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Versions: 00 01 02 03 04                                                
Network Working Group                                              Z. Li
Internet-Draft                                                 Z. Zhuang
Intended status: Standards Track                     Huawei Technologies
Expires: April 19, 2016                                            S. Lu
                                                                 Tencent
                                                        October 17, 2015


    BGP Extensions for Service-Oriented MPLS Path Programming (MPP)
                 draft-li-idr-mpls-path-programming-02

Abstract

   Service-oriented MPLS programming (SoMPP) is to provide customized
   service process based on flexible label combinations.  BGP will play
   an important role for MPLS path programming to download programmed
   MPLS path and map the service path to the transport path.  This
   document defines BGP extensions to support Service-oriented MPLS path
   programming.

Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

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
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on April 19, 2016.

Copyright Notice

   Copyright (c) 2015 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Architecture and Usecases of SoMPP  . . . . . . . . . . . . .   3
     3.1.  Architecture  . . . . . . . . . . . . . . . . . . . . . .   3
     3.2.  Usecases  . . . . . . . . . . . . . . . . . . . . . . . .   4
       3.2.1.  Deterministic ECMP  . . . . . . . . . . . . . . . . .   4
       3.2.2.  Centralized Mapping of Service to Tunnels . . . . . .   5
   4.  Download of MPLS Path . . . . . . . . . . . . . . . . . . . .   5
   5.  Download of Mapping of Service Path to Transport Path . . . .   7
     5.1.  Specify Tunnel Type . . . . . . . . . . . . . . . . . . .   7
     5.2.  Specify Specific Tunnel . . . . . . . . . . . . . . . . .   7
   6.  Route Flag Extended Community . . . . . . . . . . . . . . . .   9
   7.  Destination Node Attribute  . . . . . . . . . . . . . . . . .   9
   8.  Capability Negotiation  . . . . . . . . . . . . . . . . . . .  10
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  11
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  11
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  11
     11.2.  Informative References . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   The label stack capability of MPLS would have been utilized well to
   implement flexible path programming to satisfy all kinds of service
   requirements.  But in the distributed environment, the flexible
   programming capability is difficult to implement and always confined
   to reachability.  As the introducing of central control in the
   network, the flexible MPLS programming capability becomes possible
   owing to two factors: 1.  It becomes easier to allocate label for
   more purposes than reachability; 2.  It is easy to calculate the MPLS
   path in a global network view.  Moreover, the MPLS path programming
   capability can be utilized to satisfy more requirements of service
   bearing in the service layer which is defined as Service-oriented
   MPLS path programming.  BGP will play an important role for MPLS path
   programming to download programmed MPLS path and map the service path



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   to the transport path.  This document defines BGP extensions to
   support Service-oriented MPLS path programming.

2.  Terminology

   BGP: Border Gateway Protocol

   EVPN: Ethernet VPN

   L2VPN: Layer 2 VPN

   L3VPN: Layer 3 VPN

   MPP: MPLS Path Programming

   MVPN: Multicast VPN

   RR: Route Reflector

   SR-Path: Segment Routing Path

   NLRI: Network Layer Reachability Information

3.  Architecture and Usecases of SoMPP

3.1.  Architecture

   The architecture of BGP-based MPLS path programming is shown in the
   Figure 1.  Central control plays an important role in MPLS path
   programming.  It can extend the MPLS path programming capability
   easily.  The central controller can calculate path in a global
   network view and implement the MPLS path programming to satisfy
   different requirements of services.  The result of MPLS path
   programming can be advertised from the central controller to the
   client nodes through BGP extensions to the ingress PEs.  When client
   nodes receives the result of MPLS path programming, it will install
   the MPLS forwarding entry for the specified BGP prefix to implement
   the service process.













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                  +-------------------+
                  |      Central      |
                  |     Controller    |
       |----------|(Path Calculation  |--------|
       |          | /Path Programming)|        |
       |          +-------------------+        |
       |                                       |
   MPLS Path                                MPLS Path
       |                                       |
       |                                       |
       |                                       |
    +--------+         +--------+         +--------+
    | CLIENT |         | CLIENT |         | CLIENT |
    |        | ......  |        | ......  |        |
    |  (PE)  |         |  (P)   |         |  (PE)  |
    |        |         |        |         |        |
    +--------+         +--------+         +--------+

        Figure 1 BGP-based MPLS Path Programming

3.2.  Usecases

3.2.1.  Deterministic ECMP

   Entropy Label[RFC6790] is introduced to improve the ECMP capability
   by encapsulate the entropy label in the MPLS label stack.  The
   existing implementation is always to calculate the entropy label
   based on the header of packets by specific hash algorithm in the
   ingress node.  That is, the entropy label is determined locally by
   the ingress node.  The method can improve the hash of packets in the
   network for load-sharing.  But since the ingress node lacks the
   knowledge of the global traffic pattern of the network and calculates
   the entropy label by itself it may be not able to improve the ECMP
   capability accurately and in some cases it may deteriorate the
   imbalance of load-sharing.

   With the central controlled MPLS path programming, the central
   controller can collect the global traffic pattern information of the
   network and based on the information deterministically calculate the
   entropy label for specific flows to help improve the load-sharing of
   the network.  Then the central controller can download the label
   stack information with the deterministic entropy label to the ingress
   PEs for the specific BGP prefix.  The ingress node can install the
   MPLS forwarding entry shown in the following figure to help optimize
   the ECMP of the flow specified by the BGP prefix, then optimize the
   ECMP of the whole network.





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   +----------+      +----------+----------+
   |   BGP    | ---> |  Entropy |BGP Prefix| ---> Transport
   |  Prefix  |      |   Label  |   Label  |        Tunnel
   +----------+      +----------+----------+

3.2.2.  Centralized Mapping of Service to Tunnels

   In the network there can be multiple tunnels to one specific
   destination which satisfy different constraints.  In the traditional
   way, the tunnel is set up by the distributed forwarding nodes.  As
   the PCE-initiated LSP setup [I-D.ietf-pce-pce-initiated-lsp]is
   introduced, the tunnel with different constraints can be set up in
   the central controlled way.  In order to satisfy different service
   requirements, it is necessary to provide the capability to flexibly
   map the service to different tunnels which constraints can satisfy
   the required service requirement.  Since the central controller has
   enough information of the whole network view, it can be an effective
   way to map the service (such as L3VPN and L2VPN) to the tunnel by the
   central controller and advertise the mapping information to the
   ingress PE of the service to guide the mapping in the forwarding
   node.

   There can be two types of behaviors to map service to the tunnel:

   1.  Specify the tunnel type: with the method BGP will carry the
   tunnel type information for the BGP prefix.  When the ingress PE
   receives the information, it will use the tunnel type and the nexthop
   address (or other specified target IP address) to search the
   corresponding tunnels to bear the flow specified by the BGP prefix.
   If there are more than one tunnels, the ingress PE will load share
   the traffic across all the tunnels.

   2.  Specify the specific tunnel: For MPLS TE/SR-TE tunnel, there can
   be multiple MPLS TE tunnels from one ingress PE to a specific
   destination with different constraints.  BGP can carry the tunnel
   identifier information for the BGP prefix from the controller to the
   ingress node.  When the ingress PE receives the information, it will
   use the tunnel identifier information to search the corresponding
   tunnels to bear the flow specified by the BGP prefix.  If there are
   multiple tunnel identifiers, the ingress PE will load share the
   traffic across all the tunnels.

4.  Download of MPLS Path

   According to the service requirements, the central controller can
   combine MPLS labels flexibly.  Then it can download the service label
   combination for specific prefix.BGP extensions are necessary to
   advertise label stacks for the prefix in NLRI field.



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                     +---------------------------+
                     |   Length (1 octet)        |
                     +---------------------------+
                     |   Label (3 octets)        |
                     +---------------------------+
                     .............................
                     +---------------------------+
                     |   Prefix (variable)       |
                     +---------------------------+
                   Figure 1: NLRI Definition in RFC3107


   [RFC3107] defines above NLRI to advertise label binding for specific
   prefix.  The label field can carry one or more labels.  Each label is
   encoded as 3 octets, where the high-order 20 bits contain the label
   value, and the low order bit contains "Bottom of Stack".  But for
   other AFI/SAFIs using label binding such as VPNv4, VPNv6, EVPN, MVPN,
   etc., it dose not support the capability to carry more labels for the
   specific prefix.  Moreover for the AFI/SAFIs which do not support
   label binding capability originally, but may possibly adopt MPLS path
   programming now, there is no label field in the NLRI.  In order to
   support flexible MPLS path programming, this document defines and
   uses a new BGP attribute called the "Extended Label attribute".  This
   is an optional transitive BGP attribute.  The format of this
   attribute is defined as follows:

                      +---------------------------+
                      |   Label 1 (3 octets)      |
                      +---------------------------+
                      |   Label 2 (3 octets)      |
                      +---------------------------+
                      .............................
                      +---------------------------+
                      |   Label n (3 octets)      |
                      +---------------------------+
                    Figure 2: Extended Label Attribute


   The Label field carries one or more labels (that corresponds to the
   stack of labels [[RFC3032]]).  Each label is encoded as 3 octets,
   where the high-order 20 bits contain the label value, and the low
   order bit contains "Bottom of Stack" (as defined in [[RFC3032]]).

   The central controller for MPLS path programming could build a route
   with Extended Label attribute and send it to the ingress routers.

   Upon receiving such a route from the central Controller, the ingress
   router SHOULD select such a route as the best path.  If a packet



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   comes into the ingress router and uses such a path, the ingress
   router will encapsulate the stack of labels which is derived from the
   Extended Label Attribute of the route into the packet and forward the
   packet along the path.

   The "Extended Label attribute" can be used for various BGP address
   families.  Before using this attribute, firstly, it is necessary to
   negotiate the capability between two nodes to support MPLS path
   programming for a specific BGP address family.  If negotiation fails,
   a node MUST NOT send this attribute and MUST discard this attribute
   when it receives.

5.  Download of Mapping of Service Path to Transport Path

5.1.  Specify Tunnel Type

   [I-D.ietf-idr-tunnel-encaps] proposes the Tunnel Encapsulation
   Attribute which can be used without BGP Encapsulation SAFI to specify
   a set of tunnels.  It defines a series of Encapsulation Sub-TLVs for
   particular tunnel types.  It also defines the Remote Endpoint
   Attributes Sub-TLV to specify the remote tunnel endpoint address for
   each tunnel which can be different the BGP nexthop.  The Tunnel
   Encapsulation Attributes can be reused for the MPLS path programming
   to specify the tunnel types, the encapsulation and the remote tunnel
   endpoint address which can determine a set of tunnels which the
   service can map to.  Now the limited MPLS tunnel types are defined
   for the Tunnel Encapsulation Attributes.  In order to support MPLS
   path programming, the following MPLS tunnel types are to be defined:

        Value                  Tunnel Type
       -------      ---------------------------------------------------
         TBD        LDP LSP
         TBD        RSVP-TE LSP
         TBD        MPLS-based Segment Routing Best-effort Path
         TBD        MPLS-based Segment Routing Traffic Engineering Path


5.2.  Specify Specific Tunnel

   Besides specifying the tunnel types to determine the set of tunnels
   which the service traffic can map to, the specific tunnels can be
   specified directly by the tunnel identifiers when map the service
   traffic to the path.  BGP extensions is necessary that through the
   community attribute of BGP the identifier of the transport path can
   be carried when advertise the specific prefix.

   In order to support the application, this document defines a new BGP
   attribute called the "Extended Unicast Tunnel attribute".  This is an



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   optional transitive BGP attribute.  The format of this attribute is
   defined as follows:

         +------------------------------------------------+
         | Flags (1 octet)                                |
         +------------------------------------------------+
         | Tunnel Type (1 octets)                         |
         +------------------------------------------------+
         | Tunnel Identifier (variable)                   |
         +------------------------------------------------+


   The Flags is reserved and must be set as zero.  The Tunnel Type
   identifies the type of the tunneling technology used for the unicast
   service path.  The tunnel type determines the syntax and semantics of
   the Tunnel Identifier field.  This document defines following Tunnel
   Types:

         + 0 - No tunnel information present
         + 1 - RSVP-TE LSP
         + 2 - MPLS-based Segment Routing Traffic Engineering Path

   Tunnel Specific Attributes contains the attributes of the tunnel.
   The field is optional.  The value depends on the tunnel type.  It
   will be defined in the future versions.

   When the Tunnel Type is set to "No tunnel information present", the
   Tunnel attribute carries no tunnel information (no Tunnel
   Identifier).  when the type is used, the tunnel used for the service
   path is determined by the ingress router.

   When the Tunnel Type is set to RSVP - Traffic Engineering (RSVP-TE)
   Label Switched Path (LSP), the Tunnel Identifier is <C-Type, Tunnel
   Sender Address, Tunnel ID, Tunnel End-point Address> as specified in
   [RFC3209] If C-Type = 7, Tunnel Sender Address and Tunnel End-point
   Address are IPv4 address in 4 octets.  If C-Type = 8, Tunnel Sender
   Address and Tunnel End-point Address are IPv6 address in 16 octets.
   The other fields in the RSVP-TE LSP Identifier are the same as
   specified in [RFC3209].

   When the Tunnel Type is set to MPLS-based Segment Routing Traffic
   Engineering Path, the Tunnel Identifier is <C-Type, Tunnel Sender
   Address, Tunnel ID, Tunnel End-point Address>.  If C-Type = 7, Tunnel
   Sender Address and Tunnel End-point Address are IPv4 address in 4
   octets.  If C-Type = 8, Tunnel Sender Address and Tunnel End-point
   Address are IPv6 address in 16 octets.  The tunnel identifier is
   similar as that of RSVP-TE LSP.




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   BGP can carry multiple Extended Unicast Tunnel Attributes for
   specific prefix.  If there are multiple tunnel identifiers, the
   ingress PE will load share the traffic across all the specified
   tunnels for the service traffic determined by the specific BGP
   prefix.

6.  Route Flag Extended Community

   In order to make the MPLS path programming to take effect, the route
   advertised by the central controller after the MPLS Path Programming
   should be selected by the ingress PE over other routes for the same
   BGP prefix.  There are two options of BGP extensions for the purpose:

   Option 1: A new BGP Extended Community called as the "Route Flag
   Extended Community" can be introduced.  The Type value is to be
   assigned by IANA.

   The Route Flag Extended Community is used to carry the flag appointed
   by the BGP central controller.

   The format of this extended community is defined as follows:

       0     1     2     3     4     5     6     7
    +-----+-----+-----+-----+-----+-----+-----+-----+
    |    Type   |  Reserved                   |Flag |
    +-----+-----+-----+-----+-----+-----+-----+-----+

    Flag = 0, Treat as normal route
    Flag = 1, Treat as best route


   When a router receives a BGP route with a Route Flag Extended
   Community and the Flag set to "1", it SHOULD use the route as the
   best route when select the route from multiple routes for a specific
   prefix.

   Option 2: [I-D.ietf-idr-custom-decision] defines a new Extended
   Community, called the Cost Community, which can be used in tie
   breaking during the best path selection process.  The Cost Community
   can be reused by the MPLS path programming to set the "Point of
   Insertion" as 128 to make the route advertised by the central
   controller to be chosen.

7.  Destination Node Attribute

   This document defines and uses a new BGP attribute called as the
   "Destination Node attribute" which Type value is to be assigned by




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   IANA.  The Destination Node attribute is an optional non-transitive
   attribute that can be applied to any address family.

   The Destination Node attribute is used to carry a list of node
   addresses, which are intended to be used to determine the nodes where
   the route with such attribute SHOULD be considered.  If a node
   receives a BGP route with a Destination Node attribute, it MUST check
   the node address list.  If one address of the list belongs to this
   node, the route MUST be used in this node.  Otherwise the route MUST
   be ignored silently.

   The format of this attribute is defined as follows:

    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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               AFI             |       SAFI    |    Reserved   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   ~                                                               ~
   ~               Destination Node Address List                   ~
   ~                                                               ~
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



   AFI: Address Family Identifier (16 bits).

   SAFI: Subsequent Address Family Identifier (8 bits).

   Reserved: One octet reserved for special flags

   Destination Node Address List: The list of IPv4 (AFI=1) or IPv6
   (AFI=2) address.

8.  Capability Negotiation

   It is necessary to negotiate the capability to support MPLS path
   programming.  The MPLS-Path-Programming Capability is a new BGP
   capability [RFC5492].  The Capability Code for this capability is to
   be specified by the IANA.  The Capability Length field of this
   capability is variable.  The Capability Value field consists of one
   or more of the following tuples:









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           +--------------------------------------------------+
           |  Address Family Identifier (2 octets)            |
           +--------------------------------------------------+
           |  Subsequent Address Family Identifier (1 octet)  |
           +--------------------------------------------------+
           |  Send/Receive (1 octet)                          |
           +--------------------------------------------------+

   The meaning and use of the fields are as follows:

   Address Family Identifier (AFI): This field is the same as the one
   used in [RFC4760].

   Subsequent Address Family Identifier (SAFI): This field is the same
   as the one used in [RFC4760].

   Send/Receive: This field indicates whether the sender is (a) willing
   to receive programming MPLS paths from its peer (value 1), (b) would
   like to send programming MPLS paths to its peer (value 2), or (c)
   both (value 3) for the <AFI, SAFI>.

9.  IANA Considerations

   TBD.

10.  Security Considerations

   TBD.

11.  References

11.1.  Normative References

   [I-D.ietf-idr-custom-decision]
              Retana, A. and R. White, "BGP Custom Decision Process",
              draft-ietf-idr-custom-decision-06 (work in progress),
              April 2015.

   [I-D.ietf-idr-tunnel-encaps]
              Rosen, E., Patel, K., and G. Velde, "Using the BGP Tunnel
              Encapsulation Attribute without the BGP Encapsulation
              SAFI", draft-ietf-idr-tunnel-encaps-00 (work in progress),
              August 2015.

   [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>.



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   [RFC3032]  Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
              Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
              Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
              <http://www.rfc-editor.org/info/rfc3032>.

   [RFC3209]  Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
              and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
              Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
              <http://www.rfc-editor.org/info/rfc3209>.

   [RFC4271]  Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
              Border Gateway Protocol 4 (BGP-4)", RFC 4271,
              DOI 10.17487/RFC4271, January 2006,
              <http://www.rfc-editor.org/info/rfc4271>.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760,
              DOI 10.17487/RFC4760, January 2007,
              <http://www.rfc-editor.org/info/rfc4760>.

   [RFC5036]  Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
              "LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
              October 2007, <http://www.rfc-editor.org/info/rfc5036>.

   [RFC5492]  Scudder, J. and R. Chandra, "Capabilities Advertisement
              with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February
              2009, <http://www.rfc-editor.org/info/rfc5492>.

11.2.  Informative References

   [I-D.ietf-pce-pce-initiated-lsp]
              Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
              Extensions for PCE-initiated LSP Setup in a Stateful PCE
              Model", draft-ietf-pce-pce-initiated-lsp-04 (work in
              progress), April 2015.

   [RFC3107]  Rekhter, Y. and E. Rosen, "Carrying Label Information in
              BGP-4", RFC 3107, DOI 10.17487/RFC3107, May 2001,
              <http://www.rfc-editor.org/info/rfc3107>.

   [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>.







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Authors' Addresses

   Zhenbin Li
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: lizhenbin@huawei.com


   Shunwan Zhuang
   Huawei Technologies
   Huawei Bld., No.156 Beiqing Rd.
   Beijing  100095
   China

   Email: zhuangshunwan@huawei.com


   Sujian Lu
   Tencent
   Tengyun Building,Tower A ,No. 397 Tianlin Road,Xuhui District
   Shanghai  200233
   China

   Email: jasonlu@tencent.com
























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