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NMRG                                                       LM. Contreras
Internet-Draft                                                Telefonica
Intended status: Informational                            P. Demestichas
Expires: January 14, 2021                                          WINGS
                                                             J. Tantsura
                                                            Apstra, Inc.
                                                           July 13, 2020

                         Transport Slice Intent


   Slicing at the transport network is expected to be offered as part of
   end-to-end network slices, fostered by the introduction of new
   services such as 5G.  This document explores the usage of intent
   technologies for requesting transport slices.

Status of This Memo

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   This Internet-Draft will expire on January 14, 2021.

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   the Trust Legal Provisions and are provided without warranty as
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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Transport slice intent  . . . . . . . . . . . . . . . . . . .   3
   3.  Foundation of transport slice intents . . . . . . . . . . . .   3
   4.  Mechanisms for translating transport slice intents  . . . . .   4
     4.1.  Translation approaches and interaction with the upper
           systems . . . . . . . . . . . . . . . . . . . . . . . . .   4
     4.2.  Intent-based system suite . . . . . . . . . . . . . . . .   5
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   5
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   5
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   5
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .   6
   Contributors  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   6

1.  Introduction

   Network slicing is emerging as the future model for service offering
   in telecom operator networks.  Conceptually, network slicing provides
   a customer with an apparent dedicated network built on top of logical
   (i.e. virtual) and/or physical functions and resources supported by a
   shared infrastructure, provided by one or more telecom operators.

   The concept of network slicing has been largely fostered by the
   advent of 5G services that are expected to be deployed on top of
   different kind of slices, each built to support specific
   characteristics (extreme low latency, high bandwidth, etc).

   As part of an end-to-end network slice it is expected to have a
   number of transport network slices providing the necessary
   connectivity to the rest of components of the end-to-end slice, e.g.,
   mobile packet core slice.

   For a definition of a transport slice refer to
   [I-D.nsdt-teas-transport-slice-definition].  The following paragraph
   is directly taken from it: "A transport slice is built based on a
   request from a higher operations system.  The interface to higher
   operations systems should express the needed connectivity in a
   technology-agnostic way, and slice customers do not need to recognize
   concrete configurations based on the technologies (e.g being more
   declarative than imperative).  The request to instantiate a transport
   slice is represented with some indicators such as SLO, and
   technologies are selected and managed accordingly."

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   Intent is a high-level, declarative goal that operates at the level
   of a network and services it provides, not individual devices.  It is
   used to define outcomes and high-level operational goals.

   In consequence, it seems very convenient to apply the intent-based
   mechanisms for the provision of transport network slices, providing
   the adequate level of abstraction towards the transport network
   control and management planes.

   This document leverages current industry trends in the definition of
   end-to-end network slices.  The final objective is to describe
   intents that can be used to flexibly declare the operational aspects
   and goals of a transport network slice, meaning that the customer
   could declare what kind of transport slice is needed (the outcome)
   and not how to achieve the goals of the transport slice.

2.  Transport slice intent

   As stated in [I-D.irtf-nmrg-ibn-concepts-definitions], "Intent is a
   higher-level declarative policy that operates at the level of a
   network and services it provides, not individual devices.  It is used
   to define outcomes and high-level operational goals, without the need
   to enumerate specific events, conditions, and actions".

   When applied to transport networks, this implies that an intent for
   transport slices should provide the necessary abstraction with
   respect to implementation details, including the final devices (or
   resources) involved, and be focused on the characteristics and
   performance expectations related to it.

   With that intent it can be expected that the intent based system can
   fulfill and assure the requested transport network slice, triggering
   initial configurations at the time of initial provisioning and
   corrective actions during the transport slice lifetime.

3.  Foundation of transport slice intents

   The industrial interest around 5G is accelerating network deployments
   and operational changes.

   With this respect, the GSMA has been developing a universal blueprint
   that can be used by any vertical customer to request the deployment
   of a network slice instance (NSI) based on a specific set of service
   requirements.  Such a blueprint is a network slice descriptor called
   Generic Slice Template (GST) [GSMA].  The GST contains multiple
   attributes that can be used to characterize a network slice.  A
   particular template filled with values generates a specific Network
   Slice Type(NEST).

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   Such templates refer to the end-to-end network slice, including the
   transport part.  Despite the fact that some of the values would not
   have applicability for the transport network, others do.  An analysis
   of the relevant attributes is performed in

   According to 3GPP propositions [TS28.541], an upper 3GPP Management
   System interacts with the transport network for establishing the
   necessary slices at the transport level.  Such interaction can be
   expected to happen using the transport slice intent, described to an
   intent-based system (IBS) in the transport network part.  Then,
   according to the intent lifecycle in
   [I-D.irtf-nmrg-ibn-concepts-definitions], the IBS, after recognizing
   the intent, will proceed to translate it in order to interact with a
   transport slice controller by using a NBI as proposed in

4.  Mechanisms for translating transport slice intents

   This section describes approaches for implementing mechanisms to
   translate transport slice intents.

4.1.  Translation approaches and interaction with the upper systems

   A suite of mechanisms will be required to allow instantiation of the
   user's intent into a transport slice.  In order to be able to deliver
   an end2end Intent driven slice - a well defined set of context aware
   attributes that allow unambiguous instantiation of the intent should
   be agreed upon.  A combination of a structured set of
   attributes communicated between an IBN and an upper layer system with
   user input would allow an IBN to have intent modeled and reason about
   its completeness/validity.  Translation approaches and interaction
   with the upper systems might benefit from Natural Language Processing
   (NLP) technics that are needed for enabling high level expression of
   requirements found missing.  The goal would be to identify and
   classify the answers for as many fields as possible from the Generic
   Slice Template (GST), based on the free text / speech provided by the
   user.  As it is highly unlikely that the minimum set of fields to
   properly define a transport slice (geo-temporal characteristics,
   performance characteristics, SLO and SLA properties) will be
   fulfilled in this first step, a follow up two-step approach might
   need to be implemented.

   o  The minimum missing fields from the GST have to be identified and
      appropriate questions have to be generated (e.g. based on a pool
      of available questions correlated with each field, or based on AI

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   o  An iterative interrogation phase will be initiated towards the
      user using the previously generated questions, until the user
      provides all the missing information, so the intent can be modeled

   Interaction with the user and higher-up systems can potentially be
   further improved by utilizing Machine Learning techniques.

4.2.  Intent-based system suite

   In order to consolidate on the set of devices, technologies and
   resources to be used, a combination of deterministic or stochastic
   computation approaches will be needed.  Deterministic approaches will
   rely on mathematical models and respective algorithms.  Stochastic
   approaches will rely on technologies like machine learning.  Their
   goal will be to learn from experience, so as to optimize future
   decisions from the viewpoint of speed and reliability.  The target of
   learning will be related to the service behavior and to the
   anticipated network status in the area and time period of the service

5.  Security Considerations

   To be done.

6.  IANA Considerations

   This draft does not include any IANA considerations

7.  References

   [GSMA]     "Generic Network Slice Template, version 3.0", NG.116 ,
              May 2020.

              Contreras, L., Homma, S., and J. Ordonez-Lucena,
              "Considerations for defining a Transport Slice NBI",
              draft-contreras-teas-slice-nbi-01 (work in progress),
              March 2020.

              Clemm, A., Ciavaglia, L., Granville, L., and J. Tantsura,
              "Intent-Based Networking - Concepts and Definitions",
              draft-irtf-nmrg-ibn-concepts-definitions-01 (work in
              progress), March 2020.

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              Rokui, R., Homma, S., Makhijani, K., Contreras, L., and J.
              Tantsura, "IETF Definition of Transport Slice", draft-
              nsdt-teas-transport-slice-definition-03 (work in
              progress), July 2020.

              "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.


   This work has been partly funded by the European Commission through
   the H2020 project 5G-EVE (Grant Agreement no. 815074).


   Kostas Tsagkaris, Kostas Trichias, Vassilis Foteinos, and Thanasis
   Gkiolias (all from WINGS ICT Solutions) have also contributed to this

Authors' Addresses

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

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

   Panagiotis Demestichas
   WINGS ICT Solutions

   Email: pdemest@wings-ict-solutions.eu

   Jeff Tantsura
   Apstra, Inc.

   Email: jefftant.ietf@gmail.com

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