MPLS-TP management: Network Management Framework for MPLS-based Transport Networks
How an MPLS transport network should be managed: the architecture, and what the equipment has to do about faults, configuration and performance.
Mansfield, S., Ed., Gray, E., Ed., and K. Lam, Ed., "Network Management Framework for MPLS-based Transport Networks", RFC 5950, DOI 10.17487/RFC5950, September 2010, <https://www.rfc-editor.org/info/rfc5950>.
@misc{rfc5950,
series = {Request for Comments},
number = 5950,
howpublished = {RFC 5950},
publisher = {RFC Editor},
doi = {10.17487/RFC5950},
url = {https://www.rfc-editor.org/info/rfc5950},
author = {S. Mansfield and E. Gray and K. Lam},
title = {{Network Management Framework for MPLS-based Transport Networks}},
pagetotal = 18,
year = 2010,
month = sep,
} RFC text
Contents
Internet Engineering Task Force (IETF) S. Mansfield, Ed.
Request for Comments: 5950 E. Gray, Ed.
Category: Informational Ericsson
ISSN: 2070-1721 K. Lam, Ed.
Alcatel-Lucent
September 2010
Network Management Framework for MPLS-based Transport Networks
Abstract
This document provides the network management framework for the
Transport Profile for Multi-Protocol Label Switching (MPLS-TP).
This framework relies on the management terminology from the ITU-T to
describe the management architecture that could be used for an MPLS-
TP management network.
The management of the MPLS-TP network could be based on multi-tiered
distributed management systems. This document provides a description
of the network and element management architectures that could be
applied and also describes heuristics associated with fault,
configuration, and performance aspects of the management system.
This document is a product of a joint Internet Engineering Task Force
(IETF) / International Telecommunication Union Telecommunication
Standardization Sector (ITU-T) effort to include an MPLS Transport
Profile within the IETF MPLS and PWE3 architectures to support the
capabilities and functionalities of a packet transport network.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for informational purposes.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Not all documents
approved by the IESG are a candidate for any level of Internet
Standard; see Section 2 of RFC 5741.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc5950.
Copyright Notice
Copyright (c) 2010 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
(http://trustee.ietf.org/license-info) in effect on the date of
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described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2. Management Architecture . . . . . . . . . . . . . . . . . . . 5
2.1. Network Management Architecture . . . . . . . . . . . . . 5
2.2. Element Management Architecture . . . . . . . . . . . . . 6
2.3. Standard Management Interfaces . . . . . . . . . . . . . . 10
2.4. Management- and Control-Specific Terminology . . . . . . . 11
2.5. Management Channel . . . . . . . . . . . . . . . . . . . . 11
3. Fault Management . . . . . . . . . . . . . . . . . . . . . . . 13
3.1. Supervision . . . . . . . . . . . . . . . . . . . . . . . 13
3.2. Validation . . . . . . . . . . . . . . . . . . . . . . . . 13
3.3. Alarm Handling . . . . . . . . . . . . . . . . . . . . . . 13
4. Configuration Management . . . . . . . . . . . . . . . . . . . 13
4.1. LSP Ownership Handover . . . . . . . . . . . . . . . . . . 14
5. Performance Management . . . . . . . . . . . . . . . . . . . . 15
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 15
7. Security Considerations . . . . . . . . . . . . . . . . . . . 16
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 16
8.1. Normative References . . . . . . . . . . . . . . . . . . . 16
8.2. Informative References . . . . . . . . . . . . . . . . . . 17
1. Introduction
This document provides the network management framework for the
Transport Profile for Multi-Protocol Label Switching (MPLS-TP).
Requirements for network management in an MPLS-TP network are
documented in "Network Management Requirements for MPLS-based
Transport Networks" [3], and this document explains how network
elements and networks that support MPLS-TP can be managed using
solutions that satisfy those requirements. The relationship between
Operations, Administration, and Maintenance (OAM), management, and
other framework documents is described in the MPLS-TP framework [4]
document.
This document is a product of a joint Internet Engineering Task Force
(IETF) / International Telecommunication Union Telecommunication
Standardization Sector (ITU-T) effort to include an MPLS Transport
Profile within the IETF MPLS and PWE3 architectures to support the
capabilities and functionalities of a packet transport network.
1.1. Terminology
This framework relies on the management terminology from the ITU-T to
describe the management architecture that could be used for an
MPLS-TP management network. The terminology listed below are taken
from/based on the definitions found in ITU-T G.7710 [6], ITU-T G.7712
[7], and ITU-T M.3013 [13].
o Communication Channel (CCh): A logical channel between network
elements (NEs) that can be used in (for example) management plane
applications or control plane applications. For MPLS-TP, the
physical channel supporting the CCh is the MPLS-TP Management
Communication Channel (MCC).
o Data Communication Network (DCN): A network that supports Layer 1
(physical), Layer 2 (data-link), and Layer 3 (network)
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 downloads, etc.).
See ITU-T G.7712 [7].
o Equipment Management Function (EMF): The management functions
within an NE. See ITU-T G.7710 [6].
o Local Craft Terminal (LCT): An out-of-band device that connects to
an NE for management purposes. See ITU-T G.7710 [6].
o Label Switched Path (LSP): An MPLS-TP LSP is an LSP that uses a
subset of the capabilities of an MPLS LSP in order to meet the
requirements of an MPLS transport network as described in the
MPLS-TP framework [4].
o Management Application Function (MAF): An application process that
participates in system management. See ITU-T G.7710 [6].
o Management Communication Channel (MCC): A CCh dedicated for
management plane communications. See ITU-T G.7712 [7].
o Message Communication Function (MCF): The communications process
that performs functions such as information interchange and relay.
See ITU-T M.3013 [13].
o Management Communication Network (MCN): A DCN supporting
management plane communication is referred to as a Management
Communication Network (MCN). See ITU-T G.7712 [7].
o MPLS-TP NE: A network element (NE) that supports MPLS-TP
functions. Another term that is used for a network element is
node. In terms of this document, the term node is equivalent to
NE.
o MPLS-TP network: A network in which MPLS-TP NEs are deployed.
o Network Element Function (NEF): The set of functions necessary to
manage a network element. See ITU-T M.3010 [11].
o Operations, Administration, and Maintenance (OAM): For the MPLS-TP
effort the term OAM means the set of tools that consist of
"operation" activities that are undertaken to keep the network up
and running, "administration" activities that keep track of
resources in the network and how they are used, and "maintenance"
activities that facilitate repairs and upgrades. For a complete
expansion of the acronym, see "The OAM Acronym Soup" [15].
o Operations System (OS): A system that performs the functions that
support processing of information related to operations,
administration, maintenance, and provisioning (OAM&P) (see "The
OAM Acronym Soup" [15]) for the networks, including surveillance
and testing functions to support customer access maintenance. See
ITU-T M.3010 [11].
o Signaling Communication Network (SCN): A DCN supporting control
plane communication is referred to as a Signaling Communication
Network (SCN). See ITU-T G.7712 [7].
o Signaling Communication Channel (SCC): A CCh dedicated for control
plane communications. The SCC may be used for GMPLS/ASON
signaling and/or other control plane messages (e.g., routing
messages). See ITU-T G.7712 [7].
2. Management Architecture
The management of the MPLS-TP network could be based on a multi-
tiered distributed management systems, for example as described in
ITU-T M.3010 [11] and ITU-T M.3060/Y.2401 [12]. Each tier provides a
predefined level of network management capabilities. The lowest tier
of this organization model includes the MPLS-TP network element that
provides the transport service and the Operations System (OS) at the
Element Management Level. The Management Application Function (MAF)
within the NEs and OSs provides the management support. The MAF at
each entity can include agents only, managers only, or both agents
and managers. The MAF that includes managers is capable of managing
an agent included in other MAF.
The management communication to peer NEs and/or OSs is provided via
the Message Communication Function (MCF) within each entity (e.g., NE
and OS). The user can access the management of the MPLS-TP transport
network via a Local Craft Terminal (LCT) attached to the NE or via a
Work Station (WS) attached to the OS.
2.1. Network Management Architecture
A transport Management Network (MN) may consist of several transport-
technology-specific Management Networks. Management network
partitioning (Figure 1) below (based on ITU-T G.7710 [6]) shows the
management network partitioning. Notation used in G.7710 for a
transport-technology-specific MN is x.MN, where x is the transport-
specific technology. An MPLS-TP-specific MN is abbreviated as MT.MN.
Where there is no ambiguity, we will use "MN" for an MPLS-TP-specific
MN. In the figure below, O.MSN is equivalent to an OTN management
Subnetwork.
______________________________ _________________________________
|.-------.-------.----.-------.||.--------.--------.----.--------.|
|: : : : :||: : : : :|
|:O.MSN-1:O.MSN-2: .. :O.MSN-n:||:MT.MSN-1:MT.MSN-2: .. :MT.MSN-n:|
|: : : : :||: : : : :|
'-============================-''-===============================-'
_______________________________
|.-------.-------.-----.-------.|
|: : : : :|
|:x.MSN-1:x.MSN-2: ... :x.MSN-n:|
|: : : : :|
'-=============================-'
Management Network Partitioning
Figure 1
The management of the MPLS-TP network is separable from the
management of the other technology-specific networks, and it operates
independently of any particular client- or server-layer management
plane.
An MPLS-TP Management Network (MT.MN) could be partitioned into
MPLS-TP Management SubNetworks ("MT.MSN" or "MPLS-TP MSN", or just
"MSN" where usage is unambiguous) for consideration of scalability
(e.g., geographic or load balancing) or administration (e.g.,
operation or ownership).
The MPLS-TP MSN could be connected to other parts of the MN through
one or more LCTs and/or OSs. The Message Communication Function
(MCF) of an MPLS-TP NE initiates/terminates, routes, or otherwise
processes management messages over CChs or via an external interface.
Multiple addressable MPLS-TP NEs could be present at a single
physical location (i.e., site or office). The inter-site
communications link between the MPLS-TP NEs will normally be provided
by the CChs. Within a particular site, the NEs could communicate via
an intra-site CCh or via a LAN.
2.2. Element Management Architecture
The Equipment Management Function (EMF) of an MPLS-TP NE provides the
means through which a management system manages the NE.
The EMF interacts with the NE's transport functions by exchanging
Management Information (MI) across the Management Point (MP)
Reference Points. The EMF may contain a number of functions that
provide a data reduction mechanism on the information received across
the MP Reference Points.
The EMF includes functions such as Date and Time, FCAPS (Fault,
Configuration, Accounting, Performance, and Security) management, and
Control Plane functions. The EMF provides event message processing,
data storage, and logging. The management Agent, a component of the
EMF, converts internal management information (MI signals) into
Management Application messages and vice versa. The Agent responds
to Management Application messages from the Message Communication
Function (MCF) by performing the appropriate operations on (for
example) the Managed Objects in a Management Information Base (MIB),
as necessary. The MCF contains communications functions related to
the world outside of the NE (i.e., Date and Time source, Management
Plane, Control Plane, Local Craft Terminal, and Local Alarms).
The Date and Time functions keep track of the NE's date/time, which
is used by the FCAPS management functions to e.g., time stamp event
reports.
Below are diagrams that illustrate the components of the Equipment
Management Function (EMF) of a Network Element (NE). The high-level
decomposition of the Network Element Function (NEF) picture
(Figure 2) provides the breakdown of the NEF, then the EMF picture
(Figure 3) provides the details of Equipment Management Function, and
finally the Message Communication Function (MCF) picture (Figure 4)
details the MCF.
____________________________________________________
| Network Element Function (NEF) |
| _________________________________________ |
|| | |
|| Transport Plane Atomic Functions | |
||_________________________________________| |
| | |
| | Management |
| | Information |
| ___________________|_________________ |
| | (from date/time)<-----------+ |
| | Equipment | | |
| | Management (to/from management)<--------+ | |
| | Function | | | |
| | (EMF) (to/from control)<-----+ | | |
| | | | | | |
| | (to local alarm)---+ | | | |
| |_____________________________________| | | | | |
| | | | | |
| +--------------------------------------+ | | | |
| | +---------------------------------------+ | | |
| | | +----------------------------------------+ | |
| | | | +-----------------------------------------+ |external
| | | | | Date & Time _________________ |time
| | | | | Interface | Message | |source
| | | | +-------------- Communication <-----------------------
| | | | | Function (MCF) | |
| | | | Management | | |management
| | | +----------------> | |plane
| | | Plane Interface <---------------------->
| | | | | |local
| | | | | |craft
| | | Control Plane | | |terminal
| | +------------------> <---------------------->
| | Interface | | |control
| | | | |plane
| | Local Alarm | <---------------------->
| +--------------------> | |
| Interface | | |to local
| | | |alarms
| |_________________--------------------->
|____________________________________________________|
High-Level Decomposition of NEF
Figure 2
______________________________________________________
| _______________________________________ |
| Equipment | Management Application ||
| Management | Function (MAF) ||
| Function | _________________ ||
| (EMF) || | __________________||
| ___________||_______________ | | ||
| | | | | Date & Time ||
| | Date & Time Functions | | | Interface ||<-- 1
| |____________________________| | |__________________||
| ___________||_______________ | __________________||
| | | | | ||
| | Fault Management | | | Management ||
| |____________________________| | | Plane Interface ||<-> 2
| ___________||_______________ | |__________________||
| | | | ||
| | Configuration Management | | __________________||
| |____________________________| | | ||
| ___________||_______________ | | Control ||
| | | | | Plane Interface ||<-> 3
| | Account Management | | |__________________||
| |____________________________| | ||
| ___________||_______________ | ||
| | | | ||
| | Performance Management | | ||
| |____________________________| | ||
| ___________||_______________ | ||
| | | | ||
| | Security Management | | ||
| |____________________________| | ||
| ___________||_______________ | ||
| | | | ||
| | Control Plane Function | | ||
| |____________________________| | ||
| || | __________________||
| || | | ||
| || | | Local Alarm ||
| +----->| Agent | | Interface ||--> 4
| v ||_________________| |__________________||
| .-===-. |_______________________________________||
| | MIB | |
| `-._.-' |
|______________________________________________________|
Equipment Management Function
Figure 3
_________________
| |
| Message |
| Communication |
| Function (MCF) |
| _______________ |
Date & Time || || external
1 <--------------|| Date & Time ||<--------------
Information || Communication || time source
||_______________||
| |
| _______________ |
Management || || management
Plane || Management || plane
2 <------------->|| Plane ||<------------->
Information || Communication || (e.g. - EMS,
||_______________|| peer NE)
| |
| _______________ | control
Control Plane || || plane
3 <------------->|| Control Plane ||<------------->
Information || Communication || (e.g. - EMS,
||_______________|| peer NE)
| : |
| : | local craft
| : | terminal
| : |<------------->
| _______________ |
Local Alarm || || to local
4 -------------->|| Local Alarm ||-------------->
Information || Communication || alarms...
||_______________||
|_________________|
Message Communication Function
Figure 4
2.3. Standard Management Interfaces
The "Network Management Requirements for MPLS-based Transport
Networks" document [3] places no restriction on which management
interface is to be used for managing an MPLS-TP network. It is
possible to provision and manage an end-to-end connection across a
network where some segments are created/managed/deleted, for example
by NETCONF or SNMP and other segments by CORBA interfaces. Use of
any network management interface for one management-related purpose
does not preclude use of another network management interface for
other management-related purposes, or the same purpose at another
time. The protocol(s) to be supported are at the discretion of the
operator.
2.4. Management- and Control-Specific Terminology
Data Communication Network (DCN) is the common term for the network
used to transport Management and Signaling information between:
management systems and network elements, management systems to other
management systems, and networks elements to other network elements.
The Management Communications Network (MCN) is the part of the DCN
that supports the transport of Management information for the
Management Plane. The Signaling Communications Network (SCN) is the
part of the DCN that supports transport of signaling information for
the Control Plane. As shown in , the communication channel
terminology picture (Figure 5) each technology has its own
terminology that is used for the channels that support the transfer
of management and control plane information. For MPLS-TP, the
management plane uses the Management Communication Channel (MCC), and
the control plane uses the Signaling Communication Channel (SCC).
2.5. Management Channel
The Communication Channel (CCh) provides a logical channel between
NEs for transferring Management and/or Signaling information. Note
that some technologies provide separate communication channels for
Management (MCC) and Signaling (SCC).
MPLS-TP NEs communicate via the DCN. The DCN connects NEs with
management systems, NEs with NEs, and management systems with
management systems.
Common Terminology ____
__________ __________ | |
| | | | /->| NE | \ ____
|Management| |Operations| / |____| \ | |
|Station | <---> |System | |(CCh) | NE |
|__________| |__________| \ _|__ / |____|
\->| | /
| NE |
|____|
Network Elements use a Communication
Channel (CCh) for Transport of Information
Management Terminology ____
__________ __________ | |
| | | | /->| NE | \ ____
|Management| |Operations| / |____| \ | |
|Station | <---> |System | |(MCC) | NE |
|__________| |__________| \ _|__ / |____|
\->| | /
| NE |
|____|
Network Elements use a Management
Communication Channel (MCC) for Transport
of Management Information
Control Terminology ____
__________ __________ | |
| | | | /->| NE | \ ____
|Management| |Operations| / |____| \ | |
|Station | <---> |System | |(SCC) | NE |
|__________| |__________| \ _|__ / |____|
\->| | /
| NE |
|____|
Network Elements use a Control/Signaling
Communication Channel (SCC) for Transport
of Signaling Information
Communication Channel Terminology
Figure 5
3. Fault Management
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. Fault management
provides the mechanisms to detect, verify, isolate, notify, and
recover from the fault.
3.1. Supervision
ITU-T G.7710 [6] lists five basic categories of supervision that
provide the functionality necessary to detect, verify, and notify a
fault. The categories are: Transmission Supervision, Quality of
Service Supervision, Processing Supervision, Hardware Supervision,
and Environment Supervision. Each of the categories provides a set
of recommendations to ensure that the fault management process is
fulfilled.
3.2. Validation
ITU-T G.7710 [6] describes a fault cause as a limited interruption of
the required function. It is not reasonable for every fault cause to
be reported to maintenance personnel. The validation process is used
to turn fault causes (events) into failures (alarms).
3.3. Alarm Handling
Within an element management system, it is important to consider
mechanisms to support severity assignment, alarm reporting control,
and logging.
4. Configuration Management
Configuration management provides the mechanisms to:
o provision the MPLS-TP services
o set up security for the MPLS-TP services and MPLS-TP network
elements
o provide the destination for fault notifications and performance
parameters
o configure and control OAM
Also associated with configuration management are hardware and
software provisioning and inventory reporting.
4.1. LSP Ownership Handover
MPLS-TP networks can be managed not only by Network Management
Systems (i.e., Management Plane (MP)), but also by Control Plane (CP)
protocols. The utilization of the control plane is not a mandatory
requirement (see MPLS-TP Requirements [2]), but it is often used by
network operators in order to make network configuration and Label
Switched Path (LSP) recovery both faster and simpler.
In networks where both CP and MP are provided, an LSP could be
created by either (CP or MP). The entity creating an LSP owns the
data plane resources comprising that LSP. Only the owner of an LSP
is typically able to modify/delete it. This results in a need for
interaction between the MP and CP to allow either to manage all the
resources of a network.
Network operators might prefer to have full control of the network
resources during the set-up phase and then allow the network to be
automatically maintained by the Control Plane. This can be achieved
by creating LSPs via the Management Plane and subsequently
transferring LSP ownership to the Control Plane. This is referred to
as "ownership handover" RFC 5493 [10]. MP to CP ownership handover
is then considered a requirement where a Control Plane is in use that
supports it. The converse (CP to MP ownership handover) is a feature
that is recommended -- but not required -- for (G)MPLS networks
because it has only minor applications (for example, moving LSPs from
one path to another as a maintenance operation).
The LSP handover procedure has already been standardized for GMPLS
networks, where the signaling protocol used is RSVP-TE (RFC 3209
[1]). The utilization of RSVP-TE enhancements are defined in [5].
MP and CP interworking also includes the exchange of information that
is either requested by the MP, or a notification by the CP as a
consequence of a request from the MP or an automatic action (for
example, a failure occurs or an operation is performed). The CP is
asked to notify the MP in a reliable manner about the status of the
operations it performs and to provide a mechanism to monitor the
status of Control Plane objects (e.g., TE Link status, available
resources), and to log operations related to Control Plane LSP.
Logging is one of the most critical aspects because the MP always
needs to have an accurate history and status of each LSP and all Data
Plane resources involved in it.
5. Performance Management
Performance statistics could overwhelm a Management Network, so it is
important to provide flexible instrumentation that enables control
over the amount of performance data to be collected. Mechanisms for
limiting the quantity of information collected are well known and
deployed in IETF standards (see RFC 2819 (RMON) [8] and RFC 4502
(RMON2) [9]). The details of the performance data collected
(including loss and delay measurement data) are found in the "Network
Management Requirements for MPLS-based Transport Networks" document
[3].
A distinction is made between performance data that is collected on-
demand and data that is collected proactively. The definitions of
on-demand and proactive measurement are provided for OAM in the
"Network Management Requirements for MPLS-based Transport Networks"
document [3].
On-demand measurement provides the operator with the ability to do
performance measurement for maintenance purpose, such as diagnosis or
to provide detailed verification of proactive measurement. It is
used typically on specific LSP service instances for a limited time,
thus limiting its impact on network performance under normal
operations. Therefore, on-demand measurement does not result in
scaling issues.
Proactive measurement is used continuously over time after being
configured with periodicity and storage information. Data collected
from proactive measurement are usually used for verifying the
performance of the service. Proactive performance monitoring has the
potential to overwhelm both the process of collecting performance
data at a network element (for some arbitrary number of service
instances traversing the NE), and the process of reporting this
information to the OS. As a consequence of these considerations,
operators would typically limit the services to which proactive
performance measurement would be applied to a very selective subset
of the services being provided and would limit the reporting of this
information to statistical summaries (as opposed to raw or detailed
performance statistics).
6. Acknowledgements
The authors/editors gratefully acknowledge the thoughtful review,
comments and explanations provided by Diego Caviglia, Bernd Zeuner
and Dan Romascanu.
7. Security Considerations
The ability for the authorized network operator to access EMF
interfaces (Section 2.3) when needed is critical to proper operation.
Therefore, the EMF interfaces need to be protected from denial-of-
service conditions or attack. The EMF interfaces that use or access
private information should be protected from eavesdropping, mis-
configuration, and/or mal-configuration by unauthorized 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 considers private.
Section 4.3 of the "Security Framework for MPLS and GMPLS Networks"
document [14] provides a description of the attacks on the Operation
and Management Plane and also discusses the background necessary to
understand security practices in Internet Service Provider
environments. The security practices described are applicable to
MPLS-TP environments.
8. References
8.1. Normative References
[1] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and
G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels",
RFC 3209, December 2001.
[2] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., and
S. Ueno, "Requirements of an MPLS Transport Profile", RFC 5654,
September 2009.
[3] Lam, K., Mansfield, S., and E. Gray, "Network Management
Requirements for MPLS-based Transport Networks", RFC 5951,
September 2010.
[4] Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. Berger, "A
Framework for MPLS in Transport Networks", RFC 5921, July 2010.
[5] 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.
[6] International Telecommunication Union, "Common equipment
management function requirements", ITU-T Recommendation G.7710/
Y.1701, July 2007.
[7] International Telecommunication Union, "Architecture and
specification of data communication network",
ITU-T Recommendation G.7712/Y.1703, June 2008.
8.2. Informative References
[8] Waldbusser, S., "Remote Network Monitoring Management
Information Base", STD 59, RFC 2819, May 2000.
[9] Waldbusser, S., "Remote Network Monitoring Management
Information Base Version 2", RFC 4502, May 2006.
[10] 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.
[11] International Telecommunication Union, "Principles for a
telecommunication management network", ITU-T Recommendation
M.3010, April 2005.
[12] International Telecommunication Union, "Principles for the
Management of Next Generation Networks", ITU-T Recommendation
M.3060/Y.2401, March 2006.
[13] International Telecommunication Union, "Considerations for a
telecommunication management network", ITU-T Recommendation
M.3013, February 2000.
[14] Fang, L., "Security Framework for MPLS and GMPLS Networks",
RFC 5920, July 2010.
[15] Andersson, L., Helvoort, H., Bonica, R., Romascanu, D., and S.
Mansfield, ""The OAM Acronym Soup"", Work in progress,
June 2010.
Authors' Addresses
Scott Mansfield (editor)
Ericsson
300 Holger Way
San Jose, CA 95134
US
Phone: +1 724 931 9316
Email: scott.mansfield@ericsson.com
Eric Gray (editor)
Ericsson
900 Chelmsford Street
Lowell, MA 01851
US
Phone: +1 978 275 7470
Email: eric.gray@ericsson.com
Hing-Kam Lam (editor)
Alcatel-Lucent
600-700 Mountain Ave
Murray Hill, NJ 07974
US
Phone: +1 908 582 0672
Email: Kam.Lam@alcatel-lucent.com
ISO Plain Language
On this page
§1What This Framework Covers
This document gives the network management framework for the Transport Profile for Multi-Protocol Label Switching, MPLS-TP. The requirements for network management in an MPLS-TP network are in a separate document, and this one explains how network elements and networks that support MPLS-TP can be managed using solutions that satisfy those requirements. The relationship between operations, administration and maintenance, management and the other framework documents is described in the MPLS-TP framework document.
The framework leans on ITU-T management terminology to describe the architecture that could be used for an MPLS-TP management network. The terms come from ITU-T G.7710, G.7712 and M.3013, and the vocabulary is dense. A Communication Channel is a logical channel between network elements that can carry management plane or control plane applications; for MPLS-TP the physical channel supporting it is the Management Communication Channel. The Data Communication Network is the network that carries the layer 1, 2 and 3 traffic of distributed management communications, distributed signalling and other operations communications such as order-wire voice calls and software downloads. The part of it that carries management information is the Management Communication Network, and the part that carries signalling is the Signaling Communication Network. An Equipment Management Function holds the management functions inside a network element. A Local Craft Terminal is an out-of-band device that connects to a network element for management. A Management Application Function is an application process that takes part in system management. The Message Communication Function is the communications process that does information interchange and relay. The Network Element Function is the set of functions needed to manage a network element. The Operations System is a system that performs the functions supporting operations, administration, maintenance and provisioning, including the surveillance and testing functions that support customer access maintenance.
For MPLS-TP the effort, the term OAM means the set of tools made of operation activities that keep the network running, administration activities that track resources and how they are used, and maintenance activities that facilitate repairs and upgrades.
This RFC lays out how an MPLS transport network should be managed: how the management systems are arranged, and what the network equipment has to do about faults, configuration and performance.
§2The Management Architecture
The management of the MPLS-TP network could be based on multi-tiered distributed management systems. Each tier provides a predefined level of network management capability. The lowest tier holds the MPLS-TP network element that provides the transport service, and the Operations System at the element management level. The Management Application Function inside the network elements and the Operations Systems provides the management support, and at each entity it can include agents only, managers only, or both. A function that includes managers can manage an agent in another one. Communication to peer network elements and Operations Systems is provided by the Message Communication Function in each entity, and the user reaches the management of the transport network through a Local Craft Terminal attached to a network element or a workstation attached to the Operations System.
A transport management network may consist of several transport-technology-specific management networks. The MPLS-TP one is called an MT.MN, and it can be partitioned into MPLS-TP Management SubNetworks for scalability, such as geography or load balancing, or for administration, such as operation or ownership. The subnetwork can be connected to other parts of the management network through Local Craft Terminals or Operations Systems. Several addressable MPLS-TP network elements may sit at one physical location, and the link between them is normally provided by the communication channels; within a site they may talk over an intra-site channel or over a LAN.
At the element level, the Equipment Management Function is what a management system uses to manage the network element. It exchanges management information with the element's transport functions across management point reference points, and it may contain functions that reduce the data arriving across those reference points. It includes date and time, the FCAPS functions of fault, configuration, accounting, performance and security management, and control plane functions, and it provides event message processing, data storage and logging. The management agent inside it converts internal management information signals into management application messages and back again, and responds to messages from the Message Communication Function by performing operations on the managed objects in a Management Information Base. The Message Communication Function holds the communications functions for the world outside the element: the date and time source, the management plane, the control plane, the local craft terminal and local alarms.
The management is split into tiers, from the operator's own screen down to the equipment in the street. Each piece of equipment has a small management function inside it, and a communications function that links it to the rest of the management network.
- Management stationWhere the operator works
- Operations SystemThe element management level
- MPLS-TP Management NetworkThe MT.MN, split into management subnetworks
- MPLS-TP Management SubNetworkThe MT.MSN, for scalability or administration
- MPLS-TP network elementThe element that provides the transport service
- Network Element Function
- Transport Plane Atomic Functions
- Equipment Management Function
- Fault, configuration, accounting, performance and security functions
- Management agent and MIB
- Management Application Function
- Message Communication Function
- Date and time interface
- Management plane interface
- Control plane interface
- Local alarm interface
§3Fault Management
A fault is the inability of a function to perform a required action, and does not include an inability caused by preventive maintenance, a lack of external resources, or planned actions. Fault management provides the mechanisms to detect, verify, isolate, notify and recover from the fault.
Supervision is the first step. ITU-T G.7710 lists five basic categories that provide the functionality needed to detect, verify and notify a fault: transmission supervision, quality of service supervision, processing supervision, hardware supervision and environment supervision. Each category provides a set of recommendations to make sure the fault management process is fulfilled.
Validation comes next. ITU-T G.7710 describes a fault cause as a limited interruption of the required function, and it is not reasonable to report every fault cause to maintenance personnel. The validation process turns fault causes, which are events, into failures, which are alarms.
Alarm handling then has to be supported inside the element management system, with mechanisms for severity assignment, alarm reporting control and logging.
A fault is something that stops a function working, but not planned work or running out of something outside. The RFC follows the ITU's three steps: watch for the trouble, sort the real faults from the noise, and then raise and log the alarms that matter.
§4Configuration Management and LSP Ownership
Configuration management provides the mechanisms to provision the MPLS-TP services, set up security for the services and the network elements, provide the destination for fault notifications and performance parameters, and configure and control operations, administration and maintenance. Hardware and software provisioning and inventory reporting are associated with it as well.
One topic gets its own subsection: LSP ownership handover. An MPLS-TP network can be managed not only by network management systems, on the management plane, but also by control plane protocols. Using the control plane is not a mandatory requirement, but operators often do it to make network configuration and LSP recovery both faster and simpler. Where both planes are present, an LSP can be created by either, and the entity that creates it owns the data plane resources that make it up, so normally only the owner can modify or delete it. That creates the need for the management and control planes to interact so that either can manage all the resources of the network.
An operator may prefer full control of the resources during set-up and then let the network maintain itself automatically through the control plane. That is done by creating the LSPs on the management plane and then transferring ownership to the control plane, which is called ownership handover. Management-plane-to-control-plane handover is a requirement where a control plane is in use that supports it. The reverse, control plane to management plane, is recommended but not required for GMPLS networks, because it has only minor applications, such as moving an LSP from one path to another as a maintenance operation. The handover procedure has already been standardised for GMPLS networks, where the signalling protocol is RSVP-TE, and the RSVP-TE enhancements for it are defined elsewhere.
Interworking between the two planes also covers the exchange of information that the management plane requests, and notifications from the control plane as a result of such a request or of an automatic action such as a failure or an operation. The control plane is asked to report the status of the operations it performs in a reliable way, to offer a way of monitoring the status of control plane objects such as TE link status and available resources, and to log the operations it carries out on control plane LSPs. Logging is one of the most critical aspects, because the management plane always needs an accurate history and status of each LSP and of all the data plane resources involved in it.
Two things can build a path: the operator's management system, or the network's own control protocol. Whoever builds it owns it, so the RFC explains how to hand a path over from the operator to the network so that it can repair itself.
§5Performance Management
Performance statistics could overwhelm a management network, so flexible instrumentation is needed that gives control over how much performance data is collected. Mechanisms for limiting the quantity of information collected are well known and deployed in IETF standards, such as RMON and its second version, RMON2. The details of the performance data collected, including loss and delay measurement data, are in the network management requirements document.
The RFC distinguishes performance data collected on demand from data collected proactively. On-demand measurement gives the operator the ability to measure performance for maintenance purposes, such as diagnosis or detailed verification of proactive measurement. It is used typically on specific LSP service instances for a limited time, which limits its impact on network performance during normal operation, and so it does not result in scaling issues. Proactive measurement is used continuously over time after being configured with periodicity and storage information, and the data it collects is usually used for verifying the performance of the service. Proactive monitoring has the potential to overwhelm both the process of collecting data at a network element, for any number of service instances traversing it, and the process of reporting that information to the Operations System. Operators would therefore typically limit proactive measurement to a very selective subset of the services being provided, and limit the reporting to statistical summaries rather than raw or detailed statistics.
Collecting performance data can swamp the management network, so the RFC says to keep the continuous collection to a small set of services and report only summaries, and to use one-off measurements for everything else.
| Aspect | On-demand measurement | Proactive measurement |
|---|---|---|
| When it runs | For a limited time, on specific LSP service instances | Continuously, after being configured with a periodicity and storage information |
| Why it is used | Diagnosis, or detailed verification of proactive measurement | Verifying the performance of the service |
| Scaling | Does not result in scaling issues | Can overwhelm collection and reporting, so operators limit it to a selective subset and report statistical summaries |
§7Security Considerations
The ability for the authorised network operator to reach the equipment management interfaces when needed is critical to proper operation, so those interfaces need protecting from denial-of-service conditions and from attack. Interfaces that use or access private information should be protected from eavesdropping, from mis-configuration and from mal-configuration by unauthorised network elements, systems or users.
Performance of diagnostic functions and path characterisation involves extracting a significant amount of information about network construction that the operator considers private. The security framework for MPLS and GMPLS networks describes the attacks on the operation and management plane and the background needed to understand security practices in internet service provider environments, and the practices it describes apply to MPLS-TP environments.
The management interfaces are worth attacking, so they need protection, and the diagnostic tools reveal more about the network than the operator may want to share.