wang-nfvrg-network-slice-diverse-standards-00.txt

Internet DRAFT - draft-wang-nfvrg-network-slice-diverse-standards

draft-wang-nfvrg-network-slice-diverse-standards

Last Version:	draft-wang-nfvrg-network-slice-diverse-standards-00.txt	Tracker Entry
Date:	`03-Jul-2018`
Disposition:	expired

nfvrg L. Wang
Internet-Draft L. Geng
Intended status: Informational China Mobile
Expires: January 3, 2019 July 02, 2018

Review of Network Slicing Research in Diverse Standards
draft-wang-nfvrg-network-slice-diverse-standards-00

Abstract

As one of the significant technology in 5G, there are diverse
industry communities and standard organizations dedicated in a
research of Network Slicing, such as IETF, 3GPP, GSMA, ETSI, etc..
These organizations and communities not only standardize network
slicing architecture, management, requirements and so on, but also
individually focus on specifying network slicing in their own ways,
offering diverse specifications of it. Aiming at research on a
overall review of network slicing standard, this document discuss
diverse standards in various organizations and communities,
furthermore, analyzing the emphasis and difference between them.

Status of This Memo

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This Internet-Draft will expire on January 3, 2019.

This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents

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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Overview of Network Slicing Standard Progress . . . . . . . . 3
4. Detailed Diverse Network Slicing Standards . . . . . . . . . 4
4.1. IETF . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4.1.1. Network Slicing in IETF . . . . . . . . . . . . . . . 4
4.1.2. Information Model . . . . . . . . . . . . . . . . . . 5
4.2. 3GPP . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2.1. Network Slicing in 5G . . . . . . . . . . . . . . . . 6
4.2.2. Network Slice Operation Procedure . . . . . . . . . . 7
4.3. ETSI . . . . . . . . . . . . . . . . . . . . . . . . . . 9
4.4. GSMA . . . . . . . . . . . . . . . . . . . . . . . . . . 9
5. Conclusion:Different Understanding and Emphasis of Each
Organizations . . . . . . . . . . . . . . . . . . . . . . . . 9
6. Informative References . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11

1. Introduction

With the rapid development of 5G technology research and successful
emergence of 5G market, network slicing is becoming one of
significant technologies of 5G. The mechanism of network slicing is
that divide common physical network infrastructure into diverse
isolated virtual network resources to meet the high level demands
from different vertical industry. With network slicing, providers
are able to offer customized service to users in terms of bandwidth,
latency, security and so on. Network slicing mechanism enables 5G to
integrate diverse network resources and multi-domain technologies, to
meet various demands from vertical industry, offering the best-effort
network service. For instance, to achieve both determined latency
and security requirements from some industry services, network
slicing is likely to apply TSN[tsn] and blockchain technologies to
satisfy the requirement. Meanwhile, network resources such as high
bandwidth and dedicated network tunnel can be supplied here to meet
the demands as well which are all integrate in this network slice.

As the key feature of 5G, the concept of network slicing is discussed
in related standard organizations and communities. 3GPP release
network slicing standard of architecture in specification
[TR23.501]and management&orchestration in specification [TR28.801] .

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3GPP also specify requirement, use cases and other related features
of network slicing in different work groups. Also, being so
important to network technology progress, network slicing has gotten
a lot of attention and heated discussion in IETF. Several drafts are
released and discussed in netslicing and COMS mailing list which will
be talked in the following sections. Besides, there are other
organizations are doing research in network slicing, such as European
Telecommunications Standards Institute (ETSI), Broadband Forum (BBF),
GSM Association (GSMA), etc. Each of them makes diverse definition
and concern different areas of network slicing definition.

It shows that network slicing has been defined by multiple Standards
Definition Organizations (SDOs) and communities. However, as a
diversity of mission of each, the meaning and understanding of the
network slicing concept are different from each other and there is no
common definition. In the following part of documents, an overview
of network slicing research aspect will be discussed. Furthermore,
the emphasis and difference between each organization is analyzed as
well. This is aimed at giving out clear viewpoints of network
slicing understanding from these organizations.

2. Terminology

The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].

PLMN, Public Land Mobile Network, is a network that is established
and operated by providers for the specific purpose of providing land
mobile telecommunications services to the public.

NSSAI, Network Slice Selection Assistance Information. NSSAI
provided by the Serving PLMN during a Registration procedure,
indicating the S-NSSAIs values the UE could use in the Serving PLMN
for the current registration area.

S-NSSAI, Single Network Slice Selection Assistance Information.
S-NSSAI identify a network slice.

3. Overview of Network Slicing Standard Progress

In this section, an overview of network slicing standard progress
will be given out.

IETF Network slicing is discussed in terms of specification of
terminology, architecture[draft-geng-coms-architecture-02], use
cases[draft-qiang-coms-use-cases-00], problem statement and other
aspects related to network slicing. To map the gap between

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technology-agnostic network slicing service requirements and
specific implementation technologies, a technology independent
information model is created. Furthermore, aiming at converging
bottom-up and top-down approaches on a technology-independent
common management plane, COMS (Common Operation and Management on
network Slices) is defined and described
here[draft-geng-coms-architecture-02].

3GPP Acknowledging network slicing as significant component of 5G
process, 3GPP dedicated in making a thorough specification of
network slicing concept since the very early time when they
started considering 5G technology. Network slicing is specified
in SA1 (requirements), SA2 (architecture), SA3 (security) and SA5
(network management) respectively, in which architecture and
management will mainly be described the next paragraph.

ETSI ETSI analyses network slicing use cases defined in other SDOs
and industry fora in Report on Network Slicing Support with ETSI
NFV Architecture Framework [ETSI_GR_NFV-EVE], and give the
description that how to map the use cases to the NFV architecture
and concepts.

GSMA GSMA give the Concept of network slicing from a business way
and indicate that how network slicing can serve and support 5G
network in its report [GSMA-An-Introduction-to-Network-Slicing]

4. Detailed Diverse Network Slicing Standards

4.1. IETF

4.1.1. Network Slicing in IETF

In [draft-geng-netslices-architecture-02] , end to end network slice
is defined as a cross-domain network slice which may consist of
access network, transport network, (mobile) core network. The
concept here of network slice is expanded to a wider area and
comprises of several functional components. Driven by the multiple
requirements from users, network slice instance may include several
service components that each of which may require a set of network
resources and attributes in form of a network slice.

Network Slicing Management and Orchestration is comprised of:

Template Management: A complete description of the structure,
configuration and the plans/work flows for how to instantiate and
control the network slice instance during its life cycle.

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NS Repository: A policy to describe how user select network slice
or how multi-slice instance associated with one network slice.

Life cycle management and monitoring : Network slicing and slice
instance must be full life cycle managed and monitored.

E2E Orchestration: E2E Slices Orchestration and its functionality
which can be a)Coordinating a number of interrelated resources,
b)Autonomically control of slice life cycle management,
c)Autonomically coordinate and trigger of slice elasticity and
placement of logical resources in slices, d)Coordinates and (re)-
configure logical resources.

Domain Orchestration: In heterogeneous environment, network
slicing is expected to orchestrate multiple domain technologies
and resources to gain the most effective, dynamic and automatic
functions.

NS Manager: Manager manages all access permissions and all
interaction between a Network Slice and external functions which
are specific for each network slice instance.

Resource Registration: Responsible for the management of exposed
capability of the network infrastructure.

Under network slicing management and orchestration, the resource
management which can be physical, logical and virtual resources will
be mapped to the requirements and Capabilities users demands to
create the related network slice instance. The Capabilities of
network slicing includes reclusiveness, protection, elasticity,
extensibility, safety and isolation.

4.1.2. Information Model

However, sometimes customers, being not able to know or not familiar
with the underlying networking resources and technologies, expect a
technology-agnostic interface. A information model here is in demand
to fill the gap between technology-agnostic network slicing service
requirements and specific implementation technologies.

The information model for network slicing here is required to offer
the capability that describe the entities that compose a network
slice, their functions and the mechanism how they serve the
corresponding network slice. The information model provide the
connectivity of undying technologies from providers and customers

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requirements, and gives out a clear and complete informal diagrams of
network slices entities and technologies in different domains.

4.2. 3GPP

Here we only disscuss the architecture and management of Network
slicing in 3GPP, which are mostly related to [TR23.501] and
[TR28.801]

4.2.1. Network Slicing in 5G

In 3GPP [TR23.501], a network slice is defined as an end to end
logical communication network, within a Public Land Mobile Network
(PLMN) and includes the Core Network (CN) Control Plane, User Plane
Network Functions and 5G Access Network (AN).

A singal UE(User Equipment) may be served by multiple slices
simultaneously through a single RAN. Correspondingly, network slices
may vary for supported features and network functions optimisations
because of different S-NSSAIs with different Slice/Service Types. So
provider may select to deploy multiple network slices, but offering
same service feature, to serve a group of UEs.

S-NSSAI, delivering identification and selection information of a
network slice, is comprised of a Slice/Service type (SST) which
refers to the expected Network Slice behaviour in terms of features
and services and a Slice Differentiator (SD) which is optional
information that complements the Slice/Service type(s) to
differentiate amongst multiple Network Slices of the same Slice/
Service type. Network Slice instance can be associated with one or
more S-NSSAIs, and an S-NSSAI can be associated with one or more
Network Slice instances.SST value represents 3 service types that are
eMBB (enhanced Mobile Broadband), URLLC (ultra- Reliable Low Latency
Communications) and MIoT (Massive IoT) respectively.

Figure 1 is a network slicing architecture in 5G. For one network
slice instance, UE selects a network slice by requesting a S-NSSAI
via RAN (This will be given details in next section), and core
network responds to allocate the corresponding slice.

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Network Slice +----------------------------------------------------------------------+
Instance | +-----+ +-----+ +----------|CORE|--------------+ |
+------------+ | | | | | Transmission | +----+ +----+ +----+ +----+ | |
| eMBB +--------------+ |UE +---(R)AN +-------------------+ |UPF | |AMF | |SMF | |PCF | | |slice1
+------------+ +--+ | | | | Bearing Network | | | | | | | | |... |
| | | | | | | +----+ +----+ +----+ +----+ | |
+------------+ | | +-----+ +-----+ +------------------------------+ |
| URLLC +-----------+ ++--------+--------------------------+----------------------------------+
+------------+ +--+ | | | | | | |
| | +-----+ +-----+ +-------------------------+ | slice2
+-------------+ | | |
| MIoT +--------+ ++------+--+-----+------------------+------------------------+-----+---+
+-------------+ | | | | | | | |
| +------+ +-----+ +------------------------+ |slice3
| |
+---------------------------------------------------------------------+

Figure 1

4.2.2. Network Slice Operation Procedure

The Network slicing operation procedure starts from UE registration,
in which the selection of Network Slice instances for a UE is
triggered by the first contacted Access and Mobility Management
Function (AMF). After AMF selected by the AN receives the UE
Registration request, UE signals a requested NSSAI to AMF, and AMF is
expected to determine whether it can serve the UE by verifying
whether the S-NSSAI(s) in the Requested NSSAI are permitted based on
the Subscribed S-NSSAIs. If this case is permitted, AMF query the
Network Slice Selection Function (NSSF), with Requested NSSAI,
mapping of Requested NSSAI to Configured NSSAI. The NSSF returns to
the current AMF the Allowed NSSAI for the applicable Access Type(s)
and UE, after receiving an Allowed NSSAI from the serving AMF, will
store it.

As the one of the most important goals of network slicing
configuration, the Protocol Data Unit (PDU) Session Establishment in
a Network Slice to a DN allows data transmission in a Network Slice.
The data transmission works after a PDU session to a Data Network is
established in a Network Slice. Each PDU session corresponds to one
core network slice and one RAN slice specifically.Here AMF is common
to network slices serving the UE, but SMF and UPF are specific to
each slice they associated to.

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+---------+
| UE |
+----+----+
NSSAI |
+----+----+
| RAN |
+---------+
|RAN choose AMF with NSSAI
NSSAI |
+--------------------------+-----------------------------+
| AMF queries the NSSF |
| +--------+ with Requested NSSAI--------+ |
| | +-------------------------^ NSSF | |
| | AMF <-------------------------+ | |
| +--------NSSF returns to the +--------+ |
| +-------+Allowed NSSAI |
| | NRF | |
| +-------+ |
+--------------------------+------+----------------------+
| |
| +-------++
+-------------+------------+ |
| | |
| +-----+ +-----+ +-----+ +-++
| | | | | | | | |
| | | | | | | | |
| |SMF | |UPF | | PCF ...| |
| | | | | | | | |
| | | | | | | | |
| | | | | | | | |
| +-----+ +-----+ +-----+ | |
| | |
+---+-------+--------------+ |
| | |
| | |
+------------+------------+
| |
+--+-+ |
|DN1 | |
+----++-+----+
| DN2 |
+------+

Figure 2 Network Slice Operation

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4.3. ETSI

Rather than defining the standard of network slicing as well as other
organizations, ETSI focuses on the mapping of the network slicing to
NFV concept and describe how NFV architecture support it under the
standards of diverse organization such as 3GPP.

Under the 3GPP defination of network slicing, ETSI defines NFV-NS
that represent the virtualized resources for the slice subnet and
their connectivity to physical resources. ETSI also describe Os-Ma-
NFvo interface point that offer the interaction between the 3GPP
slicing management and NFV-MANO, which is also related to a couple of
management determination from NSMF and NSSMF.

4.4. GSMA

In [GSMA-An-Introduction-to-Network-Slicing], GSMA give the Concept
of network slicing from the point of view of business customers that
"Network slicing is the embodiment of the concept of running multiple
logical networks as virtually independent business operations on a
common physical infrastructure in an efficient and economical way."
And they define that customisable network capabilities include data
speed, quality, latency, reliability, security, and services. It is
also mentioned that different operators can share the same network
slice in GSMA description.

5. Conclusion:Different Understanding and Emphasis of Each
Organizations

Based on the above description of network slicing and its entities
from different organizations, it is not hard to find that they
provide a different understanding of network slicing concept and have
their emphasis of research on it:

In 3GPP, network slice is deployed in RAN, UPF and CN for a mobile
network. Network slice instance is created by the cooperation
between RAN and CN, which is more like a customized sliced
function in core network. But the connectivity part, transmission
network between CN and RAN is not sliced.

IETF anticipates to define an broader applied end-to-end network
slicing for not only mobile network, but also other networks forms
which may not includes CN or RAN. Therefore, the transmission
network is considered as part of network slice resource/instance
which can be sliced as well. This may ask for a orchestration of
multiple domain technologies in transmission network and a
information model to expose the relating tech capabilities.

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ETSI mainly focuses on the mapping between NFV function and
network slice based on the network slicing definition from current
organizations, while GSMA define network slicing in a general and
business way.

All of the descriptions from diverse organizations is attempting to
give a comprehensive and typical standard for network slicing.

6. Informative References

[draft-geng-coms-architecture-02]
"COMS Architecture", <https://datatracker.ietf.org/doc/
draft-geng-coms-architecture/>.

[draft-geng-netslices-architecture-02]
"Network Slicing Architecture",
<https://www.ietf.org/archive/id/
draft-geng-netslices-architecture-02.txt>.

[draft-qiang-coms-netslicing-information-model-02]
"Technology Independent Information Model for Network
Slicing", <https://datatracker.ietf.org/doc/
draft-qiang-coms-netslicing-information-model/>.

[draft-qiang-coms-use-cases-00]
"The Use Cases of Common Operation and Management of
Network Slicing", <https://datatracker.ietf.org/doc/
draft-qiang-coms-use-cases/>.

[ETSI_GR_NFV-EVE]
"Report on Network Slicing Support with ETSI NFV
Architecture Framework Disclaimer",
<https://www.etsi.org/deliver/etsi_gr/NFV-
EVE/001_099/012/03.01.01_60/gr_NFV-EVE012v030101p.pdf>.

[GSMA-An-Introduction-to-Network-Slicing]
, <https://www.gsma.com/futurenetworks/wp-
content/uploads/2017/11/
GSMA-An-Introduction-to-Network-Slicing.pdf>.

[I-D.boucadair-connectivity-provisioning-protocol]
Boucadair, M., Jacquenet, C., Zhang, D., and P.
Georgatsos, "Connectivity Provisioning Negotiation
Protocol (CPNP)", draft-boucadair-connectivity-
provisioning-protocol-15 (work in progress), December
2017.

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[RFC2119] "Key words for use in RFCs to Indicate Requirement
Levels".

[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.

[TR23.501]
"System Architecture for the 5G System",
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3144>.

[TR28.801]
"Telecommunication management;Study on management and
orchestration of network slicing for next generation
network",
<https://portal.3gpp.org/desktopmodules/Specifications/
SpecificationDetails.aspx?specificationId=3091>.

[tsn] "Time-Sensitive Networking (TSN) Task Group",
<https://1.ieee802.org/tsn/#Published_TSN_Standards>.

Authors' Addresses

Lei Wang
China Mobile
Beijing 100053
China

Email: jifengyiwl@163.com

Liang Geng
China Mobile
Beijing 100053
China

Email: gengliang@chinamobile.com

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