A framework for Point-to-Multipoint MPLS-TP OAM
draft-hmk-mpls-tp-p2mp-oam-framework-01

MPLS Working Group                                        Y.Koike, Ed.
Internet Draft                                               T.Hamano
                                                             M.Namiki
                                                                  NTT
Intended status: Informational

Expires: May 8, 2013                                  November 9, 2012

              A framework for Point-to-Multipoint MPLS-TP OAM
                draft-hmk-mpls-tp-p2mp-oam-framework-01.txt

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Abstract

   The MPLS transport profile (MPLS-TP) is being standardized to enable
   carrier-grade packet transport.

   This document discusses and specifies P2MP framework primarily
   related to OAM, management, and recovery. This document is mainly
   based on RFC5654 and RFC6371. The main focus is on the details not
   covered in relevant RFCs such as RFC5654, RFC5860, RFC5921, RFC5951,
   RFC6371 and the draft-fbb-mpls-tp-p2mp-framework. Other requirements
   for p2mp transport paths, such as recovery, will also be specified in
   a future version on the premise that there are return paths.

   Note: This I-D was made and updated based on discussions in ITU-T
   SG15, which were described in Liaison Statements: Request advance
   work on the P2MP framework in the MPLS-TP
   (https://datatracker.ietf.org/liaison/1163/) and Progressing work on
   P2MP MPLS-TP connections (https://datatracker.ietf.org/liaison/1202/)

   This document is a product of a joint Internet Engineering Task Force
   (IETF) / International Telecommunications Union Telecommunications
   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.

Table of Contents

   1. Introduction ................................................ 3
   2. Conventions used in this document............................ 4
      2.1. Terminology ............................................ 4
      2.2. Definitions ............................................ 5
   3. P2MP OAM .................................................... 5

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      3.1. OAM functions for proactive monitoring .................. 6
         3.1.1. Continuity Check and Connectivity Verification                                                                  ...... 8
         3.1.2. Remote Defect Indication ........................... 9
         3.1.3. Alarm Reporting .................................... 9
         3.1.4. Lock Reporting ..................................... 9
         3.1.5. Packet Loss Measurement ............................ 9
         3.1.6. Packet Delay Measurement ........................... 9
         3.1.7. Client Failure Indication .......................... 9
      3.2. OAM functions for on-demand monitoring .................. 9
         3.2.1. Connectivity verification .......................... 9
         3.2.2. Packet loss measurement ........................... 10
         3.2.3. Diagnostic tests .................................. 10
         3.2.4. Route Tracing ..................................... 10
         3.2.5. Packet delay measurement .......................... 10
      3.3. OAM functions for administration control ............... 11
         3.3.1. Lock Instruct ..................................... 11
   4. Security Considerations ..................................... 11
   5. IANA Considerations ........................................ 11
   6. References ................................................. 11
      6.1. Normative References ................................... 11
      6.2. Informative References ................................. 11
   7. Acknowledgments ............................................ 11

1. Introduction

   The demand for P2MP traffic is expected to increase due to the
   increase in new services such as IP-TV and video distribution
   services. In light of the global trend of improving energy efficiency,
   a point-to-multipoint (P2MP) transport function in MPLS-TP could be
   one of the solutions for achieving this goal from the perspective of
   efficient use of network resources.

   RFC5654[1] defines the following requirements that are specific to
   P2MP.

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   - Traffic-engineered point-to-multipoint (P2MP) transport paths.(item
   6).
   - Unidirectional point-to-multipoint(P2MP) transport paths (item 8)
   - Being capable of using P2MP server (sub)layer capabilities when
   supporting P2MP MPLS-TP transport paths(item 40)
   - The MPLS-TP control plane MUST support establishing all the
   connectivity patterns defined for the MPLS-TP data plane (i.e.
   unidirectional P2MP) including the configuration of protection
   functions and any associated maintenance functions.(item 50)
   Unidirectional 1+1 protection for P2MP connectivity (item 65 C)
   - Unidirectional 1:n protection for P2MP connectivity(item 67 B)
   - MPLS-TP recovery in a ring MUST protect unidirectional P2MP
   transport paths.(item 95)

   RFC5860 [2] defines MPLS-TP OAM requirements including those for
   unidirectional P2MP transport paths. With a unidirectional P2MP
   transport path, two cases are assumed as per Section 3.3 of
   RFC6371[3]. One is when no return path exists or not used and the
   other is when an out-of-band return path exists and used.

   In I-D[4], only a summary of various items specific to MPLS-TP P2MP
   framework. For example, according to the editor's note, this section
   will contain a summary of P2MP OAM, as described in RFC6371 [3],
   which defines the overall OAM architecture for MPLS-TP.

   Therefore, this draft intends to specify details of a P2MP framework
   that complements P2MP requirements and the framework of existing RFCs,
   particularly in terms of OAM, management, and recovery.

   Note: MPLS-TP functions that are applicable specifically to P2MP
   transport paths are outside the scope of RFC5921.

2. Conventions used in this document

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

  2.1. Terminology

   EMS  Element management system

   LSP  Label Switched Path

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   NE   Network Element

   NMS  Network Management System

  2.2. Definitions

   None

3. P2MP OAM, management and recovery

   The support of P2MP OAM on the data path should be independent of the
   availability of a return path or the mechanism that supports the
   return path. Basically, only unidirectional P2MP is supported in
   MPLS-TP. This means that an In-band return path is out of the scope
   of MPLS-TP requirements. In this section, two cases, with out-band
   return path and without return path, are considered basics and
   requirements when return paths exist should be independently
   specified from when no return path exists.

   P2MP considerations are described in Section 3.7 of RFC6371. The RFC
   has already described some requirements with out-band return path(s).
   On the other hand, even if there is no return path, most of OAM
   requirements in RFC5860 could be met by supporting management
   interface through which EMS/NMS can retrieve the received OAM packets.

   The return path may be considered to be directed to the entity that
   originally requested the measurements because this may not be the
   head end of the P2MP connection. Therefore, the following return path
   should be distinctly differentiated.

      RP-N: A return path to the EMS/NMS through the management
      interface (RP-N) (This case is referred to as that in which no
      return path exists)

      RP-HE: A return path to a head end of a P2MP path using any
      kind of out-of-band path (This case is referred to as that in
      which an out-of-band return path exists)

   These two kinds of return paths may be applied at the same time,
   depending on the situations.

   Note: In the following sections, additional requirements are
   basically described function-by-function, which have not been covered

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   or clarified in RFC5860[2] and RFC6371 [3], which have focused
   particularly on when return paths do not exist.

  3.1. General aspects of P2MP OAM

   P2MP transport paths are unidirectional; therefore, there is
   generally no in-band return path as in the MPLS-TP transport path per
   se. However, there are basically two approaches for handling OAM
   requirements in P2MP MPLS-TP.

   The first one is used to report the results of the
   monitoring/measurement of OAM packets from the OAM target node to the
   EMS/NMS when the NMS usually instantiates OAM functions and requires
   the results of OAM monitoring functions. This approach is called RP-N.
   The second approach is the return path to a root (source MEP) of a
   P2MP path using different methods such as a unidirectional p2p
   transport paths, and other technology-layers, such as IP, Ethernet,
   and OTN, when an NE within which a root MEP resides instantiates OAM
   functions or receive results of OAM monitoring functions. This
   approach is called as RP-HE. The following requirements are supported
   in terms of network elements when considering RP-N.

   1. OAM functions of a MEG of a P2MP transport path should be
      configurable using the EMS/NMS.

   2. Source nodes at which the source MEP reside and OAM packets are
      generated should receive OAM related information such as
      enabling/disabling OAM functions and setting/changing OAM
      attributes from the EMS/NMS on a P2MP transport path.

   3. Sink nodes at which targeting MIPs or MEPs reside and OAM packets
      are parsed should report OAM related information such as OAM
      monitoring results and consequent OAM actions to the EMS/NMS.

   4. Each OAM function of a P2MP transport path should be able to be
      independently configured using the EMS/NMS based on the
      classification of OAM functional requirements in RFC5860.

   5. An on-demand OAM function must be able to perform an OAM function
      for only a specific target MIP or MEP as well as all MEPs in a
      P2MP transport path, as specified in Section 3.7 of RFC6371[3].

   6. To manage M leaves(i.e., subset of all leaves) in an on-demand OAM
      function from the EMS/NMS, a unified mechanism must be provided.

      Note: Currently, sending an OAM packet that is targeted at a
      subset of M leaves by using an aggregating mechanism such as an

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      OAM packet including several MIP or MEP identifiers is out of the
      scope of RFC6371[3] as described in Section 3.7 of that document.

   7. Mismatches of configuration information between a root MEP and any
      leaf-MEP, at which proactive or on-demand monitoring is enabled,
      should be detected as a configuration mismatch alarm and be
      reported to the EMS/NMS by parsing received OAM packets,
      particularly when a static setting is applied.

   Generally when each OAM function is enabled, as described in Section
   5.1 of RFC6371[3], the source MEP function should be enabled prior to
   the corresponding sink MEPs function.

   Regarding configuration considerations, the following are additional
   requirements for unidirectional P2MP transport path, particularly
   when RP-HE does not exist.

   8. The configuration of each OAM function between the source MEP and
      sink MEP(s) in an MEG of a transport path should be able to be
      synchronized using the NMS, when a new P2MP transport path is set.

   9. The configuration of newly added/removed specific sink MEP(s)to
      the existing source MEP in the MEG in proactive monitoring should
      be able to be synchronized with that of the source MEP by using
      the NMS.

   10.The EMS/NMS should provide a tool for manually configuring
      consistent values of each piece of configuration information to a
      root MEP and all the related leaf MEPs in a MEG of a P2MP
      transport path for both pro-active and on-demand OAM functions.

   11.Mismatches of configuration information between a leaf MEP and any
      other leaf MEP(s) or a root MEP and leaf MEP(s), at which
      proactive monitoring will be enabled, should be able to be
      detected through the configuration management process of the
      EMS/NMS as a configuration mismatch alarm or notification without
      receiving OAM packets from a source MEP(before OAM functions are
      enabled).

      Note: This requirement is not necessary if the EMS/NMS provides a
      tool to manually configure a consistent value of each piece of
      configuration information to a root MEP.

   12.The enabling or disabling of proactive OAM functions and
      configuration mismatch alarms of the OAM functions must be
      independently configurable at each leaf-MEP as well as on all the
      leaf MEPs on a P2MP transport path, considering maintenances or a

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      case in which one or more leaf MEPs is newly added or removed
      later.

   13.Mismatches of configuration information between a leaf MEP and any
      other leaf MEP(s) or a root MEP and leaf MEP(s), at which on-
      demand OAM monitoring is enabled, must be detected as a
      configuration management process before conducting OAM functions.

  3.2. OAM functions for proactive monitoring

   The proactive OAM functions are used to detect a fault/defect or to
   automatically reports a change in the status of a transport path.

3.2.1. Continuity Check and Connectivity Verification(CC-V)

   The continuity Check function enables one or more leaf MEPs on a
   unidirectional P2MP transport path to monitor the continuity of OAM
   packets from root MEP and detect one or more loss of continuity(LOC)
   defects between the root MEP and leaf MEPs.

   The connectivity verification function enables one or more leaf MEPs
   on a P2MP transport path to monitor the connectivity of OAM packets
   from a specific root MEP and detect an unexpected connectivity defect
   between two MEGs(two P2MP transport paths)

   As described in Sections 2.2.2 and 2.2.3 of RFC5860[2], CC-V MUST be
   supported even when RP-HE does not exist.

   As described in RFC6371[3], CC-V OAM packets are used for a P2MP
   transport path. Defect detection mechanisms in P2MP transport paths
   are the same as those of the P2MP transport path specified in section
   5.1.1 of RFC6371 [3]. That is, loss of continuity(LoC) defect, mis-
   connectivity defect, period mis-configuration defect and unexpected
   encapsulation defect. Entry and exit criteria are also the same as
   those of the P2MP transport paths in RFC6371 [3]. However, in a P2MP
   transport path, all the leaf MEPs that detect a defect must be
   indentified and differentiated from a normal leaf MEP(s), which does
   not detect a defect.

   Configuration is specified in Section 5.1.3 of RFC6371[3]. The
   following configuration information must be configured: MEG-ID, MEP-
   ID, list of the other MEPs in the MEG that are different between the
   root MEP and leaf MEP, PHB for E-LSP and transmission rate.

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   Consequent actions of a unidirectional P2MP transport path are also
   covered in Section 5.1.2 of RFC6371 [3]. Operators should be able to
   enable/disable each consequent action.

   All MEPs inside a MEG need to be configured and retain the
   information when a proactive OAM function is enabled, as described in
   Section 5.1.3 of RFC6371[3]. If there is no RP-HE, it is premised
   that the EMS/NMS exists. Therefore, the above parameters are
   statically configured.

3.2.2. Remote Defect Indication

   This OAM function is not available on a P2MP transport path when
   return paths do not exist. This OAM function can be implemented only
   in RP-HE. However, the return path is out of the scope of MPLS-TP
   requirements.

3.2.3. Alarm Reporting

  FFS

3.2.4. Lock Reporting

   For further study(FFS)

3.2.5. Packet Loss Measurement

   FFS

3.2.6. Packet Delay Measurement

   FFS

3.2.7. Client Failure Indication

   FFS

  3.3. OAM functions for on-demand monitoring

3.3.1. Connectivity verification

   The connectivity verification function enables one or more leaf MEPs
   on a P2MP transport path to monitor the connectivity of OAM packets

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   from a specific root MEP and detect an unexpected connectivity defect
   between two MEGs (two P2MP transport paths)

   1. Connectivity verification functions MUST be supported when return
      paths in a unidirectional P2MP transport path do not exist.

   As described in RFC6371 [3], CC-V OAM packets are used for a P2MP
   transport path. Defect detection mechanisms in P2MP transport paths
   are the same as those of the P2MP transport path specified in section
   5.1 of RFC6371. That is, loss of continuity defect, mis-connectivity
   defect, period mis-configuration defect and unexpected encapsulation
   defect. Entry and exit criteria are also the same as those of the
   P2MP transport path in RFC6371 [3]. Moreover, consequent actions of a
   unidirectional P2MP transport path are also covered in Section 5.1.2
   of the RFC [3]

   Regarding configuration consideration, the following additional
   requirements on a unidirectional P2MP transport path when a return
   path does not exist.

3.3.2. Packet loss measurement

   FFS

3.3.3. Diagnostic tests

      Diagnostic test functions MUST be supported when a return path in
      a unidirectional P2MP transport path doesn't exist.

   Other requirements are ffs.

3.3.4. Route Tracing

      Route tracing function MUST be supported when a return path in a
      unidirectional P2MP transport path doesn't exist.

   Other requirements are ffs.

3.3.5. Packet delay measurement

   FFS

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  3.4. OAM functions for administration control

3.4.1. Lock Instruct

   FFS.

4. P2MP Recovery

FFS

5. Security Considerations

   This document does not raise any particular security considerations.

6. IANA Considerations

   There are no IANA actions required by this draft.

7. References

  7.1. Normative References

   [1]  Niven-Jenkins, B., et all, "equirements of an MPLS Transport
         Profile" RFC5654, September 2009

   [2]  Vigoureux, M., Betts, M., Ward, D., "Requirements for OAM in
         MPLS Transport Networks", RFC5860, May 2010

   [3]  Busi, I., Dave, A. , "Operations, Administration and
         Maintenance Framework for MPLS-based Transport Networks ",
         RFC6371, September 2011

   [4]  Frost, Dan.,et all, "Framework for Point-to-Multipoint MPLS
         in Transport Networks" draft-fbb-mpls-tp-p2mp-framework-05,
         August 2012

  7.2. Informative References

   None

8. Acknowledgments

   The author would like to thank all members (including MPLS-TP
   steering committee, the Joint Working Team, the MPLS-TP Ad Hoc Group

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   in ITU-T) involved in the definition and specification of MPLS
   Transport Profile.

   This document was prepared using 2-Word-v2.0.template.dot.

Authors Addresses

   Takafumi Hamano
   NTT
   hamano.takafumi@lab.ntt.co.jp

   Masatoshi Namiki
   NTT
   namiki.masatoshi@lab.ntt.co.jp

   Yoshinori Koike
   NTT
   Email: koike.yoshinori@lab.ntt.co.jp

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