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Versions: 00                                                            
nfvrg                                                            L. Wang
Internet-Draft                                                   L. Geng
Intended status: Informational                              China Mobile
Expires: January 3, 2019                                   July 02, 2018

        Review of Network Slicing Research in Diverse Standards


   As one of the significant technology in 5G, there are diverse
   industry communities and standard organizations dedicated in a
   research of Network Slicing, such as IETF, 3GPP, GSMA, ETSI, etc..
   These organizations and communities not only standardize network
   slicing architecture, management, requirements and so on, but also
   individually focus on specifying network slicing in their own ways,
   offering diverse specifications of it.  Aiming at research on a
   overall review of network slicing standard, this document discuss
   diverse standards in various organizations and communities,
   furthermore, analyzing the emphasis and difference between them.

Status of This Memo

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   This Internet-Draft will expire on January 3, 2019.

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   This document is subject to BCP 78 and the IETF Trust's Legal
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   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents

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   carefully, as they describe your rights and restrictions with respect
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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  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Overview of Network Slicing Standard Progress . . . . . . . .   3
   4.  Detailed Diverse Network Slicing Standards  . . . . . . . . .   4
     4.1.  IETF  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
       4.1.1.  Network Slicing in IETF . . . . . . . . . . . . . . .   4
       4.1.2.  Information Model . . . . . . . . . . . . . . . . . .   5
     4.2.  3GPP  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
       4.2.1.  Network Slicing in 5G . . . . . . . . . . . . . . . .   6
       4.2.2.  Network Slice Operation Procedure . . . . . . . . . .   7
     4.3.  ETSI  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
     4.4.  GSMA  . . . . . . . . . . . . . . . . . . . . . . . . . .   9
   5.  Conclusion:Different Understanding and Emphasis of Each
       Organizations . . . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Informative References  . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   With the rapid development of 5G technology research and successful
   emergence of 5G market, network slicing is becoming one of
   significant technologies of 5G.  The mechanism of network slicing is
   that divide common physical network infrastructure into diverse
   isolated virtual network resources to meet the high level demands
   from different vertical industry.  With network slicing, providers
   are able to offer customized service to users in terms of bandwidth,
   latency, security and so on.  Network slicing mechanism enables 5G to
   integrate diverse network resources and multi-domain technologies, to
   meet various demands from vertical industry, offering the best-effort
   network service.  For instance, to achieve both determined latency
   and security requirements from some industry services, network
   slicing is likely to apply TSN[tsn] and blockchain technologies to
   satisfy the requirement.  Meanwhile, network resources such as high
   bandwidth and dedicated network tunnel can be supplied here to meet
   the demands as well which are all integrate in this network slice.

   As the key feature of 5G, the concept of network slicing is discussed
   in related standard organizations and communities. 3GPP release
   network slicing standard of architecture in specification
   [TR23.501]and management&orchestration in specification [TR28.801] .

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   3GPP also specify requirement, use cases and other related features
   of network slicing in different work groups.  Also, being so
   important to network technology progress, network slicing has gotten
   a lot of attention and heated discussion in IETF.  Several drafts are
   released and discussed in netslicing and COMS mailing list which will
   be talked in the following sections.  Besides, there are other
   organizations are doing research in network slicing, such as European
   Telecommunications Standards Institute (ETSI), Broadband Forum (BBF),
   GSM Association (GSMA), etc.  Each of them makes diverse definition
   and concern different areas of network slicing definition.

   It shows that network slicing has been defined by multiple Standards
   Definition Organizations (SDOs) and communities.  However, as a
   diversity of mission of each, the meaning and understanding of the
   network slicing concept are different from each other and there is no
   common definition.  In the following part of documents, an overview
   of network slicing research aspect will be discussed.  Furthermore,
   the emphasis and difference between each organization is analyzed as
   well.  This is aimed at giving out clear viewpoints of network
   slicing understanding from these organizations.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in [RFC2119].

   PLMN, Public Land Mobile Network, is a network that is established
   and operated by providers for the specific purpose of providing land
   mobile telecommunications services to the public.

   NSSAI, Network Slice Selection Assistance Information.  NSSAI
   provided by the Serving PLMN during a Registration procedure,
   indicating the S-NSSAIs values the UE could use in the Serving PLMN
   for the current registration area.

   S-NSSAI, Single Network Slice Selection Assistance Information.
   S-NSSAI identify a network slice.

3.  Overview of Network Slicing Standard Progress

   In this section, an overview of network slicing standard progress
   will be given out.

   IETF  Network slicing is discussed in terms of specification of
      terminology, architecture[draft-geng-coms-architecture-02], use
      cases[draft-qiang-coms-use-cases-00], problem statement and other
      aspects related to network slicing.  To map the gap between

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      technology-agnostic network slicing service requirements and
      specific implementation technologies, a technology independent
      information model is created.  Furthermore, aiming at converging
      bottom-up and top-down approaches on a technology-independent
      common management plane, COMS (Common Operation and Management on
      network Slices) is defined and described

   3GPP  Acknowledging network slicing as significant component of 5G
      process, 3GPP dedicated in making a thorough specification of
      network slicing concept since the very early time when they
      started considering 5G technology.  Network slicing is specified
      in SA1 (requirements), SA2 (architecture), SA3 (security) and SA5
      (network management) respectively, in which architecture and
      management will mainly be described the next paragraph.

   ETSI  ETSI analyses network slicing use cases defined in other SDOs
      and industry fora in Report on Network Slicing Support with ETSI
      NFV Architecture Framework [ETSI_GR_NFV-EVE], and give the
      description that how to map the use cases to the NFV architecture
      and concepts.

   GSMA  GSMA give the Concept of network slicing from a business way
      and indicate that how network slicing can serve and support 5G
      network in its report [GSMA-An-Introduction-to-Network-Slicing]

4.  Detailed Diverse Network Slicing Standards

4.1.  IETF

4.1.1.  Network Slicing in IETF

   In [draft-geng-netslices-architecture-02] , end to end network slice
   is defined as a cross-domain network slice which may consist of
   access network, transport network, (mobile) core network.  The
   concept here of network slice is expanded to a wider area and
   comprises of several functional components.  Driven by the multiple
   requirements from users, network slice instance may include several
   service components that each of which may require a set of network
   resources and attributes in form of a network slice.

   Network Slicing Management and Orchestration is comprised of:

      Template Management: A complete description of the structure,
      configuration and the plans/work flows for how to instantiate and
      control the network slice instance during its life cycle.

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      NS Repository: A policy to describe how user select network slice
      or how multi-slice instance associated with one network slice.

      Life cycle management and monitoring : Network slicing and slice
      instance must be full life cycle managed and monitored.

      E2E Orchestration: E2E Slices Orchestration and its functionality
      which can be a)Coordinating a number of interrelated resources,
      b)Autonomically control of slice life cycle management,
      c)Autonomically coordinate and trigger of slice elasticity and
      placement of logical resources in slices, d)Coordinates and (re)-
      configure logical resources.

      Domain Orchestration: In heterogeneous environment, network
      slicing is expected to orchestrate multiple domain technologies
      and resources to gain the most effective, dynamic and automatic

      NS Manager: Manager manages all access permissions and all
      interaction between a Network Slice and external functions which
      are specific for each network slice instance.

      Resource Registration: Responsible for the management of exposed
      capability of the network infrastructure.

   Under network slicing management and orchestration, the resource
   management which can be physical, logical and virtual resources will
   be mapped to the requirements and Capabilities users demands to
   create the related network slice instance.  The Capabilities of
   network slicing includes reclusiveness, protection, elasticity,
   extensibility, safety and isolation.

4.1.2.  Information Model

   However, sometimes customers, being not able to know or not familiar
   with the underlying networking resources and technologies, expect a
   technology-agnostic interface.  A information model here is in demand
   to fill the gap between technology-agnostic network slicing service
   requirements and specific implementation technologies.

   The information model for network slicing here is required to offer
   the capability that describe the entities that compose a network
   slice, their functions and the mechanism how they serve the
   corresponding network slice.  The information model provide the
   connectivity of undying technologies from providers and customers

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   requirements, and gives out a clear and complete informal diagrams of
   network slices entities and technologies in different domains.

4.2.  3GPP

   Here we only disscuss the architecture and management of Network
   slicing in 3GPP, which are mostly related to [TR23.501] and

4.2.1.  Network Slicing in 5G

   In 3GPP [TR23.501], a network slice is defined as an end to end
   logical communication network, within a Public Land Mobile Network
   (PLMN) and includes the Core Network (CN) Control Plane, User Plane
   Network Functions and 5G Access Network (AN).

   A singal UE(User Equipment) may be served by multiple slices
   simultaneously through a single RAN.  Correspondingly, network slices
   may vary for supported features and network functions optimisations
   because of different S-NSSAIs with different Slice/Service Types.  So
   provider may select to deploy multiple network slices, but offering
   same service feature, to serve a group of UEs.

   S-NSSAI, delivering identification and selection information of a
   network slice, is comprised of a Slice/Service type (SST) which
   refers to the expected Network Slice behaviour in terms of features
   and services and a Slice Differentiator (SD) which is optional
   information that complements the Slice/Service type(s) to
   differentiate amongst multiple Network Slices of the same Slice/
   Service type.  Network Slice instance can be associated with one or
   more S-NSSAIs, and an S-NSSAI can be associated with one or more
   Network Slice instances.SST value represents 3 service types that are
   eMBB (enhanced Mobile Broadband), URLLC (ultra- Reliable Low Latency
   Communications) and MIoT (Massive IoT) respectively.

   Figure 1 is a network slicing architecture in 5G.  For one network
   slice instance, UE selects a network slice by requesting a S-NSSAI
   via RAN (This will be given details in next section), and core
   network responds to allocate the corresponding slice.

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   Network Slice              +----------------------------------------------------------------------+
  Instance                   | +-----+   +-----+                   +----------|CORE|--------------+ |
 +------------+              | |     |   |     | Transmission      | +----+ +----+ +----+ +----+  | |
 |  eMBB      +--------------+ |UE   +---(R)AN +-------------------+ |UPF | |AMF | |SMF | |PCF |  | |slice1
 +------------+           +--+ |     |   |     | Bearing Network   | |    | |    | |    | |    |... |
                          |  | |     |   |     |                   | +----+ +----+ +----+ +----+  | |
 +------------+           |  | +-----+   +-----+                   +------------------------------+ |
 | URLLC      +-----------+ ++--------+--------------------------+----------------------------------+
 +------------+        +--+ |     |   |     |                    |                         |     |
                       |  | +-----+   +-----+                    +-------------------------+     | slice2
+-------------+        |  |                                                                      |
|  MIoT       +--------+  ++------+--+-----+------------------+------------------------+-----+---+
+-------------+        |   |      |  |     |                  |                        |     |
                       |   +------+  +-----+                  +------------------------+     |slice3
                       |                                                                     |

Figure 1

4.2.2.  Network Slice Operation Procedure

   The Network slicing operation procedure starts from UE registration,
   in which the selection of Network Slice instances for a UE is
   triggered by the first contacted Access and Mobility Management
   Function (AMF).  After AMF selected by the AN receives the UE
   Registration request, UE signals a requested NSSAI to AMF, and AMF is
   expected to determine whether it can serve the UE by verifying
   whether the S-NSSAI(s) in the Requested NSSAI are permitted based on
   the Subscribed S-NSSAIs.  If this case is permitted, AMF query the
   Network Slice Selection Function (NSSF), with Requested NSSAI,
   mapping of Requested NSSAI to Configured NSSAI.  The NSSF returns to
   the current AMF the Allowed NSSAI for the applicable Access Type(s)
   and UE, after receiving an Allowed NSSAI from the serving AMF, will
   store it.

   As the one of the most important goals of network slicing
   configuration, the Protocol Data Unit (PDU) Session Establishment in
   a Network Slice to a DN allows data transmission in a Network Slice.
   The data transmission works after a PDU session to a Data Network is
   established in a Network Slice.  Each PDU session corresponds to one
   core network slice and one RAN slice specifically.Here AMF is common
   to network slices serving the UE, but SMF and UPF are specific to
   each slice they associated to.

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                         |   UE    |
                   NSSAI      |
                         |   RAN   |
                              |RAN choose AMF with  NSSAI
                   NSSAI      |
   |                   AMF queries the NSSF                 |
   |    +--------+      with Requested NSSAI--------+       |
   |    |        +-------------------------^ NSSF   |       |
   |    |  AMF   <-------------------------+        |       |
   |    +--------NSSF returns to the       +--------+       |
   |    +-------+Allowed NSSAI                              |
   |    |  NRF  |                                           |
   |    +-------+                                           |
                              |      |
                              |      +-------++
                +-------------+------------+ |
                |                          | |
                | +-----+ +-----+ +-----+  +-++
                | |     | |     | |     |  |  |
                | |     | |     | |     |  |  |
                | |SMF  | |UPF  | | PCF ...|  |
                | |     | |     | |     |  |  |
                | |     | |     | |     |  |  |
                | |     | |     | |     |  |  |
                | +-----+ +-----+ +-----+  |  |
                |                          |  |
                +---+-------+--------------+  |
                    |       |                 |
                    |       |                 |
                            |    |
                         +--+-+  |
                         |DN1 |  |
                               | DN2  |

   Figure 2 Network Slice Operation

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4.3.  ETSI

   Rather than defining the standard of network slicing as well as other
   organizations, ETSI focuses on the mapping of the network slicing to
   NFV concept and describe how NFV architecture support it under the
   standards of diverse organization such as 3GPP.

   Under the 3GPP defination of network slicing, ETSI defines NFV-NS
   that represent the virtualized resources for the slice subnet and
   their connectivity to physical resources.  ETSI also describe Os-Ma-
   NFvo interface point that offer the interaction between the 3GPP
   slicing management and NFV-MANO, which is also related to a couple of
   management determination from NSMF and NSSMF.

4.4.  GSMA

   In [GSMA-An-Introduction-to-Network-Slicing], GSMA give the Concept
   of network slicing from the point of view of business customers that
   "Network slicing is the embodiment of the concept of running multiple
   logical networks as virtually independent business operations on a
   common physical infrastructure in an efficient and economical way."
   And they define that customisable network capabilities include data
   speed, quality, latency, reliability, security, and services.  It is
   also mentioned that different operators can share the same network
   slice in GSMA description.

5.  Conclusion:Different Understanding and Emphasis of Each

   Based on the above description of network slicing and its entities
   from different organizations, it is not hard to find that they
   provide a different understanding of network slicing concept and have
   their emphasis of research on it:

      In 3GPP, network slice is deployed in RAN, UPF and CN for a mobile
      network.  Network slice instance is created by the cooperation
      between RAN and CN, which is more like a customized sliced
      function in core network.  But the connectivity part, transmission
      network between CN and RAN is not sliced.

      IETF anticipates to define an broader applied end-to-end network
      slicing for not only mobile network, but also other networks forms
      which may not includes CN or RAN.  Therefore, the transmission
      network is considered as part of network slice resource/instance
      which can be sliced as well.  This may ask for a orchestration of
      multiple domain technologies in transmission network and a
      information model to expose the relating tech capabilities.

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      ETSI mainly focuses on the mapping between NFV function and
      network slice based on the network slicing definition from current
      organizations, while GSMA define network slicing in a general and
      business way.

   All of the descriptions from diverse organizations is attempting to
   give a comprehensive and typical standard for network slicing.

6.  Informative References

              "COMS Architecture", <https://datatracker.ietf.org/doc/

              "Network Slicing Architecture",

              "Technology Independent Information Model for Network
              Slicing", <https://datatracker.ietf.org/doc/

              "The Use Cases of Common Operation and Management of
              Network Slicing", <https://datatracker.ietf.org/doc/

              "Report on Network Slicing Support with ETSI NFV
              Architecture Framework Disclaimer",

              , <https://www.gsma.com/futurenetworks/wp-

              Boucadair, M., Jacquenet, C., Zhang, D., and P.
              Georgatsos, "Connectivity Provisioning Negotiation
              Protocol (CPNP)", draft-boucadair-connectivity-
              provisioning-protocol-15 (work in progress), December

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   [RFC2119]  "Key words for use in RFCs to Indicate Requirement

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,

              "System Architecture for the 5G System",

              "Telecommunication management;Study on management and
              orchestration of network slicing for next generation

   [tsn]      "Time-Sensitive Networking (TSN) Task Group",

Authors' Addresses

   Lei Wang
   China Mobile
   Beijing  100053

   Email: jifengyiwl@163.com

   Liang Geng
   China Mobile
   Beijing  100053

   Email: gengliang@chinamobile.com

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