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Versions: (draft-sprecher-mpls-tp-oam-analysis) 00 01 02 03 04 05 06 07 08 09 RFC 6669

Network Working Group                                        N. Sprecher
Internet-Draft                                    Nokia Siemens Networks
Intended status: Informational                             E. Bellagamba
Expires: January 5, 2011                                        Ericsson
                                                           Y. Weingarten
                                                  Nokia Siemens Networks
                                                            July 4, 2010


                          MPLS-TP OAM Analysis
                 draft-ietf-mpls-tp-oam-analysis-02.txt

Abstract

   This document analyzes the set of requirements for Operations,
   Administration, and Maintenance (OAM) for the Transport Profile of
   MPLS(MPLS-TP) as defined in [MPLS-TP OAM Reqs], to evaluate whether
   existing OAM tools (either from the current MPLS toolset or from the
   ITU-T documents) can be applied to these requirements.  Eventually,
   the purpose of the document is to map the set of functions to a set
   of tools based on the existing OAM toolset.

Status of this Memo

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

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on January 5, 2011.

Copyright Notice

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   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Scope  . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.2.  Organization of the document . . . . . . . . . . . . . . .  4
     1.3.  Contributing Authors . . . . . . . . . . . . . . . . . . .  5
     1.4.  Acronyms . . . . . . . . . . . . . . . . . . . . . . . . .  5
   2.  Basic OAM infrastructure functionality . . . . . . . . . . . .  5
   3.  MPLS-TP OAM Functions  . . . . . . . . . . . . . . . . . . . .  6
     3.1.  Continuity Check and Connectivity Verification . . . . . .  7
       3.1.1.  Documents for CC-V tools . . . . . . . . . . . . . . .  7
     3.2.  Remote Defect Indication . . . . . . . . . . . . . . . . .  7
       3.2.1.  Documents for RDI  . . . . . . . . . . . . . . . . . .  7
     3.3.  Route Tracing  . . . . . . . . . . . . . . . . . . . . . .  7
       3.3.1.  Documents for Route Tracing  . . . . . . . . . . . . .  8
     3.4.  Alarm Reporting  . . . . . . . . . . . . . . . . . . . . .  8
       3.4.1.  Documents for Alarm Reporting  . . . . . . . . . . . .  8
     3.5.  Lock Reporting . . . . . . . . . . . . . . . . . . . . . .  8
       3.5.1.  Documents for Lock Reporting . . . . . . . . . . . . .  8
     3.6.  Diagnostic . . . . . . . . . . . . . . . . . . . . . . . .  8
       3.6.1.  Documents for Diagnostic Testing . . . . . . . . . . .  9
     3.7.  Lock Instruct  . . . . . . . . . . . . . . . . . . . . . .  9
       3.7.1.  Documents for Lock Instruct  . . . . . . . . . . . . .  9
     3.8.  Client Failure Indication  . . . . . . . . . . . . . . . .  9
       3.8.1.  Documents for CFI  . . . . . . . . . . . . . . . . . .  9
     3.9.  Packet Loss Measurement  . . . . . . . . . . . . . . . . .  9
       3.9.1.  Documents for Packet Loss Measurement  . . . . . . . . 10
     3.10. Packet Delay Measurement . . . . . . . . . . . . . . . . . 10
       3.10.1. Documents for Delay Measurement  . . . . . . . . . . . 10
   4.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   6.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   7.  Informative References . . . . . . . . . . . . . . . . . . . . 11
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12

















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1.  Introduction

1.1.  Scope

   OAM (Operations, Administration, and Maintenance) plays a significant
   role in carrier networks, providing methods for fault management and
   performance monitoring in both the transport and the service layers
   in order to improve their ability to support services with guaranteed
   and strict Service Level Agreements (SLAs) while reducing their
   operational costs.

   [MPLS-TP Reqs] in general, and [MPLS-TP OAM Reqs] in particular
   define a set of requirements for OAM functionality in MPLS-Transport
   Profile (MPLS-TP) for MPLS-TP Segments, Label Switched Paths (LSPs)
   (network infrastructure) and Pseudowires (PWs) (services).  One of
   the mandates of the joint (IETF and ITU-T) MPLS-TP work-item is the
   objective of developing a Transport Profile is to base the toolset on
   existing MPLS technologies.  In addition, [MPLS-TP Reqs] indicates
   the need for the OAM toolset for MPLS-TP to be fully interoperable
   with existing MPLS OAM tools.

   The purpose of this document is to outline the recommendations of the
   MPLS-TP design team and confirmed by the working group for the
   toolset that should be defined to fulfill the OAM functionality
   requirements as documented in [MPLS-TP OAM Reqs] and [MPLS-TP OAM
   Frwk].  Based on the principles cited above, it was determined to
   base the MPLS-TP OAM toolset on the following existing MPLS tools:

   o  LSP-Ping as defined in [LSP Ping].

   o  Bidirectional Forwarding Detection (BFD) as defined in [BASE BFD]
      and refined in [MPLS BFD].

   o  ITU-T OAM for Ethernet toolset as defined in [Y.1731] this will be
      used for functionality guidelines for the performance measurement
      tools that are not currently supported in MPLS.

   It should be noted that certain extensions and adjustments may be
   made to the existing MPLS tools, in order to conform to the transport
   environment and the requirements of MPLS-TP.

1.2.  Organization of the document

   Section 2 of the document provides references to the basic OAM tools
   that are provided for MPLS-TP OAM.

   Section 3 outlines the different tools that are required for MPLS-TP
   OAM and references the documents that will define the appropriate



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   tools based on the principles outlined above.

1.3.  Contributing Authors

   Yaakov Stein (Rad), Annamaria Fulignoli (Ericsson), Italo Busi
   (Alcatel Lucent), Huub van Helvoort (Huawei)

1.4.  Acronyms

   This draft uses the following acronyms:

   ACH     Associated Channel Header
   BFD     Bidirectional Forwarding Detection
   CC-V    Continuity Check and Connectivity Verification
   G-ACH   Generic Associated Channel Header
   LSP     Label Switched Path
   MPLS-TP Transport Profile for MPLS
   OAM     Operations, Administration, and Maintenance
   PW      Pseudowire
   RDI     Remote Defect Indication
   SLA     Service Level Agreement
   TLV     Type, Length, Value
   VCCV    Virtual Circuit Connectivity Verification


2.  Basic OAM infrastructure functionality

   [MPLS-TP OAM Reqs] defines a set of requirements on OAM architecture
   and general principles of operations which are evaluated below:

   o  [MPLS-TP OAM Reqs] requires that OAM mechanisms in MPLS-TP are
      independent of the transmission media and of the client service
      being emulated by the PW.

   o  [MPLS-TP OAM Reqs] requires that the MPLS-TP OAM must be able to
      support both an IP based and non-IP based environment.  If the
      network is IP based, i.e.  IP routing and forwarding are
      available, then the MPLS-TP OAM toolset should rely on the IP
      routing and forwarding capabilities.  On the other hand, in
      environments where IP functionality is not available, the OAM
      tools must still be able to operate without dependence on IP
      forwarding and routing.

   o  [MPLS-TP OAM Reqs] requires that all OAM protocols support
      identification information, at least in the form of IP addressing
      structure and be extensible to support additional identification
      schemes.




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   o  It is also required that OAM packets and the user traffic are
      congruent (i.e.  OAM packets are transmitted in-band) and there is
      a need to differentiate OAM packets from user-plane ones.
      Inherent in this requirement is the principle that MPLS-TP OAM be
      independent of any existing control-plane, although it should not
      preclude use of the control-plane functionality.

   o  [MPLS-TP OAM Reqs] requires a single OAM technology and consistent
      OAM capabilities for LSPs, PWs, and Sections.

   o  [MPLS-TP OAM Reqs] requires allowing OAM packets to be directed to
      an intermediate point of a LSP/PW.

   The following comprise the document-set that addresses the basic
   requirements listed above:

   o  The [MPLS-TP OAM Frwk] document describes the architecural
      framework for conformance to the basic requirements listed above.
      It also defines the basic relationships between the MPLS
      structures, e.g.  LSP, PW, and the structures necessary for OAM
      functionality, i.e. the Managed Entity Group, its End-points, and
      Intermediate Points.

   o  The [MPLS G-ACH] document specifies the use of the MPLS-TP in-
      band control channel.  This is modeled after the VCCV channel
      described in [PW ACH] and allows transporting the OAM messages
      congruently with the data traffic while allowing the required
      identification of the packets.  It is expected that all of the OAM
      protocols will be used in conjunction with this Generic Associated
      Channel.

   o  The [MPLS-TP ACH TLV] document specifies a basic set of TLV fields
      that could be used by different OAM messages, in conjunction with
      the Generic Associated Channel, to supply the additional parameter
      values necessary for the proper functionality.

   o  The [MPLS TP Idents] document addresses the need of MPLS-TP to
      support different addressing spaces.  This document describes
      different formats for addresses that could be used to identify the
      transport entities in the network and referenced by the different
      OAM protocols.


3.  MPLS-TP OAM Functions

   The following sections discuss the required OAM functions that were
   identified in [MPLS-TP OAM Reqs] and expanded upon in [MPLS-TP OAM
   Frwk].



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3.1.  Continuity Check and Connectivity Verification

   Continuity Check and Connectivity Verification (CC-V) are OAM
   operations generally used in tandem, and compliment each other.
   These functions are generally run proactively, but may also be used
   on-demand, either due to bandwidth considerations or for diagnoses of
   a specific condition.  Proactively [MPLS-TP OAM Reqs] states that the
   function should allow the MEPs to monitor the liveness and
   connectivity of a transport path.  In on-demand mode, this function
   should support monitoring between the MEPs and, in addition, between
   a MEP and MIP.

   The [MPLS-TP OAM Frwk] highlights the need for the CC-V messages to
   include unique identification of the MEG that is being monitored and
   the MEP that originated the message.  The function, both proactively
   and in on-demand mode, need to be transmitted at regular rates pre-
   configured by the operator.

3.1.1.  Documents for CC-V tools

   [Pro CC-V] defines the BFD extensions that will be used for proactive
   CC-V applications.  While [Demand CV] provides the LSP-Ping
   extensions that will be used to implement on-demand Connectivity
   Verification.  Both of these tools will be used together with the
   basic tools mentioned above in section 2

3.2.  Remote Defect Indication

   Remote Defect Indication (RDI) is used by a path end-point to report
   to its peer end-point that a defect is detected on a bi-directional
   connection between them.  [MPLS-TP OAM Reqs] points out that this
   function may be applied to a unidirectional LSP only if there a
   return path exists.  [MPLS-TP OAM Frwk] points out that this function
   is associated with the proactive CC-V function

3.2.1.  Documents for RDI

   The [Pro CC-V] document includes and extension for BFD that would
   include the RDI indication in the BFD format, and a specification of
   how this indication is to be used.

3.3.  Route Tracing

   [MPLS-TP OAM Reqs] defines that there is a need for functionality
   that would allow a path end-point to identify the intermediate and
   end-points of the path.  This function would be used in on-demand
   mode.  Normally, this path will be used for bidirectional PW, LSP,
   and sections, however, unidirectional paths may be supported only if



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   a return path exists.

3.3.1.  Documents for Route Tracing

   The [Demand CV] document that specifies the LSP-Ping enhancements for
   MPLS-TP on-demand Connectivity Verification includes information on
   the use of LSP-Ping for route tracing of a MPLS-TP transport path.

3.4.  Alarm Reporting

   Alarm Reporting is a function used by an intermediate point of a
   path, that becomes aware of a fault on the path, to report to the
   end-points of the path.  [MPLS-TP OAM Frwk] states that this may
   occur as a result of a defect condition discovered at a server sub-
   layer.  This generates an Alarm Indication Signal (AIS) that
   continues until the fault is cleared.  The consequent action of this
   function is detailed in [MPLS-TP OAM Frwk].

3.4.1.  Documents for Alarm Reporting

   MPLS-TP defines a new protocol to address this functionality that is
   documented in [Fault Mng].  This protocol uses all of the basic
   mechanisms detailed in Section 2.

3.5.  Lock Reporting

   Lock reporting, defined in [MPLS-TP OAM Reqs], is similar to the
   Alarm Reporting function described above.  It is used by an
   intermediate point to notify the end points of a transport path that
   an administrative lock condition exists for this transport path.

3.5.1.  Documents for Lock Reporting

   MPLS-TP defines a new protocol to address this functionality that is
   documented in [Fault Mng].  This protocol uses all of the basic
   mechanisms detailed in Section 2.

3.6.  Diagnostic

   The [MPLS-TP OAM Reqs] indicates that there is need to provide a OAM
   function that would enable conducting different diagnostic tests on a
   PW, LSP, or Section.  The [MPLS-TP OAM Frwk] provides two types of
   specific tests to be used through this functionality:

   o  Throughput Estimation - allowing the provider to verify the
      bandwidth/throughput of a transport path.  This is an out-of-
      service tool, that uses special packets of varying sizes to test
      the actual bandwidth and/or throughput of the path.



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   o  Data-plane loopback - this out-of-service tool that causes all
      traffic that reaches the target node, either a MEP or MIP, to be
      looped back to the originating MEP.  For targeting MIPs, a
      corouted bi-directional path is required.

3.6.1.  Documents for Diagnostic Testing

   These diagnostic functions are being defined in a merge of existing
   separate individual drafts.  The merged document will define a new
   G-ACH based protocol message that addresses the Throughput Estimation
   tool, and also provide various flavors of loopback functionality.

3.7.  Lock Instruct

   The Lock Instruct function is an administrative control tool that
   allows a path end-point to instruct its peer end-point to lock the
   path.  The tool is necessary to support single-side provisioning for
   administartive locking, according to .  This function is used on-
   demand.

3.7.1.  Documents for Lock Instruct

   Work is being done on a document that will specify the new ACH based
   protocol format for this tool.

3.8.  Client Failure Indication

   Client Failure Indication (CFI) is defined in [MPLS-TP OAM Reqs] to
   allow the propagation information from one edge of the network to the
   other.  The information concerns a defect to a client, in the case
   that the client does not support alarm notification.

3.8.1.  Documents for CFI

   Work is being done on a document that will specify the new ACH based
   protocol format for this tool.

3.9.  Packet Loss Measurement

   Packet Loss Measurement is required, by [MPLS-TP OAM Reqs] to provide
   a quantification of the packet loss ratio on a transport path.  This
   is the ratio of the number of user packets lost to the total number
   of user packets during a defined time interval.  To employ this
   function, [MPLS-TP OAM Frwk] defines that the two end-points of the
   transport path should exchange counters of messages transmitted and
   received within a time period bounded by loss-measurement messages.
   The framework warns that there may be small errors in the computation
   that result from various issues.



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3.9.1.  Documents for Packet Loss Measurement

   The [Loss-Delay] describes the protocol formats and procedures for
   using the tool.  The tool logic is based on the behavior of the
   parallel function described in [Y.1731].

3.10.  Packet Delay Measurement

   Packet Delay Measurement is a function that is used to measure one-
   way or two-way delay of a packet transmission between a pair of the
   end-points of a path (PW, LSP, or Section), as described in [MPLS-TP
   OAM Reqs].  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.

   [MPLS-TP OAM Frwk] describes how the tool could be performed (both in
   proactive and on-demand modes) for either one-way or two-way
   measurement.  However, it warns that the one-way delay option
   requires precise time synchronization between the end-points.

3.10.1.  Documents for Delay Measurement

   The [Loss-Delay] describes the protocol formats and procedures for
   using the tool.  The tool logic is based on the behavior of the
   parallel function described in [Y.1731].


4.  IANA Considerations

   This document makes no request of IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.


5.  Security Considerations

   This document does not by itself raise any particular security
   considerations.



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6.  Acknowledgements

   The editors wish to thank the MPLS-TP Design Team members, from both
   the IETF and ITU-T leadership teams, in formulating the
   recommendations documented here.  In particular, we would like to
   thank Loa Andersson, Huub van Helvoort, and the Area Directors for
   their suggestions and enhancements to the text.


7.  Informative References

   [LSP Ping]
              Kompella, K. and G. Swallow, "Detecting Multi-Protocol
              Label Switched (MPLS) Data Plane Failures", RFC 4379,
              February 2006.

   [PW ACH]   Bryant, S., Swallow, G., Martini, L., and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over an MPLS PSN", RFC 4385, February 2006.

   [BASE BFD]
              Katz, D. and D. Ward, "Bidirectional Forwarding
              Detection", RFC 5880, February 2009.

   [MPLS BFD]
              Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
              "BFD For MPLS LSPs", RFC 5884, June 2008.

   [MPLS TP Idents]
              Bocci, M. and G. Swallow, "MPLS-TP Identifiers",
              ID draft-ietf-mpls-tp-identifiers-01.txt, March 2010.

   [Pro CC-V]
              Allan, D. and G. Swallow, "Proactive Connection
              Verification, Continuity Check and Remote Defect
              indication for MPLS Transport Profile",
              ID draft-ietf-mpls-tp-cc-cv-rdi-00.txt, June 2010.

   [Demand CV]
              Bahadur, N., Aggarwal, R., Boutros, S., and E. Gray, "MPLS
              on-demand Connectivity Verification, Route Tracing and
              Adjacency Verification",
              ID draft-ietf-mpls-tp-on-demand-cv-00, June 2010.

   [MPLS-TP OAM Reqs]
              Vigoureux, M., Betts, M., and D. Ward, "Requirements for
              OAM in MPLS Transport Networks",
              ID draft-ietf-mpls-tp-oam-requirements-05, April 2009.



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   [MPLS-TP OAM Frwk]
              Busi, I., Niven-Jenkins, B., and D. Allan, "MPLS-TP OAM
              Framework and Overview",
              ID draft-ietf-mpls-tp-oam-framework-07, July 2010.

   [MPLS-TP Reqs]
              Niven-Jenkins, B., Nadeau, T., and C. Pignataro,
              "Requirements for the Trasport Profile of MPLS",
              ID draft-ietf-mpls-tp-requirements-06, April 2009.

   [MPLS G-ACH]
              Bocci, M., Bryant, S., and M. Vigoureux, "MPLS Generic
              Associated Channel", RFC 5586, June 2009.

   [MPLS-TP ACH TLV]
              Boutros, S., Bryant, S., Sivabalan, S., Swallow, G., and
              D. Ward, "Definition of ACH TLV Structure",
              ID draft-ietf-mpls-tp-ach-tlv-00, June 2009.

   [Fault Mng]
              Swallow, G., Fulignoli, A., and M. Vigoureux, "MPLS Fault
              Management OAM", ID draft-ietf-mpls-tp-fault-00,
              March 2010.

   [Loss-Delay]
              Frost, D. and S. Bryant, "Packet Loss and Delay
              Measurement for the MPLS Transport Profile",
              ID draft-frost-mpls-tp-loss-delay-00, April 2010.

   [Y.1731]   International Telecommunications Union - Standardization,
              "OAM functions and mechanisms for Ethernet based
              networks", ITU Y.1731, May 2006.


Authors' Addresses

   Nurit Sprecher
   Nokia Siemens Networks
   3 Hanagar St. Neve Ne'eman B
   Hod Hasharon,   45241
   Israel

   Email: nurit.sprecher@nsn.com








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   Elisa Bellagamba
   Ericsson
   6 Farogatan St
   Stockholm,   164 40
   Sweden

   Phone: +46 761440785
   Email: elisa.bellagamba@ericsson.com


   Yaacov Weingarten
   Nokia Siemens Networks
   3 Hanagar St. Neve Ne'eman B
   Hod Hasharon,   45241
   Israel

   Phone: +972-9-775 1827
   Email: yaacov.weingarten@nsn.com

































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