PBB-EVPN C-MAC flush: Flush Mechanism for Customer MAC Addresses Based on Service Instance Identifier (I-SID) in Provider Backbone Bridging EVPN (PBB-EVPN)

Internet Engineering Task Force (IETF)                   J. Rabadan, Ed.
Request for Comments: 9541                                  S. Sathappan
Category: Standards Track                                     K. Nagaraj
ISSN: 2070-1721                                                    Nokia
                                                               M. Miyake
                                                              T. Matsuda
                                                                Softbank
                                                              March 2024


  Flush Mechanism for Customer MAC Addresses Based on Service Instance
    Identifier (I-SID) in Provider Backbone Bridging EVPN (PBB-EVPN)

Abstract

   Provider Backbone Bridging (PBB) can be combined with Ethernet
   Virtual Private Networks (EVPNs) to deploy Ethernet Local Area
   Network (E-LAN) services in large Multiprotocol Label Switching
   (MPLS) networks.  That combination is what we refer to as "PBB-EVPN."
   Single-Active multihoming and per Service Instance Identifier (I-SID)
   load-balancing can be provided to access devices and aggregation
   networks.  In order to speed up the network convergence in case of
   failures on Single-Active multihomed Ethernet Segments (ESs), PBB-
   EVPN defines a flush mechanism for Customer MACs (C-MACs) called
   "C-MAC flush" that works for different Ethernet Segment Backbone MAC
   (B-MAC) address allocation models.  This document complements those
   C-MAC flush procedures for cases in which no PBB-EVPN ESs are defined
   (i.e., the attachment circuit is associated with a zero Ethernet
   Segment Identifier (ESI)) and the C-MAC flush requires I-SID-level
   granularity.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9541.

Copyright Notice

   Copyright (c) 2024 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction
     1.1.  Abbreviations
     1.2.  Terminology and Conventions
   2.  Solution Requirements
   3.  EVPN BGP Encoding for I-SID-Based C-MAC Flush
   4.  Solution Description
     4.1.  I-SID-Based C-MAC Flush Activation Procedures
     4.2.  C-MAC Flush Generation
     4.3.  C-MAC Flush Process upon Receiving a C-MAC Flush
           Notification
   5.  Conclusions
   6.  Security Considerations
   7.  IANA Considerations
   8.  References
     8.1.  Normative References
     8.2.  Informative References
   Acknowledgments
   Authors' Addresses

1.  Introduction

   [RFC7623] defines how Provider Backbone Bridging (PBB) can be
   combined with Ethernet Virtual Private Networks (EVPNs) to deploy
   E-LAN services in very large MPLS networks.  [RFC7623] also describes
   how Single-Active multihoming and per-I-SID load-balancing can be
   provided to access devices and aggregation networks.  When Access
   Ethernet and/or MPLS networks exist, [EVPN-VIRTUAL-ES] describes how
   virtual Ethernet Segments (ESs) can be associated with a group of
   Ethernet Virtual Circuits (EVCs) or even pseudowires (PWs).  In order
   to speed up the network convergence in case of failures on Single-
   Active multihomed ESs, [RFC7623] defines a Customer MAC flush
   mechanism that works for different ES B-MAC address allocation
   models.

   In some cases, the administrative entities that manage the access
   devices or aggregation networks do not demand multihomed ESs from the
   PBB-EVPN provider, but simply demand multiple single-homed ESs.
   Single-homed ESs use null ESIs, whereas multihomed ESs use non-null
   ESIs.  If using single-homed ESs, the PBB-EVPN network is no longer
   aware of the redundancy offered by the access administrative entity.
   Figure 1 shows an example where the PBB-EVPN network provides four
   different Attachment Circuits (ACs) for I-SID1, with those ACs not
   being part of any ES or virtual ES.  (Therefore, they are referred to
   as null virtual Ethernet Segments.)

   <----G.8032----><--PBB-EVPN Network-----><----MPLS---->
        Access          MPLS                Access
         Ring                               Network
   I-SID1      ESI +------+         +------+
   +----+      null| PE1  |---------| PE3  |
   |CE1 |----------|B-MAC1|         |B-MAC3| ESI null
   +----+    active|      |         |      |----+ PW
     |             +------+         +------+     \active
     |               |                 |          \  +----+
     |               |                 |           ==|CE3 |I-SID1
     |               |                 |          /  +----+
     |standby  ESI +------+         +------+     / PW
   +----+      null| PE2  |         | PE4  |----+ standby
   |CE2 |----------|B-MAC2|         |B-MAC4| ESI null
   +----+    active|      |---------|      |
   I-SID1          +------+         +------+

               Figure 1: PBB-EVPN and Non-ES-Based Redundancy

   In the example in Figure 1, CE1, CE2, and CE3 are attached to the
   same service, identified by I-SID1, in the PBB-EVPN PEs.  CE1 and CE2
   are connected to the PEs via "Ethernet ring protection switching" as
   specified in [G.8032], and their ACs to PE1 and PE2 are represented
   by a port and VLAN identifier.  CE3 is dual-homed to PE3 and PE4
   through an active/standby PW, and its AC to the PEs is represented by
   a PW.  Each of the four PEs uses a dedicated Backbone MAC address as
   a source MAC address (B-MAC1, B-MAC2, B-MAC3, and B-MAC4,
   respectively) when encapsulating customer frames in PBB packets and
   forwarding those PBB packets to the remote PEs as per [RFC7623].
   There are no multihomed ESs defined in the PBB-EVPN network of the
   example; that is why the four ACs in Figure 1 show the text "ESI
   null", which means the Ethernet Segment Identifier on those ACs is
   zero.  Since there are no multihomed ESs defined, the PEs keep their
   ACs active as long as the physical connectivity is established and
   the CEs are responsible for managing the redundancy, avoiding loops,
   and providing per-I-SID load-balancing to the PBB-EVPN network.
   Examples of CEs managing their own redundancy are described in
   [G.8032], or [RFC4762] for active/standby PWs.

   For instance, in normal conditions, CE2 will block its link to CE1
   and CE3 will block its forwarding path to PE4.  In this situation, a
   failure in one of the redundant ACs will trigger the CEs to start
   using their redundant paths; however, those failures will not trigger
   any C-MAC flush procedures in the PEs that implement [RFC7623], since
   the PEs are not using the PBB-EVPN multihoming procedures.  For
   example:

   *  If the active PW from CE3 (to PE3) fails and the failure is due to
      the entire PE3 node failing, then the procedures in [RFC7623]
      guarantee that all the remote PEs flush all the C-MACs associated
      with B-MAC3 (the B-MAC of PE3).  In this case, CE3 detects the
      fault due to the PW going operationally down.

   *  However, if the active PW from CE3 (to PE3) fails (but PE3 is
      still operationally up), following the procedures in [RFC7623],
      neither PE3 nor PE4 issue a C-MAC flush message.  Therefore, the
      remote PEs will continue pointing at PE3's B-MAC to reach CE3's
      C-MACs, until the C-MACs age out in the I-SID1 forwarding tables.
      In this case, PE3 may use any of the existing PW notifications so
      that CE3 switches the active PW to PE4.

   *  The same issue is exposed when the active PW from CE3 switches
      over from PE3 to PE4 due to a manual operation on CE3; that is,
      neither PE3 nor PE4 trigger any C-MAC flush notification and the
      remote PEs continue sending the traffic to PE3 until the C-MACs
      age out.

   [RFC7623] provides a C-MAC flush solution based on a shared B-MAC
   update along with the MAC Mobility extended community where the
   sequence number is incremented.  However, the procedure is only used
   along with multihomed ESs.  Even if that procedure could be used for
   null ESs, as in the example of Figure 1, the Customer MAC flush
   procedure in [RFC7623] would result in unnecessary flushing of
   unaffected I-SIDs on the remote PEs, and subsequent flooding of
   unknown unicast traffic in the network.  For instance, in the case
   that CE3 switches its active PW over to PE4, a potential solution
   reusing the existing C-MAC flush notifications in [RFC7623] is for
   PE3 to issue an update for the MAC/IP Advertisement route of B-MAC3
   with a higher sequence number.  However, this update would cause
   unnecessary Customer MAC flushing for all the I-SIDs attached to PE3
   (supposing multiple I-SIDs in PE3) rather than for only I-SID1.

   This document describes an extension of the Customer MAC flush
   procedures in [RFC7623], so that in the failure example above, PE3
   can trigger a Customer MAC flush notification that makes PE1, PE2,
   and PE4 flush all the Customer MACs associated with PE3's B-MAC3 and
   (only) I-SID1.  In order to do so, this specification introduces the
   encoding of the I-SID in the MAC/IP Advertisement routes advertised
   for the B-MACs.  The C-MAC flush procedure explained in this document
   is referred to as "PBB-EVPN I-SID-based C-MAC flush" and can be used
   in PBB-EVPN networks with null or non-null (virtual) ESs.

   This specification assumes that the reader is familiar with the
   procedures in [RFC7623].

1.1.  Abbreviations

   AC:  Attachment Circuit

   B-MAC:  Backbone MAC

   CE:  Customer Edge

   C-MAC:  Customer MAC

   ES:  Ethernet Segment

   ESI:  Ethernet Segment Identifier

   EVI:  EVPN Instance

   EVPN:  Ethernet Virtual Private Network (as in [RFC7432])

   I-SID:  Service Instance Identifier

   MAC:  Media Access Control

   MAC-VRF:  MAC Virtual Routing and Forwarding

   PBB-EVPN:  Provider Backbone Bridging and EVPN (as in [RFC7623])

   PE:  Provider Edge

1.2.  Terminology and Conventions

   Familiarity with the terminology in [RFC7623] is expected.

   B-MAC/0 route:  This is an EVPN MAC/IP Advertisement route that uses
      a B-MAC in the MAC address field and a zero Ethernet Tag ID.

   B-MAC/I-SID route:  This is an EVPN MAC/IP Advertisement route that
      uses a B-MAC in the MAC address field and an I-SID in the Ethernet
      Tag field.  It is used to notify remote PEs about the required
      C-MAC flush procedure for the C-MACs associated with the
      advertised B-MAC and I-SID.

   G.8032:  Refers to Ethernet ring protection switching as described in
      [G.8032].

   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.

2.  Solution Requirements

   The following requirements are followed by the C-MAC flush solution
   described in this document:

   a.  The solution MUST prevent packet-loss scenarios in case of
       failures on null ES ACs (Attachment Circuits not associated with
       an ES; that is, their corresponding ESI is zero) when the access
       device or access network is responsible for the redundancy.

   b.  This extension described in this document MUST work with Single-
       Active non-null ESs and virtual ESs, irrespective of the PE B-MAC
       address assignment (dedicated per-ES B-MAC or shared B-MAC, as in
       [RFC7623]).

   c.  In case of failure on the egress PE, the solution MUST provide a
       C-MAC flush notification at the B-MAC and I-SID granularity
       level.

   d.  The solution MUST provide a reliable C-MAC flush notification in
       PBB-EVPN networks that use Route Reflectors (RRs).  MAC flushing
       needs to be provided to all affected I-SIDs in spite of the BGP
       flush notification messages being aggregated at the RR.

   e.  The solution MUST coexist in [RFC7623] networks where there are
       PEs that do not support this specification.

   f.  The solution SHOULD be enabled or disabled by an administrative
       option on a per-PE and per-I-SID basis (as opposed to always
       being enabled for all the I-SIDs).

3.  EVPN BGP Encoding for I-SID-Based C-MAC Flush

   The solution does not use any new BGP attributes but reuses the MAC
   Mobility extended community as an indication of C-MAC flush (as in
   [RFC7623]) and encodes the I-SID in the Ethernet Tag field of the
   EVPN MAC/IP advertisement route.  As a reference, Figure 2 shows the
   MAC Mobility extended community and the EVPN MAC/IP advertisement
   route that are used as specified in [RFC7432] and used in this
   document as a C-MAC flush notification message.

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   | Type=0x06     | Sub-Type=0x03 |   Flags       |   Reserved=0  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                       Sequence Number                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

               +---------------------------------------+
               |  Route Distinguisher                  |
               +---------------------------------------+
               |  ESI = 0                              |
               +---------------------------------------+
               |  Ethernet Tag ID = I-SID              |
               +---------------------------------------+
               |  MAC Address Length = 48              |
               +---------------------------------------+
               |  B-MAC Address                        |
               +---------------------------------------+
               |  IP Address Length = 0                |
               +---------------------------------------+
               |  MPLS Label1                          |
               +---------------------------------------+

       Figure 2: C-MAC Flush Notification Encoding: B-MAC/I-SID Route

   Where:

   *  The route's route distinguisher and route targets are the ones
      corresponding to its EVI.  Alternatively to the EVI's Route Target
      (RT), the route MAY be tagged with an RT auto-derived from the
      Ethernet Tag (I-SID) instead.  [RFC7623] describes how the EVPN
      MAC/IP Advertisement routes can be advertised along with the EVI
      RT or an RT that is derived from the I-SID.

   *  The Ethernet Tag encodes the I-SID.  This indicates to the PE that
      it must flush the C-MACs for that encoded I-SID, upon reception of
      the route.

   *  The MAC address field encodes the B-MAC address.  This indicates
      to the PE that it must flush the C-MACs associated with that
      encoded B-MAC, upon reception of the route.

   *  The MAC Mobility extended community is used as in [RFC7623], where
      an increment in the sequence number between two updates for the
      same B-MAC/I-SID will be interpreted as a C-MAC flush notification
      for the corresponding B-MAC and I-SID.

   All the other fields are set and used as defined in [RFC7623].  This
   document will refer to this route as the "B-MAC/I-SID route", as
   opposed to the EVPN MAC/IP Advertisement route used in [RFC7623] that
   contains a specific B-MAC and the Ethernet Tag ID set to zero.  This
   document uses the term "B-MAC/0 route" to represent a B-MAC route
   advertised with an Ethernet Tag ID = 0.

   Note that this B-MAC/I-SID route will be accepted and reflected by
   any RR as specified in [RFC7432], since no new attributes or values
   are used.  A PE receiving the route will process the received B-MAC/
   I-SID update only in the case of supporting the procedures described
   in this document.

4.  Solution Description

   Figure 1 will be used in the description of the solution.  CE1, CE2,
   and CE3 are connected to ACs associated with I-SID1, where no
   (multihomed) ESs have been enabled, and the ACs and PWs are in active
   or standby state as per Figure 1.

   Enabling or disabling I-SID-based C-MAC flush SHOULD be an
   administrative choice on the system that MAY be configured per I-SID
   (I-Component, Service Instance Component), as opposed to being
   configured for all I-SIDs.  When enabled on a PE:

   a.  The PE will be able to generate B-MAC/I-SID routes as C-MAC Flush
       notifications for the remote PEs.

   b.  The PE will be able to process B-MAC/I-SID routes received from
       remote PEs.

   The PE MUST follow the procedures in [RFC7623] for C-MAC flush.  This
   specification provides some additional procedures when I-SID-based
   C-MAC flush is enabled.

   This C-MAC flush specification is described in three sets of
   procedures:

   *  I-SID-based C-MAC flush activation

   *  C-MAC flush notification generation upon AC failures

   *  C-MAC flush process upon receiving a C-MAC flush notification

4.1.  I-SID-Based C-MAC Flush Activation Procedures

   The following behavior MUST be followed by the PBB-EVPN PEs following
   this specification.  Figure 1 is used as a reference.

   *  As in [RFC7623], each PE advertises a shared B-MAC in a B-MAC/0
      route (with B-MAC1, B-MAC2, B-MAC3, and B-MAC4 in the MAC address
      field, respectively).  This is the B-MAC that each PE will use as
      B-MAC SA (Source Address) when encapsulating the frames received
      on any local single-homed AC.  Each PE will import the received
      B-MAC/0 routes from the remote PEs and will install the B-MACs in
      its B-component (Backbone Component) MAC-VRF.  For instance, PE1
      will advertise B-MAC1/0 and will install B-MAC2, B-MAC3, and
      B-MAC4 in its MAC-VRF.

   *  Assuming I-SID-based C-MAC flush is activated for I-SID1, the PEs
      will advertise the shared B-MAC with I-SID1 encoded in the
      Ethernet Tag. That is, PE1 will advertise B-MAC1/1 and will
      receive B-MAC2/1, B-MAC3/1, and B-MAC4/1.  The receiving PEs MUST
      use these B-MAC/I-SID routes only for C-MAC flush procedures and
      they MUST NOT be used to add/withdraw any B-MAC entry in the MAC-
      VRFs.  As per [RFC7623], only B-MAC/0 routes can be used to add/
      withdraw B-MACs in the MAC-VRFs.

   *  The above procedure MAY also be used for dedicated B-MACs (B-MACs
      allocated per ES).

4.2.  C-MAC Flush Generation

   If, for instance, there is a failure on PE1's AC, PE1 will generate
   an update including B-MAC1/1 along with the MAC Mobility extended
   community where the Sequence Number has been incremented.  The
   reception of the B-MAC1/1 with an increment in the sequence number
   will trigger the C-MAC flush procedures on the receiving PEs.

   *  An AC going operationally down MUST generate a B-MAC/I-SID with a
      higher Sequence Number.  If the AC going down makes the entire
      local I-SID go operationally down, the PE will withdraw the B-MAC/
      I-SID route for the I-SID.

   *  An AC going operationally up SHOULD NOT generate any B-MAC/I-SID
      update, unless it activates its corresponding I-SID, in which case
      the PE will advertise the B-MAC/I-SID route.

   *  An AC receiving a G.8032 flush notification or a flush message in
      any other protocol from the access network MAY propagate it to the
      remote PEs by generating a B-MAC/I-SID route update with a higher
      Sequence Number.

4.3.  C-MAC Flush Process upon Receiving a C-MAC Flush Notification

   A PE receiving a C-MAC flush notification will follow these
   procedures:

   *  A received B-MAC/I-SID route (with a non-zero I-SID) MUST NOT add/
      remove any B-MAC to/from the MAC-VRF.

   *  An update of a previously received B-MAC/I-SID route with an
      increment Sequence Number MUST flush all the C-MACs associated
      with that I-SID and B-MAC.  C-MACs associated with the same I-SID
      but different B-MAC MUST NOT be flushed.

   *  A received B-MAC/I-SID withdraw (with a non-zero I-SID) MUST flush
      all the C-MACs associated with that B-MAC and I-SID.

   Note that the C-MAC flush procedures described in [RFC7623] for
   B-MAC/0 routes are still valid and a PE receiving [RFC7623] C-MAC
   flush notification messages MUST observe the behavior specified in
   [RFC7623].

5.  Conclusions

   The I-SID-based C-MAC flush solution described in this document has
   the following benefits:

   a.  The solution solves packet-loss scenarios in case of failures on
       null ES ACs, since the C-MAC flush procedures are independent of
       the ES definition.

   b.  This extension can also be used with Single-Active non-null ESs
       and virtual ESs, irrespective of the PE B-MAC address assignment
       (dedicated per-ES B-MAC or shared B-MAC).

   c.  It provides a C-MAC flush notification at B-MAC and I-SID
       granularity level, therefore flushing a minimum number of C-MACs
       and reducing the amount of unknown unicast flooding in the
       network.

   d.  It provides a reliable C-MAC flush notification in PBB-EVPN
       networks that use RRs.  RRs will propagate the C-MAC flush
       notifications for all the affected I-SIDs, irrespective of the
       order in which the notifications make it to the RR.

   e.  The solution can coexist in a network with systems supporting or
       not supporting this specification.  Non-supporting systems ignore
       the B-MAC/I-SID routes; however, they still follow the C-MAC
       flush procedures in [RFC7623].

6.  Security Considerations

   Security considerations described in [RFC7623] apply to this
   document.

   In addition, this document suggests additional procedures that can be
   activated on a per I-SID basis and generate additional EVPN MAC/IP
   Advertisement routes in the network.  The format of these additional
   EVPN MAC/IP Advertisement routes is backwards compatible with the
   procedures in [RFC7623] and should not create any issues for
   receiving PEs that do not follow this specification.  However, the
   additional routes may consume extra memory and processing resources
   on the receiving PEs.  Because of that, it is RECOMMENDED to activate
   this feature only when necessary (when multihomed networks or devices
   are attached to the PBB-EVPN PEs), and not by default in any PBB-EVPN
   PE.

7.  IANA Considerations

   This document has no IANA actions.

8.  References

8.1.  Normative References

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

   [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, <https://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, <https://www.rfc-editor.org/info/rfc7623>.

   [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>.

8.2.  Informative References

   [EVPN-VIRTUAL-ES]
              Sajassi, A., Brissette, P., Schell, R., Drake, J., and J.
              Rabadan, "EVPN Virtual Ethernet Segment", Work in
              Progress, Internet-Draft, draft-ietf-bess-evpn-virtual-
              eth-segment-15, 28 February 2024,
              <https://datatracker.ietf.org/doc/html/draft-ietf-bess-
              evpn-virtual-eth-segment-15>.

   [G.8032]   ITU-T, "Ethernet ring protection switching", ITU-T
              Recommendation G.8032/Y.1344, March 2020,
              <https://www.itu.int/rec/T-REC-G.8032-202003-I/en>.

   [RFC4762]  Lasserre, M., Ed. and V. Kompella, Ed., "Virtual Private
              LAN Service (VPLS) Using Label Distribution Protocol (LDP)
              Signaling", RFC 4762, DOI 10.17487/RFC4762, January 2007,
              <https://www.rfc-editor.org/info/rfc4762>.

Acknowledgments

   The authors want to thank Vinod Prabhu, Sriram Venkateswaran, Laxmi
   Padakanti, and Ranganathan Boovaraghavan for their review and
   contributions.

Authors' Addresses

   Jorge Rabadan (editor)
   Nokia
   520 Almanor Avenue
   Sunnyvale, CA 94085
   United States of America
   Email: jorge.rabadan@nokia.com


   Senthil Sathappan
   Nokia
   520 Almanor Avenue
   Sunnyvale, CA 94085
   United States of America
   Email: senthil.sathappan@nokia.com


   Kiran Nagaraj
   Nokia
   520 Almanor Avenue
   Sunnyvale, CA 94085
   United States of America
   Email: kiran.nagaraj@nokia.com


   M. Miyake
   Softbank
   Email: masahiro.miyake@g.softbank.co.jp


   T. Matsuda
   Softbank
   Email: taku.matsuda@g.softbank.co.jp