No Working Group A. Galis (editor)
Internet-Draft University College London
Intended Status: Informational et al.
Expires: December 1, 2017 June 2, 2017
Network Slicing - Revised Problem Statement
draft-galis-netslices-revised-problem-statement-03
Abstract
This document introduces Network Slicing problems and the motivation
for new work areas. It represents an initial revision of the Network
Slicing problem statement derived from the analysis of the technical
gaps in IETF protocols ecosystem. It complements and brings together
the efforts being carried out in several other IETF working groups to
achieve certain aspects of Network Slicing functions and operations.
Status of this Memo
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This Internet-Draft will expire on December 1, 2017.
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Table of Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Network Slicing Value Characteristics . . . . . . . . . . . 4
1.2 Network Slicing Work Scope . . . . . . . . . . . . . . . . . 5
1.3 Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
2. Network Slicing - Suggested Problems and Work Areas . . . . . . 7
2.1 Global Issues - Problems (GP) . . . . . . . . . . . . . . . 7
2.1.1 Problem GI1: Uniform Reference Model (***) . . . . . . . 7
2.1.2 Problem GI2: Requirements for operations and
interactions (**) . . . . . . . . . . . . . . . . . . . 8
2.1.3 Problem GI3: Slice Templates (***) . . . . . . . . . . . 9
2.2 Network Slice Capabilities - Problems (NSC) . . . . . . . . 9
2.2.1 Problem NSC1: Guarantees for isolation (***) . . . . . 9
2.2.2 Problem NSC2: Fulfilling diverse requirements (*) . . . 10
2.2.3 Problem NSC3: Efficiency in slicing (*) . . . . . . . . 10
2.2.4 Problem NSC4: Slice Recursion (**) . . . . . . . . . . . 11
2.2.5 Problem NSC5: Customized security mechanisms per slice
(*) . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2.6 Problem NSC6: flexibility and efficiency trade-offs
(*) . . . . . . . . . . . . . . . . . . . . . . . . . . 11
2.2.7 Problem NSC7: Optimisation (**) . . . . . . . . . . . . 12
2.2.8 Problem NSC8: Monitoring (**) . . . . . . . . . . . . . 12
2.2.9 Problem NSC9: Capability exposure and APIs (***) . . . . 12
2.2.10 Problem NSC10: Programmability of Operations of
Network Slices (**) . . . . . . . . . . . . . . . . . . 13
2.3 Network Slice Operations - Problems (NSO) . . . . . . . . . 14
2.3.1 Problem NSO1: Slice life cycle management (***) . . . . 14
2.3.2 Problem NSO2: Autonomic slice management and operation
(**) . . . . . . . . . . . . . . . . . . . . . . . . . . 14
2.3.3 Problem NSO3 - Slice stitching / composition (***) . . . 15
2.3.4 Problem NSO4: E2E Network Orchestration (***) . . . . . 16
2.3.5 Problem NSO5: Service Mapping (**) . . . . . . . . . . . 17
2.3.6 Problem NSO6: Roles in Network Slicing (*) . . . . . . . 17
2.3.7 Problem NSO7: Efficient enablers and methods for
integration (*) . . . . . . . . . . . . . . . . . . . . 18
2.4 Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
3. OAM Operation with Customized Granularity . . . . . . . . . . . 20
4 Security Considerations . . . . . . . . . . . . . . . . . . . . 21
5 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 21
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21
7 References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
7.1 IETF References . . . . . . . . . . . . . . . . . . . . . . 21
7.2 Informative References . . . . . . . . . . . . . . . . . . 23
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 25
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1 Introduction
Network slicing (NS) is an approach of flexible isolation and
allocation of network resources and network functions for a network
instance, providing high level of customization and quality
guarantee. It transform the networking perspective by abstracting,
isolating, orchestrating, softwarizing, and separating logical
network components from the underlying physical network supporting
the introduction of new network architectures ([RFC1958], [RFC3439],
[RFC3234]) and new service delivery [5G-ICN]. In general, a
particular network slice consists of a union of subsets of
(connectivity, storage, computing) resources & (Virtual) Network
Functions & Service functions [RFC7665] at the data & control &
management planes at a given time that are managed together to
provide a logical networking infrastructure in support of a variety
of services.
Network slicing enables creation of multiple, parallel networks of
different features by flexible isolation of allocated to a slice
network resources and network functions and providing high level of
customization and quality guarantee.
The management plane allocates the grouping of network resources
(whereby network resources can be physical, virtual or a combination
thereof), it connects with the physical and virtual network and
service functions ([SFC WG]) as appropriate, and it instantiates all
of the network and service functions assigned to the slice. On the
other hand, for slice operations, the slice control plane
functionality that may be operated by slice tenant, takes over the
control and governing of all the network resources, network
functions, and service functions assigned to the slice. It (re-)
configures them as appropriate and as per elasticity needs, in order
to provide an end-to-end service. In particular, slice ingress
routers are configured so that appropriate traffic is bound to the
relevant slice.
Allocation of traffic flows to slices as may be based on simple rules
(relying on a subset of the transport coordinate, DSCP/traffic class,
or flow label), or may be a more sophisticated one (to be further
defined) such as enabling new slice specific constructs in the data
plane. Also, the flows to slice allocation rules that are specified
for a slice can be changed dynamically, based on some events (e.g.
triggered by a service request). The slice control plane is
responsible for instructing the involved elements to honour such
needs.
Network operators can use NS to enable different services to receive
different treatment and to allow the allocation and release of
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network resources according to the context and contention policy of
the operators. Such an approach using NS would allow significant
reduction of the operations expenditure. In addition, there is a
enabling link between NS and softwarization. On one hand NS makes
possible softwarization, programmability ([RFC7149]), and the
innovation necessary to enrich the offered services. On the other
hand Network softwarization techniques [IMT2020-2015], [IMT2020-2016]
may be used to realise and manage [MANO-2014] network slicing. NS
provides the means for the network operators to provide network
programmable capabilities to both service providers and other market
players without changing their physical infrastructure. NS enables
the concurrent deployment of multiple logical, self-contained and
independent, shared or partitioned networks on a common
infrastructure. Slices may support dynamic multiple services, multi-
tenancy, and the integration means for vertical market players (e.g.
automotive industry, energy industry, healthcare industry, media and
entertainment industry, etc.)
1.1 Network Slicing Value Characteristics
As a differentiation from non-partition networks and those with
simple partitions of connectivity resources (e.g. VPNs)/ Virtual
Networks/Other abstractions of the data traffic layer, the following
key value-added characteristics of Network Slicing and corresponding
usage are identified:
* Network Slice is a dedicated network that is build on an
infrastructure mainly composed of, but not limited to,
connectivity, storage and computing.
* Each network slice has the ability to dynamically expose and
possibly negotiate the parameters that characterize an NS.
* Each network slice will have its own operator that sees it as a
complete network infrastructure (i.e. router instances,
programmability, using any appropriate communication protocol,
caches, provide dynamic placement of virtual network functions
according to traffic patterns, to use its own controller,
finally it can manage its network as its own).
* Network slicing support tenants that are strongly independent on
infrastructure.
* A Network Slicing aware infrastructure allows operators to use
part of the network resources to meet stringent resource
requirements
* Network slicing introduces an additional layer of abstraction by
the creation of logically or physically isolated groups of
network resources and network function/virtual network functions
configurations separating its behavior from the underlying
physical network.
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* Network slicing covers the full life cycle of slices that are
managed groups of infrastructure resources, network functions
and services (e.g. the network slice components are: service
instance, a network functions instance, resources, slice manager
and capability exposure).
* Network slices will need to be self-managed by automated,
autonomic and autonomous, systems in order to cope with dynamic
requirements, such as scalability or extensibility of an
infrastructure (organically growing/shrinking of resources to
meet the size of their organizations)
* Network slices are configurable and programmable and they have
the ability to expose their capabilities and characteristics.
The slice protocols and functions are selected according to
slice required features. The behaviour of the network slice
realized via network slice instance(s).
* Network slices are concurrently deployed as multiple logical,
self-contained and independent, partitioned network functions
and resources on a common physical infrastructure.
* Network slicing supports dynamic multi-services, multi-tenancy
and the means for backing vertical market players.
* Network slicing simplifies the provisioning of services
manageability of networks and integration and operational
challenges especially for supporting. communication services.
* Network slicing offers native service customisation enabled by
the selection and configuration of network functions for
coordinating/orchestration and control of network resource.
* Network slicing considerably transforms the networking
perspective by abstracting, isolating, orchestrating and
separating logical network behaviours from the underlying
physical network resources
1.2 Network Slicing Work Scope
The purpose of the NS work in IETF is to develop a set of protocols
and/or protocol extensions that enable efficient slice creation,
activation / deactivation, composition, elasticity,
coordination/orchestration, management, isolation, guaranteed SLA,
and safe and secure operations within a connectivity network or
network cloud / data centre environment that assumes an IP and/or
MPLS-based underlay.
While there are isolated efforts being carried out in several IETF
working groups Network WG [I-D.leeking-actn-problem-statement 03],
TEAS WG [I-D.teas-actn-requirements-04], [I-D.dong-network-slicing-
problem-statement], ANIMA WG [I-D.galis-anima-autonomic-slice-
networking], [IETF-Slicing1], [IETF-Slicing2], [IETF-Slicing3],
[IETF-Slicing4], [IETF-Slicing5], [IETF-Mobility], [IETF-
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Virtualization], [IETF-Coding], [IETF-Anchoring] to achieve certain
aspects of network slice functions and operations, there is a clear
need to look at the complete life-cycle management characteristics of
Network Slicing solutions though the discussions based on the
following architectural tenets:
* Underlay tenet: support for an IP/MPLS-based underlay data
plane.
* Governance tenet: a logically centralized authority for network
slices in a domain.
* Separation tenet: slices may be virtually or physically
independent of each other and have an appropriate degree of
isolation (note 1) from each other.
* Capability exposure tenet: each slice allows third parties to
access via dedicated interfaces and /or APIs and /or programming
methods information regarding services provided by the slice
(e.g., connectivity information, mobility, autonomicity, etc.)
within the limits set by the operator or the slice owner.
NS approaches that do not adhere to these tenets are explicitly
outside of the scope of the proposed work at IETF.
In pursuit of the solutions described above, there is a need to
document an architecture for network slicing within both wide area
network and edge/central data center environments.
Elicitation of requirements (examples are [RFC2119], [RFC4364]) for
both Network Slice control and management planes will be needed,
Facilitating the selection, extension, and/or development of the
protocols for each of the functional interfaces identified to support
the architecture.
Additionally, documentation on the common use-cases for slice
validation for 5G is needed, such as mission-critical ultra-low
latency communication services; massive-connectivity machine
communication services (e.g. smart metering, smart grid and sensor
networks); extreme QoS; independent operations and management;
independent cost and/or energy optimisation; independent multi-
topology routing; multi-tenant operations; new network architecture
enablement, etc.
The proposed NS work would be coordinated with other IETF WGs (e.g.
TEAS WG, DETNET WG, ANIMA WG, SFC WG, NETCONF WG, SUPA WG, NVO3 WG,
DMM WG, Routing Area WG (RTGWG), Network Management Research Group
(NMRG) and NFV Research Group (NFVRG)) to ensure that the
commonalities and differences in solutions are properly considered.
Where suitable protocols, models or methods exist, they will be
preferred over creating new ones.
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1.3 Notes
(1) This issue requires efficient interaction between an upper
layer in the hierarchy and a lower layer for QoS guarantees
and for most of the operations on slicing.
2. Network Slicing - Suggested Problems and Work Areas
The goal of this proposed work is to develop one or more protocol
specifications (or extensions to existing protocols) to address
specific slicing problems that are not met by the existing tools. The
following problems were selected according to the analysis of the
technical gaps in IETF protocols ecosystem. In addition an initial
priority level is attached to each problem. [(***) high priority,
(**) medium priority and (*) low priority]. The proposed WG charter
would include at least the high priority problems.
2.1 Global Issues - Problems (GP)
2.1.1 Problem GI1: Uniform Reference Model (***)
Uniform Reference Model for Network Slicing (Architecture document):
* Description of all of the functional elements required for
network slicing.
* Description of shared non-sliced network parts. Establishes the
boundaries to the basic network slice operations (creation,
management, exposure, consumption).
* Describes the minimum functional roles derived from basic
network slice operations including infrastructure owner
(creation, exposure, management), slice operator (exposure,
management, consumption), slice customer (management,
consumption). Describe the interactions between infrastructure
owner <-> slice operator, slice operator <-> slice operator,
slice operator <-> slice customer.
* Additionally, this working area will normalize nomenclature and
definitions for Network Slicing.
Short explanation: A uniform definition and architecture of Network
slicing is presented in the NS Architecture draft. A Network slice is
a managed group of subsets of resources, network functions/network
virtual functions at the data, control, management/orchestration
planes and services at a given time. Network slice is programmable
and has the ability to expose its capabilities. The behaviour of the
network slice realized via network slice instance(s).
(1) The Service Instance Component represents the end-user service
or business services. An instance of an end-user service or a
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business service that is realized within or by a NS. Would be
provided by the network operator or by 3rd parties.
(2) A Network Slice Instance component
a. Represented by a set of network functions, virtual network
functions and resources at a given time
b. Forms a complete instantiated logical network to meet
certain network characteristics required by the Service
Instance(s).
c. Provides network characteristics which are required by a
Service Instance.
d. May also be shared across multiple Service Instances
(3) Resources component - it includes: Physical, Logical & Virtual
resources
a. Physical & Logical resources - An independently manageable
partition of a physical resource, which inherits the same
characteristics as the physical resource and whose
capability is bound to the capability of the physical
resource. It is dedicated to a Network Function or shared
between a set of Network Functions.
b. Virtual resources - An abstraction of a physical or logical
resource, which may have different characteristics from
that resource, and whose capability may not be bound to the
capability of that resource.
(4) Slice Element Manager (SEM) and Capability exposure component
a. Slice Element Manager (SEM) is instantiated in each Network
Slice and it manages all access permissions and all
interaction between a Network Slice and external functions
(i.e. other Network Slices, Orchestrators, etc). Each SEM
converts requirements from orchestrator into virtual
resources and manages
Consolidation and versification of the above definition is required.
New protocols are needed for the creation, for discovery and for
orchestrating network slicing.
2.1.2 Problem GI2: Requirements for operations and interactions (**)
Review common scenarios from the requirements for operations and
interactions point of view. Describes the roles (owner, operator,
user) which are played by entities with single /multiple entities
playing different roles.
Short explanation: Review of the functional and non- functional NS
requirements is needed to ensure that resource utilization is
maximised and infrastructure costs are minimised as services will
need to operate over a union of shared network infrastructures, as
against the traditional monolithic model operated either as dedicated
network or as an overlay.
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2.1.3 Problem GI3: Slice Templates (***)
Design the slices to different scenarios [ChinaCom-2009], [GENI-
2009], [IMT2020-2016bis], [NGMN-2016], [NGS-3GPP-2016], [ONF-2016]);
Outlines an appropriate slice template definition that may include
capability exposure of managed partitions of network resources (i.e.
connectivity ([CPP]), compute and storage resources), physical and/or
virtual network and service functions that can act as an independent
connectivity network and/or as a network cloud.
Short explanation: A network slice template based on uniform
reference model would enable the creation of a network slice
instance. A template defines an abstraction of the overall network
resources and functions requirement for a particular network slice
instance. Different templates can also be regarded as definitions of
individual network slice types. Besides the reference model for
network resources and functions, each template has a complete
description of the structure, configuration and the plans/work flows
for how a certain type of network slice instance should be
instantiated and managed during its life cycle.
There should be a clear definition of the level of abstraction of the
network slice template according to the arrangement and specification
of network slice life cycle management system. A valid network slice
instance profile created based on specific network slice template is
going to be decomposed into configuration profiles to certain OAM
domains for the purpose of network slice instance creation.
The creation of a specific network slice template strictly relies on
the exposed network capabilities. The network slice life cycle
management system should not allow a template with parameters
exceeding the capabilities to be created.
2.2 Network Slice Capabilities - Problems (NSC)
2.2.1 Problem NSC1: Guarantees for isolation (***)
Four-dimensional efficient slice creation with guarantees for
isolation in each of the Data /Control /Management /Service planes.
Enablers for safe, secure and efficient multi-tenancy in slices.
Short explanation: Network slices MUST support multi-tenancy,
ensuring that isolation and performance guarantees are provided at
the data, control, management and service planes. This involves the
following:
* A network slice SHOULD provide a guaranteed level of service,
according to a negotiated SLA between the customer and the slice
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provider
* Slices MUST be isolated at service level (e.g., one slice must
not impact on the level of service of the other slides, even if
sharing resources).
* Slices MUST be isolated at data level, even if sharing
resources. Security and privacy mechanisms should be in place to
ensure this.
* A network slice SHOULD be provided with exclusive control and/or
management interfaces (depending on the type of network slice),
enabling the deployment of different logical network slices over
shared resources.
2.2.2 Problem NSC2: Fulfilling diverse requirements (*)
Methods to enable diverse requirements for NS including guarantee for
the end-to-end QoS of service in a slice.
Short explanation: The main goal of fulfilling NS requirements is to
ensure that service operators can utilize or benefit from Network
Slicing through multi-tenancy, enabling different customized
infrastructures for different group of services across different
network segments and operating them independently. It includes the
tasks that go into determining the needs or conditions to meet for NS
systems, taking account of the possibly conflicting requirements of
the various stakeholders and a prioritisation of requirements. New
protocols are needed for interoperability between diverse type of
network slices which are fulfilling diverse requirements
2.2.3 Problem NSC3: Efficiency in slicing (*)
Specifying policies and methods to realize diverse requirements
without re-engineering the infrastructure.
Short explanation: This item is deployment-specific and cannot be
promised as a problem to be solved entirely by protocols. An
underlying infrastructure will always be needed to be reengineered
and maintained to support up-to-date technologies and emerging
requirements (including instantiating new service functions or
withdrawing service functions, adding new nodes to absorb for
traffic, ...). It is a local decision to figure out whether many
services will be bound to the same slice, how many slices are to be
instantiated and so on. Exposing standard interfaces to capture
requirements will help to rationale the use of resources and how the
requirements are fulfilled, however it is a challenge to guarantee in
an absolute manner that slicing allows "diverse requirements without
re-engineering the infrastructure".
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2.2.4 Problem NSC4: Slice Recursion (**)
Short explanation: Recursion is a property of some functional blocks:
a larger functional block can be created by aggregating a number of a
smaller functional block and interconnecting them with a specific
topology. As such recursive network slice definition is defined as
the ability to build a new network slice out of existing network
slice (s). A certain resource or network function /virtual network
function could scale recursively, meaning that a certain pattern
could replace part of itself. This leads to a more elastic network
slice definition, where a network slice template, describing the
functionality, can be filled by a specific pattern or implementation,
depending on the required performance, required QoS or available
infrastructure.
New protocols are needed for use of network slice template
segmentation allowing a slicing hierarchy with parent - child
relationships.
2.2.5 Problem NSC5: Customized security mechanisms per slice (*)
Short explanation: Customized securing mechanisms will be needed on a
per slice basis. This may be provided by enabling dedicated service
functions. For such cases, SFC techniques can be used here.
Soliciting distinct SFs per slice can be provided with existing
tools. I don't see a new problem out there.
This may be provided by configuring dedicated policies in a given
security service function. In such case, I2NSF techniques can be used
to interact with a given service function.
Traffic isolation may be needed for some services. Legacy tools can
be used. I'm not sure if there is specific work specific to slicing
other than making sure that appropriate flows are grafted to the
appropriate slice and no data leaking between slices is to happen.
2.2.6 Problem NSC6: flexibility and efficiency trade-offs (*)
Methods and policies to manage the trade-offs between flexibility and
efficiency in slicing.
Short explanation: Mechanisms SHOULD be in place to allow different
levels of flexibility when providing network slices: from the ones
that provided greater levels of flexibility in the provided resources
and services that compound the slice, allowing to dynamically
change/scale/migrate it over time within a negotiated range, to the
ones that ensure the efficiency of the use of the resources at the
cost of a smaller degree of flexibility.
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2.2.7 Problem NSC7: Optimisation (**)
Methods for network resources automatic selection for NS; global
resource view formed; global energy view formed; Network Slice
deployed based on global resource and energy efficiency; Mapping
protocols.
Short explanation: NS optimisation includes methods which enable that
resources utilization is monitored and maximise, that infrastructure
operational costs are minimised and that QoS are managed and
maximised at the time of creation of network slice instance and well
as during NS operation.
2.2.8 Problem NSC8: Monitoring (**)
Monitoring status and behaviour of NS in a single and/or muti-domain
environment; NS interconnection.
Short explanation: A Network slice is a managed group of subsets of
resources, network functions / network virtual functions at the data,
control, management/orchestration planes and services at a given
time. Monitoring of slices interacts with and it is part of the NS
Lifecycle management to aiming at reporting the performance of the
running NS. As input, the Monitoring Subsystem receives the detailed
service monitoring requests with references to resource allocation
and Network functions instances in a NS. The Monitoring Subsystem is
responsible for the monitoring continuously the state all 4
components of a NS (Service Instance component, Network Slice
Instance component, Resources component).
New protocols are needed for discovery and monitoring probes of all
NS components and NS itself.
2.2.9 Problem NSC9: Capability exposure and APIs (***)
Capability exposure for NS; plus APIs for slices
Short explanation: To exploit the flexibility offered by network
slices their users (customers, overlying operators) would need to
know the features offered by both individual resources and complete
slices. This means that there must be interfaces to deliver such
information to the entity that needs it, but that will be also
transitively delivered to the following chains of the slicing
structure towards the final users.
To this sense, there are two specific interfaces that must be defined
to address such function:
* The bottom-up interface, offered by underlying resource
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providers to resource consumers (operators) of any layer.
* The top-down interface, offered by overlying operators to lower
level providers.
On the one hand, the first interface will, obviously, enable slice
operators to access the slices owned by underlying providers and
manage the resources they have been assigned in them. On the other
hand, the second interface will enable lower layers to know details
about the resources managed by overlying operators and the
requirements they impose to the overlying network slices.
In this respect, both interfaces will emphasize the relation among
the original resources, as well as the links from them to the
resulting resources. This forms the main key of their management
operations.
2.2.10 Problem NSC10: Programmability of Operations of Network Slices
(**)
Short explanation: Network slice operations consist of all operations
related to life cycle management of a slice and its optimized
operation. Slice instance lifecycle management includes all
operations related to slice instance creation, activation, update and
deactivation. All these operations are automated and driven by
appropriate policies. A slice instance is created according to a
slice template and related policies. A unique identifier is assigned
to each slice after its creation and a list of active slice instances
are stored in slice repository. Several slice types are predefined
which describe their functions as access, core, transport, data
center and edge cloud slices. As example to each slice instance a
Slice Priority parameter is assigned which describe the way of
handling of slice degradation in case of lack of resources that can
be allocated to slices. The parameter is also used in emergency
situations in which there is a need to release resources from
existing slices and to allocate them to newly created slices that are
used for emergency situation handling.
The end-to-end slice can be a composition of per administrative or
technological domain slices that are created according to their local
templates. The process of slice creation can be recursive. The slice
level are split between slice operator and slice tenant. The slice
tenant obtains information about slices related KPIs and is
expressing his reconfiguration wills as intents (high level
policies), which are implemented in an automated manner by slice
control and management planes. The slice operator is responsible for
slice lifecycle and slice FCAPS handling. During operations of slice
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the slice resources are allocated in a dynamic way in order to
provide required performance but in an economical way.
Each network slice exhibits following features: protection (note 2),
elasticity (note 3), extensibility (note 4) and safety (note 5).
2.3 Network Slice Operations - Problems (NSO)
2.3.1 Problem NSO1: Slice life cycle management (***)
Slice life cycle management including creation, activation /
deactivation, protection (note 2), elasticity (note 3), extensibility
(note 4), safety (note 5), sizing and scalability of the slicing
model per network and per network cloud: slices in access, core and
transport networks; slices in data centres, slices in edge clouds.
Short explanation: Network slicing enables the operator to create
logically partitioned networks at a given time customized to provide
optimized services for different market scenarios. These scenarios
demand diverse requirements in terms of service characteristics,
required customized network and virtual network functionality (at the
data, control, management planes), required network resources,
performance, isolation, elasticity and QoS issues. A network slice is
created only with the necessary network functions and network
resources at a given time. They are gathered from a complete set of
resources and network /virtual network functions and orchestrated for
the particular services and purposes.
New protocols are needed for realising full Slice life cycle
management at two distinct levels:
(1) "network slice life-cycle management level" (i.e. the series of
state of functional activities through which a network slice
passes: creation, operation, deletion) and
(2) "network slice instances level" (activated network slice
level).
Functions for creating and managing network slice instances and the
functions instantiated in the network slice instance are mapped to
respective framework level.
2.3.2 Problem NSO2: Autonomic slice management and operation (**)
It incudes self-configuration, self-composition, self-monitoring,
self-optimisation, self-elasticity are carried as part of the slice
protocols.
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Short explanation: Network slice is a dynamic entity which lifecycle
and operations should be automated. There are 3 main reasons of this
automation:
(1) There is an expectation that the number of slice instances can
be huge what rises the problem of management scalability if it
is performed in a classical, manual way.
(2) Network slice instances can be created on demand by the end-
users or verticals. They may play a role of slice instance
administrator (making some reconfigurations or monitoring slice
performance. It is however not expected that such administrator
will have required experience and tools related to slice
instance management. They can express some high-level requests
that has to be translated into low level operations
(3) Multiple network slice instances have to share common resources
in economical way but with preserving required performance
indicators. The problem of allocation of resources between
slices combined with real-time optimization of slice operations
can be only solved by continuous monitoring of slice performance
and making continuous adaptations of resources allocated to
them.
The mentioned reasons call for autonomic management which part should
be autonomic management of each slice and autonomic management of
resources that are allocated to slices. The autonomic operations at
the slice instance level comprise of self-configuration, self-
composition, efficient self-monitoring, self-healing and real-time
optimization (self-optimisation) as a part of the autonomic
management framework.
2.3.3 Problem NSO3 - Slice stitching / composition (***)
Having enablers and methods for efficient stitching /composition/
decomposition of slices:
* vertically (service + management + control planes) and/or
* horizontally (between different domains part of access, core,
edge segments) and /or
* vertically + horizontally.
Short explanation: Slice stitching. The network slice has to provide
end-to-end communication and services. In some cases such end-to-end
network slice instance can be created directly but in multi-domain
environment the end-to slice will be a composition of slices of
different domains in the each network segments (i.e. access, core,
edge, transport, etc.). In such a case the domain slices will be
created and maintained using domain specific slice templates and use
domain specific operations and all the domain slicing will be
stitched together horizontally. The operation is supported by
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appropriate descriptions of domain slices, exchange of slice related
policies between domains. Slice stitching operations are supported by
uniform slice descriptors and appropriate matching of them. Each
slices has appropriate set of mechanisms (slice border control
functions) that support horizontal stitching of slices.
The vertical stitching of slices is an operation that modifies
functionality of existing slice by adding and merging of functions of
another slice (i.e. enhancing control plane properties be functions
defined in another slice template). In general the vertical stitching
of slices is used to enrich slice services.
Slices will be recursively used as components in software
architectures. This means that several slices will be able to be used
together to build a "composite network service" that inherits the
capabilities of the original slices. The recursive property means
that both slices and derived composite services can be again "split"
into pieces to form new slices. The straight result of this aspect is
that complex services are highly simplified by "stitching" slices
and/or part of them, achieving the actual complexity by exploiting
layering, which is the de-facto standard composition capability
typically mapped into network architectures, but also by exploiting
the abstraction levels offered by network service composability.
However, to hide such complexity and thus achieve the intended
abstraction, the network architecture (and slicing reference model)
must include, adopt, and promote the deployment of the necessary
mechanisms and functions that support slice stitching and network
service composability.
2.3.4 Problem NSO4: E2E Network Orchestration (***)
End-to-end network segments orchestration of slices ([GUERZONI-2016],
[KARL-2016]).
Short explanation: Network service composition has demonstrated to be
highly beneficial for both operators and final users [GRAMMATIKOU-
2012]. It allows the formation of large number of different services,
which will be specialized to the particular needs of a user or a
specific situation. However, the current network architecture is far
for being ideal to implement such function.
One of the keys of network slicing is the flexibility it adds to the
network and the resulting "de-ossification" of network resources.
Thus, this environment is much more optimal to allow the
proliferation of network service composition, but it means that some
sort of specific requirements must be pushed towards the architecture
that supports the general slicing.
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First, a proper composable network service model needs network
resources to be compatible, regardless of the domain to which they
pertain. Then they must be homogeneously described, so a user can
actually understand their individual capabilities and "draw" the
service they want to build by combining them. Finally, the resources
living among separated network slices must be "connectable" to each
other. This means that they must cross the domain of their
providers/owners in order to reach their destination.
New protocols are needed for full end to end orchestration between
the layers, from the IP layer and up.
2.3.5 Problem NSO5: Service Mapping (**)
Having dynamic and Automatic Mapping of Services to slices; YANG
models for slices.
Short Description: The main goal of the service mapping framework is
to enable on-demand processing anywhere in the physically distributed
network, with dynamic and fine granular service (re-)provisioning,
which can hide significant part of the resource management complexity
from service providers and users, hence allowing them to focus on
service and application innovation. It include a slice-aware YANG
information model based on necessary connectivity, storage, compute
resources, network functions, capabilities exposed and service
elements. As such the service mapping participates in management of
the network slices.
2.3.6 Problem NSO6: Roles in Network Slicing (*)
Enablers and methods for the above mentioned capabilities and
operations from different viewpoints on slices (note 6).
Short explanation: Several viewpoints emerge from the global and
wide interaction among the Network Infrastructure Owner (NIO),
Network Slice Provider (NSP), and Network Slice Tenant(NST), and they
must be treated by network slicing to ensure their use cases are
correctly covered. They are:
- NIO <=> NSP:
+ NIO offers the physical infrastructure to NSP, and NSP
creates and manages the "slice" of network resources.
+ NSP interacts vertically to request and instantiate (embed)
composite network services onto the underlying physical
infrastructures.
+ NSP can possibly act as NIO.
- NSP <=> NST:
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+ NSP offers the individual objects/resources obtained after
slicing the physical infrastructure to the NST.
+ NST requests to the NSP the necessary CRUD (Create,
Retrieve, Update, Delete) operations on its own Network
Slices.
- NSP <=> NSP:
+ Allows inter-provider tasks (e.g. migration of resources or
whole slices among providers.
+ Organizes the interoperability levels among Network Slices
managed by different providers.
+ Facilitates the recursive slicing, so a new NSP slices the
resources offered by other NSP.
- NIO <=> NIO:
+ Horizontal communication between owners to coordinate the
required interactions among physical infrastructure
resources, and/or the migration of whole slices among
different NIOs.
+ It may be common for NIO to provide network infrastructures
to NSP in an old-fashion way where no network slicing is
concerned.
However, a NIO may become a double role of NIO+NSP once it provides
NSaaS.
Any NSP can become a NST if it uses specific network slice instance
for a particular service, or it purchase NSaaS from another NSP.
2.3.7 Problem NSO7: Efficient enablers and methods for integration (*)
Efficient enablers and methods for integration of above capabilities
and operations.
Short explanation: In order to enable the above required capabilities
and operation for network slicing, well defined reference points
among the involved actors and entities are required, as well as the
proper interface definitions ensuring interoperability of all
involved pieces. Some examples of the required reference
points/interfaces include:
Customer/Vertical (user of the slice) - Network Slice Provider. The
user of the slice SHOULD be able to specify the characteristics of
the slide and provide it in a suitable/understandable format to the
NSP. A proper information model is needed to convey the customer
slice requirements. And the model might need to support different
levels of abstraction, to support different use cases.
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Network Slice Provider - Network Slice Provider / Network Slice
Operator / Network Service Provider. The slice provider MUST be able
to request resources to compose a slice to other slice providers,
slice operator or service operators. The interface needs to support
recursiveness and different levels of abstraction (the request might
involve resources or services).
Inter-domain interactions at different levels. Another way of
composing a slice is by interaction of players at the same level
(peering, instead of recursive), by delegating the request to other
provides/operators. This type of interaction can take place at
different levels (resource, network service, etc), and therefore
would impose different requirements. In all cases, security issues
are key due to the inter-operator nature.
2.4 Notes
(1) Protection refers to the related mechanisms so that events
within one slice, such as congestion, do not have a negative
impact on another slice.
(2) Elasticity refers to the mechanisms and triggers for the
growth/shrinkage of network resources, and/or network and
service functions.
(3) Extensibility refers to the ability to expand a NS with
additional functionality and/or characteristics, or through
the modification of existing functionality/characteristics,
while minimizing impact to existing functions.
(4) Safety refers to the conditions of being protected against
different types and the consequences of failure, error harm or
any other event, which could be considered non-desirable.
(5) Multiple viewpoints on slices: I) viewpoint of the slice's
owner towards user: from this viewpoint a slice is defined as
a means to "split" physical or virtual infrastructure elements
to "service" smaller portions. This action would be
recursively done from the owner of the initial and physical
infrastructure element to the users. II) viewpoint of from the
user towards the physical infrastructure owner. From this
viewpoint a slice is viewed just as a set of resources that
must be managed (requests to a provider, listed, changed,
returned to the provider, etc.). This viewpoint emphasizes
those issues that would be used in the SLA definition of a
slice.
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3. OAM Operation with Customized Granularity
In accordance with [RFC6291], OAM is used to denote the following:
* Operations: refer to activities that are undertaken to keep the
network and the services it deliver up and running. It includes
monitoring the underlying resources and identifying problems.
* Administration: refer to activities to keep track of resources
within the network and how they are used.
* Maintenance: refer to activities to facilitate repairs and
upgrades. Maintenance also involves corrective and preventive
measures to make the managed network run more effectively, e.g.,
adjusting configuration and parameters.
As per [RFC6291], NetSlices provisioning operations are not
considered as part of OAM. Provisioning operations are discussed in
other sections. Maintaining automatically-provisioned slices within a
network raises the following requirements:
* Ability to run OAM activities on a provider's customized
granularity level. In other words, ability to run OAM activities
at any level of granularity that a service provider see fit. In
particular:
- An operator must be able to execute OAM tasks on a per slice
basis.
- These tasks can cover the "whole" slice within a domain or
portion of that slice (for troubleshooting purposes, for
example).
- For example, OAM tasks can consist in tracing resources that
are bound to a given slice, tracing resources that are
invoked when forwarding a given flow bound to a given
network slice, assessing whether flow isolation
characteristics are in conformance with the NS Resource
Specification, or assessing the compliance of the allocated
slice resource against flow/customer requirements.
- An operator must be able to enable differentiated failure
detect and repair features for a specific/subset of network.
For example, a given slice may require fast detect and
repair mechanisms (e.g., as a function of the nature of the
traffic (pattern) forwarded through the NS), while others
may not be engineered with such means.
- When a given slice is shared among multiple
services/customers, an operator must be able to execute
(per-slice) OAM tasks for a particular service or customer.
* Ability to automatically discover the underlying service
functions and the slices they are involved in or they belong
to.
* Ability to dynamically discover the set of NetSlices that are
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enabled within a network. Such dynamic discovery capability
facilitates the detection of any mismatch between the view
maintained by the control plane and the actual network
configuration. When mismatches are detected, corrective
actions must be undertaken accordingly.
4 Security Considerations
Security will be a major part of the design of network slicing.
5 IANA Considerations
This document requests no IANA actions.
6. Acknowledgements
Thanks to Sheng Jiang (Huawei Technologies), Kevin Smith (Vodafone),
Satoru Matsushima (SoftBank), Christian Jacquenet (Orange), Mohamed
Boucadair (Orange) for reviewing this draft. Thanks to Stuart Clayman
(UCL) for creating the nroff markup for this document.
7 References
7.1 IETF References
[I-D.dong-network-slicing-problem-statement] Dong, J. and S. Bryant,
"Problem Statement of Network Slicing in IP/MPLS
Networks", draft-dong-network-slicing-problem-statement-00
(work in progress), October 2016.
[I-D.galis-anima-autonomic-slice-networking] Galis, A., Makhijani,
K., and D. Yu, "Autonomic Slice Networking-Requirements
and Reference Model", draft-galis-anima-autonomic-slice-
networking-01 (work in progress), October 2016.
[RFC7665] Halpern, J., Pignataro, C., "Service Function Chaining
(SFC) Architecture", https://tools.ietf.org/html/rfc7665,
October 2015.
[I-D.leeking-actn-problem-statement 03] Ceccarelli, D., Lee, Y.,
"Framework for Abstraction and Control of Traffic
Engineered Networks", draft-leeking-actn-problem-
statement-03 (work in progress), September 2014.
[I-D.teas-actn-requirements-04] Lee, Y., Dhody, D., Belotti, S.,
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INTERNET DRAFT Network Slicing Revised Problem Statement June 2017
Pithewan, K., Ceccarelli, D., "Requirements for
Abstraction and Control of TE Networks", draft-ietf-teas-
actn-requirements-04.txt, January 2017.
[IETF-Slicing1] "Presentations - Network Slicing meeting at IETF 97
of 15th November 2016", n.d.,
<https://www.dropbox.com/s/ax2ofdwygjema8z/0-
Network%20Slicing%20Side%20Meeting%20Introduction_
IETF97.pdf>.
[IETF-Slicing2] "Presentations - Network Slicing meeting at IETF 97
of 15th November 2016", n.d.,
<https://www.dropbox.com/s/k2or6sd0ddzrc6c/1-
Network%20Slicing%20Problem%20Statement_IETF97.pdf>.
[IETF-Slicing3] "Presentations - Network Slicing meeting at IETF 97
of 15th November 2016", n.d.,
<https://www.dropbox.com/s/g8zvfvbrtkysjs1/2-
Autonomic%20Slice%20Networking_IETF97.pdf>.
[IETF-Slicing4] "Presentations - Network Slicing meeting at IETF 97
of 15th November 2016", n.d.,
<https://www.dropbox.com/s/d3rk4pjeg552ilv/3-
Architecture%20for%20delivering%20multicast%20mobility
%20services%20using%20network%20slicing_IETF97.pdf>.
[IETF-Slicing5] "Presentations - Network Slicing meeting at IETF 97
of 15th November 2016", n.d.,
<https://www.dropbox.com/s/e3isn1bxwwhaw8g/4-
ACTN%20and%20network%20slicing_IETF97.pdf>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI
10.17487/RFC2119, March 1997, <http://www.rfc-
editor.org/info/rfc2119>.
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February
2006, <http://www.rfc-editor.org/info/rfc4364>.
[RFC1958] Carpenter, B., "Architectural Principles of the Internet",
RFC 1958, <https://www.ietf.org/rfc/rfc1958.txt>.
[RFC3439] Bush, R., Meyer, D., "Some Internet Architectural
Guidelines and Philosophy", RFC3439,
<https://www.ietf.org/rfc/rfc3439.txt>.
[RFC3234] Carpenter, B., Brim S., "Middleboxes: Taxonomy and Issues",
Galis, et al. Expires December 1, 2017 [Page 22]
INTERNET DRAFT Network Slicing Revised Problem Statement June 2017
RFC3439, <https://tools.ietf.org/html/rfc3234>.
[RFC7149] Boucadair, M., Jacquenet, C. , " Software-Defined
Networking: A Perspective from within a Service Provider
Environment", RFC 7149, March 2014
<https://tools.ietf.org/html/rfc7149>.
[SFG WG] "Service Function Chaining WG"
<https://datatracker.ietf.org/doc/charter-ietf-sfc/>.
[CPP] Boucadair M., Jacquenet, C., Wang, N., "IP Connectivity
Provisioning Profile (CPP)"
https://tools.ietf.org/html/rfc7297
[IETF-Mobility] Truong-Xuan Do, Young-Han Kim, "Architecture for
delivering multicast mobility services using network
slicing" 2016-10-31<draft-xuan-dmm-multicast-mobility-
slicing-00.txt>
[IETF-Virtualization] Carlos Bernardos, Akbar Rahman, Juan Zuniga,
Luis Contreras, Pedro Aranda, " Network Virtualization
Research Challenges" 2016-10-31<draft-irtf-nfvrg-gaps-
network-virtualization-03.txt>
[IETF-Coding] M.A. Vazquez-Castro, Tan Do-Duy, Paresh Saxena, Magnus
Vikstrom, "Network Coding Function Virtualization" 2016-
11-14 <draft-vazquez-nfvrg-netcod-function-virtualization-
00.txt>
[IETF-Anchoring] Anthony Chan, Xinpeng Wei, Jong-Hyouk Lee, Seil
Jeon, Alexandre Petrescu, Fred Templin "Distributed
Mobility Anchoring" 2016-12-15 <draft-ietf-dmm-
distributed-mobility-anchoring-03.txt,.pdf>
[RFC6291] L. Andersson, H. van Helvoort, R. Bonica, D. Romascanu, S.
Mansfield "Guidelines for the Use of the "OAM" Acronym in
the IETF" - June 2011 https://tools.ietf.org/html/rfc6291
7.2 Informative References
[ChinaCom-2009] "A. Galis et al - Management and Service-aware
Networking Architectures (MANA) for Future Internet -
Invited paper IEEE 2009 Fourth International Conference on
Communications and Networking in China (ChinaCom09) 26-28
August 2009, Xi'an, China", n.d.,
<http://www.chinacom.org/2009/index.html>.
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INTERNET DRAFT Network Slicing Revised Problem Statement June 2017
[GENI-2009] "GENI Key Concepts - Global Environment for Network
Innovations (GENI)", n.d.,
<http://groups.geni.net/geni/wiki/GENIConcepts>.
[GUERZONI-2016] "Guerzoni, R., Vaishnavi, I., Perez-Caparros, D.,
Galis, A., et al Analysis of End-to-End Multi Domain
Management and Orchestration Frameworks for Software
Defined Infrastructures - an Architectural Survey", June
2016, <onlinelibrary.eiley.com/10.1002/ett.3084/pdf>.
[IMT2020-2015] "Report on Gap Analysis", ITU-T FG IMT2020, December
2015, <http://www.itu.int/en/ITU-T/focusgroups/imt-
2020/Pages/default.aspx>.
[IMT2020-2016] "Draft Technical Report Application of network
softwarization to IMT-2020 (O-041)", ITU-T FG IMT2020,
December 2016, <http://www.itu.int/en/ITU-
T/focusgroups/imt-2020/Pages/default.aspx>.
[IMT2020-2016bis] "Draft Terms and definitions for IMT-2020 in ITU-T
(O-040)", ITU-T FG IMT2020, December 2016,
<http://www.itu.int/en/ITU-T/focusgroups/imt-
2020/Pages/default.aspx>.
[KARL-2016] "Karl, H., Peuster, M, Galis, A., et al DevOps for
Network Function Virtualization - An Architectural
Approach", July 2016, <http://onlinelibrary.wiley.com/doi/
10.1002/ett.3084/full>.
[MANO-2014] "Network Functions Virtualisation (NFV); Management and
Orchestration v1.1.1.", ETSI European Telecommunications
Standards Institute., December 2014,
<http://www.etsi.org/deliver/etsi_gs/NFV-
MAN/001_099/001/01.01.01_60/gs_nfv-man001v010101p.pdf>.
[NGMN-2016] "Hedmar,P., Mschner, K., et al - Description of Network
Slicing Concept", NGMN Alliance NGS-3GPP-2016, January
2016, <https://www.nmn.org/uploads/media/
160113_Network_Slicing_v1_0.pdf>.
[NGS-3GPP-2016] "Study on Architecture for Next Generation System -
latest version v1.0.2", September 2016,
<http://www.3gpp.org/ftp/tsg_sa/WG2_Arch/Latest_SA2_Specs/
Latest_draft_S2_Specs>.
[ONF-2016] Paul, M, Schallen, S., Betts, M., Hood, D., Shirazipor,
M., Lopes, D., Kaippallimalit, J., - Open Network
Fundation document "Applying SDN Architecture to 5G
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INTERNET DRAFT Network Slicing Revised Problem Statement June 2017
Slicing", Open Network Fundation, April 2016,
<https://www.opennetworking.org/images/stories/downloads/
sdn-resources/technical-reports/
Applying_SDN_Architecture_to_5G_Slicing_TR-526.pdf>.
[5G-ICN] Ravi Ravindran, Asit Chakraborti, Syed Obaid Amin, Aytac
Azgin, G.Q.Wang, "5G-ICN: Delivering ICN Services in 5G
using Network Slicing", IEEE Communication Magazine, May,
2017.
[GRAMMATIKOU-2012] Grammatikou, M; Marinos, C; Martinez-Julia, P;
Jofre, J; Gheorghiu, S; et al. Proceedings of the
International Conference on Parallel and Distributed
Processing Techniques and Applications (PDPTA); Athens: 1-
5. Athens: The Steering Committee of The World Congress in
Computer Science, Computer Engineering and Applied
Computing (WorldComp). (2012)
[GAPS] Gap Analysis for Network Slicing draft-qiang-netslices-gap-
analysis-00
[NS UseCases] Network Slicing Use Cases: Network Customization for
different services draft-makhijani-netslices-usecase-
customization-02
[NS ARCH] Network Slicing Architecture draft-geng-netslices-
architecture-01
Authors' Addresses
Alex Galis
University College London
Email: a.galis@ucl.ac.uk
Slawomir Kuklinski
Orange
Email: slawomir.kuklinski@orange.com
Jie Dong
Huawei Technologies
Email: jie.dong@huawei.com
Liang Geng
China Mobile
Email: gengliang@chinamobile.com
Galis, et al. Expires December 1, 2017 [Page 25]
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Kiran Makhijani
Huawei Technologies
Email: kiran.makhijani@huawei.com
Hannu Flinck
Nokia
Email: hannu.flinck@nokia-bell-labs.com
Ravi Ravindran
Huawei Technologies
Email: ravi.ravindran@huawei.com
Luis Miguel Contreras Murillo
Telefonica
Email: luismiguel.contrerasmurillo@telefonica.com
Stewart Bryant
Huawei Technologies
Email: stewart.bryant@gmail.com
Pedro Martinez-Julia
National Institute of Information and Communications Technology
(NICT)
Email: pedro@nict.go.jp
Susan Hares
Huawei Technologies
Email: shares@ndzh.com
Carlos Jesus Bernardos Cano
University Carlos III Madrid
Email: cjbc@it.uc3m.es
Galis, et al. Expires December 1, 2017 [Page 26]