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Network Slicing Architecture

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This is an older version of an Internet-Draft whose latest revision state is "Expired".
Authors Liang Geng , Stewart Bryant , Jie Dong
Last updated 2017-03-13
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Network Working Group                                            L. Geng
Internet-Draft                                              China Mobile
Intended status: Informational                                 S. Bryant
Expires: September 14, 2017                                      J. Dong
                                                     Huawei Technologies
                                                          March 13, 2017

                      Network Slicing Architecture


   This document defines the overall architecture of network slicing.
   Base on the general architecture, basic concepts of network slicing
   and examples of network slicing instances are introduced for
   clarification purposes.  Some architectural considerations about the
   data plane, control plane, management and orchestration of network
   slicing are described to give a general view of network slicing
   implementation principles.  This also helps to identify the gaps in
   existing IETF works relating to network slicing.

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

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Demand for Network Slicing  . . . . . . . . . . . . . . . . .   3
     2.1.  Guaranteed Service Performance  . . . . . . . . . . . . .   4
     2.2.  End-to-end Customization  . . . . . . . . . . . . . . . .   4
     2.3.  Network Slicing as a Service  . . . . . . . . . . . . . .   4
   3.  Network Slicing Architecture  . . . . . . . . . . . . . . . .   5
     3.1.  Basic Concepts  . . . . . . . . . . . . . . . . . . . . .   5
       3.1.1.  Network Slicing Service Provider  . . . . . . . . . .   5
       3.1.2.  Network Slice Instance  . . . . . . . . . . . . . . .   5
       3.1.3.  Network Slice Type  . . . . . . . . . . . . . . . . .   6
       3.1.4.  Network Slice Template  . . . . . . . . . . . . . . .   6
       3.1.5.  Network Slice Tenant  . . . . . . . . . . . . . . . .   6
     3.2.  General Architecture  . . . . . . . . . . . . . . . . . .   6
   4.  Data Plane of Network Slicing . . . . . . . . . . . . . . . .   8
     4.1.  Propagation of Guarantees . . . . . . . . . . . . . . . .   8
     4.2.  The Underlying Physical Layer . . . . . . . . . . . . . .   8
     4.3.  Hard vs Soft Slicing in the Data-plane  . . . . . . . . .   9
     4.4.  The Role of Deterministic Networking  . . . . . . . . . .   9
     4.5.  The Role of VPNs  . . . . . . . . . . . . . . . . . . . .  10
     4.6.  Dynamic Reprovisioning  . . . . . . . . . . . . . . . . .  10
     4.7.  Non-IP Data Plane . . . . . . . . . . . . . . . . . . . .  10
   5.  Control Plane of Network Slicing  . . . . . . . . . . . . . .  10
   6.  Management and Orchestration of Network Slicing . . . . . . .  11
   7.  Service Functions . . . . . . . . . . . . . . . . . . . . . .  11
   8.  OAM and Telemetry . . . . . . . . . . . . . . . . . . . . . .  11
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  12
   10. Security Considerations . . . . . . . . . . . . . . . . . . .  12
   11. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   12. Normative References  . . . . . . . . . . . . . . . . . . . .  12
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   The Internet has always been designed to support a variety of
   services.  The emerging 5G market is expected to bring this diversity
   of services to a new level.  Typical examples of new bandwidth-hungry
   services enabled by 5G include high definition (HD) video, virtual
   reality (VR) and augmented reality (AR).  The high bandwidth
   requirement of these services is not particularly challenging thanks
   to the continuing advancing technologies.  However, the guarantee of

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   high bandwidth performance of these services based-on a spontaneous
   on-demand pattern is fairly challenging.  Moreover, providing high
   bandwidth with strict packet loss tolerances and high mobility is
   also difficult for the current networks which are commonly designed
   for best effort purposes.

   Given that most Internet protocols are designed to comply with a best
   effort, or enhanced best effort paradigm, it is inevitable that the
   network will suffer from performance degradation in case of
   congestion.  Recent work on deterministic networking (DetNet) aim to
   improve this situation by providing a ceiling on latency for a
   particular traffic flow, which significant improves packet error rate
   for specific DetNet services.  This pioneering work gives a great
   example that new approaches are investigated to make the Internet
   aware of certain performance requirement other than the bandwidth.

   Taking a look at the network infrastructure, service provider used to
   build dedicated network and resources for services requiring
   guaranteed performance.  This is simply not cost-effective, neither
   is it flexible.  The emergence of virtualization and VPN technologies
   make it possible to set up logically isolated computing and network
   instances from shared infrastructures.  This can be used dedicatedly
   by specific services for improved performances.  However, many
   questions are still to be answered as different technologies in
   various domains need to be combined to build network slices, which
   may require the separation of different resources and various types
   of performance guarantees.

2.  Demand for Network Slicing

   It is expected that a diversity of new services will emerge in 5G
   network.  These services including smart home, industrial control,
   remote healthcare, Vehicle-to-Everything (V2X) and etc. will
   eventually create an ecosystem of "Internet of Everything".  With
   hundreds of billions of devices from different business sectors
   connected, the future network needs to meet the diversified Quality
   of Experience (QoE) demands of different vertical industries.
   Typical QoE requirements for the end users or the applications are
   extremely low latency and high reliability, whilst the purchaser of
   the slice is looking for short time-to-market and rapid deployment of
   the service infrastructure needed to provide the technical
   underpinning of their business.  Service providers' networks need to
   continuously evolve to adapt to this change.  As a result, it is
   believed that future networks should be able to provide services with
   guaranteed performances together with the existing best-effort
   services.  In order to achieve this, it is preferred that dedicated
   resources in the network could be used by different vertical industry

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   customers.  Network slicing is proposed as an end-to-end solution for
   this purpose.

2.1.  Guaranteed Service Performance

   One of the most challenging requirements for future network is to
   provide guaranteed performance for varieties of new services whilst
   maintaining the economies of scale that accrue through resource
   sharing.  It has been foreseen that the requirements of different
   services would be diversified and complex.

   Taking augmented reality (AR) service as an example, it requires high
   bandwidth to provide a local video feed to the augmenter, and high
   quality augmented video back to the user.  At the same time, it also
   requires extremely low latency since the created reality and the
   user's view must be synchronized to avoid reaction mismatch.  Another
   example is the vehicular communications where the delay in traffic
   control system may directly jeopardize the road safety.

   Network slicing can deal with these challenges by mapping the
   performance requirements to physically or logically dedicated

2.2.  End-to-end Customization

   Customization is another significant feature of future services.
   Many vertical industries are expected to offer customization
   capabilities as a service to both internal manufacturing processes
   and specific end users.  Meanwhile, these customized services need to
   be deployed with short time-to-market.  The network needs to adapt to
   this challenge since customers may frequently adjust and refine their
   customization requirements.

   There is ongoing work such as network orchestration, software defined
   networks and network function virtualization that aims to address
   this problem.  In principle, these new technologies share a common
   request for the network to provide the ability to provide agile
   resource allocation.

2.3.  Network Slicing as a Service

   It is anticipated that the operation of 5G and future networks will
   involve new business models.  Given that the network is more
   flexible, elastic, modularized and customized, the shared network
   infrastructure can be sliced and offered as a service to the
   customer.  For instance, dedicated, isolated, end-to-end network
   resources with a customized topology can be provided as a network
   slice service to the tenant of this network slice.The tenants are

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   allowed to have a certain level of provisioning of their network

3.  Network Slicing Architecture

   This section introduces the general system architecture of network

3.1.  Basic Concepts

   Network slicing is a collection of technologies that are used to
   establish logically dedicated resources including but not limited to
   connectivity, computing, storage, provisioning and specific network
   functions.  The logical resources are a part of the larger common
   network infrastructures that are shared among various network slice
   instances.  These dedicated resources can be customized to meet the
   diversified requirements of different vertical industries.

   The following sections describe some basic concepts of network

3.1.1.  Network Slicing Service Provider

   A network slicing service provider, typically a telecommunication
   service provider, is the owner of the network infrastructures from
   which network slices are created.  The network slicing service
   provider takes the responsibilities of managing and orchestrating
   corresponding resources that network slicing uses.

3.1.2.  Network Slice Instance

   A network slice instance (NSI) is the end-to-end realization of
   network slicing, which consists of the combination of physically or
   logically dedicated resources.  An NSI typically associates with
   components from different network domains including core network,
   transport network and access network.  It may also require cloud
   resources from data centres.  Furthermore, end-user terminals may
   also allocate dedicated resource to a specific NSI.

   Each NSI is defined and created for specific service-oriented
   requirements.  The logically dedicated resources allocated to NSIs
   may be intrinsically isolated physical instances.  They may also
   share common physical infrastructures according to implementation

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3.1.3.  Network Slice Type

   Network slices are categorized into different types according to the
   abstraction of characteristics of the services they facilitate.  The
   methodology used for defining network slice types may be different
   for the owners of network slicing infrastructure.  Some typical
   examples of network slice types according to 5G implementation
   include eMMB, mMTC and URLLC.  Network slice type may be used to map
   specific network resources, VPNs, QoS categories according to real
   implementation.  It is advised that mutual types should be defined
   according to existing main-stream service implementation scenarios.
   Extensions should be allowed for network slicing service provider to
   make according to new requirements.

3.1.4.  Network Slice Template

   A network slice template is an abstraction of the resource
   requirement for a set of similar network slice instances.  Different
   templates are defined for individual network slice types.  These
   templates are used to create certain network slice instances.

3.1.5.  Network Slice Tenant

   A network slice tenant is the user of specific NSIs, with which
   specific services can be provided to end customers.  Network slice
   tenants can make requests of the creation of new network slice
   instances.  Certain level of management capability should be exposed
   to network slice tenant from network slice service provider.

3.2.  General Architecture

   Figure 1 illustrates the general architecture of network slicing.  It
   can be seen that two network slice instances are created from the
   shared network infrastructures.  In principle, the network elements
   (NEs) represent any general network infrastructures for demonstration
   purposes.  The two instances created do not know the existence of
   each other.  However, they may share the computing, connectivity and
   storage resources of the NE, whether they are in physical or virtual
   forms.  Meanwhile, the owner of a particular network slice instance
   is allowed to adjust the instance by requesting changes via the
   network slicing management and orchestration system.

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       |         Network Slice Management and Orchestration        |
       |   +------------+ +-------------+ +--------------------+   |
       |   |  Template  | |   E2E Slice | |   Life cycle Mngt. |   |
       |   | Management | |Orchestration| |   and monitoring   |   |
       |   +------------+ +-------------+ +--------------------+   |
       |              Created Network Slice Instances              |
       | +-------------------------------------------------------+ |
       | |                                                       | |
       | |  +---+          +---+            +---+                | |
       | |  |NE1+----+     |NE3|            |NE5|                | |
       | |  +---+    |     +-+-+            +-+-+                | |
       | |         +-+-+     |                |                  | |
       | |         |NE2+-----+                |                  | |
       | |         +-+-+                      |  Network Slice   | |
       | |           |                        |   Instance 1     | |
       | |           +------------------------+                  | |
       | +-------------------------------------------------------+ |
       | +-------------------------------------------------------+ |
       | |                                                       | |
       | |  +---+                           +---+      +---+     | |
       | |  |NE1+----+                   +--+NE5+------+NE6|     | |
       | |  +---+    |                   |  +-+-+      +---+     | |
       | |         +-+-+           +---+ |    |                  | |
       | |         |NE2|           |NE4+-+    |                  | |
       | |         +-+-+           +-+-+      |  Network Slice   | |
       | |           |               |        |   Instance 2     | |
       | |           +------------------------+                  | |
       | +-------------------------------------------------------+ |

       |             Physical Network Infrastructures              |
       |    +---+         +---+             +---+      +---+       |
       |    |NE1+----+    |NE3+------+   +--+NE5+------+NE6|       |
       |    +---+    |    +-+-+      |   |  +-+-+      +---+       |
       |           +-+-+    |      +-+-+ |    |                    |
       |           |NE2+----+      |NE4+-+    |                    |
       |           +-+-+           +-+-+      |                    |
       |             |               |        |                    |
       |             +------------------------+                    |
                  Figure 1. Network Slicing Architecture

   It is fundamental to network slicing that slices may be created, the
   topology and/or its resources modified, and that the slices may be
   decommissioned in a timely manner with minimum work by the network
   slicing provider or the customer.  This is not however unique to

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   network slicing, it is a goal of modern classical networks to be able
   to do this.

4.  Data Plane of Network Slicing

   In the network slicing architecture, the data plane in the edge and
   core of the network will likely be one or more of the standard IETF
   data planes: IPv4/IPv6, MPLS or Pseudowires (PW).  This section
   assumes that the IETF protocol stack exists as-is, and describes the
   performance consideration in different layers of the data plane.

4.1.  Propagation of Guarantees

   Guarantees of delay start at the physical layer and propagate up the
   stack layer by layer.  Any layer can add delay, and can take various
   steps to minimize the impact of delay on its layer, but no layer can
   reduce the delay introduced by a lower layer.

   Guarantees of loss and jitter can, by contrast be upheld or improved
   at any layer of the protocol stack, but usually at a cost of
   increased delay.  Where delay is a constrain as it is in some 5G
   applications the option of trading delay for better loss or jitter
   characteristics is not an option.  In these circumstances it is
   critical that the quality characteristics start at the physical layer
   and be maintained at each layer of the protocol stack.

4.2.  The Underlying Physical Layer

   A point to point dedicated physical channel provides the delay,
   jitter and loss characteristics limited only by the media itself.
   This does not fulfil the need for rapid reconfiguration of the
   network to provision new services.

   To address the need to provision a slice of the data-plane one
   approach that can be deployed is to time-slice access to the physical
   service.  Ignoring many of the classic TDM offering as being too
   slow, a number of technologies are available that might be applied
   including OTN and FlexE.  Whilst the provisioning of the channel
   provided by underlays such as FlexE and the interconnection of FlexE
   channels is within the scope of this architecture the operation of
   the underlay is outside its scope.

   The logical sub-division of a physical channel be that a single
   channel with the full bandwidth available or a channel multiplexed at
   the physical layer such as is provided by FlexE we will consider in
   the following section.

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4.3.  Hard vs Soft Slicing in the Data-plane

   Hard slicing refers to the provision of resources in such a way that
   they are dedicated to a specific NSI.  Data-plane resources are
   provided in the data-plane through the allocation of a lambda,
   through the allocation of a time domain multiplexed resource such as
   a FlexE channel or through a service such as an MPLS hard-pipe.  Note
   that although hard-pipes can be used to allocate dedicated, non-
   shared resources to an NSI, the using of allocation is bandwidth,
   which can result in more "lumpiness" in the physical channel that
   would not be present with a true physical layer multiplexing scheme.

   Soft slicing refers to the provision of resources in such a way that
   whilst the slices are separated such that they cannot statically
   interfere with each other (one cannot receive the others packets or
   observe or interfere with the other's storage), they can interact
   dynamically (one may find the other is sending a packet just when it
   wants to, or the other may be using CPU cycles just when the other
   needs to process some information), which means they may compete for
   some particular resource at some specific time.  Soft slicing is
   achieved through logically multiplexing the data-plane over a
   physical channel include various types of tunnel (IP or MPLS) or
   various types of pseudowire (again IP or MPLS).  Although the design
   of deterministic networking techniques helps, it is not possible to
   achieve the same degree of isolation with these techniques as it is
   possible to achieve with pure physical layer multiplexing techniques.
   However where such techniques provide sufficient isolation their use
   leads to a network design that may be deployed on existing equipment
   designs and which can make unused bandwidth available to best effort

4.4.  The Role of Deterministic Networking

   Deterministic networking is a technology under development in the
   IETF that aims to both minimize congestion loss and set an upper
   bound on per hop latency.  It allows a packet layer to emulate the
   behaviour of a fully partitioned underlay such might be provided
   through some physical layer multiplexing system such as FlexE.

   Deterministic networking works by policing the ingress rate of a flow
   to an agreed maximum and then scheduling the transmission time of
   each flow to reduce the "lumpiness" and hence the possible buildup of
   queues and hence congestion loss.

   Whilst deterministic networking is not as perfect as physical layer
   multiplexing in terms of latency minimization, because the scheduling
   is hop by hop and not end to end meaning that at each hop a packet
   has to wait for the transmission slot allocated to its flow, it has

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   the advantage that it is able to allocate slots not needed by the
   allocated traffic to best effort traffic.  This reallocation of the
   unused transmission slots to background traffic significantly
   improves the efficiency of the network by amortizing the cost between
   the scheduled high priority users and the best effort users.

4.5.  The Role of VPNs

   VPNs are considered candidate technologies for network slicing.  The
   existing VPN technologies mainly focus on the isolation of forwarding
   tables between different tenants and provide a virtual topology for
   the connectivity between different sites of a tenant.  The VPN layer
   and the underlying network resources are usually loosely coupled, and
   statistical multiplexing is adopted to improve network utilization.

   Although VPNs have been widely used to provide enterprise services in
   service provide networks, it is unclear that whether VPNs along with
   existing underlying tunnel technologies can meet the performance and
   isolation requirements of critical services in the vertical

4.6.  Dynamic Reprovisioning

   A requirement of the network slicing system is that it can be
   dynamically and non-disruptively reprovisioned.  That is not an
   unusual requirement of a modern network.  However the frequency of
   reprovisioning with network slicing will be relatively high, such
   that it in many cases it is not possible to hide any disruption
   during a "quiet" time.

   Physical multiplexing methods such as FlexE have the ability to
   seamlessly reprovision multiplex slots.  At the network layer
   techniques such as make-before-break, segment routing, and loop-free-
   convergence can be used to provide uninterrupted operation during a
   topology change.

4.7.  Non-IP Data Plane

   Non-IP data plane in support of Information Centric Networking (ICN),
   some of the IoT services and other similar requirements will be added
   in a future version.

5.  Control Plane of Network Slicing

   There are two control plane systems that need to be considered.  The
   first is the control plane of the slicing infrastructure itself, the
   second is the control plane of an individual slice.

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   The network slicing control plane receives instructions from the
   orchestration layer and creates the required network slices and
   manages them throughout their life cycle.  The slices need to satisfy
   a diverse set requirements and need to be dynamically managed as the
   collective requirements of the set of network slices changes, and as
   the resource and capabilities of the physical network change with
   time.  Changes occur as resources fail, and resources are added.
   They also occur as the slices are added and deleted possibly needing
   a garbage collection and defagmantation service.

   The control plane of the network slicing system needs to comply with
   the SDN architecture, while still using distributed control protocols
   when it is necessary or proved to have advantages.

   Within a slice the full range of existing control plane technologies
   needs to be permissible.  Some slices will run the existing IGP
   protocols (such as IS-IS or OSPF) whilst others may use BGP.  Some
   slices may be controlled by their own SDN controllers.  However the
   architecture needs to be sufficiently general so as not to restrict
   the control protocols that may be used within a slice.

6.  Management and Orchestration of Network Slicing

   The management and orchestration layer of network slicing system is
   responsible for the slice template management, slice orchestration
   and life cycle management and monitoring of network slices.  Network
   slice templates can be generated according to the functional and
   performance requirements of the tenants.  In different network
   domains, different technologies may be used for network slicing, and
   orchestration is needed to build E2E network slice.  The
   provisioning, runtime assurance and decommissioning of E2E network
   slices is also the key function of this layer.

   It is expected that the management and orchestration layer would use
   state of the art management technologies to support short time-to-
   market, and help the operators to build an open ecosystem for new
   services in vertical industries.

7.  Service Functions

   To be provided in a future version.

8.  OAM and Telemetry

   To be provided in a future version.

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9.  IANA Considerations

   This document makes no request of IANA.

10.  Security Considerations

   Each layer of the system has its own security requirements.

11.  Acknowledgements

12.  Normative References

              China Mobile Communication Corporation, Huawei
              Technologies Co. Deutsche Telekom AG,Volkswagen, "5G
              Service-Guaranteed Network Slicing White Paper", 2017,

              Nakao, A., Shimizu, T., and T. Kinoshita, "High level
              technical characteristics of network softwarization for
              IMT-2020", 2017.

              Goto, Y. and N. Morita, "Draft supplement to Y.IMT2020
              series "Standardization and open source activities related
              to network softwarization of IMT-2020"", 2017.

Authors' Addresses

   Liang Geng
   China Mobile


   Stewart Bryant
   Huawei Technologies


   Jie Dong
   Huawei Technologies


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