Internet Engineering Task Force (IETF) K. Lam
Request for Comments: 5951 Alcatel-Lucent
Category: Standards Track S. Mansfield
ISSN: 2070-1721 E. Gray
September 2010 Network Management Requirements for MPLS-based Transport Networks
This document specifies the requirements for the management of
equipment used in networks supporting an MPLS Transport Profile
(MPLS-TP). The requirements are defined for specification of
network management aspects of protocol mechanisms and procedures
that constitute the building blocks out of which the MPLS
Transport Profile is constructed. That is, these requirements
indicate what management capabilities need to be available in
MPLS for use in managing the MPLS-TP. This document is intended
to identify essential network management capabilities, not to
specify what functions any particular MPLS implementation
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This document specifies the requirements for the management of
equipment used in networks supporting an MPLS Transport Profile
(MPLS-TP). The requirements are defined for specification of network
management aspects of protocol mechanisms and procedures that
constitute the building blocks out of which the MPLS Transport
Profile is constructed. That is, these requirements indicate what
management capabilities need to be available in MPLS for use in
managing the MPLS-TP. This document is intended to identify
essential network management capabilities, not to specify what
functions any particular MPLS implementation supports.
This document also leverages management requirements specified in
ITU-T G.7710/Y.1701  and RFC 4377 , and attempts to comply with
the guidelines defined in RFC 5706 .
ITU-T G.7710/Y.1701 defines generic management requirements for
transport networks. RFC 4377 specifies the operations and management
requirements, including operations-and-management-related network
management requirements, for MPLS networks.
This document is a product of a joint ITU-T and IETF effort to
include an MPLS Transport Profile (MPLS-TP) within the IETF MPLS and
Pseudowire Emulation Edge-to-Edge (PWE3) architectures to support
capabilities and functionality of a transport network as defined by
The requirements in this document derive from two sources:
1) MPLS and PWE3 architectures as defined by the IETF, and
2) packet transport networks as defined by the ITU-T.
Requirements for management of equipment in MPLS-TP networks are
defined herein. Related functions of MPLS and PWE3 are defined
elsewhere (and are out of scope in this document).
This document expands on the requirements in ITU-T G.7710/Y.1701 
and RFC 4377  to cover fault, configuration, performance, and
security management for MPLS-TP networks, and the requirements for
object and information models needed to manage MPLS-TP networks and
In writing this document, the authors assume the reader is familiar
with RFCs 5921  and 5950 .
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 .
Although this document is not a protocol specification, the use of
this language clarifies the instructions to protocol designers
producing solutions that satisfy the requirements set out in this
Anomaly: The smallest discrepancy that can be observed between actual
and desired characteristics of an item. The occurrence of a single
anomaly does not constitute an interruption in ability to perform a
required function. Anomalies are used as the input for the
Performance Monitoring (PM) process and for detection of defects
(from , Section 3.7).
Communication Channel (CCh): A logical channel between network
elements (NEs) that can be used (for example) for management or
control plane applications. The physical channel supporting the CCh
is technology specific. See Appendix A.
Data Communication Network (DCN): A network that supports Layer 1
(physical layer), Layer 2 (data-link layer), and Layer 3 (network
layer) functionality for distributed management communications
related to the management plane, for distributed signaling
communications related to the control plane, and other operations
communications (e.g., order-wire/voice communications, software
Defect: The density of anomalies has reached a level where the
ability to perform a required function has been interrupted. Defects
are used as input for performance monitoring, the control of
consequent actions, and the determination of fault cause (from ,
Failure: The fault cause persisted long enough to consider the
ability of an item to perform a required function to be terminated.
The item may be considered as failed; a fault has now been detected
(from , Section 3.25).
Fault: A fault is the inability of a function to perform a required
action. This does not include an inability due to preventive
maintenance, lack of external resources, or planned actions (from
, Section 3.26).
Fault Cause: A single disturbance or fault may lead to the detection
of multiple defects. A fault cause is the result of a correlation
process that is intended to identify the defect that is
representative of the disturbance or fault that is causing the
problem (from , Section 3.27).
Fault Cause Indication (FCI): An indication of a fault cause.
Management Communication Channel (MCC): A CCh dedicated for
management plane communications.
Management Communication Network (MCN): A DCN supporting management
plane communication is referred to as a Management Communication
MPLS-TP NE: A network element (NE) that supports the functions of
MPLS necessary to participate in an MPLS-TP based transport service.
See RFC 5645  for further information on functionality required to
MPLS-TP network: a network in which MPLS-TP NEs are deployed.
Operations, Administration and Maintenance (OAM), On-Demand and
Proactive: One feature of OAM that is largely a management issue is
control of OAM; on-demand and proactive are modes of OAM mechanism
operation defined in (for example) Y.1731 ( - Sections 3.45 and
3.44, respectively) as:
o On-demand OAM - OAM actions that are initiated via manual
intervention for a limited time to carry out diagnostics.
On-demand OAM can result in singular or periodic OAM actions
during the diagnostic time interval.
o Proactive OAM - OAM actions that are carried on continuously to
permit timely reporting of fault and/or performance status.
(Note that it is possible for specific OAM mechanisms to only have a
sensible use in either on-demand or proactive mode.)
Operations System (OS): A system that performs the functions that
support processing of information related to operations,
administration, maintenance, and provisioning (OAM&P) for the
networks, including surveillance and testing functions to support
customer access maintenance.
Signaling Communication Channel (SCC): A CCh dedicated for control
plane communications. The SCC can be used for GMPLS/ASON signaling
and/or other control plane messages (e.g., routing messages).
Signaling Communication Network (SCN): A DCN supporting control plane
communication is referred to as a Signaling Communication Network
2. Management Interface Requirements
This document does not specify a preferred management interface
protocol to be used as the standard protocol for managing MPLS-TP
networks. Managing an end-to-end connection across multiple operator
domains where one domain is managed (for example) via NETCONF  or
SNMP , and another domain via CORBA , is allowed.
1) For the management interface to the management system, an MPLS-TP
NE MAY actively support more than one management protocol in any
For example, an operator can use one protocol for configuration of an
MPLS-TP NE and another for monitoring. The protocols to be supported
are at the discretion of the operator.
3. Management Communication Channel (MCC) Requirements
1) Specifications SHOULD define support for management connectivity
with remote MPLS-TP domains and NEs, as well as with termination
points located in NEs under the control of a third party network
operator. See ITU-T G.8601  for example scenarios in multi-
carrier, multi-transport technology environments.
2) For management purposes, every MPLS-TP NE MUST connect to an OS.
The connection MAY be direct (e.g., via a software, hardware, or
proprietary protocol connection) or indirect (via another MPLS-TP
NE). In this document, any management connection that is not via
another MPLS-TP NE is a direct management connection. When an
MPLS-TP NE is connected indirectly to an OS, an MCC MUST be
supported between that MPLS-TP NE and any MPLS-TP NE(s) used to
provide the connection to an OS.
4. Management Communication Network (MCN) Requirements
Entities of the MPLS-TP management plane communicate via a DCN, or
more specifically via the MCN. The MCN connects management systems
with management systems, management systems with MPLS-TP NEs, and (in
the indirect connectivity case discussed in section 3) MPLS-TP NEs
with MPLS-TP NEs.
RFC 5586  defines a Generic Associated Channel (G-ACh) to enable
the realization of a communication channel (CCh) between adjacent
MPLS-TP NEs for management and control. RFC 5718  describes how
the G-ACh can be used to provide infrastructure that forms part of
the MCN and SCN. It also explains how MCN and SCN messages are
encapsulated, carried on the G-ACh, and decapsulated for delivery to
management or signaling/routing control plane components on a label
switching router (LSR).
Section 7 of ITU-T G.7712/Y.1703  describes the transport DCN
architecture and requirements as follows:
1) The MPLS-TP MCN MUST support the requirements for:
a) CCh access functions specified in Section 7.1.1;
b) MPLS-TP SCC data-link layer termination functions specified in
c) MPLS-TP MCC data-link layer termination functions specified in
d) Network layer PDU into CCh data-link frame encapsulation
functions specified in Section 7.1.3;
e) Network layer PDU forwarding (Section 7.1.6), interworking
(Section 7.1.7), and encapsulation (Section 7.1.8) functions,
as well as tunneling (Section 7.1.9) and routing (Section
As a practical matter, MCN connections will typically have addresses.
See the section on Identifiers in RFC 5921  for further
In order to have the MCN operate properly, a number of management
functions for the MCN are needed, including:
o Retrieval of DCN network parameters to ensure compatible
functioning, e.g., packet size, timeouts, quality of service,
window size, etc.;
o Establishment of message routing between DCN nodes;
o Management of DCN network addresses;
o Retrieval of operational status of the DCN at a given node;
o Capability to enable/disable access by an NE to the DCN. Note
that this is to allow the isolation of a malfunctioning NE to keep
it from impacting the rest of the network.
5. Fault Management Requirements
The Fault Management functions within an MPLS-TP NE enable the
supervision, detection, validation, isolation, correction, and
reporting of abnormal operation of the MPLS-TP network and its
5.1. Supervision Function
The supervision function analyzes the actual occurrence of a
disturbance or fault for the purpose of providing an appropriate
indication of performance and/or detected fault condition to
maintenance personnel and operations systems.
1) The MPLS-TP NE MUST support supervision of the OAM mechanisms that
are deployed for supporting the OAM requirements defined in RFC
2) The MPLS-TP NE MUST support the following data-plane forwarding
path supervision functions:
a) Supervision of loop-checking functions used to detect loops in
the data-plane forwarding path (which result in non-delivery of
traffic, wasting of forwarding resources, and unintended self-
replication of traffic);
b) Supervision of failure detection;
3) The MPLS-TP NE MUST support the capability to configure data-plane
forwarding path related supervision mechanisms to perform
on-demand or proactively.
4) The MPLS-TP NE MUST support supervision for software processing --
e.g., processing faults, storage capacity, version mismatch,
corrupted data, and out of memory problems, etc.
5) The MPLS-TP NE MUST support hardware-related supervision for
interchangeable and non-interchangeable unit, cable, and power
6) The MPLS-TP NE SHOULD support environment-related supervision for
temperature, humidity, etc.
5.2. Validation Function
Validation is the process of integrating Fault Cause indications into
Failures. A Fault Cause Indication (FCI) indicates a limited
interruption of the required transport function. A Fault Cause is
not reported to maintenance personnel because it might exist only for
a very short period of time. Note that some of these events are
summed up in the Performance Monitoring process (see Section 7), and
when this sum exceeds a configured value, a threshold crossing alert
(report) can be generated.
When the Fault Cause lasts long enough, an inability to perform the
required transport function arises. This failure condition is
subject to reporting to maintenance personnel and/or an OS because
corrective action might be required. Conversely, when the Fault
Cause ceases after a certain time, clearing of the Failure condition
is also subject to reporting.
1) The MPLS-TP NE MUST perform persistency checks on fault causes
before it declares a fault cause a failure.
2) The MPLS-TP NE SHOULD provide a configuration capability for
control parameters associated with performing the persistency
checks described above.
3) An MPLS-TP NE MAY provide configuration parameters to control
reporting and clearing of failure conditions.
4) A data-plane forwarding path failure MUST be declared if the fault
cause persists continuously for a configurable time (Time-D). The
failure MUST be cleared if the fault cause is absent continuously
for a configurable time (Time-C).
Note: As an example, the default time values might be as follows:
Time-D = 2.5 +/- 0.5 seconds
Time-C = 10 +/- 0.5 seconds
These time values are as defined in G.7710 .
5) MIBs - or other object management semantics specifications -
defined to enable configuration of these timers SHOULD explicitly
provide default values and MAY provide guidelines on ranges and
value determination methods for scenarios where the default value
chosen might be inadequate. In addition, such specifications
SHOULD define the level of granularity at which tables of these
values are to be defined.
6) Implementations MUST provide the ability to configure the
preceding set of timers and SHOULD provide default values to
enable rapid configuration. Suitable default values, timer
ranges, and level of granularity are out of scope in this document
and form part of the specification of fault management details.
Timers SHOULD be configurable per NE for broad categories (for
example, defects and/or fault causes), and MAY be configurable
per-interface on an NE and/or per individual defect/fault cause.
7) The failure declaration and clearing MUST be time stamped. The
time-stamp MUST indicate the time at which the fault cause is
activated at the input of the fault cause persistency (i.e.,
defect-to-failure integration) function, and the time at which the
fault cause is deactivated at the input of the fault cause
5.3. Alarm Handling Function
5.3.1. Alarm Severity Assignment
Failures can be categorized to indicate the severity or urgency of
1) An MPLS-TP NE SHOULD support the ability to assign severity (e.g.,
Critical, Major, Minor, Warning) to alarm conditions via
See G.7710 , Section 7.2.2 for more detail on alarm severity
assignment. For additional discussion of Alarm Severity management,
see discussion of alarm severity in RFC 3877 .
5.3.2. Alarm Suppression
Alarms can be generated from many sources, including OAM, device
1) An MPLS-TP NE MUST support suppression of alarms based on
5.3.3. Alarm Reporting
Alarm Reporting is concerned with the reporting of relevant events
and conditions, which occur in the network (including the NE,
incoming signal, and external environment).
Local reporting is concerned with automatic alarming by means of
audible and visual indicators near the failed equipment.
1) An MPLS-TP NE MUST support local reporting of alarms.
2) The MPLS-TP NE MUST support reporting of alarms to an OS. These
reports are either autonomous reports (notifications) or reports
on request by maintenance personnel. The MPLS-TP NE SHOULD report
local (environmental) alarms to a network management system.
3) An MPLS-TP NE supporting one or more other networking technologies
(e.g., Ethernet, SDH/SONET, MPLS) over MPLS-TP MUST be capable of
translating MPLS-TP defects into failure conditions that are
meaningful to the client layer, as described in RFC 4377 ,
5.3.4. Alarm Reporting Control
Alarm Reporting Control (ARC) supports an automatic in-service
provisioning capability. Alarm reporting can be turned off on a per-
managed entity basis (e.g., LSP) to allow sufficient time for
customer service testing and other maintenance activities in an
"alarm free" state. Once a managed entity is ready, alarm reporting
is automatically turned on.
1) An MPLS-TP NE SHOULD support the Alarm Reporting Control function
for controlling the reporting of alarm conditions.
See G.7710  (Section 18.104.22.168) and RFC 3878  for more
information about ARC.
6. Configuration Management Requirements
Configuration Management provides functions to identify, collect data
from, provide data to, and control NEs. Specific configuration tasks
requiring network management support include hardware and software
configuration, configuration of NEs to support transport paths
(including required working and protection paths), and configuration
of required path integrity/connectivity and performance monitoring
6.1. System Configuration
1) The MPLS-TP NE MUST support the configuration requirements
specified in G.7710 , Section 8.1 for hardware.
2) The MPLS-TP NE MUST support the configuration requirements
specified in G.7710 , Section 8.2 for software.
3) The MPLS-TP NE MUST support the configuration requirements
specified in G.7710 , Section 22.214.171.124 for local real-time
4) The MPLS-TP NE MUST support the configuration requirements
specified in G.7710 , Section 126.96.36.199 for local real-time
clock alignment with external time reference.
5) The MPLS-TP NE MUST support the configuration requirements
specified in G.7710 , Section 188.8.131.52 for performance
monitoring of the clock function.
6.2. Control Plane Configuration
1) If a control plane is supported in an implementation of MPLS-TP,
the MPLS-TP NE MUST support the configuration of MPLS-TP control
plane functions by the management plane. Further detailed
requirements will be provided along with progress in defining the
MPLS-TP control plane in appropriate specifications.
6.3. Path Configuration
1) In addition to the requirement to support static provisioning of
transport paths (defined in RFC 5645 , Section 2.1 -- General
Requirements, requirement 18), an MPLS-TP NE MUST support the
configuration of required path performance characteristic
thresholds (e.g., Loss Measurement <LM>, Delay Measurement <DM>
thresholds) necessary to support performance monitoring of the
2) In order to accomplish this, an MPLS-TP NE MUST support
configuration of LSP information (such as an LSP identifier of
some kind) and/or any other information needed to retrieve LSP
status information, performance attributes, etc.
3) If a control plane is supported, and that control plane includes
support for control-plane/management-plane hand-off for LSP
setup/maintenance, the MPLS-TP NE MUST support management of the
hand-off of Path control. For example, see RFCs 5943  and
4) Further detailed requirements SHALL be provided along with
progress in defining the MPLS-TP control plane in appropriate
5) If MPLS-TP transport paths cannot be statically provisioned using
MPLS LSP and pseudowire management tools (either already defined
in standards or under development), further management
specifications MUST be provided as needed.
6.4. Protection Configuration
1) The MPLS-TP NE MUST support configuration of required path
protection information as follows:
o designate specifically identified LSPs as working or protecting
o define associations of working and protecting paths;
o operate/release manual protection switching;
o operate/release force protection switching;
o operate/release protection lockout;
o set/retrieve Automatic Protection Switching (APS) parameters,
o Wait to Restore time,
o Protection Switching threshold information.
6.5. OAM Configuration
1) The MPLS-TP NE MUST support configuration of the OAM entities and
functions specified in RFC 5860 .
2) The MPLS-TP NE MUST support the capability to choose which OAM
functions are enabled.
3) For enabled OAM functions, the MPLS-TP NE MUST support the ability
to associate OAM functions with specific maintenance entities.
4) The MPLS-TP NE MUST support the capability to configure the OAM
entities/functions as part of LSP setup and tear-down, including
co-routed bidirectional point-to-point, associated bidirectional
point-to-point, and uni-directional (both point-to-point and
5) The MPLS-TP NE MUST support the configuration of maintenance
entity identifiers (e.g., MEP ID and MIP ID) for the purpose of
LSP connectivity checking.
6) The MPLS-TP NE MUST support configuration of OAM parameters to
meet their specific operational requirements, such as
a) one-time on-demand immediately or
b) one-time on-demand pre-scheduled or
c) on-demand periodically based on a specified schedule or
d) proactive on-going.
7) The MPLS-TP NE MUST support the enabling/disabling of the
connectivity check processing. The connectivity check process of
the MPLS-TP NE MUST support provisioning of the identifiers to be
transmitted and the expected identifiers.
7. Performance Management Requirements
Performance Management provides functions for the purpose of
maintenance, bring-into-service, quality of service, and statistics
This information could be used, for example, to compare behavior of
the equipment, MPLS-TP NE, or network at different moments in time to
evaluate changes in network performance.
ITU-T Recommendation G.7710  provides transport performance
monitoring requirements for packet-switched and circuit-switched
transport networks with the objective of providing a coherent and
consistent interpretation of the network behavior in a multi-
technology environment. The performance management requirements
specified in this document are driven by such an objective.
7.1. Path Characterization Performance Metrics
1) It MUST be possible to determine when an MPLS-TP-based transport
service is available and when it is unavailable.
From a performance perspective, a service is unavailable if there is
an indication that performance has degraded to the extent that a
configurable performance threshold has been crossed and the
degradation persists long enough (i.e., the indication persists for
some amount of time, which is either configurable or well-known) to
be certain it is not a measurement anomaly.
Methods, mechanisms, and algorithms for exactly how unavailability is
to be determined -- based on collection of raw performance data --
are out of scope for this document.
2) The MPLS-TP NE MUST support collection and reporting of raw
performance data that MAY be used in determining the
unavailability of a transport service.
3) MPLS-TP MUST support the determination of the unavailability of
the transport service. The result of this determination MUST be
available via the MPLS-TP NE (at service termination points), and
determination of unavailability MAY be supported by the MPLS-TP NE
directly. To support this requirement, the MPLS-TP NE management
information model MUST include objects corresponding to the
availability-state of services.
Transport network unavailability is based on Severely Errored Seconds
(SES) and Unavailable Seconds (UAS). The ITU-T is establishing
definitions of unavailability that are generically applicable to
packet transport technologies, including MPLS-TP, based on SES and
UAS. Note that SES and UAS are already defined for Ethernet
transport networks in ITU-T Recommendation Y.1563 .
4) The MPLS-TP NE MUST support collection of loss measurement (LM)
5) The MPLS-TP NE MUST support collection of delay measurement (DM)
6) The MPLS-TP NE MUST support reporting of performance degradation
via fault management for corrective actions.
"Reporting" in this context could mean:
o reporting to an autonomous protection component to trigger
o reporting via a craft interface to allow replacement of a
faulty component (or similar manual intervention),
7) The MPLS-TP NE MUST support reporting of performance statistics on
request from a management system.
7.2. Performance Measurement Instrumentation
7.2.1. Measurement Frequency
1) For performance measurement mechanisms that support both proactive
and on-demand modes, the MPLS-TP NE MUST support the capability to
be configured to operate on-demand or proactively.
7.2.2. Measurement Scope
On measurement of packet loss and loss ratio:
1) For bidirectional (both co-routed and associated) point-to-point
a) on-demand measurement of single-ended packet loss and loss
ratio measurement is REQUIRED;
b) proactive measurement of packet loss and loss ratio measurement
for each direction is REQUIRED.
2) For unidirectional (P2P and point-to-multipoint (P2MP))
connection, proactive measurement of packet loss and loss ratio is
On Delay measurement:
3) For a unidirectional (P2P and P2MP) connection, on-demand
measurement of delay measurement is REQUIRED.
4) For a co-routed bidirectional (P2P) connection, on-demand
measurement of one-way and two-way delay is REQUIRED.
5) For an associated bidirectional (P2P) connection, on-demand
measurement of one-way delay is REQUIRED.
8. Security Management Requirements
1) The MPLS-TP NE MUST support secure management and control planes.
8.1. Management Communication Channel Security
1) Secure communication channels MUST be supported for all network
traffic and protocols used to support management functions. This
MUST include, at least, protocols used for configuration,
monitoring, configuration backup, logging, time synchronization,
authentication, and routing.
2) The MCC MUST support application protocols that provide
confidentiality and data-integrity protection.
3) The MPLS-TP NE MUST support the following:
a) Use of open cryptographic algorithms (see RFC 3871 ).
b) Authentication - allow management connectivity only from
c) Authorization - allow management activity originated by an
authorized entity, using (for example) an Access Control List
d) Port Access Control - allow management activity received on an
authorized (management) port.
8.2. Signaling Communication Channel Security
Security requirements for the SCC are driven by considerations
similar to MCC requirements described in Section 8.1.
Security Requirements for the control plane are out of scope for this
document and are expected to be defined in the appropriate control
1) Management of control plane security MUST be defined in the
appropriate control plane specifications.
8.3. Distributed Denial of Service
A denial-of-service (DoS) attack is an attack that tries to prevent a
target from performing an assigned task, or providing its intended
service(s), through any means. A Distributed DoS (DDoS) can multiply
attack severity (possibly by an arbitrary amount) by using multiple
(potentially compromised) systems to act as topologically (and
potentially geographically) distributed attack sources. It is
possible to lessen the impact and potential for DoS and DDoS by using
secure protocols, turning off unnecessary processes, logging and
monitoring, and ingress filtering. RFC 4732  provides background
on DoS in the context of the Internet.
1) An MPLS-TP NE MUST support secure management protocols and SHOULD
do so in a manner that reduces potential impact of a DoS attack.
2) An MPLS-TP NE SHOULD support additional mechanisms that mitigate a
DoS (or DDoS) attack against the management component while
allowing the NE to continue to meet its primary functions.
9. Security Considerations
Section 8 includes a set of security requirements that apply to MPLS-
TP network management.
1) Solutions MUST provide mechanisms to prevent unauthorized and/or
unauthenticated access to management capabilities and private
information by network elements, systems, or users.
Performance of diagnostic functions and path characterization
involves extracting a significant amount of information about network
construction that the network operator might consider private.
The authors/editors gratefully acknowledge the thoughtful review,
comments, and explanations provided by Adrian Farrel, Alexander
Vainshtein, Andrea Maria Mazzini, Ben Niven-Jenkins, Bernd Zeuner,
Dan Romascanu, Daniele Ceccarelli, Diego Caviglia, Dieter Beller, He
Jia, Leo Xiao, Maarten Vissers, Neil Harrison, Rolf Winter, Yoav
Cohen, and Yu Liang.
11.1. Normative References
 ITU-T Recommendation G.7710/Y.1701, "Common equipment
management function requirements", July, 2007.
 Nadeau, T., Morrow, M., Swallow, G., Allan, D., and S.
Matsushima, "Operations and Management (OAM) Requirements for
Multi-Protocol Label Switched (MPLS) Networks", RFC 4377,
 Vigoureux, M., Ed., Ward, D., Ed., and M. Betts, Ed.,
"Requirements for Operations, Administration, and Maintenance
(OAM) in MPLS Transport Networks", RFC 5860, May 2010.
 Jones, G., Ed., "Operational Security Requirements for Large
Internet Service Provider (ISP) IP Network Infrastructure", RFC
3871, September 2004.
 Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
 ITU-T Recommendation G.7712/Y.1703, "Architecture and
specification of data communication network", June 2008.
 Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed.,
Sprecher, N., and S. Ueno, "Requirements of an MPLS Transport
Profile", RFC 5654, September 2009.
 Bocci, M., Ed., Bryant, S., Ed., Frost, D., Ed., Levrau, L.,
and L. Berger, "A Framework for MPLS in Transport Networks",
RFC 5921, July 2010.
 Mansfield, S. Ed., Gray, E., Ed., and K. Lam, Ed., "Network
Management Framework for MPLS-based Transport Networks", RFC
5950, September 2010.
12.2. Informative References
 Beller, D. and A. Farrel, "An In-Band Data Communication
Network For the MPLS Transport Profile", RFC 5718, January
 Chisholm, S. and D. Romascanu, "Alarm Management Information
Base (MIB)", RFC 3877, September 2004.
 ITU-T Recommendation M.20, "Maintenance philosophy for
telecommunication networks", October 1992.
 Telcordia, "Network Maintenance: Network Element and Transport
Surveillance Messages" (GR-833-CORE), Issue 5, August 2004.
 Bocci, M., Ed., Vigoureux, M., Ed., and S. Bryant, Ed., "MPLS
Generic Associated Channel", RFC 5586, June 2009.
 Harrington, D., "Guidelines for Considering Operations and
Management of New Protocols and Protocol Extensions", RFC 5706,
 Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed., and
A. Bierman, Ed., "Network Configuration Protocol (NETCONF)",
Work in Progress, July 2010.
 Presuhn, R., Ed., "Version 2 of the Protocol Operations for the
Simple Network Management Protocol (SNMP)", STD 62, RFC 3416,
 OMG Document formal/04-03-12, "The Common Object Request
Broker: Architecture and Specification", Revision 3.0.3. March
 Caviglia, D., Bramanti, D., Li, D., and D. McDysan,
"Requirements for the Conversion between Permanent Connections
and Switched Connections in a Generalized Multiprotocol Label
Switching (GMPLS) Network", RFC 5493, April 2009.
 Caviglia, D., Ceccarelli, D., Bramanti, D., Li, D., and S.
Bardalai, "RSVP-TE Signaling Extension for LSP Handover from
the Management Plane to the Control Plane in a GMPLS-Enabled
Transport Network", RFC 5852, April 2010.
 ITU-T Recommendation G.806, "Characteristics of transport
equipment - Description methodology and generic functionality",
 ITU-T Recommendation Y.1731, "OAM functions and mechanisms for
Ethernet based networks", February, 2008.
 ITU-T Recommendation G.8601, "Architecture of service
management in multi bearer, multi carrier environment", June
 Lam, H., Huynh, A., and D. Perkins, "Alarm Reporting Control
Management Information Base (MIB)", RFC 3878, September 2004.
 ITU-T Recommendation Y.1563, "Ethernet frame transfer and
availability performance", January 2009.
 Handley, M., Ed., Rescorla, E., Ed., and IAB, "Internet Denial-
of-Service Considerations", RFC 4732, December 2006.
Appendix A. Communication Channel (CCh) Examples
A CCh can be realized in a number of ways.
1. The CCh can be provided by a link in a physically distinct
network, that is, a link that is not part of the transport network
that is being managed. For example, the nodes in the transport
network can be interconnected in two distinct physical networks:
the transport network and the DCN.
This is a "physically distinct out-of-band CCh".
2. The CCh can be provided by a link in the transport network that is
terminated at the ends of the DCC and that is capable of
encapsulating and terminating packets of the management protocols.
For example, in MPLS-TP, a single-hop LSP might be established
between two adjacent nodes, and that LSP might be capable of
carrying IP traffic. Management traffic can then be inserted into
the link in an LSP parallel to the LSPs that carry user traffic.
This is a "physically shared out-of-band CCh."
3. The CCh can be supported as its native protocol on the interface
alongside the transported traffic. For example, if an interface
is capable of sending and receiving both MPLS-TP and IP, the IP-
based management traffic can be sent as native IP packets on the
This is a "shared interface out-of-band CCh".
4. The CCh can use overhead bytes available on a transport
connection. For example, in TDM networks there are overhead bytes
associated with a data channel, and these can be used to provide a
CCh. It is important to note that the use of overhead bytes does
not reduce the capacity of the associated data channel.
This is an "overhead-based CCh".
This alternative is not available in MPLS-TP because there is no
5. The CCh can be provided by a dedicated channel associated with the
data link. For example, the generic associated label (GAL) 
can be used to label DCC traffic being exchanged on a data link
between adjacent transport nodes, potentially in the absence of
any data LSP between those nodes.
This is a "data link associated CCh".
It is very similar to case 2, and by its nature can only span a
single hop in the transport network.
6. The CCh can be provided by a dedicated channel associated with a
data channel. For example, in MPLS-TP, the GAL  can be
imposed under the top label in the label stack for an MPLS-TP LSP
to create a channel associated with the LSP that can carry
management traffic. This CCh requires the receiver to be capable
of demultiplexing management traffic from user traffic carried on
the same LSP by use of the GAL.
This is a "data channel associated CCh".
7. The CCh can be provided by mixing the management traffic with the
user traffic such that is indistinguishable on the link without
deep-packet inspection. In MPLS-TP, this could arise if there is
a data-carrying LSP between two nodes, and management traffic is
inserted into that LSP. This approach requires that the
termination point of the LSP be able to demultiplex the management
and user traffic. This might be possible in MPLS-TP if the MPLS-
TP LSP is carrying IP user traffic.
This is an "in-band CCh".
These realizations can be categorized as:
A. Out-of-fiber, out-of-band (types 1 and 2)
B. In-fiber, out-of-band (types 2, 3, 4, and 5)
C. In-band (types 6 and 7)
The MCN and SCN are logically separate networks and can be realized
by the same DCN or as separate networks. In practice, that means
that, between any pair of nodes, the MCC and SCC can be the same link
or separate links.
It is also important to note that the MCN and SCN do not need to be
categorised as in-band, out-of-band, etc. This definition only
applies to the individual links, and it is possible for some nodes to
be connected in the MCN or SCN by one type of link, and other nodes
by other types of link. Furthermore, a pair of adjacent nodes can be
connected by multiple links of different types.
Lastly, note that the division of DCN traffic between links between a
pair of adjacent nodes is purely an implementation choice. Parallel
links can be deployed for DCN resilience or load sharing. Links can
be designated for specific use. For example, so that some links
carry management traffic and some carry control plane traffic, or so
that some links carry signaling protocol traffic while others carry
routing protocol traffic.
It is important to note that the DCN can be a routed network with
forwarding capabilities, but that this is not a requirement. The
ability to support forwarding of management or control traffic within
the DCN can substantially simplify the topology of the DCN and
improve its resilience, but does increase the complexity of operating
See also RFC 3877 , ITU-T M.20 , and Telcordia document
GR-833-CORE  for further information.
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