Internet DRAFT - draft-defoy-netslices-3gpp-network-slicing
draft-defoy-netslices-3gpp-network-slicing
Network Working Group X. de Foy
Internet-Draft A. Rahman
Intended status: Informational InterDigital Communications, LLC
Expires: April 19, 2018 October 16, 2017
Network Slicing - 3GPP Use Case
draft-defoy-netslices-3gpp-network-slicing-02
Abstract
This document describes work conducted at the 3GPP standard
organization on 5G Network Slicing. Its goal is to provide detailed
use cases, and help better define requirements, for Internet
Protocols supporting Network Slicing.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Background . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. NS Work in 3GPP Prior to 5G Phase 1 . . . . . . . . . . . 3
2. Network Slicing Requirements in 3GPP . . . . . . . . . . . . 3
3. Network Slicing in Logical 5G Architecture in 3GPP . . . . . 4
3.1. Early Work on RAN Slicing . . . . . . . . . . . . . . . . 7
4. Management Aspect of Network Slicing in 3GPP . . . . . . . . 8
5. 5G Virtual Infrastructure Management in 3GPP . . . . . . . . 8
6. Security for Network Slicing in 3GPP . . . . . . . . . . . . 10
7. Analysis and Input to IETF NETSLICES . . . . . . . . . . . . 12
7.1. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1.1. Management Use Case: Create or Terminate a 3GPP
Network Slice Subnet . . . . . . . . . . . . . . . . 12
7.1.2. Management Use Case: Create or Terminate a Complete
3GPP Network Slice . . . . . . . . . . . . . . . . . 13
7.1.3. Management Use Case: Activate or Deactivate a
Complete 3GPP Network Slice . . . . . . . . . . . . . 14
7.1.4. Management Use Case: Update a Complete 3GPP Network
Slice . . . . . . . . . . . . . . . . . . . . . . . . 14
7.1.5. Management Use Case: Monitor Network Slices . . . . . 15
7.1.6. Management Use Case: Slice Management Exposure . . . 15
7.1.7. Management Use Case: Support for Multi-Domain Network
Slice . . . . . . . . . . . . . . . . . . . . . . . . 16
7.1.8. Operational Use Case: Select Network Slices for a
Device . . . . . . . . . . . . . . . . . . . . . . . 16
7.1.9. Operational Use Case: Create or Terminate a PDU
Session . . . . . . . . . . . . . . . . . . . . . . . 16
7.2. Additional Discussion on Security Related Requirements . 17
8. Security Considerations . . . . . . . . . . . . . . . . . . . 18
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18
11. Informative References . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 19
1. Introduction
This document describes work conducted at the 3GPP standard
organization on 5G Network Slicing. Its goal is to provide detailed
use cases, and help better define requirements, for Internet
Protocols supporting Network Slicing.
The concept of Network Slicing (NS) is considered a key mechanism for
5G networks to serve vertical industries with widely different
service needs, in term of latency, reliability, capacity, and domain
specific extra functionalities. It does so by exposing isolated
partitions of network resources and services. The IETF Bar-BoF
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NETSLICES activity studies the need for supporting protocols. In
particular, [I-D.gdmb-netslices-intro-and-ps] defines NS in a broad
context and suggests related problems and work areas. It also
identifies the need to provide use cases such as, for example, ultra-
low latency and massive-connectivity machine communication services.
We propose to review ongoing NS work in 3GPP within the present
document. This constitutes in our view another valid type of use
case, since 3GPP architecture may ultimately use or integrate with NS
solutions defined in IETF.
Sections 2 to 6 aim to represent the current state of NS and related
aspects in 3GPP. We attempted to leave our own analysis out of these
sections and present it into section 7. For simplicity, 3GPP-
specific acronyms are defined in the section they are used, which is
mostly section 3.
1.1. Background
The 3GPP standard organization is in the process of developing 5G
system architecture, which includes NS. In the present document we
will use information collected from 3GPP Release 15 specifications
(as well as preliminary studies from Release 14 when specifications
are not yet available). This release aims to address a more urgent
subset of commercial needs in "5G Phase 1", with expected deployments
in 2020. Work on NS is split between different working and study
groups, reviewed here in separate sections.
1.2. NS Work in 3GPP Prior to 5G Phase 1
While the present document will only focus on NS in 5G Phase 1, an
early form of NS was introduced in Release 13, with the Dedicated
Core Network (DCN) or DECOR feature, where dedicated core network
nodes are forming a DCN serving subscribers or devices with a certain
"usage type" (e.g. machine-to-machine or enterprise). In the Release
14 eDECOR feature, the DCN selection mechanism was extended to be
assisted by the device, which can now send its usage type to the RAN.
This is specified in [_3GPP.23.401]. Deployments are expected in
2017 and 2018.
2. Network Slicing Requirements in 3GPP
NS requirements are included in [_3GPP.22.261]. There are
requirements related to:
o Provisioning: create/modify/delete Network Slices, provision
network functions to be used in Network Slices, define network
services and capabilities supported by a network slice.
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o Managing association to slices: configure association of devices
and services to Network Slices, move/remove user between/from
slices.
o Interoperating: support roaming and non-roaming using the same
home slice, support devices simultaneously connected to multiple
slices.
o Supporting performance and isolation: support dynamic slice
elasticity, ensure performance isolation during normal and elastic
slice operation and during slice creation or deletion, enable
operators to differentiate performance and functionalities between
slices.
3. Network Slicing in Logical 5G Architecture in 3GPP
5G network architecture is entering its normative stage in 2017 with
a "5G System - Phase 1" Release 15 work item, which is in the process
of producing two technical specifications: 23.501 "System
Architecture for the 5G System" and 23.502 "Procedures for the 5G
System". At this early stage, though, we will still need to refer to
the earlier technical report [_3GPP.23.799]. The following text
summarizes what has been agreed about NS (refer to section 8.1 of
that report for more details).
A Network Slice is a complete logical network including Radio Access
Network (RAN) and Core Network (CN). It provides telecommunication
services and network capabilities, which may vary (or not) from slice
to slice. Distinct RAN and Core Network Slices will exist. A device
may access multiple Network Slices simultaneously through a single
RAN.
The device may provide Network Slice Selection Assistance Information
(NSSAI) parameters to the network to help it select a RAN and a core
network part of a slice instance for the device. A single NSSAI may
lead to the selection of several slices. The network may also use
device capabilities, subscription information and local operator
policies to do the selection.
A NSSAI is a collection of smaller components, Session Management
NSSAIs (SM-NSSAI), which each include a Slice Service Type (SST) and
possibly a Slice Differentiator (SD). Slice service type refers to
an expected network behavior in terms of features and services (e.g.
specialized for broadband or massive IoT), while the slice
differentiator can help selecting among several Network Slice
instances of the same type, e.g. to isolate traffic related to
different services into different slices.
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A PDU session is a 5G concept for an association between the device
and a data network, which can be IP, Ethernet or Unstructured (i.e.
transparent to the 5G system). The device will associate an
application with one out of multiple parallel PDU sessions, each PDU
session correspond to one core Network Slice and one RAN slice.
Different PDU sessions may belong to different slices. More
precisely, an application will be associated with a SM-NSSAI (as
mentioned above, this includes a slice service type and may also
include a slice differentiator), and data for this application will
be routed to a PDU session associated to this SM-NSSAI.
Part of the control plane, the Common Control Network Function
(CCNF), is common to all or several slices. It includes the Access
and mobility Management Function (AMF) as well as the Network Slice
Selection Function (NSSF), which is in charge of selecting core
Network Slice instances. Besides those shared functions, different
Network Slices may also have dedicated control plane functions such
as the Session Management Function (SMF), which manages PDU sessions.
User plane functions are dedicated to each slice. The RAN selects a
CCNF for a new PDU session. CCNF may initiate the redirection of
service for a device towards another CCNF, initially at session
setup, or later on.
In figures 1 and 2 we attempt to represent the use of NS in 3GPP
logical architecture (those figures are our interpretation and are
not directly adapted from the report). Figure 1 represents the role
of NSSAI in network selection. Figure 2 represents the major network
functions and interfaces in the context of RAN and Core Network
Slicing. The terms used in these diagrams were introduced earlier.
System description and diagrams in section 4 of [_3GPP.23.501] can
provide additional context.
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+-------+
| |
|Device |
| |
RAN uses NSSAI +---+---+
to select CCNF |
\ |(NSSAI)
\ |
+---+---+
| +-------------+
CCNF uses NSSAI | RAN +---------+ |
to select slice | | | |
or redirect to +---+---+ | |
another CCNF | | |
\ |(NSSAI) | |
\ | | |
+-------+--------+ | |
| Common Control | | |
| Plane Network | | |
| Functions | | |
| (CCNF) | | |
+-----+----+-----+ | |
| | | |
| | | |
| | | |
+---------|----+----------|---+-------+
| | | |
+------------|---------------|-------+ |
| +---------++ +-----+----+ | |
| | | | | | |
| | +------+ | | +------+ | | |
| | | | | | | | | | |
| | |CP NF1| | | |UP NF1| | | |
| | | | | | | | | | |
| | +------+ | | +------+ | | |
| | ... | | ... | | |
| | | | | | |
| | +------+ | | +------+ | | |
| | | | | | | | | | |
| | |CP NFn| | | |UP NFn| | | |
| | | | | | | | | | |
| | +------+ | | +------+ | | |
| | | | | +---+
| +----------+ +----------+ |
+------------------------------------+
Core Network Slice Instances
Figure 1: Network Slice Selection in 3GPP architecture
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CCNF Network Slice Instance
+-----------------+---------------------+
| | |
| | |
| +--------+ | +--------+ |
| | Control| | | Control| |
+--------+ Plane +----------+ Plane | |
| | | AMF... | | | SMF... | |
| | +--------+ | +----+---+ |
| | | | |
| | | | |
| | | | |
+---+--+ +-----------------+ | |
|Device| | | | |
+---+--+ | | | |
| | | | |
| | +--------+ | +------+-----+ |
| | | | | | User Plane | | +---------------+
+--------+ RAN +--------+ Functions +------+Data Network or|
| | | | | | | | The Internet |
| +--------+ | +------------+ | +---------------+
| | |
| | |
+-----------------+---------------------+
RAN Slice
Figure 2: Network Slices in 3GPP architecture
3.1. Early Work on RAN Slicing
In line with the logical architecture described above, early work on
RAN slicing is being conducted as part of the larger Release 14
"Study on New Radio Access Technology". Key principles are likely to
include the following, extracted from [_3GPP.38.801]:
1. RAN will support differentiated handling of traffic between pre-
configured, isolated RAN slices. How to perform this is left to
implementation.
2. Selection of the RAN slice will be based on IDs (which should be
the slice service type and slice differentiator defined above)
provided by the device or core network.
3. A RAN slice may or may not be available at a given location.
4. RAN will select the core network slice.
5. QoS differentiation within a RAN slice will be supported as well.
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4. Management Aspect of Network Slicing in 3GPP
3GPP is developing a Release 14 "Study on management and
orchestration of NS for next generation network" technical report
[_3GPP.28.801], which defines an information model where the Network
Slice as well as physical and virtualized network functions belong to
the network operator domain, while the virtualized resources belong
to another domain operated by a virtualization infrastructure service
provider.
The concept of "Network Slice Subnet" is used in the model, as
defined originally in [NGMN_Network_Slicing]. Network Slice Subnet
instances are comprised of physical and virtual resources, have a
life cycle independent from Network Slices they belong to, can be
shared between several Network Slices and may be associated with
other Network Slice Subnet instances.
Multiple management use cases are described, ranging from creating
and monitoring a slice instance to configuring its SLA policy,
capacity and roaming support. It is also expected that some level of
slice management will be exposed to customers, and that operators
will have the possibility to create end-to-end Network Slices
involving multiple operators' networks.
Key issues are identified, including creating a slice across multiple
administrative domains, sharing a Network Slice between multiple
services, moving towards a more autonomous management, as well as
additional management specific key issues.
Finally, the life cycle of a slice is defined over 4 phases:
preparation phase including design and pre-provisioning, an
"instantiation, configuration and activation" phase, a run-time phase
including supervision and reporting, as well as upgrade,
reconfiguration and scaling, and a decommissioning phase.
5. 5G Virtual Infrastructure Management in 3GPP
To support the logical architecture defined earlier, some aspects of
virtualization infrastructure management are also being standardized
by 3GPP, through the activity "Management of mobile networks that
include virtualized network functions". This includes 5 work tasks,
the first of which deals with concept, architecture and requirements
[_3GPP.28.500], and 4 additional specialized work tasks on
configuration, fault, lifecycle and performance management, are in
the process of creating more detailed technical specification
documents.
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The new 5G management system is tied to NFV-MANO, as defined by ETSI.
Its system architecture is described in [_3GPP.28.500] and
represented in Figure 3 (directly adapted from TS28.500). It defines
interconnections between the 3GPP management system and the NFV-MANO
system. NFV-MANO has the responsibility to manage NFV Infrastructure
(NFVI) and VNF lifecycle, and to report performance data, fault and
VNF instance information to 3GPP management system.
+--------------------------------------------+ +-------------+
| +----------------------------------+OSS/BSS| | NFV |(3)
| | NM | | (1)|Orchestrator +--+
| +--+--------------+--------------+-+ +----+ (NFVO) | |
+----|--------------|--------------|---------+ +-------------+ |
| | | |(2) |
| Itf-N | Itf-N | Itf-N | |
| | | +------+------+ |
| | | | | |
| +---------+------------+ | | | |
| |DM +----------------+ | | (5) | | |
| | | EM +------------------+ VNF | |
| | +-+--------+-----+ | | (5) | Manager | |
| +-----|--------|-------+ | +----------+ (VNFM) | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
| | | | | | | |
+-+-+--+ | | +--+---++--+ (5) | | |
| | EM | | | | EM | +------+ | |
| +----+ | | +-------+ | +------+------+ |
| | | | | VNF | | |
| | +----++ +----+----+ +----+-----+ |(4) |
| | | | | | | | |
| | | | | VNF | | | |
| | | | | | |(7) | |
| | | | +-----+---+ | +------+------+ |
| | | | |(7) | | | |
| NE | | NE | +-----+----------+----+ | Virtualized | |
| (PNF)| |(PNF)| | | | Infrastruct.| |
| | | | | NFV Infrastructure | (6) | Manager +--+
| | | | | (NFVI) +-------+ (VIM) |
| | | | | | | |
+------+ +-----+ +---------------------+ +-------------+
Figure 3: 3GPP Network Management Architecture
The major building blocks on the left are from pre-existing 3GPP
architecture and on the right are from ETSI NFV architecture. Itf-N
is the traditional 3GPP management interface between the network
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manager and domain and element managers, some of which will now be
collocated with VNFs. Other interfaces identified in the diagram are
defined as part of the NFV architecture and described in published
NFV specifications (which themselves do not make mention of NS).
o (1) Os-Ma-nfvo enables managing Network Service Descriptors (NSD),
network service lifecycle, performance, faults and VNF packages.
The NSD information model is specified by ETSI NFV as well. It
enables describing network connectivity topology graphs where VNFs
are connected together through virtual links. An NSD also
includes VNF descriptors, which include memory and CPU
requirements, a link to a software image, initial setup scripts,
etc.
o (2) Or-Vnfm includes package management, VNF lifecycle/fault/
configuration management, virtualized resources management (in
indirect mode as seen below), and relays notifications from the
VNF or EM.
o (3) Or-Vi and (4) Vi-Vnfm are the northbound interface of the
Virtual Infrastructure Manager (VIM). The orchestrator can
basically use a direct interface to VIM, or indirectly go through
the VNF manager over Or-Vnfm. The orchestrator can add software
images, create/update/terminate virtualized compute/network/
storage resources allocations, manage resource capacity, manage
network virtual paths, run and query performance collection jobs,
set quotas. Location/affinity constraints can be applied when
creating resources.
o (5) Ve-Vnfm is used both between VNFM and EM and between VNFM and
VNFs. It includes lifecycle, performance, fault and configuration
management, as well as notifications from the EM that VNFM can
subscribe to.
o (6) Nf-Vi is for assignment of virtualized resources, hardware
resource configuration and state information exchange.
o (7) Vn-Nf represents the execution environment provided to the
VNF.
6. Security for Network Slicing in 3GPP
The present section on NS security is based on the "Study on
Architecture and Security for Next Generation System", a Release 14
study item. Its related technical report is [_3GPP.33.899], and
covers, among other areas, a NS security area dealing with service
access, network function sharing and isolation. Multiple key issues
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are summarized here (refer to [_3GPP.33.899] section 5.8 for more
details):
1. Isolation requirements, especially performance isolation, ask for
data plane actions on one slice to have no influence on other
Network Slices and for control plane actions (e.g.
creation/update/deletion) to have little influence on other
slices. Lack of isolation can enable DoS attacks from one slice
to another, especially since some functions can be shared between
slices. Moreover, a device can access multiple Network Slices,
which increases the possibility for leakage/breach type of issues
between Network Slices, both from the device and the service
side.
2. Different Network Slices may need to implement different security
policies, e.g. in term of authentication requirements (IoT vs.
mobile broadband user). Authentication may be centralized and/or
per-slice.
3. Security and privacy of devices' access to Network Slices is also
a concern. It may be possible to forge slice selection
information for a device. Slice selection information sent over
the access network can also lead to confidentiality issues. The
proposed key hierarchy supports having different keys for
different slices. How to enable security isolation of a common
control plane between different Network Slices is not addressed
at this point.
4. Security of sensitive shared network elements such as the HSS
(which holds customers' profiles) is identified as a key issue as
well.
5. Slice management functions should be secured, since an attacker
may use them, e.g. to delete a slice. Slice management
capabilities exposed through APIs for 3rd parties are especially
vulnerable.
6. Security on inter-slice communications is an issue in several
scenarios, for example when multiple Network Slices share control
plane functions, and when a RAN slice and a Core Network slice
are interconnected to form a complete slice. Each slice is
considered a different trusted domain.
7. A range of potential issues related to virtualization are yet to
be explored further, though it is not clear if they are in the
scope of 3GPP. Issues include for example isolation between VNFs
hosted by the same hypervisor, authentication between VNFs,
performance isolation between VNFs.
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7. Analysis and Input to IETF NETSLICES
Earlier sections of this document summarized our understanding of 5G
architecture and requirements for NS, as defined by 3GPP, in their
current state. Our goal in these sections was to provide context to
IETF NETSLICES, since a protocol or framework defined by IETF for NS
may be used to implement or interoperate with 3GPP-compliant 5G
systems. In reference to Figure 3, the scope of IETF involvement
with NS could be within NFV Infrastructure, as well as some aspects
of the control plane on the right-hand side of the figure. The
concept of "Network Slice Subnet" discussed in section 4 may be
useful as a building block, e.g. a single-domain and composable
service chain that is used to assemble a network slice. Defining the
interfaces of such a component could help focusing on sharing between
Network Slices and extending Network Slices across domains.
We will now attempt to derive high level use cases and requirements
from this work. The goal is to serve as 3GPP-focused input to future
efforts to gather use cases and requirements for IETF NETSLICES.
7.1. Use Cases
The following 3GPP-focused use cases for NS are derived from the
reviewed 3GPP specifications and reports. Especially, management
related use cases are derived from [_3GPP.28.801] and operational use
cases are derived from [_3GPP.23.501].
The goal here is to describe the use cases at high level only, with
the understanding that the IETF NETSLICES group may choose to define
selected use cases further if needed.
In the following text we will use the terms "Complete 3GPP Network
Slice" to refer to a "Network Slice Instance" used by 3GPP, and "3GPP
Network Slice Subnet" to refer to "Network Slice Subnet Instance".
Moreover, we consider that the (IETF) Network Slice concept is a
generalization of the "3GPP Network Slice Subnet", i.e. the "3GPP
Network Slice Subnet" is a particular Network Slice which happens to
be part of a 3GPP network.
7.1.1. Management Use Case: Create or Terminate a 3GPP Network Slice
Subnet
The operator's OSS/BSS provides a description of a Network Slice to
the Orchestrator, which, through the Virtual Infrastructure Manager,
configures compute and network elements to create a Network Slice
holding a specific set of interconnected virtual and/or physical
network functions. User plane Network Slices include one or more
bidirectional paths between network functions (i.e. one or more
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service function chains). Control plane Network Slices can either
include a set of service function chains or alternatively can
interconnect multiple network functions in a virtual network. In all
cases, Network Slices are defined with a variable set of reserved
KPIs, including minimum and maximum throughput, delay, packet loss,
etc.
Potential requirements:
o A Network Slice can be a service function chain or a virtual
network
o A Network Slice can be associated with a variable set of resource
reservation with regards to KPIs such as minimum and maximum
throughput, delay, packet loss, etc.
7.1.2. Management Use Case: Create or Terminate a Complete 3GPP Network
Slice
The operator creates a Complete 3GPP Network Slice by composing
together smaller Network Slices together, which the highest level
Network Slices being: a RAN Network Slice, a Core Network slice
holding user plane (UPF) and control plane (SMF) network functions,
as well common Core Network functions. Those common core network
functions (AMF, PCF, etc.) may be placed in multiple Network Slices
since they can have different scaling properties.
The Common CN Function Network Slices (including AMF) may be shared
or dedicated to a given SMF. In the shared case, there will be
traffic flows terminated within a dedicated CN slice (e.g. SMF) and
the shared function. RAN Slices may similarly be shared or
dedicated. In the shared case, each user traffic flow passing
through a shared RAN slice will then pass through one out of multiple
dedicated CN slices interconnected with this shared RAN Slice. In
both (RAN and CN) shared cases, there should be reserved resources
within the shared Network Slice, to ensure that the whole flow has
reserved resources.
NS is not a required feature in 3GPP, especially not all Core Network
functions are required to belong to a slice with a specified level of
service. In some cases, common network functions like AMF and PCF
may be implemented outside of a Network Slice, or, equivalently, in a
Network Slice with no specified QoS.
A wide variation of cases, associating "n" Network Slices with "m"
network services or applications involving "p" end devices, is
supported. For example: a single slice instance could be associated
with multiple IoT applications, each connected to multiple devices.
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In another example, an application may split its end users in 2
service categories with different SLAs, using different Network Slice
instances.
Potential requirements:
o Network Slices can be composed of smaller Network Slices which can
be dedicated or shared.
o Functions in Network Slices can interact with network functions
outside of a Network Slice.
7.1.3. Management Use Case: Activate or Deactivate a Complete 3GPP
Network Slice
Each Network Slice can be created in a deactivated state, and can be
later switched between activated and deactivated state. This can
provide multiple advantages, e.g. speeding up procedures, and
enabling using a pool of unused resources. Activation or
deactivation of a Complete 3GPP Network Slice can then be
orchestrated as the activation (resp. deactivation) of individual
Network Slices, possibly in a given order.
Potential requirement:
o A slice can be created deactivated, and can be switched between
activated and deactivated state.
7.1.4. Management Use Case: Update a Complete 3GPP Network Slice
The operator can modify the configuration (e.g. network or compute
capacity or capability) of one of the Network Slices composing the
Complete 3GPP Network Slice, while it is in use. Example of such
operations include:
o Increase the capacity of NFs
o Update the configuration of NFs
o Add, replace or remove a NFs
o Add, replace or remove a Network Slice
Some operations affecting a shared slice may not be possible without
affecting other Network Slices, and may be replaced by other
operations: for example, instead of changing the configuration of a
shared AMF to accommodate the needs of a SMF, another Network Slice
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with an AMF may be created or activated, and replace the original
AMF's slice for this SMF.
Potential requirement:
o Ability to add, replace, remove NFs, and Network Slices without
affecting service, assuming that the network service's design
enables this.
7.1.5. Management Use Case: Monitor Network Slices
The 3GPP management system monitors performance of individual Network
Slice level and coalesce performance data for the whole Complete 3GPP
Network Slice. Individual Network Slice level performance data is
also useful to decide to scale up or down services within those
slices. Performance data (or events) includes user and control
traffic load data. It can also include QoS/SLA data, e.g. indicating
whether services were provided at expected QoS/SLA level. Alarms
notifications can be individually enabled. Events and alarms from a
shared Network Slice contain enough information to be attributed by
the 3GPP management system to one of the Complete 3GPP Network Slices
that contain this shared Network Slice.
Potential requirements:
o Performance monitoring (measure of KPIs and alarms) occurs at
Network Slice level.
o Performance monitoring should be able to identify flows which are
shared with other Network Slices, and enable matching performance
data with those flows and Network Slices.
7.1.6. Management Use Case: Slice Management Exposure
3GPP networks may in some cases expose partial 3GPP Network Slice
management to third party Communication Service Providers (CSP), who
may in turn consume this service or provide it to their own
customers. Using this management interface a third party can request
the creation of a Complete 3GPP Network Slice using specifications of
NFs, isolation, security, performance requirements (such as traffic
demand requirements for the coverage areas, QoS for service).
When a 3GPP operator exposes management data (e.g. fault management
data, performance data) about a Complete 3GPP Network Slice shared by
multiple customers of a CSP, exposed management data of each customer
is isolated from each other.
Potential requirement:
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o Management data should enable identification of individual flows
in such a way that it can be match to different customer groups.
7.1.7. Management Use Case: Support for Multi-Domain Network Slice
To support roaming, a 3GPP operator configures one or more Complete
3GPP Network Slice to be selected to support roaming subscribers, to
act as visited Complete 3GPP Network Slices. Operators configure the
interconnection of a home Complete 3GPP Network Slice in one domain
and a visited Complete 3GPP Network Slice in the other domain.
Performance data is sent from the visited domain to the control
function in the home domain.
Potential requirement:
o Support secure inter-domain interconnection for exchanging user
plan traffic and performance data.
7.1.8. Operational Use Case: Select Network Slices for a Device
A subscriber's device initially connects to the network. It sends,
over a signaling path through the RAN, a message including a Network
Slice Selection Assistance Information (NSSAI), which is a set of one
or more tuples (slice type, slice differentiator). The RAN selects
an appropriate AMF and forwards the NSSAI to this function. The AMF
determines (possibly with the help of a Network Slice Selection
Function) the set of allowed (slice type, slice differentiator) for
this subscriber, using the NSSAI, device capabilities, subscriber's
profile, and operator policy. There is no physical resource
reservation at this stage.
Slice selection in this context is a preparation of control plane
functions and may probably be considered out of scope for a general
NS framework. Therefore no potential requirements are derived from
it.
7.1.9. Operational Use Case: Create or Terminate a PDU Session
At some point, the device needs a PDU session to transport flows for
a specific application. It sends, over a signaling path through the
RAN, a PDU session establishment request to the AMF, typically
including a tuple (slice type, slice differentiator) and a data
network name. If no such tuple is provided, the AMF will determine a
default one to use. The AMF will then determine which SMF (i.e.
which Core Network Slice) to use, taking into consideration: the
tuple (slice type, slice differentiator), data network name,
subscription information, local operator policies and load conditions
of the candidate SMFs. If this is a home-routed roaming case, the
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AMF will select a SMF in the visited network and another SMF in the
home network. The SMF selects the user plane function (UPF) that
will handle the traffic, and transmits configuration information to
this UPF (e.g. packet detection, QoS enforcement and reporting rules
to be installed on the UPF for this PDU Session).
Potential requirement:
o A network slice control API should enable installing new flows and
associated reporting rules.
7.2. Additional Discussion on Security Related Requirements
In addition to potential requirements listed along with the use cases
above, here is a list of additional discussion points related to
security requirements and not directly described in a use case at
this point:
1. 3GPP architecture demonstrates a requirement for authenticating
users of Network Slice resources (which may or may not be within
the scope of an IETF framework). There is however a need for
separate per-slice security policies, e.g. having different
authentication requirements between IoT and broadband.
2. Interoperation between Network Slices is a major risk factor on
isolation and can occur in various scenarios:
* "Interoperation for extension" when data and control plane are
interconnected for extending a slice between RAN and CN, or
between visitor and home networks in a roaming scenario.
* "Interoperation through network function sharing" occurs in
3GPP when some control planes functions are performed by
common functions.
* "Interoperation through end points" can occur on user devices
connected to multiple Network Slices, or on an application
server side interacting with clients over different slices.
3. There is a strict requirement for security and performance
isolation from data plane and control plane actions between
slices. Should Network Slices be allowed to tap into currently
unused resource capacity? There is a possible tradeoff here
between performance/network efficiency and isolation, since in
this case, through its normal operation, a slice may influence
another slice by denying it this extra capacity.
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8. Security Considerations
Security aspects of NS in 3GPP are covered in section 6.
9. IANA Considerations
This document requests no IANA actions.
10. Acknowledgements
The authors would like to thank Ulises Olvera-Hernandez for his
contribution and comments.
11. Informative References
[_3GPP.22.261]
3GPP, "Service requirements for next generation new
services and markets", 3GPP TS 22.261 1.1.0, February
2017, <http://www.3gpp.org/ftp/Specs/html-info/22261.htm>.
[_3GPP.23.401]
3GPP, "General Packet Radio Service (GPRS) enhancements
for Evolved Universal Terrestrial Radio Access Network
(E-UTRAN) access", 3GPP TS 23.401 14.2.0, 12 2016,
<http://www.3gpp.org/ftp/Specs/html-info/23401.htm>.
[_3GPP.23.501]
3GPP, "System Architecture for the 5G System", 3GPP
TS 23.501 0.2.0, 2 2017,
<http://www.3gpp.org/ftp/Specs/html-info/23501.htm>.
[_3GPP.23.799]
3GPP, "Study on Architecture for Next Generation System",
3GPP TR 23.799 14.0.0, 12 2016,
<http://www.3gpp.org/ftp/Specs/html-info/23799.htm>.
[_3GPP.28.500]
3GPP, "Telecommunication management; Management concept,
architecture and requirements for mobile networks that
include virtualized network functions", 3GPP TS 28.500
1.3.0, 11 2016,
<http://www.3gpp.org/ftp/Specs/html-info/28500.htm>.
[_3GPP.28.801]
3GPP, "Study on management and orchestration of network
slicing for next generation network", 3GPP TR 28.801
0.4.0, 1 2017,
<http://www.3gpp.org/ftp/Specs/html-info/28801.htm>.
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[_3GPP.33.899]
3GPP, "Study on the security aspects of the next
generation system", 3GPP TR 33.899 0.6.0, 11 2016,
<http://www.3gpp.org/ftp/Specs/html-info/33899.htm>.
[_3GPP.38.801]
3GPP, "Study on the security aspects of the next
generation system", 3GPP TR 38.801 1.0.0, 12 2016,
<http://www.3gpp.org/ftp/Specs/html-info/38801.htm>.
[I-D.gdmb-netslices-intro-and-ps]
Galis, A., Dong, J., kiran.makhijani@huawei.com, k.,
Bryant, S., Boucadair, M., and P. Martinez-Julia, "Network
Slicing - Introductory Document and Revised Problem
Statement", draft-gdmb-netslices-intro-and-ps-02 (work in
progress), February 2017.
[NGMN_Network_Slicing]
NGMN, "Description of Network Slicing Concept", 1 2016,
<https://www.ngmn.org/uploads/
media/160113_Network_Slicing_v1_0.pdf>.
Authors' Addresses
Xavier de Foy
InterDigital Communications, LLC
Montreal
Canada
Email: Xavier.Defoy@InterDigital.com
Akbar Rahman
InterDigital Communications, LLC
Montreal
Canada
Email: Akbar.Rahman@InterDigital.com
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