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Versions: (draft-vigoureux-mpls-tp-oam-requirements) 00 01 02 03 04 05 06 RFC 5860

MPLS Working Group                                M. Vigoureux (Editor)
Internet Draft                                           Alcatel-Lucent
Intended status: Informational
Expires: May 2009                                      D. Ward (Editor)
                                                    Cisco Systems, Inc.

                                                      M. Betts (Editor)
                                                        Nortel Networks

                                                      November 28, 2008



              Requirements for OAM in MPLS Transport Networks
                  draft-ietf-mpls-tp-oam-requirements-00


Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.

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   This Internet-Draft will expire on May 28, 2009.

Abstract

   This document lists the requirements for Operations, Administration
   and Maintenance functionality in MPLS networks that are used for
   packet transport services and network operations.

   These requirements are derived from the set of requirements specified
   by ITU-T and first published in the ITU-T Supplement Y.Sup4 [5].




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Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [1].

Table of Contents

   1. Introduction...................................................2
      1.1. Terminology...............................................3
      1.2. Definitions...............................................3
      1.3. Context and Motivations...................................4
   2. OAM Requirements...............................................5
      2.1. Architectural Requirements................................5
      2.2. Functional Requirements...................................7
         2.2.1. General requirements.................................8
         2.2.2. Connectivity and Continuity Verification.............8
         2.2.3. Client Failure Indication............................8
         2.2.4. Remote Defect Indication.............................8
         2.2.5. Alarm Suppression....................................8
         2.2.6. Packet Loss..........................................9
         2.2.7. Delay Measurement....................................9
         2.2.8. Route Determination..................................9
         2.2.9. Diagnostic..........................................10
      2.3. Operational Requirements.................................10
      2.4. Performance Requirements.................................11
   3. Security Considerations.......................................11
   4. Congestion Considerations.....................................12
   5. IANA Considerations...........................................12
   6. Acknowledgments...............................................12
   7. References....................................................13
      7.1. Normative References.....................................13
      7.2. Informative References...................................13
   Authors' Addresses...............................................13
   Contributing Authors' Addresses..................................14
   Intellectual Property Statement..................................15
   Disclaimer of Validity...........................................16
   Copyright Statement..............................................17


1. Introduction

   This document lists the requirements for Operations, Administration
   and Maintenance functionality in MPLS networks that are used for
   packet transport services and network operations.




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1.1. Terminology

   AC    Attachment Circuit

   CSF   Client Signal Fail

   FCAPS Fault, Configuration, Accounting, Performance, Security

   LER   Label Edge Router

   LSP   Label Switched Path

   LSR   Label Switching Router

   ME    Maintenance Entity

   MEP   Maintenance End Point

   MIP   Maintenance Intermediate Point

   MP    Maintenance Point

   MS-PW Multi Segment Pseudowire

   OAM   Operations, Administration and Maintenance

   PE    Provider Edge

   PSN   Packet Switched Network

   PW    Pseudowire

   SLA   Service Level Agreement

   SS-PW Single Segment Pseudowire

   S-PE  PW Switching Provider Edge

   T-PE  PW Terminating Provider Edge

   TCME  Tandem Connection Maintenance Entity

1.2. Definitions

   In this document we refer to a fault as the inability of a function
   to perform a required action. This does not include an inability due



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   to preventive maintenance, lack of external resources, or planned
   actions. See also ITU-T G.806 [3].

   In this document we refer to a defect as the situation for which
   density of anomalies has reached a level where the ability to perform
   a required function has been interrupted. See also ITU-T G.806 [3].

   In this document, we refer to MPLS Transport Profile (MPLS-TP) as the
   set of MPLS functions used to support packet transport services and
   network operations.

   In this document we refer to a MPLS Section as a network segment
   between two LSRs that are immediately adjacent at the MPLS layer.

   For definitions of OAM functional components such as Maintenance
   Point, Maintenance End Point and Maintenance Intermediate Point,
   please refer to [7].
   Additional definitions can also be found in [8].

1.3. Context and Motivations

   Important attributes of MPLS-TP are that

   o  it is able to function regardless of which client signals are
      using its connectivity service or over which transmission media it
      is running. The client, transport network and server layers are,
      from a functional point of view, independent layer networks. That
      is, demarcation points exist between MPLS-TP and the client layer,
      and between MPLS-TP and the underlying server layer.

   o  it provides means to commit to Service Level Agreements (SLAs)
      negotiated with customers, as well as means to monitor compliance
      with these SLAs.

   o  it is consistent with existing transport network OAM models.

   In the context of MPLS-TP, the rationale for OAM mechanisms are
   twofold as they can serve:

   o  as a network-oriented mechanism (used by a transport network
      operator) to monitor his network infrastructure and to implement
      internal mechanisms in order to enhance the general behaviour and
      the level of performance of his network (e.g. protection mechanism
      in case of node or link failure). For example fault localization
      is typically associated to this use case.




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   o  as a service-oriented mechanism (used by a transport service
      provider) to monitor his offered services to end customers in
      order to be able to react rapidly in case of a problem and to be
      able to verify some of the SLA parameters (i.e. performance
      monitoring) negotiated with the end customer. Note that a
      transport service could be provided over several networks or
      administrative domains that may not be all owned and managed by
      the same transport service provider.

   More generally, OAM is an important and fundamental functionality in
   transport networks as it contributes to:

   o  the reduction of operational complexity and costs, by allowing
      efficient and automatic detection, localisation, handling, and
      diagnosis of defects, and by minimizing service interruptions and
      operational repair times.

   o  the enhancement of network availability, by ensuring that defects,
      for example resulting in misdirected customer traffic are
      detected, diagnosed and dealt with before a customer reports the
      problem.

   o  meet service and performance objectives, by running OAM
      functionality which allows SLA verification in a multi-maintenance
      domain environment and allows the determination of service
      degradation due to, for example, packet delay or packet loss.

   This is achieved through the support of FCAPS functionality, as
   described in ITU-T M.3400 [2], itself relying on OAM related
   information.

2. OAM Requirements

   This section lists the requirements by which the OAM functionality of
   MPLS-TP should abide. Some requirements for this application are
   similar to some of those listed in RFC 4377 [6].

   The requirements listed below may be met by one or more OAM
   protocols, the definition or selection of these protocols is outside
   the scope of this document. However, the specified solution MUST
   inter-work with the existing MPLS and PW OAM protocols.

2.1. Architectural Requirements

   OAM functions SHOULD be independent of the underlying tunnelling or
   point-to-point technology or transmission media.



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   OAM functions SHOULD be independent of the service a pseudowire may
   emulate.

   The set of OAM functions operated on each Maintenance Entity SHOULD
   be independent one from another.
   Note that independence should not be understood here in terms of
   isolation but in terms of separate running processes. There should be
   one OAM process running per Maintenance Entity but different OAM
   running processes could interact (e.g. alarm summarization).

   OAM functionality MAY be deployed in a variety of environments. In
   some of these IP routing and forwarding capabilities are inherently
   present (e.g. IP/MPLS) and the OAM functionality MUST also support
   their use. Other deployment scenarios exist where IP routing and
   forwarding capabilities are not necessarily present (e.g. MPLS-TP).
   In these latter cases, the operation of OAM functions MUST NOT rely
   on IP routing and forwarding capabilities. Further, it is REQUIRED by
   this document that OAM interoperability is achieved across these
   environments. It is also REQUIRED by this document that the two above
   requirements are still met and still hold when interoperability is
   achieved.

   Furthermore, in case OAM packets need to incorporate identification
   information of source and/or destination nodes, an IP addressing
   structure MUST be supported.

   When MPLS-TP is run with IP routing and forwarding capabilities, all
   existing IP/MPLS OAM functionality (e.g. LSP-Ping, BFD and VCCV) MUST
   be able to operate seamlessly.

   OAM functions MUST operate and be configurable even in the absence of
   a control plane. Conversely, OAM functions SHOULD be configurable as
   part of connectivity (LSP or PW) management. Note that means for
   configuring OAM functions and for connectivity management are outside
   the scope of this document.

   The service emulated by a single segment or a multi-segment
   pseudowire may span multiple domains. A LSP may also span multiple
   domains. It MUST be possible to perform OAM functions on a per domain
   basis and across multiple domains. More generally it MUST be possible
   to perform OAM functions between any two switching elements of a PW
   or of a LSP. This is referred to as segment (or tandem connection)
   monitoring (see [7]). Furthermore, in case of a fault or defect on
   the service, means MUST be available for the service provider to be
   informed of the fault even if the fault is located outside of his
   domain.



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   OAM functions operate in the data plane. OAM packets MUST run in-
   band. That is, OAM packets for a specific Maintenance Entity MUST
   follow the exact same data path as user traffic of that Maintenance
   Entity. This is known as fate sharing.

   It MUST be possible to discriminate data traffic from OAM packets.
   This includes a means to differentiate OAM packets from user traffic
   as well as the capability to apply specific treatment, to OAM
   packets, at the MIPs or MEPs targeted by these OAM packets.

   As part of the design of OAM mechanisms for MPLS-TP, a mechanism that
   enables the realization of a channel for general purpose signalling,
   e.g. for control, management and OAM information, associated with the
   data plane paths, MUST be provided. Such mechanism SHOULD support the
   operation of existing IP/MPLS OAM.

   OAM functions MUST be able to be used for PWs, LSPs and Sections.
   Furthermore, since LSPs MAY be stacked, OAM functions MUST be able to
   run on each LSP, regardless of the label stack depth.

2.2. Functional Requirements

   Hereafter are listed the required functions composing the MPLS-TP OAM
   tool-set. The list may not be exhaustive and as such the OAM
   mechanisms developed in support of the identified requirements SHALL
   be extensible and thus SHALL NOT preclude the definition of
   additional OAM functions in the future. Furthermore, the design of
   OAM mechanisms for MPLS-TP MUST allow the ability to support vendor
   specific and experimental OAM functions. Vendor specific and
   experimental OAM functions MUST be disabled by default and explicitly
   enabled by a service provider or network operator, between nodes that
   support them.

   Moreover, the use of OAM functions SHOULD be optional for the service
   provider or network operator. A network operator or service provider
   SHOULD be able to choose which OAM functions to use and which
   Maintenance Entities to apply them to.

   Note that the functions listed below can serve the purpose of fault
   and/or performance management. For example, connectivity verification
   can be used for fault management application by detecting failure
   conditions, but may also be used for performance management
   application through its contribution to the evaluation of performance
   metrics (e.g. unavailability time). Nevertheless, it is outside the
   scope of this document to specify which function should be used for
   which application.



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2.2.1. General requirements

   If a defect or fault occurs, mechanisms MUST be provided to detect
   it, diagnose it, localize it, and notify the appropriate entities.
   Corrective actions SHOULD be taken according to the type of defect or
   fault.

   In the case of the PW Maintenance Entity, OAM mechanisms SHOULD be
   provided to ensure that customers do not have to detect faults. The
   OAM functions SHOULD allow the service provider to automatically
   detect and notify the faults associated with a PW Maintenance Entity.

2.2.2. Connectivity and Continuity Verification

   The MPLS-TP OAM tool-set MUST provide a function to enable service
   providers to detect loss of continuity but also mis-connectivity
   between two points of a Maintenance Entity.

2.2.3. Client Failure Indication

   The MPLS-TP OAM tool-set MUST provide a function to enable a MEP to
   propagate a client failure indication to its peer MEP when alarm
   suppression in the client layer is not supported.

   In cases where the OAM of the native service of an AC or a PW type
   does not provide mechanisms to propagate failure condition
   information, while a downstream indication of such state is needed,
   MPLS-TP OAM SHOULD provide mechanisms for propagating AC failures and
   their clearance across a MPLS-TP domain.

2.2.4. Remote Defect Indication

   The MPLS-TP OAM tool-set MUST provide a function to enable a MEP to
   notify its peer MEP of the detection of a defect on a bi-directional
   connection between them.

2.2.5. Alarm Suppression

   The MPLS-TP OAM tool-set MUST provide a function to enable a server
   layer MEP to notify a failure condition or an administrative locking
   to its client layer MEP(s) in order to suppress alarms that may be
   generated by maintenance domains of the client layer as a result of
   the failure condition or of the administrative locking in the server
   layer.





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   The MPLS-TP OAM tool-set MUST allow the client layer to differentiate
   between a defect condition and an administrative locking action at
   the server layer ME.

   The server layer MEP and the client layer MEPs MAY reside on the same
   node or on different nodes. A mechanism MUST be provided for both
   cases.

   An alarm suppression and summarization mechanism MUST be provided.
   For example, a fault detected at the LSP level MUST NOT trigger
   various alarms at the PW level.

2.2.6. Packet Loss

   The MPLS-TP OAM tool-set MUST provide a function to enable service
   providers to measure packet loss ratio between a pair of MEPs. Packet
   loss ratio is the ratio of the user-plane packets not delivered to
   the total number of user-plane packets transmitted during a defined
   time interval. The number of user-plane packets not delivered is the
   difference between the number of user-plane packets transmitted by
   the source node and the number of user-plane packets received at the
   destination node.

2.2.7. Delay Measurement

   The MPLS-TP OAM tool-set MUST provide a function to enable service
   providers to measure the one-way or two-way delay of a packet
   transmission between a pair of MEPs. Where,

   o  One-way packet delay is the time elapsed from the start of
      transmission of the first bit of the packet by a source node until
      the reception of the last bit of that packet by the destination
      node.

   o  Two-way packet delay is the time elapsed from the start of
      transmission of the first bit of the packet by a source node until
      the reception of the last bit of the loop-backed packet by the
      same source node, when the loopback is performed at the packet's
      destination node.

2.2.8. Route Determination

   The MPLS-TP OAM tool-set MUST provide a function to enable service
   providers to determine the route of a connection across the MPLS
   transport network.




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2.2.9. Diagnostic

   The MPLS-TP OAM tool-set MUST provide a function to enable service
   providers to verify bandwidth throughput (and other diagnostic tests)
   between a pair of MEPs.

2.3. Operational Requirements

   OAM functions such as connectivity and continuity verification MUST
   NOT rely on user traffic. Dedicated OAM flows SHOULD be used to
   detect connectivity and continuity defects. See also ITU-T G.806 .
   [3].
   This document does not mandate the use of a particular OAM function,
   however, it is RECOMMENDED that connectivity and continuity
   verification is performed on every Maintenance Entity in order to
   reliably detect connectivity defects.

   OAM functions MUST be applicable to bidirectional point-to-point
   connections, and a subset of these OAM functions MUST be applicable
   to unidirectional point-to-point and point-to-multipoint connections.
   This subset is based on the nature of both the OAM functions and the
   connections to which they can apply.

   The following table describes how, on which Maintenance Entity and
   between which points of the Maintenance Entity SHOULD the required
   OAM functions be applied. In these tables, MEP stands for monitoring
   from MEP to MEP, MIP stands for monitoring from MEP to MIP, U stands
   for unidirectional, B stands for bidirectional. Crosses (x) indicate
   the way the considered function should be applied, numbers indicate
   the way the considered function should be applied while pointing to a
   footnote providing additional details.


















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                          +-------------------------------------------+
                          |      on-demand      |      proactive      |
                          |---------------------+----------+----------|
                          |    MEP   |   MIP    |    MEP   |   MIP    |
                          |----------+----------+----------+----------|
                          | P2P |P2MP| P2P |P2MP| P2P |P2MP| P2P |P2MP|
                          |-----+----+----------+----------+-----+----|
                          |U |B | U  |U |B | U  |U |B | U  |U |B | U  |
   +----------------------+--+--+----+--+--+----+--+--+----+--+--+----|
   | cc verification      |  |x |    |  |x |    |x |x | x  |  |  |    |
   |----------------------+--+--+----+--+--+----+--+--+----+--+--+----|
   | client fail. indic.  |  |  |    |  |  |    |  |x |    |  |  |    |
   |----------------------+--+--+----+--+--+----+--+--+----+--+--+----|
   | remote defect indic. |  |  |    |  |  |    |  |x |    |  |  |    |
   |----------------------+--+--+----+--+--+----+--+--+----+--+--+----|
   | alarm suppression    |  |  |    |  |  |    |x |x | x  |  |  |    |
   |----------------------+--+--+----+--+--+----+--+--+----+--+--+----|
   | packet loss measure  |  |1 |    |  |  |    |x |2 | x  |  |  |    |
   |----------------------+--+--+----+--+--+----+--+--+----+--+--+----|
   | delay measurement    |x |3 | x  |  |  |    |  |  |    |  |  |    |
   |----------------------+--+--+----+--+--+----+--+--+----+--+--+----|
   | route determination  |  |x |    |  |x |    |  |  |    |  |  |    |
   |----------------------+--+--+----+--+--+----+--+--+----+--+--+----|
   | diagnostic           |x |x | x  |  |  |    |  |  |    |  |  |    |
   +----------------------+-------------------------------------------+
   1: single-ended packet loss measurements

   2: in both directions of the bi-directional connection

   3: one-way and two-way packet delay measurements

         Table 1 : OAM functions and their applicability scope



2.4. Performance Requirements

   OAM functions SHOULD continue to meet their objectives regardless of
   congestion conditions. See also ITU-T Y.1541 [4].

   Additional requirements will be incorporated in a future revision of
   this document.

3. Security Considerations

   Mechanisms SHOULD be provided to ensure that unauthorized access is
   prevented from triggering any OAM function.


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   OAM messages MAY be authenticated.

   An OAM packet for a Maintenance Entity MUST NOT leak out of the ME,
   i.e. go beyond the terminating MEP.

4. Congestion Considerations

   A mechanism (e.g. rate limiting) MUST be provided to prevent OAM
   messages from causing congestion in the PSN.

5. IANA Considerations

   There are no IANA actions required by this draft.

6. Acknowledgments

   The authors would like to thank all members of the teams (the Joint
   Working Team, the MPLS Interoperability Design Team in IETF and the
   T-MPLS Ad Hoc Group in ITU-T) involved in the definition and
   specification of MPLS Transport Profile.





























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7. References

7.1. Normative References

   [1]   Bradner, S., "Key words for use in RFCs to Indicate Requirement
         Levels", BCP 14, RFC 2119, March 1997

   [2]   ITU-T Recommendation M.3400 (2000), TMN management functions

   [3]   ITU-T Recommendation G.806 (2006), Characteristics of transport
         equipment - Description methodology and generic functionality

   [4]   ITU-T Recommendation Y.1541 (2006), Network performance
         objectives for IP-based services

   [5]   ITU-T Supplement Y.Sup4 (2008), Transport Requirements for T-
         MPLS OAM and considerations for the application of IETF MPLS
         Technology

7.2. Informative References

   [6]   Nadeau, T., et al., "Operations and Management (OAM)
         Requirements for Multi-Protocol Label Switched (MPLS)
         Networks", RFC 4377, February 2006

   [7]   Busi, I., Niven-Jenkins, B., "MPLS-TP OAM Framework and
         Overview", draft-busi-mpls-tp-oam-framework, October 2008

   [8]   Niven-Jenkins, B., Brungard, D., Betts, M., "MPLS-TP
         Requirements", draft-ietf-mpls-tp-requirements, November 2008

Authors' Addresses

   Martin Vigoureux
   Alcatel-Lucent

   Email: martin.vigoureux@alcatel-lucent.com


   David Ward
   Cisco Systems, Inc.

   Email: dward@cisco.com






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   Malcolm Betts
   Nortel Networks

   Email: betts01@nortel.com


Contributing Authors' Addresses

   Matthew Bocci
   Alcatel-Lucent

   Email: matthew.bocci@alcatel-lucent.com


   Italo Busi
   Alcatel-Lucent

   Email: italo.busi@alcatel-lucent.it


   Huub van Helvoort
   Huawei Technologies Co.Ltd.

   Email: hhelvoort@huawei.com


   Marc Lasserre
   Alcatel-Lucent

   Email: mlasserre@alcatel-lucent.com


   Lieven Levrau
   Alcatel-Lucent

   Email: llevrau@alcatel-lucent.com


   Han Li
   China Mobile Communications Corporation (CMCC)
   Email: lihan@chinamobile.com








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   Julien Meuric
   Orange

   Email: julien.meuric@orange-ftgroup.com


   Philippe Niger
   Orange

   Email: philippe.niger@orange-ftgroup.com


   Benjamin Niven-Jenkins
   BT

   Email: benjamin.niven-jenkins@bt.com


   Jing Ruiquan
   China Telecom
   Email: jingrq@ctbri.com.cn


   Nurit Sprecher
   Nokia-Siemens Networks

   Email: nurit.sprecher@nsn.com


   Yuji Tochio
   Fujitsu

   Email: tochio@jp.fujitsu.com


   Yaacov Weingarten
   Nokia-Siemens Networks

   Email: yaacov.weingarten@nsn.com


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Internet-Draft       OAM Requirements for MPLS-TP         November 2008


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