One document matched: draft-ietf-mpls-tp-oam-framework-02.txt
Differences from draft-ietf-mpls-tp-oam-framework-01.txt
MPLS Working Group I. Busi (Ed)
Internet Draft Alcatel-Lucent
Intended status: Informational B. Niven-Jenkins (Ed)
BT
D. Allan (Ed)
Ericsson
Expires: April 2010 October 26, 2009
MPLS-TP OAM Framework
draft-ietf-mpls-tp-oam-framework-02.txt
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that other
groups may also distribute working documents as Internet-Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress".
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
Copyright Notice
Copyright (c) 2009 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents in effect on the date of
publication of this document (http://trustee.ietf.org/license-info).
Please review these documents carefully, as they describe your rights
and restrictions with respect to this document.
Busi et al. Expires April 26, 2010 [Page 1]
Internet-Draft MPLS-TP OAM Framework October 2009
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].
Table of Contents
1. Introduction.....................................................3
1.1. Contributing Authors........................................4
2. Conventions used in this document................................4
2.1. Terminology.................................................4
2.2. Definitions.................................................5
3. Functional Components............................................8
3.1. Maintenance Entity (ME) and Maintenance Entity Group (MEG)..9
3.2. MEG End Points (MEPs)......................................12
3.3. MEG Intermediate Points (MIPs).............................14
3.4. Server MEPs................................................15
3.5. Tandem Connection..........................................15
4. Reference Model.................................................16
4.1. MPLS-TP Section Monitoring.................................19
4.2. MPLS-TP LSP End-to-End Monitoring..........................20
4.3. MPLS-TP LSP Tandem Connection Monitoring...................21
4.4. MPLS-TP PW Monitoring......................................23
4.5. MPLS-TP MS-PW Tandem Connection Monitoring.................23
5. OAM Functions for proactive monitoring..........................24
5.1. Continuity Check and Connectivity Verification.............25
5.1.1. Defects identified by CC-V............................26
5.1.2. Consequent action.....................................28
5.1.3. Configuration considerations..........................29
5.1.4. Applications for proactive CC-V.......................29
5.2. Remote Defect Indication...................................30
5.2.1. Configuration considerations..........................31
5.2.2. Applications for Remote Defect Indication.............31
5.3. Alarm Reporting............................................31
5.4. Lock Reporting.............................................33
5.5. Packet Loss Monitoring.....................................33
5.5.1. Configuration considerations..........................33
5.5.2. Applications for Packet Loss Monitoring...............33
Busi et al. Expires April 26, 2010 [Page 2]
Internet-Draft MPLS-TP OAM Framework October 2009
5.6. Client Signal Failure Indication...........................34
5.6.1. Configuration considerations..........................34
5.6.2. Applications for Client Signal Failure Indication.....34
5.7. Delay Measurement..........................................35
5.7.1. Configuration considerations..........................35
5.7.2. Applications for Delay Measurement....................36
6. OAM Functions for on-demand monitoring..........................36
6.1. Connectivity Verification..................................36
6.1.1. Configuration considerations..........................38
6.2. Packet Loss Monitoring.....................................38
6.2.1. Configuration considerations..........................38
6.2.2. Applications for On-demand Packet Loss Monitoring.....39
6.3. Diagnostic.................................................39
6.4. Route Tracing..............................................39
6.5. Delay Measurement..........................................40
6.5.1. Configuration considerations..........................40
6.5.2. Applications for Delay Measurement....................41
6.6. Lock Instruct..............................................41
7. Security Considerations.........................................41
8. IANA Considerations.............................................41
9. Acknowledgments.................................................41
10. References.....................................................43
10.1. Normative References......................................43
10.2. Informative References....................................43
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.
[Editor's note - The draft needs to be reviewed to ensure support of
OAM for p2mp transport paths]
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]).
Busi et al. Expires April 26, 2010 [Page 3]
Internet-Draft MPLS-TP OAM Framework October 2009
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
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
LTCME LSP Tandem Connection Maintenance Entity
[Editor's note - Difference or similarity between tandem connection
monitoring (TCM)_and Path Segment Tunnel (PST) need to be defined and
agreed]
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
Busi et al. Expires April 26, 2010 [Page 4]
Internet-Draft MPLS-TP OAM Framework October 2009
PTCME PW Tandem Connection Maintenance Entity
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.
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.
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).
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
Busi et al. Expires April 26, 2010 [Page 5]
Internet-Draft MPLS-TP OAM Framework October 2009
messages. It never generates unsolicited OAM messages itself. A MIP
resides within an MEG between MEPs (details in section 3.2).
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 Message: One or more OAM information elements that when
exchanged between MEPs or between MEPs and MIPs performs some OAM
functionality (e.g. continuity check or 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) independently from 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.
The following terms are defined in RFC 5654 [11] as follows:
Associated bidirectional path: A path that supports traffic flow in
both directions but that is constructed from a pair of unidirectional
paths (one for each direction) that are associated with one another
at the path's ingress/egress points. The forward and backward
directions are setup, monitored, and protected independently. As a
consequence, they may or may not follow the same route (links and
nodes) across the network.
Concatenated Segment: A serial-compound link connection as defined in
G.805 [17]. A concatenated segment is a contiguous part of an LSP or
Busi et al. Expires April 26, 2010 [Page 6]
Internet-Draft MPLS-TP OAM Framework October 2009
multi-segment PW that comprises a set of segments and their
interconnecting nodes in sequence. See also "Segment".
Co-routed bidirectional path: A path where the forward and backward
directions follow the same route (links and nodes) across the
network. Both directions are setup, monitored and protected as a
single entity. A transport network path is typically co-routed.
Layer network: Layer network is defined in G.805 [17]. A layer
network provides for the transfer of client information and
independent operation of the client OAM. A layer network may be
described in a service context as follows: one layer network may
provide a (transport) service to higher client layer network and may,
in turn, be a client to a lower-layer network. A layer network is a
logical construction somewhat independent of arrangement or
composition of physical network elements. A particular physical
network element may topologically belong to more than one layer
network, depending on the actions it takes on the encapsulation
associated with the logical layers (e.g., the label stack), and thus
could be modeled as multiple logical elements. A layer network may
consist of one or more sublayers. Section 1.4 (of RFC 5654) provides
a more detailed overview of what constitutes a layer network. For
additional explanation of how layer networks relate to the OSI
concept of layering, see Appendix I of Y.2611 [19].
Section Layer Network: A section layer is a server layer (which may
be MPLS-TP or a different technology) that provides for the transfer
of the section-layer client information between adjacent nodes in the
transport-path layer or transport service layer. A section layer may
provide for aggregation of multiple MPLS-TP clients. Note that G.805
[17] defines the section layer as one of the two layer networks in a
transmission-media layer network. The other layer network is the
physical-media layer network.
Path: See Transport Path
Segment: A link connection as defined in G.805 [17]. A segment is the
part of an LSP that traverses a single link or the part of a PW that
traverses a single link (i.e., that connects a pair of adjacent
{Switching|Terminating} Provider Edges). See also "Concatenated
Segment". [editors: concept should be layer specific.. suggesting
that the part of a PW that traverses a single physical link is a
segment means a segment is pretty much bounded by duct ends, and by
devices completely clueless as to the existence of the PW, visibility
of the wrong layer, To group: we have a definition conflict between
G.805 and usage of segment in IETF (e.g. PWE3), not sure how to
resolve this, for discussion Nov 3]
Busi et al. Expires April 26, 2010 [Page 7]
Internet-Draft MPLS-TP OAM Framework October 2009
Sublayer: Sublayer is defined in G.805 [17]. The distinction between
a layer network and a sublayer is that a sublayer is not directly
accessible to clients outside of its encapsulating layer network and
offers no direct transport service for a higher layer (client)
network. [editors: messy definition as it is context specific. Given
MPLS has no PID, the transport path will always exist in a sublayer
as the PW or PID label which has no forwarding context will be bottom
of stack. Whether or not you actually think of the PW label as being
a sublayer itself entirely dependant on usage SS or MS-PW, for
discussion Nov 3rd]
Transport Path: A network connection as defined in G.805 [17]. In an
MPLS-TP environment, a transport path corresponds to an LSP or a PW.
Transport Path Layer: A (sub)layer network that provides
point-to-point or point-to-multipoint transport paths. It is
instrumented with OAM mechanisms that are independent of the clients
it is transporting. [editor: if you look at the sublayer discussion
above, this term pretty much universally must be a transport path
sub-layer. The transport path cannot be a layer to itself in the
MPLS_TP architecture unless we are discussing multi-segment dry
martini, for discussion Nov 3rd]
Unidirectional path: A path that supports traffic flow in only one
direction.
The term 'Per-hop Behavior' is defined in [14] as follows:
Per-hop Behavior: a description of the externally observable
forwarding treatment applied at a differentiated services-compliant
node to a behavior aggregate.
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 -
Busi et al. Expires April 26, 2010 [Page 8]
Internet-Draft MPLS-TP OAM Framework October 2009
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, for
discussion Nov 3rd]
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 is
created by either the management plane or by the control plane (if
present). Some components may be instantiated after the path is
initially created (e.g. TCM).
3.1. Maintenance Entity (ME) and Maintenance Entity Group (MEG)
[editors: rather than fight chicken and egg, we made two sections
into one]
MPLS-TP OAM operates in the context of Maintenance Entities (MEs)
that are a relationship between two points of a point to point
[editors: why has this restriction been added, for discussion Nov 3rd]
transport path to which maintenance and monitoring operations
apply. These two points are called Maintenance Entity Group End
Points (MEPs). In between these two points zero or more intermediate
points, called Maintenance Entity Group MEG 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 the MEPs belong to (i.e. within
the domain of the transport path or segment, in the specific 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
Busi et al. Expires April 26, 2010 [Page 9]
Internet-Draft MPLS-TP OAM Framework October 2009
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 or
lower layer TCMs.
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 network under its
responsibility and to localize problems efficiently.
[Dave: given how these definitions are shaking out, should the MEG
and ME not be confined to a sub-layer, there is no such thing as a
completely self contained "layer" in the architecture to which a MEG
can apply, for Nov 3rd]
An MPLS-TP maintenance entity group can cover either the whole end-
to-end or a Tandem Connection of the transport path. A Maintenance
Entity Group may be defined to monitor the transport path for fault
and/or performance management.
In case of associated bi-directional paths, two independent
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 exist
in a unidirectional ME.
The following properties apply to all MPLS-TP MEs:
o They can be nested but not overlapped, e.g. an ME may cover a
segment or a concatenated segment of another ME, and may also
include the forwarding engine(s) of the node(s) at the edge(s) of
the segment or concatenated segment, but all its MEPs and MIPs are
no longer part of the encompassing ME. It is possible that MEPs of
nested MEs reside on a single node.
o Each OAM flow is associated with a single Maintenance Entity.
o OAM packets are subject to the same forwarding treatment (i.e.
fate share) as the data traffic and in some cases may be required
to have common queuing discipline E2E with the class of traffic
monitored. OAM packets can be distinguished from the data traffic
using the GAL and ACH constructs [9] for LSP and Section or the
ACH construct [6]and [9] for (MS-)PW.
Busi et al. Expires April 26, 2010 [Page 10]
Internet-Draft MPLS-TP OAM Framework October 2009
[Propose from Munich - rewrite to describe the MEG as collection of
one or more maint entities and then immediately define an ME.
[editors: much of this comment is actually either ME or MEP/MIP
specific, not MEG specific, hence we are struggling as to what to do
with this, for discussion Nov 3rd]
A key point in the definition of an ME is the end-points are defined
by location of the logical function MEP
Later 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 to distinguish between the point of interception of an OAM
msg and the point where the action takes place.
Somewhere we need to distinguish between the OAM control function and
the OAM measurement function. i.e. we set up a loop back (a control
function, in which case the OAM message may be intercepted and
actioned anywhere convenient), and the measurement function (i.e.
looping the packet to determine that it reached a particular part of
the network) which needs to be actioned at a precisely know and
stipulated point in the network/equipment.
Note that not all functionality / processing of an OAM pkt needs to
take place at the point of measurement.
We considered 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 the
node - i.e. egress interface
- Response via OAM
- Reporting to mgt interface
It is useful to further decompose this into an initiator and a
responder in general an initiator is the source mep and the responder
is a mip or a sink mep. There are exceptions to this such as a mip
initiating an AIS msg or lock indication.]
Busi et al. Expires April 26, 2010 [Page 11]
Internet-Draft MPLS-TP OAM Framework October 2009
Another OAM construct is referred to as Maintenance Entity Group,
which is a collection of one or more MEs that belongs to the same
transport path and that are maintained and monitored as a group.
A use case for an MEG with more than one ME is point-to-multipoint
OAM. The reference model for the 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 OAM operations are independent
for each ME (A-D, A-E and A-F):
o Fault conditions - depending from where the failure is located
o Packet loss - depending from where the packets are lost
o Packet delay - depending on different paths
Each leaf (i.e. D, E and F) terminates OAM messages to monitor its
own [Root, Leaf] ME while the root (i.e. A) generates OAM messages to
monitor all the MEs of the p2mp MEG. In this particular case, the
p2mp transport path is monitored by a MEG that consists of three MEs.
Nodes B and C might implement a MIP in the corresponding MEGs.
3.2. MEG End Points (MEPs)
MEG End Points (MEPs) are the end points of an MEG. In the context of
an MPLS-TP LSP, only LERs can implement MEPs while in the context of
an LSP Tandem Connection both LERs and LSRs can implement MEPs.
Regarding MPLS-TP PW, only T-PEs can implement MEPs while for a PW
Tandem Connection both T-PEs and S-PEs can implement MEPs. In the
context of MPLS-TP Section, any MPLS-TP NE can implement MEPs.
[Munich: See note about PW Tandem monitoring earlier, and whether a
PW can be a tandem connection]
Busi et al. Expires April 26, 2010 [Page 12]
Internet-Draft MPLS-TP OAM Framework October 2009
MEPs are responsible for activating and controlling all of the OAM
functionality for the MEG. A MEP is capable of initiating 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 MPLS label identifies the MEG the OAM packet
belongs to.
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 support a MEP.
MEPs have to prevent OAM packets corresponding to a MEG from leaking
outside that MEG:
o A MEP sink terminates all the OAM packets that it receives
corresponding to its MEG and does not forward them further along
the path.
o A MEP in a tandem connection tunnels all the OAM packets that it
receives, upstream from the associated MEG to prevent them from
being processed within the associated MEG. The usage of the label
stacking mechanism allows all the MEPs and MIPs within the MEG to
distinguish tunneled OAM packets from OAM packets that belong to
that MEG.
MPLS-TP MEP passes a fault indication to its client (sub-)layer
network as a consequent action of fault detection. [ editor:
interesting case, is this always sink, or are we considering
loopbacks where inserting fault indication into the client (s)layer
is comparatively useless. We wrestled with same problem with RSVP
errors in the past ..., for Nov 3rd]
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.
A MEP of an MPLS-TP tandem connection is not necessarily coincident
with the termination of the MPLS-TP transport path (LSP or PW) and
monitors the transport path for failures or performance degradation
(e.g. based on packet counts) within the boundary of the MEG for the
tandem connection.
Busi et al. Expires April 26, 2010 [Page 13]
Internet-Draft MPLS-TP OAM Framework October 2009
It may occur in TCM that two MEPs 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 i.e. an LSP or PW. If we need to add a monitoring point within
an LSP we create a new sub-layer. We need to describe the migration
process for adding a TCM segment.
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: clarify in section 3.4]
3.3. MEG Intermediate Points (MIPs)
A MEG Intermediate Point (MIP) is a point between the two MEPs of an
ME.
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 OAM - editors:
this text was removed in the commented .rtf document from Munich but
not tracked as a revision, validate this change Nov 3rd] packets, but
may be addressed by OAM packets initiated by one of the MEPs of the
ME. 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 an 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 MIPs per node on both sides of
the forwarding engine)
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" 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 belongs to is inferred from
the MPLS label.
Busi et al. Expires April 26, 2010 [Page 14]
Internet-Draft MPLS-TP OAM Framework October 2009
Once an MEG is configured, the operator can enable/disable the MIPs
on the nodes within the MEG.
3.4. Server MEPs
A server MEP is a MEP of an ME that is either:
o defined in a layer network below the MPLS-TP layer network being
referenced, or
o defined in a sub-layer of the MPLS-TP layer network that is below
the sub-layer being referenced.
A server MEP can coincide with a MIP or a MEP in the client (MPLS-TP)
layer network.
A server MEP also interacts with the client/server adaptation
function between the client (MPLS-TP) layer network and the server
layer network. The adaptation function maintaints state on the
mapping of MPLS-TP transport paths that are setup over that server
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
OTH 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 LSP Tandem Connection MEP for higher-level LTCMEs,
defined in section 4.3;
o An MPLS-TP PW Tandem Connection MEP for higher-level PTCMEs,
defined in section 4.5.
The server MEP can run appropriate OAM functions for fault detection
within the server (sub-)layer network, and notifies a fault
indication to its client MPLS-TP layer network. Server MEP OAM
functions are outside the scope of this document.
3.5. Tandem Connection
A tandem connection is instantiated to support tandem connection
monitoring (TCM).
Busi et al. Expires April 26, 2010 [Page 15]
Internet-Draft MPLS-TP OAM Framework October 2009
TCM for a given portion of a transport path is implemented by first
creating a hierarchical LSP that that has a 1:1 association with
portion of the transport path that is to be uniquely monitored such
that there is direct correlation between all FM and PM information
gathered for the tandem connection AND the monitored portion of the
E2E path. The tandem connection is monitored using normal LSP
monitoring. There are a number of implications to this approach:
1) The hierarchical LSP would use the uniform model of EXP code
point copying between sub-layers for diffserv such that the E2E
markings and PHB treatment was preserved in the tandem
connection.
2) The hierarchical LSP would use the pipe model for TTL handling
such that MIP addressing for the E2E entity would be distinct
from the tandem connection.
3) PM statistics need to be adjusted for the overhead of the
additional sub-layer.
4) The server sub-layer LSP is viewed as single hop by the client
LSP. The E2E ME source MEPs cannot direct transactions to tandem
connection MIPs.
[editors: the text from Munich suggested that a tandem connection
could be N:1, we've stuck with 1:1 such that there would be direct
correlation of PM stats between the tandem connection and the
monitored portion of the transport path, a N:1 hierarchical LSP IF WE
INSIST on including, should be documented as a separate procedure]
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 MEs are specified in this document:
o A Section Maintenance Entity (SME), allowing monitoring and
management of MPLS-TP Sections (between MPLS LSRs).
o A LSP Maintenance Entity (LME), allowing monitoring and management
of an end-to-end LSP (between LERs).
o A PW Maintenance Entity (PME), allowing monitoring and management
of an end-to-end SS/MS-PWs (between T-PEs).
Busi et al. Expires April 26, 2010 [Page 16]
Internet-Draft MPLS-TP OAM Framework October 2009
o An LSP Tandem Connection Maintenance Entity (LTCME), allowing
monitoring and management of an LSP Tandem Connection between any
LER/LSR along the LSP. [Munich: Please clarify that an LTCME is
JUST an ordinary hierarchical LSP (RFC3031).
Note - TCM only makes sense for LSPs as previously noted.]The MEs
specified in this MPLS-TP framework are compliant with the
architecture framework for MPLS MS-PWs [7] and MPLS LSPs [2].
Hierarchical LSPs are also supported. 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, end-to-end (from LER to LER) by an LME. Tandem
Connection monitoring via LTCME are applicable on each LSP Tunnel in
the hierarchy.
[Munich: There was discussion on above para - and it was suggested
that it be removed.] [ for discussion Nov 3rd, TCM and hierarchical
LSPs...]
Busi et al. Expires April 26, 2010 [Page 17]
Internet-Draft MPLS-TP OAM Framework October 2009
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 PTCME ---^ ^---- PWXZ PTCME ---^
^---------^ ^---------^
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.
Busi et al. Expires April 26, 2010 [Page 18]
Internet-Draft MPLS-TP OAM Framework October 2009
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. Yet, this does not preclude that multiple MEGs may be affected
simultaneously by the same network condition, for example, a fibre
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 PTCME because typically TCMs are
used to monitor an OAM domain (like PW13 and PWXZ PTCMEs) rather
than the segment between two OAM domains. However the OAM framework
does not pose any constraints on the way TCM are instantiated as long
as they are not overlapping.
The subsections below define the MEs specified in this MPLS-TP OAM
architecture framework document. Unless otherwise stated, all
references to domains, LSRs, MPLS Sections, LSPs, pseudowires and MEs
in this section are made in relation to those shown in Figure 3.
4.1. MPLS-TP Section Monitoring
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.
Busi et al. Expires April 26, 2010 [Page 19]
Internet-Draft MPLS-TP OAM Framework October 2009
|<------------------- 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 shows 5 Section MEs configured in the path 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
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.
Busi et al. Expires April 26, 2010 [Page 20]
Internet-Draft MPLS-TP OAM Framework October 2009
|<------------------- 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 depicts 2 LMEs configured in the path 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 Tandem Connection Monitoring
An MPLS-TP LSP Tandem Connection Monitoring ME (LTCME) 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 LTCME 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 LTCMEs MAY be configured on any LSP. The LSRs that terminate
the LTCME may or may not be immediately adjacent at the MPLS-TP
layer. LTCME OAM packets must fate share with the user data packets
sent over the monitored LSP segment.
A LTCME 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 LTCME is intended to be deployed in scenarios where it is
preferable to monitor the behaviour of a part of an LSP rather than
the entire LSP itself, for example when there is a need to monitor a
Busi et al. Expires April 26, 2010 [Page 21]
Internet-Draft MPLS-TP OAM Framework October 2009
part of an LSP that extends beyond the administrative boundaries of
an MPLS-TP enabled administrative domain.
Note that LTCMEs are equally applicable to hierarchical LSPs.
|<--------------------- 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 LTCME PSNXZ LTCME
^---------------------------------------^
PSN1Z LME
DBN: Domain Border Node
Figure 6 MPLS-TP LSP Tandem Connection Monitoring ME (LTCME)
Figure 6 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
configured to monitor the PSN1Z LSP: 1) a LTCME monitoring the PSN13
LSP Concatenated Segment on Domain 1 (PSN13 LTCME), and 2) a LTCME
monitoring the PSNXZ LSP Concatenated Segment on Domain Z (PSNXZ
LTCME).
It is worth noticing that LTCMEs can coexist with the LME monitoring
the end-to-end LSP and that LTCME MEPs and LME MEPs can be coincident
in the same node (e.g. PE1 node supports both the PSN1Z LME MEP and
the PSN13 LTCME MEP).
Busi et al. Expires April 26, 2010 [Page 22]
Internet-Draft MPLS-TP OAM Framework October 2009
4.4. MPLS-TP PW Monitoring
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 MPLS-TP PW ME (PME)
Figure 7 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 Tandem Connection Monitoring
An MPLS-TP MS-PW Tandem Connection Monitoring ME (PTCME) 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 PTCME 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 PTCMEs MAY be configured on any MS-PW. The PEs may or may
not be immediately adjacent at the MS-PW layer. PTCME OAM packets
fate share with the user data packets sent over the monitored PW
Segment.
A PTCME can be defined between the following entities:
o T-PE and any S-PE of a given MS-PW
Busi et al. Expires April 26, 2010 [Page 23]
Internet-Draft MPLS-TP OAM Framework October 2009
o Any two S-PEs of a given MS-PW. It can span several PW segments.
A PTCME 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 PTCME ----^ ^---- PW5 PTCME ----^
^---------------------PW1Z PME--------------------^
Figure 8 MPLS-TP MS-PW Tandem Connection Monitoring (PTCME)
Figure 8 depicts the same MS-PW (MS-PW1Z) between AC1 and AC2 as in
Figure 7. In this scenario there are two separate PTCMEs configured
to monitor MS-PW1Z: 1) a PTCME monitoring the PW13 MS-PW Segment on
Domain 1 (PW13 PTCME), and 2) a PTCME monitoring the PWXZ MS-PW
Segment on Domain Z with (PWXZ PTCME).
It is worth noticing that PTCMEs can coexist with the PME monitoring
the end-to-end MS-PW and that PTCME MEPs and PME MEPs can be
coincident in the same node (e.g. TPE1 node supports both the PW1Z
PME MEP and the PW13 PTCME MEP).
5. OAM Functions for proactive monitoring
[Munich: Note the fwk needs to be explicit about the mapping of
functions to the tools we have chosen.] [editors: shouldn't it be the
other way around?]
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.
Busi et al. Expires April 26, 2010 [Page 24]
Internet-Draft MPLS-TP OAM Framework October 2009
5.1. Continuity Check and Connectivity Verification
Proactive Continuity Check functions are used to detect a loss of
continuity defect (LOC) between two MEPs in an MEG.
Proactive Connectivity Verification functions 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 MEG identifier.
Different formats of MEP identifiers are defined in [10] to address
different applications. When MPLS-TP is deployed in transport network
applications as defined by ITU-T, the ICC-based format for MEP
identification is the DEFAULT and MANDATORY identification scheme.
When MPLS-TP is deployed in IP-based environment, the IP-based MEP
identification is the DEFAULT and MANDATORY identification scheme.
As a consequence, it is not possible to detect misconnections between
two MEGs monitored only for Continuity while it is possible to detect
any misconnection between two MEGs monitored for Continuity and
Connectivity or between an MEG monitored for Continuity and
Connectivity and one MEG monitored only for Continuity.
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).
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.
[Editor's note - Describe the relation between the previous paragraph
and the fate sharing requirement. Need to clarify also in the
requirement document that for proactive CC-V the fate sharing is
related to the forwarding behavior and not to the QoS behavior]
Busi et al. Expires April 26, 2010 [Page 25]
Internet-Draft MPLS-TP OAM Framework October 2009
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. 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.
To initialize the proactive CC-V monitoring on a configured ME
without affecting traffic, 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 ME and peer MEP identifiers) are
received within the interval equal to 3.5 times the receiving
MEP's configured CC-V transmission period.
o Exit criteria: a pro-active CC-V OAM packet from the peer MEP
(i.e. with the correct ME and peer MEP identifiers) 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 or misconnection) with its
Busi et al. Expires April 26, 2010 [Page 26]
Internet-Draft MPLS-TP OAM Framework October 2009
peer source MEP when the received packet carries an incorrect ME
identifier.
o Entry criteria: the sink MEP receives a pro-active CC-V OAM packet
with an incorrect ME ID.
o Exit criteria: the sink MEP does not receive any pro-active CC-V
OAM packet with an incorrect ME ID 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 ME ID 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 MEs.
5.1.1.3. MEP misconfiguration defect
When a pro-active CC-V packet is received, a sink MEP identifies a
MEP misconfiguration defect with its peer source MEP when the
received packet carries a correct ME Identifier but an unexpected
peer MEP Identifier which includes the MEP's own MEP Identifier.
o Entry criteria: the sink MEP receives a CC-V pro-active packet
with correct ME ID but with unexpected MEP ID.
o Exit criteria: the sink MEP does not receive any pro-active CC-V
OAM packet with a correct ME ID and unexpected MEP ID 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
ME ID and unexpected MEP ID since this defect has been raised.
5.1.1.4. Period Misconfiguration defect
If pro-active CC-V OAM packets are received with correct ME and MEP
identifiers but with a transmission period different than its own
configured transmission period, then a CC-V period mis-configuration
defect is detected
o Entry criteria: a MEP receives a CC-V pro-active packet with
correct ME ID and MEP ID 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 ME and MEP IDs 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 ME and MEP IDs and an incorrect
transmission period since this defect has been raised.
Busi et al. Expires April 26, 2010 [Page 27]
Internet-Draft MPLS-TP OAM Framework October 2009
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 ME Identifier, or an unexpected MEP,
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 and the CC-V monitoring is enabled 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 ME in
order to reliably detect connectivity defects. However, CC-V
proactive monitoring MAY be disabled by an operator on an ME. 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, an unexpected ME Identifier, or an
unexpected MEP it MUST declare a signal fail condition at the
transport path level.
If a MEP detects an Unexpected Period defect it SHOULD 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
Busi et al. Expires April 26, 2010 [Page 28]
Internet-Draft MPLS-TP OAM Framework October 2009
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 ME. 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)
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 the above information are
statically configured; for dynamically established transport paths
the configuration information are signaled via the control plane.
5.1.4. Applications for proactive CC-V
CC-V is applicable for fault management, performance monitoring, or
protection switching applications.
o Fault Management: default transmission period is 1s (i.e.
transmission rate of 1 packet/second)
o Performance Monitoring: 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.
Busi et al. Expires April 26, 2010 [Page 29]
Internet-Draft MPLS-TP OAM Framework October 2009
o Protection Switching: in order to achieve sub-50ms the defect
entry criteria should resolve in less than 50msec, and should
budget sufficient portion of the 50 msec. to be available for
consequent action processing. In some cases, when a slower
recovery time is acceptable, it is also possible to lengthen the
transmission rate.
It SHOULD be possible for the operator to configure these
transmission rates for all applications, to satisfy his internal
requirements.
In addition, the operator should be able to define the consequent
action to be performed for each of these applications.
5.2. Remote Defect Indication
The Remote Defect Indication (RDI) 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.]
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.
Busi et al. Expires April 26, 2010 [Page 30]
Internet-Draft MPLS-TP OAM Framework October 2009
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 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, 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
MEP upon fault detection in the server layer network to which the
server MEP is associated.
[editor: the above is confused. The server layer passes signal fail
or whatever notification to the adaptation function which has
knowledge of the client layer transport paths, otherwise we are
discussing a layer violation. These may be MEP co-located end points
or MIPs. It is the OAM functionality co-located with the adaptation
function that performs AIS insertion into the client layer MPLS-TP
paths.... If agreed I will re-word accordingly]
Only Server MEPs can issue MPLS-TP packets with AIS information. Upon
detection of a signal fail condition the Server MEP can immediately
start transmitting periodic packets with AIS information. These
Busi et al. Expires April 26, 2010 [Page 31]
Internet-Draft MPLS-TP OAM Framework October 2009
periodic packets, with AIS information, continue to be transmitted
until the signal fail condition is cleared. [editor: SEE ABOVE]
Upon receiving a packet with AIS information an MPLS-TP MEP detects
an AIS defect condition and suppresses loss of continuity alarms
associated with all of its peer MEPs. [editor: There can only be one
MEP for the ME AIS has been received in association with] 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 MEs
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 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 generates AIS packets on
the PSN13 LME in order to allow its MEP in LSR3 to suppress the LOC
alarm. LSR3 can also suppress the secondary alarm on PW1 PTCME
because the MEP of PW1 PTCME resides within the same node as the MEP
of PSN13 LME. The MEP of PW1 PTCME in LSR3 also 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 ME 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.
Busi et al. Expires April 26, 2010 [Page 32]
Internet-Draft MPLS-TP OAM Framework October 2009
5.4. Lock Reporting
To be incorporated in a future revision of this document
5.5. Packet Loss Monitoring
Packet Loss Monitoring (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. 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 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).
5.5.2. Applications for Packet Loss Monitoring
LM is relevant for the following applications:
o Single or double-end performance monitoring: determination of the
packet loss performance of a transport path for Service Level
Agreement (SLA) verification purposes.
Busi et al. Expires April 26, 2010 [Page 33]
Internet-Draft MPLS-TP OAM Framework October 2009
o Single or double-end performance monitoring: determination of 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, in a manner similar to
Recommendation G.826 [19] and Recommendation G.7710 [20].
5.6. Client Signal Failure Indication
The Client Signal Failure Indication (CSF) function 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 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 path does not support a native
defect/alarm indication mechanism, e.g. FDI/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 ME, 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:
Busi et al. Expires April 26, 2010 [Page 34]
Internet-Draft MPLS-TP OAM Framework October 2009
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. Delay Measurement
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. 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
Busi et al. Expires April 26, 2010 [Page 35]
Internet-Draft MPLS-TP OAM Framework October 2009
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
[Munich: Note the fwk needs to be explicit about the mapping of
functions to the tools we have chosen.]
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.
[editor: we would have to babysit a lot fewer words if we folded this
into section 5 and simply indicated which transactions existed in
both proactive and reactive forms... if agreed I will edit accordingly]
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.
Use of on-demand CV is dependent on the existence of a bi-directional
connection ME, because it requires the presence of a return path in
the data plane.
[Editor's note - Clarify in the sentence above and within the
paragraph that on-demand CV requires a return path to send back the
reply to on-demand CV packets]
Busi et al. Expires April 26, 2010 [Page 36]
Internet-Draft MPLS-TP OAM Framework October 2009
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 ME that is being checked. The on-demand
functionality may be used to check either an entire ME (end-to-end)
or between a MEP to a specific MIP. This functionality may not be
available for associated bidirectional 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 ME, the source MEP should issue
a burst of on-demand CV packets that uniquely identifies the ME 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 and use the default
value when performing an end-to-end check [IB => This is quite
generic for addressing packets to MIPs and MEPs so it is better to
move this text in section 2]. 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 the usage of on-demand
CV with different packet sizes, e.g. to discover MTU problems.]
When a connectivity problem is detected (e.g. via a proactive CC-V
OAM tool), an on-demand CV tool can be used to check the path. The
series should check CV from MEP to peer MEP on the path, and if a
fault is discovered, by lack of response, then additional checks may
be performed to each of the intermediate MIP to locate the fault.
[Dave: this seems a bit warped as the original discussion was about
not spending resources on proactive CC-V, so can we just be honest
about "when the incredibly pissed off customer calls, an on demand CV
tool..."]
Busi et al. Expires April 26, 2010 [Page 37]
Internet-Draft MPLS-TP OAM Framework October 2009
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 the reason for such
configuration]
6.2. Packet Loss Monitoring
On-demand Packet Loss (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. 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. [Dave: again
are we discussing simply discard eligibility and no other PHB
impacts?]
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).
Busi et al. Expires April 26, 2010 [Page 38]
Internet-Draft MPLS-TP OAM Framework October 2009
6.2.2. Applications for On-demand Packet Loss Monitoring
On-demand LM is relevant for the following applications:
o Single-end performance monitoring: diagnostic of the packet loss
performance of a transport path for SLA trouble shooting purposes.
o Single-end performance monitoring: diagnostic of the packet loss
performance of a PHB Scheduling Class or Ordering Aggregate within
a transport path for QoS trouble shooting purposes.
6.3. Diagnostic
To be incorporated in a future revision of this document
[Munich: Need to describe the two types of loopback - LBM/LBR and
traffic loopback enhanced with variable sized packets in the on
demand cases.
One objective of diags is fault location, we need to make clear how
we apply the tools to fault location.
At the top of each section we need to describe the detailed
requirements and then in the rest of the section describe how it is
met.]
6.4. Route Tracing
After e.g. provisioning an MPLS-TP LSP or for trouble shooting
purposes, it is often necessary to trace a route covered by an ME
from a source MEP to the sink MEP including all the MIPs in-between.
The route tracing function 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 and, to a much lesser degree, CC. 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 the full list of MIPs and
the peer MEP in it answer(s). 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.
Busi et al. Expires April 26, 2010 [Page 39]
Internet-Draft MPLS-TP OAM Framework October 2009
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. Delay Measurement
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. 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 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.
Busi et al. Expires April 26, 2010 [Page 40]
Internet-Draft MPLS-TP OAM Framework October 2009
6.5.2. Applications for Delay Measurement
DM is relevant for the following applications:
o Single or double-end performance monitoring: determination of the
packet delay and/or delay variation performance of a transport
path for SLA verification purposes.
o Single or double-end performance monitoring: determination of the
packet delay and/or delay variation a PHB Scheduling Class or
Ordering Aggregate within a 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 to unavailable
time.
6.6. Lock Instruct
To be incorporated in a future revision of this document
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
Busi et al. Expires April 26, 2010 [Page 41]
Internet-Draft MPLS-TP OAM Framework October 2009
T-MPLS Ad Hoc Group in ITU-T) involved in the definition and
specification of MPLS Transport Profile.
This document was prepared using 2-Word-v2.0.template.dot.
Busi et al. Expires April 26, 2010 [Page 42]
Internet-Draft MPLS-TP OAM Framework October 2009
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-01 (work in progress),
June 2009
[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-swallow-
mpls-tp-identifiers-01 (work in progress), July 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 (work in progress), August 2009
Busi et al. Expires April 26, 2010 [Page 43]
Internet-Draft MPLS-TP OAM Framework October 2009
[13] Sprecher, N., Nadeau, T., van Helvoort, H., Weingarten, Y.,
"MPLS-TP OAM Analysis", draft-sprecher-mpls-tp-oam-analysis-04
(work in progress), May 2009
[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.it
Busi et al. Expires April 26, 2010 [Page 44]
Internet-Draft MPLS-TP OAM Framework October 2009
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@alcatel-lucent.com
Lieven Levrau
Alcatel-Lucent
Email: llevrau@alcatel-lucent.com
Dinesh Mohan
Nortel
Email: mohand@nortel.com
Vincenzo Sestito
Alcatel-Lucent
Email: vincenzo.sestito@alcatel-lucent.it
Nurit Sprecher
Nokia Siemens Networks
Email: nurit.sprecher@nsn.com
Busi et al. Expires April 26, 2010 [Page 45]
Internet-Draft MPLS-TP OAM Framework October 2009
Huub van Helvoort
Huawei Technologies
Email: hhelvoort@huawei.com
Martin Vigoureux
Alcatel-Lucent
Email: martin.vigoureux@alcatel-lucent.fr
Yaacov Weingarten
Nokia Siemens Networks
Email: yaacov.weingarten@nsn.com
Rolf Winter
NEC
Email: Rolf.Winter@nw.neclab.eu
Busi et al. Expires April 26, 2010 [Page 46]
| PAFTECH AB 2003-2026 | 2026-04-22 17:12:55 |