PCEP Extension for Distribution of Link-State and TE information for Optical Networks
draft-lee-pce-pcep-ls-optical-03

Versions: 00 01 02 03                                                   
PCE Working Group                                             Young Lee
                                                          Haomian Zheng
Internet Draft                                                   Huawei
Intended Status: Standard
Expires: March 2018                                  Daniele Ceccarelli
                                                               Ericsson

                                                               Wei Wang
                                     Beijing Univ. of Posts and Telecom

                                                             Peter Park
                                                                     KT

                                                         Bin Young Yoon
                                                                   ETRI


                                                      September 5, 2017



   PCEP Extension for Distribution of Link-State and TE information for
                             Optical Networks



                     draft-lee-pce-pcep-ls-optical-03


Abstract

   In order to compute and provide optimal paths, Path Computation
   Elements (PCEs) require an accurate and timely Traffic Engineering
   Database (TED). Traditionally this Link State and TE information has
   been obtained from a link state routing protocol (supporting traffic
   engineering extensions).

   This document extends the Path Communication Element Communication
   Protocol (PCEP)_ with Link-State and TE information for optical
   networks.



Status of this Memo

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

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



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   other groups may also distribute working documents as Internet-
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   This Internet-Draft will expire on March 5, 2018.

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   document authors. All rights reserved.

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Table of Contents


   1. Introduction...................................................3
   2. Applicability..................................................4
   3. Requirements for PCEP extension................................5
   4. PCEP-LS extension for Optical Networks.........................7
      4.1. Node Attributes TLV.......................................7
      4.2. Link Attributes TLV.......................................8
   5. Security Considerations........................................9
   6. IANA Considerations...........................................10
      6.1. PCEP-LS Sub-TLV Type Indicators..........................10
   7. References....................................................11
      7.1. Normative References.....................................11
      7.2. Informative References...................................11
   Appendix A. Contributor Addresses................................13


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   Author's Addresses...............................................13

1. Introduction

   In Multiprotocol Label Switching (MPLS) and Generalized MPLS
   (GMPLS), a Traffic Engineering Database (TED) is used in computing
   paths for connection oriented packet services and for circuits. The
   TED contains all relevant information that a Path Computation
   Element (PCE) needs to perform its computations. It is important
   that the TED should be complete and accurate anytime so that the PCE
   can perform path computations.

   In MPLS and GMPLS networks, Interior Gateway routing Protocols
   (IGPs) have been used to create and maintain a copy of the TED at
   each node. One of the benefits of the PCE architecture [RFC4655] is
   the use of computationally more sophisticated path computation
   algorithms and the realization that these may need enhanced
   processing power not necessarily available at each node
   participating in an IGP.

   Section 4.3 of [RFC4655] describes the potential load of the TED on
   a network node and proposes an architecture where the TED is
   maintained by the PCE rather than the network nodes. However it does
   not describe how a PCE would obtain the information needed to
   populate its TED. PCE may construct its TED by participating in the
   IGP ([RFC3630] and [RFC5305] for MPLS-TE; [RFC4203] and [RFC5307]
   for GMPLS). An alternative is offered by [BGP-LS].

   [RFC7399] touches upon this issue: "It has also been proposed that
   the PCE Communication Protocol (PCEP) [RFC5440] could be extended to
   serve as an information collection protocol to supply information
   from network devices to a PCE. The logic is that the network devices
   may already speak PCEP and so the protocol could easily be used to
   report details about the resources and state in the network,
   including the LSP state discussed in Sections 14 and 15."

   [Stateful-PCE] describes a set of extensions to PCEP to provide
   stateful control.  A stateful PCE has access to not only the
   information carried by the network's Interior Gateway Protocol
   (IGP), but also the set of active paths and their reserved resources
   for its computations. PCC can delegate the rights to modify the LSP
   parameters to an Active Stateful PCE. This requires PCE to quickly
   be updated on any changes in the Topology and TEDB, so that PCE can
   meet the need for updating LSPs effectively and in a timely manner.
   The fastest way for a PCE to be updated on TED changes is via a
   direct interface with each network node and with incremental update
   from each network node.


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   [PCE-initiated] describes the setup, maintenance and teardown of
   PCE-initiated LSPs under the stateful PCE model, without the need
   for local configuration on the PCC, thus allowing for a dynamic
   network that is centrally controlled and deployed. This model
   requires timely topology and TED update at the PCE.

   [PCEP-LS-Arch] proposes alternative architecture approaches for
   learning and maintaining the Link State (and TE)  information
   directly on a PCE from network nodes as an alternative to IGPs and
   BGP transport and investigate the impact from the PCE, routing
   protocol, and network node perspectives.

   [RFC6805] describes a Hierarchical PCE (H-PCE) architecture which
   can be used for computing end-to-end paths for inter-domain MPLS
   Traffic Engineering (TE) and GMPLS Label Switched Paths (LSPs).
   Within the Hierarchical PCE (H-PCE) architecture [RFC6805], the
   Parent PCE (P-PCE) is used to compute a multi-domain path based on
   the domain connectivity information.  A Child PCE (C-PCE) may be
   responsible for a single domain or multiple domains, it is used to
   compute the intra-domain path based on its domain topology
   information.

   [Stateful H-PCE] presents general considerations for stateful PCE(s)
   in hierarchical PCE architecture. In particular, the behavior
   changes and additions to the existing stateful PCE mechanisms
   (including PCE-initiated LSP setup and active PCE usage) in the
   context of networks using the H-PCE architecture.

   [PCEP-LS] describes a mechanism by which Link State and TE
   information can be collected from packet networks and shared with
   PCE with the PCEP itself. This is achieved using a new PCEP message
   format.

   This draft describes an optical extension of [PCEP-LS] and explains
   how encodings suggested by [PCEP-LS] can be used in the optical
   network contexts.





2. Applicability

   There are three main applicability of this alternative proposed by
   this draft:




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      - Case 1: Where there is IGP running in optical network but
         there is a need for a faster link-state and TE resource
         collection at the PCE directly from an optical node (PCC) via
         a PCC-PCE interface.

           o A PCE may receive an incremental update (as opposed to
              the entire TE information of the node/link).


         Note: A PCE may receive full information from IGP using
         existing mechanism. In some cases, the convergence of full
         link-state and TE resource information of the entire network
         may not be appropriate for certain applications. Incremental
         update capability will enhance the accuracy of the TE
         information at a given time.


      - Case 2: Where there is no IGP running in the optical network
         and there is a need for link-state and TE resource collections
         at the PCE directly from an optical node (PCC) via a PCC-PCE
         interface.


      - Case 3: Where there is a need for transporting abstract
         optical link-state and TE information from child PCE and to a
         parent PCE in H-PCE [RFC6805] and [Stateful H-PCE] as well as
         for Physical Network Controller (PNC) to Multi-Domain Service
         Coordinator (MDSC) in Abstraction and Control of TE Networks
         (ACTN) [ACTN-Frame].

         Note: The applicability for Case 3 may arise as a consequence
         of Case 1 and Case 2. When TE information changes occur in the
         optical network, this may also affect abstracted TE
         information and thus needs to be updated to Parent PCE/MSDC
         from each child PCE/PNC.



3. Requirements for PCEP extension


   The key requirements associated with link-state (and TE)
   distribution are identified for PCEP and listed in Section 4 of
   [PCEP-LS]. These new functions required in PCEP to support
   distribution of link-state (and TE) information are described in
   Section 5 of [PCEP-LS]. Details of PCEP messages and related
   Objects/TLVs are specified in Sections 8 and 9 of [PCEP-LS]. The key


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   requirements and new functions specified in [PCEP-LS] are equally
   applicable to optical networks.

   Besides the generic requirements specified in [PCEP-LS], optical
   specific features also need to be considered in this document. As
   connection-based network, there are specific parameters such as
   reachable table, optical latency, wavelength consistency and some
   other parameters that need to be included during the topology
   collection. Without these restrictions, the path computation may be
   inaccurate or infeasible for deployment, therefore these information
   MUST be included in the PCEP.

   The procedure on how the optical parameters are used is described in
   following sections.

ion

   The reachable source-destination node pair indicates that there are
   a few number of OCh paths between two nodes. The reachability is
   restricted by impairment, wavelength consistency and so on. This
   information is necessary at PCE to promise the path computed between
   source node and destination node is reachable. In this scenario, the
   PCE should be responsible to compute how many OCh paths are
   available to set up connections between source and destination node.
   Moreover, if a set of optical wavelength is indicated in the path
   computation request, the PCE should also determine whether a
   wavelength of the set of preselected optical wavelength is available
   for the source-destination pair connection.

   To enable PCE to complete the above functions, the reachable
   relationship and OMS link information need to be reported to PCE.
   Once PCE detect that any wavelength is available, the corresponding
   OMS link should be included in a lambda plane. Then this link can be
   used for path computation in future.

   Moreover, in a hierarchical PCE architecture, the information above
   need to be reported from child PCE to parent PCE, who acts as a
   service coordinator.



   It is a usual case that the PCC indicates the latency when
   requesting the path computation. In optical networks the latency is
   a very sensitive parameter and there is stricter requirement on
   latency. Given the maximal number of OCh paths between source-
   destination nodes, the PCE also need to determine how many OCh path
   satisfies the indicated latency threshold.


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   There is usually high-performance algorithm running on the PCE to
   guarantee the performance of the computed path. During the
   computation, the delay factor may be converted into a kind of link
   weight. After the algorithm provides a few candidate paths between
   the source and destination nodes, the PCE SHOULD be capable to
   selecting one shortest path by computing the total path delay.

   Optical PCEs are embedded with optimization algorithm, e.g.,
   shortest path algorithm, to improve the performance of computed
   path.

4. PCEP-LS extension for Optical Networks

   This section provides additional PCEP-LS extension necessary to
   support optical networks. All Objects/TLVs defined in [PCEP-LS] are
   applicable to optical networks.

4.1. Node Attributes TLV

   Node-Attributed TLV is defined in Section 9.2.10.1 in [PCEP-LS] as
   follows. This TLV is applicable for LS Node Object-Type as defined
   in [PCEP-LS].



       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Type                |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      //               Node Attributes Sub-TLVs (variable)           //
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



   The following 'Node Attribute' sub-TLVs are valid for optical
   networks:

   +-----------+------------------+--------------+-------------------+
   |  Sub-TLV  | Description      | TLV/Sub-TLV  | Length  |Reference|
   +-----------+------------------+--------------+---------+---------+
   |    TBD    | Connectivity     |   5/14       | variable|[RFC7579]|
   |           | Matrix           |              |         |[RFC7580]|
   |    TBD    | Resource Block   |   6/1        | variable|[RFC7688]|
   |           | Information      |              |         |         |


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   |    TBD    | Resource Block   |   6/2        | variable|[RFC7688]|
   |           | Accessibility    |              |         |         |
   |    TBD    | Resource Block   |   6/3        | variable|[RFC7688]|
   |           | Wavelength Const |              |         |         |
   |    TBD    | Resource Block   |   6/4        | variable|[RFC7688]|
   |           | Pool State       |              |         |         |
   |    TBD    | Resource Block   |   6/5        | variable|[RFC7688]|
   |           | Shared Access    |              |         |         |
   |           | Wavelength Avail.|              |         |         |
   +------------------------------------------------------=----------+


4.2. Link Attributes TLV

   Link-Attributes TLV is defined in Section 9.2.10.2 in [PCEP-LS] as
   follows. This TLV is applicable for LS Link Object-Type as defined
   in [PCEP-LS].



       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Type                |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      //                  Link Attributes Sub-TLVs (variable)        //
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



   The following 'Link Attribute' sub-TLVs are valid for optical
   networks:















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   +-----------+-----------------+--------------+--------+----------+
   |  Sub-TLV  | Description     | TLV/Sub-TLV  | Length |Reference |
   |           |                 |              |        |          |
   +-----------+-----------------+--------------+--------+----------+
   |    TBD    | ISCD            |   15         |Variable|[RFC4203] |
   |           |                 |              |        |          |
   |    TBD    | OTN-TDM SCSI    |   15/1,2     |Variable|[RFC4203] |
   |           |                 |              |        |[RFC7138] |
   |    TBD    | WSON-LSC SCSI   |   15/1,2     |Variable|[RFC4203] |
   |           |                 |              |        |[RFC7688] |
   |    TBD    | Flexi-grid SCSI |   15/1       |Variable|[FlexOSPF]|
   |           |                 |              |        |
   |    TBD    | Port Label      |   34         |Variable|[RFC7579] |
   |           | Restriction     |              |        |[RFC7580] |
   |           |                 |              |        |[FlexOSPF]|
   +-----------+-----------------+--------------+--------+----------+

4.3. PCEP-LS for Optical Network Abstraction

   This section provides additional PCEP-LS extension necessary to
   support optical networks parameters discussed in Sections 3.1 and
   3.2. Abstraction is primarily applied to C-PCE and P-PCE although
   the same principle can be applied to PCC (NE) to PCE.

   For OTN networks, max bandwidth available may be per ODU 0/1/2/3
   switching level or aggregated across all ODU switching levels (i.e.,
   ODUj/k).

   For WSON networks, max bandwidth available may be per
   lambda/frequency level (OCh) or aggregated across all
   lambda/frequency level. Per OCh level abstraction gives more
   detailed data to the P-PCE at the expense of more information
   processing. Either OCh-level or aggregated level abstraction should
   factor in the RWA constraint (i.e., wavelength continuity) at the C-
   PCE level. This means the C-PCE should have this capability and
   advertise it as such.

   [Editor's Note: Encoding will be provided in the revision]


5. Security Considerations

   This document extends PCEP for LS (and TE) distribution including a
   set of TLVs.  Procedures and protocol extensions defined in this
   document do not effect the overall PCEP security model.  See
   [RFC5440], [I-D.ietf-pce-pceps]. The PCE implementation SHOULD
   provide mechanisms to prevent strains created by network flaps and


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   amount of LS (and TE) information.  Thus it is suggested that any
   mechanism used for securing the transmission of other PCEP message
   be applied here as well.  As a general precaution, it is RECOMMENDED
   that these PCEP extensions only be activated on authenticated and
   encrypted sessions belonging to the same administrative authority.

6. IANA Considerations

   This document requests IANA actions to allocate code points for the
   protocol elements defined in this document.

6.1. PCEP-LS Sub-TLV Type Indicators

   This document specifies a set of PCEP-LS Sub-TLVs. IANA is requested
   to create an "PCEP-LS Sub-TLV Types" sub-registry in the "PCEP TLV
   Type Indicators" for the sub-TLVs carried in the PCEP-LS TLV (Node
   Attributes TLV and Link Attributes TLV).

   +-----------+------------------+--------------+----------+
   |  Sub-TLV  | Description      | Ref Sub-TLV  | Reference|
   +-----------+------------------+--------------+----------+
   |    TBD    | Connectivity     |   5/14       | [RFC7579]|
   |           | Matrix           |              | [RFC7580]|
   |    TBD    | Resource Block   |   6/1        | [RFC7688]|
   |           | Information      |              |          |
   |    TBD    | Resource Block   |   6/2        | [RFC7688]|
   |           | Accessibility    |              |          |
   |    TBD    | Resource Block   |   6/3        | [RFC7688]|
   |           | Wavelength Const |              |          |
   |    TBD    | Resource Block   |   6/4        | [RFC7688]|
   |           | Pool State       |              |          |
   |    TBD    | Resource Block   |   6/5        | [RFC7688]|
   |           | Shared Access    |              |          |
   |           | Wavelength Avail.|              |          |
   |    TBD    | ISCD             |   15         |[RFC4203] |
   |           |                  |              |          |
   |    TBD    | OTN-TDM SCSI     |   15/1,2     |[RFC4203] |
   |           |                  |              |[RFC7138] |
   |    TBD    | WSON-LSC SCSI    |   15/1,2     |[RFC4203] |
   |           |                  |              |[RFC7688] |
   |    TBD    | Flexi-grid SCSI  |   15/1       |[FlexOSPF]|
   |           |                  |              |          |
   |    TBD    | Port Label       |   34         |[RFC7579] |
   |           | Restriction      |              |[RFC7580] |
   |           |                  |              |[FlexOSPF]|
   +-----------+------------------+--------------+----------+



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7. References

7.1. Normative References

   [RFC4655] Farrel, A., Vasseur, J.-P., and J. Ash, "A Path
             Computation Element (PCE)-Based Architecture", RFC 4655,
             August 2006.

   [RFC4674] Le Roux, J., Ed., "Requirements for Path Computation
             Element (PCE) Discovery", RFC 4674, October 2006.

   [RFC5088] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
             Zhang, "OSPF Protocol Extensions for Path Computation
             Element (PCE) Discovery", RFC 5088, January 2008.

   [RFC5089] Le Roux, JL., Ed., Vasseur, JP., Ed., Ikejiri, Y., and R.
             Zhang, "IS-IS Protocol Extensions for Path Computation
             Element (PCE) Discovery", RFC 5089, January 2008.

   [RFC5250] Berger, L., Bryskin, I., Zinin, A., and R. Coltun, "The
             OSPF Opaque LSA Option", RFC 5250, July 2008.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
             Engineering", RFC 5305, October 2008.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
             Element (PCE) Communication Protocol (PCEP)", RFC 5440,
             March 2009.



7.2. Informative References

   [JMS]    Java Message Service, Version 1.1, April 2002, Sun
             Microsystems.

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic
             Engineering (TE) Extensions to OSPF Version 2", RFC 3630,
             September 2003.

   [RFC4203]  Kompella, K., Ed. and Y. Rekhter, Ed., "OSPF Extensions
             in Support of Generalized Multi-Protocol Label Switching
             (GMPLS)", RFC 4203, October 2005.


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   [RFC4655]  Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
             Element (PCE)-Based Architecture", RFC 4655, August 2006.

   [BGP-LS] Gredler, H., Medved, J., Previdi, S., Farrel, A., and
             S.Ray, "North-Bound Distribution of Link-State and TE
             information using BGP", draft-ietf-idr-ls-distribution,
             work in progress.

   [S-PCE-GMPLS] X. Zhang, et. al, "Path Computation Element (PCE)
             Protocol Extensions for Stateful PCE Usage in GMPLS-
             controlled Networks", draft-ietf-pce-pcep-stateful-pce-
             gmpls, work in progress.

   [RFC7399] A. Farrel and D. king, "Unanswered Questions in the Path
             Computation Element Architecture", RFC 7399, October 2015.

   [RFC7449]  Y. Lee, G. Bernstein, "Path Computation Element
             Communication Protocol (PCEP) Requirements for Wavelength
             Switched Optical Network (WSON) Routing and Wavelength
             Assignment", RFC 7449, February 2015.

   [RFC4456] Bates, T., Chen, E., and R. Chandra, "BGP Route
             Reflection: An Alternative to Full Mesh Internal BGP
             (IBGP)", RFC 4456, April 2006.

   [RFC6163]  Y. Lee, G. Bernstein, W. Imajuku, "Framework for GMPLS
             and PCE Control of Wavelength Switched Optical Networks",
             RFC 6163,

   [G.680] ITU-T Recommendation G.680, Physical transfer functions of
             optical network elements, July 2007.

   [ACTN-Frame] D.Ceccarelli, and Y. Lee (Editors), "Framework for
             Abstraction and Control of TE Networks", draft-ietf-teas-
             actn-framework, work in progress.

   [RFC6805] A. Farrel and D. King, "The Application of the Path
             Computation Element Architecture to the Determination of a
             Sequence of Domains in MPLS and GMPLS", RFC 6805, November
             2012.

   [PCEP-LS-Arch] Y. Lee, D. Dhody and D. Ceccarelli, "Architecture and
             Requirement for Distribution of Link-State and TE
             Information via PCEP", draft-leedhody-teas-pcep-ls, work
             in progress.




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   [PCEP-LS] D. Dhody, Y. Lee and D. Ceccarelli "PCEP Extension for
             Distribution of Link-State and TE Information.", work in
             progress, September 21, 2015[Stateful-PCE] Crabbe, E.,
             Minei, I., Medved, J., and R. Varga, "PCEP Extensions for
             Stateful PCE", draft-ietf-pce-stateful-pce, work in
             progress.

   [PCE-Initiated] 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, work in
             progress.

   [Stateful H-PCE] D. Dhody, Y. Lee and D. Ceccarelli, "Hierarchical
             Stateful Path Computation Element (PCE)", draft-ietf-pce-
             stateful-hpce, work-in-progress.

   [FlexOSPF] X. Zhang, H. Zheng, R. Casellas, O. Gonzalez de Dios, D.
             Ceccarelli, "GMPLS OSPF Extensions in support of Flexi-
             grid DWDM networks", draft-ietf-ccamp-flexible-grid-ospf-
             ext-05, work in progress.



Appendix A. Contributor Addresses

   Dhruv Dhody
   Huawei Technologies
   Divyashree Techno Park, Whitefield
   Bangalore, Karnataka 560066
   India
   Email: dhruv.ietf@gmail.com


Author's Addresses


   Young Lee
   Huawei Technologies
   5340 Legacy Drive, Building 3
   Plano, TX 75023, USA

   Email: leeyoung@huawei.com






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   Haomian Zheng
   Huawei Technologies Co., Ltd.
   F3-1-B R&D Center, Huawei Base,
   Bantian, Longgang District
   Shenzhen 518129 P.R.China

   Email: zhenghaomian@huawei.com


   Daniele Ceccarelli
   Ericsson
   Torshamnsgatan,48
   Stockholm
   Sweden

   EMail: daniele.ceccarelli@ericsson.com

   Wei Wang
   Beijing University of Posts and Telecom
   No. 10, Xitucheng Rd. Haidian District, Beijing 100876, P.R.China

   Email: weiw@bupt.edu.cn

    Peter Park
   KT
   Email: peter.park@kt.com

   Bin Yeong Yoon
   ETRI
   Email: byyun@etri.re.kr

















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