. packets.
For example, let's consider the case where the MPLS-TP Section For example, let's consider the case where the MPLS-TP Section
between LSR 1 and LSR 2 in the reference network of Figure 5 is between LSR 1 and LSR 2 in the reference network of Figure 5 is
administrative locked at LSR2 (in both directions). administrative locked at LSR2 (in both directions).
Assuming that all the MEGs described in Figure 5 have pro-active Assuming that all the MEGs described in Figure 5 have pro-active
CC-V enabled, a LOC defect is detected by the MEPs of LSP13 LME, CC-V enabled, a LOC defect is detected by the MEPs of LSP13
PW1 PSME and PW1Z PME, however in a transport network all these LMEG, PW1 PSMEG and PW1Z PMEG, however in a transport network
secondary alarms should be suppressed (i.e. not reported to the all these secondary alarms should be suppressed (i.e. not
NMS or reported as secondary alarms). reported to the NMS or reported as secondary alarms).
The MEP of Sec12 SME in LSR 2 notifies the adaptation function The MEP of Sec12 SMEG in LSR 2 notifies the adaptation function
for LSP13 LME that then generates LKR packets on the LSP13 LME for LSP13 LMEG that then generates LKR packets on the LSP13 LMEG
in order to allow its MEPs in LSR1 and LSR3 to suppress the LOC in order to allow its MEPs in LSR1 and LSR3 to suppress the LOC
alarm. LSR3 can also suppress the secondary alarm on PW13 PSME alarm. LSR3 can also suppress the secondary alarm on PW13 PSMEG
because the MEP of PW13 PSME resides within the same node as the because the MEP of PW13 PSMEG resides within the same node as
MEP of LSP13 LME. The MEP of PW13 PSME in LSR3 also notifies the the MEP of LSP13 LMEG. The MEP of PW13 PSMEG in LSR3 also
adaptation function for PW1Z PME that then generates AIS packets notifies the adaptation function for PW1Z PMEG that then
on PW1Z PME in order to allow its MEP in LSRZ to suppress the generates AIS packets on PW1Z PMEG in order to allow its MEP in
LOC alarm. LSRZ to suppress the LOC alarm.
The generation of LKR packets for each MEG in the MPLS-TP client The generation of LKR packets for each MEG in the MPLS-TP client
(sub-)layer is configurable (i.e. the operator can (sub-)layer is configurable (i.e. the operator can
enable/disable the LKR generation). enable/disable the LKR generation).
LKR packets are transmitted with the "minimum loss probability LKR packets are transmitted with the "minimum loss probability
PHB" within a single network operator. This PHB is configurable PHB" within a single network operator. For E-LSPs, this PHB is
on network operator's basis. configurable on network operator's basis, while for L-LSPs, this
is determined as per RFC 3270 [22].
Locked condition is cleared if no LKR packet has been received Locked condition is cleared if no LKR packet has been received
for 3.5 times the transmission period. for 3.5 times the transmission period.
5.5. Packet Loss Measurement 5.5. Packet Loss Measurement
Packet Loss Measurement (LM) is one of the capabilities Packet Loss Measurement (LM) is one of the capabilities
supported by the MPLS-TP Performance Monitoring (PM) function in supported by the MPLS-TP Performance Monitoring (PM) function in
order to facilitate reporting of QoS information for a transport order to facilitate reporting of QoS information for a transport
path as required in section 2.2.11 of RFC 5860 [11]. LM is used path as required in section 2.2.11 of RFC 5860 [11]. LM is used
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Proactive LM is performed by periodically sending LM OAM packets Proactive LM is performed by periodically sending LM OAM packets
from a MEP to a peer MEP and by receiving LM OAM packets from from a MEP to a peer MEP and by receiving LM OAM packets from
the peer MEP (if a co-routed or associated bidirectional the peer MEP (if a co-routed or associated bidirectional
transport path) during the life time of the transport path. Each transport path) during the life time of the transport path. Each
MEP performs measurements of its transmitted and received MEP performs measurements of its transmitted and received
packets. These measurements are then correlated in real time packets. These measurements are then correlated in real time
with the peer MEP in the ME to derive the impact of packet loss with the peer MEP in the ME to derive the impact of packet loss
on a number of performance metrics for the ME in the MEG. The LM on a number of performance metrics for the ME in the MEG. The LM
transactions are issued such that the OAM packets will transactions are issued such that the OAM packets will
experience the same queuing discipline as the measured traffic experience the same PHB scheduling class as the measured traffic
while transiting between the MEPs in the ME. while transiting between the MEPs in the ME.
For a MEP, near-end packet loss refers to packet loss associated For a MEP, near-end packet loss refers to packet loss associated
with incoming data packets (from the far-end MEP) while far-end with incoming data packets (from the far-end MEP) while far-end
packet loss refers to packet loss associated with egress data packet loss refers to packet loss associated with egress data
packets (towards the far-end MEP). packets (towards the far-end MEP).
Pro-active LM can be operated in two ways:
o One-way: a MEP sends LM OAM packet to its peer MEP containing
all the required information to facilitate near-end packet
loss measurements at the peer MEP.
o Two-way: a MEP sends LM OAM packet with a LM request to its
peer MEP, which replies with a LM OAM packet as a LM
response. The request/response LM OAM packets containing all
the required information to facilitate both near-end and
far-end packet loss measurements from the viewpoint of the
originating MEP.
One-way LM is applicable to both unidirectional and
bidirectional (co-routed or associated) transport paths while
two-way LM is applicable only to bidirectional (co-routed or
associated) transport paths.
MIPs, as well as intermediate nodes, do not process the LM MIPs, as well as intermediate nodes, do not process the LM
information and forward these pro-active LM OAM packets as information and forward these pro-active LM OAM packets as
regular data packets. regular data packets.
5.5.1. Configuration considerations 5.5.1. Configuration considerations
In order to support proactive LM, the transmission rate and PHB In order to support proactive LM, the transmission rate and PHB
class associated with the LM OAM packets originating from a MEP class associated with the LM OAM packets originating from a MEP
need be configured as part of the LM provisioning. LM OAM need be configured as part of the LM provisioning. LM OAM
packets should be transmitted with the PHB that yields the packets should be transmitted with the PHB that yields the
lowest discard probability within the measured PHB Scheduling lowest drop precedence within the measured PHB Scheduling Class
Class (see RFC 3260 [16]). (see RFC 3260 [16]).
If that PHB class is not an ordered aggregate where the ordering If that PHB class is not an ordered aggregate where the ordering
constraint is all packets with the PHB class being delivered in constraint is all packets with the PHB class being delivered in
order, LM can produce inconsistent results. order, LM can produce inconsistent results.
5.5.2. Sampling skew 5.5.2. Sampling skew
If an implementation makes use of a hardware forwarding path If an implementation makes use of a hardware forwarding path
which operates in parallel with an OAM processing path, whether which operates in parallel with an OAM processing path, whether
hardware or software based, the packet and byte counts may be hardware or software based, the packet and byte counts may be
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variation in the transport path monitored by a pair of MEPs. variation in the transport path monitored by a pair of MEPs.
Proactive DM is performed by sending periodic DM OAM packets Proactive DM is performed by sending periodic DM OAM packets
from a MEP to a peer MEP and by receiving DM OAM packets from from a MEP to a peer MEP and by receiving DM OAM packets from
the peer MEP (if a co-routed or associated bidirectional the peer MEP (if a co-routed or associated bidirectional
transport path) during a configurable time interval. transport path) during a configurable time interval.
Pro-active DM can be operated in two ways: Pro-active DM can be operated in two ways:
o One-way: a MEP sends DM OAM packet to its peer MEP containing o One-way: a MEP sends DM OAM packet to its peer MEP containing
all the required information to facilitate one-way packet all the required information to facilitate one-way packet
delay and/or one-way packet delay variation measurements at delay and/or one-way packet delay variation measurements at
the peer MEP. Note that this requires synchronized precision the peer MEP. Note that this requires precise time
time at either MEP by means outside the scope of this synchronisation at either MEP by means outside the scope of
framework. this framework.
o Two-way: a MEP sends DM OAM packet with a DM request to its o Two-way: a MEP sends DM OAM packet with a DM request to its
peer MEP, which replies with a DM OAM packet as a DM peer MEP, which replies with a DM OAM packet as a DM
response. The request/response DM OAM packets containing all response. The request/response DM OAM packets containing all
the required information to facilitate two-way packet delay the required information to facilitate two-way packet delay
and/or two-way packet delay variation measurements from the and/or two-way packet delay variation measurements from the
viewpoint of the source MEP. viewpoint of the originating MEP.
One-way DM is applicable to both unidirectional and
bidirectional (co-routed or associated) transport paths while
two-way DM is applicable only to bidirectional (co-routed or
associated) transport paths.
MIPs, as well as intermediate nodes, do not process the DM MIPs, as well as intermediate nodes, do not process the DM
information and forward these pro-active DM OAM packets as information and forward these pro-active DM OAM packets as
regular data packets. regular data packets.
5.6.1. Configuration considerations 5.6.1. Configuration considerations
In order to support pro-active DM, the transmission rate and PHB In order to support pro-active DM, the transmission rate and,
associated with the DM OAM packets originating from a MEP need for E-LSPs, the PHB associated with the DM OAM packets
be configured as part of the DM provisioning. DM OAM packets originating from a MEP need be configured as part of the DM
should be transmitted with the PHB that yields the lowest provisioning. DM OAM packets should be transmitted with the PHB
discard probability within the measured PHB Scheduling Class that yields the lowest drop precedence within the measured PHB
(see RFC 3260 [16]). Scheduling Class (see RFC 3260 [16]).
5.7. Client Failure Indication 5.7. Client Failure Indication
The Client Failure Indication (CFI) function, as required in The Client Failure Indication (CFI) function, as required in
section 2.2.10 of RFC 5860 [11], is used to help process client section 2.2.10 of RFC 5860 [11], is used to help process client
defects and propagate a client signal defect condition from the defects and propagate a client signal defect condition from the
process associated with the local attachment circuit where the process associated with the local attachment circuit where the
defect was detected (typically the source adaptation function defect was detected (typically the source adaptation function
for the local client interface) to the process associated with for the local client interface) to the process associated with
the far-end attachment circuit (typically the source adaptation the far-end attachment circuit (typically the source adaptation
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transport path, the CFI message requires additional information transport path, the CFI message requires additional information
to permit the client instance to be identified. to permit the client instance to be identified.
MIPs, as well as intermediate nodes, do not process the CFI MIPs, as well as intermediate nodes, do not process the CFI
information and forward these pro-active CFI OAM packets as information and forward these pro-active CFI OAM packets as
regular data packets. regular data packets.
5.7.1. Configuration considerations 5.7.1. Configuration considerations
In order to support CFI indication, the CFI transmission rate In order to support CFI indication, the CFI transmission rate
and PHB of the CFI OAM message/information element should be and, for E-LSPs, the PHB of the CFI OAM message/information
configured as part of the CFI configuration. element should be configured as part of the CFI configuration.
6. OAM Functions for on-demand monitoring 6. OAM Functions for on-demand monitoring
In contrast to proactive monitoring, on-demand monitoring is In contrast to proactive monitoring, on-demand monitoring is
initiated manually and for a limited amount of time, usually for initiated manually and for a limited amount of time, usually for
operations such as diagnostics to investigate a defect operations such as diagnostics to investigate a defect
condition. condition.
On-demand monitoring covers a combination of "in-service" and On-demand monitoring covers a combination of "in-service" and
"out-of-service" monitoring functions. The control and "out-of-service" monitoring functions. The control and
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(e.g., data plane loopback) and the issuance of notifications (e.g., data plane loopback) and the issuance of notifications
into client layers of the transport path being removed from into client layers of the transport path being removed from
service (e.g., lock-reporting) service (e.g., lock-reporting)
3. The measurements resulting from on-demand monitoring are 3. The measurements resulting from on-demand monitoring are
typically harvested in real time, as these are frequently typically harvested in real time, as these are frequently
initiated manually. These do not necessarily require initiated manually. These do not necessarily require
different harvesting mechanisms that for harvesting proactive different harvesting mechanisms that for harvesting proactive
monitoring telemetry. monitoring telemetry.
The functions that are exclusive out-of-service are those The functions that are exclusively out-of-service are those
described in section 6.3. The remainder are applicable to both described in section 6.3. The remainder are applicable to both
in-service and out-of-service transport paths. in-service and out-of-service transport paths.
6.1. Connectivity Verification 6.1. Connectivity Verification
In order to preserve network resources, e.g. bandwidth, On demand connectivity verification function, as required in
processing time at switches, it may be preferable to not use section 2.2.3 of RFC 5860 [11], is a transaction that flows from
proactive CC-V. In order to perform fault management functions, the originating MEP to a target MIP or MEP to verify the
network management may invoke periodic on-demand bursts of on- connectivity between these points.
demand CV packets, as required in section 2.2.3 of RFC 5860
[11].
On demand connectivity verification is a transaction that flows
from the source MEP to a target MIP or MEP.
Use of on-demand CV is dependent on the existence of either a Use of on-demand CV is dependent on the existence of either a
bi-directional ME, or an associated return ME, or the bi-directional ME, or an associated return ME, or the
availability of an out-of-band return path because it requires availability of an out-of-band return path because it requires
the ability for target MIPs and MEPs to direct responses to the the ability for target MIPs and MEPs to direct responses to the
originating MEPs. originating MEPs.
In order to preserve network resources, e.g. bandwidth,
processing time at switches, it may be preferable to not use
proactive CC-V. In order to perform fault management functions,
network management may invoke periodic on-demand bursts of on-
demand CV packets.
An additional use of on-demand CV would be to detect and locate An additional use of on-demand CV would be to detect and locate
a problem of connectivity when a problem is suspected or known a problem of connectivity when a problem is suspected or known
based on other tools. In this case the functionality will be based on other tools. In this case the functionality will be
triggered by the network management in response to a status triggered by the network management in response to a status
signal or alarm indication. signal or alarm indication.
On-demand CV is based upon generation of on-demand CV packets On-demand CV is based upon generation of on-demand CV packets
that should uniquely identify the MEG that is being checked. that should uniquely identify the MEG that is being checked.
The on-demand functionality may be used to check either an The on-demand functionality may be used to check either an
entire MEG (end-to-end) or between a source MEP and a specific entire MEG (end-to-end) or between the originating MEP and a
MIP. This functionality may not be available for associated specific MIP. This functionality may not be available for
bidirectional transport paths or unidirectional paths, as the associated bidirectional transport paths or unidirectional
MIP may not have a return path to the source MEP for the on- paths, as the MIP may not have a return path to the originating
demand CV transaction. MEP for the on-demand CV transaction.
On-demand CV may generate a one-time burst of on-demand CV On-demand CV may generate a one-time burst of on-demand CV
packets, or be used to invoke periodic, non-continuous, bursts packets, or be used to invoke periodic, non-continuous, bursts
of on-demand CV packets. The number of packets generated in of on-demand CV packets. The number of packets generated in
each burst is configurable at the MEPs, and should take into each burst is configurable at the MEPs, and should take into
account normal packet-loss conditions. account normal packet-loss conditions.
When invoking a periodic check of the MEG, the source MEP should When invoking a periodic check of the MEG, the originating MEP
issue a burst of on-demand CV packets that uniquely identifies should issue a burst of on-demand CV packets that uniquely
the MEG being verified. The number of packets and their identifies the MEG being verified. The number of packets and
transmission rate should be pre-configured at the source MEP. their transmission rate should be pre-configured at the
The source MEP should use the mechanisms defined in sections 3.3 originating MEP. The source MEP should use the mechanisms
and 3.4 when sending an on-demand CV packet to a target MEP or defined in sections 3.3 and 3.4 when sending an on-demand CV
target MIP respectively. The target MEP/MIP shall return a reply packet to a target MEP or target MIP respectively. The target
on-demand CV packet for each packet received. If the expected MEP/MIP shall return a reply on-demand CV packet for each packet
number of on-demand CV reply packets is not received at source received. If the expected number of on-demand CV reply packets
MEP, this is an indication that a connectivity problem may is not received at originating MEP, this is an indication that a
exist. connectivity problem may exist.
On-demand CV should have the ability to carry padding such that On-demand CV should have the ability to carry padding such that
a variety of MTU sizes can be originated to verify the MTU a variety of MTU sizes can be originated to verify the MTU
transport capability of the transport path. transport capability of the transport path.
MIPs that are not target by on-demand CV packets, as well as MIPs that are not targeted by on-demand CV packets, as well as
intermediate nodes, do not process the CV information and intermediate nodes, do not process the CV information and
forward these on-demand CV OAM packets as regular data packets. forward these on-demand CV OAM packets as regular data packets.
6.1.1. Configuration considerations 6.1.1. Configuration considerations
For on-demand CV the source MEP should support the configuration For on-demand CV the originating MEP should support the
of the number of packets to be transmitted/received in each configuration of the number of packets to be
burst of transmissions and their packet size. transmitted/received in each burst of transmissions and their
packet size.
In addition, when the CV packet is used to check connectivity In addition, when the CV packet is used to check connectivity
toward a target MIP, the number of hops to reach the target MIP toward a target MIP, the number of hops to reach the target MIP
should be configured. should be configured.
The PHB of the on-demand CV packets should be configured as For E-LSPs, the PHB of the on-demand CV packets should be
well. This permits the verification of correct operation of QoS configured as well. This permits the verification of correct
queuing as well as connectivity. operation of QoS queuing as well as connectivity.
6.2. Packet Loss Measurement 6.2. Packet Loss Measurement
On-demand Packet Loss Measurement (LM) is one of the On-demand Packet Loss Measurement (LM) is one of the
capabilities supported by the MPLS-TP Performance Monitoring capabilities supported by the MPLS-TP Performance Monitoring
function in order to facilitate the diagnosis of QoS function in order to facilitate the diagnosis of QoS
performances for a transport path, as required in section 2.2.11 performances for a transport path, as required in section 2.2.11
of RFC 5860 [11]. As proactive LM, on-demand LM is used to of RFC 5860 [11]. As proactive LM, on-demand LM is used to
exchange counter values for the number of ingress and egress exchange counter values for the number of ingress and egress
packets transmitted and received by the transport path monitored packets transmitted and received by the transport path monitored
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Use of packet loss measurement in an out-of-service transport Use of packet loss measurement in an out-of-service transport
path requires a traffic source such as a tester. path requires a traffic source such as a tester.
MIPs, as well as intermediate nodes, do not process the LM MIPs, as well as intermediate nodes, do not process the LM
information and forward these on-demand LM OAM packets as information and forward these on-demand LM OAM packets as
regular data packets. regular data packets.
6.2.1. Configuration considerations 6.2.1. Configuration considerations
In order to support on-demand LM, the beginning and duration of In order to support on-demand LM, the beginning and duration of
the LM procedures, the transmission rate and PHB associated with the LM procedures, the transmission rate and, for E-LSPs, the
the LM OAM packets originating from a MEP must be configured as PHB associated with the LM OAM packets originating from a MEP
part of the on-demand LM provisioning. LM OAM packets should be must be configured as part of the on-demand LM provisioning. LM
transmitted with the PHB that yields the lowest discard OAM packets should be transmitted with the PHB that yields the
probability within the measured PHB Scheduling Class (see RFC lowest drop precedence within the measured PHB Scheduling Class
3260 [16]). (see RFC 3260 [16]).
6.2.2. Sampling skew 6.2.2. Sampling skew
If an implementation makes use of a hardware forwarding path The same considerations described in section 5.5.2 for the
which operates in parallel with an OAM processing path, whether pro-active LM are also applicable to on-demand LM
hardware or software based, the packet and byte counts may be implementations.
skewed if one or more packets can be processed before the OAM
processing samples counters. If OAM is implemented in software
this error can be quite large.
6.2.3. Multilink issues 6.2.3. Multilink issues
Multi-link Issues are as described in section 5.5.3. Multi-link Issues are as described in section 5.5.3.
6.3. Diagnostic Tests 6.3. Diagnostic Tests
Diagnostic tests are tests performed on a MEG that has been taken Diagnostic tests are tests performed on a MEG that has been taken
out-of-service. out-of-service.
6.3.1. Throughput Estimation 6.3.1. Throughput Estimation
Throughput estimation is an on-demand out-of-service function, Throughput estimation is an on-demand out-of-service function,
as required in section 2.2.5 of RFC 5860 [11], that allows as required in section 2.2.5 of RFC 5860 [11], that allows
verifying the bandwidth/throughput of an MPLS-TP transport path verifying the bandwidth/throughput of an MPLS-TP transport path
(LSP or PW) before it is put in-service. (LSP or PW) before it is put in-service.
Throughput estimation is performed between MEPs and between MEP Throughput estimation is performed between MEPs and between MEP
and MIP. It and can be performed in one-way or two-way modes. and MIP. It can be performed in one-way or two-way modes.
According to RFC 2544 [12], this test is performed by sending According to RFC 2544 [12], this test is performed by sending
OAM test packets at increasing rate (up to the theoretical OAM test packets at increasing rate (up to the theoretical
maximum), graphing the percentage of OAM test packets received maximum), computing the percentage of OAM test packets received
and reporting the rate at which OAM test packets begin to drop. and reporting the rate at which OAM test packets begin to drop.
In general, this rate is dependent on the OAM test packet size. In general, this rate is dependent on the OAM test packet size.
When configured to perform such tests, a MEP source inserts OAM When configured to perform such tests, a source MEP inserts OAM
test packets with a specified packet size and transmission test packets with a specified packet size and transmission
pattern at a rate to exercise the throughput. pattern at a rate to exercise the throughput.
For a one-way test, the remote MEP sink receives the OAM test For a one-way test, the remote sink MEP receives the OAM test
packets and calculates the packet loss. For a two-way test, the packets and calculates the packet loss. For a two-way test, the
remote MEP loopbacks the OAM test packets back to original MEP remote MEP loopbacks the OAM test packets back to original MEP
and the local MEP sink calculates the packet loss. and the local sink MEP calculates the packet loss.
It is worth noting that two-way throughput estimation can only It is worth noting that two-way throughput estimation is only
evaluate the minimum of available throughput of the two applicable to bidirectional (co-routed or associated) transport
directions. In order to estimate the throughput of each paths and can only evaluate the minimum of available throughput
direction uniquely, two one-way throughput estimation sessions of the two directions. In order to estimate the throughput of
have to be setup. each direction uniquely, two one-way throughput estimation
sessions have to be setup.
It is also worth noting that if throughput estimation is
performed on transport paths that transit oversubscribed links,
the test may not produce comprehensive results if viewed in
isolation because the impact of the test on the surrounding
traffic needs to also be considered. Moreover, the estimation
will only reflect the bandwidth available at the moment when the
measure is made.
MIPs that are not target by on-demand test OAM packets, as well MIPs that are not target by on-demand test OAM packets, as well
as intermediate nodes, do not process the throughput test as intermediate nodes, do not process the throughput test
information and forward these on-demand test OAM packets as information and forward these on-demand test OAM packets as
regular data packets. regular data packets.
6.3.1.1. Configuration considerations 6.3.1.1. Configuration considerations
Throughput estimation is an out-of-service tool. The diagnosed Throughput estimation is an out-of-service tool. The diagnosed
MEG should be put into a Lock status before the diagnostic test MEG should be put into a Lock status before the diagnostic test
skipping to change at page 48, line 16 skipping to change at page 52, line 35
using the Lock Instruct OAM tool as defined in section 7. using the Lock Instruct OAM tool as defined in section 7.
At the transmitting MEP, provisioning is required for a test At the transmitting MEP, provisioning is required for a test
signal generator, which is associated with the MEP. At a signal generator, which is associated with the MEP. At a
receiving MEP, provisioning is required for a test signal receiving MEP, provisioning is required for a test signal
detector which is associated with the MEP. detector which is associated with the MEP.
6.3.1.2. Limited OAM processing rate 6.3.1.2. Limited OAM processing rate
If an implementation is able to process payload at much higher If an implementation is able to process payload at much higher
data rates than OAM packets, then accurate measurement of data rates than OAM test packets, then accurate measurement of
throughput using OAM packets is not achievable. Whether OAM throughput using OAM test packets is not achievable. Whether
packets can be processed at the same rate as payload is OAM packets can be processed at the same rate as payload is
implementation dependent. implementation dependent.
6.3.1.3. Multilink considerations 6.3.1.3. Multilink considerations
If multilink is used, then it may not be possible to perform If multilink is used, then it may not be possible to perform
throughput measurement, as the throughput test may not have a throughput measurement, as the throughput test may not have a
mechanism for utilizing more than one component link of the mechanism for utilizing more than one component link of the
aggregated link. aggregated link.
6.3.2. Data plane Loopback 6.3.2. Data plane Loopback
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normal per hop processing such as TTL decrement. normal per hop processing such as TTL decrement.
The data plane loopback function requires that the MEG is locked The data plane loopback function requires that the MEG is locked
such that user data traffic is prevented from entering/exiting such that user data traffic is prevented from entering/exiting
that MEG. Instead, test traffic is inserted at the ingress of that MEG. Instead, test traffic is inserted at the ingress of
the MEG. This test traffic can be generated from an internal the MEG. This test traffic can be generated from an internal
process residing within the ingress node or injected by external process residing within the ingress node or injected by external
test equipment connected to the ingress node. test equipment connected to the ingress node.
It is also normal to disable proactive monitoring of the path as It is also normal to disable proactive monitoring of the path as
the source MEP will see all source MEP originated OAM messages the sink MEP will see all the OAM messages, originated by the
returned to it. associated source MEP, returned to it.
The only way to send an OAM packet to a node set in the data The only way to send an OAM packet (e.g., to remove the data
plane loopback mode is via TTL expiry, irrespectively on whether plane loopback state) to the MIPs or MEPs hosted by a node set
the node is hosting MIPs or MEPs. It should also be noted that in the data plane loopback mode is via TTL expiry. It should
MIPs can be addressed with more than one TTL value on a also be noted that MIPs can be addressed with more than one TTL
co-routed bi-directional path set into dataplane loopback. value on a co-routed bi-directional path set into dataplane
loopback.
If the loopback function is to be performed at an intermediate If the loopback function is to be performed at an intermediate
node it is only applicable to co-routed bi-directional paths. If node it is only applicable to co-routed bi-directional paths. If
the loopback is to be performed end to end, it is applicable to the loopback is to be performed end to end, it is applicable to
both co-routed bi-directional or associated bi-directional both co-routed bi-directional or associated bi-directional
paths. paths.
It should be noted that data plane loopback function itself is It should be noted that data plane loopback function itself is
applied to data-plane loopback points that can resides on applied to data-plane loopback points that can resides on
different interfaces from MIPs/MEPs. Where a node implements different interfaces from MIPs/MEPs. Where a node implements
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can be put into data plane loopback state via an NMS action or can be put into data plane loopback state via an NMS action or
using an OAM tool for data plane loopback configuration. using an OAM tool for data plane loopback configuration.
If the data plane loopback point is set somewhere at an If the data plane loopback point is set somewhere at an
intermediate point of a co-routed bidirectional transport path, intermediate point of a co-routed bidirectional transport path,
the side of loop back function (one side or both side) needs to the side of loop back function (one side or both side) needs to
be configured. be configured.
6.4. Route Tracing 6.4. Route Tracing
It is often necessary to trace a route covered by a MEG from a It is often necessary to trace a route covered by a MEG from an
source MEP to the sink MEP including all the MIPs in-between, originating MEP to the peer MEP(s) including all the MIPs in-
and may be conducted after provisioning an MPLS-TP transport between, and may be conducted after provisioning an MPLS-TP
path for, e.g., trouble shooting purposes such as fault transport path for, e.g., trouble shooting purposes such as
localization. fault localization.
The route tracing function, as required in section 2.2.4 of RFC The route tracing function, as required in section 2.2.4 of RFC
5860 [11], is providing this functionality. Based on the fate 5860 [11], is providing this functionality. Based on the fate
sharing requirement of OAM flows, i.e. OAM packets receive the sharing requirement of OAM flows, i.e. OAM packets receive the
same forwarding treatment as data packet, route tracing is a same forwarding treatment as data packet, route tracing is a
basic means to perform connectivity verification and, to a much basic means to perform connectivity verification and, to a much
lesser degree, continuity check. For this function to work lesser degree, continuity check. For this function to work
properly, a return path must be present. properly, a return path must be present.
Route tracing might be implemented in different ways and this Route tracing might be implemented in different ways and this
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defined monitoring period. defined monitoring period.
On-Demand DM is performed by sending periodic DM OAM packets On-Demand DM is performed by sending periodic DM OAM packets
from a MEP to a peer MEP and by receiving DM OAM packets from from a MEP to a peer MEP and by receiving DM OAM packets from
the peer MEP (if a co-routed or associated bidirectional the peer MEP (if a co-routed or associated bidirectional
transport path) during a configurable time interval. transport path) during a configurable time interval.
On-demand DM can be operated in two modes: On-demand DM can be operated in two modes:
o One-way: a MEP sends DM OAM packet to its peer MEP containing o One-way: a MEP sends DM OAM packet to its peer MEP containing
all the required information to facilitate one-way packet all the required information to facilitate one-way packet
delay and/or one-way packet delay variation measurements at delay and/or one-way packet delay variation measurements at
the peer MEP. Note that this requires synchronized precision the peer MEP. Note that this requires precise time
time at either MEP by means outside the scope of this synchronisation at either MEP by means outside the scope of
framework. this framework.
o Two-way: a MEP sends DM OAM packet with a DM request to its o Two-way: a MEP sends DM OAM packet with a DM request to its
peer MEP, which replies with an DM OAM packet as a DM peer MEP, which replies with an DM OAM packet as a DM
response. The request/response DM OAM packets containing all response. The request/response DM OAM packets containing all
the required information to facilitate two-way packet delay the required information to facilitate two-way packet delay
and/or two-way packet delay variation measurements from the and/or two-way packet delay variation measurements from the
viewpoint of the source MEP. viewpoint of the originating MEP.
MIPs, as well as intermediate nodes, do not process the DM MIPs, as well as intermediate nodes, do not process the DM
information and forward these on-demand DM OAM packets as information and forward these on-demand DM OAM packets as
regular data packets. regular data packets.
6.5.1. Configuration considerations 6.5.1. Configuration considerations
In order to support on-demand DM, the beginning and duration of In order to support on-demand DM, the beginning and duration of
the DM procedures, the transmission rate and PHB associated with the DM procedures, the transmission rate and, for E-LSPs, the
the DM OAM packets originating from a MEP need be configured as PHB associated with the DM OAM packets originating from a MEP
part of the DM provisioning. DM OAM packets should be need be configured as part of the DM provisioning. DM OAM
transmitted with the PHB that yields the lowest discard packets should be transmitted with the PHB that yields the
probability within the measured PHB Scheduling Class (see RFC lowest drop precedence within the measured PHB Scheduling Class
3260 [16]). (see RFC 3260 [16]).
In order to verify different performances between long and short In order to verify different performances between long and short
packets (e.g., due to the processing time), it should be packets (e.g., due to the processing time), it should be
possible for the operator to configure the packet size of the possible for the operator to configure the packet size of the
on-demand OAM DM packet. on-demand OAM DM packet.
7. OAM Functions for administration control 7. OAM Functions for administration control
7.1. Lock Instruct 7.1. Lock Instruct
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Note that if the client (sub-)layer is also MPLS-TP, Lock Note that if the client (sub-)layer is also MPLS-TP, Lock
Reporting (LKR) generation at the client MPLS-TP (sub-)layer is Reporting (LKR) generation at the client MPLS-TP (sub-)layer is
terminated, as described in section 5.4. terminated, as described in section 5.4.
8. Security Considerations 8. Security Considerations
A number of security considerations are important in the context A number of security considerations are important in the context
of OAM applications. of OAM applications.
OAM traffic can reveal sensitive information such as passwords, OAM traffic can reveal sensitive information such as performance
performance data and details about e.g. the network topology. data and details about the current state of the network.
The nature of OAM data therefore suggests that some form of Insertion of, or modifications to OAM transactions can mask the
authentication, authorization and encryption is in place. This true operational state of the network and in the case of
will prevent unauthorized access to vital equipment and it will transactions for administration control, such as Lock or
prevent third parties from learning about sensitive information dataplane loopback instructions, these can be used for explicit
about the transport network. However it should be observed that denial of service attacks. The effect of such attacks is
the combination of all permutations of unique MEP to MEP, MEP to mitigated only by the fact that the managed entities whose state
MIP, and intermediate system originated transactions mitigates can be masked is limited to those that transit the point of
against the practical establishment and maintenance of a large malicious access to the network internals due to the fate
number of security associations per MEG. sharing nature of OAM messaging.
For this reason it is assumed that the network is physically The sensitivity of OAM data therefore suggests that one solution
secured against man-in-the-middle attacks. Further, this is that some form of authentication, authorization and
document describes OAM functions that, if a man-in-the-middle encryption is in place. This will prevent unauthorized access to
attack was possible, could be exploited to significantly disrupt vital equipment and it will prevent third parties from learning
proper operation of the network. about sensitive information about the transport network. However
it should be observed that the combination of the need for
timeliness of OAM transaction exchange and all permutations of
unique MEP to MEP, MEP to MIP, and intermediate system
originated transactions mitigates against the practical
establishment and maintenance of a large number of security
associations per MEG either in advance or as required.
For this reason it is assumed that the internal links of the
network is physically secured from malicious access such that
OAM transactions scoped to fault and performance management of
individual MEGs are not encumbered with additional security.
Mechanisms that the framework does not specify might be subject Mechanisms that the framework does not specify might be subject
to additional security considerations. to additional security considerations.
9. IANA Considerations 9. IANA Considerations
No new IANA considerations. No new IANA considerations.
10. Acknowledgments 10. Acknowledgments
skipping to change at page 54, line 10 skipping to change at page 59, line 10
Swallow, Yuji Tochio, Curtis Villamizar, Maarten Vissers and Swallow, Yuji Tochio, Curtis Villamizar, Maarten Vissers and
Xuequin Wei for their comments and enhancements to the text. Xuequin Wei for their comments and enhancements to the text.
This document was prepared using 2-Word-v2.0.template.dot. This document was prepared using 2-Word-v2.0.template.dot.
11. References 11. References
11.1. Normative References 11.1. Normative References
[1] Rosen, E., Viswanathan, A., Callon, R., "Multiprotocol [1] Rosen, E., Viswanathan, A., Callon, R., "Multiprotocol
Label Switching Architecture", RFC 3031, January 2001 Label Switching Architecture", RFC 3031, January 2001
[2] Bryant, S., Pate, P., "Pseudo Wire Emulation Edge-to-Edge [2] Bryant, S., Pate, P., "Pseudo Wire Emulation Edge-to-Edge
(PWE3) Architecture", RFC 3985, March 2005 (PWE3) Architecture", RFC 3985, March 2005
[3] Nadeau, T., Pignataro, S., "Pseudowire Virtual Circuit [3] Nadeau, T., Pignataro, S., "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007 Pseudowires", RFC 5085, December 2007
[4] Bocci, M., Bryant, S., "An Architecture for Multi-Segment [4] Bocci, M., Bryant, S., "An Architecture for Multi-Segment
Pseudo Wire Emulation Edge-to-Edge", RFC 5659, October Pseudo Wire Emulation Edge-to-Edge", RFC 5659, October
2009 2009
[5] Niven-Jenkins, B., Brungard, D., Betts, M., sprecher, N., [5] Niven-Jenkins, B., Brungard, D., Betts, M., sprecher, N.,
Ueno, S., "MPLS-TP Requirements", RFC 5654, September 2009 Ueno, S., "MPLS-TP Requirements", RFC 5654, September 2009
[6] Agarwal, P., Akyol, B., "Time To Live (TTL) Processing in [6] Agarwal, P., Akyol, B., "Time To Live (TTL) Processing in
Multiprotocol Label Switching (MPLS) Networks", RFC 3443, Multiprotocol Label Switching (MPLS) Networks", RFC 3443,
January 2003 January 2003
[7] Vigoureux, M., Bocci, M., Swallow, G., Ward, D., Aggarwal, [7] Vigoureux, M., Bocci, M., Swallow, G., Ward, D., Aggarwal,
R., "MPLS Generic Associated Channel", RFC 5586, June 2009 R., "MPLS Generic Associated Channel", RFC 5586, June 2009
[8] Bocci, M., et al., "A Framework for MPLS in Transport [8] Bocci, M., et al., "A Framework for MPLS in Transport
Networks", RFC 5921, July 2010 Networks", RFC 5921, July 2010
[9] Bocci, M., et al., " MPLS Transport Profile User-to-Network and [9] Bocci, M., et al., " MPLS Transport Profile User-to-Network and
Network-to-Network Interfaces", draft-ietf-mpls-tp-uni-nni-00 Network-to-Network Interfaces", draft-ietf-mpls-tp-uni-nni-02
(work in progress), August 2010 (work in progress), December 2010
[10] Swallow, G., Bocci, M., "MPLS-TP Identifiers", draft-ietf- [10] Swallow, G., Bocci, M., "MPLS-TP Identifiers", draft-ietf-
mpls-tp-identifiers-02 (work in progress), July 2010 mpls-tp-identifiers-03 (work in progress), December 2010
[11] Vigoureux, M., Betts, M., Ward, D., "Requirements for OAM [11] Vigoureux, M., Betts, M., Ward, D., "Requirements for OAM
in MPLS Transport Networks", RFC 5860, May 2010 in MPLS Transport Networks", RFC 5860, May 2010
[12] Bradner, S., McQuaid, J., "Benchmarking Methodology for [12] Bradner, S., McQuaid, J., "Benchmarking Methodology for
Network Interconnect Devices", RFC 2544, March 1999 Network Interconnect Devices", RFC 2544, March 1999
[13] ITU-T Recommendation G.806 (01/09), "Characteristics of [13] ITU-T Recommendation G.806 (01/09), "Characteristics of
transport equipment - Description methodology and generic transport equipment - Description methodology and generic
functionality ", January 2009 functionality ", January 2009
11.2. Informative References 11.2. Informative References
[14] Sprecher, N., Nadeau, T., van Helvoort, H., Weingarten, [14] Sprecher, N., Nadeau, T., van Helvoort, H., Weingarten,
Y., "MPLS-TP OAM Analysis", draft-ietf-mpls-tp-oam- Y., "MPLS-TP OAM Analysis", draft-ietf-mpls-tp-oam-
analysis-02 (work in progress), July 2010 analysis-02 (work in progress), July 2010
[15] Nichols, K., Blake, S., Baker, F., Black, D., "Definition [15] Nichols, K., Blake, S., Baker, F., Black, D., "Definition
of the Differentiated Services Field (DS Field) in the of the Differentiated Services Field (DS Field) in the
IPv4 and IPv6 Headers", RFC 2474, December 1998 IPv4 and IPv6 Headers", RFC 2474, December 1998
[16] Grossman, D., "New terminology and clarifications for [16] Grossman, D., "New terminology and clarifications for
Diffserv", RFC 3260, April 2002. Diffserv", RFC 3260, April 2002.
[17] Kompella, K., Rekhter, Y., Berger, L., "Link Bundling in [17] Kompella, K., Rekhter, Y., Berger, L., "Link Bundling in
MPLS Traffic Engineering (TE)", RFC 4201, October 2005 MPLS Traffic Engineering (TE)", RFC 4201, October 2005
[18] ITU-T Recommendation G.707/Y.1322 (01/07), "Network node [18] ITU-T Recommendation G.707/Y.1322 (01/07), "Network node
interface for the synchronous digital hierarchy (SDH)", interface for the synchronous digital hierarchy (SDH)",
January 2007 January 2007
[19] ITU-T Recommendation G.805 (03/00), "Generic functional [19] ITU-T Recommendation G.805 (03/00), "Generic functional
architecture of transport networks", March 2000 architecture of transport networks", March 2000
[20] ITU-T Recommendation Y.1731 (02/08), "OAM functions and [20] ITU-T Recommendation Y.1731 (02/08), "OAM functions and
mechanisms for Ethernet based networks", February 2008 mechanisms for Ethernet based networks", February 2008
[21] IEEE Standard 802.1AX-2008, "IEEE Standard for Local and [21] IEEE Standard 802.1AX-2008, "IEEE Standard for Local and
Metropolitan Area Networks - Link Aggregation", November Metropolitan Area Networks - Link Aggregation", November
2008 2008
[22] Le Faucheur et.al. " Multi-Protocol Label Switching (MPLS) [22] Le Faucheur et.al. " Multi-Protocol Label Switching (MPLS)
Support of Differentiated Services", RFC 3270, May 2002. Support of Differentiated Services", RFC 3270, May 2002.
Authors' Addresses Authors' Addresses
Dave Allan Dave Allan
Ericsson Ericsson
Email: david.i.allan@ericsson.com Email: david.i.allan@ericsson.com
Italo Busi Italo Busi
Alcatel-Lucent Alcatel-Lucent
 End of changes. 242 change blocks. 
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