NMRG LM. Contreras
Internet-Draft Telefonica
Intended status: Informational P. Demestichas
Expires: July 15, 2022 WINGS
J. Tantsura
Microsoft
January 11, 2022
IETF Network Slice Intent
draft-contreras-nmrg-transport-slice-intent-05
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 IETF network slices.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. IETF network slice intent . . . . . . . . . . . . . . . . . . 3
3. Foundation of IETF network slice intents . . . . . . . . . . 4
4. Mechanisms for translating IETF network slice intents . . . . 5
4.1. Translation approaches and interaction with the upper
systems . . . . . . . . . . . . . . . . . . . . . . . . . 5
4.2. Intent-based system suite . . . . . . . . . . . . . . . . 6
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 7
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
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 network slices at transport level (referred as IETF 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 an IETF network slice refer to
[I-D.ietf-teas-ietf-network-slices]. The following paragraph is
directly taken from it: "An IETF Network Slice Service enables
connectivity between a set of CEs with specific Service Level
Objectives (SLOs) and Service Level Expectations (SLEs) over a common
underlay network."
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.
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In consequence, it seems very convenient to apply the intent-based
mechanisms for the provision of IETF 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 an IETF network slice, meaning that the customer could
declare what kind of IETF network slice is needed (the outcome) and
not how to achieve the goals of the IETF network slice.
2. IETF network slice intent
As stated in [I-D.irtf-nmrg-ibn-concepts-definitions], "Intent is a
declaration of operational goals that a network is supposed to meet
and outcomes that the network is supposed to deliver, without
specifying how to achieve or how to implement them. Those goals and
outcomes are defined in a manner that is purely declarative - they
specify what to accomplish, not how to achieve it."
When applied to transport networks, this implies that an intent for
IETF network 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 aim it can be expected that the intent based system can
fulfill and assure the requested IETF network slice, triggering
initial configurations at the time of initial provisioning and
corrective actions during the IETF network slice lifetime.
Regarding the corrective actions it is possible to differentiate two
levels. First, corrective actions that could be performed by the
management and control capabilities of the network (i.e., by the IETF
Network Slice Controller) to maintain the Service level Objectives
(SLOs) as originally declared in the slice intent, so being these
internal actions to the management and control elements of the
network. Second, corrective actions that could be necessary to
perform due to incongruences between the SLOs expressed in the intent
and the observed monitoring information, then requiring some
adaptation to the intent itself in order to perform the corrective
action.
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3. Foundation of IETF network 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).
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 IETF network 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
IETF network slice controller by using a NBI as proposed in
[I-D.contreras-teas-slice-nbi].
Figure 1 captures the intent procedure for the fulfillment phase
(assurance phase will be detailed in future versions of this draft).
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User Space : Translation / IBS : Network Ops
: Space : Space
: :
+----------+ : +----------+ +-----------+ : +-----------+
Fulfill |recognize/|---> |translate/|-->| learn/ |-->| configure/|
|generate | | | | plan/ | | provision |
|intent |<--- | refine | | render | : | |
+----------+ : +----------+ +-----------+ : +-----------+
: :
.........................................................................
Slice Customer : Slice Provider
-------------- : --------------
:
- Customized Slice : - Identification of IETF : - Slice request
Templates : network slice endpoints : to IETF NSC by
- Service SLOs as : and connectivity pattern : using slice
understood by : - Derivation of network SLOs : NBI YANG model
slice customer : and SLEs from high-level :
: Customer Service SLOs :
: :
Figure 1: Fulfillment phase of the Transport Slicing Intent
4. Mechanisms for translating IETF network slice intents
This section describes approaches for implementing mechanisms to
translate IETF network slice intents. As part of such translation it
could be necessary to translate the slice needs expressed by the
customer in terms of service-specific SLOs (e.g., high-resolution
real-time video quality) to network- or connectivity-specific SLOs
(e.g., a correspondent throughput and/or latency) which are the SLOs
an IETF Network Slice Controller understands. More on this can be
found in [TMV].
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 IETF network 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
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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 an IETF network 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).
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 5.0", NG.116 ,
June 2021.
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[I-D.contreras-teas-slice-nbi]
Contreras, L. M., Homma, S., Ordonez-Lucena, J. A.,
Tantsura, J., and K. Szarkowicz, "IETF Network Slice Use
Cases and Attributes for Northbound Interface of IETF
Network Slice Controllers", draft-contreras-teas-slice-
nbi-05 (work in progress), July 2021.
[I-D.ietf-teas-ietf-network-slices]
Farrel, A., Gray, E., Drake, J., Rokui, R., Homma, S.,
Makhijani, K., Contreras, L. M., and J. Tantsura,
"Framework for IETF Network Slices", draft-ietf-teas-ietf-
network-slices-05 (work in progress), October 2021.
[I-D.irtf-nmrg-ibn-concepts-definitions]
Clemm, A., Ciavaglia, L., Granville, L. Z., and J.
Tantsura, "Intent-Based Networking - Concepts and
Definitions", draft-irtf-nmrg-ibn-concepts-definitions-06
(work in progress), December 2021.
[TMV] "Service performance measurement methods over 5G
experimental networks", 5G-PPP TMV , May 2021.
[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
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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/
Panagiotis Demestichas
WINGS ICT Solutions
Greece
Email: pdemest@wings-ict-solutions.eu
Jeff Tantsura
Microsoft
Email: jefftant.ietf@gmail.com
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