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E2E Network Slicing - Key 5G technology

: What is it? Why do we need it? How do we implement it?
November 27, 2015 | By Dr. Harrison J. Son and Chris Yoo (tech@netmanias.com)

Before you read this post, we recommend you read the following articles first:

Mobile Network Architecture for 5G Era - New C-RAN Architecture and Distributed 5G Core

5G network as envisioned by KT - Analysis of KT's 5G network architecture

5G and Network Slicing

With 5G being actively discussed everywhere, Network Slicing certainly is one of the most discussed
technologies these days. Network operators like KT, SK Telecom, China Mobile, DT, KDDI and NTT, and
also vendors like Ericsson, Nokia and Huawei are all recognizing it as an ideal network architecture for the
coming 5G era.
This new technology lets operators slice one physical network into multiple, virtual, end-to-end (E2E)
networks, each logically isolated including device, access, transport and core network (like partitioning a
HDD into C and D drives) and dedicated for different types of services with different characteristics and
requirements.
For each network slice, dedicated resources (like resources within virtualized servers, network BW,
QoS, etc.) are guaranteed. As slices are isolated from each other, an error or fault occurred in one slice
does not cause any effect on communication in other slices.

Then, why 5G needs network slicing?

So far, mobile networks (of up
to 4G), mainly serving mobile

5G Devices
5G Network

phones, have been optimized

for phones only, at large.
However, in 5G era, they have
to serve a variety of devices

Nokia, 2015

with different characteristics and needs. Some of the most mentioned use cases for 5G era are Mobile
Broadband, Massive IoT, and Mission-critical IoT, and they all require different types of features and
networks in terms of mobility, charging, security, policy control, latency, reliability, etc.
For instance, an massive IoT service that connects immobile sensors measuring temperature, humidity,
precipitation, etc. to mobile networks does not require features like handover or location update, which
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Netmanias Tech-Blog: E2E Network Slicing - Key 5G technology

have been critical in serving mobile phones. Or, a mission-critical IoT service (like autonomous driving or
remote controlled robots) requires, unlike mobile broadband service, a substantially low E2E latency less than a few ms.
Table 1. Most compelling use cases for 5G
5G Use Case

Example

Requirements

Mobile Broadband

4K/8K UHD, hologram, AR/VR

High capacity, video cache

Massive IoT

Sensor network (metering, agriculture,

Massive connection (200,000/km2)

building, logistics, city, home, etc.)

mostly immobile devices

Motion control, autonomous driving,

Low latency (ITS 5ms, motion

automated factory, smart-grid

control 1 ms)

Mission-critical IoT

high reliability
Then, does this mean we have to make dedicated networks for each service? So, one for 5G phone, one
for 5G massive IoT, another for 5G mission-critical IoT, and so on? No, we do not have to because
network slicing can give you multiple logical networks over a single physical network. A much more costeffective way!

4G Network: communication service

5G network: all mobile services via all types of devices

via phones in the communication

industry

across all industries

Service/Industry

Service/Device
Communication service
(voice, text and Internet)

Communication, Internet

Mobile Broadband
~ 20Gbps

4G network

Massive IoT

200,000/Km2

5G network

Logistics,
Agriculture,
Climate
Automobile
, Factory

Mission-critical IoT

1ms
how?
Multiple 5G networks ? X
Communication, Internet
Logistics,
Agriculture,
Climate
Automobile
, Factory

Network Slicing !
Communication, Internet

Mobile Broadband
Mobile Broadband Slice
Massive IoT

Mission-critical IoT

Massive IoT Slice

Mission-critical IoT Slice

5G network

Logistics,
Agriculture,
Climate
Automobile
, Factory

Figure 1. Network slicing: Why do we need it?

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Netmanias Tech-Blog: E2E Network Slicing - Key 5G technology

Below is an illustration of 5G network slices by presented in its 5G White Paper.

Figure 2. 5G network slices illustrated by NGMN

How do we implement E2E network slices?

The concept of network slices presented in Figure 2 above may look too abstract. Let's take a closer look
at how network slices are actually implemented.
(1) 5G RAN and Core: NFV
In the current mobile networks, main devices are phones, and RAN (DU and RU) and Core
functions are built with dedicated network equipment provided by RAN vendors. To implement
network slices, Network Function Virtualization (NFV) is a prerequisite. Basically, the main idea of NFV is
to install Network Function S/W (i.e., MME, S/P-GW and PCRF in Packet Core, and DU in RAN) all onto
Virtual Machines (VMs) deployed on a virtualized commercial server (COTS; commercial off-the-shelf),
NOT onto their dedicated network equipment individually. This way, RAN works as edge cloud while Core
works as core cloud. Connectivity among VMs located in edge and core clouds are provisioned using
SDN. Then, slices are created for each service (i.e., phone slice, massive IoT slice, mission-critical IoT
slice, and so on).

Netmanias Tech-Blog: E2E Network Slicing - Key 5G technology

Current Network (with dedicated equipment)

RU

RAN

Core

DU

Core
PCRF

Fronthaul
Dedicated
equipment

IP Backhaul

MME
S/P-GW

Dedicated
equipment

Dedicated
equipment

Edge Cloud

Core Cloud

(NFV)

(NFV)

VM/VNF=DU

VM/VNF = Core
Core

Creating virtualized network

NFV (Network functions like DU, Core, etc. are
virtualized and run on commercial servers)
SDN (Securing network connection)

DU
Hypervisor

Dedicated
equipment

Commercial
server

SDN
(network connection
between VMs)

Hypervisor

Commercial
server

Network Slicing: Creating multiple virtual networks (by cutting network horizontally)

UHD Slice

Edge Cloud

Core Cloud

(NFV)

(NFV)

DU

Core

Phone Slice

DU

Core

Massive IoT Slice

DU

Core

Mission-critical IoT Slice

DU

Core
Hypervisor

Hypervisor

SDN
Dedicated
equipment

Commercial
server

Commercial
server
In the figure, Core indicates user plane

Figure 3. How to slice network

Netmanias Tech-Blog: E2E Network Slicing - Key 5G technology

Figure 4 shows how applications dedicated for each service can be virtualized and installed in each slice.
For example, slices can be configured as follows:

UHD slice: All virtualized DU, 5G Core (UP), and Cache server in Edge cloud, and virtualized 5G
Core (CP) and MVO server in Core cloud

Phone slice: 5G Core (UP and CP) with full mobility features, and IMS server, all virtualized in Core
cloud

Massive IoT slice (e.g., sensor network): Simpler, light duty 5G Core WITHOUT mobility
management feature in Core cloud

Mission-critical IoT slice: 5G Core (UP) and associated servers (e.g., V2X server) all down in Edge
cloud for minimized transmission delay

As seen so far, dedicated slices are created for services with different requirements. And virtualized
network functions are being placed in different locations in each slice (i.e., Edge or Core cloud) depending
on services. Also, some network functions, like charging, policy control, etc., can be essential in one slice,
but unnecessary in other slices. Operators can customize network slices the way they want, probably in
the most cost-effective way.
Edge Cloud

Core Cloud

(NFV)

(NFV)

UHD Slice

MVO
DU

Core

Cache
TCP-Opt.

Phone Slice
DU

Massive IoT Slice

IMS

Core
IoT Svr

DU

Core

Access Mgt
Session Mgt

Mission-critical IoT Slice

DU

Core

V2X Svr

V2X Svr

Hypervisor

Hypervisor
Dedicated
equipment

Access Mgt
Session Mgt
Mobility Mgt
Charging

SDN

Figure 4. How to slice network (cont.)

Up to this point, it was NFV's job. Then, what role does SDN play in network slicing?
(2) Network slicing between Edge and Core clouds: IP/MPLS-SDN
SDN, although once a pretty simple concept when first introduced, has now become more complicated
than ever as every vendor claims their SDN authentic. Let's take Overlay type, an SDN approach that
offers connectivity between VMs by leveraging the existing network infrastructure, as an example.
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Netmanias Tech-Blog: E2E Network Slicing - Key 5G technology

SDN Controller
VM (VNF) Creation, Control
Connectivity among VMs

E2E Network Slices

Edge Cloud
(NFV)

DU
(UHD)

PGW
(UHD)

CDN
cache

Core Cloud
(NFV)

CDN
parent

UHD VPN

100Gbps, BE

DU
(Voice)

PGW
(Voice)

Voice VPN
DU
(IoT)

IMS
PGW
(IoT)

IoT VPN

IoT

vSwitch/vRouter
DC SD

SDN SW

nel
N Tun

SDN SW

IP/MPLS-SDN
(MPLS L3 VPN)

DC G/W
(PE)

5G Fronthaul

DC SD

vSwitch/

N Tun
nel vRouter

DC G/W
(PE)
T-SDN (POTN)

T-SDN

Figure 5. E2E network slicing

First let's see how network connectivity between VMs in Edge and Core clouds are secured. Inter-VM
networking must be made over both IP/MPLS SDN, and its sub SDN, Transport SDN. Here, however, we
will discuss router vendor-supplied IP/MPLS SDN only. Both Ericsson and Juniper have presented this type
of IP/MPLS SDN networking architecture, both operating slightly differently, but pretty similar in terms of
how VMs are connected through SDN.
In Core cloud lies a virtualized server. In the Hypervisor of the server, a built-in vRouter/vSwitch is run.
SDN Controller performs provisioning of the virtualized server and DC G/W routers (PE router of MPLS L3
VPN installed in cloud data center) to create SDN tunnels (i.e., MPLS GRE, VXLAN) between each VM in
the Core cloud (e.g., 5G IoT Core) and DC G/W router.
The SDN Controller then performs mapping between these tunnels and MPLS L3 VPN (e.g., IoT VPN). The
process is the same in Edge cloud as well, creating IoT slice connecting from Edge cloud, to IP/MPLS
backbone, and all the way to Core cloud. This process can be implemented using technologies and
standards that have become available so far.
(3) Network slicing between Edge cloud and RU at cell site
Now what's left is fronthaul. How do we slice this fronthaul between Edge cloud and 5G RU? To begin
with, 5G fronthaul would have to be defined first. There are some alternatives in discussion (e.g.,
introducing new packet-based fronthaul by redefining functions of DU and RU), but no standard
definition has been made yet. Figure 6 is an illustration presented in ITU Focus Group IMT 2020, and gives
an example of virtualized fronthaul.

Netmanias Tech-Blog: E2E Network Slicing - Key 5G technology

Figure 6. Example of 5G C-RAN network slicing by ITU

[Source: Report on Standards Gap Analysis, ITU, Focus groups on IMT-2020, Oct. 2015]

Network slicing for 5G era is still shaping up, with concerns and issues remaining unsolved. So, we will
keep track of technological updates by operators, vendors and standardization organizations in Korea
and around the world, to keep you updated about the technology.

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NMC Consulting Group is an advanced and professional network consulting company, specializing in IP network areas (e.g., FTTH, Metro Ethernet and IP/MPLS), service
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