MPLS Working Group I. Busi (Ed)
Internet Draft Alcatel-Lucent
Intended status: Informational B. Niven-Jenkins (Ed)
BT
D. Allan (Ed)
Ericsson
Expires: June September 5, 2010 March 5, 2010 December 10, 2009
MPLS-TP OAM Framework
draft-ietf-mpls-tp-oam-framework-04.txt
draft-ietf-mpls-tp-oam-framework-05.txt
Abstract
Multi-Protocol Label Switching (MPLS) Transport Profile (MPLS-TP) is
based on a profile of the MPLS and pseudowire (PW) procedures as
specified in the MPLS Traffic Engineering (MPLS-TE), pseudowire (PW)
and multi-segment PW (MS-PW) architectures complemented with
additional Operations, Administration and Maintenance (OAM)
procedures for fault, performance and protection-switching management
for packet transport applications that do not rely on the presence of
a control plane.
This document describes a framework to support a comprehensive set of
OAM procedures that fulfills the MPLS-TP OAM requirements [12].
This document is a product of a joint Internet Engineering Task Force
(IETF) / International Telecommunications Union Telecommunications
Standardization Sector (ITU-T) effort to include an MPLS Transport
Profile within the IETF MPLS and PWE3 architectures to support the
capabilities and functionalities of a packet transport network as
defined by the ITU-T.
Status of this Memo
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Abstract
Multi-Protocol Label Switching (MPLS) Transport Profile (MPLS-TP) is
based on a profile Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the MPLS Trust Legal Provisions and pseudowire (PW) procedures are provided without warranty as
specified
described in the MPLS Traffic Engineering (MPLS-TE), pseudowire (PW)
and multi-segment PW (MS-PW) architectures complemented with
additional Operations, Administration BSD License.
Table of Contents
1. Introduction..................................................5
1.1. Contributing Authors.....................................5
2. Conventions used in this document.............................6
2.1. Terminology..............................................6
2.2. Definitions..............................................7
3. Functional Components.........................................8
3.1. Maintenance Entity and Maintenance (OAM)
procedures for fault, performance Entity Group..........9
3.2. Nested MEGs: Path Segment Tunnels and protection-switching management
for packet transport applications that do not rely on the presence of
a control plane.
This document describes a framework to support a comprehensive set of
OAM procedures that fulfills the MPLS-TP OAM requirements [12].
This document is a product of a joint Internet Engineering Task Force
(IETF) / International Telecommunications Union Telecommunications
Standardization Sector (ITU-T) effort to include an MPLS Transport
Profile within the IETF MPLS and PWE3 architectures to support the
capabilities and functionalities of a packet transport network.
Table of Contents
1. Introduction..................................................5
1.1. Contributing Authors.....................................5
1.2. Editors Issues...........................................6
2. Conventions used in this document.............................9
2.1. Terminology..............................................9
2.2. Definitions.............................................10
3. Functional Components........................................12
3.1. Maintenance Entity and Maintenance Entity Group.........13
3.2. Tandem Connection
Monitoring...................................................11
3.3. MEG End Points (MEPs)...................................16
3.3. (MEPs)...................................12
3.4. MEG Intermediate Points (MIPs)..........................19
3.4. Server MEPs.............................................20 (MIPs)..........................13
3.5. Path Segment Tunnels and Tandem Connection Monitoring...21 Server MEPs.............................................14
3.6. Configuration Considerations............................15
3.7. P2MP considerations.....................................15
4. Reference Model..............................................21 Model..............................................16
4.1. MPLS-TP Section Monitoring..............................23 Monitoring (SME)........................18
4.2. MPLS-TP LSP End-to-End Monitoring.......................24 Monitoring (LME).................19
4.3. MPLS-TP LSP Path Segment Tunnel Monitoring..............25 Monitoring (LPSTME).....19
4.4. MPLS-TP PW Monitoring...................................27 Monitoring (PME).............................21
4.5. MPLS-TP MS-PW Path Segment Tunnel Monitoring............27 Monitoring (PPSTME)...21
5. OAM Functions for proactive monitoring.......................28 monitoring.......................22
5.1. Continuity Check and Connectivity Verification..........29 Verification..........23
5.1.1. Defects identified by CC-V.........................30 CC-V.........................25
5.1.2. Consequent action..................................31 action..................................26
5.1.3. Configuration considerations.......................32
5.1.4. Applications for proactive CC-V....................33 considerations.......................27
5.2. Remote Defect Indication................................34 Indication................................28
5.2.1. Configuration considerations.......................34
5.2.2. Applications for Remote Defect Indication..........35 considerations.......................29
5.3. Alarm Reporting.........................................35 Reporting.........................................29
5.4. Lock Reporting..........................................36 Reporting..........................................30
5.5. Packet Loss Monitoring..................................36 Measurement.................................31
5.5.1. Configuration considerations.......................37
5.5.2. Applications for Packet Loss Monitoring............37 considerations.......................32
5.6. Client Signal Failure Indication........................38 Indication...............................32
5.6.1. Configuration considerations.......................38
5.6.2. Applications for Client Signal Failure Indication..38 considerations.......................32
5.7. Packet Delay Measurement.......................................39 Measurement................................33
5.7.1. Configuration considerations.......................39
5.7.2. Applications for Delay Measurement.................40 considerations.......................33
6. OAM Functions for on-demand monitoring.......................40 monitoring.......................33
6.1. Connectivity Verification...............................40 Verification...............................34
6.1.1. Configuration considerations.......................41 considerations.......................35
6.2. Packet Loss Monitoring..................................42 Measurement.................................35
6.2.1. Configuration considerations.......................42
6.2.2. Applications for On-demand Packet Loss Monitoring..42 considerations.......................36
6.3. Diagnostic..............................................42 Diagnostic Tests........................................36
6.3.1. Throughput Estimation..............................36
6.3.2. Data plane Loopback................................37
6.4. Route Tracing...........................................43 Tracing...........................................37
6.4.1. Configuration considerations.......................38
6.5. Packet Delay Measurement.......................................44 Measurement...............................38
6.5.1. Configuration considerations.......................44
6.5.2. Applications for Delay Measurement.................45 considerations......................38
6.6. Lock Instruct...........................................45 Instruct..........................................39
6.6.1. Locking a transport path..........................39
6.6.2. Unlocking a transport path........................39
7. Security Considerations......................................45 Considerations.....................................40
8. IANA Considerations..........................................45 Considerations.........................................40
9. Acknowledgments..............................................46 Acknowledgments.............................................40
10. References..................................................47 References.................................................42
10.1. Normative References...................................47 References..................................42
10.2. Informative References.................................47 References................................42
Editors' Note:
This Informational Internet-Draft is aimed at achieving IETF
Consensus before publication as an RFC and will be subject to an IETF
Last Call.
[RFC Editor, please remove this note before publication as an RFC and
insert the correct Streams Boilerplate to indicate that the published
RFC has IETF Consensus.]
1. Introduction
As noted in [8], MPLS-TP defines a profile of the MPLS-TE and (MS-)PW
architectures defined in RFC 3031 [2], RFC 3985 [5] and [7] which is
complemented with additional OAM mechanisms and procedures for alarm,
fault, performance and protection-switching management for packet
transport applications.
In line with [13], existing MPLS OAM mechanisms will be used wherever
possible and extensions or new OAM mechanisms will be defined only
where existing mechanisms are not sufficient to meet the
requirements.
The MPLS-TP OAM framework defined in this document provides a
comprehensive set of OAM procedures that satisfy the MPLS-TP OAM
requirements [12]. In this regard, it defines similar OAM
functionality as for existing SONET/SDH and OTN OAM mechanisms (e.g.
[16]).
The MPLS-TP OAM framework is applicable to both LSPs and (MS-)PWs and
supports co-routed and bidirectional p2p transport paths as well as
unidirectional p2p and p2mp transport paths.
This document is a product of a joint Internet Engineering Task Force
(IETF) / International Telecommunications Union Telecommunications
Standardization Sector (ITU-T) effort to include an MPLS Transport
Profile within the IETF MPLS and PWE3 architectures to support the
capabilities and functionalities of a packet transport network. network as
defined by the ITU-T.
1.1. Contributing Authors
Dave Allan, Italo Busi, Ben Niven-Jenkins, Annamaria Fulignoli,
Enrique Hernandez-Valencia, Lieven Levrau, Dinesh Mohan, Vincenzo
Sestito, Nurit Sprecher, Huub van Helvoort, Martin Vigoureux, Yaacov
Weingarten, Rolf Winter
1.2. Editors Issues
Editor's Note:
This section is
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be removed prior to submission to the RFC editor.
1) ME architecture needs further discussion/clarification
Agreement (call 24 November):
o Co-routed bidirectional p2p transport entity: one bidirectional
ME
o Associated bidirectional p2p transport entity: two
unidirectional MEs
o Unidirectional p2p transport entity: one unidirectional ME
o Unidirectional p2mp (with N leaves) transport entity: N
unidirectional ME
Clarify that in a p2mp transport entity all the traffic (including
OAM packets) is sent (multicast) from the root to all the leaves. As
a consequence:
o To send an OAM packet to all leaves, it is required to send a
single OAM packet that will be delivered by the forwarding plane
to all the leaves and processed by all the leaves.
o To send an OAM packet to a single leaf, it is required to send a
single OAM packet that will be delivered by the forwarding plane
to all the leaves and processed only by the target leaf and
ignored by the other leaves.
o In order to send an OAM packet to M leaves (i.e., a subset of
all the leaves), the current working assumption is to send M
different (multicast) OAM packets targeted to each individual
leaf in the group of M leaves. Better mechanisms are under
investigation and might be added in future versions of this
draft.
2) Use of terms LTCME and PTCME, should these be genericised for
PSTs.
Agreement (call 24 November): the editors of the framework document
will make sure that the framework document is aligned with the
decision to use the term PST. This document will be aligned with this
decision.
3) CV refers to using an ME ID for misbranching detection. This does
not align with p2mp LSPs where a CV would then be required to
carry all the MEs in the MEG.
Agreement (call 24 November): we are going to use the term MEG ID in
the document. ME ID has been used in older versions of the document
and its use is legacy.
For pro-active CC-V (both p2p and p2mp), the globally unique MEP ID
information needs to be carried: section on pro-active CC-V needs to
be updated accordingly.
4) Discussions of PW monitoring and PW tandem connection monitoring
seem to be rendered out of scope by the layering decision at
Hiroshima.
Discussion points (call 24 November) - No agreement reached on this
issue
PW OAM architecture: based on the architecture defined in this
document using MEP and MIPs
PW TCM concept: just a specific application of the architecture of
the TP-LSP (1:1 mapped with the monitored PW) carrying a PW segment
in the MS-PW architecture.
Generic clarifications (to be added) [terminology based on RFC 5654]:
o before a TCM is setup, we can have a concatenated LSP
segment. After the TCM (that is a TP-LSP) is setup, we have a
single LSP segment between the TCM end-points;
o before a TCM is setup, we can have a concatenated PW segment.
After the TCM (that is a TP-LSP) is setup, we have a single
PW segment between the TCM end-points.
Problems with PW TCM are the implications of removing S-PEs from the
PW path. Need further discussion. It is not obvious to Dave that
removing an LSR from a path can be done hitlessly either ... by
slipping a PST under it ...
Action (Italo): check which requirements cannot be met if PW TCM
between non-adjacent PEs cannot be supported and whether this is a
showstopper issue or not.
Action (Italo): describe the PW TCM as an LSP and circulate the
description to the mailing list for review. If needed, another call
will be setup to finalize the discussion.
Action (Matthew, Italo): Develop a couple of diagrams showing how the
mechanism works for LSPs and PWs.
5) Concerns have been raised against the idea of having MIPs capable
to generate spontaneous messages. AIS/Lock Indication packets are
generated by the adaptation functions. This point needs
clarifying.
Agreement (9 December):
AIS/Lock Indication are generate by a MIP node (to be define as a
node hosting a MIP) w/o saying that they are generated by a MIP.
The general framework will describe the mechanism for intermediate
nodes to insert packets and each specific framework document (e.g.,
OAM framework) will describe the usage of this capability on a case-
by-case basis. When you provision bw between two end-points you must
allow enough bw for any additional traffic, including traffic from
MEPs and MIPs.
OAM framework will describe that a MIP node may insert OAM packets
into a LSP and this will be described on a function-by-function
basis. It will also describe the functions that require a MIP to
generate OAM packets (e.g., on-demand CV).
6) Presence or absence of MIPs is a bizarre point. At least one MIP
in every node is addressed by TTL, and gaps in the enablement of
MIPs would produce spurious test results. A convention of "MIPs
exist at any node on a transport path that has a return path to a
source MEP" would make sense vs. discussing manual
enable/disable/configuration of MIPs.
Note - the annotated text ("If the set of MIPs is actually sparse
(i.e. not every hop is a MIP), then it has to be intermediate nodes
to do some operations") needs further clarification.
Agreement (9 December):
All the intermediate nodes host MIP(s). Local policy allows them to
be enabled per function and per LSP. The local policy is controlled
by the management system, which may delegate it to the control plane.
7) Discussions in Hiroshima and subsequent calls have suggested use
of alternative return paths "if available", not all of which will
be GAL/GACH encapsulated? This point needs clarifying.
Agreement (9 December):
When the return path is not an MPLS-TP path, the reply message does
not need to be GAL/ACH encapsulated.
The request message needs to carry sufficient information to allow
the target MIP/MEP to reply when a non MPLS-TP return path is used.
8) Data plane loopback
Action (17 November): check on the mailing list (both ITU-T and IETF
to get inputs from both types of operators).
9) Review the draft to check that all the known implications related
to the support of p2mp transport paths have been described.
This check will be done in the next version after the current open
points/comments have been resolved.
10)Given layering discussion in Hiroshima, it is not very clear
whether MPLS TP is a sub layer network within the MPLS layer
network or a layer network by its own.
This issue should be resolved in the context of the MPLS TP Framework
draft but has impacts on this draft as well.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [1].
2.1. Terminology
AC Attachment Circuit
DBN Domain Border Node
FDI Forward Defect Indication
LER Label Edge Router
LME LSP Maintenance Entity
LSP Label Switched Path
LSR Label Switch Router
LPSTME LSP packet segment tunnel interpreted as described in RFC-2119 [1].
2.1. Terminology
AC Attachment Circuit
DBN Domain Border Node
FDI Forward Defect Indication
LER Label Edge Router
LME LSP Maintenance Entity
LSP Label Switched Path
LSR Label Switch Router
LPSTME LSP packet segment tunnel ME
ME Maintenance Entity
MEG Maintenance Entity Group
MEP Maintenance Entity Group End Point
MIP Maintenance Entity Group Intermediate Point
PHB Per-hop Behavior
PME PW Maintenance Entity
PPSTME PW path segment tunnel ME
PST Path Segment Tunnel
PSN Packet Switched Network
PW Pseudowire
SLA Service Level Agreement
SME Section Maintenance Entity
2.2. Definitions
Note - the definitions in this section are intended to be in line
with ITU-T recommendation Y.1731 in order to have a common,
unambiguous terminology. They do not however intend to imply a
certain implementation but rather serve as a framework to describe
the necessary OAM functions for MPLS-TP.
Data plane loopback: it is an out-of-service test where an interface
at either an intermediate or terminating node in a path is placed
into a data plane loopback state, such that it loops back all the
packets (including user data and OAM) it receives on a specific MPLS-
TP transport path.
Domain Border Node (DBN): An LSP intermediate MPLS-TP node (LSR) that
is at the boundary of an MPLS-TP OAM domain. Such a node may be
present on the edge of two domains or may be connected by a link to
an MPLS-TP node in another OAM domain.
Loopback: see data plane loopback and OAM loopback definitions.
Maintenance Entity (ME): Some portion of a transport path that
requires management bounded by two points, and the relationship
between those points to which maintenance and monitoring operations
apply (details in section 3.1).
Maintenance Entity Group (MEG): The set of one or more maintenance
entities that maintain and monitor a transport path in an OAM domain.
MEP: A MEG end point (MEP) is capable of initiating (MEP Source) and
terminating (MEP Sink) OAM messages for fault management and
performance monitoring. MEPs reside at the boundaries of an ME
(details in section 3.2). 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
messages and may generate OAM messages in reaction to received OAM
messages. It never generates unsolicited OAM messages itself. A MIP
resides within an MEG between MEPs (details in section 3.2). 3.3).
OAM domain: A domain, as defined in [11], whose entities are grouped
for the purpose of keeping the OAM confined within that domain.
Note - within the rest of this document the term "domain" is used to
indicate an "OAM domain"
OAM flow: Is the set of all OAM messages originating with a specific
MEP that instrument one direction of a MEG.
OAM information element: An atomic piece of information exchanged
between MEPs in MEG used by an OAM application.
OAM loopback: it is the capability of a node to intercepts some
specific OAM packets and to generate a reply back to their sender.
OAM loopback can work in-service and can support different OAM
functions (e.g., bidirectional on-demand connectivity verification).
OAM Message: One or more OAM information elements that when exchanged
between MEPs or between MEPs and MIPs performs some OAM functionality
(e.g. connectivity verification)
OAM Packet: A packet that carries one or more OAM messages (i.e. OAM
information elements).
Path: See Transport Path
Signal Fail: A condition declared by a MEP when the data forwarding
capability associated with a transport path has failed, e.g. loss of
continuity.
Tandem Connection: A tandem connection is an arbitrary part of a
transport path that can be monitored (via OAM) independent of the
end-to-end monitoring (OAM). The tandem connection may also include
the forwarding engine(s) of the node(s) at the boundaries of the
tandem connection.
This document uses the terms defined in RFC 5654 [11].
This document uses the term 'Per-hop Behavior' as defined in [14].
3. Functional Components
MPLS-TP defines a profile of the MPLS and PW architectures ([2], [5]
and [7]) that is designed to transport service traffic where the
characteristics of information transfer between the transport path
endpoints can be demonstrated to comply with certain performance and
quality guarantees. In order to verify and maintain these performance
and quality 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 arbitrary parts of transport paths, defined as Tandem
Connections, between any two arbitrary points along a path.
In order to describe the required OAM functionality, this document
introduces a set of high-level functional components. [Note -
discussion in Munich -tues concluded that TCM not possible with PWs -
can monitor a single PW segment - but attempting to monitor more than
one segment converts the PW into an LSP and therefore the intervening
SPEs are unable to see the PW as a PW due to the differences in how
OAM flows are disambiguated.] [editors: if true this IMO is a huge
problem as the one place I would really want TCM is a multi-domain
MS-PW, else I have to control plane peer at two layers, pending
resolution of discussion item 4 in section 1.2]
When a control plane is not present, the management plane configures
these functional components. Otherwise they can be configured either
by the management plane or by the control plane.
These functional components should be instantiated when the path [7]) that is
created by either the management plane or by required to transport service traffic where the control plane (if
present). Some components may be instantiated after
characteristics of information transfer between the transport path is
initially created (e.g. PST).
[Dave: are we discussing the same issue for LSP PSTs as for PWs, an
S-PE cannot easily
endpoints can be removed, certainly not hitlessly, how is an LSP
different?] demonstrated to comply with certain performance and
quality guarantees.
In order to describe the required OAM functionality, this document
introduces a set of high-level functional components.
3.1. Maintenance Entity and Maintenance Entity Group
MPLS-TP OAM operates in the context of Maintenance Entities (MEs)
that are a relationship between two points of a point to point
transport path or a root and a leaf of a point to multipoint
transport path to which maintenance and monitoring operations apply.
These two points are called Maintenance Entity Group (MEG) End Points
(MEPs). In between these two points zero or more intermediate points,
called Maintenance Entity Group Intermediate Points (MIPs), MAY exist
and can be shared by more than one ME in a MEG.
The MEPs that form an MEG are configured and managed to limit the
scope of an OAM flow within the MEG that the MEPs belong to (i.e.
within the domain of the transport path or segment, in the specific
sub-layer of the MPLS layer network, that is being monitored and
managed). A misbranching fault may cause OAM packets to be delivered
to a MEP that is not in the MEG of origin.
The abstract reference model for an ME with MEPs and MIPs is
described in Figure 1 below:
+-+ +-+ +-+ +-+
|A|----|B|----|C|----|D|
+-+ +-+ +-+ +-+
Figure 1 ME Abstract Reference Model
The instantiation of this abstract model to different MPLS-TP
entities is described in section 4. In this model, nodes A, B, C and
D can be LER/LSR for an LSP or the {S|T}-PEs for a MS-PW. MEPs reside
in nodes A and D while MIPs reside in nodes B and C. The links
connecting adjacent nodes can be physical links, (sub-)layer
LSPs/PSTs, or sub-layer
LSPs/PSTs. serving layer paths.
This functional model defines the relationships between all OAM
entities from a maintenance perspective, to allow each Maintenance
Entity to monitor and manage the layer (sub-)layer network under its
responsibility and to localize problems efficiently.
[Editor's note - MEG are sub-layers. Need
Another OAM functional component is referred to as Maintenance Entity
Group, which is a collection of one or more MEs that belongs to check the document for
consistency with this agreement]
same transport path and that are maintained and monitored as a group.
An MPLS-TP maintenance entity group can cover either Maintenance Entity Group may be defined to monitor the whole end-
to-end path or a
transport path segment tunnel supporting some portion for fault and/or performance management.
The MEPs that form an MEG are configured and managed to limit the
scope of an OAM flow within the MEG that the MEPs belong to (i.e.
within the domain of the transport path. path that is being monitored and
managed). A Maintenance Entity Group misbranching fault may cause OAM packets to be defined delivered
to monitor a MEP that is not in the MEG of origin.
In case of unidirectional point-to-point transport path for fault and/or performance management. paths, a single
unidirectional Maintenance Entity is defined to monitor it.
In case of associated bi-directional point-to-point transport paths,
two independent unidirectional Maintenance Entities are defined to
independently monitor each direction. This has implications for
transactions that terminate at or query a MIP as a return path from
MIP to source MEP does not necessarily exist in a unidirectional ME.
The following properties apply to all MPLS-TP MEGs:
o They can be nested but not overlapped, e.g. an MEG may cover a
segment or MEG.
In case of co-routed bi-directional point-to-point transport paths, a concatenated segment
single bidirectional Maintenance Entity is defined to monitor both
directions congruently.
In case of another MEG, and may also
include unidirectional point-to-multipoint transport paths, a
single unidirectional Maintenance entity for each leaf is defined to
monitor the forwarding engine(s) of transport path from the node(s) at root to that leaf.
The reference model for the edge(s) p2mp MEG is represented in Figure 2.
+-+
/--|D|
/ +-+
+-+
/--|C|
+-+ +-+/ +-+\ +-+
|A|----|B| \--|E|
+-+ +-+\ +-+ +-+
\--|F|
+-+
Figure 2 Reference Model for p2mp MEG
In case of p2mp transport paths, the segment or concatenated segment, but all its MEPs and MIPs OAM operations are
no longer part of the encompassing MEG. It is possible that MEPs
of nested MEGs reside on a single node. independent
for each ME (A-D, A-E and A-F):
o Each OAM flow Fault conditions - some faults may impact more than one ME
depending from where the failure is associated with a single Maintenance Entity
Group. located;
o OAM Packet loss - packet dropping may impact more than one ME
depending from where the packets that instrument a particular direction of an LSP are
subject to the same forwarding treatment lost;
o Packet delay - will be unique per ME.
Each leaf (i.e. fate share) as the
data traffic D, E and in some cases may be required F) terminates OAM flows to have common
queuing discipline E2E with monitor the class of traffic monitored. OAM
packets can be distinguished ME
from the data traffic using the GAL
and ACH constructs [9] for LSP itself and Section or the ACH construct
[6]and [9] for (MS-)PW.
[Editor's note: A key point in root while the definition of an ME is root (i.e. A) generates OAM
messages common to all the end-
points are defined by location MEs of the logical function MEP
Later p2mp MEG. Nodes B and C MAY
implement a MIP in the framework we will discuss the precision with which we
can identify the location of a MEP/MIP i.e, ingress i/f, egress i/f
or node.
We need corresponding MEG.
3.2. Nested MEGs: Path Segment Tunnels and Tandem Connection Monitoring
In order to distinguish between the point of interception of an OAM
msg verify and the point where the action takes place.
Action: look at the text in the framework document regarding the
location of the functional components (MEPs maintain performance and MIPs).]
[Editors' note: Somewhere we quality guarantees,
there is a need to distinguish between the OAM
control function and the not only apply OAM measurement function. i.e. we set up functionality on a transport
path granularity (e.g. LSP or MS-PW), but also on arbitrary parts of
transport paths, defined as Tandem Connections, between any two
arbitrary points along a transport path.
Path segment tunnels (PSTs), as defined in [8], are instantiated to
provide monitoring of a portion of a
loop back (a control function, in which case the OAM message may set of co-routed transport paths
(LSPs or MS-PWs). Path segment tunnels can also be
intercepted and actioned anywhere convenient), and the measurement
function (i.e. looping employed to meet
the packet requirement to determine provide tandem connection monitoring (TCM).
TCM for a given portion of a transport path is implemented by first
creating a path segment tunnel that it reached has a
particular part 1:1 association with
portion of the network) which needs transport path that is to be actioned at a
precisely know uniquely monitored. This
means there is direct correlation between all FM and stipulated point in PM information
gathered for the network/equipment.
Action (Dave) - add some text on PST AND the subject.]
Note that not all functionality / processing monitored portion of an OAM pkt needs to
take place at the point of measurement. [editors: this comment E2E transport
path. The PST is not
clear. For discussion during revision call]
[Editors' note - Address monitored using normal LSP monitoring.
There are a number of implications to this comment while addressing approach:
1) The PST would use the control
and measurement issue above.
We considered uniform model of TC code point copying
between sub-layers for diffserv such that an OAM function can be decomposed into the
following components
- Instruction or command
- Execution
- Addressing (node, interface etc) is ttl/LSP enough - do we need
sub-addressing to cause execution on a specific component in E2E markings and
PHB treatment for the
node - i.e. egress interface
- Response via OAM
- Reporting to mgt interface]
[Editor's note: transport path was preserved by the MPLS-TP framework will describe how it is
possible to inject OAM packets on intermediate nodes. We need to
describe how this capability is used within PST.
2) The PST would use the pipe model for TTL handling such that MIP
addressing for the E2E entity would be not be impacted by the OAM framework and to
reference to
presence of the MPLS-TP framework PST.
3) PM statistics need to be adjusted for the description encapsulation overhead
of this
capability]
Another OAM construct the additional PST sub-layer.
A PST is referred instantiated to as Maintenance Entity Group,
which is create an MEG that monitors a collection segment of one or more MEs that belongs to the same a
transport path and that (LSP or PW). The endpoints of the PST are maintained MEPs and monitored as a group.
A use case for
limit the scope of an MEG with more than one ME is point-to-multipoint
OAM. The reference model for OAM flow within the p2mp MEG is represented in Figure 2.
+-+
/--|D|
/ +-+
+-+
/--|C|
+-+ +-+/ +-+\ +-+
|A|----|B| \--|E|
+-+ +-+\ +-+ +-+
\--|F|
+-+
Figure 2 Reference Model for p2mp MEG
In case the MEPs belong to
(i.e. within the domain of p2mp transport paths, the OAM operations are independent
for each ME (A-D, A-E PST that is being monitored and A-F):
managed).
The following properties apply to all MPLS-TP MEGs:
o Fault conditions - some faults They can be nested but not overlapped, e.g. an MEG may impact more than one ME
depending from where the failure is located
o Packet loss - packet dropping cover a
segment or a concatenated segment of another MEG, and may impact more than one ME
depending from where also
include the packets forwarding engine(s) of the node(s) at the edge(s) of
the segment or concatenated segment, but all its MEPs and MIPs are lost
no longer part of the encompassing MEG. It is possible that MEPs
of nested MEGs reside on a single node.
o Packet delay - depending It is possible for MEPs of nested MEGs to reside on different paths a single node.
o Each leaf (i.e. D, E and F) terminates OAM flows flow is associated with a single Maintenance Entity
Group.
o OAM packets that instrument a particular direction of a transport
path are subject to monitor the ME
from itself and the root while the root same forwarding treatment (i.e. A) generates OAM
messages common fate
share) as the data traffic and in some cases may be required to all
have common queuing discipline E2E with the MEs class of traffic
monitored. OAM packets can be distinguished from the p2mp MEG. Nodes B data traffic
using the GAL and C MAY
implement a MIP in ACH constructs [9] for LSP and Section or the corresponding MEG.
3.2.
ACH construct [6]and [9] for (MS-)PW.
3.3. MEG End Points (MEPs)
MEG End Points (MEPs) are the source and sink points of an MEG. In
the context of an MPLS-TP LSP, only LERs can implement MEPs while in
the context of a path segment tunnel (PST) both LERs and LSRs can
implement MEPs that contribute to the overall monitoring
infrastructure for the transport path. Regarding MPLS-TP PW, only T-
PEs can implement MEPs while for PSTs supporting a PW both T-PEs and
S-PEs can implement MEPs. In the context of MPLS-TP Section, any
MPLS-TP NE LSR can implement a MEP.
[Munich: See note about PW Tandem monitoring earlier, and whether a
PW can be a tandem connection - for further discussion (discussion
point 4 in section 1.2)]
MEPs are responsible for activating and controlling all of the OAM
functionality for the MEG. A MEP is capable of originating and
terminating OAM messages for fault management and performance
monitoring. These OAM messages are encapsulated into an OAM packet
using the G-ACh as defined in RFC 5586 [9]: in this case the G-ACh
message is an OAM message and the channel type indicates an OAM
message. A MEP terminates all the OAM packets it receives from the
MEG it belongs to. The MEG the OAM packet belongs to is inferred from
the MPLS or PW label.[Editors: given label or, in case of MPLS-TP section, the discussion about alternative MPLS-TP port
the OAM packet has been received with the GAL at the top of the label
stack.
OAM packets may require the use of an available "out-of-band" return paths,
path (as defined in [8]). In such cases sufficient information is a GAL/GaCH always present ...?. For discussion on
required in the IETF review calls] originating transaction such that the OAM reply
packet can be constructed (e.g. IP address).
Once an MEG is configured, the operator can configure which OAM
functions to use on the MEG but the MEPs are always enabled. A node
at the edge of an MEG always supports a MEP.
MEPs terminate all OAM packets received from the associated transport
path or path segment tunnel [Editors: the PST definition in the
framework should be augmented to clarity that the clients of a PST
should edge of an MEG always be LSPs or PWs]. supports a MEP.
MEPs terminate all OAM packets received from the associated MEG. As
the MEP corresponds to the termination of the forwarding path for an
MEG at the given sub-level, (sub-)layer, OAM packets never "leaks" outside of a
MEG in a fault free implementation.
A MEP of an MPLS-TP transport path (Section, LSP or PW) coincides
with transport path termination and monitors it for failures or
performance degradation (e.g. based on packet counts) in an end-to-
end scope. Note that both MEP source and MEP sink coincide with
transport paths' source and sink terminations.
The MEPs of a path segment tunnel are not necessarily coincident with
the termination of the MPLS-TP transport path (LSP or PW) and monitor
some portion of the transport path for failures or performance
degradation (e.g. based on packet counts) only within the boundary of
the MEG for the path segment tunnel.
An MPLS-TP MEP sink passes a fault indication to its client
(sub-)layer network as a consequent action of fault detection.
It may occur that the MEPs of a path segment tunnel are set on both
sides of the forwarding engine such that the MEG is entirely internal
to the node.
Note that a MEP can only exist at the beginning and end of a
sub-layer layer
i.e. an LSP or PW. If we need to monitor some portion of that LSP or PW [editor: mention of PW in this context needs to be
revised after agreement on discussion point 4 in section 1.2],
PW, a new sub-layer in the form of a path segment tunnel MUST be
created which permits MEPs and an associated MEG to be created.
[Editor: We need to describe the migration process for adding a path
segment tunnel.]
[Editor's note: Update the draft to capture the agreements below
after the discussion points 5, 6 and 7 in section 1.2 are resolved
(to maintain consistency):
We have the case of a MIP sending msg to a MEP. To do this it uses
the LSP label - i.e. the top label of the stack at that point.
[editors: move and clarify in section 3.3 - for further discuss.
If the set of MIPs is actually sparse (i.e. not every hop is a MIP),
then it has to be intermediate nodes to do some operations.]
Agreement (10 November): An intermediate node can send an OAM packet.
Clarify that we need to provide enough bandwidth on the transport
paths to support OAM traffic (throughout the framework document).
From IETF point of view no distinction between MIPs and adaptation
functions.
Lou question about how triggered response OAM packets are sent by
MIPs/MEPs.
Agreement (call 9 December):
o bidirectional co-routed: use the reverse path (thus checking
both the forward and backward directions of the transport
path). Co-routed bidirectional transport paths can have a
minimum bandwidth return path.
o unidirectional p2p and p2mp: no ability to support triggered
response OAM message
Non MPLS-TP LSP/PW return path MAY be requested by the OAM message
triggering the reply and the target MIP/MEP MAY attempt to reply
using the requested return path.
In this case, only the forward direction of the MPLS-TP transport
path is checked and the connectivity to the source MEP via the
requested return path is not guaranteed.
Agreement (call 17 November) associated MEG to use as a working assumption be created.
We have the same
MEP/MIP model in MS-PW OAM architecture. In order case of an intermediate node sending msg to validate a MEP. To do
this
working assumption we need to understand how to describe it uses the PW
Status information: this information is propagated on a hop-by-hop
basis between adjacent PEs using LDP (dynamic PW segments) or ACH
Status PW (static PW segments).]
3.3. LSP label - i.e. the top label of the stack at that
point.
3.4. MEG Intermediate Points (MIPs)
A MEG Intermediate Point (MIP) is a point between the MEPs of an MEG.
A MIP is capable of reacting to some OAM packets and forwarding all
the other OAM packets while ensuring fate sharing with data plane
packets. However, a MIP does not initiate [unsolicited unsolicited OAM - editors:
this text was removed in the commented .rtf document from Munich but
not tracked as a revision, validate this change after MIP/MEP
discussion (discussion point 5 in section 1.2)] packets,
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
packets that are sent on the MEG it belongs to.
An intermediate node within a point-to-point MEG can either:
o not support MPLS-TP OAM (i.e. no MIPs per node)
o support per-node MIP (i.e. a single MIP per node)
o support per-interface MIP (i.e. two or more MIPs per node on both
sides of the forwarding engine)
[Editor's note - Need to describe MIPs for p2mp MEGs]
[Editor's note - Add a Figure to describe how the two options can be
support]
A node at the edge of an MEG can also support a MEP and a
per-interface MIP at the two sides of the forwarding engine.
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 node
where the MIP resides. It is always assumed that the "pipe"/"short
pipe" model of TTL handling is used by the MPLS transport profile.
The source MEP should also include Target MIP information in 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 is
inferred from the MPLS label.
A node at the edge of an MEG can also support per-interface MEPs and
per-interface MIPs on either side of the forwarding engine.
Once an MEG is configured, the operator can enable/disable the MIPs
on the nodes within the MEG. [Editors': review this paragraph after
discussion point 6 in section 1.2 All the intermediate nodes host MIP(s).
Local policy allows them to be enabled per function and per LSP. The
local policy is resolved]
3.4. controlled by the management system, which may
delegate it to the control plane.
3.5. Server MEPs
A server MEP is a MEP of an MEG that is either:
o defined in a layer network that is "below", which is to say
encapsulates and transports the MPLS-TP layer network being
referenced, or
o defined in a sub-layer of the MPLS-TP layer network that is
"below" which is to say encapsulates and transports the sub-layer
being referenced.
A server MEP can coincide with a MIP or a MEP in the client (MPLS-TP)
layer
(sub-)layer network.
[Editors' note: review the text above pending discussion of whether
MPLS-TP is a sub-layer network within the MPLS layer network or a
layer network by its own (discussion point 10 in section 1.2)]
A server MEP also interacts with the client/server adaptation
function between the client (MPLS-TP) (sub-)layer network and the
server (sub-)layer network. The adaptation function maintains state
on the mapping of MPLS-TP transport paths that are setup over that
server layer's (sub-)layer's transport path.
For example, a server MEP can be either:
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 in section
4.1;
o An MPLS-TP Section MEP for MPLS-TP LSPs, defined in section 4.2;
o An MPLS-TP LSP MEP for MPLS-TP PWs, defined in section 4.4;
o An MPLS-TP PST MEP used for higher-level PSTs, LSP segment monitoring, as defined in
section 4.3; 4.3, for MPLS-TP LSPs or higher-level LSP PSTs;
o An MPLS-TP PW Tandem Connection PST MEP used for higher-level PTCMEs, PW segment monitoring, as defined in
section 4.5. [Editor: update this bullet after the
discussion on 4.5, for MPLS-TP PWs or higher-level PW TCM (discussion point 4 in section 1.2)] PSTs.
The server MEP can run appropriate OAM functions for fault detection
within the server (sub-)layer network, and provides a fault
indication to its client MPLS-TP layer network. Server its client MPLS-TP layer network. Server MEP OAM
functions are outside the scope of this document.
3.6. Configuration Considerations
When a control plane is not present, the management plane configures
these functional components. Otherwise they can be configured either
by the management plane or by the control plane.
Local policy allows to disable the usage of any available "out-of-
band" return path, as defined in [8], to generate OAM reply packets,
irrespectively on what is requested by the node originating the OAM
packet triggering the request.
PSTs are usually instantiated when the transport path is created by
either the management plane or by the control plane (if present).
Sometimes PST can be instantiated after the transport path is
initially created (e.g. PST).
3.7. P2MP considerations
All the traffic sent over a p2mp transport path, including OAM
packets generated by a MEP, is sent (multicast) from the root to all
the leaves. As a consequence:
o To send an OAM packet to all leaves, the source MEP can send a
single OAM packet that will be delivered by the forwarding plane
to all the leaves and processed by all the leaves.
o To send an OAM packet to a single leaf, the source MEP sends a
single OAM packet that will be delivered by the forwarding plane
to all the leaves but contains sufficient information to
identify a target leaf, and therefore is processed only by the
target leaf and ignored by the other leaves.
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
functions packets
targeted to each individual leaf in the group of M leaves.
Better mechanisms are outside the scope of this document.
3.5. Path Segment Tunnels and Tandem Connection Monitoring
Path segment tunnels (PSTs)
P2MP paths are instantiated unidirectional, therefore any return path to provide monitoring of a portion source
MEP for on demand transactions will be out of a band.
A mechanism to scope the set of co-routed transport paths. Path segment tunnels
can also be employed MEPs or MIPs expected to meet the requirement respond to provide tandem
connection monitoring (TCM).
TCM for a
given portion of a transport path is implemented by first
creating a path segment tunnel that that has a 1:1 association with
portion of the transport path that is to be uniquely monitored. This
means there "on demand" transaction is direct correlation between all FM and PM information
gathered for the PST AND useful as it relieves the monitored portion source MEP
of the E2E path. The
PST is monitored using normal LSP monitoring.
There are a number of implications requirement to this approach:
1) The PST would use the uniform model of EXP code point copying
between sub-layers for diffserv such that the E2E markings filter and
PHB treatment for the transport path was preserved by the PST.
2) The PST would use the pipe model for discard undesired responses as
normally TTL handling such that MIP
addressing for the E2E entity would be not be impacted by the
presence of the PST.
3) PM statistics need to be adjusted for the encapsulation overhead
of exhaust will address all MIPs at a given distance from
the additional PST sub-layer. source, and failure to exhaust TTL will address all MEPs.
4. Reference Model
The reference model for the MPLS-TP framework builds upon the concept
of an MEG, and its associated MEPs and MIPs, to support the
functional requirements specified in [12].
The following MPLS-TP MEGs are specified in this document:
o A Section Maintenance Entity Group (SME), allowing monitoring and
management of MPLS-TP Sections (between MPLS LSRs).
o A LSP Maintenance Entity Group (LME), allowing monitoring and
management of an end-to-end LSP (between LERs).
o A PW Maintenance Entity Group (PME), allowing monitoring and
management of an end-to-end SS/MS-PWs (between T-PEs).
o A LSP PST Maintenance Entity Group (PSTME), (LPSTME), allowing monitoring
and management of a path segment tunnel (between any LERs/LSRs
along an LSP).
o A MS-PW Tandem Connection PST Maintenance Entity (PTCME), (PPSTME), allowing monitoring and
management of a PW Tandem Connection an MPLS-TP path segment tunnel (between any
T-PEs/S-PEs along the (MS-)PW) [Editors': update this bullet after
resolution of PW TCM discussion (discussion point 4 in section
1.2] (MS-)PW).
The MEGs specified in this MPLS-TP framework are compliant with the
architecture framework for MPLS-TP MS-PWs [7] and LSPs [2].
Hierarchical LSPs are also supported in the form of path segment
tunnels. In this case, each LSP Tunnel in the hierarchy is a
different sub-layer network that can be monitored, independently from
higher and lower level LSP tunnels in the hierarchy, on an end-to-end
basis (from LER to LER) by a PSTME. It is possible to monitor a
portion of a hierarchical LSP by instantiating a hierarchical PSTME
between any LERs/LSRs along the hierarchical LSP.
Native |<------------------- MS-PW1Z ------------------->| Native
Layer | | Layer
Service | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | Service
(AC1) V V LSP V V LSP V V LSP V V (AC2)
+----+ +-+ +----+ +----+ +-+ +----+
+----+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +----+
| | | |=========| |=========| |=========| | | |
| CE1|---|........PW13.......|...PW3X..|........PWXZ.......|---|CE2 |
| | | |=========| |=========| |=========| | | |
+----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+
+----+ +-+ +----+ +----+ +-+ +----+
. . . .
| | | |
|<---- Domain 1 --->| |<---- Domain Z --->|
^------------------- PW1Z PME -------------------^
^---- PW13 PPSTME---^ ^---- PWXZ PPSTME---^
^---------^ ^---------^
PSN13 LME PSNXZ LME
^---^ ^---^ ^---------^ ^---^ ^---^
Sec12 Sec23 Sec3X SecXY SecYZ
SME SME SME SME SME
TPE1: Terminating Provider Edge 1 SPE2: Switching Provider Edge 3
TPEX: Terminating Provider Edge X SPEZ: Switching Provider Edge Z
^---^ ME ^ MEP ==== LSP .... PW
Figure 3 Reference Model for the MPLS-TP OAM Framework
Figure 3 depicts a high-level reference model for the MPLS-TP OAM
framework. The figure depicts portions of two MPLS-TP enabled network
domains, Domain 1 and Domain Z. In Domain 1, LSR1 is adjacent to LSR2
via the MPLS Section Sec12 and LSR2 is adjacent to LSR3 via the MPLS
Section Sec23. Similarly, in Domain Z, LSRX is adjacent to LSRY via
the MPLS Section SecXY and LSRY is adjacent to LSRZ via the MPLS
Section SecYZ. In addition, LSR3 is adjacent to LSRX via the MPLS
Section 3X.
Figure 3 also shows a bi-directional MS-PW (PW1Z) between AC1 on TPE1
and AC2 on TPEZ. The MS-PW consists of three bi-directional PW
Segments: 1) PW13 segment between T-PE1 and S-PE3 via the bi-
directional PSN13 LSP, 2) PW3X segment between S-PE3 and S-PEX, via
the bi-directional PSN3X LSP, and 3) PWXZ segment between S-PEX and
T-PEZ via the bi-directional PSNXZ LSP.
The MPLS-TP OAM procedures that apply to an MEG of a given transport
path are expected to
operate independently from procedures on other
MEGs of the same transport path and certainly MEGs of other transport
paths. MEGs. Yet, this does
not preclude that multiple MEGs may be affected simultaneously by the
same network condition, for example, a fiber cut event.
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 be
instantiated on a particular node. In particular, when looking at
Figure 3, it should be possible to configure one or more MEPs on the
same node if that node is the endpoint of one or more MEGs.
Figure 3 does not describe a PW3X PPSTME because typically PSTs are
used to monitor an OAM domain (like PW13 and PWXZ PPSTMEs) rather
than the segment between two OAM domains. However the OAM framework
does not pose any constraints on the way PSTs are instantiated as
long as they are not overlapping.
The subsections below define the MEGs specified in this MPLS-TP OAM
architecture framework document. Unless otherwise stated, all
references to domains, LSRs, MPLS Sections, LSPs, pseudowires and
MEGs in this section are made in relation to those shown in Figure 3.
4.1. MPLS-TP Section Monitoring (SME)
An MPLS-TP Section ME (SME) is an MPLS-TP maintenance entity intended
to an MPLS Section as defined in [11]. An SME may be configured on
any MPLS section. SME OAM packets must fate share with the user data
packets sent over the monitored MPLS Section.
An SME is intended to be deployed for applications where it is
preferable to monitor the link between topologically adjacent (next
hop in this layer network) MPLS (and MPLS-TP enabled) LSRs rather
than monitoring the individual LSP or PW segments traversing the MPLS
Section and the server layer technology does not provide adequate OAM
capabilities.
|<------------------- MS-PW1Z ------------------->|
| |
| |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| |
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 | +----+
+----+ +-+ +----+ +----+ +-+ +----+
^--^ ^--^ ^---------^ ^---^ ^---^
Sec12 Sec23 Sec3X SecXY SecYZ
SME SME SME SME SME
Figure 4 Reference Example of MPLS-TP Section MEs (SME)
Figure 4 3 shows 5 Section MEs configured in the path network between AC1
and AC2:
1. Sec12 ME associated with the MPLS Section between LSR 1 and LSR 2,
2. Sec23 ME associated with the MPLS Section between LSR 2 and LSR 3,
3. Sec3X ME associated with the MPLS Section between LSR 3 and LSR X,
4. SecXY ME associated with the MPLS Section between LSR X and LSR Y,
and
5. SecYZ ME associated with the MPLS Section between LSR Y and LSR Z.
4.2. MPLS-TP LSP End-to-End Monitoring (LME)
An MPLS-TP LSP ME (LME) is an MPLS-TP maintenance entity intended to
monitor an end-to-end LSP between two LERs. An LME may be configured
on any MPLS LSP. LME OAM packets must fate share with user data
packets sent over the monitored MPLS-TP LSP.
An LME is intended to be deployed in scenarios where it is desirable
to monitor an entire LSP between its LERs, rather than, say,
monitoring individual PWs.
|<------------------- MS-PW1Z ------------------->|
| |
| |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| |
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 | +----+
+----+ +-+ +----+ +----+ +-+ +----+
^---------^ ^---------^
PSN13 LME PSNXZ LME
Figure 5 Examples of MPLS-TP LSP MEs (LME)
Figure 5 3 depicts 2 LMEs configured in the path network between AC1 and
AC2: 1) the PSN13 LME between LER 1 and LER 3, and 2) the PSNXZ LME
between LER X and LER Y. Note that the presence of a PSN3X LME in
such a configuration is optional, hence, not precluded by this
framework. For instance, the SPs may prefer to monitor the MPLS-TP
Section between the two LSRs rather than the individual LSPs.
4.3. MPLS-TP LSP Path Segment Tunnel Monitoring (LPSTME)
An MPLS-TP LSP Path Segment Tunnel ME (LPSTME) is an MPLS-TP
maintenance entity intended to monitor an arbitrary part of an LSP
between a given pair of LSRs independently from the end-to-end
monitoring (LME). An LPSTMEE can monitor an LSP segment or
concatenated segment and it may also include the forwarding engine(s)
of the node(s) at the edge(s) of the segment or concatenated segment.
Multiple LPSTMEs MAY be configured on any LSP. The LSRs that
terminate the LPSTME may or may not be immediately adjacent at the
MPLS-TP layer. LPSTME OAM packets must fate share with the user data
packets sent over the monitored LSP segment.
A LPSTME can be defined between the following entities:
o LER and any LSR of a given LSP.
o Any two LSRs of a given LSP.
An LPSTME is intended to be deployed in scenarios where it is
preferable to monitor the behaviour of a part of an LSP or set of
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
administrative boundaries of an MPLS-TP enabled administrative
domain.
|<--------------------- PW1Z -------------------->|
| |
| |<--------------PSN1Z LSP-------------->| |
| |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| |
V V S-LSP V V S-LSP V V S-LSP V V
+----+ +-+ +----+ +----+ +-+ +----+
+----+ | PE1| | | |DBN3| |DBNX| | | | PEZ| +----+
| |AC1| |=======================================| |AC2| |
| CE1|---|......................PW1Z.......................|---|CE2 |
| | | |=======================================| | | |
+----+ | 1 | |2| | 3 | | X | |Y| | Z | +----+
+----+ +-+ +----+ +----+ +-+ +----+
. . . .
| | | |
|<---- Domain 1 --->| |<---- Domain Z --->|
^---------^ ^---------^
PSN13 LPSTME PSNXZ LPSTME
^---------------------------------------^
PSN1Z LME
DBN: Domain Border Node
Figure 6 4 MPLS-TP LSP Path Segment Tunnel ME (LPSTME)
Figure 6 4 depicts a variation of the reference model in Figure 3 where
there is an end-to-end PSN LSP (PSN1Z LSP) between PE1 and PEZ. PSN1Z
LSP consists of, at least, three LSP Concatenated Segments: PSN13,
PSN3X and PSNXZ. In this scenario there are two separate LTCMEs LPSTMEs
configured to monitor the PSN1Z LSP: 1) a LPSTME monitoring the PSN13
LSP Concatenated Segment on Domain 1 (PSN13 LPSTME), and 2) a LPSTME
monitoring the PSNXZ LSP Concatenated Segment on Domain Z (PSNXZ
LPSTME).
It is worth noticing that LPSTMEs can coexist with the LME monitoring
the end-to-end LSP and that LPSTME MEPs and LME MEPs can be
coincident in the same node (e.g. PE1 node supports both the PSN1Z
LME MEP and the PSN13 LPSTME MEP).
4.4. MPLS-TP PW Monitoring (PME)
An MPLS-TP PW ME (PME) is an MPLS-TP maintenance entity intended to
monitor a SS-PW or MS-PW between a pair of T-PEs. A PME MAY be
configured on any SS-PW or MS-PW. PME OAM packets must fate share
with the user data packets sent over the monitored PW.
A PME is intended to be deployed in scenarios where it is desirable
to monitor an entire PW between a pair of MPLS-TP enabled T-PEs
rather than monitoring the LSP aggregating multiple PWs between PEs.
|<------------------- MS-PW1Z ------------------->|
| |
| |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| |
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 7 5 MPLS-TP PW ME (PME)
Figure 7 5 depicts a MS-PW (MS-PW1Z) consisting of three segments:
PW13, PW3X and PWXZ and its associated end-to-end PME (PW1Z PME).
4.5. MPLS-TP MS-PW Path Segment Tunnel Monitoring
[Editors' note: revise this section after the discussion on PW TCM is
closed (discussion item 4 in section 1.2)] (PPSTME)
An MPLS-TP MS-PW Path Segment Tunnel Monitoring ME (PPSTME) is an
MPLS-TP maintenance entity intended to monitor an arbitrary part of
an MS-PW between a given pair of PEs independently from the end-to-
end monitoring (PME). A PPSTME can monitor a PW segment or
concatenated segment and it may also include the forwarding engine(s)
of the node(s) at the edge(s) of the segment or concatenated segment.
Multiple PPSTMEs MAY be configured on any MS-PW. The PEs may or may
not be immediately adjacent at the MS-PW layer. PPSTME OAM packets
fate share with the user data packets sent over the monitored PW
Segment.
A PPSTME can be defined between the following entities:
o T-PE and any S-PE of a given MS-PW
o Any two S-PEs of a given MS-PW. It can span several PW segments.
A PPSTME is intended to be deployed in scenarios where it is
preferable to monitor the behaviour of a part of a MS-PW rather than
the entire end-to-end PW itself, for example to monitor an MS-PW
Segment within a given network domain of an inter-domain MS-PW.
|<------------------- MS-PW1Z ------------------->|
| |
| |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| |
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 | +----+
+----+ +-+ +----+ +----+ +-+ +----+
^---- PW1 PPSTME----^ ^---- PW5 PPSTME----^
^---------------------PW1Z PME--------------------^
Figure 8 6 MPLS-TP MS-PW Path Segment Tunnel Monitoring (PPSTME)
Figure 8 6 depicts the same MS-PW (MS-PW1Z) between AC1 and AC2 as in
Figure 7. 5. In this scenario there are two separate PPSTMEs configured
to monitor MS-PW1Z: 1) a PPSTME monitoring the PW13 MS-PW Segment on
Domain 1 (PW13 PPSTME), and 2) a PTCME PPSTME monitoring the PWXZ MS-PW
Segment on Domain Z with (PWXZ PPSTME).
It is worth noticing that PPSTMEs can coexist with the PME monitoring
the end-to-end MS-PW and that PPSTME MEPs and PME MEPs can be
coincident in the same node (e.g. TPE1 node supports both the PW1Z
PME MEP and the PW13 PPSTME MEP).
5. OAM Functions for proactive monitoring
[Editors' note: at the beginning of each section, reference the
section in the OAM Requirements document and explicitly list
additional detailed requirements wrt the OAM Requirements document]
In this document, proactive monitoring refers to OAM operations that
are either configured to be carried out periodically and continuously
or preconfigured to act on certain events such as alarm signals.
Proactive monitoring is frequently "in service" monitoring. The
control and measurement implications are:
1. Proactive monitoring for a MEG is typically configured at
transport path creation time.
2. The operational characteristics of in-band measurement
transactions (e.g., CV, LM etc.) are configured at the MEPs.
3. Server layer events are reported by transactions originating at
intermediate nodes.
4. The measurements resulting from proactive monitoring are typically
only reported outside of the MEG as unsolicited notifications for
"out of profile" events, such as faults or loss measurement
indication of excessive impairment of information transfer
capability.
5. The measurements resulting from proactive monitoring may be
periodically harvested by an EMS/NMS.
5.1. Continuity Check and Connectivity Verification
Proactive Continuity Check functions functions, as required in section 2.2.2 of
[12], are used to detect a loss of continuity defect (LOC) between
two MEPs in an MEG.
Proactive Connectivity Verification functions functions, as required in section
2.2.3 of [12], are used to detect an unexpected connectivity defect
between two MEGs (e.g. mismerging or misconnection), as well as
unexpected connectivity within the MEG with an unexpected MEP.
Both functions are based on the (proactive) generation of OAM packets
by the source MEP that are processed by the sink MEP. As a
consequence these two functions are grouped together into Continuity
Check and Connectivity Verification (CC-V) OAM packets.
In order to perform pro-active Connectivity Verification function,
each CC-V OAM packet MUST also include a globally unique Source MEP
identifier. When used to perform only pro-active Continuity Check
function, the CC-V OAM packet MAY not include any globally unique
Source MEP identifier identifier. Different formats of MEP identifiers are
defined in [10] to address different environments. When MPLS-TP is
deployed in transport network environments where IP addressing is not
used in the forwarding plane, the ICC-based format for MEP
identification is used. When MPLS-TP is deployed in IP-based
environment, the IP-based MEP identification is used.
As a consequence, it is not possible to detect misconnections between
two MEGs monitored only for Continuity while it is possible continuity as neither the OAM message
type nor OAM message content provides sufficient information to detect
any misconnection between two MEGs monitored for Continuity and
Connectivity or between
disambiguate an MEG invalid source. To expand:
o For CC leaking into a CC monitored for Continuity and
Connectivity and one MEG - undetectable
o For CV leaking into a CC monitored only for Continuity.
[Editor's note MEG - Rephrase presence of additional
Source MEP identifier allows detecting the previous paragraph: describe fault
o For CC leaking into a CV monitored MEG - lack of additional Source
MEP identifier allows detecting the four
cases.] fault.
o For CV leaking into a CV monitored MEG - different Source MEP
identifier permits fault to be identified.
CC-V OAM packets MUST be transmitted at a regular, operator's
configurable, rate. The default CC-V transmission periods are
application dependent (see section 5.1.4). 5.1.3).
Proactive CC-V OAM packets are transmitted with the "minimum loss
probability PHB" within a single network operator. This PHB is
configurable on network operator's basis. PHBs can be translated at
the network borders by the same function that translates it for user
data traffic.
[Editor's note - Describe the relation between the previous paragraph
and the fate sharing requirement. Need to clarify also in the
requirement document The implication is that for proactive CC-V the fate sharing is
related to shares with much of
the forwarding behavior and implementation, but not to the QoS behavior] all aspects of PHB processing
are exercised. On demand tools are used for finer grained fault
finding.
In a bidirectional point-to-point transport path, when a MEP is
enabled to generate pro-active CC-V OAM packets with a configured
transmission rate, it also 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 components of the transport path. In a
unidirectional transport path (either point-to-point or point-to-
multipoint), only the source MEP is enabled to generate CC-V OAM
packets and only the sink MEP is configured to expect these packets
at the configured rate.
MIPs, as well as intermediate nodes not supporting MPLS-TP OAM, are
transparent to the pro-active CC-V information and forward these pro-
active CC-V OAM packets as regular data packets.
It is desirable to not generate spurious alarms during initialization
or tear down; hence the following procedures are recommended. At
initialization, the MEP source function (generating pro-active CC-V
packets) should be enabled prior to the corresponding MEP sink
function (detecting continuity and connectivity defects). When
disabling the CC-V proactive functionality, the MEP sink function
should be disabled prior to the corresponding MEP source function.
5.1.1. Defects identified by CC-V
Pro-active CC-V functions allow a sink MEP to detect the defect
conditions described in the following sub-sections. For all of the
described defect cases, the sink MEP SHOULD notify the equipment
fault management process of the detected defect.
5.1.1.1. Loss Of Continuity defect
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 OAM
packets from the peer MEP.
o Entry criteria: if no pro-active CC-V OAM packets from the peer
MEP (i.e. with the correct globally unique Source MEP identifier)
are received within the interval equal to 3.5 times the receiving
MEP's configured CC-V reception period.
o Exit criteria: a pro-active CC-V OAM packet from the peer MEP
(i.e. with the correct globally unique Source MEP identifier) is
received.
5.1.1.2. Mis-connectivity defect
When a pro-active CC-V OAM packet is received, a sink MEP identifies
a mis-connectivity defect (e.g. mismerge, misconnection or unintended
looping) with its peer source MEP when the received packet carries an
incorrect globally unique Source MEP identifier.
o Entry criteria: the sink MEP receives a pro-active CC-V OAM packet
with an incorrect globally unique Source MEP identifier.
o Exit criteria: the sink MEP does not receive any pro-active CC-V
OAM packet with an incorrect globally unique Source MEP identifier
for an interval equal at least to 3.5 times the longest
transmission period of the pro-active CC-V OAM packets received
with an incorrect globally unique Source MEP identifier since this
defect has been raised. This requires the OAM message to self
identify the CC-V periodicity as not all MEPs can be expected to
have knowledge of all MEGs.
5.1.1.3. Period Misconfiguration defect
If pro-active CC-V OAM packets are received with a correct globally
unique Source MEP identifier but with a transmission period different
than the locally configured reception period, then a CV period mis-
configuration defect is detected.
o Entry criteria: a MEP receives a CC-V pro-active packet with
correct globally unique Source MEP identifier but with a Period
field value different than its own CC-V configured transmission
period.
o Exit criteria: the sink MEP does not receive any pro-active CC-V
OAM packet with a correct globally unique Source MEP identifier
and an incorrect transmission period for an interval equal at
least to 3.5 times the longest transmission period of the pro-
active CC-V OAM packets received with a correct globally unique
Source MEP identifier and an incorrect transmission period since
this defect has been raised.
5.1.2. Consequent action
[editors: IMO this would be better folded into the specific defect
types, If agreed I will edit accordingly]
A sink MEP that detects one of the defect conditions defined in
section 5.1.1 MUST perform the following consequent actions. Some of
these consequent actions SHOULD be enabled/disabled by the operator
depending upon the application used (see section 5.1.4).
If a MEP detects an unexpected globally unique Source MEP Identifier,
it MUST block all the traffic (including also the user data packets)
that it receives from the misconnected transport path.
If a MEP detects LOC defect that is not caused by a period
mis-configuration, it SHOULD block all the traffic (including also
the user data packets) that it receives from the transport path, if
this consequent action has been enabled by the operator.
It is worth noticing that the OAM requirements document [12]
recommends that CC-V proactive monitoring is enabled on every MEG in
order to reliably detect connectivity defects. However, CC-V
proactive monitoring MAY be disabled by an operator on an MEG. In the
event of a misconnection between a transport path that is pro-
actively monitored for CC-V and a transport path which is not, the
MEP of the former transport path will detect a LOC defect
representing a connectivity problem (e.g. a misconnection with a
transport path where CC-V proactive monitoring is not enabled)
instead of a continuity problem, with a consequent wrong traffic
delivering. For these reasons, the traffic block consequent action is
applied even when a LOC condition occurs. This block consequent
action MAY be disabled through configuration. This deactivation of
the block action may be used for activating or deactivating the
monitoring when it is not possible to synchronize the function
activation of the two peer MEPs.
If a MEP detects a LOC defect (section 5.1.1.1), a mis-connectivity
defect (section 5.1.1.2) or a period misconfiguration defect (section
5.1.1.3), it MUST declare a signal fail condition at the transport
path level.
[Editor's note - Transport equipment also performs defect correlation
(as defined in G.806) in order to properly report failures to the
transport NMS]. The current working assumption, to be further
investigated, is that defect correlations are outside the scope of
this document and to be defined in ITU-T documents.]
5.1.3. Configuration considerations
At all MEPs inside a MEG, the following configuration information
needs to be configured when a proactive CC-V function is enabled:
o MEG ID; the MEG identifier to which the MEP belongs;
o MEP-ID; the MEP's own identity inside the MEG;
o list of peer MEPs inside the MEG. For a point-to-point MEG the
list would consist of the single peer MEP ID from which the 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. In case
of the leaf MEP of a p2mp MEG, the list is composed by the root
MEP ID (i.e. each leaf MUST know the root MEP ID from which it
expect to receive the CC-V OAM packets).
o transmission rate; the default CC-V transmission periods are
application dependent (see section 5.1.4)
Note that the reception period is the same as the configured
transmission rate.
o PHB; it identifies the per-hop behaviour of CC-V packet. Proactive
CC-V packets are transmitted with the "minimum loss probability
PHB" previously configured within a single network operator. This
PHB is configurable on network operator's basis. PHBs can be
translated at the network borders.
For statically provisioned transport paths
o transmission rate; the above information default CC-V transmission periods are
statically configured; for dynamically established transport paths
the configuration information
application dependent (depending on whether they are signaled via the control plane.
5.1.4. Applications for proactive CC-V
CC-V is applicable for used to
support fault management, performance monitoring, or protection
switching applications. applications):
o Fault Management: default transmission period is 1s (i.e.
transmission rate of 1 packet/second).
o Performance Monitoring: default transmission period is 100ms
(i.e. transmission rate of 10 packets/second). Performance
monitoring is only relevant when the transport path is defect
free. CC-V contributes to the accuracy of PM statistics by
permitting the defect free periods to be properly
distinguished.
o Protection Switching: default transmission period is 3.33ms
(i.e. transmission rate of 300 packets/second), in order to
achieve sub-
50ms sub-50ms the CC-V defect entry criteria should resolve
in less than 10msec, and complete a protection switch within a
subsequent period of 50 msec.
It SHOULD be possible for the operator to configure these
transmission rates for all applications, to satisfy his internal
requirements.
In addition,
Note that the reception period is the same as the configured
transmission rate.
For statically provisioned transport paths the above information are
statically configured; for dynamically established transport paths
the configuration information are signaled via the control plane.
The operator should SHOULD be able to define enable/disable some of the consequent
action to be performed for each of these applications.
actions defined in section 5.1.2.
5.2. Remote Defect Indication
The Remote Defect Indication (RDI) function, as required in section
2.2.9 of [12], is an indicator that is transmitted by a MEP to
communicate to its peer MEPs that a signal fail condition exists.
RDI is only used for bidirectional connections and is associated with
proactive CC-V activation. The RDI indicator is piggy-backed onto the
CC-V packet.
When a MEP detects a signal fail condition (e.g. in case of a
continuity or connectivity defect), it should begin transmitting an
RDI indicator to its peer MEP. The RDI information will be included
in all pro-active CC-V packets that it generates for the duration of
the signal fail condition's existence.
[Editor's note - Add some forward compatibility information to cover
the case where future OAM mechanisms that contributes to the signal
fail detection (and RDI generation) are defined.]
the signal fail condition's existence.
A MEP that receives the packets with the RDI information should
determine that its peer MEP has encountered a defect condition
associated with a signal fail.
MIPs as well as intermediate nodes not supporting MPLS-TP OAM are
transparent to the RDI indicator and forward these proactive CC-V
packets that include the RDI indicator as regular data packets, i.e.
the MIP should not perform any actions nor examine the indicator.
When the signal fail defect condition clears, the MEP should clear
the RDI indicator from subsequent transmission of pro-active CC-V
packets. A MEP should clear the RDI defect upon reception of a pro-
active CC-V packet from the source MEP with the RDI indicator
cleared.
5.2.1. Configuration considerations
In order to support RDI indication, this may be a unique OAM message
or an OAM information element embedded in a CV message. In this case
the RDI transmission rate and PHB of the OAM packets carrying RDI
should be the same as that configured for CC-V.
5.2.2. Applications for Remote Defect Indication
RDI is applicable for the following applications:
o Single-ended fault management - A MEP that receives an RDI
indication from its peer MEP, can report a far-end defect
condition (i.e. the peer MEP has detected a signal fail condition
in the traffic direction from the MEP that receives the RDI
indication to the peer MEP that has sent the RDI information).
o Contribution to far-end performance monitoring - The indication of
the far-end defect condition is used as a contribution to the
bidirectional performance monitoring process.
5.3. Alarm Reporting
The Alarm Reporting function function, as required in section 2.2.8 of [12],
relies upon an Alarm Indication Signal (AIS) message used to suppress
alarms following detection of defect conditions at the server
(sub-)layer.
o A server MEP that detects a signal fail conditions in the server
(sub-)layer, will notify the MPLS-TP client (sub-)layer adaptation
function, which can generate packets with AIS information in a
direction opposite to its peers MEPs to allow the suppression of
secondary alarms at the MEP in the client (sub-)layer.
A server MEP is responsible for notifying the MPLS-TP layer network
adaptation function upon fault detection in the server layer network
to which the server MEP is associated.
Only the client layer adaptation function at an intermediate node
will issue MPLS-TP packets with AIS information. Upon receiving
notification of a signal fail condition the adaptation function
SHOULD immediately start transmitting periodic packets with AIS
information. These periodic packets, with AIS information, continue
to be transmitted until the signal fail condition is cleared.
Upon receiving a packet with AIS information an MPLS-TP MEP enters an
AIS defect condition and suppresses loss of continuity alarms
associated with its peer MEP. A MEP resumes loss of continuity alarm
generation upon detecting loss of continuity defect conditions in the
absence of AIS condition.
For example, let's consider a fiber cut between LSR 1 and LSR 2 in
the reference network of Figure 3. Assuming that all the MEGs
described in Figure 3 have pro-active CC-V enabled, a LOC defect is
detected by the MEPs of Sec12 SME, PSN13 LME, PW1 PTCME PPSTME and PW1Z
PME, however in transport network only the alarm associate to the
fiber cut needs to be reported to NMS while all these secondary
alarms should be suppressed (i.e. not reported to the NMS or reported
as secondary alarms).
If the fiber cut is detected by the MEP in the physical layer (in
LSR2), LSR2 can generate the proper alarm in the physical layer and
suppress the secondary alarm associated with the LOC defect detected
on Sec12 SME. As both MEPs reside within the same node, this process
does not involve any external protocol exchange. Otherwise, if the
physical layer has not enough OAM capabilities to detect the fiber
cut, the MEP of Sec12 SME in LSR2 will report a LOC alarm.
In both cases, the MEP of Sec12 SME in LSR 2 notifies the adaptation
function for PSN13 LME that then generates AIS packets on the PSN13
LME in order to allow its MEP in LSR3 to suppress the LOC alarm. LSR3
can also suppress LOC alarm. LSR3
can also suppress the secondary alarm on PW13 PPSTME because the MEP
of PW13 PPSTME resides within the same node as the MEP of PSN13 LME.
The MEP of PW13 PPSTME in LSR3 also notifies the adaptation function
for PW1Z PME that then generates AIS packets on PW1Z PME in order to
allow its MEP in LSRZ to suppress the LOC alarm.
The generation of AIS packets for each MEG in the client (sub-)layer
is configurable (i.e. the operator can enable/disable the AIS
generation).
AIS packets are transmitted with the "minimum loss probability PHB"
within a single network operator. This PHB is configurable on network
operator's basis.
A MIP is transparent to packets with AIS information and therefore
does not require any information to support AIS functionality.
5.4. Lock Reporting
The Lock Reporting function, as required in section 2.2.7 of [12],
relies upon a Locked Report (LKR) message used to suppress alarms
following administrative locking action in the server (sub-)layer.
A server MEP is responsible for notifying the MPLS-TP layer network
adaption function upon locked condition applied to the secondary alarm on PW13 PPSTME because server layer
network to which the server MEP
of PW13 PPSTME resides within is associated.
Only the same client layer adaptation function at an intermediate node as the MEP of PSN13 LME.
The MEP
will issue MPLS-TP packets with LKR information. Upon receiving
notification of PW13 PPSTME in LSR3 also notifies a locked condition the adaptation function
for PW1Z PME that then generates AIS SHOULD
immediately start transmitting periodic packets on PW1Z PME in order with LKR information.
These periodic packets, with LKR information, will continue to
allow be
transmitted until the locked condition is cleared.
Upon receiving a packet with LKR information an MPLS-TP MEP enters an
LKR defect condition and suppresses loss of continuity alarm
associated with its peer MEP. A MEP resumes loss of continuity alarm
generation upon detecting loss of continuity defect conditions in LSRZ to suppress the LOC alarm.
absence of LKR condition.
The generation of AIS LKR packets for each MEG is configurable in the client server
(sub-)layer
is configurable (i.e. the operator can enable/disable the AIS LKR
generation).
AIS
LKR packets are transmitted with the "minimum loss probability PHB"
within a single network operator. This PHB is configurable on network
operator's basis.
A MIP is transparent to packets with AIS LKR information and therefore
does not require any information to support AIS LKR functionality.
5.4. Lock Reporting
To be incorporated in a future revision of this document
5.5. Packet Loss Monitoring Measurement
Packet Loss Monitoring Measurement (LM) is one of the capabilities supported by
the MPLS-TP Performance Monitoring (PM) function in order to
facilitate reporting of QoS information for a transport path. path as
required in section 2.2.11 of [12]. LM is used to exchange counter
values for the number of ingress and egress packets transmitted and
received by the transport path monitored by a pair of MEPs.
Proactive LM is performed by periodically sending LM OAM packets from
a MEP to a peer MEP and by receiving LM OAM packets from the peer MEP
(if a bidirectional transport path) during the life time of the
transport path. Each MEP performs measurements of its transmitted and
received packets. These measurements are then transactionally
correlated 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
transactions are issued such that the OAM packets will experience the
same queuing discipline as the measured traffic while transiting
between the MEPs in the ME.
For a MEP, near-end packet loss refers to packet loss associated with
incoming data packets (from the far-end MEP) while far-end packet
loss refers to packet loss associated with egress data packets
(towards the far-end MEP).
5.5.1. Configuration considerations
In order to support proactive LM, the transmission rate and PHB
associated with the LM OAM packets originating from a MEP need be
configured as part of the LM provisioning procedures. LM OAM packets
should be transmitted with the same PHB class that yields the lowest packet loss
performance among the PHB Scheduling Classes or Ordered Aggregates
(see RFC 3260 [15]) in the monitored transport path for the relevant
network domain(s).
5.5.2. Applications for Packet Loss Monitoring LM is relevant for the following applications:
o Single or double-end performance monitoring: determination of intended
to measure. If that PHB is not an ordered aggregate where the
packet loss performance of a transport path for Service Level
Agreement (SLA) verification purposes.
o Single or double-end performance monitoring: determination of
ordering constraint is all packets with the
packet loss performance of a PHB Scheduling Class or Ordered
Aggregate within a transport path.
o Contribution to service unable time. Both near-end and far-end
packet loss measurements contribute to performance metrics such as
near-end severely errored seconds (Near-End SES) and far-end
severely errored seconds (Far-End SES) respectively, which
together contribute to unavailable time, being delivered in a manner similar to
Recommendation G.826 [19] and Recommendation G.7710 [20].
order, LM can produce inconsistent results.
5.6. Client Signal Failure Indication
The Client Signal Failure Indication (CSF) function function, as required in section
2.2.10 of [12], is used to help process client defects and propagate
a client signal defect condition from the process associated with the
local attachment circuit where the defect was detected (typically the
source adaptation function for the local client interface) to the
process associated with the far-
end far-end attachment circuit (typically the
source adaptation function for the far-end client interface) for the
same transmission path in case the client of the transmission transport path does
not support a native defect/alarm indication mechanism, e.g. FDI/AIS.
[Editor's note - The need to support this function on the LSP layer
(and not only at the PW layer) needs to be further investigated.
Pending discussion on MPLS-TP clients in the main framework
document.] AIS.
A source MEP starts transmitting a CSF indication to its peer MEP
when it receives a local client signal defect notification via its
local CSF function. Mechanisms to detect local client signal fail
defects are technology specific.
A sink MEP that has received a CSF indication report this condition
to its associated client process via its local CSF function.
Consequent actions toward the client attachment circuit are
technology specific.
Either there needs to be a 1:1 correspondence between the client and
the MEG, or when multiple clients are multiplexed over a transport
path, the CSF message requires additional information to permit the
client instance to be identified.
5.6.1. Configuration considerations
In order to support CSF indication, the CSF transmission rate and PHB
of the CSF OAM message/information element should be configured as
part of the CSF configuration.
5.6.2. Applications for Client Signal Failure Indication
CSF is applicable for the following applications:
o Single-ended fault management - A MEP that receives a CSF
indication from its peer MEP, can report a far-end client defect
condition (i.e. the peer MEP has been informed of local client
signal fail condition in the traffic direction from the client to
the peer MEP that transmitted the CSF).
o Contribution to far-end performance monitoring - The indication of
the far-end defect condition may be used to account on network
operator contribution to the bidirectional performance monitoring
process.
CSF supports the application described in Appendix VIII of ITU-T
G.806 [18].
5.7. Packet Delay Measurement
Packet Delay Measurement (DM) is one of the capabilities supported by
the MPLS-TP PM function in order to facilitate reporting of QoS
information for a transport path. path as required in section 2.2.12 of
[12]. Specifically, pro-active DM is used to measure the long-term
packet delay and packet delay variation in the transport path
monitored by a pair of MEPs.
Proactive DM is performed by sending periodic DM OAM packets from a
MEP to a peer MEP and by receiving DM OAM packets from the peer MEP
(if a bidirectional transport path) during a configurable time
interval.
Pro-active DM can be operated in two ways:
o One-way: a MEP sends DM OAM packet to its peer MEP containing all
the required information to facilitate one-way packet delay and/or
one-way packet delay variation measurements at the peer MEP. Note
that this requires synchronized precision time at either MEP by
means outside the scope of this framework.
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 response. The
request/response DM OAM packets containing all the required
information to facilitate two-way packet delay and/or two-way
packet delay variation measurements from the viewpoint of the
source MEP.
5.7.1. Configuration considerations
In order to support pro-active DM, the transmission rate and PHB
associated with the DM OAM packets originating from a MEP need be
configured as part of the DM provisioning procedures. DM OAM packets
should be transmitted with the PHB that yields the lowest packet loss
performance among the PHB Scheduling Classes or Ordered Aggregates
(see RFC 3260 [15]) in the monitored transport path for the relevant
network domain(s).
5.7.2. Applications for Delay Measurement
DM is relevant for the following applications:
o Single or double-end performance monitoring: determination of the
delay performance of a transport path for SLA verification
purposes.
o Single or double-end performance monitoring: determination of the
delay performance of a PHB Scheduling Class or Ordered Aggregate
within a transport path
6. OAM Functions for on-demand monitoring
[Editors' note: at the beginning of each section, reference the
section in the OAM Requirements document and explicitly list
additional detailed requirements wrt monitored transport path for the relevant
network domain(s).
6. OAM Requirements document] Functions for on-demand monitoring
In contrast to proactive monitoring, on-demand monitoring is
initiated manually and for a limited amount of time, usually for
operations such as e.g. diagnostics to investigate into a defect
condition.
On-demand monitoring covers a combination of "in service" and "out-of
service" monitoring functions. The control and measurement
implications are:
1. A MEG can be directed to perform an "on demand" functions at
arbitrary times in the lifetime of a transport path.
2. "out of service" monitoring functions may require a-priori
configuration of both MEPs and intermediate nodes in the MEG
(e.g., data plane loopback) and the issuance of notifications into
client layers of the transport path being removed from service
(e.g., lock-reporting)
3. The measurements resulting from on-demand monitoring are typically
harvested in real time, as these are frequently craftsperson
initiated and attended. These do not necessarily require different
harvesting mechanisms that that for harvesting proactive
monitoring telemetry.
6.1. Connectivity Verification
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. packets, as required
in section 2.2.3 of [12].
Use of on-demand CV is dependent on the existence of either a bi-directional bi-
directional MEG, because it requires or the presence availability of a return path in the data
plane.[Editors': needs to be revised on the basis an out of the band return path
discussion (discussion item 7 in section 1.2]
[Editor's note - Clarify in
because it requires the sentence above ability for target MIPs and within the
paragraph that on-demand CV requires a return path MEPs to send back the
reply direct
responses to on-demand CV packets] the originating MEPs.
An additional use of on-demand CV would be to detect and locate a
problem of connectivity when a problem is suspected or known based on
other tools. In this case the functionality will be triggered by the
network management in response to a status signal or alarm
indication.
On-demand CV is based upon generation of on-demand CV packets that
should uniquely identify the MEG that is being checked. The on-
demand functionality may be used to check either an entire MEG (end-
to-end) or between a MEP to a specific MIP. This functionality may
not be available for associated bidirectional paths transport paths, as the
MIP may not have a return path to the source MEP for the on-demand CV
transaction.
On-demand CV may generate a one-time burst of on-demand CV packets,
or be used to invoke periodic, non-continuous, bursts of on-demand CV
packets. The number of packets generated in each burst is
configurable at the MEPs, and should take into account normal packet-
loss conditions.
When invoking a periodic check of the MEG, the source MEP should
issue a burst of on-demand CV packets that uniquely identifies the
MEG being verified. The number of packets and their transmission
rate should be pre-configured and known to both the source MEP and
the target MEP or MIP. The source MEP should use the TTL field to
indicate the number of hops necessary, when targeting a MIP mechanisms
defined in sections 3.3 and use
the default value 3.4 when performing sending an end-to-end check [IB => This is
quite generic for addressing packets to MIPs and MEPs so it is better on-demand CV packet
to move this text in section 2]. a target MEP or target MIP respectively. The target MEP/MIP shall
return a reply on-demand CV packet for each packet received. If the
expected number of on-demand CV reply packets is not received at
source MEP, the LOC defect state is entered.
[Editor's note - We need to add some text for
On demand CV should have the usage ability to carry padding such that a
variety of on-demand
CV with different packet sizes, e.g. MTU sizes can be originated to discover verify the MTU problems.] capacity of
the transport path.
6.1.1. Configuration considerations
For on-demand CV the MEP should support the configuration of the
number of packets to be transmitted/received in each burst of
transmissions and their packet size. The transmission rate should be
configured between the different nodes.
In addition, when the CV packet is used to check connectivity toward
a target MIP, the number of hops to reach the target MIP should be
configured.
The PHB of the on-demand CV packets should be configured as well.
[Editor's note - We need to be better define
This permits the reason for such
configuration] verification of correct operation of QoS queuing as
well as connectivity.
6.2. Packet Loss Monitoring Measurement
On-demand Packet Loss Measurement (LM) is one of the capabilities
supported by the MPLS-TP Performance Monitoring function in order to
facilitate diagnostic of QoS performance for a transport path. path, as
required in section 2.2.11 of [12]. As proactive LM, on-demand LM is
used to exchange counter values for the number of ingress and egress
packets transmitted and received by the transport path monitored by a
pair of MEPs.
On-demand LM is performed by periodically sending LM OAM packets from
a MEP to a peer MEP and by receiving LM OAM packets from the peer MEP
(if a bidirectional transport path) during a pre-defined monitoring
period. Each MEP performs measurements of its transmitted and
received packets. These measurements are then correlated evaluate the
packet loss performance metrics of the transport path.
6.2.1. Configuration considerations
In order to support on-demand LM, the beginning and duration of the
LM procedures, the transmission rate and PHB associated with the LM
OAM packets originating from a MEP must be configured as part of the
on-demand LM provisioning procedures. LM OAM packets should be
transmitted with the PHB that yields the lowest packet loss
performance among the PHB Scheduling Classes or Ordered Aggregates
(see RFC 3260 [15]) in the monitored transport path for the relevant
network domain(s).
6.2.2. Applications for On-demand Packet Loss Monitoring
On-demand LM
6.3. Diagnostic Tests
6.3.1. Throughput Estimation
Throughput estimation is relevant for the following applications:
o Single-end performance monitoring: diagnostic an on-demand out-of-service function, as
required in section 2.2.5 of [12], that allows verifying the packet loss
performance
bandwidth/throughput of a an MPLS-TP transport path for SLA trouble shooting purposes.
o Single-end performance monitoring: diagnostic (LSP or PW) before
it is put in-service.
Throughput estimation is performed between MEPs and can be performed
in one-way or two way modes.
This test is performed by sending OAM test packets at increasing rate
(up to the theoretical maximum), graphing the percentage of OAM test
packets received and reporting the rate at which OAM test packets
start begin dropped. In general, this rate is dependent on the OAM
test packet loss
performance of size.
When configured to perform such tests, a PHB Scheduling Class or Ordering Aggregate within MEP source inserts OAM test
packets with test information with specified throughput, packet size
and transmission patterns.
For one way test, remote MEP sink receives the OAM test packets and
calculates the packet loss. For two way test, the remote MEP
loopbacks the OAM test packets back to original MEP and the local MEP
sink calculates the packet loss.
6.3.1.1. Configuration considerations
Throughput estimation is an out-of-service tool. The diagnosed MEG
should be put into a transport path for QoS trouble shooting purposes.
6.3. Diagnostic
To Lock status before the diagnostic test is
started.
An MEG can be incorporated put into a Lock status either via NMS action or using
the Lock Instruct OAM tool as defined in section 6.6.
At the transmitting MEP, provisioning is required for a test signal
generator, which is associated with the MEP. At a receiving MEP,
provisioning is required for a future revision of this document
[Editors' note: describe an test signal detector which is
associated with the MEP.
A MIP is transparent to the OAM tool test packets sent for throughput throught
estimation (out-
of-service): works in one-way and two-way modes]
[Editors' note: Need further investigation about the need to support
a data-plane loopback. If needed, which layer therefore does have not require any provisioning to support
this function (i.e. the
MPLS-TP layer or its server layer?) It is
also needed to understand whether it is needed to specify where this
data-plane throghtput estimation.
6.3.2. Data plane Loopback
Data plane loopback takes place within the equipment]
[Munich: Need to describe the two types is an out-of-service function, as required in
section 2.2.5 of loopback - LBM/LBR and [12], that permits traffic loopback enhanced with variable sized packets in originated at the on
demand cases.
One objective ingress
of diags is fault location, we need to make clear how
we apply the tools a transport path to fault location.
At the top of each section we need be looped back to describe the detailed
requirements and then in the rest point of origin by an
interface at either an intermediate node or a terminating node.
If the section describe how loopback function is to be performed at an intermediate node
it is
met.]
6.4. Route Tracing
[Editors' note: The framework needs only applicable to say what you need co-routed bi-directional paths. If the
loopback is to trace and
not how you do be performed end to end, it (remove the description of the solution).]
[Editors' note: Need is applicable to investigate if we need both tracing options:
describe why and co-
routed bi-directional or associated bi-directional paths.
Where a sketch of the two options node implements data plane loopback capability and their properties.
Possible reasons for both options:
o TTL incremental tells whether the CP is correct or not
o the second it
implements more than one (path discovery) point is ...
Action: check on the mailing list the need to support both modes of
operations.]
After e.g. provisioning an MPLS-TP LSP or for trouble shooting
purposes, it implementation dependent.
6.4. Route Tracing
It is often necessary to trace a route covered by an ME MEG from a
source MEP to the sink MEP including all the MIPs in-between. in-between after
e.g., provisioning an MPLS-TP transport path or for trouble shooting
purposes, it.
The route tracing function function, as required in section 2.2.4 of [12], is
providing this functionality. Based on the fate sharing requirement
of OAM flows, i.e. OAM packets receive the same forwarding treatment
as data packet, route tracing is a basic means to perform CV
connectivity verification and, to a much lesser degree, CC. continuity
check. For this function to work properly, a return path must be
present.
Route tracing might be implemented in different ways and this
document does not preclude any of them.
Route trace could be
implemented e.g. by an MPLS traceroute-like function [RFC4379].
However, route tracing should always return discover the full list of MIPs and of the
peer MEP in it answer(s). MEPs. In case a defect exist, the route trace function needs to
be able to detect it and stop automatically returning the incomplete
list of OAM entities that it was able to trace.
6.4.1. Configuration considerations
The configuration of the route trace function must at least support
the setting of the trace depth (number of hops)_and the number of trace attempts before it gives up. Default setting need to be
configurable by the operator, too.
6.5. Packet Delay Measurement
Packet Delay Measurement (DM) is one of the capabilities supported by
the MPLS-TP PM function in order to facilitate reporting of QoS
information for a transport path. path, as required in section 2.2.12 of
[12]. Specifically, on-demand DM is used to measure packet delay and
packet delay variation in the transport path monitored by a pair of
MEPs during a pre-defined monitoring period.
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 the peer MEP
(if a bidirectional transport path) during a configurable time
interval.
On-demand DM can be operated in two ways:
o One-way: a MEP sends DM OAM packet to its peer MEP containing all
the required information to facilitate one-way packet delay and/or
one-way packet delay variation measurements at the peer MEP.
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 response. The
request/response DM OAM packets containing all the required
information to facilitate two-way packet delay and/or two-way
packet delay variation measurements from the viewpoint of the
source MEP.
6.5.1. Configuration considerations
In order to support on-demand DM, the beginning and duration of the
DM procedures, the transmission rate and PHB associated with the DM
OAM packets originating from a MEP need be configured as part of the
LM provisioning procedures. DM OAM packets should be transmitted with
the PHB that yields the lowest packet delay performance among the PHB
Scheduling Classes or Ordering Aggregates (see RFC 3260 [15]) in the
monitored
monitored transport path for the relevant network domain(s).
In order to verify different performances between long and short
packets (e.g., due to the processing time), it SHOULD be possible for
the operator to configure of the on-demand OAM DM packet.
6.6. Lock Instruct
Lock Instruct (LKI) function, as required in section 2.2.6 of [12],
is a command allowing a MEP to instruct the peer MEP(s) to put the
MPLS-TP transport path into a locked condition.
This function allows single-side provisioning for administratively
locking (and unlocking) an MPLS-TP transport path.
Note that it is also possible to administratively lock (and unlock)
an MPLS-TP transport path using two-side provisioning, where the NMS
administratively put both MEPs into ad administrative lock condition.
In this case, the LKI function is not required/used.
6.6.1. Locking a transport path
A MEP, upon receiving a single-side administrative lock command from
NMS, sends an LKI request OAM packet to its peer MEP(s). It also puts
the MPLS-TP transport path into a locked and notify its client
(sub-)layer adaptation function upon the locked condition.
A MEP, upon receiving an LKI request from its peer MEP, can accept or
not the instruction and MUST reply to the peer MEP with an LKI reply
OAM packet indicating whether it has accepted or not the instruction.
If the lock instruction has been accepted, it also puts the MPLS-TP
transport path into a locked and notify its client (sub-)layer
adaptation function upon the locked condition.
Note that if the client (sub-)layer is also MPLS-TP, Lock Reporting
(LKR) generation at the client MPLS-TP (sub-)layer is started, as
described in section 5.4.
6.6.2. Unlocking a transport path for the relevant network domain(s).
In order to verify different performances between long and short
packets (e.g., due
A MEP, upon receiving a single-side administrative unlock command
from NMS, sends an LKI removal request OAM packet to its peer MEP(s).
The peer MEP, upon receiving an LKI removal request, can accept or
not the processing time), removal instruction and MUST reply with an LKI removal reply
OAM packet indicating whether it SHOULD be possible for has accepted or not the operator to configure of instruction.
If the on-demand OAM DM packet.
6.5.2. Applications for Delay Measurement
DM is relevant for lock removal instruction has been accepted, it also clears the following applications:
o Single or double-end performance monitoring: determination of
locked condition on the
packet delay and/or delay variation performance of a MPLS-TP transport path for SLA verification purposes.
o Single or double-end performance monitoring: determination of and notify this event
to its client (sub-)layer adaptation function.
The MEP that has initiated the
packet delay and/or delay variation a PHB Scheduling Class or
Ordering Aggregate within LKI clear procedure, upon receiving a
positive LKI removal reply, also clears the locked condition on the
MPLS-TP transport path
o Contribution to service unable time. Packet delay measurements may
contribute to performance metrics such as near-end severely
errored seconds (Near-End SES) and far-end severely errored
seconds (Far-End SES), which together contribute notify this event to unavailable
time.
6.6. its client
(sub-)layer adaptation function.
Note that if the client (sub-)layer is also MPLS-TP, Lock Instruct
To be incorporated Reporting
(LKR) generation at the client MPLS-TP (sub-)layer is terminated, as
described in a future revision of this document section 5.4.
7. Security Considerations
A number of security considerations are important in the context of
OAM applications.
OAM traffic can reveal sensitive information such as passwords,
performance data and details about e.g. the network topology. The
nature of OAM data therefore suggests to have some form of
authentication, authorization and encryption in place. This will
prevent unauthorized access to vital equipment and it will prevent
third parties from learning about sensitive information about the
transport network.
Mechanisms that the framework does not specify might be subject to
additional security considerations.
8. IANA Considerations
No new IANA considerations.
9. Acknowledgments
The authors would like to thank all members of the teams (the Joint
Working Team, the MPLS Interoperability Design Team in IETF and the
T-MPLS Ad Hoc Group in ITU-T) involved in the definition and
specification of MPLS Transport Profile.
The editors gratefully acknowledge the contributions of Adrian
Farrel, Yoshinori Koike and Luca Martini for per-interface MIPs and
MEPs description.
The editors gratefully acknowledge the contributions of Malcolm
Betts, Yoshinori Koike, Xiao Min, and Maarten Vissers for the lock
report and lock instruction description.
The authors would also like to thank Malcolm Betts, Stewart Bryant,
Rui Costa, Adrian Farrel, Liu Gouman, Feng Huang, Yoshionori Koike,
Yuji Tochio, Maarten Vissers and Xuequin Wei for their comments and
enhancements to the text.
This document was prepared using 2-Word-v2.0.template.dot.
10. References
10.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997
[2] Rosen, E., Viswanathan, A., Callon, R., "Multiprotocol Label
Switching Architecture", RFC 3031, January 2001
[3] Rosen, E., et al., "MPLS Label Stack Encoding", RFC 3032,
January 2001
[4] Agarwal, P., Akyol, B., "Time To Live (TTL) Processing in
Multi-Protocol Label Switching (MPLS) Networks", RFC 3443,
January 2003
[5] Bryant, S., Pate, P., "Pseudo Wire Emulation Edge-to-Edge
(PWE3) Architecture", RFC 3985, March 2005
[6] Nadeau, T., Pignataro, S., "Pseudowire Virtual Circuit
Connectivity Verification (VCCV): A Control Channel for
Pseudowires", RFC 5085, December 2007
[7] Bocci, M., Bryant, S., "An Architecture for Multi-Segment
Pseudo Wire Emulation Edge-to-Edge", draft-ietf-pwe3-ms-pw-
arch-05 (work in progress), September 2008
[8] Bocci, M., et al., "A Framework for MPLS in Transport
Networks", draft-ietf-mpls-tp-framework-06 draft-ietf-mpls-tp-framework-10 (work in progress),
October 2009
February 2010
[9] Vigoureux, M., Bocci, M., Swallow, G., Ward, D., Aggarwal, R.,
"MPLS Generic Associated Channel", RFC 5586, June 2009
[10] Swallow, G., Bocci, M., "MPLS-TP Identifiers", draft-ietf-mpls-
tp-identifiers-00 (work in progress), November 2009
10.2. Informative References
[11] Niven-Jenkins, B., Brungard, D., Betts, M., sprecher, N., Ueno,
S., "MPLS-TP Requirements", RFC 5654, September 2009
[12] Vigoureux, M., Betts, M., Ward, D., "Requirements for OAM in
MPLS Transport Networks", draft-ietf-mpls-tp-oam-requirements-
03
06 (work in progress), August 2009 March 2010
[13] Sprecher, N., Nadeau, T., van Helvoort, H., Weingarten, Y.,
"MPLS-TP OAM Analysis", draft-ietf-mpls-tp-oam-analysis-00 draft-ietf-mpls-tp-oam-analysis-01
(work in progress), November 2009 March 2010
[14] Nichols, K., Blake, S., Baker, F., Black, D., "Definition of
the Differentiated Services Field (DS Field) in the IPv4 and
IPv6 Headers", RFC 2474, December 1998
[15] Grossman, D., "New terminology and clarifications for
Diffserv", RFC 3260, April 2002.
[16] ITU-T Recommendation G.707/Y.1322 (01/07), "Network node
interface for the synchronous digital hierarchy (SDH)", January
2007
[17] ITU-T Recommendation G.805 (03/00), "Generic functional
architecture of transport networks", March 2000
[18] ITU-T Recommendation G.806 (01/09), "Characteristics of
transport equipment - Description methodology and generic
functionality ", January 2009
[19] ITU-T Recommendation G.826 (12/02), "End-to-end error
performance parameters and objectives for international,
constant bit-rate digital paths and connections", December 2002
[20] ITU-T Recommendation G.7710 (07/07), "Common equipment
management function requirements", July 2007
[21] ITU-T Recommendation Y.2611 (06/12), " High-level architecture
of future packet-based networks", 2006
Authors' Addresses
Dave Allan (Editor)
Ericsson
Email: david.i.allan@ericsson.com
Italo Busi (Editor)
Alcatel-Lucent
Email: Italo.Busi@alcatel-lucent.com
Ben Niven-Jenkins (Editor)
BT
Email: benjamin.niven-jenkins@bt.com
Contributing Authors' Addresses
Annamaria Fulignoli
Ericsson
Email: annamaria.fulignoli@ericsson.com
Enrique Hernandez-Valencia
Alcatel-Lucent
Email: Enrique.Hernandez@alcatel-lucent.com
Lieven Levrau
Alcatel-Lucent
Email: Lieven.Levrau@alcatel-lucent.com
Dinesh Mohan
Nortel
Email: mohand@nortel.com
Vincenzo Sestito
Alcatel-Lucent
Email: Vincenzo.Sestito@alcatel-lucent.com
Nurit Sprecher
Nokia Siemens Networks
Email: nurit.sprecher@nsn.com
Huub van Helvoort
Huawei Technologies
Email: hhelvoort@huawei.com
Martin Vigoureux
Alcatel-Lucent
Email: Martin.Vigoureux@alcatel-lucent.com
Yaacov Weingarten
Nokia Siemens Networks
Email: yaacov.weingarten@nsn.com
Rolf Winter
NEC
Email: Rolf.Winter@nw.neclab.eu