E2E Network Slicing - Key 5G technology

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1 NETMANIAS TECH-BLOG Please visit to view more posts 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 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 5G Devices to 4G), mainly serving mobile phones, have been optimized for phones only, at large. However, in 5G era, they have to serve a variety of devices 5G Network 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 1

2 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, building, logistics, city, home, etc.) Massive connection (200,000/km 2 ) mostly immobile devices Mission-critical IoT Motion control, autonomous driving, automated factory, smart-grid Low latency (ITS 5ms, motion control 1 ms) 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 via phones in the communication industry Communication service (voice, text and Internet) 4G network 5G network: all mobile services via all types of devices across all industries Mobile Broadband ~ 20Gbps Massive IoT 200,000/Km 2 Service/Device 5G network Service/Industry Communication, Internet Logistics, Agriculture, Climate Mission-critical IoT 1ms Automobile, Factory how? Multiple 5G networks? X Network Slicing! Communication, Internet Logistics, Agriculture, Climate Mobile Broadband Massive IoT Mobile Broadband Slice Massive IoT Slice Mission-critical IoT Slice Communication, Internet Logistics, Agriculture, Climate Automobile, Factory Mission-critical IoT 5G network Automobile, Factory Figure 1. Network slicing: Why do we need it? 2

3 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 : NFV ❶ In the current mobile networks, main devices are phones, and RAN ( and RU) and functions are built with dedicated network provided by RAN vendors. ❷ To implement network slices, Network Function Virtualization 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, and in RAN) all onto Virtual Machines (VMs) deployed on a virtualized commercial server (COTS; commercial off-the-shelf), NOT onto their dedicated network individually. This way, RAN works as edge cloud while works as core cloud. Connectivity among VMs located in edge and core clouds are provisioned using SDN. ❸ Then, slices are created for each service (i.e., phone slice, massive IoT slice, mission-critical IoT slice, and so on). 3

4 ❶ Current Network (with dedicated ) RU RAN Fronthaul IP Backhaul PCRF MME S/P-GW ❷ Creating virtualized network NFV (Network functions like,, etc. are virtualized and run on commercial servers) SDN (Securing network connection) Edge Cloud Cloud VM/VNF= VM/VNF = Commercial server SDN (network connection between VMs) Commercial server ❸ Network Slicing: Creating multiple virtual networks (by cutting network horizontally) Edge Cloud Cloud UHD Slice Phone Slice Massive IoT Slice Mission-critical IoT Slice SDN Commercial server Commercial server In the figure, indicates user plane Figure 3. How to slice network 4

5 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, 5G (UP), and Cache server in Edge cloud, and virtualized 5G (CP) and MVO server in cloud Phone slice: 5G (UP and CP) with full mobility features, and IMS server, all virtualized in cloud Massive IoT slice (e.g., sensor network): Simpler, light duty 5G WITHOUT mobility management feature in cloud Mission-critical IoT slice: 5G (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 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 Cloud UHD Slice Cache MVO Phone Slice Massive IoT Slice TCP-Opt. IoT Svr IMS Access Mgt Session Mgt Mobility Mgt Charging Mission-critical IoT Slice Access Mgt Session Mgt V2X Svr V2X Svr 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 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. 5

6 SDN Controller Edge Cloud VM (VNF) Creation, Control Connectivity among VMs Cloud E2E Network Slices (UHD) vswitch/vrouter PGW (UHD) (Voice) CDN cache (IoT) DC SDN Tunnel UHD VPN 100Gbps, BE Voice VPN IoT VPN IP/MPLS-SDN (MPLS L3 VPN) PGW (Voice) IMS DC SDN Tunnel CDN parent PGW (IoT) IoT 서버 vswitch/ vrouter SDN SW 5G Fronthaul SDN SW DC G/W (PE) DC G/W (PE) T-SDN T-SDN (POTN) Figure 5. E2E network slicing First let's see how network connectivity between VMs in Edge and 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 cloud lies a virtualized server. In the 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 cloud (e.g., 5G IoT ) 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 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 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. 6

7 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. 7

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