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Versions: 00 01 02                                                      
Individual                                                      S. Homma
Internet-Draft                                              H. Nishihara
Intended status: Informational                                       NTT
Expires: August 5, 2019                                      T. Miyasaka
                                                           KDDI Research
                                                                A. Galis
                                               University College London
                                                               V. Ram OV
                                   Independent Research Consultant India
                                                                D. Lopez
                                                    L. Contreras-Murillo
                                                       J. Ordonez-Lucena
                                                          Telefonica I+D
                                                       P. Martinez-Julia
                                                                L. Qiang
                                                     Huawei Technologies
                                                                R. Rokui
                                                            L. Ciavaglia
                                                               X. de Foy
                                                       InterDigital Inc.
                                                        February 1, 2019

                     Network Slice Provision Models


   Network slicing is an approach to provide separate virtual network
   based on service requirements.  It's a fundamental concept of the 5G,
   and the architecture and specification is under standardization in
   several organizations.  However, the definitions and scopes of
   network slicing vary to some degree from one organization to another.
   This document provides classification of provisioning models of
   network slice for clarifying the differences on the definitions and

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 https://datatracker.ietf.org/drafts/current/.

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   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 August 5, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   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 and Motivation . . . . . . . . . . . . . . . . .   3
     1.1.  Differentiated Roles in Network Slice Provisioning  . . .   3
     1.2.  High-level Problem Statement  . . . . . . . . . . . . . .   4
   2.  Definition of Terms . . . . . . . . . . . . . . . . . . . . .   4
   3.  General Requirements for Network Slicing  . . . . . . . . . .   7
   4.  Network Slice Structure . . . . . . . . . . . . . . . . . . .   7
     4.1.  Resources for Structuring Network Slices  . . . . . . . .   7
     4.2.  Basic Network Slice Structure . . . . . . . . . . . . . .  11
     4.3.  Stakeholders in the Structuring Network Slices  . . . . .  14
   5.  Variations of Network Slice Creation  . . . . . . . . . . . .  14
     5.1.  Ready-made Network Slice  . . . . . . . . . . . . . . . .  14
     5.2.  Custom-made Network Slice . . . . . . . . . . . . . . . .  15
     5.3.  semi-Custom-made Network Slice  . . . . . . . . . . . . .  15
   6.  Network Slice Provision Models  . . . . . . . . . . . . . . .  15
     6.1.  Three Provision Models  . . . . . . . . . . . . . . . . .  15
     6.2.  Configurable Parameters/Attributes on each Provision
           Models  . . . . . . . . . . . . . . . . . . . . . . . . .  18
     6.3.  Capability of NS Tenant on each Provision Model . . . . .  18
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  18
   8.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  18
   9.  Acknowledgement . . . . . . . . . . . . . . . . . . . . . . .  18
   10. Informative References  . . . . . . . . . . . . . . . . . . .  18
   Appendix A.  NS Structure in the 3GPP 5GS . . . . . . . . . . . .  20
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  20

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1.  Introduction and Motivation

   Network slicing is an approach to provide separate virtual networks
   depending on requirements of each service.  Network slicing receives
   attention due to factors such as diversity of services and devices,
   and it is also a fundamental concept of the 5G for applying networks
   to such various types of requirements.

   In addition, network slicing is expected to enable a business model
   to provide dedicated logical networks to 3rd parties or vertical
   customers on-demand, called NSaaS (Network Slice as a Service).  For
   such usage, in network slicing, provision of networks able to
   guarantee communication characteristics end to end would be required.
   However, the definitions are not harmonized over several SDOs
   (Standards Developing Organizations).

   This document clarifies provision patterns of network slice, and
   provides the definitions and scope of network slicing which are
   available over several organizations.  Furthermore, the deliverables
   would be help for evaluating applicabilities of existing
   technologies/solutions to network slicing.

1.1.  Differentiated Roles in Network Slice Provisioning

   The widespread of system and network virtualization technologies has
   conducted to new business opportunities, enlarging the offer of IT
   resources in the form of Network Slices (NS).  As a consequence,
   there is a clear differentiation between the owner of physical
   resources, the infrastructure operator, and the intermediary that
   conforms and delivers network services to the final customers, the
   Virtual Network Operator (VNO).

   VNOs aim to exploit the virtualized infrastructures to deliver new
   and improved services to their customers.  However, current NS
   techniques offer poor support for VNOs to control their resources.
   It has been considered that the infrastructure operator is
   responsible of the reliability of the NS elements but several
   situations advocate the VNO to gain a finer control on its resources.
   For instance, dynamic events, such as the identification of new
   requirements or the detection of incidents within the virtual system,
   might urge a VNO to quickly reform its virtual infrastructure and
   resource allocation.  However, the interfaces offered by current
   virtualization platforms do not offer the necessary functions for
   VNOs to perform the elastic adaptations they require to tackle with
   their dynamic operation environments.

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1.2.  High-level Problem Statement

   Beyond their heterogeneity, which can be resolved by software
   adapters, NS platforms do not offer common methods and functions, so
   it is difficult for the virtual network controllers used by the VNOs
   to actually manage and control virtual resources instantiated on
   different platforms, not even considering different infrastructure
   operators.  Therefore, it is necessary to reach a common definition
   of the functions that should be offered by underlying platforms to
   enable such overlay controllers with the possibility of allocate and
   deallocate resources dynamically and get monitoring data about them.

   Such common methods should be offered by all underlying controllers,
   regardless of being network-oriented (e.g., ODL, ONOS, Ryu) or
   computing-oriented (e.g., OpenStack, OpenNebula, Eucalyptus).
   Furthermore, it is also important for those platforms to offer some
   "PUSH" function to report resource state, avoiding the need for the
   VNO's controller to "POLL" for such data.  A starting point to get
   proper notifications within current REST APIs could be to consider
   the protocol proposed by the [WEBPUSH-WG].

   Finally, in order to establish a proper order and allow the
   coexistence and collaboration of different systems, a common ontology
   regarding network and system virtualization should be defined and
   agreed, so different and heterogeneous systems can understand each
   other without requiring to rely on specific adaptation mechanisms
   that might break with any update on any side of the relation.

2.  Definition of Terms

   This section lists definitions and terms related to network slicing.
   Although this document refers terms and viewpoints on network slicing
   in 3GPP documents ([TS.28.530-3GPP] and [TS.28.801-3GPP]) and
   [NGMN-5G-White-Paper], some of definitions in this document may be
   different from ones of those documents.

   Network Slicing:  Network slicing indicates a technology, an
      approach, or a concept to create logical separate networks in
      support of services, depending on several requirements, on the
      same physical resources.  This is possible by combinations of
      several network technologies.

   Network Slice (NS):  An NS is a general name of logical separate
      networks instantiated on a network infrastructure.  It includes
      Network Slice Instance, Network Slice Subnet Instance, and End-to-
      End Network Slice Instance.

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   Network Slice Instance (NSI):  An NSI is a logical network
      instantiated with network(WAN) and computing(NFVI), and some
      include additional network service functions such as firewall or
      load-balancer.  It is composed of one or more Network Slice Subnet
      Instances.  When it provides connectivity from end to end for end
      users, it is called End-to-End Network Slice Instance.  An NSI is
      basically an overlay network and is independent of the underlay
      network's topology.

   Network Slice Subnet Instance (NSSI):  An NSSI is a partially virtual
      network instantiated within a single domain, and it basically
      provides connectivity to other domains or end points.  Ways to
      construct an NSSI depends on the specifications of underlay

   End-to-End Network Slice Instance (E2E-NSI):  An E2E-NSI is a virtual
      network connecting among end points.  It is composed of one or
      multiple NSSIs.  This term is used in this document when it should
      be emphasized that the NSI is structured from end to end.  As an
      example, for providing an E2E-NSI on the 3GPP 5G network,
      combining three types of NSIs: RAN-, TRN-, and CN-NSIs would be

   Transport(TRN)-NSSI:  A set of connections between various network
      functions (VNF or PNF) with deterministic SLAs.  They can be
      implemented (aka realized) with various technologies (e.g.  IP,
      Optics, FN, Microwave) and various transport (e.g.  RSVP, Segment
      routing, ODU, OCH etc).  The overview of NSI composed with TRN-
      NSSI is shown in Appendix A.

   RAN-NSSI:  Regardless of RAN deployment (e.g. distributed-RAN,
      Centralized-RAN or Cloud-RAN, a RAN-NSSI creates a dedicate and
      logical resource on RAN for each NSI which are completely.  The
      overview of NSI composed with RAN-NSSI is shown in Appendix A.

   Core(CN)-NSSI:  Regardless of Core deployment, a CN-NSI creates a
      dedicate and logical resource on Core network for each NSI which
      are completely.  The overview of NSI composed with CN-NSSI is
      shown in Appendix A.

   Network Slice as a Service (NSaaS):  An NSaaS is a service delivery
      model in which a third-party provider or a vertical customer hosts
      NSIs and makes them available to customers.  In this model, there
      mainly two roles: NS provider and NS tenant.

   Network Slice Provider (NS Provider):  An NS provider is a person or
      group that designs and instantiates one or more NSIs/NSSIs, and
      provides them to NS tenants.  In some cases, an NS provider is an

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      infrastructure operator simultaneously.  This includes NSI, NSSI,
      and E2E-NSI providers.

   Network Slice Tenant (NS Tenant):  An NS tenant is a person or group
      that rents and occupies NSIs from NS providers.

   Network Slice Stakeholder (NS Stakeholder):  An NS stakeholder is an
      actor in network slicing, and has roles of either NS provider or

   Infrastructure Operator:  An infrastructure operator is an
      organization who manages infrastructure networks or data centers
      for running NSIs.  In the most of cases, infrastructure operators
      are initial NS providers on NSaaS.  Also, some of them may be NS
      tenants simultaneously.

   Vertical Customer:  A vertical customer is a organization who
      provides some communicating services with using NSIs on NSaaS
      model.  In many cases, a vertical customer become the final NS
      tenant on NSaaS.  For example, video gaming companies or vehicle
      vendors will possibly be vertical customers.

   Virtual Network Operator (VNO):  A VNO is a person or group that
      operates virtual networks composed with resources or NSSIs rent
      from infrastructure operators and provides such virtual networks
      as NSIs to vertical customers who are final NS tenants.  In some
      cases, infrastructure operators have this role in addition to
      operating their own infrastructure simultaneously.

   Domain:  A domain is a group of a network and devices administrated
      under a policy-based common set of rules and procedures.

   Resource:  A resource is an element used to create virtual networks.
      There are several types of resources, i.e., connectivity,
      computing and storage.  The details are described Section 4.1

   Virtual Network:  A virtual network is a network running a number of
      virtual network functions.

   Virtual Network Function (VNF):  A virtual network function (VNF) is
      a network function whose functional software is decoupled from
      hardware.  One or more VNFs run as different software and
      processes on top of industry-standard high-volume servers,
      switches and storage, or cloud computing infrastructure.  They are
      capable of implementing network functions traditionally
      implemented via custom hardware appliances and middleboxes (e.g.,
      router, NAT, firewall, load balancer, etc.).

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   Network Operation System:  A network operation system is an entity or
      a group of entities for operating network nodes and functions as
      compositions of infrastructure network.  For example, OSS/BSS,
      orchestrator, and EMS are considered to be network operation

3.  General Requirements for Network Slicing

   On network slice operations, capabilities for dynamic instantiation,
   change, and deletion should be required because an NSI is established
   based on received orders from tenants in NSaaS.  From this aspect,
   some mechanisms to design a network based on service requirements and
   to convert those to concrete configurations based on the design would
   be required.

   In addition, each NS has to maintain concrete communication
   characteristics end to end, and resource reservations on data plane
   and isolation among NSIs would be required.  Isolation is a concept
   to prevent the reduction of communication quality caused by
   disturbance from other NSs, and it may have some levels of
   enforcement, such as hard or soft isolations.  In some cases, for
   providing appropriate communication between client and server, it
   would be allowed for NS tenants to put their applications as contents
   server on NSIs by using computing resources.

   The required agility of slice operation and granularity of end to end
   communication quality requested can vary depending on provision

4.  Network Slice Structure

   This section describes resources used for structuring NSs and the
   basic structure of E2E-NS.

4.1.  Resources for Structuring Network Slices

   A network slice is structured as combinations of the resources it
   uses.  Such resources are mainly categorized into three classes:
   network/WAN, computing/NFVI, and functionality resources.  Variations
   of each resources are described below.  (Note that the lists are not

   Network(WAN) Resources:

      *  Connectivity:

         +  (v)Link

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            -  Bandwidth per link/session

            -  Connected area/end points

            -  Forwarding route/path (e.g., for traffic engineering,

            -  Communication Priority (e.g., QoS class)

            -  Range of jitter amount

         +  Interface of vNode

            -  QoS setting (e.g., Queue size, DSCP remarking, PIR/CIR)

            -  Filter setting

         +  vRouter/vSwitch (# Treated as a set of (v)links and
            interfaces of vNodes.)

      *  Multicast support

      *  Encryption support

      *  Authentication support

      *  Metadata conveyance (e.g., subscriber ID)

      *  Protocols for slice data plane:

         +  VLAN

         +  IPoE (IPv4 or IPv6)

         +  MAP-E

         +  DS-Lite

         +  PPPoE

         +  L2TP

         +  GRE

         +  MPLS

         +  VxLAN

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         +  Geneve

         +  GTP-U

         +  Segment Routing MPLS

         +  Segment Routing IPv6

         +  NSH

         +  Other

   Computing(NFVI) Resources:

      *  (v)CPU core

      *  Storage

      *  Memory

      *  Disk

      *  vNIC

      *  Connectivity to VNF instances

      *  Virtual Deployment Unit:

         +  Virtual Machine (VM)

         +  container

         +  micro kernel

      *  Resource Deployment Location (i.e., edge DC, central DC, public
         cloud, ..., etc.)

   Functionality Resources:

      *  Image:

         +  Data Plane(DP) NF:

            -  GateWay(GW) function:

               o  Access Point Type (e.g., for radio, Wi-Fi, and fixed

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               o  Slice Selection Setting

               o  Terminate protocol

               o  Authentication

            -  Security Appliance:

               o  IPS (Intrusion Prevention System)

               o  IDS (Intrusion Detection System)

               o  WAF (Web Application Firewall)

            -  DPI

            -  Load Balancer

            -  TCP Accelerator

            -  Video Optimizer

            -  Parental Control

            -  Mobile DP functions (Ref. 3GPP 5GS)



                  Uplink Classifier

         +  Control Plane(CP) NF:

            -  DHCP

               o  Fixed IP address allocation

               o  Dynamic IP address allocation

               o  The number of registered devices

            -  DNS

            -  VoIP (SBC, SIP server)

            -  Mobile CP function (Ref. 3GPP 5GS)

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               o  AMF (Access and Mobility management Function)

               o  SMF (Session Management Function)

               o  PCF (Policy Control Function)

               o  UDM (Unified Data Management)

               o  NEF (Network Exposure Function)

      *  Provided VNF Type (e.g., open source, product of vender#A, ...,

      *  Function location (e.g., edge DC, central DC, Public cloud,

   In terms of security or usability for NS tenants, some abstraction on
   resource information would be required, however both setting
   parameters of underlay infrastructure and abstracted information may
   coexist in these lists.

   For abstraction of parameters of underlay networks, some additional
   protocols or functions (like [RFC8453] ) would be required.
   Moreover, for providing strict communication qualities, combinations
   of some technologies may be useful (ref.

4.2.  Basic Network Slice Structure

   An E2E-NSI is constructed by stitching NSSIs instantiated on each
   participating domain.  This includes the simplest case of a single
   NSSI as an E2E NS.  Domain types where some NSSIs are established are
   described below:

   o  Fixed access network

   o  Mobile access network

   o  Transport network

   o  Fixed core network

   o  Mobile core network

   o  Data center (DC)

      *  Edge DC

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      *  Central DC

   o  Private network

      *  Enterprise

      *  Factory

      *  Utilities

      *  Farming

      *  Home/SOHO

      *  Other

   Figure 1 describes the overview of this structure.  Resources in each
   domain (e.g., access, core networks, and DC) are handled by
   management entities and constitute an NSSI.  An E2E-NSI is
   established by stitching these NSSIs.  Ways to stitch NS-subnets are
   described in [I-D.defoy-coms-subnet-interconnection] and

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              /                                          /
                  A              A              A
                  |              |              |

               ____________   ___________   ______________
              /           /  /          /  /             /
             /___________/  /__________/  /_____________/
                NSSI#1         NSSI#2         NSSI#3
                  A              A              A
                  |              |              |

              o---o         [PNF]              /----[VM]
                 / `--.     /  `----.         /----[VM]
             NW Rsrc#1     NW Rsrc+PNF      NW+CMP Rsrcs
                 A               A              A
                 |               |              |

             ,--------.     ,--------.    ,-----------.
            / Access   \   / Core     \  /             \
            | Network  |   | Network  |  |  DC Domain  |
            \ Domain   /   \ Domain   /  \             /
             `--------'     `--------'    `-----------'

             NW Rsrc : Network Resource
             CMP Rsrc: Computing Resource
              o   : virtual/physical node structuring NSI
              --  : virtual/physical link structuring NSI
             [PNF]: Physical Network Function Appliance on NSI
             [VM] : Virtual Machine Instance on NSI

                    Figure 1: Overview of NS Structure

   Although it is shown that an NSSI belongs to just only one E2E-NSI in
   Figure 1, it may be allowed that multiple E2E-NSIs share an NSSI.
   Some resources may belong to multiple NSSI as well.

   In addition, structure on composition of NSI may be recursive.  In
   other words, even though Figure 1 shows a case where NSSIs compose
   directly an E2E-NSI, in some cases, NSSIs compose an NSI which is a
   part of an E2E-NSI.  The overview is shown in Figure 2.  In this
   figure, NSI#4 is composed of NSSI#1 and NSSI#2, and it structures
   E2E-NSI#5 with NSSI#3.

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                /                                          /
                             A                    A
                             |                    |
                 ___________________________      |
                /                          /      |
               /__________________________/       |
                 NSI#4 (= NSSI#1 + NSSI#2)        |
                    A              A              |
                    |              |              |
                 ____________   ___________   _____________
                /           /  /          /  /            /
               /___________/  /__________/  /____________/
                  NSSI#1         NSSI#2         NSSI#3

               Figure 2: Overview of NS recursive structure

4.3.  Stakeholders in the Structuring Network Slices

   Potential stakeholders in network slicing are described below:

   o NSSI provider:  infrastructure operator

   o Intermediate-NSI provider:  infrastructure operator, VNO

   o E2E-NSI provider:  infrastructure operator, VNO, service provider

   o NS tenant:  infrastructure operator, VNO, service provider,
      enterprise, mass user

   o End customer:  enterprise, mass user, etc.

5.  Variations of Network Slice Creation

   NSs can be classified according to their creation pattern into two
   types: ready-made(RM) NS, custom-made(CM), and semi-custom-made(sCM)
   NS.  This section describes the features of these types.

5.1.  Ready-made Network Slice

   RM-NS is an NS creation pattern in which an infrastructure operator
   decides service requirements by itself, and established based on the
   requirements in advance.  NS tenants select one of RM-NSs whose
   features are closer to their requirements.

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   This model doesn't need immediacy on designing of NSI and enables to
   mitigate the difficulty of implementation compared with other models.

5.2.  Custom-made Network Slice

   CM-NS is an NS creation pattern in which an NS is established based
   on an order from a tenant and is provided to it.  As examples of
   usage of CM-NS, an enterprise builds and operates a virtual private
   network for connecting several bases, or OTT (Over The Top) or other
   industrial service providers create NSs based on their own
   requirements and use them as a part of their own services (e.g.,
   connected vehicles/drones, online video games, or remote surgery).

   In this model, network operation system would be required to have
   incorporate intelligence for designing appropriate NSs on-demand.

5.3.  semi-Custom-made Network Slice

   sCM-NS is a derivation of a CM-NS.  In sCM-NS, an NS provider designs
   the outline of NSs in advance, and a tenant tunes an NS with deciding
   some parameters or applications run on resources.  For example, an
   infrastructure operator designs a logical network presenting
   connectivity, and tenants install their own applications on servers
   running on the logical network.

6.  Network Slice Provision Models

   This document classifis NS provision models into three categories
   defined in the following section.  The capabilities which NS tenants
   can have on management of NSs would vary depending on the selected
   provision model.

6.1.  Three Provision Models

   The provision models are categorized into three models: SaaS
   (Software as a Service), PaaS (Platform as a Service), IaaS
   (Infrastructure as a Service) like models as below.

   SaaS-like Model:  In this model, an NS provider designs NS templates
      in advance, and a tenant selects and uses one which fulfills most
      its requirement among the templates.  The specifications of NSs
      are abstracted to KPIs as networks and servers and shown to
      tenants.  In short, detailed parameters of infrastructure network
      are hidden from tenants.

   PaaS-like Model:  In this model, a tenant makes its request,
      including connected area, path routes, the KPIs, and included
      service functions, and a NS provider designs an NS template and

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      instantiate an NS based on the request dynamically.  The
      configurable values would vary depending on the policy of each NS

   IaaS-like Model:  In this model, a tenant designs its own NS
      templates and instantiates NSs by indicating concrete resources to
      infrastructure operators.  In other words, infrastructure
      operators provide just their resources, and NSs are coordinated by
      the tenant.

   An example of mapping of each NS provision model is shown in
   Figure 3.

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                           [NS Tenant] ---------------------------+
       . . . . . . . . . . . . . . . . . . . . . . . .            |
       *Service Layer                                             |
                                            .--.                  |
        .------.                           (    )-.               |
       | Area#A |<==== Connectivity ====> .' [APL] '     SaaS-like|
        `------' [BW:100Mbps, Delay<10ms](           )  <---------+
        .------.                          (  [APL] -'             |
       | Area#B |<==== Connectivity ====>  '-(     )              |
        `------' [BW:100Mbps, Delay<10ms]     '---'               |
                                        Virtual Private           |
                                             Cloud                |
       . . . . . . . . . . . . . . . . . . . . . . . .            |
       *NS Layer                                                  |
                  __________________________________              |
                 /                                 /              |
                / [AP]----o                       /      PaaS-like|
               /         / `--.     /---[VM]     /      <---------+
              /  [AP]---o-----o--[FW]--[VM]     /                 |
             /_________________________________/                  |
                              NSI                                 |
       . . . . . . . . . . . . . . . . . . . . . . . .            |
       *Infra Layer                                               |
                  [AP]----o          /---[SV]                     |
                         / `--.     /---[SV]             IaaS-like|
                 [AP]---o-----o--[FW]--[SV]             <---------+
                         .---'    /---[SV]

         o  : virtual/physical node
         -- : virtual/physical link
         [AP] : Access point
         [APL]: Application owned by NS Tenant
         [FW] : Firewall Function
         [VM] : Virtual Machine Instance on Sever
         [SV] : Server as Infrastructure

                 Figure 3: Mapping of NS provision models

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   In some cases, NSIs provided based on IaaS- or PaaS-like models are
   coordinated to a form of SaaS-like model by an NS broker , and the NS
   broker or by the tenant, becoming a NS provider in a recursive
   manner.  For example, a vertical customer sends its high-level
   requirements to an NS broker create an appropriate NSI with resources
   provided by infrastructure operators.

6.2.  Configurable Parameters/Attributes on each Provision Models


6.3.  Capability of NS Tenant on each Provision Model


7.  Security Considerations

   In NSaaS, parts of controls of infrastructures are opened to
   externals, and thus some mechanisms, such as authentication for APIs,
   to prevent illegal access would be required.

   Other considerations are TBD

8.  IANA Considerations

   This memo includes no request to IANA.

9.  Acknowledgement

   The author would like to thank Toru Okugawa for his kind review and
   valuable feedback.

10.  Informative References

              Foy, X., Rahman, A., Galis, A.,
              kiran.makhijani@huawei.com, k., and L. Qiang,
              "Interconnecting (or Stitching) Network Slice Subnets",
              draft-defoy-coms-subnet-interconnection-01 (work in
              progress), October 2017.

              Dong, J., Bryant, S., Li, Z., Miyasaka, T., and Y. Lee, "A
              Framework for Enhanced Virtual Private Networks (VPN+)
              Service", draft-dong-teas-enhanced-vpn-03 (work in
              progress), November 2018.

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              Homma, S., Foy, X., and A. Galis, "Gateway Function for
              Network Slicing", draft-homma-nfvrg-slice-gateway-00 (work
              in progress), July 2018.

              NGMN, "NGMN 5G White Paper", February 2015,

   [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,

              3rd Generation Partnership Project (3GPP), "3GPP TS 23.501
              (V15.3.0): System Architecture for 5G System; Stage 2",
              September 2018, <http://www.3gpp.org/ftp//Specs/

              3rd Generation Partnership Project (3GPP), "3GPP TS 28.530
              (V1.0.0): Management and orchestration of networks and
              network slicing; Concepts, use cases and requirements
              (work in progress)", June 2018,

              3rd Generation Partnership Project (3GPP), "3GPP TS 28.541
              (V15.1.0): 5G Netowkr Resource Model (NRM); Stage 2 and
              stage 3 (Release 15)", June 2018,

              3rd Generation Partnership Project (3GPP), "3GPP TS 28.801
              (V15.1.0): Study on Management and Orchestration of
              Network Slicing for next generation network (Release 15)",
              June 2018, <http://www.3gpp.org/ftp//Specs/

              IETF, "Web-Based Push Notifications(webpush)",

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Appendix A.  NS Structure in the 3GPP 5GS

   The overview of structure of NS in the 3GPP 5GS is shown in Figure 4.
   The terms are described in the 3GPP documents (e.g., [TS.23.501-3GPP]
   and [TS.28.530-3GPP]).

   <==================          E2E-NSI         =======================>
                :                 :                  :           :  :
                :                 :                  :           :  :
   <======  RAN-NSSI  ======><=TRN-NSSI=><====== CN-NSSI  ======>VL[APL]
       :        :        :        :         :       :        :   :  :
       :        :        :        :         :       :        :   :  :
   RW[NFs ]<=TRN-NSSI=>[NFs ]<=TRN-NSSI=>[NFs ]<=TRN-NSSI=>[NFs ]VL[APL]

    . . . . . . . . . . . . ..          . . . . . . . . . . . . ..
    .,----.   ,----.   ,----..  ,----.  .,----.   ,----.   ,----..
 UE--|RAN |---| TN |---|RAN |---| TN |---|CN  |---| TN |---|CN  |--[APL]
    .|NFs |   `----'   |NFs |.  `----'  .|NFs |   `----'   |NFs |.
    .`----'            `----'.          .`----'            `----'.
    . . . . . . . . . . . . ..          . . . . . . . . . . . . ..

   RW         RAN                MBH               CN               DN

  UE: User Equipment
  RAN: Radio Access Network
  CN: Core Network
  DN: Data Network
  TN: Transport Network
  MBH: Mobile Backhaul
  RW: Radio Wave
  NF: Network Function
  APL: Application Server

             Figure 4: Overview of Structure of NS in 3GPP 5GS

Authors' Addresses

   Shunsuke Homma

   Email: shunsuke.homma.fp@hco.ntt.co.jp

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   Hidetaka Nishihara

   Email: nishihara.hidetaka@lab.ntt.co.jp

   Takuya Miyasaka
   KDDI Research

   Email: ta-miyasaka@kddi-research.jp

   Alex Galis
   University College London

   Email: a.galis@ucl.ac.uk

   Vishnu Ram OV
   Independent Research Consultant India

   Email: vishnu.u@ieee.org

   Diego R. Lopez
   Telefonica I+D

   Email: diego.r.lopez@telefonica.com

   Luis M. Contreras-Murillo
   Telefonica I+D

   Email: luismiguel.contrerasmurillo@telefonica.com

   Jose A. Ordonez-Lucena
   Telefonica I+D

   Email: joseantonio.ordonezlucena@telefonica.com

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   Pedro Martinez-Julia

   Email: pedro@nict.go.jp

   Li Qiang
   Huawei Technologies

   Email: qiangli3@huawei.com

   Reza Rokui

   Email: reza.rokui@nokia.com

   Laurent Ciavaglia

   Email: Laurent.ciavaglia@nokia.com

   Xavier de Foy
   InterDigital Inc.

   Email: Xavier.Defoy@InterDigital.com

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