No Working Group                                                A. Galis
Internet-Draft                                 University College London
Intended status: Informational                                   J. Dong
Expires: July 23, 2017                                      K. Makhijani
                                                               S. Bryant
                                                     Huawei Technologies
                                                            M. Boucadair
                                                       P. Martinez-Julia
                                                       February 14, 2017

 Network Slicing - Introductory Document and Revised Problem Statement


   This document introduces Network Slicing problems and the motivation
   for new work areas. It represents an initial revision of the Network
   Slicing problem statement derived from the analysis of the technical
   gaps in IETF protocols ecosystem.  It complements and brings together
   the silo efforts being carried out in several other IETF working groups
   to achieve certain aspects of Network Slicing functions and operations.

Status of This Memo

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   carefully, as they describe your rights and restrictions with respect
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Notes . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   2.  Suggested Problems and Work Areas . . . . . . . . . . . . . .   4
     2.1.  Notes . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   3.  Documents . . . . . . . . . . . . . . . . . . . . . . . . . .   7
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   Network Slicing (NS) refers to the managed partitions of physical
   and/or virtual network resources, network physical/virtual and
   service functions [RFC7665] that can act as an independent instance
   of a connectivity network and/or as a network cloud. Network resources
   include connectivity, compute, and storage resources.

   Network Slices considerably transform the networking perspective by
   abstracting, isolating, orchestrating, softwarizing, and separating
   logical network components from the underlying physical network
   resources and as such they enhance Internet architecture principles
   ([RFC1958], [RFC3439], [RFC3234]).

   The management plane creates the grouping of network resources (whereby
   network resources can be physical, virtual or a combination thereof),
   it connects with the physical and virtual  network and service functions
   ([SFC WG]) as appropriate, and it instantiates all of the network and
   service functions assigned to the slice. On the other hand, for slice
   operations, the slice control plane takes over the control and governing
   of all the network resources, network functions, and service functions
   assigned to the slice. It (re-) configures them as appropriate and as per
   elasticity needs, in order to provide an end-to-end service. In particular,
   ingress routers  are  configured so that appropriate traffic is bound to
   the relevant slice. Identification means for the traffic may be simple
   (relying on a subset of the transport coordinate, DSCP/traffic class, or
   flow label), or identification may be a more sophisticated one (to be
   further defined). Also, the traffic capacity that is specified for a slice
   can be changed dynamically, based on some events (e.g. triggered by a
   service request). The slice control plane is responsible for instructing
   the involved elements to honor such needs.

   Network operators can use NS to enable different services to receive
   different treatment and to allow the allocation and release of network
   resources according to the context and contention policy of the operators.
   Such an approach using NS would allow significant reduction of the operations
   expenditure. In addition NS makes possible softwarization, programmability
   ([RFC7149]), and the innovation necessary to enrich the offered services.
   Network softwarization techniques [IMT2020-2015], [IMT2020-2016] may be used

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   to realise and manage [MANO-2014] network slicing. NS provides the
   means for the network operators to provide network programmable
   capabilities to both OTT providers and other market players without
   changing their physical infrastructure. NS enables the concurrent
   deployment of multiple logical, self-contained and independent,
   shared or partitioned networks on a common infrastructure. Slices
   may support dynamic multiple services, multi-tenancy, and the
   integration means for vertical market players (e.g. automotive
   industry, energy industry, healthcare industry, media and
   entertainment industry, etc.)

   The purpose of the NS work in IETF is to develop a set of protocols and/
   or protocol extensions that enable efficient slice creation,
   activation / deactivation, composition, elasticity, coordination /
   orchestration, management, isolation, guaranteed SLA, and safe and secure
   operations within a connectivity network or network cloud / data centre
   environment that assumes an IP and/or MPLS-based underlay.

   While there are isolated efforts being carried out in several IETF
   working groups Network WG [I-D.leeking-actn-problem-statement 03], TEAS WG
   [I-D.teas-actn-requirements-04], [I-D.dong-network-slicing-problem-statement],
   ANIMA WG [I-D.galis-anima-autonomic-slice-networking], [IETF-Slicing1],
   [IETF-Slicing2], [IETF-Slicing3], [IETF-Slicing4], [IETF-Slicing5],[IETF-
   Mobility], [IETF-Virtualization], [IETF-Coding], [IETF-Anchoring] to
   achieve certain aspects of network slice functions and operations,
   there is a clear need to look at the complete life-cycle management
   characteristics of Network Slicing solutions though the discussions
   based on the following architectural tenets:

   o Underlay tenet: support for an IP/MPLS-based underlay data plane the
   transport network used to carry that underlay.

   o Governance tenet: a logically centralized authority for network
   slices in a domain.

   o Separation tenet: slices may be independent of each other and have
   an appropriate degree of isolation (note 1) from each other.

   o Capability exposure tenet: each slice allows third parties to
   access via dedicated interfaces  and /or APIs information regarding
   services provided by the slice (e.g., connectivity information, mobility,
   autonomicity, etc.) within the limits set by the operator.

   NS approaches that do not adhere to these tenets are explicitly
   outside of the scope of the proposed work at IETF.

   In pursuit of the solutions described above, there is a need to
   document an architecture for network slicing within both wide area
   network and data center environments.

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   Elicitation of requirements ([RFC2119], [RFC4364]) for both Network
   Slice control and management planes will be needed, facilitating
   the selection, extension, and/or development of the protocols for each
   of the functional interfaces identified to support the architecture.

   Additionally, documentation on the common use-cases for slice
   validation for 5G is needed, such as mission-critical ultra-low latency
   communication services; massive-connectivity machine communication
   services (e.g. smart metering, smart grid and sensor networks); extreme
   QoS; independent operations and management; independent cost and/or
   energy optimisation; independent multi-topology routing; multi-tenant
   operations; etc.

   The proposed NS work would be coordinated with other IETF WGs (e.g.
   DMM WG, Routing Area WG (RTGWG), Network Management Research Group
   (NMRG)and NFV Research Group (NFVRG)) to ensure that the commonalities
   and differences in solutions are properly considered. Where suitable
   protocols, models or methods exist, they will be preferred over
   creating new ones.

1.1.  Notes

   (1) This issue requires efficient interaction between an upper layer
   in the hierarchy and a lower layer for QoS guarantees and for most
   of the operations on slicing.

2.  Suggested Problems and Work Areas

   The goal of this proposed work is to develop one or more protocol
   specifications (or extensions to existing protocols) to address  specific
   slicing problems that are not met by the existing tools. The following
   problems were selected according to the analysis of the technical gaps in
   IETF protocols ecosystem.

   o Uniform Reference Model for Network Slicing (Architecture document):
   Describes all of the functional elements and instances of a network slice.
   Describes shared non-sliced network parts. Establishes the boundaries to the
   basic network slice operations (creation, management, exposure, consumption).
   Describes the minimum functional and non-functional roles derived from basic
   network slice operations including infrastructure owner (creation, exposure,
   management), slice operator (exposure, management, consumption), slice user
   (management, consumption). Describe the interactions between infrastructure
   owner -- slice operator, slice operator -- slice operator, slice operator --
   slice user. Additionally, this working area will normalize nomenclature and
   definitions for Network Slicing.

   o Review common scenarios from the requirements for operations and
   interactions point of view. Describes the roles (owner, operator, user) which
   are played by entities with single /multiple entities playing different roles.

   o Slice Templates: Design the slices to different scenarios
   ([ChinaCom-2009], [GENI-2009], [IMT2020-2016bis], [NGMN-2016],
   [NGS-3GPP-2016], [ONF-2016]); Outlines an appropriate slice template
   definition that may include capability exposure of managed partitions
   of network resources (i.e. connectivity ([CPP]), compute and storage
   resources), physical and/or virtual network and service functions that can
   act as an independent connectivity network and/or as a network cloud.

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   o Network Slice capabilities (where some prioritization may be
   needed) are expected to be:

       * Four-dimensional efficient slice creation with guarantees for
         isolation in each of the Data /Control /Management /Service
         planes. Enablers for safe, secure and efficient multi-tenancy
         in slices.

       * Methods to enable diverse requirements for NS including
         guarantee for the end-to-end QoS of service in a slice.

       * Efficiency in slicing: specifying policies and methods to realize
         diverse requirements without re-engineering the infrastructure.

       * Recursion: namely methods for NS segmentation allowing a slicing
         hierarchy with parent - child relationships.

       * Customized security mechanisms per slice.

       * Methods and policies to manage the trade-offs between flexibility
         and efficiency in slicing.

       * Optimisation: namely methods for network resources automatic
         selection for NS; global resource view formed; global energy view
         formed; Network Slice deployed based on global resource
         and energy efficiency; Mapping algorithms.

       * Monitoring status and behaviour of NS in a single and/or
         muti-domain environment; NS interconnection.

       * Capability exposure (e.g. openness) for NS; plus APIs for slices.

       * Programmability and control of Network Slices.

   o Network slice operations (again some prioritization may be needed) are
     expected to be:

       * Slice life cycle management including creation,
        activation / deactivation, protection (note 2), elasticity (note 3),
        extensibility (note 4), safety (note 5), sizing and scalability of the
        slicing model per network and per network cloud: slices in access, core
        and transport networks; slices in data centres, slices in edge clouds.

       * Autonomic slice management and operation: namely self-configuration,
        self-composition, self-monitoring, self-optimisation,
        self-elasticity are carried as part of the slice protocols.

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       * Slice stitching / composition: having enablers and methods for
       efficient stitching /composition/ decomposition of slices:
        - vertically (service + management + control planes) and/or
        - horizontally (between different domains part of access,
          core, edge segments) and /or
        - vertically + horizontally.

       * End-to-end network segments and network clouds orchestration
        of slices ([GUERZONI-2016], [KARL-2016]).

       * Service Mapping: having dynamic and Automatic Mapping of Services to
        slices; YANG models for slices.

   o Describe the enablers and methods for the above mentioned capabilities
   and operations from different viewpoints on slices (note 6).

   o Efficient enablers and methods for integration of above capabilities and

2.1.  Notes

   (2) Protection refers to the related mechanisms so that events within
   one slice, such as congestion, do not have a negative impact on
   another slice.

   (3) Elasticity refers to the mechanisms and triggers for the growth
   /shrinkage of network resources, and/or network and service functions.

   (4) Extensibility refers to the ability to expand a NS with
   additional functionality and/or characteristics, or through the
   modification of existing functionality/characteristics, while
   minimizing impact to existing functions.

   (5) Safety refers to the conditions of being protected against
   different types and the consequences of failure, error harm or any
   other event, which could be considered non-desirable.

   (6) Multiple viewpoints on slices: I) viewpoint of the slice's owner
   towards user: from this viewpoint a slice is defined as a means to
   "split" physical or virtual infrastructure elements to "service" smaller
   portions. This action would be recursively done from the owner of the initial and
   physical infrastructure element to the users. II) viewpoint of from the user towards
   the physical infrastructure owner. From this viewpoint a slice is viewed just as a
   set of resources that must be managed (requests to a provider, listed, changed,
   returned to the provider, etc.). This viewpoint emphasizes those issues that would
   be used in the SLA definition of a slice.

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3.  Documents

   The following are the proposed / expected / resulting documents with
   priority (I) or (II) (we note that revised prioritization may be needed):

   o (I) Agreed work plan

   o (I) NS Architecture document
     - Slice template and reference model to IESG (Informational)

   o (I) NS Exposure Interface specification and Data model
     - Slice life-cycle management model and NS Exposure Interface
        specification to IESG (Informational)
     - YANG data model for slicing.

   o (I) Service Requirement to Network Capability Mapping Data Model
     - Requirements for both NS control and management planes.
     - Common use-cases for slice validation for 5G.

   o (I) Four dimensional efficient slice isolation with guarantees for
   isolation in each of the Data/ Control/ Management/ Service planes.

   o (II) Methods to enable diverse requirements for NS including
   guarantee for the end-to-end QoS of a slice.

   o (I) End-to-end coordination and orchestration of slices.

   o (II) Customized security mechanisms per slice.

   o (I) Slice stitching / composition: enablers for efficient stitch /
   composition / decomposition of slices vertically, horizontally and
   vertically + horizontally. This item covers considerations related to
   interconnecting slices that are bond the same administrative domain or
   interconnecting multi-administrative domain.

4.  Security Considerations

   Security will be a major part of the design of network slicing.

5.  IANA Considerations

   This document requests no IANA actions.

6.  Acknowledgements

   Thanks to Sheng Jiang (Huawei Technologies), Hannu Flinck (Nokia),
   Kevin Smith (Vodafone) for reviewing this draft.

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7.  References

7.1.  IETF References

              Dong, J. and S. Bryant, "Problem Statement of Network
              Slicing in IP/MPLS Networks", draft-dong-network-slicing-
              problem-statement-00 (work in progress), October 2016.

              Galis, A., Makhijani, K., and D. Yu, "Autonomic Slice
              Networking-Requirements and Reference Model", draft-galis-
              anima-autonomic-slice-networking-01 (work in progress),
              October 2016.
              Halpern, J., Pignataro, C.,
              "Service Function Chaining (SFC) Architecture",
    , October 2015.

   [I-D.leeking-actn-problem-statement 03]
              Ceccarelli, D., Lee, Y.,
              "Framework for Abstraction and Control of Traffic Engineered
              Networks", draft-leeking-actn-problem-statement-03
              (work in progress), September 2014.

              Lee, Y., Dhody, D., Belotti, S., Pithewan, K., Ceccarelli, D.,
              "Requirements for Abstraction and Control of TE Networks",
              January 2017.

              "Presentations - Network Slicing meeting at IETF 97 of
              15th November 2016", n.d., <

              "Presentations - Network Slicing meeting at IETF 97 of
              15th November 2016", n.d., <

              "Presentations - Network Slicing meeting at IETF 97 of
              15th November 2016", n.d., <

              "Presentations - Network Slicing meeting at IETF 97 of
              15th November 2016", n.d., <

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              "Presentations - Network Slicing meeting at IETF 97 of
              15th November 2016", n.d., <

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
              2006, <>.

   [RFC1958] Carpenter, B., "Architectural Principles of the Internet",
             RFC 1958,

   [RFC3439] Bush, R., Meyer, D., "Some Internet Architectural Guidelines and
             Philosophy",  RFC 3439,

   [RFC3234] Carpenter, B., Brim S., "Middleboxes: Taxonomy and Issues",

   [RFC7149] Boucadair, M., Jacquenet, C.  , " Software-Defined Networking: A
             Perspective from within a Service Provider Environment", RFC 7149,
             March 2014

   [SFG WG]
              "Service Function Chaining WG"
              Boucadair M., Jacquenet, C., Wang, N., "IP Connectivity
              Provisioning Profile (CPP)"

    [IETF-Mobility]Truong-Xuan Do, Young-Han Kim, "Architecture
              for delivering multicast mobility services using network
              slicing" 2016-10-31

    [IETF-Virtualization] Carlos Bernardos, Akbar Rahman, Juan Zuniga, Luis Contreras,
              Pedro Aranda, " Network Virtualization Research Challenges" 2016-10-31

     [IETF-Coding] M.A. Vazquez-Castro, Tan Do-Duy, Paresh Saxena, Magnus Vikstrom,
              "Network Coding Function Virtualization" 2016-11-14

     [IETF-Anchoring] Anthony Chan, Xinpeng Wei, Jong-Hyouk Lee, Seil Jeon,
              Alexandre Petrescu, Fred Templin "Distributed Mobility Anchoring"

7.2.  Informative References

              "A. Galis et al - Management and Service-aware Networking
              Architectures (MANA) for Future Internet - Invited paper
              IEEE 2009 Fourth International Conference on
              Communications and Networking in China (ChinaCom09) 26-28
              August 2009, Xi'an, China", n.d.,

              "GENI Key Concepts - Global Environment for Network
              Innovations (GENI)", n.d.,

              "Guerzoni, R., Vaishnavi, I., Perez-Caparros, D., Galis, A.,
              et al Analysis of End-to-End Multi Domain Management and
              Orchestration Frameworks for Software Defined
              Infrastructures - an Architectural Survey", June 2016,

              "Report on Gap Analysis", ITU-T FG IMT2020, December
              2015, <

              "Draft Technical Report Application of network
              softwarization to IMT-2020 (O-041)", ITU-T FG IMT2020,
              December 2016, <

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              "Draft Terms and definitions for IMT-2020 in ITU-T
              (O-040)", ITU-T FG IMT2020, December 2016,

              "Karl, H., Peuster, M, Galis, A., et al DevOps for Network
              Function Virtualization - An Architectural Approach", July

              "Network Functions Virtualisation (NFV); Management and
              Orchestration v1.1.1.", ETSI European Telecommunications
              Standards Institute., December 2014,

              "Hedmar,P., Mschner, K., et al - Description of Network
              Slicing Concept", NGMN Alliance NGS-3GPP-2016, January
              2016, <

              "Study on Architecture for Next Generation System - latest
              version v1.0.2", September 2016,

              "Paul, M, Schallen, S., Betts, M., Hood, D., Shirazipor,
              M., Lopes, D., Kaippallimalit, J., - Open Network
              Fundation document "Applying SDN Architecture to 5G
              Slicing", Open Network Fundation, April 2016,

Authors' Addresses

   Alex Galis
   University College London


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   Jie Dong
   Huawei Technologies


   Kiran Makhijani
   Huawei Technologies


   Stewart Bryant
   Huawei Technologies


   Mohamed Boucadair


   Pedro Martinez-Julia
   National Institute of Information and Communications Technology (NICT)


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