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Versions: 00 01

INTERNET-DRAFT                                               V. Govindan
Intended status: Proposed Standard                          M. Mudigonda
                                                              A. Sajassi
                                                           Cisco Systems
                                                               G. Mirsky
                                                                     ZTE
                                                             D. Eastlake
                                                                  Huawei
Expires: November 24, 2018                                  May 25, 2018


                   Fault Management for EVPN networks
                      draft-gmsm-bess-evpn-bfd-01


Abstract

   This document specifies a proactive, in-band network OAM mechanism to
   detect loss of continuity and miss-connection faults that affect
   unicast and multi-destination paths, used by Broadcast, unknown
   Unicast and Multicast traffic, in an EVPN network.  The mechanisms
   proposed in the draft use the widely adopted Bidirectional Forwarding
   Detection (BFD) protocol.


Status of this Memo

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

   Distribution of this document is unlimited. Comments should be sent
   to the authors or the BESSq working group mailing list:
   bess@ietf.org.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft
   Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.







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Table of Contents

      1. Introduction............................................3
      1.1 Terminology............................................3

      2. Scope of this Document..................................4
      3. Motivation for Running BFD at the EVPN Network Layer....4

      4. Fault Detection of Unicast Traffic......................6

      5. Fault Detection for BUM Traffic.........................7
      5.1 Ingress Replication....................................7
      5.2 Label Switched Multicast...............................7

      6. BFD Packet Encapsulation................................8
      6.1 Using GAL/G-ACh Encapsulation Without IP Headers.......8
      6.1.1 Ingress Replication..................................8
      6.1.1.1 Alternative Encapsulation Format...................8
      6.1.2 LSM (Label Switched Multicast).......................9
      6.1.3 Unicast..............................................9
      6.1.3.1 Alternative Encapsulation Format...................9
      6.2 Using IP Headers......................................10

      7. Scalability Considerations.............................11
      8. IANA Considerations....................................12
      9. Security Considerations................................13

      Normative References......................................14
      Informative References....................................15

      Authors' Addresses........................................17





















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1. Introduction

   [I-D.eastlake-bess-evpn-oam-req-frmwk] and [I-D.ooamdt-rtgwg-ooam-
   requirement] outline the OAM requirements of Ethernet VPN networks
   [RFC7432].  This document proposes mechanisms for proactive fault
   detection at the network (overlay) OAM layer of EVPN.  EVPN fault
   detection mechanisms need to consider unicast traffic separately from
   Broadcast, unknown Unicast, and Multicsst (BUM) traffic since they
   map to different FECs in EVPN, hence this document proposes different
   fault detection mechanisms to suit each type using the principles of
   [RFC5880], [RFC5884] and Point-to-multipoint BFD [I-D.ietf-bfd-
   multipoint] and [I-D.ietf-bfd-multipoint-active-tail]. Packet loss
   and packet delay measurement are out of scope for this document.



1.1 Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in BCP
   14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

   The following acronyms are used in this document.

      BUM - Broadcast, Unknown Unicast, and Multicast

      CC - Continuity Check

      CV - Connectivity Verification

      FEC - Forwarding Equivalency Class

      GAL - Generic Associated Channel Label

      LSM - Label Switched Multicast (P2MP)

      LSP - Label Switched Path

      MP2P - Multi-Point to Point

      OAM - Operations Administration, and Maintenance

      P2MP - Point to Multi-Point (LSM)

      PE - Provider Edge

      PHP - Penultimate Hop Popping



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2. Scope of this Document

   This document specifies proactive fault detection for EVPN [RFC7432]
   using BFD mechanisms for:

      o  Unicast traffic.

      o  BUM traffic using Multi-point-to-Point (MP2P) tunnels (ingress
         replication).

      o  BUM traffic using Point-to-Multipoint (P2MP) tunnels (LSM).

   This document does not discuss BFD mechanisms for:

      o  EVPN variants like PBB-EVPN [RFC7623].  This will be addressed
         in future versions.

      o  Integrated Routing and Bridging (IRB) solution based on EVPN
         [I-D.ietf-bess-evpn-inter-subnet-forwarding].  This will be
         addressed in future versions.

      o  EVPN using other encapsulations like VxLAN, NVGRE and MPLS over
         GRE [RFC8365].

      o  BUM traffic using MP2MP tunnels will also be addressed in a
         future version of this document.

   This specification describes procedures only for BFD asynchronous
   mode.  BFD demand mode is outside the scope of this specification.
   Further, the use of the Echo function is outside the scope of this
   specification.



3. Motivation for Running BFD at the EVPN Network Layer

   The choice of running BFD at the network layer of the OAM model for
   EVPN [I-D.eastlake-bess-evpn-oam-req-frmwk] and [I-D.ooamdt-rtgwg-
   ooam-requirement] was made after considering the following:

   o  In addition to detecting link failures in the EVPN network, BFD
      sessions at the network layer can be used to monitor the
      successful programming of labels used for setting up MP2P and P2MP
      EVPN tunnels transporting Unicast and BUM traffic.  The scope of
      reachability detection covers the ingress and the egress EVPN PE
      nodes and the network connecting them.

   o  Monitoring a representative set of path(s) or a particular path
      among the multiple paths available between two EVPN PE nodes could
      be done by exercising the entropy labels when they are used.


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      However paths that cannot be realized by entropy variations cannot
      be monitored.  Fault monitoring requirements outlined by [I-
      D.eastlake-bess-evpn-oam-req-frmwk] are addressed by the
      mechanisms proposed by this draft.

   Successful establishment and maintenance of BFD sessions between EVPN
   PE nodes does not fully guarantee that the EVPN service is
   functioning.  For example, an egress EVPN-PE can understand the EVPN
   label but could switch data to incorrect interface.  However, once
   BFD sessions in the EVPN Network Layer reach UP state, it does
   provide additional confidence that data transported using those
   tunnels will reach the expected egress node.  When the BFD session in
   EVPN overlay goes down that can be used as an indication of a Loss-
   of-Connectivity defect in the EVPN underlay that would cause EVPN
   service failure.





































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4. Fault Detection of Unicast Traffic

   The mechanisms specified in BFD for MPLS LSPs [RFC5884] [RFC7726] can
   be applied to bootstrap and maintain BFD sessions for unicast EVPN
   traffic.  The discriminators required for de-multiplexing the BFD
   sessions MUST be exchanged using EVPN LSP ping specifying the Unicast
   EVPN FEC [I-D.jain-bess-evpn-lsp-ping] before establishing the BFD
   session.  This is needed since the MPLS label stack does not contain
   enough information to disambiguate the sender of the packet.

   The usage of MPLS entropy labels takes care of the requirement to
   monitor various paths of the multi-path server layer network
   [RFC6790].  Each unique realizable path between the participating PE
   routers MAY be monitored separately when entropy labels are used.
   The multi-path connectivity between two PE routers MUST be tracked by
   at least one representative BFD session, but in that case the
   granularity of fault-detection would be coarser.  The PE node
   receiving the EVPN LSP ping MUST allocate BFD discriminators using
   the procedures defined in [RFC7726].  Once the BFD session for the
   EVPN label is UP, the ends of the BFD session MUST NOT change the
   local discriminator values of the BFD Control packets they generate,
   unless they first brings down the session as specified in [RFC5884].






























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5. Fault Detection for BUM Traffic



5.1 Ingress Replication

   Ingress replication uses separate MP2P tunnels for transporting BUM
   traffic from the ingress PE (head) to a set of one or more egress PEs
   (tails).  The fault detection mechanism specified by this document
   takes advantage of the fact that a unique copy is made by the head
   for each tail.  Another key aspect to be considered in EVPN is the
   advertisement of the inclusive multicast route.  The BUM traffic
   flows from a head node to a particular tail only after the head
   receives the inclusive multicast route containing the BUM EVPN label
   (downstream allocated) corresponding to the MP2P tunnel.

   The head-end PE performing ingress replication MUST initiate an EVPN
   LSP ping using the inclusive multicast FEC [I-D.jain-bess-evpn-lsp-
   ping] upon receiving an inclusive multicast route from a tail to
   bootstrap the BFD session.  There MAY exist multiple BFD sessions
   between a head PE an individual tail due to the usage of entropy
   labels [RFC6790] for an inclusive multicast FEC.  The PE node
   receiving the EVPN LSP ping MUST allocate BFD discriminators using
   the procedures defined in [RFC7726].  Once the BFD session for the
   EVPN label is UP, the ends of the BFD session MUST NOT change the
   local discriminator values of the BFD Control packets they generate,
   unless they first brings down the session as specified in [RFC5884].



5.2 Label Switched Multicast

   Fault detection for BUM traffic distributed by a Label Switched
   Multicst (LSM) using a P2MP tunnel is done with active tail
   multipoint BFD in the reliable head notification scenario (see [I-
   D.ietf-bfd-multipoint] and [I-D.ietf-bfd-multipoint-active-tail]
   particularly Section 3.4).

   TBD...













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6. BFD Packet Encapsulation



6.1 Using GAL/G-ACh Encapsulation Without IP Headers

   This section describes use of the Generic Associated Channel Label
   (GAL/G-ACh).



6.1.1 Ingress Replication

   The packet contains the following labels: LSP label (transport) when
   not using PHP (Penultimate Hop Popping), the optional entropy label,
   the BUM label and the SH label [RFC7432] (where applicable).  The G-
   ACh type is set to TBD1.  The G-Ach payload of the packet MUST
   contain the L2 header (in overlay space) followed by the IP header
   encapsulating the BFD packet.  The MAC address of the inner packet is
   used to validate the <EVI, MAC> in the receiving node.  The
   discriminator values of BFD are obtained through negotiation through
   the out-of-band EVPN LSP ping.



6.1.1.1 Alternative Encapsulation Format

   A new TLV can be defined as proposed in Sec 3 of [RFC6428] to include
   the EVPN FEC information as a TLV following the BFD Control packet.

   The format of the TLV can be reused from the EVPN Inclusive Multicast
   sub-TLV proposed by Fig 2 of [I-D.jain-bess-evpn-lsp-ping].

   A new type (TBD3) to indicate the EVPN Inclusive Multicast SubTLV is
   requested from the "CC/ CV MEP-ID TLV" registry [RFC6428].

















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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 1|Version|     Flags     |       BFD CV Code Point TBD2  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     ~                  BFD Control Packet                           ~
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     ~               EVPN Inclusive Multicast TLV                    ~
     |                 (Type = TBD3)                                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

             Figure 1: BFD-EVPN CV Message for EVPN Multicast
                                  (Ingress Replication)



6.1.2 LSM (Label Switched Multicast)

   TBD...



6.1.3 Unicast

   The packet contains the following labels: LSP label (transport) when
   not using PHP, the optional entropy label and the EVPN Unicast label.
   The G-ACh type is set to TBD1.  The G-Ach payload of the packet MUST
   contain the L2 header (in overlay space) followed by the IP header
   encapsulating the BFD packet.  The MAC address of the inner packet is
   used to validate the <EVI, MAC> in the receiving node.  The
   discriminator values for BFD are obtained through negotiation using
   the out-of-band EVPN ping.



6.1.3.1 Alternative Encapsulation Format

   A new TLV can be defined as proposed in Sec 3 of [RFC6428] to include
   the EVPN FEC information as a TLV following the BFD Control packet.
   The format of the TLV can be reused from the EVPN MAC sub-TLV
   proposed by Figure 1 of [I-D.jain-bess-evpn-lsp-ping].  A new type
   (TBD4) to indicate the EVPN MAC SubTLV is requested from the "CC/ CV
   MEP-ID TLV" registry [RFC6428].






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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |0 0 0 1|Version|     Flags     |       BFD CV Code Point TBD2  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     ~                  BFD Control Packet                           ~
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     ~                           EVPN MAC Sub TLV                    ~
     |                 (Type = TBD4)                                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 2: BFD-EVPN CV Message for EVPN Unicast



6.2 Using IP Headers

   The encapsulation option using IP headers will not be suited for
   EVPN, as using different values in the destination IP address for
   data and OAM (BFD) packets could cause the BFD packets to follow a
   different path than that of data packets.  Hence this option MUST NOT
   be used for EVPN.



























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7. Scalability Considerations

   The mechanisms proposed by this draft could affect the packet load on
   the network and its elements especially when supporting
   configurations involving a large number of EVIs.  The option of
   slowing down or speeding up BFD timer values can be used by an
   administrator or a network management entity to maintain the overhead
   incurred due to fault monitoring at an acceptable level.












































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8. IANA Considerations

   IANA is requested to assign two channel types from the "Pseudowire
   Associated Channel Types" registry in [RFC4385] as follows.

         Value   Description   Reference
         -----   -----------   ------------
         TBD1    EFD-EVPN CC   [this document]
         TBD2    BFD-EVPN CV   [this document]

   Ed Note: Do we need a CC code point?  TBD

   IANA is requested to assign the following code-points from the "CC/CV
   MEP-ID TLV" registry [RFC6428].


         Value    Name                       Reference
         -----   ------------------------   ---------------
         TBD3    EVPN inclusive multicast   [this document]
         TBD4    EVPN unicast               [this document]
































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9. Security Considerations

   Security considerations discussed in [RFC5880], [RFC5883], and
   [RFC8029] apply.

   MPLS security considerations [RFC5920] apply to BFD Control packets
   encapsulated in a MPLS label stack. When BPD Control packets are
   routed, the authentication considerations discussed in [RFC5883]
   should be followed.











































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Normative References

   [I-D.ietf-bess-evpn-inter-subnet-forwarding] Sajassi, A., Salam, S.,
             Thoria, S., Rekhter, Y., Drake, J., Yong, L., and L.
             Dunbar, "Integrated Routing and Bridging in EVPN", draft-
             ietf-bess-evpn-inter-subnet-forwarding-03 (work in
             progress), October 2015.

   [I-D.ietf-bfd-multipoint] Katz, D., Ward, D., and J. Networks, "BFD
             for Multipoint Networks", draft-ietf-bfd-multipoint-16
             (work in progress), April 2016.

   [I-D.ietf-bfd-multipoint-active-tail] Katz, D., Ward, D., and J.
             Networks, "BFD Multipoint Active Tails.", draft-ietf-bfd-
             multipoint-active-tail-07 (work in progress), May 2016.

   [I-D.jain-bess-evpn-lsp-ping] Jain, P., Boutros, S., and S. Salam,
             "LSP-Ping Mechanisms for EVPN and PBB-EVPN", draft-jain-
             bess-evpn-lsp-ping-06 (work in progress), May 2016.

   [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
             Requirement Levels", BCP 14, RFC 2119, DOI
             10.17487/RFC2119, March 1997, <http://www.rfc-
             editor.org/info/rfc2119>.

   [RFC4385] 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, DOI 10.17487/RFC4385,
             February 2006, <http://www.rfc-editor.org/info/rfc4385>.

   [RFC5880] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
             (BFD)", RFC 5880, DOI 10.17487/RFC5880, June 2010,
             <http://www.rfc-editor.org/info/rfc5880>.

   [RFC5883] Katz, D. and D. Ward, "Bidirectional Forwarding Detection
             (BFD) for Multihop Paths", RFC 5883, DOI 10.17487/RFC5883,
             June 2010, <https://www.rfc-editor.org/info/rfc5883>.

   [RFC5884] Aggarwal, R., Kompella, K., Nadeau, T., and G. Swallow,
             "Bidirectional Forwarding Detection (BFD) for MPLS Label
             Switched Paths (LSPs)", RFC 5884, DOI 10.17487/RFC5884,
             June 2010, <http://www.rfc-editor.org/info/rfc5884>.

   [RFC6425] Saxena, S., Ed., Swallow, G., Ali, Z., Farrel, A.,
             Yasukawa, S., and T. Nadeau, "Detecting Data-Plane Failures
             in Point-to-Multipoint MPLS - Extensions to LSP Ping", RFC
             6425, DOI 10.17487/RFC6425, November 2011,
             <https://www.rfc-editor.org/info/rfc6425>.




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   [RFC6428] Allan, D., Ed., Swallow, G., Ed., and J. Drake, Ed.,
             "Proactive Connectivity Verification, Continuity Check, and
             Remote Defect Indication for the MPLS Transport Profile",
             RFC 6428, DOI 10.17487/RFC6428, November 2011,
             <http://www.rfc-editor.org/info/rfc6428>.

   [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and L.
             Yong, "The Use of Entropy Labels in MPLS Forwarding", RFC
             6790, DOI 10.17487/RFC6790, November 2012, <http://www.rfc-
             editor.org/info/rfc6790>.

   [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A.,
             Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based
             Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February
             2015, <http://www.rfc-editor.org/info/rfc7432>.

   [RFC7623] Sajassi, A., Ed., Salam, S., Bitar, N., Isaac, A., and W.
             Henderickx, "Provider Backbone Bridging Combined with
             Ethernet VPN (PBB-EVPN)", RFC 7623, DOI 10.17487/RFC7623,
             September 2015, <http://www.rfc-editor.org/info/rfc7623>.

   [RFC7726] Govindan, V., Rajaraman, K., Mirsky, G., Akiya, N., and S.
             Aldrin, "Clarifying Procedures for Establishing BFD
             Sessions for MPLS Label Switched Paths (LSPs)", RFC 7726,
             DOI 10.17487/RFC7726, January 2016, <http://www.rfc-
             editor.org/info/rfc7726>.

   [RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
             Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
             Switched (MPLS) Data-Plane Failures", RFC 8029, DOI
             10.17487/RFC8029, March 2017, <https://www.rfc-
             editor.org/info/rfc8029>.

   [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119
             Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May
             2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8365] Sajassi, A., Ed., Drake, J., Ed., Bitar, N., Shekhar, R.,
             Uttaro, J., and W. Henderickx, "A Network Virtualization
             Overlay Solution Using Ethernet VPN (EVPN)", RFC 8365, DOI
             10.17487/RFC8365, March 2018, <https://www.rfc-
             editor.org/info/rfc8365>.



Informative References

   [I-D.ooamdt-rtgwg-ooam-requirement] Kumar, N., Pignataro, C., Kumar,
             D., Mirsky, G., Chen, M., Nordmark, E., Networks, J., and
             D. Mozes, "Overlay OAM Requirements", draft-ooamdt-rtgwg-


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             ooam-requirement-02 (work in progress), March 2016.

   [I-D.eastlake-bess-evpn-oam-req-frmwk] Salam, S., Sajassi, A.,
             Aldrin, S., and J. Drake, "EVPN Operations, Administration
             and Maintenance Requirements and Framework", draft-
             eastlake-bess-evpn-oam-req-frmwk-00 (work in progress), May
             2018.

   [RFC5920] Fang, L., Ed., "Security Framework for MPLS and GMPLS
             Networks", RFC 5920, DOI 10.17487/RFC5920, July 2010,
             <https://www.rfc-editor.org/info/rfc5920>.









































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Authors' Addresses


      Vengada Prasad Govindan
      Cisco Systems

      Email: venggovi@cisco.com


      Mudigonda Mallik
      Cisco Systems

      Email: mmudigon@cisco.com


      Ali Sajassi
      Cisco Systems
      170 West Tasman Drive
      San Jose, CA  95134, USA

      Email: sajassi@cisco.com


      Gregory Mirsky
      ZTE Corp.

      Email: gregimirsky@gmail.com


      Donald Eastlake, 3rd
      Huawei Technologies
      155 Beaver Street
      Milford, MA 01757 USA

      Phone: +1-508-333-2270
      Email: d3e3e3@gmail.com
















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