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Versions: (draft-gray-mpls-tp-nm-req) 00 01 02 03 04 05 06 RFC 5951

     Network Working Group                                  Hing-Kam Lam
     Internet Draft                                       Alcatel-Lucent
     Expires: October, 2009                              Scott Mansfield
     Intended Status: Informational                            Eric Gray
                                                                Ericsson
                                                          April 15, 2009
     
     
                    MPLS TP Network Management Requirements
                        draft-ietf-mpls-tp-nm-req-01.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
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        This Internet-Draft will expire on October 15, 2009.
     
     Abstract
     
        This document specifies the requirements necessary to manage the
        elements and networks that support an MPLS Transport Profile
        (MPLS-TP). This document is a product of a joint International
        Telecommunications Union - Telecommunications Standardization
        Sector (ITU-T) and Internet Engineering Task Force (IETF) effort
        to include a MPLS Transport Profile within the IETF MPLS
        architecture. The requirements are driven by the management
        functionality needs defined by ITU-T for packet transport
        networks.
     
     
     
     
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     Table of Contents
     
     
        1. Introduction................................................3
           1.1. Terminology............................................3
        2. Management Interface Requirements...........................4
        3. Management Communication Channel (MCC) Requirements.........4
        4. Management Communication Network (MCN) Requirements.........5
        5. Fault Management Requirements...............................5
           5.1. Supervision Function...................................5
           5.2. Validation Function....................................6
           5.3. Alarm Handling Function................................7
              5.3.1. Alarm Severity Assignment.........................7
              5.3.2. Alarm Suppression.................................7
              5.3.3. Alarm Reporting Control...........................8
              5.3.4. Alarm Reporting...................................8
        6. Configuration Management Requirements.......................8
           6.1. System Configuration...................................9
           6.2. Control Plane Configuration............................9
           6.3. Path Configuration.....................................9
           6.4. Protection Configuration...............................9
           6.5. OAM Configuration.....................................10
        7. Performance Management Requirements........................10
           7.1. Path Characterization Performance Metrics.............10
           7.2.  Performance Measurement Instrumentation..............12
              7.2.1. Measurement Frequency............................12
              7.2.2. Measurement Scope................................12
        8. Security Management Requirements...........................13
           8.1. Management Communication Channel Security.............13
           8.2. Signaling Communication Channel Security..............13
           8.3. Distributed Denial of Service.........................13
        9. Security Considerations....................................14
        10.  IANA Considerations......................................14
        11. Acknowledgments...........................................14
        12. References................................................14
           12.1. Normative References.................................14
           12.2. Informative References...............................15
        13. Author's Addresses........................................16
        Copyright Statement...........................................16
        Acknowledgment................................................17
        APPENDIX A: Communication Channel (CC) Examples...............18
     
     
     
     
     
     
     
     
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     1. Introduction
     
        This document describes the requirements necessary to manage the
        elements and networks that support an MPLS Transport Profile
        (MPLS-TP).  It leverages the management requirements specified
        in ITU-T G.7710/Y.1701 [1] and RFC 4377 [2]. ITU-T G.7710/Y.1701
        [1] specifies generic management requirements for transport
        (including packet-based and circuit-based) networks. RFC 4377
        specifies the OAM requirements, including OAM-related network
        management requirements, for MPLS networks. This document
        expands on the requirements in [1] and [2] 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 Network Elements.
     
     1.1. Terminology
     
        Although this document is not a protocol specification, 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 [6]
        and are to be interpreted as instructions to protocol designers
        producing solutions that satisfy the requirements set out in
        this document.
     
        MPLS-TP NE: a network element (NE) that supports MPLS-TP
        functions
     
        MPLS-TP network: a network in which MPLS-TP NEs are deployed
     
        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 downloads, etc.).
     
        Management Communication Network (MCN): A DCN supporting
        management plane communication is referred to as a Management
        Communication Network (MCN).
     
        Signaling Communication Network (SCN): A DCN supporting control
        plane communication is referred to as a Signaling Communication
        Network (SCN).
     
     
     
     
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        Communication Channel (CC): a logical channel between network
        elements (NEs) that can be used - e.g. - for management plane
        application or control plane applications. The physical channel
        supporting the CC is technology specific.  See APPENDIX A:
     
        Management Communication Channel (MCC): a CC dedicated for
        management plane communications.
     
        Signaling Communication Channel (SCC): a CC dedicated for
        control plane communications. The SCC may be used for GMPLS/ASON
        signaling and/or other control plane messages (e.g., routing
        messages).
     
        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.
     
     2. Management Interface Requirements
     
        This document does not specify which management interface
        protocol should be 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/XML or SNMP/SMI, and another domain via CORBA/IDL, is
        allowed.
     
        For the management interface to the management system, an MPLS-
        TP NE MAY actively support more than one management protocol in
        any given deployment. For example, an MPLS-TP NE may use one
        protocol for configuration and another for monitoring. The
        protocols to be supported are at the discretion of the operator.
     
     3. Management Communication Channel (MCC) Requirements
     
        An MPLS-TP management network SHOULD support seamless management
        connectivity with remote MPLS-TP domains and NEs as well as with
        termination points located in NEs under control by a third party
        network operator.  See ITU-T G.8601 [8] for example scenarios in
        multi-carrier multi-transport-technology environments.
     
        For management purpose, every MPLS-TP NE MUST connect to an OS
        either directly or indirectly via another MPLS-TP NE. When an
        MPLS-TP NE is connected indirectly to an OS, an MCC MUST be
        supported between the MPLS-TP NE and the other MPLS-TP NE.
     
     
     
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     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 MPLS-TP NEs
        with management systems, NEs with NEs, and management systems
        with management systems. Transport DCN architecture and
        requirements are specified in ITU-T G.7712/Y.1703 [7], including
        network layer protocols and their interworking.
     
        As a practical requirement, MCN connections require addressing.
        See the section on addressing in [13] for further information.
     
        In order to have the MCN operate properly, a number of
        management functions for the MCN are required, including:
     
          . Retrieval of DCN network parameters to ensure compatible
             functioning, e.g. packet size, timeouts, quality of
             service, window size, etc.;
     
          . Establishment of message routing between DCN nodes;
     
          . Management of DCN network addresses;
     
          . Retrieval of operational status of the DCN at a given node;
     
          . Capability to enable/disable access to the DCN.
     
     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
        environment.
     
     5.1. Supervision Function
     
        The supervision function analyses 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.
     
        The MPLS-TP NE MUST support supervision of the OAM mechanisms
        that are deployed for supporting the OAM requirements defined in
        [3].
     
     
     
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        The MPLS-TP NE MUST support the following transmission
        supervision functions:
     
          . Supervision of looping check 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);
     
          . Supervision of the detection of failure in the sequence of
            a protocol exchange (e.g. automatic protection switching
            protocol);
     
        The MPLS-TP NE transmission-related supervision mechanisms MUST
        support the flexibility to be configured to perform on-demand or
        proactively.
     
        The MPLS-TP NE MUST support supervision for software processing
        e.g., processing fault, storage capacity problem, version
        mismatch, corrupted data, out of memory, etc.
     
        The MPLS-TP NE MUST support hardware-related supervision for
        interchangeable and non-interchangeable units, cable, and power
        problem.
     
        The MPLS-TP NE SHOULD support environment-related supervision
        for temperature, humidity, etc.
     
     5.2. Validation Function
     
        Validation is concerned with the integration of Fault Causes
        into Failures. A Fault Cause indicates a limited interruption of
        the required transport function. A Fault Cause is not reported
        to maintenance personnel because it could exist only for a very
        short time. Note that some of these events however are summed up
        in the Performance Monitoring process, and when this sum exceeds
        a certain value, a Threshold 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.
     
        The MPLS-TP NE MUST perform persistency checks on fault causes
        before it declares a fault cause a failure.
     
     
     
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        A transmission failure SHALL be declared if the fault cause
        persists continuously for a configurable time (Time-D). The
        failure SHALL be cleared if the fault cause is absent
        continuously for a configurable time (Time-C).  Typically the
        default time values would 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 [1].
     
        The failure declaration and clearing MUST be time stamped. The
        time-stamp SHALL 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
        persistency function.
     
     5.3. Alarm Handling Function
     
     5.3.1. Alarm Severity Assignment
     
        Failures might be categorized to indicate the severity or
        urgency of the fault.
     
        An MPLS-TP NE SHOULD support the flexibility of assignment of
        severity (e.g., Critical, Major, Minor, Warning) by the
        management system.
     
        See G.7710 [1] for more description about alarm severity
        assignment.
     
     5.3.2. Alarm Suppression
     
        Alarms may be generated from many sources, including OAM, device
        status, etc.
     
        An MPLS-TP NE MUST provide alarm suppression functionality that
        prevents the generation of superfluous alarms.
     
        Examples of alarm suppression mechanisms include simply
        discarding the alarms (or not generating them in the first
        place), or aggregating the alarms together, thereby greatly
        reducing the number of alarm notifications to be emitted.
     
     
     
     
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        Note: An MPLS-TP NE supporting the inter-working of one or more
        networking technologies (e.g., Ethernet, SDH/SONET, MPLS) with
        MPLS-TP needs to translate an MPLS-TP fault into an existing
        transport technology failure condition for reporting to the
        management system.
     
        See RFC 4377 [2] for more description.
     
     5.3.3. Alarm Reporting Control
     
        Alarm Reporting Control (ARC) supports an automatic in-service
        provisioning capability. Alarm reporting MAY be turned off on a
        per-managed entity (e.g., LSP) basis 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.
     
        An MPLS-TP NE SHOULD support the Alarm Reporting Control
        function for controlling the reporting of alarm conditions.
     
        See G.7710 [1] and RFC 3878 [9] for more description of ARC.
     
     5.3.4. 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.
     
        An MPLS-TP NE MUST support local reporting of alarms.
     
        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.
     
     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
     
     
     
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        protection paths), and configuration of required path
        integrity/connectivity and performance monitoring (i.e. - OAM).
     
     6.1. System Configuration
     
        The MPLS-TP NE MUST support the configuration requirements
        specified in G.7710 [1] for hardware, software, and date/time.
     
     6.2. Control Plane Configuration
     
        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 might be provided along with progress in defining
        the MPLS-TP control plane in appropriate specifications.
     
     6.3. Path Configuration
     
        The MPLS-TP NE MUST support the capability of configuring
        required path performance characteristic thresholds (e.g. - Loss
        Measurement [LM], Delay Measurement [DM] thresholds).
     
        The MPLS-TP NE MUST support the capability of configuring
        required LSPs as follows:
     
            . configure LSP indentifier and/or other information
               necessary to retrieve LSP status information.
     
     6.4. Protection Configuration
     
        The MPLS-TP NE MUST support the capability of configuring
        required path protection as follows:
     
            . Designate specifically identified LSPs as working or
               protection LSPs;
            . define associations of working and protection paths;
            . operate/release manual protection switching;
            . operate/release force protection switching;
            . operate/release protection lockout;
            . set/retrieve Automatic Protection Switching (APS)
               parameters, including -
                 . Wait to Restore time,
                 . Protection Switching threshold information.
     
     
     
     
     
     
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     6.5. OAM Configuration
     
        The MPLS-TP NE MUST provide the capability to configure the OAM
        entities and functions specified in [3].
     
        The MPLS-TP NE MUST support the capability to choose which OAM
        functions to use and which maintenance entity to apply them.
     
        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
        point-to-multipoint) connections.
     
        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.
     
        The MPLS-TP NE MUST have the flexibility to configure OAM
        parameters to meet their specific operational requirements, such
        as whether (1) one-time on-demand immediately or (2) one-time
        on-demand pre-scheduled or (3) on-demand periodically based on a
        specified schedule or (4) proactive on-going.
     
        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 to evaluate and report
        upon the behavior of the equipment, NE, and network for the
        purpose of Maintenance, Bring-into-service, Quality of service,
        and Performance monitoring for signal degradation. ITU-T
        Recommendation G.7710 [1] provides transport performance
        monitoring requirements for packet-switched and circuit-switched
        transport networks with the objective of providing coherent and
        consistent interpretation of the network behavior, in particular
        for hybrid network which consists of multiple transport
        technologies. The performance management requirements specified
        in this document are driven by such an objective.
     
     7.1. Path Characterization Performance Metrics
     
        The MPLS-TP NE MUST support collection of loss measurement (LM)
        so that they can be used to detect performance degradation.
     
     
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        The MPLS-TP NE MUST support collection of delay measurement (DM)
        so that they can be used to detect performance degradation.
     
        The MPLS-TP NE MUST support reporting of Performance degradation
        via fault management for corrective actions (e.g. protection
        switching).
     
        The MPLS-TP NE MUST support collection of loss ratio measurement
        so that they can be used to determine Severely Errored Second
        (SES).
     
        A SES is declared for a one second interval when the ratio of
        lost packets to total transmitted packets in that one second
        interval exceeds a predetermined threshold.
     
        The packet lost threshold for declaring SES MUST be
        configurable.
     
        The number of SESs MUST be collected per configurable intervals
        (e.g. 15-minute and 24-hour).
     
        The MPLS-TP NE MUST support collection of SES measurement so
        that they can be used to determine service unavailable time.
     
        A period of unavailable time (UAT) begins at the onset of 10
        consecutive SES events. These 10 seconds are considered to be
        part of unavailable time. A new period of available time begins
        at the onset of 10 consecutive non-SES events. These 10 seconds
        are considered to be part of available time.
     
        The MPLS-TP NE MUST support collection of Unavailable Seconds
        (UAS) so that they can be used to determine service
        availability.
     
        The number of UAS MUST be collected per configurable intervals
        (e.g. 15-minute and 24-hour).
     
        SES and UAS history (the number of readings to be retained and
        available) is as defined in ITU and ANSI documents associated
        with specific transport technologies (for instance, ITU-T
        G.7710, and ANSI T1.231-2003 [T1.231.01-2003 for DSL,.02 for
        DS1,.03 for DS3 and T1.231.04-2003 for SONET] - see [1] and [14]
        respectively), however these are fairly consistently defined as
        follows:
     
          - Current and previous 1-day statistics
     
     
     
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          - Current and 16 recent 15-minute statistics (ITU-T)
     
          - Current, previous and 31 recent 15-minute statistics (ANSI)
     
        Note that - worst case (ANSI) requires 2 copies of 1-day
        statistics (current and previous) and 33 copies of 15-minute
        statistics (current, previous and 31 recent).
     
     7.2. Performance Measurement Instrumentation
     
     7.2.1. Measurement Frequency
     
        The performance measurement mechanisms MUST support the
        flexibility to be configured to operate on-demand or proactively
        (i.e. continuously over a period of time).
     
     7.2.2. Measurement Scope
     
        On measurement of packet loss and loss ratio:
     
          - For bidirectional (both co-routed and associated) P2P
             connections -
     
                 . on-demand measurement of single-ended packet loss,
                    and loss ratio, measurement are required;
     
                 . proactive measurement of packet loss, and loss
                    ratio, measurement for each direction are required.
     
        Note: for associated bidirectional P2P connections, this data
        can only be measured at end-points.
     
          - For unidirectional (P2P and P2MP) connection, proactive
             measurement of packet loss, and loss ratio, are required.
     
        On Delay measurement:
     
          - For unidirectional (P2P and P2MP) connection, on-demand
             measurement of delay measurement is required.
     
          - For co-routed bidirectional (P2P) connection, on-demand
             measurement of one-way and two-way delay are required.
     
          - For associated bidirectional (P2P) connection, on-demand
             measurement of one-way delay is required.
     
     
     
     
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     8. Security Management Requirements
     
        The MPLS-TP NE MUST support secure management and control
        planes.
     
     8.1. Management Communication Channel Security
     
        Secure channels MUST be provided 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.  The MCC MUST support application
        protocols that provide confidentiality and data integrity
        protection.
     
        If management communication security is provided, the MPLS-TP NE
        MUST support the following:
     
          - Use of open cryptographic algorithms (See RFC 3871 [5])
     
          - Authentication - allow management connectivity only from
             authenticated entities.
     
          - Authorization - allow management activity originated by an
             authorized entity, using (for example) an Access Control
             List (ACL).
     
        Port Access Control - allow management activity received on an
        authorized (management) port.
     
     8.2.Signaling Communication Channel Security
     
        Security considerations for the SCC are similar to the
        considerations driving the 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 plane specifications. Management of the
        control plane security must also be defined at that time.
     
     8.3. Distributed Denial of Service
     
        Denial of Service (DoS) attack is an attack which 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)
     
     
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        distributed attack sources. It is possible to lessen the impact
        and potential for DDOS by using secure protocols, turning off
        unnecessary processes, logging and monitoring, and ingress
        filtering.  RFC 4732 [4] provides background on DOS in the
        context of the Internet.
     
     9. Security Considerations
     
        Section 8 includes a set of security requirements that apply to
        MPLS-TP network management.
     
        Solutions MUST provide mechanisms to prevent unauthorized and/or
        unauthenticated access to 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 MAY consider
        private.
     
     10. IANA Considerations
     
        There are no IANA actions associated with this document.
     
     11. Acknowledgments
     
        The authors/editors gratefully acknowledge the thoughtful
        review, comments and explanations provided by Adrian Farrel,
        Andrea Maria Mazzini, Ben Niven-Jenkins, Bernd Zeuner, Diego
        Caviglia, Dieter Beller, He Jia, Leo Xiao, Maarten Vissers, Neil
        Harrison and Rolf Winter.
     
     12. References
     
     12.1. Normative References
     
        [1]   ITU-T Recommendation G.7710/Y.1701, "Common equipment
              management function requirements", July, 2007.
     
        [2]   Nadeau, T., et al, "Operations and Management (OAM)
              Requirements for Multi-Protocol Label Switched (MPLS)
              Networks", RFC 4377, February 2006.
     
        [3]   Vigoureus, M., et al, "Requirements for OAM in MPLS
              Transport Networks", work in progress.
     
     
     
     
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        [4]   Handley, M., et al, "Internet Denial-of-Service
              Considerations", RFC 4732, November 2006.
     
        [5]   Jones, G., "Operational Security Requirements for Large
              Internet Service Provider (ISP) IP Network
              Infrastructure", RFC 3871, September 2004.
     
        [6]   Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", RFC 2119, March 1997.
     
        [7]   ITU-T Recommendation G.7712/Y.1703, "Architecture and
              Specification of Data Communication Network", June 2008.
     
        [8]   ITU-T Recommendation G.8601, "Architecture of service
              management in multi bearer, multi carrier environment",
              June 2006.
     
        [9]   Lam, H., et al, "Alarm Reporting Control Management
              Information Base (MIB)", RFC 3878, September 2004.
     
     12.2. Informative References
     
        [10]  Chisholm, S. and D. Romascanu, "Alarm Management
              Information Base (MIB)", RFC 3877, September 2004.
     
        [11]  ITU-T Recommendation M.20, "Maintenance Philosophy for
              Telecommunication Networks", October 1992.
     
        [12]  Telcordia, "Network Maintenance: Network Element and
              Transport Surveillance Messages" (GR-833-CORE), Issue 5,
              August 2004.
     
        [13]  Bocci, M. et al, "A Framework for MPLS in Transport
              Networks", Work in Progress, November 27, 2008.
     
        [14]  ANSI T1.231-2003, "Layer 1 In-Service Transmission
              Performance Monitoring", American National Standards
              Institute, 2003.
     
        [15]  Vigoureux, M. et al, "MPLS Generic Associated Channel",
              draft-ietf-mpls-tp-gach-gal, work in progress.
     
     
     
     
     
     
     
     
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     13. Author's Addresses
     
        Editors:
     
        Scott Mansfield
        Ericsson
        5000 Ericsson Drive
        Warrendale, PA, 15086
        Phone: +1 724 742 6726
        EMail: Scott.Mansfield@Ericsson.com
     
        Hing-Kam (Kam) Lam
        Alcatel-Lucent
        600-700 Mountain Ave
        Murray Hill, NJ, 07974
        Phone: +1 908 582 0672
        Email: hklam@Alcatel-Lucent.com
     
        Eric Gray
        Ericsson
        900 Chelmsford Street
        Lowell, MA, 01851
        Phone: +1 978 275 7470
        Email: Eric.Gray@Ericsson.com
     
        Author(s):
     
        Contributor(s):
     
        Adrian Farrel
        Old Dog Consulting
        Email: adrian@olddog.co.uk
     
     Copyright Statement
     
        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.
     
     
     
     
     
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     Acknowledgment
     
        Funding for the RFC Editor function is currently provided by the
        Internet Society.
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
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     APPENDIX A: Communication Channel (CC) Examples
     
        A CC may be realized in a number of ways.
     
        1. The CC may 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 may be interconnected in two distinct physical
        networks: the transport network and the DCN.
     
        This is a "physically distinct out-of-band CC".
     
        2. The CC may be provided by a link in the transport network
        that is terminated at the ends of the DCC and which is capable
        of encapsulating and terminating packets of the management
        protocols.  For example, in MPLS-TP an 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 CC."
     
        3. The CC may 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 interface.
     
        This is a "shared interface out-of-band CC".
     
        4. The CC may 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 CC. 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 CC".
     
        This alternative is not available in MPLS-TP because there is no
        overhead available.
     
        5. The CC may provided by a dedicated channel associated with
        the data link. For example, the generic associated label (GAL)
        [15] may be used to label DCC traffic being exchanged on a data
     
     
     
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        link between adjacent transport nodes, potentially in the
        absence of any data LSP between those nodes.
     
        This is a "data link associated CC".
     
        It is very similar to case 2, and by its nature can only span a
        single hop in the transport network.
     
        6. The CC may be provided by a dedicated channel associated with
        a data channel. For example, in MPLS-TP the GAL [15] may be
        imposed under the top label in the label stack for an MPLS-TP
        LSP to create a channel associated with the LSP that may carry
        management traffic. This CC 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 CC".
     
        7. The CC may 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 is able to demultiplex the
        management and user traffic. Such might be possible in MPLS-TP
        if the MPLS-TP LSP was carrying IP user traffic.
     
        This is an "in-band CC".
     
        These realizations may 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 may be
        realized by the same DCN or as separate networks. In practice,
        that means that, between any pair of nodes, the MCC and SCC may
        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
     
     
     
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        pair of adjacent nodes may 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 may be deployed for DCN resilience or
        load sharing. Links may 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 should be noted that the DCN may 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 may substantially simplify the topology of the
        DCN and improve its resilience, but does increase the complexity
        of operating the DCN.
     
        See also RFC 3877 [10], ITU-T M.20 [11], and Telcordia document
        GR-833-CORE [12] for further information.
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
     
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