GMPLS Asymmetric Bandwidth Bidirectional Label Switched Paths (LSPs)
RFC 5467

Network Working Group                                          L. Berger
Request for Comments: 5467                                          LabN
Category: Experimental                                         A. Takacs
                                                                Ericsson
                                                             D. Caviglia
                                                                Ericsson
                                                                D. Fedyk
                                                                  Nortel
                                                               J. Meuric
                                                          France Telecom
                                                              March 2009

  GMPLS Asymmetric Bandwidth Bidirectional Label Switched Paths (LSPs)

Status of This Memo

   This memo defines an Experimental Protocol for the Internet
   community.  It does not specify an Internet standard of any kind.
   Discussion and suggestions for improvement are requested.
   Distribution of this memo is unlimited.

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Abstract

   This document defines a method for the support of GMPLS asymmetric
   bandwidth bidirectional Label Switched Paths (LSPs).  The presented
   approach is applicable to any switching technology and builds on the
   original Resource Reservation Protocol (RSVP) model for the transport
   of traffic-related parameters.  The procedures described in this
   document are experimental.

Table of Contents

   1. Introduction ....................................................2
      1.1. Background .................................................3
      1.2. Approach Overview ..........................................3
      1.3. Conventions Used in This Document ..........................4
   2. Generalized Asymmetric Bandwidth Bidirectional LSPs .............4
      2.1. UPSTREAM_FLOWSPEC Object ...................................5
           2.1.1. Procedures ..........................................5
      2.2. UPSTREAM_TSPEC Object ......................................5
           2.2.1. Procedures ..........................................5
      2.3. UPSTREAM_ADSPEC Object .....................................6
           2.3.1. Procedures ..........................................6
   3. Packet Formats ..................................................6
   4. Compatibility ...................................................7
   5. IANA Considerations .............................................8
      5.1. UPSTREAM_FLOWSPEC Object ...................................8
      5.2. UPSTREAM_TSPEC Object ......................................8
      5.3. UPSTREAM_ADSPEC Object .....................................8
   6. Security Considerations .........................................8
   7. References ......................................................9
      7.1. Normative References .......................................9
      7.2. Informative References .....................................9
   Appendix A. Alternate Approach Using ADSPEC Object.................11
      A.1. Applicability .............................................11
      A.2. Overview ..................................................11
      A.3. Procedures ................................................12
      A.4. Compatibility .............................................13

1.  Introduction

   GMPLS [RFC3473] introduced explicit support for bidirectional Label
   Switched Paths (LSPs).  The defined support matched the switching
   technologies covered by GMPLS, notably Time Division Multiplexing
   (TDM) and lambdas; specifically, it only supported bidirectional LSPs
   with symmetric bandwidth allocation.  Symmetric bandwidth
   requirements are conveyed using the semantics objects defined in
   [RFC2205] and [RFC2210].

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   Recent work ([GMPLS-PBBTE] and [MEF-TRAFFIC]) has looked at extending
   GMPLS to control Ethernet switching.  In this context, there has been
   discussion of the support of bidirectional LSPs with asymmetric
   bandwidth.  (That is, bidirectional LSPs that have different
   bandwidth reservations in each direction.)  This discussion motivated
   the extensions defined in this document, which may be used with any
   switching technology to signal asymmetric bandwidth bidirectional
   LSPs.  The procedures described in this document are experimental.

1.1.  Background

   Bandwidth parameters are transported within RSVP ([RFC2210],
   [RFC3209], and [RFC3473]) via several objects that are opaque to
   RSVP.  While opaque to RSVP, these objects support a particular model
   for the communication of bandwidth information between an RSVP
   session sender (ingress) and receiver (egress).  The original model
   of communication, defined in [RFC2205] and maintained in [RFC3209],
   used the SENDER_TSPEC and ADSPEC objects in Path messages and the
   FLOWSPEC object in Resv messages.  The SENDER_TSPEC object was used
   to indicate a sender's data generation capabilities.  The FLOWSPEC
   object was issued by the receiver and indicated the resources that
   should be allocated to the associated data traffic.  The ADSPEC
   object was used to inform the receiver and intermediate hops of the
   actual resources allocated for the associated data traffic.

   With the introduction of bidirectional LSPs in [RFC3473], the model
   of communication of bandwidth parameters was implicitly changed.  In
   the context of [RFC3473] bidirectional LSPs, the SENDER_TSPEC object
   indicates the desired resources for both upstream and downstream
   directions.  The FLOWSPEC object is simply confirmation of the
   allocated resources.  The definition of the ADSPEC object is either
   unmodified and only has meaning for downstream traffic, or is
   implicitly or explicitly ([RFC4606] and [MEF-TRAFFIC]) irrelevant.

1.2.  Approach Overview

   The approach for supporting asymmetric bandwidth bidirectional LSPs
   defined in this document builds on the original RSVP model for the
   transport of traffic-related parameters and GMPLS's support for
   bidirectional LSPs.  An alternative approach was considered and
   rejected in favor of the more generic approach presented below.  For
   reference purposes only, the rejected approach is summarized in
   Appendix A.

   The defined approach is generic and can be applied to any switching
   technology supported by GMPLS.  With this approach, the existing
   SENDER_TSPEC, ADSPEC, and FLOWSPEC objects are complemented with the
   addition of new UPSTREAM_TSPEC, UPSTREAM_ADSPEC, and

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   UPSTREAM_FLOWSPEC objects.  The existing objects are used in the
   original fashion defined in [RFC2205] and [RFC2210], and refer only
   to traffic associated with the LSP flowing in the downstream
   direction.  The new objects are used in exactly the same fashion as
   the old objects, but refer to the upstream traffic flow.  Figure 1
   shows the bandwidth-related objects used for asymmetric bandwidth
   bidirectional LSPs.

                        |---|        Path        |---|
                        | I |------------------->| E |
                        | n | -SENDER_TSPEC      | g |
                        | g | -ADSPEC            | r |
                        | r | -UPSTREAM_FLOWSPEC | e |
                        | e |                    | s |
                        | s |        Resv        | s |
                        | s |<-------------------|   |
                        |   | -FLOWSPEC          |   |
                        |   | -UPSTREAM_TSPEC    |   |
                        |   | -UPSTREAM_ADSPEC   |   |
                        |---|                    |---|

         Figure 1: Generic Asymmetric Bandwidth Bidirectional LSPs

   The extensions defined in this document are limited to Point-to-Point
   (P2P) LSPs.  Support for Point-to-Multipoint (P2MP) bidirectional
   LSPs is not currently defined and, as such, not covered in this
   document.

1.3.  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 [RFC2119].

2.  Generalized Asymmetric Bandwidth Bidirectional LSPs

   The setup of an asymmetric bandwidth bidirectional LSP is signaled
   using the bidirectional procedures defined in [RFC3473] together with
   the inclusion of the new UPSTREAM_FLOWSPEC, UPSTREAM_TSPEC, and
   UPSTREAM_ADSPEC objects.

   The new upstream objects carry the same information and are used in
   the same fashion as the existing downstream objects; they differ in
   that they relate to traffic flowing in the upstream direction while
   the existing objects relate to traffic flowing in the downstream
   direction.  The new objects also differ in that they are used on
   messages in the opposite directions.

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2.1.  UPSTREAM_FLOWSPEC Object

   The format of an UPSTREAM_FLOWSPEC object is the same as a FLOWSPEC
   object.  This includes the definition of class types and their
   formats.  The class number of the UPSTREAM_FLOWSPEC object is 120 (of
   the form 0bbbbbbb).

2.1.1.  Procedures

   The Path message of an asymmetric bandwidth bidirectional LSP MUST
   contain an UPSTREAM_FLOWSPEC object and MUST use the bidirectional
   LSP formats and procedures defined in [RFC3473].  The C-Type of the
   UPSTREAM_FLOWSPEC object MUST match the C-Type of the SENDER_TSPEC
   object used in the Path message.  The contents of the
   UPSTREAM_FLOWSPEC object MUST be constructed using a format and
   procedures consistent with those used to construct the FLOWSPEC
   object that will be used for the LSP, e.g., [RFC2210] or [RFC4328].

   Nodes processing a Path message containing an UPSTREAM_FLOWSPEC
   object MUST use the contents of the UPSTREAM_FLOWSPEC object in the
   upstream label and the resource allocation procedure defined in
   Section 3.1 of [RFC3473].  Consistent with [RFC3473], a node that is
   unable to allocate a label or internal resources based on the
   contents of the UPSTREAM_FLOWSPEC object MUST issue a PathErr message
   with a "Routing problem/MPLS label allocation failure" indication.

2.2.  UPSTREAM_TSPEC Object

   The format of an UPSTREAM_TSPEC object is the same as a SENDER_TSPEC
   object.  This includes the definition of class types and their
   formats.  The class number of the UPSTREAM_TSPEC object is 121 (of
   the form 0bbbbbbb).

2.2.1.  Procedures

   The UPSTREAM_TSPEC object describes the traffic flow that originates
   at the egress.  The UPSTREAM_TSPEC object MUST be included in any
   Resv message that corresponds to a Path message containing an
   UPSTREAM_FLOWSPEC object.  The C-Type of the UPSTREAM_TSPEC object
   MUST match the C-Type of the corresponding UPSTREAM_FLOWSPEC object.
   The contents of the UPSTREAM_TSPEC object MUST be constructed using a
   format and procedures consistent with those used to construct the
   FLOWSPEC object that will be used for the LSP, e.g., [RFC2210] or
   [RFC4328].  The contents of the UPSTREAM_TSPEC object MAY differ from
   contents of the UPSTREAM_FLOWSPEC object based on application data
   transmission requirements.

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   When an UPSTREAM_TSPEC object is received by an ingress, the ingress
   MAY determine that the original reservation is insufficient to
   satisfy the traffic flow.  In this case, the ingress MAY issue a Path
   message with an updated UPSTREAM_FLOWSPEC object to modify the
   resources requested for the upstream traffic flow.  This modification
   might require the LSP to be re-routed, and in extreme cases might
   result in the LSP being torn down when sufficient resources are not
   available.

2.3.  UPSTREAM_ADSPEC Object

   The format of an UPSTREAM_ADSPEC object is the same as an ADSPEC
   object.  This includes the definition of class types and their
   formats.  The class number of the UPSTREAM_ADSPEC object is 122 (of
   the form 0bbbbbbb).

2.3.1.  Procedures

   The UPSTREAM_ADSPEC object MAY be included in any Resv message that
   corresponds to a Path message containing an UPSTREAM_FLOWSPEC object.
   The C-Type of the UPSTREAM_TSPEC object MUST be consistent with the
   C-Type of the corresponding UPSTREAM_FLOWSPEC object.  The contents
   of the UPSTREAM_ADSPEC object MUST be constructed using a format and
   procedures consistent with those used to construct the ADSPEC object
   that will be used for the LSP, e.g., [RFC2210] or [MEF-TRAFFIC].  The
   UPSTREAM_ADSPEC object is processed using the same procedures as the
   ADSPEC object and, as such, MAY be updated or added at transit nodes.

3.  Packet Formats

   This section presents the RSVP message-related formats as modified by
   this section.  This document modifies formats defined in [RFC2205],
   [RFC3209], and [RFC3473].  See [RSVP-BNF] for the syntax used by
   RSVP.  Unmodified formats are not listed.  Three new objects are
   defined in this section:

      Object name            Applicable RSVP messages
      ---------------        ------------------------
      UPSTREAM_FLOWSPEC      Path, PathTear, PathErr, and Notify
                                 (via sender descriptor)
      UPSTREAM_TSPEC         Resv, ResvConf, ResvTear, ResvErr, and
                                 Notify (via flow descriptor list)
      UPSTREAM_ADSPEC        Resv, ResvConf, ResvTear, ResvErr, and
                                 Notify (via flow descriptor list)

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   The format of the sender description for bidirectional asymmetric
   LSPs is:

      <sender descriptor> ::=  <SENDER_TEMPLATE> <SENDER_TSPEC>
                               [ <ADSPEC> ]
                               [ <RECORD_ROUTE> ]
                               [ <SUGGESTED_LABEL> ]
                               [ <RECOVERY_LABEL> ]
                               <UPSTREAM_LABEL>
                               <UPSTREAM_FLOWSPEC>

   The format of the flow descriptor list for bidirectional asymmetric
   LSPs is:

      <flow descriptor list> ::= <FF flow descriptor list>
                               | <SE flow descriptor>

      <FF flow descriptor list> ::= <FLOWSPEC>
                               <UPSTREAM_TSPEC> [ <UPSTREAM_ADSPEC> ]
                               <FILTER_SPEC>
                               <LABEL> [ <RECORD_ROUTE> ]
                               | <FF flow descriptor list>
                               <FF flow descriptor>

      <FF flow descriptor> ::= [ <FLOWSPEC> ]
                               [ <UPSTREAM_TSPEC>] [ <UPSTREAM_ADSPEC> ]
                               <FILTER_SPEC> <LABEL>
                               [ <RECORD_ROUTE> ]

      <SE flow descriptor> ::= <FLOWSPEC>
                               <UPSTREAM_TSPEC> [ <UPSTREAM_ADSPEC> ]
                               <SE filter spec list>

      <SE filter spec list> is unmodified by this document.

4.  Compatibility

   This extension reuses and extends semantics and procedures defined in
   [RFC2205], [RFC3209], and [RFC3473] to support bidirectional LSPs
   with asymmetric bandwidth.  To indicate the use of asymmetric
   bandwidth, three new objects are defined.  Each of these objects is
   defined with class numbers in the form 0bbbbbbb.  Per [RFC2205],
   nodes not supporting this extension will not recognize the new class
   numbers and should respond with an "Unknown Object Class" error.  The
   error message will propagate to the ingress, which can then take
   action to avoid the path with the incompatible node or may simply
   terminate the session.

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5.  IANA Considerations

   IANA has assigned new values for namespaces defined in this section
   and reviewed in this subsection.

   The IANA has made the assignments described below in the "Class
   Names, Class Numbers, and Class Types" section of the "RSVP
   PARAMETERS" registry.

5.1.  UPSTREAM_FLOWSPEC Object

   A new class named UPSTREAM_FLOWSPEC has been created in the 0bbbbbbb
   range (120) with the following definition:

      Class Types or C-types:

      Same values as FLOWSPEC object (C-Num 9)

5.2.  UPSTREAM_TSPEC Object

   A new class named UPSTREAM_TSPEC has been created in the 0bbbbbbb
   range (121) with the following definition:

      Class Types or C-types:

      Same values as SENDER_TSPEC object (C-Num 12)

5.3.  UPSTREAM_ADSPEC Object

   A new class named UPSTREAM_ADSPEC has been created in the 0bbbbbbb
   range (122) with the following definition:

      Class Types or C-types:

      Same values as ADSPEC object (C-Num 13)

6.  Security Considerations

   This document introduces new message objects for use in GMPLS
   signaling [RFC3473] -- specifically the UPSTREAM_TSPEC,
   UPSTREAM_ADSPEC, and UPSTREAM_FLOWSPEC objects.  These objects
   parallel the exiting SENDER_TSPEC, ADSPEC, and FLOWSPEC objects but
   are used in the opposite direction.  As such, any vulnerabilities
   that are due to the use of the old objects now apply to messages
   flowing in the reverse direction.

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   From a message standpoint, this document does not introduce any new
   signaling messages or change the relationship between LSRs that are
   adjacent in the control plane.  As such, this document introduces no
   additional message- or neighbor-related security considerations.

   See [RFC3473] for relevant security considerations, and [SEC-
   FRAMEWORK] for a more general discussion on RSVP-TE security
   discussions.

7.  References

7.1.  Normative References

   [RFC2205]       Braden, R., Ed., Zhang, L., Berson, S., Herzog, S.,
                   and S. Jamin, "Resource ReSerVation Protocol (RSVP)
                   -- Version 1 Functional Specification", RFC 2205,
                   September 1997.

   [RFC2210]       Wroclawski, J., "The Use of RSVP with IETF Integrated
                   Services", RFC 2210, September 1997.

   [RFC2119]       Bradner, S., "Key words for use in RFCs to Indicate
                   Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC3209]       Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan,
                   V., and G. Swallow, "RSVP-TE: Extensions to RSVP for
                   LSP Tunnels", RFC 3209, December 2001.

   [RFC3473]       Berger, L., Ed., "Generalized Multi-Protocol Label
                   Switching (GMPLS) Signaling Resource ReserVation
                   Protocol-Traffic Engineering (RSVP-TE) Extensions",
                   RFC 3473, January 2003.

7.2.  Informative References

   [GMPLS-PBBTE]   Fedyk, D., et al "GMPLS Control of Ethernet", Work in
                   Progress, July 2008.

   [MEF-TRAFFIC]   Papadimitriou, D., "MEF Ethernet Traffic Parameters,"
                   Work in Progress, October 2008.

   [RFC4606]       Mannie, E. and D. Papadimitriou, "Generalized Multi-
                   Protocol Label Switching (GMPLS) Extensions for
                   Synchronous Optical Network (SONET) and Synchronous
                   Digital Hierarchy (SDH) Control", RFC 4606, August
                   2006.

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   [RFC4328]       Papadimitriou, D., Ed., "Generalized Multi-Protocol
                   Label Switching (GMPLS) Signaling Extensions for
                   G.709 Optical Transport Networks Control", RFC 4328,
                   January 2006.

   [RSVP-BNF]      Farrel, A. "Reduced Backus-Naur Form (RBNF) A Syntax
                   Used in Various Protocol Specifications", Work in
                   Progress, November 2008.

   [SEC-FRAMEWORK] Fang, L., Ed., "Security Framework for MPLS and GMPLS
                   Networks", Work in Progress, November 2008.

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A.  Appendix A: Alternate Approach Using ADSPEC Object

   This section is included for historic purposes and its implementation
   is NOT RECOMMENDED.

A.1.  Applicability

   This section presents an alternate method for the support of
   asymmetric bandwidth bidirectional LSP establishment with a single
   RSVP-TE signaling session.  This approach differs in applicability
   and generality from the approach presented in the main body of this
   document.  In particular, this approach is technology-specific; it
   uses the ADSPEC object to carry traffic parameters for upstream data
   and requires the Metro Ethernet Forum (MEF) Ethernet Traffic
   Parameter, while the approach presented above is suitable for use
   with any technology.

   The generalized asymmetric bandwidth bidirectional LSP presented in
   the main body of this document has the benefit of being applicable to
   any switching technology, but requires support for three new types of
   object classes, i.e., the UPSTREAM_TSPEC, UPSTREAM_ADSPEC, and
   UPSTREAM_FLOWSPEC objects.

   The solution presented in this section is based on the
    Ethernet-specific ADSPEC object, and is referred to as the "ADSPEC
   Object" approach.  This approach limits applicability to cases where
   the [MEF-TRAFFIC] traffic parameters are appropriate, and to
   switching technologies that define no use for the ADSPEC object.
   While ultimately it is this limited scope that has resulted in this
   approach being relegated to an Appendix, the semantics of this
   approach are quite simple in that they only require the definition of
   a new ADSPEC object C-Type.

   In summary, the "ADSPEC Object" approach presented in this section
   SHOULD NOT be implemented.

A.2.  Overview

   The "ADSPEC Object" approach is specific to Ethernet and uses [MEF-
   TRAFFIC] traffic parameters.  This approach is not generic and is
   aimed at providing asymmetric bandwidth bidirectional LSPs for just
   Ethernet transport.  With this approach, the ADSPEC object carries
   the traffic parameters for the upstream data flow.  SENDER_TSPEC
   object is used to indicate the traffic parameters for the downstream
   data flow.  The FLOWSPEC object provides confirmation of the
   allocated downstream resources.  Confirmation of the upstream
   resource allocation is a Resv message, as any resource allocation

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   failure for the upstream direction will always result in a PathErr
   message.  Figure 2 shows the bandwidth-related objects used in the
   first approach.

                            |---|        Path      |---|
                            | I |----------------->| E |
                            | n | -SENDER_TSPEC    | g |
                            | g | -ADSPEC          | r |
                            | r |                  | e |
                            | e |        Resv      | s |
                            | s |<-----------------| s |
                            | s | -FLOWSPEC        |   |
                            |---|                  |---|

   Figure 2: Asymmetric Bandwidth Bidirectional LSPs Using ADSPEC Object

   In the "ADSPEC Object" approach, the setup of an asymmetric bandwidth
   bidirectional LSP would be signaled using the bidirectional
   procedures defined in [RFC3473] together with the inclusion of a new
   ADSPEC object.  The new ADSPEC object would be specific to Ethernet
   and could be called the Ethernet Upstream Traffic Parameter ADSPEC
   object.  The Ethernet Upstream Traffic Parameter ADSPEC object would
   use the Class-Number 13 and C-Type UNASSIGNED (this approach should
   not be implemented).  The format of the object would be the same as
   the Ethernet SENDER_TSPEC object defined in [MEF-TRAFFIC].

   This approach would not modify behavior of symmetric bandwidth LSPs.
   Per [MEF-TRAFFIC], such LSPs are signaled either without an ADSPEC or
   with an INTSERV ADSPEC.

   The defined approach could be reused to support asymmetric bandwidth
   bidirectional LSPs for other types of switching technologies.  All
   that would be needed would be to define the proper ADSPEC object.

A.3.  Procedures

   Using the approach presented in this section, the process of
   establishing an asymmetric bandwidth bidirectional LSP would follow
   the process of establishing a symmetric bandwidth bidirectional LSP,
   as defined in Section 3 of [RFC3473], with two modifications.  These
   modifications would be followed when an incoming Path message is
   received containing an Upstream_Label object and the Ethernet
   Upstream Traffic Parameter ADSPEC object.

   The first modification to the symmetric bandwidth process would be
   that when allocating the upstream label, the bandwidth associated
   with the upstream label would be taken from the Ethernet Upstream
   Traffic Parameter ADSPEC object, see Section 3.1 of [RFC3473].

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   Consistent with [RFC3473], a node that is unable to allocate a label
   or internal resources based on the contents of the ADSPEC object,
   would issue a PathErr message with a "Routing problem/MPLS label
   allocation failure" indication.

   The second modification would be that the ADSPEC object would not be
   modified by transit nodes.

A.4.  Compatibility

   The approach presented in this section reuses semantics and
   procedures defined in [RFC3473].  To indicate the use of asymmetric
   bandwidth, a new ADSPEC object C-type would be defined.  Per
   [RFC2205], nodes not supporting the approach should not recognize
   this new C-type and respond with an "Unknown object C-Type" error.

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Authors' Addresses

   Lou Berger
   LabN Consulting, L.L.C.

   EMail: lberger@labn.net

   Attila Takacs
   Ericsson
   1. Laborc u.
   1037 Budapest, Hungary

   Phone: +36-1-4377044
   EMail: attila.takacs@ericsson.com

   Diego Caviglia
   Ericsson
   Via A. Negrone 1/A
   Genova-Sestri Ponente, Italy

   Phone: +390106003738
   EMail: diego.caviglia@ericsson.com

   Don Fedyk
   Nortel Networks
   600 Technology Park Drive
   Billerica, MA, USA 01821

   Phone: +1-978-288-3041
   EMail: dwfedyk@nortel.com

   Julien Meuric
   France Telecom
   Research & Development
   2, avenue Pierre Marzin
   22307 Lannion Cedex - France

   Phone: +33 2 96 05 28 28
   EMail: julien.meuric@orange-ftgroup.com

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