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Versions: (draft-leedhody-pce-vn-association) 00 01

PCE Working Group                                                 Y. Lee
Internet-Draft                                                      SKKU
Intended Status: Standards track                                H. Zheng
Expires:  April 28, 2020                             Huawei Technologies
                                                           D. Ceccarelli
                                                                Ericsson
                                                        October 28, 2019


    Path Computation Element communication Protocol (PCEP) extensions
    for Establishing Relationships between sets of LSPs and Virtual
                               Networks
                 draft-ietf-pce-vn-association-01


Abstract

   This document describes how to extend Path Computation Element (PCE)
   Communication Protocol (PCEP) association mechanism introduced by the
   PCEP Association Group specification, to further associate sets of
   LSPs with a higher-level structure such as a virtual network (VN)
   requested by clients or applications. This extended association
   mechanism can be used to facilitate virtual network control using PCE
   architecture.



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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."










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   The list of current Internet-Drafts can be accessed at
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Table of Contents

   1. Introduction  . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1. Requirements Language . . . . . . . . . . . . . . . . . . .  4
   2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . .  5
   3. Operation Overview  . . . . . . . . . . . . . . . . . . . . . .  5
   4. Extensions to PCEP  . . . . . . . . . . . . . . . . . . . . . .  7
   5. Applicability to H-PCE architecture . . . . . . . . . . . . . .  8
   6. Implementation Status . . . . . . . . . . . . . . . . . . . . .  9
     6.1.  Huawei's Proof of Concept based on ONOS  . . . . . . . . . 10
   7. Security Considerations . . . . . . . . . . . . . . . . . . . . 10
   8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 10
     8.1. Association Object Type Indicator . . . . . . . . . . . . . 10
     8.2. PCEP TLV Type Indicator . . . . . . . . . . . . . . . . . . 10
     8.3. PCEP Error  . . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  Manageability Considerations . . . . . . . . . . . . . . . . . 11
     9.1.  Control of Function and Policy . . . . . . . . . . . . . . 11
     9.2.  Information and Data Models  . . . . . . . . . . . . . . . 11
     9.3.  Liveness Detection and Monitoring  . . . . . . . . . . . . 11
     9.4.  Verify Correct Operations  . . . . . . . . . . . . . . . . 11
     9.5.  Requirements On Other Protocols  . . . . . . . . . . . . . 12
     9.6.  Impact On Network Operations . . . . . . . . . . . . . . . 12
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 12



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     10.2. Informative References . . . . . . . . . . . . . . . . . . 12




1. Introduction

   The Path Computation Element communication Protocol (PCEP) provides
   mechanisms for Path Computation Elements (PCEs) to perform path
   computations in response to Path Computation Clients' (PCCs)
   requests.

   [RFC8051] describes general considerations for a stateful PCE
   deployment and examines its applicability and benefits, as well as
   its challenges and limitations through a number of use cases.
   [RFC8231] 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.  The additional state allows the PCE to compute
   constrained paths while considering individual LSPs and their
   interactions.

   [RFC8281] describes the setup, maintenance and teardown of PCE-
   initiated LSPs under the stateful PCE model.

   [I-D.ietf-pce-association-group] introduces a generic mechanism to
   create a grouping of LSPs. This grouping can then be used to define
   association between sets of LSPs or between a set of LSPs and a set
   of attributes.

   [RFC8453] describes various Virtual Network (VN) operations initiated
   by a customer/application. In this context, there is a need for
   associating a set of LSPs with a VN "construct" to facilitate VN
   operations in PCE architecture. This association allows the PCEs to
   identify which LSPs belong to a certain VN. The PCE could then use
   this association to optimize all LSPs belonging to the VN together.
   The PCE could further take VN specific actions on the LSPs such as
   relaxation of constraints, policy actions, setting default behavior
   etc.

   [RFC8637] examines the PCE and ACTN architecture and describes how
   the PCE architecture is applicable to ACTN. [RFC6805] and [I-D.ietf-
   pce-stateful-hpce] describes a hierarchy of stateful PCEs with Parent
   PCE coordinating multi-domain path computation function between Child
   PCE(s) and thus making it the base for PCE applicability for ACTN. In
   this text child PCE would be same as Provisioning Network Controller
   (PNC), and the parent PCE as Multi-domain Service Coordinator (MDSC)



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   [RFC8453].

   This document specifies a PCEP extension to associate a set of LSPs
   based on Virtual Network (VN) (or customer). A Virtual Network (VN)
   is a customer view of the TE network.  Depending on the agreement
   between client and provider various VN operations and VN views are
   possible as described in [RFC8453].

1.1. Requirements Language

   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.




































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2. Terminology

   The terminology is as per [RFC4655], [RFC5440], [RFC6805], [RFC8231]
   and [RFC8453].

3. Operation Overview

   As per [I-D.ietf-pce-association-group], LSPs are associated with
   other LSPs with which they interact by adding them to a common
   association group.

   An association group based on VN is useful for various optimizations
   that should be applied by considering all the LSPs in the
   association. This includes, but not limited to -

      o Path Computation: When computing path for a LSP, the impact of
      this LSP, on the other LSPs belonging to the same VN is useful to
      analyze. The aim would be optimize overall VN and all LSPs, rather
      than a single LSP. Also, the optimization criteria such as
      minimize the load of the most loaded link (MLL) [RFC5541] and
      other could be applied for all the LSP belonging to the same VN,
      identified by the VN association.

      o Path Re-Optimization: The child PCE or the parent PCE would like
      to use advanced path computation algorithm and optimization
      technique that consider all the LSPs belonging to a VN/customer
      and optimize them all together during the re-optimization.


      This association is useful in PCEP session between parent PCE
      (MDSC) and child PCE (PNC). When computing the path, the child PCE
      (PNC) refer to the VN in the request from parent PCE (MDSC) and
      map the VN to available network resources. Based on the
      availability of resource and various constraints, the path is
      computed and replied to the parent PCE (MDSC). The mapping
      relationship between the VN and the network could be included as a
      part of response as well.  The figure describes a typical VN
      operations using PCEP for illustration purpose. It is worth noting
      that in a multi-domain scenario, the different domain is
      controlled by different child PCEs. In order to set up the end-to-
      end tunnel, multiple tunnel segments need to be stitched, by the
      border nodes in each domain who receives the instruction from
      their child PCE (PNC).








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                                   ******
                         ..........*MDSC*..............................
                      .            ****** ..                   MPI    .
                   .                .        .                 PCEP   .
                .                   .          .   PCInitiate LSPx   .
              .                    .             .   with VNAG = 10   .
             .                    .                .                  .
            .                    .                  .                 .
           .                    .                    .                .
           v                    v                    v                .
         ******               ******               ******             .
         *PNC1*               *PNC2*               *PNC4*             .
         ******               ******               ******             .
         +---------------+    +---------------+    +---------------+  .
         |A              |----|               |----|              C|  .
         |               |    |               |    |               |  .
         |DOMAIN 1       |----|DOMAIN 2       |----|DOMAIN 4       |  .
         +------------B13+    +---------------+    +B43------------+  .
                                                  /                  .
                             ******              /                   .
                             *PNC3*<............/.....................
                             ******            /
                             +---------------+/
                              B31           B34
                              |               |
                              |DOMAIN 3      B|
                              +---------------+

         MDSC -> Parent PCE
         PNC  -> Child  PCE
         MPI  -> PCEP

   In this draft, this grouping is used to define associations between a
   set of LSPs and a virtual network, a new association group is defined
   below -

      o  VN Association Group (VNAG)

   One new Association type is defined as described in the Association
   object -

      o  Association type = TBD1 ("VN Association") for VNAG

   The scope and handling of VNAG identifier is similar to the generic
   association identifier defined in [I-D.ietf-pce-association-group].

   In this document VNAG object refers to an Association Object with the
   Association type set to "VNAG".



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   Local polices on the PCE MAY define the computational and
   optimization behavior for the LSPs in the VN. An LSP MUST NOT belong
   to more than one VNAG. If an implementation encounters more than one
   VNAG, it MUST consider the first occurrence and ignore the others.

   [I-D.ietf-pce-association-group] specify the mechanism for the
   capability advertisement of the association types supported by a PCEP
   speaker by defining a ASSOC-Type-List TLV to be carried within an
   OPEN object.  This capability exchange for the association type
   described in this document (i.e.  VN Association Type) MUST be done
   before using the policy association.  Thus the PCEP speaker MUST
   include the VN Association Type (TBD1) in the ASSOC-Type-List TLV
   before using the VNAG in the PCEP messages.

   This Association-Type is dynamic in nature and created by the Parent
   PCE (MDSC) for the LSPs belonging to the same VN or customer. These
   associations are conveyed via PCEP messages to the PCEP peer.
   Operator-configured Association Range MUST NOT be set for this
   association-type and MUST be ignored.

4. Extensions to PCEP

   The format of VNAG is as per the ASSOCIATION object [I-D.ietf-pce-
   association-group].

   This document defines one mandatory TLV "VIRTUAL-NETWORK-TLV" and one
   new optional TLV "VENDOR-INFORMATION-TLV"; apart from this TLV,
   VENDOR-INFORMATION-TLV can be used to carry arbitrary vendor specific
   information.

      o VIRTUAL-NETWORK-TLV: Used to communicate the VN Identifier.

      o VENDOR-INFORMATION-TLV: Used to communicate arbitrary vendor
      specific behavioral information, described in [RFC7470].

   The format of VIRTUAL-NETWORK-TLV is 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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |           Type=TBD2           |       Length (variable)       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                                                               |
   //                   Virtual Network Name                      //
   |                                                               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





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              Figure 1: The VIRTUAL-NETWORK-TLV formats

   Type: TBD2 (to be allocated by IANA)

   Length: Variable Length

   Virtual Network Name (variable): an unique symbolic name for the VN.
   It SHOULD be a string of printable ASCII characters, without a NULL
   terminator. The VN name is a human-readable string that identifies
   a VN and can be specified at the beginning of the PCEP session.
   After the mapping between VN and LSPs are accomplished, the VN name
   can be used as a reference, to identify the LSPs from VN or identify
   the VN from LSP information in the later PCEP session. Therefore it
   MUST remain constant throughout an LSP's lifetime, which may span
   across multiple consecutive PCEP sessions and/or PCC restarts.  The
   VN name MAY be specified by an operator or auto-generated by the
   PCEP speaker.

   The VIRTUAL-NETWORK-TLV MUST be included in VNAG object.If a PCEP
   speaker receives the VNAG object without the VIRTUAL-NETWORK-TLV, it
   MUST send a PCErr message with Error-Type=6 (mandatory object
   missing) and Error-Value=TBD3 (VIRTUAL-NETWORK-TLV missing) and close
   the session.

   The format of VENDOR-INFORMATION-TLV is defined in [RFC7470].

5. Applicability to H-PCE architecture

   The ability to compute shortest constrained TE LSPs in Multiprotocol
   Label Switching (MPLS) and Generalized MPLS (GMPLS) networks across
   multiple domains has been identified as a key motivation for PCE
   development.  [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 architecture, the parent
   PCE is used to compute a multi-domain path based on the domain
   connectivity information.  A child 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.

   [I-D.ietf-pce-stateful-hpce] introduces general considerations for
   stateful PCE(s) in hierarchical PCE architecture.  In particular, the
   behavior changes and additions to the existing stateful PCE
   mechanisms in the context of a H-PCE architecture.

   In Stateful H-PCE architecture, the Parent PCE receives a virtual
   network creation request by its client over its Northbound API. This
   VN is uniquely identified by an Association ID in VNAG as well as the



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   VIRTUAL-NETWORK name. This VN may comprise multiple LSPs in the
   network in a single domain or across multiple domains.

   As the Parent PCE computes the optimum E2E paths for each tunnel in
   VN, it MUST associate each LSP with the VN to which it belongs.
   Parent PCE sends a PCInitiate Message with this association
   information in the VNAG Object (See Section 4 for details). This in
   effect binds an LSP that is to be instantiated at the child PCE with
   the VN.

   Whenever changes occur with the instantiated LSP in a domain network,
   the domain child PCE reports the changes using a PCRpt Message in
   which the VNAG Object indicates the relationship between the LSP and
   the VN.

   Whenever an update occurs with VNs in the Parent PCE (via the
   client's request), the parent PCE sends an PCUpd Message to inform
   each affected child PCE of this change.

   The Child PCE could then use this association to optimize all LSPs
   belonging to the same VN association together. The Child PCE could
   further take VN specific actions on the LSPs such as relaxation of
   constraints, policy actions, setting default behavior etc. The parent
   PCE could also maintain all E2E LSP or per-domain path segments under
   a single VN association.

6. Implementation Status

   [Note to the RFC Editor - remove this section before publication, as
   well as remove the reference to RFC 7942.]

   This section records the status of known implementations of the
   protocol defined by this specification at the time of posting of this
   Internet-Draft, and is based on a proposal described in RFC 7942
   [RFC7942].  The description of implementations in this section is
   intended to assist the IETF in its decision processes in progressing
   drafts to RFCs.  Please note that the listing of any individual
   implementation here does not imply endorsement by the IETF.
   Furthermore, no effort has been spent to verify the information
   presented here that was supplied by IETF contributors.  This is not
   intended as, and must not be construed to be, a catalog of available
   implementations or their features.  Readers are advised to note that
   other implementations may exist.

   According to RFC 7942, "this will allow reviewers and working groups
   to assign due consideration to documents that have the benefit of
   running code, which may serve as evidence of valuable experimentation
   and feedback that have made the implemented protocols more mature. It



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   is up to the individual working groups to use this information as
   they see fit".

6.1.  Huawei's Proof of Concept based on ONOS

   The PCE function was developed in the ONOS open source platform. This
   extension was implemented on a private version as a proof of concept
   to ACTN.

   o  Organization: Huawei

   o  Implementation: Huawei's PoC based on ONOS

   o  Description: PCEP as a southbound plugin was added to ONOS.  To
      support ACTN, this extension in PCEP is used.  Refer
      https://wiki.onosproject.org/display/ONOS/PCEP+Protocol

   o  Maturity Level: Prototype

   o  Coverage: Full

   o  Contact: satishk@huawei.com

7. Security Considerations

      This document defines one new type for association, which do not
      add any new security concerns beyond those discussed in [RFC5440],
      [RFC8231] and [I-D.ietf-pce-association-group] in itself.

      Some deployments may find the Virtual Network Name and the VN
      associations as extra sensitive; and thus should employ suitable
      PCEP security mechanisms like TCP-AO [RFC5925] or [RFC8253].

8. IANA Considerations

8.1. Association Object Type Indicator

      This document defines a new association type, originally defined
      in [I-D.ietf-pce-association-group], for path protection.  IANA is
      requested to make the assignment of a new value for the sub-
      registry "ASSOCIATION Type Field" (request to be created in [I-
      D.ietf-pce-association-group]), as follows:

      Value     Name                        Reference

      TBD1      VN Association Type         [This I.D.]

8.2. PCEP TLV Type Indicator



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      This document defines a new TLV for carrying additional
      information of LSPs within a path protection association group.
      IANA is requested to make the assignment of a new value for the
      existing "PCEP TLV Type Indicators" registry as follows:

      Value     Name                        Reference

      TBD2      VIRTUAL-NETWORK-TLV         [This I.D.]

8.3. PCEP Error

      This document defines new Error-Type and Error-Value related to
      path protection association.  IANA is requested to allocate new
      error values within the "PCEP-ERROR Object Error Types and Values"
      sub- registry of the PCEP Numbers registry, as follows:

      Error-Type  Meaning

      6           Mandatory Object missing
                  Error-value=TBD3: VIRTUAL-NETWORK TLV missing [This
      I.D.]


9.  Manageability Considerations

9.1.  Control of Function and Policy

      An operator MUST BE allowed to mark LSPs that belong to the same
      VN. This could also be done automatically based on the VN
      configuration.

9.2.  Information and Data Models

      The PCEP YANG module [I-D.ietf-pce-pcep-yang] should support the
      association between LSPs including VN association.

9.3.  Liveness Detection and Monitoring

      Mechanisms defined in this document do not imply any new liveness
      detection and monitoring requirements in addition to those already
      listed in [RFC5440].

9.4.  Verify Correct Operations

      Mechanisms defined in this document do not imply any new operation
      verification requirements in addition to those already listed in
      [RFC5440].




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9.5.  Requirements On Other Protocols

      Mechanisms defined in this document do not imply any new
      requirements on other protocols.

9.6.  Impact On Network Operations

      Mechanisms defined in this document do not have any impact on
      network operations in addition to those already listed in
      [RFC5440].

10. References

10.1. 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.

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

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
             2119 Key Words", BCP 14, RFC 8174, May 2017.

   [RFC8231] E. Crabbe, I. Minei, J. Medved, and R. Varga, "PCEP
             Extensions for Stateful PCE", RFC 8231, September 2017.

   [RFC8281] E. Crabbe, et. al., "PCEP Extensions for PCE-initiated LSP
             Setup in a Stateful PCE Model", RFC 8281, December 2017.

   [I-D.ietf-pce-association-group] I, Minei, Ed., "PCEP Extensions for
             Establishing Relationships Between Sets of LSPs", draft-
             ietf-pce-association-group, work in progress.

10.2. Informative References

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

   [RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
             Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
             June 2010, <https://www.rfc-editor.org/info/rfc5925>.

   [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



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             2012.

   [RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
             Code: The Implementation Status Section", BCP 205, RFC
             7942, DOI 10.17487/RFC7942, July 2016.

   [RFC8453] Ceccarelli, D., Ed. and Y. Lee, Ed., "Framework for
             Abstraction and Control of TE Networks (ACTN)", RFC 8453,
             DOI 10.17487/RFC8453, August 2018, <https://www.rfc-
             editor.org/info/rfc8453>.

   [RFC8637] Dhody D., Lee Y., and D. Ceccarelli, "Applicability of Path
             Computation Element (PCE) for Abstraction and Control of TE
             Networks (ACTN)", RFC 8637, July 2019,<https://www.rfc-
             editor.org/info/rfc8637> .

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


   [RFC5541]  Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of
              Objective Functions in the Path Computation Element
              Communication Protocol (PCEP)", RFC 5541,
              DOI 10.17487/RFC5541, June 2009,
              <http://www.rfc-editor.org/info/rfc5541>.

   [RFC7470]  Zhang, F. and A. Farrel, "Conveying Vendor-Specific
              Constraints in the Path Computation Element Communication
              Protocol", RFC 7470, DOI 10.17487/RFC7470, March 2015,
              <http://www.rfc-editor.org/info/rfc7470>.

   [RFC8051]  Zhang, X., Ed. and I. Minei, Ed., "Applicability of a
              Stateful Path Computation Element (PCE)", RFC 8051,
              DOI 10.17487/RFC8051, January 2017,
              <http://www.rfc-editor.org/info/rfc8051>.

   [RFC8253]  Lopez, D., Dios, O., Wu, W., and D. Dhody, "Secure
              Transport for PCEP", RFC 8253, October 2017 .

   [I-D.ietf-pce-pcep-yang]
              Dhody, D., Hardwick, J., Beeram, V., and j.
              jefftant@gmail.com, "A YANG Data Model for Path
              Computation Element Communications Protocol (PCEP)",
              draft-ietf-pce-pcep-yang (work in progress).






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 Contributor's Addresses

   Dhruv Dhody
   Huawei Technologies
   Divyashree Technopark, Whitefield
   Bangalore, Karnataka  560066
   India

   Email: dhruv.ietf@gmail.com

   Qin Wu
   Huawei Technologies
   China

   Email: bill.wu@huawei.com

   Xian Zhang
   Huawei Technologies
   China

   Email: zhang.xian@huawei.com

 Author's Addresses

   Young Lee
   Sung Kyun Kwan University (SKKU)
   Seoul South Korea

   Email: younglee.tx@gmail.com

   Haomian Zheng
   Huawei Technologies
   China

   Email: zhenghaomian@huawei.com

   Daniele Ceccarelli
   Ericsson
   Torshamnsgatan,48
   Stockholm,
   Sweden

   Email: daniele.ceccarelli@ericsson.com








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