Considerations for defining a Transport Slice NBI
draft-contreras-teas-slice-nbi-00

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TEAS Working Group                                         LM. Contreras
Internet-Draft                                                Telefonica
Intended status: Informational                                  S. Homma
Expires: May 7, 2020                                                 NTT
                                                       J. Ordonez-Lucena
                                                              Telefonica
                                                        November 4, 2019

           Considerations for defining a Transport Slice NBI
                   draft-contreras-teas-slice-nbi-00

Abstract

   The transport network is an essential component in the end-to-end
   delivery of services and, consequently, with the advent of network
   slicing it is necessary to understand what could be the way in which
   the transport network is consumed as a slice.  This document analyses
   the needs of potential transport slice consumers in order to identify
   the functionality required on the North Bound Interface (NBI) of a
   transport slice producer for satisfying such transport slcie
   requests.

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   publication of this document.  Please review these documents
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Conventions used in this document . . . . . . . . . . . . . .   3
   3.  Northbound interface for transport slices . . . . . . . . . .   3
   4.  Transport slice use cases . . . . . . . . . . . . . . . . . .   4
     4.1.  5G Services . . . . . . . . . . . . . . . . . . . . . . .   4
       4.1.1.  Generic Slice Template  . . . . . . . . . . . . . . .   5
       4.1.2.  Categorization of GST attributes  . . . . . . . . . .   6
         4.1.2.1.  Attributes with direct impact on the transport
                   slice definition  . . . . . . . . . . . . . . . .   7
         4.1.2.2.  Attributes with indirect impact on the transport
                   slice definition  . . . . . . . . . . . . . . . .   7
         4.1.2.3.  Attributes with no impact on the transport slice
                   definition  . . . . . . . . . . . . . . . . . . .   8
     4.2.  NFV-based services  . . . . . . . . . . . . . . . . . . .   8
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   9
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   9
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

1.  Introduction

   A number of new technologies, such as 5G, NFV and SDN are not only
   evolving the network from a pure technological perspective but also
   are changing the concept in which new services are offered to the
   customers [I-D.homma-slice-provision-models] by introducing the
   concept of network slicing.

   The transport network is an essential component in the end-to-end
   delivery of services and, consequently, it is necessary to understand
   what could be the way in which the transport network is consumed as a
   slice.

   In this document it is assumed that there exists a (logically)
   centralized component in the transport network, namely Transport
   Slice Producer (TSP) with the responsibilities on the control and
   management of the transport slices invoked for a given service, as
   requested by Transport Slice Consumers (TSC).

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   This document analyses the needs of potential transport slice
   consumers in order to identify the functionality required on the
   North Bound Interface (NBI) of the TSP to be exposed towards such
   transport slice consumers.  Solutions to construct the requested
   transport slices are out of scope of this document.

   This document addresses some of the discussions of the TEAS Slice
   Design Team.  However it is not at this stage an official outcome of
   the Design Team.

2.  Conventions used in this document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC2119 [RFC2119].

3.  Northbound interface for transport slices

   In a general manner, the transport network supports different kinds
   of services.  These services consume the transport network provided
   capabilities for deploying end-to-end services, interconnecting
   network functions or applications spread across the network and
   providing connectivity toward the final users of these services.

   Under the slicing approach, a transport slice consumer requests to a
   transport slice producer a slice with certain characteristics and
   parametrization.  Such request it is assumed here to be done through
   an NBI exposed by the TSP to the consumer, as reflected in Fig. 1.

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                               +--------------------+
                               |                    |
                               |      Transport     |
                               |   Slice Consumer   |
                               |                    |
                               +--------------------+
                                          A
                                          |
                                          | Transport
                                          | Slice
                                          | NBI
                                          |
                                          V
                               +--------------------+
                               |                    |
                               |      Transport     |
                               |   Slice Producer   |
                               | (Transport Slicer) |
                               |                    |
                               +--------------------+

                   Figure 1: Transport slice NBI concept

   The functionality supported by the NBI depends on the requirements
   that the slice consumer has to satisfy.  It is then important to
   understand the needs of the slice consumers as well as the way of
   expressing them.

4.  Transport slice use cases

   Different use cases for slice consumers can be identified, as
   described in the following sections.

4.1.  5G Services

   5G services natively rely on the concept of network slicing. 5G is
   expected to allow vertical customers to request slices in such a
   manner that the allocated resources and capabilities in the network
   appear as dedicated for them.

   In network slicing scenarios, a vertical customer requests a network
   operator to allocate a network slice instance (NSI) satisfying a
   particular set of service requirements.  The content/format of these
   requirements are highly dependent on the networking expertise and use
   cases of the customer under consideration.  To deal with this
   heterogeneity, it is fundamental for the network operator to define a
   a unified ability to interpret service requirements from different

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   vertical customers, and to represent them in a common language, with
   the purposes of facilitating their translation/mapping into specific
   slicing-aware network configuration actions.  In this regard, model-
   based network slice descriptors built on the principles of
   reproducibility, reusability and customizability can be defined for
   this end.

   As a starting point for such a definition, GSMA developed the idea of
   having a universal blueprint that can be used by any vertical
   customer to order the deployment of an NSI based on a specific set of
   service requirements.  The result of this work has been the
   definition of a baseline network slice descriptor called Generic
   Slice Template (GST).  The GST contains multiple attributes that can
   be used to characterize a network slice.  A Network Slice Type (NEST)
   describes the characteristics of a network slice by means of filling
   GST attributes with values based on specific service requirements.
   Basically, a NEST is a filled-in version of a GST.  Different NESTs
   allow describing different types of network slices.  For slices based
   on standardized service types, e.g. eMBB, uRLLC and mIoT, the network
   operator may have a set of readymade, standardized NESTs (S-NESTs).
   For slices based on specific industry use cases, the network operator
   can define additional NESTs.

   Service requirements from a given vertical customer are mapped to a
   NEST, which provides a self-contained description of the network
   slice to be provisioned for that vertical customer.  According to
   this reasoning, the NEST can be used by the network operator as input
   to the NSI preparation phase, which is defined in [TS28.530]. 3GPP is
   working on the translation of the GST/NEST attributes into NSI
   related requirements, which are defined in the "ServiceProfile" data
   type from the Network Slice Information Object Class (IOC) in
   [TS28.541].  These requirements are used by the 3GPP Management
   System to allocate the NSI across all network domains, including
   transport network.  The transport slice defines the part of that NSI
   that is deployed across the transport network.

   Despite the translation is an on-going work in 3GPP it seems
   convenient to start looking at the GST attributes to understand what
   kind of parameters could be required for the transport slice NBI.

4.1.1.  Generic Slice Template

   The structure of the GST is defined in [GSMA].  The template defines
   a total of 35 attributes.  For each of them, the following
   information is provided:

   o  Attribute definition, which provides a formal definition of what
      the attribute represents.

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   o  Attribute parameters, including:

      *  Value, e.g. integer, float.

      *  Measurement unit, e.g. milliseconds, Gbps

      *  Example, which provides examples of values the parameter can
         take in different use cases.

      *  Tag, which allow describing the type of parameter, according to
         its semantics.  An attribute can be tagged as a
         characterization attribute or a scalability attribute.  If it
         is characterization attribute, it can be further tagged as a
         performance-related attribute, a functionality-related
         attribute or an operation-related attribute.

      *  Exposure, which allow describing how this attribute interact
         with the slice consumer, either as an API or a KPI.

   o  Attribute presence, either mandatory, conditional or optional.

   Attributes from GST can be used by the network operator (slice
   producer) and a vertical customer (slice consumer) to agree SLA.

   GST attributes are generic in the sense that they can be used to
   characterize different types of network slices.  Once those
   attributes become filled with specific values, it becomes a NEST
   which can be ordered by slice consumers.

4.1.2.  Categorization of GST attributes

   Not all the GST attributes as defined in [GSMA] have impact in the
   transport network since some of them are specific to either the radio
   or the mobile core part.

   In the analysis performed in this document, the attributes have been
   categorized as:

   o  Attributes that directly impact the definition of the transport
      slice, i.e., attributes that can be directly translated into
      requirements required to be satisfied by a transport slice.

   o  Attributes that indirectly impact the definition of the transport
      slice, i.e., attributes that indirectly impose some requirements
      to a transport slice.

   o  Attributes that do not have impact on the transport slice.

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   The following sections describe the attributes falling into the three
   categories.

4.1.2.1.  Attributes with direct impact on the transport slice
          definition

   The following attributes impose requirements in the transport slice

   o  Availability

   o  Deterministic communication

   o  Downlink throughput per network slice

   o  Energy efficiency

   o  Group communication support

   o  Isolation level

   o  Maximum supported packet size

   o  Mission critical support

   o  Performance monitoring

   o  Reliability

   o  Slice quality of service parameters

   o  Support for non-IP traffic

   o  Uplink throughput per network slice

   o  User data access (i.e., tunneling mechanisms)

4.1.2.2.  Attributes with indirect impact on the transport slice
          definition

   The following attributes indirectly impose requirements in the
   transport slice to support the end-to-end service.

   o  Coverage

   o  Delay tolerance (i.e., if the service can be delivered when the
      system has sufficient resources)

   o  Downlink throughput per UE

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   o  Network Slice Customer network functions

   o  Number of connections

   o  Performance prediction (i.e., capability to predict the network
      and service status)

   o  Root cause investigation

   o  Session and Service Continuity support

   o  Simultaneous use of the network slice

   o  Supported device velocity

   o  Terminal density

   o  Uplink throughput per UE

   o  User management openness (i.e., capability to manage users'
      network services and corresponding requirements)

4.1.2.3.  Attributes with no impact on the transport slice definition

   The following attributes do not impact the transport slice.

   o  Location based message delivery (not related to the geographical
      spread of the network slice itself but with the localized
      distribution of information)

   o  MMTel support, i.e. support of and Multimedia Telephony Service
      (MMTel)as well as IP Multimedia Subsystem (IMS) support.

   o  Number of terminals

   o  Positioning support

   o  Radio spectrum

   o  Synchronicity (among devices)

   o  V2X communication mode

4.2.  NFV-based services

   To do.

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5.  Security Considerations

   This draft does not include any security considerations.

6.  IANA Considerations

   This draft does not include any IANA considerations

7.  References

7.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

7.2.  Informative References

   [GSMA]     "Generic Network Slice Template, version 1.0", NG.116 ,
              May 2019.

   [I-D.homma-slice-provision-models]
              Homma, S., Nishihara, H., Miyasaka, T., Galis, A., OV, V.,
              Lopez, D., Contreras, L., Ordonez-Lucena, J., Martinez-
              Julia, P., Qiang, L., Rokui, R., Ciavaglia, L., and X.
              Foy, "Network Slice Provision Models", draft-homma-slice-
              provision-models-01 (work in progress), July 2019.

   [TS28.530]
              "TS 28.530 Management and orchestration; Concepts, use
              cases and requirements (Release 16) V16.0.0.", 3GPP TS
              28.530 V16.0.0 , September 2019.

   [TS28.541]
              "TS 28.541 Management and orchestration; 5G Network
              Resource Model (NRM); Stage 2 and stage 3 (Release 16)
              V16.2.0.", 3GPP TS 28.541 V16.2.0 , September 2019.

Authors' Addresses

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   Luis M. Contreras
   Telefonica
   Ronda de la Comunicacion, s/n
   Sur-3 building, 3rd floor
   Madrid  28050
   Spain

   Email: luismiguel.contrerasmurillo@telefonica.com
   URI:   http://lmcontreras.com/

   Shunsuke Homma
   NTT
   Japan

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

   Jose A. Ordonez-Lucena
   Telefonica
   Ronda de la Comunicacion, s/n
   Sur-3 building, 3rd floor
   Madrid  28050
   Spain

   Email: joseantonio.ordonezlucena@telefonica.com

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