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
draft-contreras-nmrg-transport-slice-intent-01
Abstract
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.
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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
[I-D.contreras-teas-slice-nbi].
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
[I-D.contreras-teas-slice-nbi].
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
approaches).
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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
accordingly.
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
provision.
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.
[I-D.contreras-teas-slice-nbi]
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.
[I-D.irtf-nmrg-ibn-concepts-definitions]
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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[I-D.nsdt-teas-transport-slice-definition]
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.
[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.
Acknowledgments
This work has been partly funded by the European Commission through
the H2020 project 5G-EVE (Grant Agreement no. 815074).
Contributors
Kostas Tsagkaris, Kostas Trichias, Vassilis Foteinos, and Thanasis
Gkiolias (all from WINGS ICT Solutions) have also contributed to this
work.
Authors' Addresses
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/
Panagiotis Demestichas
WINGS ICT Solutions
Greece
Email: pdemest@wings-ict-solutions.eu
Jeff Tantsura
Apstra, Inc.
Email: jefftant.ietf@gmail.com
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